JP2008254947A - Honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a honeycomb structure having excellent thermal shock resistance. <P>SOLUTION: The honeycomb structure 1 comprises: a honeycomb base material 2 composed of a porous ceramics and having a plurality of cells extending to the axial direction; and an outer circumferential material layer 4 composed of a ceramics covering the outer circumferential face in the circumferential direction of the honeycomb base material 2. Provided that the thermal expansion coefficient at 300 to 900°C in the honeycomb base material 2 is denoted as α<SB>I</SB>(ppm/K) and the thermal expansion coefficient at 300 to 900°C in the outer circumferential material layer 4 is denoted as α<SB>II</SB>(ppm/K), the value of α<SB>I</SB>-α<SB>II</SB>is 1.0 to 5.0(ppm/K). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a honeycomb structure, and more particularly to a honeycomb structure excellent in thermal shock resistance.

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

  A honeycomb structure made of a ceramic is generally made of a porous ceramic, and includes a honeycomb base material that defines a plurality of cells serving as fluid flow paths, and an outer periphery made of ceramics that covers the outer peripheral surface in the circumferential direction of the honeycomb base material. And a material layer. And the honeycomb base material is sealed with a sealing portion made of ceramics that seals the end portions where the adjacent cells are opposite to each other so that the end faces have a checkered pattern.

  A DPF made of a ceramic honeycomb structure is used as a wall flow type catalyst in which exhaust gas passes through partition walls that partition partition wall cells. The wall flow type catalyst collects PM in the exhaust gas through which the exhaust gas passes through the continuous pores formed in the cell wall and cannot pass through the pores. That is, the DPF is exposed to high-temperature exhaust gas in order to collect PM in the exhaust gas.

  Further, since the DPF is clogged when the collected PM is accumulated, it is necessary to remove the collected PM. One method of removing the collected PM is a method of decomposing and removing PM by combustion or the like. There is also a method in which a catalytic metal exhibiting catalytic activity is supported on the DPF and PM is decomposed with this catalytic metal.

  When PM is burned and removed, the honeycomb structure is heated, and combustion is further promoted by heat generated during decomposition (combustion) of PM. That is, the DPF is exposed to a rapid temperature change (temperature increase) during PM combustion.

  When the DPF exposed to high temperature is rapidly cooled, there is a problem in that the outer peripheral portion (outer peripheral material layer) is damaged. When the DPF held at a high temperature is rapidly cooled, the outer peripheral portion is rapidly cooled and contracts, but the inside (honeycomb substrate) remains at a high temperature and does not follow the contraction of the outer peripheral portion. As a result, tensile stress acts on the outer peripheral portion, and cracks and cracks occur on the outer peripheral portion.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the honeycomb structure excellent in thermal shock resistance.

  In order to solve the above-mentioned problems, the present inventors have repeatedly studied about a ceramic honeycomb structure, and as a result, the outer periphery of the honeycomb body (honeycomb base material, honeycomb segment) is 300 to 900 ° C. higher than the honeycomb body. It has been found that the above problem can be solved by arranging an outer peripheral layer having a low thermal expansion coefficient of 1.0 to 5.0 (ppm / K).

That is, the honeycomb structure of the present invention is made of porous ceramics and has a honeycomb substrate having a plurality of cells extending in the axial direction, and an outer peripheral material layer made of ceramics covering the outer peripheral surface of the honeycomb substrate in the circumferential direction. The thermal expansion coefficient of the honeycomb substrate at 300 to 900 ° C. is α _I (ppm / K), and the thermal expansion coefficient of the outer peripheral material layer at 300 to 900 ° C. is α _II (ppm / K), the value of α _I -α _II is 1.0 to 5.0 (ppm / K).

Further, the honeycomb structure of the present invention has a plurality of honeycomb bodies made of porous ceramics and a bonding material layer for bonding the plurality of honeycomb bodies to each other, and has a plurality of cells extending in the axial direction. A honeycomb structure having a substrate, the thermal expansion coefficient of the honeycomb body at 300 to 900 ° C. being α _III (ppm / K), and the thermal expansion coefficient of the bonding material layer at 300 to 900 ° C. being α _IV ( when the ppm / K), the value of alpha _{III-.alpha. IV} is characterized in that it is a 1.0~5.0 (ppm / K).

  The honeycomb structure of the present invention has a honeycomb substrate when exposed to a high temperature by making the thermal expansion coefficient of the outer peripheral material layer provided on the outer periphery of the honeycomb base material slightly smaller than the thermal expansion coefficient of the honeycomb base material. The amount of thermal expansion of the material is reduced. As a result, the honeycomb structure of the present invention became a honeycomb structure excellent in thermal shock resistance.

