JP4873326B2 - Honeycomb structure - Google Patents

Description

The present invention relates to a honeycomb structure.

Conventionally, as an exhaust gas purification filter or a catalyst carrier, an aggregated honeycomb structure formed by combining a plurality of columnar honeycomb fired bodies in which a large number of cells are arranged in the longitudinal direction is known (for example, see Patent Document 1). ). In such a collective honeycomb structure, an adhesive layer is formed on the side surface of each honeycomb fired body, and the honeycomb fired bodies are bonded to each other through the adhesive layer.
In such a honeycomb structure, the honeycomb fired bodies are firmly bonded to each other in order to prevent the shape of the honeycomb structure in which the honeycomb fired bodies are bundled from collapsing.

However, in the aggregated honeycomb structure in which the honeycomb fired bodies are firmly bonded to each other in this way, it is used as an exhaust gas purification filter, and thermal stress is applied to the central portion of the honeycomb structure when regenerated. Cracks may occur, which is a problem.
JP 2005-154202 A

The present invention has been made to solve these problems, and provides a honeycomb structure in which cracks and the like are not generated even when a regeneration process is performed and thermal stress is applied. With the goal.

In other words, the honeycomb structure according to claim 1 is a honeycomb structure in which a plurality of columnar honeycomb fired bodies in which a large number of cells are arranged in parallel in the longitudinal direction with a cell wall interposed therebetween are bound via an adhesive layer. Body,
Among the honeycomb fired bodies, the adhesive strength A measured by a three-point bending strength test between the central honeycomb fired bodies located at the center of the cut surface obtained by cutting the honeycomb structure along a cross section perpendicular to the longitudinal direction is: 0.02 to 0.2 MPa, and
The adhesive strength A is characterized by being lower than the adhesive strength B measured by a three-point bending strength test between outer peripheral honeycomb fired bodies constituting a part of the outer periphery of the honeycomb structure of the honeycomb fired bodies. To do.

In the honeycomb structure according to the first aspect, the adhesive strength A between the central honeycomb fired bodies is set lower than the adhesive strength B between the peripheral honeycomb fired bodies.
At the time of regenerating the honeycomb structure, the central portion of the honeycomb structure is likely to be heated at a higher temperature than the outer peripheral portion, and therefore, it is considered that the honeycomb structure is subjected to a larger thermal stress than the outer peripheral portion. In the honeycomb structure, since the bonding strength A between the honeycomb fired bodies at the center is lowered, the thermal stress received by the fired bodies at the center can be reduced by the adhesive layer, and there is a crack at the center of the honeycomb structure. It can be prevented from occurring.
Further, in the honeycomb structure of the present invention, the bonding strength B between the peripheral honeycomb fired bodies is increased, and the peripheral honeycomb fired bodies are bonded with sufficient adhesive strength to maintain the shape of the honeycomb structure. Therefore, the shape of the honeycomb structure does not collapse, or the position of the honeycomb fired body does not shift.

Further, since the adhesive strength A between the central honeycomb fired bodies is 0.02 MPa or more, the central honeycomb fired body is difficult to come off from the honeycomb structure, and the adhesive strength A is 0.2 MPa or less. The thermal stress received by the center honeycomb fired body is easily dispersed, and cracks are less likely to occur.

That is, in the honeycomb structure of the present invention, the adhesive strength between all the honeycomb fired bodies is not uniformly increased as in the conventional honeycomb structure, but the adhesive strength between the honeycomb fired bodies in the central portion is in a specific range. Further, the honeycomb structure is provided with a difference in adhesive strength between the honeycomb fired bodies at the outer peripheral portion, and thereby formed with sufficient adhesive strength to maintain the shape thereof, and cracks are not generated during the regeneration process. It can be a body.

In the honeycomb structure according to claim 2, the adhesive strength A measured by a three-point bending strength test between the central honeycomb fired bodies and a three-point bending strength test between the outer peripheral honeycomb fired bodies were measured. The difference (B−A) from the adhesive strength B is 0.02 to 0.2 MPa.

In the honeycomb structure according to claim 2, by setting the difference in adhesive strength (B-A) in such a range, thermal stress is dispersed in the adhesive layer between the central portion and the periphery thereof, so that the regeneration treatment is performed. Sometimes cracks are less likely to occur.
If the difference in the adhesive strength (BA) is less than 0.02 MPa, the difference is small, so that cracks and the like are likely to occur. On the other hand, the difference in adhesive strength (BA) exceeds 0.2 MPa. Then, the adhesive strength of the outer peripheral portion becomes too strong, stress concentration occurs in the outer peripheral portion, and cracks are likely to occur.

In the honeycomb structure according to a third aspect, any one end of the cell is sealed, and can function as an exhaust gas purification filter that removes particulates and the like in the exhaust gas of the vehicle.

In the honeycomb structure according to claim 4, since the main components of the adhesive layer are inorganic fibers and an inorganic binder, inorganic particles and an inorganic binder, or inorganic fibers, an inorganic particle, and an inorganic binder, an adhesive layer is formed. When this occurs, it is easy to relieve stress and cracks are less likely to occur.

(First embodiment)
Hereinafter, a first embodiment which is an embodiment of the present invention will be described with reference to the drawings.
FIG. 1A is a longitudinal sectional view showing an embodiment of a honeycomb structure of the present invention, FIG. 1B is a perspective view of the honeycomb structure, and FIG. It is a perspective view which shows the honeycomb fired body 13 which comprises the honeycomb structure as described in (a) and (b), (b) is the AA sectional view.