  Further, the honeycomb structure of the present invention reduces the thermal expansion amount of the honeycomb body when exposed to high temperatures by making the thermal expansion coefficient of the outer peripheral material layer slightly smaller than the thermal expansion coefficient of the honeycomb base material. I am letting. As a result, the honeycomb structure of the present invention became a honeycomb structure excellent in thermal shock resistance.

(First invention)
A honeycomb structure of the present invention comprises a honeycomb substrate having a plurality of cells extending in the axial direction and made of porous ceramics, and an outer peripheral material layer made of ceramics covering the outer circumferential surface of the honeycomb substrate in the circumferential direction. It is a honeycomb structure having.

The honeycomb structure of the present invention has a thermal expansion coefficient of α _I (ppm / K) of the honeycomb base material at 300 to 900 ° C., and a thermal expansion coefficient of the outer peripheral material layer at 300 to 900 ° C. of α _II (ppm / K), the value of α _I -α _II is 1.0 to 5.0 (ppm / K). The thermal expansion coefficient of the honeycomb substrate (alpha _I) and the thermal expansion coefficient of the outer peripheral material layer (alpha _II) is a thermal expansion coefficient of the ceramic constituting each.

  Ceramics have the property of being strong against compressive stress and weak against tensile stress. As in the present invention, the outer peripheral material layer is formed of a material having a smaller coefficient of thermal expansion than that of the honeycomb substrate, thereby regulating the amount of thermal expansion of the honeycomb substrate when the honeycomb structure is exposed to a high temperature. The shrinkage amount of the outer peripheral material layer can be reduced during shrinkage. As a result, the occurrence of cracks and cracks in the outer peripheral material layer due to thermal shock can be suppressed.

  More specifically, when the temperature of the honeycomb structure of the present invention is raised, each of the honeycomb base material and the outer peripheral material layer undergoes thermal expansion. The outer peripheral material layer is formed of a material having a smaller thermal expansion coefficient than the honeycomb base material, and the outer peripheral material layer regulates the thermal expansion of the honeycomb base material (the amount of thermal expansion of the honeycomb base material is reduced). When the heated honeycomb structure is cooled (rapidly cooled), the outer peripheral material layer exposed to a lower temperature is cooled and contracts. The honeycomb base material is maintained at a high temperature (a state in which thermal expansion occurs) due to the low thermal conductivity of the outer peripheral material layer. When the outer peripheral material layer shrinks, stress acts in the direction in which the honeycomb substrate shrinks (compresses). However, the honeycomb substrate is maintained in a state where thermal expansion has occurred, and tensile stress acts on the outer peripheral material layer. In the present invention, the thermal expansion of the honeycomb substrate is regulated, and the tensile stress applied to the outer peripheral material layer is reduced. As a result, the occurrence of cracks and cracks in the outer peripheral material layer is suppressed.

The honeycomb structure of the present invention exhibits an effect that the outer peripheral material layer regulates the thermal expansion of the honeycomb base material when the value of α _I -α _II is 1.0 to 5.0 (ppm / K). . Here, the values of α _I and α _II are values at the same temperature between 300 ° C. and 900 ° C. If the value of α _I -α _II is less than 1.0 (ppm / K), the difference in thermal expansion coefficient between the honeycomb base material and the peripheral material layer becomes too small, and the peripheral material layer regulates the thermal expansion of the honeycomb base material. The effect cannot be demonstrated. When the value of α _I -α _II exceeds 5.0 (ppm / K), the difference in thermal expansion coefficient between the honeycomb base material and the outer peripheral material layer becomes too large, and the outer peripheral material layer during thermal expansion when the temperature becomes high However, the thermal expansion of the honeycomb substrate is excessively restricted, and the honeycomb substrate and the outer peripheral material layer are damaged.

A preferable value of α _I -α _II is 1.0 to 4.0 (ppm / K), and a more preferable value of α _I -α _II is 1.0 to 3.0 (ppm / K). .

  In the present invention, when the temperature at which the honeycomb structure is exposed is in the temperature range of 300 to 900 ° C., the difference in thermal expansion coefficient is 1.0 to 5.0 (ppm / K). Below 300 ° C., the honeycomb structure hardly undergoes thermal expansion. For this reason, the effect which controls the thermal expansion of the honeycomb base material by an outer peripheral material layer cannot fully be exhibited. Further, since the thermal expansion hardly occurs, the difference in thermal expansion coefficient does not appear sufficiently. The temperature range in which the difference in thermal expansion coefficient falls within a predetermined range may be a high temperature range where the honeycomb structure is exposed, and is preferably 300 to 800 ° C.

  The porous ceramic material forming the honeycomb substrate of the honeycomb structure of the present invention is not particularly limited, and conventionally known ceramics 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 ceramics mainly composed of silicon carbide.

  In the honeycomb structure of the present invention, the outer peripheral material layer preferably has a thickness of 0.5 mm or more. When the thickness of the outer peripheral material layer is 0.5 mm or more, the effect of regulating the thermal expansion of the honeycomb substrate can be sufficiently exhibited. In addition, since the outer peripheral material layer regulates the thermal expansion of the honeycomb base material as the thickness of the outer peripheral material layer increases, the thermal shock resistance is improved. Generally, the outer peripheral material layer is formed by preparing a slurry that constitutes the outer peripheral material layer and applying this slurry to the outer peripheral surface of the honeycomb base material. Therefore, as the thickness of the outer peripheral material layer increases, the slurry is applied. Thickness increases, workability deteriorates and costs increase. For this reason, the preferable thickness of the outer peripheral material layer is 0.5 to 5.0 mm, the more preferable thickness is 0.5 to 3.0 mm, and the further preferable thickness is 0.5 to 1.0 mm. . The honeycomb structure of the present invention can suppress damage to the outer peripheral material layer even if the thickness of the outer peripheral material layer is reduced. Here, the thickness of the outer peripheral material layer is defined as the thickness of the outer peripheral material layer at the portion where the thickness in the radial direction of the honeycomb structure is the thinnest. 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.

  In the honeycomb structure of the present invention, the outer diameter of the honeycomb base material is not limited. However, if the outer peripheral material layer has a constant thickness, the smaller the outer diameter of the honeycomb base material, the better the thermal shock resistance. It becomes. In the honeycomb structure of the present invention, the thermal expansion coefficient of the outer peripheral material layer is slightly smaller than the thermal expansion coefficient of the honeycomb base material. The difference in thermal expansion coefficient regulates the thermal expansion of the honeycomb substrate. The amount of thermal expansion of the honeycomb substrate increases as the outer diameter of the honeycomb substrate increases. That is, the greater the outer diameter of the honeycomb substrate, the greater the stress applied to the outer peripheral material layer during thermal expansion. If the thickness of the outer peripheral material layer is the same, the stress that regulates the thermal expansion of the honeycomb substrate is relatively low, and the thermal expansion of the honeycomb substrate cannot be regulated. As a result, the honeycomb structure is damaged. On the other hand, when the outer diameter of the honeycomb substrate is reduced, the stress applied to the outer peripheral material layer during thermal expansion is reduced, and the honeycomb structure is not damaged. The amount of thermal expansion is also related to the heating temperature of the honeycomb structure, and the amount of thermal expansion increases as the heating temperature increases. That is, if the thickness of the outer peripheral material layer is the same, the smaller the outer diameter of the honeycomb base material, the more the honeycomb structure is not damaged even when exposed to a higher temperature.

(Second invention)
The honeycomb structure of the present invention has a plurality of honeycomb bodies made of porous ceramics and a bonding material layer for bonding the plurality of honeycomb bodies to each other, and has a plurality of cells extending in the axial direction. Is a honeycomb structure.

The honeycomb structure of the present invention has a thermal expansion coefficient of α _III (ppm / K) at 300 to 900 ° C. and an α _IV (ppm) thermal expansion coefficient of the bonding material layer at 300 to 900 ° C. / K), the value of α _III -α _IV is 1.0 to 5.0 (ppm / K). The thermal expansion coefficient of the honeycomb chromatid (alpha _III) and the thermal expansion coefficient of the bonding material layer (alpha _IV) is a thermal expansion coefficient of the ceramic constituting each. Here, the values of α _III and α _IV are values at the same temperature between 300 and 900 ° C. When the value of α _III -α _IV is 1.0 to 5.0 (ppm / K), the bonding material exerts an effect of regulating the thermal expansion of the honeycomb segment. If the value of α _III -α _IV is less than 1.0 (ppm / K), the difference between the thermal expansion coefficients of the honeycomb segment and the bonding material becomes too small, and the bonding material has the effect of regulating the thermal expansion of the honeycomb segment. Cannot be demonstrated. If the value of α _III -α _IV exceeds 5.0 (ppm / K), the difference between the thermal expansion coefficients of the honeycomb segment and the bonding material becomes too large, and when the thermal expansion occurs at a high temperature, Peeling occurs at the interface of the honeycomb body, and the honeycomb base material and the bonding material layer are damaged.

A preferable α _III -α _IV value is 1.0 to 4.0 (ppm / K), and a more preferable α _III -α _IV value is 1.0 to 3.0 (ppm / K). .

  In the present invention, when the temperature at which the honeycomb structure is exposed is in the temperature range of 300 to 900 ° C., the difference in thermal expansion coefficient is preferably 1.0 to 5.0 (ppm / K). Below 300 ° C., the honeycomb structure hardly undergoes thermal expansion. For this reason, the effect which controls the thermal expansion of the honeycomb base material by a joining material layer cannot fully be exhibited. Further, since the thermal expansion hardly occurs, the difference in thermal expansion coefficient does not appear sufficiently. The temperature range in which the difference in thermal expansion coefficient falls within a predetermined range may be a high temperature range where the honeycomb structure is exposed, and is preferably 300 to 800 ° C.

  The material of the porous ceramic forming the honeycomb segment of the honeycomb structure of the present invention is not particularly limited, and conventionally known ceramics 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 ceramics mainly composed of silicon carbide.

  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 joined with the joining material is preferably formed with a thickness of 0.5 to 5.0 mm.

  Here, when the honeycomb structure of the present invention is formed by joining a plurality of segments, if the thickness of the bonding material layer in the thickness direction of the partition walls of the honeycomb structure is very small, the bonding material layer You can ignore the effects of.

  In the honeycomb structure of the present invention, the outer diameter of the honeycomb body is not limited, but if the thickness of the bonding material layer is constant, the smaller the outer diameter of the honeycomb body, the better the thermal shock resistance. It becomes. In the honeycomb structure of the present invention, the thermal expansion coefficient of the bonding material layer is slightly smaller than the thermal expansion coefficient of the honeycomb divided material. The difference in thermal expansion coefficient regulates the thermal expansion of the honeycomb segment. The amount of thermal expansion of the honeycomb body increases as the outer diameter of the honeycomb body increases. That is, the larger the outer diameter of the honeycomb segment, the greater the stress applied to the bonding material layer during thermal expansion. If the thickness of the bonding material layer is the same, the stress that regulates the thermal expansion of the honeycomb segment is relatively low, and the thermal expansion of the honeycomb segment cannot be regulated. As a result, the honeycomb structure is damaged. On the other hand, when the outer diameter of the honeycomb segment is reduced, the stress applied to the bonding material layer during thermal expansion is reduced, and the honeycomb structure is not damaged. The amount of thermal expansion is also related to the heating temperature of the honeycomb structure, and the amount of thermal expansion increases as the heating temperature increases. That is, as long as the thickness of the bonding material layer is the same, the smaller the outer diameter of the honeycomb segment, the less the honeycomb structure is damaged even when exposed to a higher temperature.

  The 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 honeycomb structure is used for a DPF or the like can be suppressed. Specifically, when the honeycomb structure is used for applications such as DPF, the honeycomb structure is exposed to high heat. The 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.

  In addition, since the thickness of the outer peripheral material layer varies depending on the shape of the honeycomb structure, the thickness thereof cannot be determined unconditionally. Note that as the thickness of the outer peripheral material layer increases, the amount of deformation due to thermal expansion of the honeycomb body that can be relaxed by the outer peripheral material layer increases, thereby improving the thermal shock resistance of the honeycomb structure. Generally, the outer peripheral material layer is formed by preparing a slurry that constitutes the outer peripheral material layer and applying this slurry to the outer peripheral surface of the honeycomb base material. Therefore, as the thickness of the outer peripheral material layer increases, the slurry is applied. Thickness increases, workability deteriorates and costs increase. For this reason, the preferable thickness of the outer peripheral material layer is 0.5 to 5.0 mm, the more preferable thickness is 0.5 to 3.0 mm, and the further preferable thickness is 0.5 to 1.0 mm. .

In the honeycomb structure of the present invention, when the thermal expansion coefficient of the outer peripheral material layer at 300 to 900 ° C. is α _II (ppm / K), the value of α _III -α _II is 1.0 to 5.0 ( ppm / K). When the value of α _III -α _II falls within a predetermined range, the outer peripheral material layer can regulate the amount of thermal expansion of the honeycomb substrate, and the amount of contraction of the outer peripheral material layer can be reduced during contraction. As a result, the occurrence of cracks and cracks in the outer peripheral material layer due to thermal shock can be suppressed.

  In the first to second honeycomb structures of the present invention, the cell shape (cross-sectional shape) is not particularly limited, and may be a conventionally known cross-sectional shape. Of the conventionally known cell shapes, a square shape is more preferable. Furthermore, when the honeycomb structure is formed by bonding a plurality of ceramic segments through the bonding material layer, the size of the cells (cell shape) formed in each ceramic segment is the same, It may be different or any. The size (cell shape) of each ceramic segment cell is preferably the same.

  In the first to second honeycomb structures of the present invention, one end or the other end of many cells is preferably sealed with a sealing material made of ceramics. A wall flow type honeycomb structure can be formed by sealing one end or the other end of the cell with a sealing material. The material of the ceramic constituting the sealing material is not particularly limited, and may be the same as or different from the porous ceramic constituting the honeycomb structure. More preferably, the ceramic is mainly composed of porous ceramics.

  The first to second honeycomb structures of the present invention are preferably used for DPF. The honeycomb structure of the present invention can be used as a wall flow type filter catalyst in which exhaust gas (gas) passes through partition walls that partition cells, and among these filter catalysts, it is particularly preferable to use as a DPF.

  When the first to second honeycomb structures of the present invention are used as a DPF, at least one of a porous oxide made of alumina or the like, or a catalyst metal such as Pt, Pd, or Rh is formed on at least the pore surfaces of the partition walls. It is preferably supported. By carrying these substances, purification performance such as particulates as DPF is improved.

  The outer peripheral shape of the first to second honeycomb structures 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.

  Hereinafter, the present invention will be described using examples.

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

Example 1
The manufacturing method of the honeycomb structure for DPF of an Example is shown below.

  First, a ceramic body of the honeycomb body 2 containing SiC as a main component is weighed, and after thoroughly mixing (kneading) the raw material, a molded body made of columnar SiC having a large number of cells formed in the axial direction is conventionally obtained. It was manufactured by extrusion molding, which is a known manufacturing method. This molded body has cells having a square section. Here, the outer peripheral shape (apparent shape) of the formed body can be formed not only in the shape of a prism as in the present embodiment, but also in the outer peripheral shape that substantially matches the outer peripheral shape when the honeycomb structure is 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 dried molded object, and was dried 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 in which the slurry is injected into the cell at 2300 ° C. is heat-treated to fire the molded body, and the slurry is solidified to form the sealing material 3, and the cell sealed with the sealing material 3 (sealing part) A honeycomb body 2 having the structure was formed. The length of the sealing material 3 in the axial direction of the cell was 3.0 mm. The state in which the sealing part is formed is schematically shown in FIG.

  The honeycomb body 2 was cut using an electric saw to form an outer peripheral shape. The cutting with the electric saw was made to form a substantially cylindrical shape of φ60 mm in which the cells having the sealing material formed at both ends formed the outer peripheral surface along the line indicated by the broken line in FIG. FIG. 2 schematically shows the honeycomb body 2 (cut body) after being formed.

  And 75.50 g of SiC powder having an average particle diameter (D50) of 30 μm (manufactured by Shinano Denki Smelting Co., Ltd., trade name: GP- # 400) and spherical silica having an average particle diameter (D50) of 7 μm (commercially available from Denki Kagaku Kogyo Co. Name: FB-8S) 60.40 g, average particle diameter (D50) spherical silica (1.2 μm) (Shin-Etsu quartz, product name: SO-C5) 18.12 g, 1.26 wt% carboxymethyl cellulose (CMC) Containing binder solution (Daicel Chemical Industries, trade name: CMC Daicel) 18.12 g, colloidal silica (Nissan Chemical Industries, trade name: Snowtex 30) 18.12 g, Dispersant (Uniqema, trade name: KD-2) ) 0.50 g was weighed and mixed well to prepare a slurry. The prepared slurry was a slurry having fine particles and was in a mousse-like state. For this reason, it was easy to handle.

  And the prepared slurry was apply | coated so that the thickness of the thinnest part might be set to 1.0 mm on the outer peripheral surface of a cutting body, and it dried at 80 degreeC, Then, it heated at 850 degreeC and solidified the slurry. Thereby, the outer peripheral material layer 4 was able to be formed on the outer peripheral surface. Moreover, the prepared slurry could be easily applied.

  As described above, the honeycomb structure 1 of this example could be manufactured. The honeycomb structure of the present example is shown in FIGS. 3 shows the end face of the honeycomb structure 1, FIG. 4 shows the vicinity of the peripheral edge of the end face of the honeycomb structure 1, and FIG. 5 shows the cross section of the honeycomb structure 1 in the axial direction.

  As shown in the figure, a honeycomb structure 1 of the present example includes a honeycomb substrate 2 made of porous SiC ceramics having a large number of cells extending in the axial direction, and one of predetermined cells among the large number of cells. The sealing material 3 filled in one end portion or the other end portion and the outer peripheral material layer 4 formed on the outer peripheral surface in the circumferential direction of the partition wall portion are provided. Note that the honeycomb body 2 of the honeycomb structure 1 of the present example is formed in a substantially cylindrical shape having an outer diameter of 61.0 mm and an axial length of 150 mm.

(Comparative Example 1)
A honeycomb structure was manufactured in the same manner as in Example 1, except that the slurry for forming the outer peripheral material layer 4 was a slurry containing SiC as a main component (trade name: BETACK 1566, manufactured by Telnic Industry Co., Ltd.).

(Comparative Example 2)
The slurry for forming the outer peripheral material layer 4 is 75.50 g of SiC powder (the above-mentioned trade name: GP- # 400) having an average particle diameter (D50) of 20 μm and spherical silica having an average particle diameter (D50) of 7 μm ( The above-mentioned product name: FB-8S) 60.40 g, the average particle size (D50) is 1.2 μm spherical silica (the above-mentioned product name: SO-C5) 18.12 g, the average particle size (D50) phenol is 30 μm Resin (manufactured by Gunei Chemical Industry Co., Ltd., trade name: Marilyn MC-043) 9.54 g, binder solution containing CMC at 1.26 wt% (above trade name: CMC Daicel) 18.12 g, colloidal silica (above trade name : Snowtex N) 18.12 g, 0.50 g of a dispersion material (manufactured by San Nopco, trade name: SN Dispersant 5468), and a slurry prepared by mixing with 10.00 g of water Other than the can, to manufacture a honeycomb structure in the same manner as in Example 1.

  In the honeycomb structure of this comparative example, powdering was confirmed on the surface of the outer peripheral material layer 4.

(Evaluation)
As an evaluation of the honeycomb structures 1 of Example 1 and Comparative Examples 1 and 2, each honeycomb structure was subjected to a heat shock test. Specific test methods are shown below.

  First, a heating furnace capable of adjusting the internal temperature is prepared, and the furnace temperature is heated to a predetermined temperature within the range of 600 to 950 ° C. (temperature every 50 ° C.) and held. When it is confirmed that the furnace temperature is maintained at a predetermined temperature, the honeycomb structure to be tested is placed in the furnace and held for 20 minutes.

  After holding for 20 minutes, the honeycomb structure was taken out from the furnace, held at room temperature, and rapidly cooled.

  At the time of heat dissipation (rapid cooling), the outer periphery was observed until the temperature of the honeycomb structure was sufficiently lowered. The observation results are shown in Table 1. In Table 1, when the crack was not confirmed in the outer peripheral material layer 4, it was indicated by ◯, and when the crack was confirmed in the outer peripheral material layer 4, it was indicated by ×.

  Further, the thermal expansion coefficients of the honeycomb substrate 2 and the outer peripheral material layer were measured at the respective heating temperatures of the honeycomb structure 1, and the measurement results are shown in FIG. In FIG. 6, the thermal expansion coefficient of the honeycomb base material 2 and the thermal expansion coefficients of the respective outer peripheral material layers of the example and the comparative example are shown.

  As shown in Table 1, the honeycomb structure of each comparative example had cracks in the outer peripheral material layer when heated to 800 ° C. As shown in FIG. 6, the honeycomb structure of each comparative example has a thermal expansion coefficient of the outer peripheral material layer equal to or higher than that of the honeycomb base material. For this reason, when the honeycomb structure is heated to cause thermal expansion of the honeycomb base material and the outer peripheral material layer, the honeycomb structure expands with a large thermal expansion amount. And when shrinking at the time of cooling, the amount of shrinkage becomes large, and the tensile stress concerning an outer peripheral material layer becomes large. As a result, cracks occur in the outer peripheral material layer.

On the other hand, the honeycomb structure of Example 1 was not cracked in the outer peripheral material layer even when heated to 800 ° C. The honeycomb structure of Example 1, as shown in FIG. 6, the difference in the thermal expansion coefficient of the honeycomb substrate 2 at 300~900 ℃ (α _I) between the thermal expansion coefficient of the outer peripheral material layer 4 (alpha _II) Value (value of α _I -α _II ) is in the range of about 1.0 to 2.5 (ppm / K), and therefore, the thermal expansion of the honeycomb base material 2 is regulated by the outer peripheral material layer 4. The amount of contraction of the outer peripheral material layer 4 at the time of contraction was reduced, the tensile stress applied to the outer peripheral material layer 4 was reduced, and the outer peripheral material layer 4 was not cracked.

  As described above, the honeycomb structure of Example 1 is a honeycomb structure having better thermal shock resistance than the honeycomb structure of the comparative example. That is, it can be seen that by adjusting the thermal expansion coefficients of the honeycomb substrate 2 and the outer peripheral material layer 4 constituting the honeycomb structure 1, a honeycomb structure having excellent thermal shock resistance can be obtained.

  In this embodiment, the thickness of the outer peripheral material layer 4 is 1.0 mm. However, if the thickness of the outer peripheral material layer 4 is greater than 1.0 mm, the outer peripheral material layer 4 is heated to 800 ° C. or higher. Cracks are less likely to occur.

(Example 2)
A honeycomb structure was manufactured in the same manner as in Example 1 except that the honeycomb body 2 was substantially cylindrical with a diameter of 40 mm.

(Example 3)
A honeycomb structure was manufactured in the same manner as in Example 1 except that the thickness of the outer peripheral material layer 4 was changed to 5 mm.

(Evaluation)
A heat shock test similar to that in Example 1 was performed on the honeycomb structures of Examples 2 to 3. The test results are also shown in Table 1.

  As shown in Table 1, the honeycomb structure of Example 2 was not cracked in the outer peripheral material layer even when heated to 850 ° C. Since the honeycomb structure of Example 2 has a small outer diameter, the amount of thermal expansion of the honeycomb body when heated is small. While the amount of thermal expansion of the honeycomb body is small, the outer peripheral material layer can regulate the thermal expansion of the honeycomb body. When the heating temperature becomes excessively large (above 850 ° C.), the amount of thermal expansion of the honeycomb body becomes excessively large, and the outer peripheral material layer cannot regulate the thermal expansion of the honeycomb body. That is, it can be seen that the thermal shock resistance increases as the outer diameter of the honeycomb body decreases as in the honeycomb structure of the present example.

  The honeycomb structure of Example 3 was not cracked in the outer peripheral material layer even when heated to 950 ° C. The honeycomb structure of Example 3 has a considerably thick outer peripheral material layer of 5 mm, and has a high ability to the stress received from the thermal expansion of the honeycomb body. That is, by forming the outer peripheral material layer sufficiently thick, the thermal expansion can be regulated even if the thermal expansion amount of the honeycomb body becomes considerably large. The honeycomb structure of the present example suppresses the thermal expansion of the honeycomb even at a high temperature (a temperature range higher than a temperature range exposed when the honeycomb body is used for a DPF or the like) at which the amount of thermal expansion of the honeycomb body becomes considerably large. It was found that the thermal shock resistance was excellent.

Example 4
A method for manufacturing the DPF honeycomb structure of Example 4 will be described below.

  First, the honeycomb segment 5 was manufactured by the same method as that for manufacturing the honeycomb body of Example 1. The honeycomb segment 5 is the honeycomb of Example 1 except that the bonding material layer 6 has a smaller cross-sectional area in the cross section perpendicular to the axial direction than the honeycomb body of Example 1 (the number of partitioned cells is small). The configuration is the same as that of the body 2. In the manufactured honeycomb body 5, a sealing portion made of the sealing material 3 is formed in a cell. The honeycomb segment 5 is shown in FIG. In FIG. 7, the sealing material 3 is omitted.

  And the slurry similar to the slurry prepared in order to form an outer periphery material layer in Example 1 was prepared. Using the prepared slurry as a bonding material, the honeycomb bodies 5 were bonded to each other. In the bonding with the bonding material, the bonding material was applied to the outer peripheral surface of the honeycomb body 5 so as to have a thickness of 1.0 ± 0.5 mm, and then another honeycomb body 5 was bonded to the surface. . This joining was repeated, and the 16 honeycomb bodies 5 were joined so that the cross section was a square, and dried at 80 ° C. The end face of the joined body of the honeycomb body 5 is shown in FIG.

  Then, this joined body was cut using an electric saw to form an outer peripheral shape. Cutting with an electric saw was made so that a cell having a sealing material formed at both ends formed a substantially cylindrical shape forming an outer peripheral surface. During this cutting, no peeling of the sealing material from the cell was observed.

  Then, a slurry similar to that in Example 1 was prepared, applied to the outer peripheral surface of the molded body with a thickness of 0.5 mm, dried at 80 ° C., and then heated at 850 ° C. to solidify the bonding material and the slurry. It was. Thereby, the outer peripheral material layer 4 was able to be formed on the outer peripheral surface.

  As described above, the honeycomb structure 1 of this example could be manufactured. The honeycomb structure of the present example is shown in FIG. The handling of the slurry prepared in the manufacture of the honeycomb structure of the present example can be easily performed as described above, and the manufacture of the honeycomb structure of the present example can be easily performed.

  As shown in the figure, the honeycomb structure 1 of the present example is composed of a honeycomb structure in which a plurality of honeycomb bodies 5 made of porous SiC ceramics are bonded via a bonding material layer 6, and a large number of cells. And a sealing material 3 filled in one end or the other end of a predetermined cell, and an outer peripheral material layer 4 formed on the outer peripheral surface in the circumferential direction of the partition wall. is doing.

(Comparative Example 3)
A honeycomb structure was prepared in the same manner as in Example 2 except that the slurry for forming the outer peripheral material layer 4 and the bonding material layer 6 was the same as the slurry for forming the outer peripheral material layer 4 of Comparative Example 1. Manufactured.

(Comparative Example 4)
The honeycomb structure was formed in the same manner as in Example 2 except that the slurry for forming the outer peripheral material layer 4 and the bonding material layer 6 was the same as the slurry for forming the outer peripheral material layer 4 of Comparative Example 2. Manufactured.

(Evaluation)
As an evaluation of the honeycomb structures 1 of Example 4 and Comparative Examples 3 to 4, the same heat shock test as that of Example 1 was performed. The heat shock test was performed by heating to a predetermined temperature within a range of 600 to 850 ° C. The test results are shown in Table 2.

  As shown in Table 2, the honeycomb structures of Comparative Examples 3 to 4 were cracked in the outer peripheral material layer when heated to 750 ° C. In each of the honeycomb structures of the comparative examples, the thermal expansion coefficient of the outer peripheral material layer is equal to or greater than the thermal expansion coefficient of the honeycomb segment. Since the materials constituting the honeycomb segment 5 and the bonding material layer 6 used in Example 4 and Comparative Examples 3 to 4 are the same as those in Example 1 and Comparative Examples 1 and 2, each is shown in FIG. It is clear that it has a thermal expansion coefficient.

  The honeycomb structures of Comparative Examples 3 to 4 expand with a large amount of thermal expansion when the honeycomb structure 1 is heated and the honeycomb segment 5 and the bonding material layer 6 cause thermal expansion. And when shrinking at the time of cooling, the amount of shrinkage becomes large, and the tensile stress concerning an outer peripheral material layer becomes large. As a result, cracks occur in the outer peripheral material layer.

On the other hand, the honeycomb structure of Example 4 was not cracked in the outer peripheral material layer even when heated to 750 ° C. The honeycomb structure of Example 2, as shown in FIG. 6, the difference in the thermal expansion coefficient of the honeycomb chromatid 5 at 300~900 ℃ (α _III) and the thermal expansion coefficient of the bonding material layer 6 (alpha _IV) for the value (the value of α _III -α _IV) is in the range of approximately 1.0 to 2.5 (ppm / K), the thermal expansion of the honeycomb chromatid 5 are restricted by the bonding material layer 6, The amount of thermal expansion of the entire honeycomb structure 1 is small. That is, the amount of thermal expansion of the outer peripheral material layer 4 during thermal expansion is suppressed, the amount of contraction of the outer peripheral material layer 4 during contraction is reduced, the tensile stress applied to the outer peripheral material layer 4 is reduced, and the outer peripheral material layer 4 No more cracks.

  As described above, the honeycomb structure of Example 4 is a honeycomb structure having better thermal shock resistance than the honeycomb structures of Comparative Examples 3 to 4. That is, it can be seen that the honeycomb structure having excellent thermal shock resistance can be obtained by adjusting the thermal expansion coefficients of the honeycomb segment 5 and the bonding material layer 6 constituting the honeycomb structure 1.

  In this embodiment, the thickness of the bonding material layer 6 is 1.0 mm. However, if the thickness of the bonding material layer 6 is greater than 1.0 mm, the outer peripheral material layer is heated even when heated to 700 ° C. or higher. Cracks are less likely to occur.

1 is a view showing a honeycomb body used for a honeycomb structure of Example 1. FIG. 1 is a view showing a cut body of a honeycomb body of Example 1. FIG. 3 is a view showing an end face of a honeycomb structure of Example 1. FIG. 3 is a view showing the vicinity of the peripheral edge portion of the end face of the honeycomb structure of Example 1. FIG. 3 is a view showing a cross section in the axial direction of a honeycomb structure of Example 1. FIG. It is the figure which showed the difference ((alpha) _I- (alpha) _II ) of the thermal expansion coefficient of the honeycomb structure of Example 1 and Comparative Examples 1-2. FIG. 6 is a view showing a honeycomb segment used in the honeycomb structure of Example 4. 6 is a view showing an end face of a joined body of honeycomb bodies of Example 4. FIG. 6 is a view showing an end face of a honeycomb structure of Example 4. FIG.

Explanation of symbols

1: Honeycomb structure 2: Honeycomb body 3: Sealing material 4: Peripheral material layer 5: Honeycomb segment 6: Bonding material layer

Claims (4)

A honeycomb substrate made of porous ceramics and having a plurality of cells extending in the axial direction;
An outer peripheral material layer made of ceramics covering the outer peripheral surface of the honeycomb substrate in the circumferential direction;
A honeycomb structure having
When the thermal expansion coefficient of the honeycomb substrate at 300 to 900 ° C. is α _I (ppm / K) and the thermal expansion coefficient of the outer peripheral material layer at 300 to 900 ° C. is α _II (ppm / K), A honeycomb structure having a value of α _I -α _II of 1.0 to 5.0 (ppm / K).   The honeycomb structure according to claim 1, wherein the porous ceramic is mainly composed of silicon carbide. A plurality of honeycomb bodies made of porous ceramics;
A bonding material layer for bonding the honeycomb bodies to each other;
A honeycomb structure having a honeycomb substrate having a plurality of cells extending in the axial direction,
When the thermal expansion coefficient of the honeycomb segment at 300 to 900 ° C. is α _III (ppm / K) and the thermal expansion coefficient of the bonding material layer at 300 to 900 ° C. is α _IV (ppm / K), A honeycomb structure having a value of α _III -α _IV of 1.0 to 5.0 (ppm / K).   The honeycomb structure according to claim 3, wherein the porous ceramic is mainly composed of silicon carbide.

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