In the honeycomb structure 10 according to the embodiment, a plurality of honeycomb fired bodies 11, 12, and 13 including the honeycomb fired body 13 shown in FIG. 2A are bundled through an adhesive layer 14 to form a ceramic block 15. Further, a sealing material layer 16 is formed on the outer periphery of the ceramic block 15.
In FIGS. 1 (a) and 1 (b), only the outlines of the honeycomb fired bodies 11, 12, and 13 are shown, but the honeycomb fired bodies 13 and the like constituting the honeycomb structure 10 are shown in FIG. 2 (b). As described above, a large number of cells 13a are arranged in the longitudinal direction, and the cell wall 13b separating the cells 13a functions as a filter.

As shown in FIG. 2 (b), the cells 13a formed in the honeycomb fired body 13 are sealed by either one of the end portions on the inlet side or the outlet side of the exhaust gas with the sealing material 13c. The exhaust gas flowing into the cell 13a passes through the cell wall 13b separating the cell 13a and then flows out from the other cell 13a. When the exhaust gas passes through the cell wall 13b, the particulates are part of the cell wall 13b. In this way, the exhaust gas is purified. The honeycomb fired body 13 has a quadrangular prism shape as shown in FIG. 2A, but the honeycomb fired bodies 11 and 12 are produced by cutting the honeycomb fired body 13. .

In the honeycomb structure of the present invention, the center portion refers to a portion in the vicinity of the center on a cut surface obtained by cutting the honeycomb structure perpendicular to the longitudinal direction.
Therefore, in the honeycomb structure 10 formed by binding a total of 16 honeycomb fired bodies 11, 12, 13 in 4 × 4 in width, the central honeycomb fired body is as shown in FIG. 1 (a). The four honeycomb fired bodies 13 present at the upper right, lower right, upper left and lower left of the center of the cut surface cut in a cross section perpendicular to the longitudinal direction.

Further, the outer peripheral honeycomb fired body constituting a part of the outer periphery in FIG. 1A refers to twelve honeycomb fired bodies 11 and 12 in contact with the sealing material layer 16 formed on the outer peripheral part. .

Therefore, the adhesive strength A between the honeycomb fired bodies at the center means the adhesive strength between the honeycomb fired bodies 13 bonded by the adhesive layer 14a, and the adhesive strength B between the fired bodies at the outer peripheral part is the adhesive. This refers to the bonding strength of the honeycomb fired bodies 11 and 12 or the honeycomb fired bodies 12 and 12 bonded by the layer 14b.

FIG. 3 is a longitudinal sectional view of a honeycomb structure 20 in which 25 honeycomb fired bodies 21, 22, 23, and 27 are bundled in 5 vertical × 5 horizontal.
The center-portion honeycomb fired body in such a honeycomb structure 20 includes a honeycomb fired body located at the center of the cut surface, and eight honeycombs existing in the upper, lower, left, right, upper right, lower right, upper left and lower left of the honeycomb fired body. The fired body, that is, a total of nine honeycomb fired bodies 23 is referred to. In FIG. 3, reference numeral 25 denotes a ceramic block.

Moreover, the outer peripheral part honeycomb fired body which comprises a part of outer periphery means the 16 honeycomb fired bodies 21, 22, and 27 which are in contact with the sealing material layer 26 formed in the outer peripheral part in FIG.

Therefore, the adhesive strength A between the honeycomb fired bodies at the center means the adhesive strength between the honeycomb fired bodies 23 bonded by the adhesive layer 24a, and the adhesive strength B between the honeycomb fired bodies at the outer periphery is the adhesive. The bonding strength of the honeycomb fired bodies 21 and 22 or the honeycomb fired bodies 22 and 27 bonded by the layer 24b is referred to.

Based on the above, when the number of bundles of the honeycomb fired bodies is an even number × even number, even if the number exceeds 16, the number of bundles is 4 × 4 horizontal As in the case of the structure, four honeycomb fired bodies become the central honeycomb fired body, and the number of bundles of the honeycomb fired bodies is an odd number × odd number is a case where the number exceeds 25. However, nine honeycomb fired bodies become the central honeycomb fired body as in the case of the honeycomb structure having a bundle number of 5 × 5.

And, as described above, the adhesive strength A between the honeycomb fired bodies at the center is determined by a three-point bending test on any two adjacent honeycomb fired bodies among the four or nine honeycomb fired bodies. Refers to the measured adhesive strength. In the present invention, the adhesive strength A is 0.02 to 0.2 MPa, and is lower than the adhesive strength B between the outer peripheral honeycomb fired bodies. Further, the adhesive strength A preferably has a difference (BA) from the adhesive strength B of 0.02 to 0.2 MPa.

Further, as described above, the outer peripheral honeycomb fired body is a honeycomb fired body that constitutes a part of the outer periphery of the honeycomb structure regardless of the number of honeycomb fired bodies constituting the honeycomb structure. The bond strength B between the two honeycomb fired bodies refers to the bond strength measured by a three-point bending test for any two adjacent peripheral honeycomb fired bodies.

The adhesive strength can be measured by a three-point bending test performed by a method according to JIS R 1601.
That is, from the manufactured honeycomb structure, the sample was cut out so that the above-mentioned honeycomb fired body was present on both sides of the adhesive layer while the adhesive layer was present in the vertical direction of the middle part, Set so that the load point comes to the part, and bend three points.
The three-point bending strength can be calculated by the following equation (1).
σ = 3P (L−L ₁ ) / 2Bh ² (1)
In the above equation (1), σ is the three-point bending strength, P is the load, L-L ₁ is the distance between the fulcrums (unit mm), B is the width of the test piece (unit mm), and h is the thickness of the test piece. (Height, unit mm).

The main components of the adhesive layer for bonding the honeycomb fired bodies of the present invention are inorganic fibers and an inorganic binder, inorganic particles and an inorganic binder, or inorganic fibers and an inorganic particle and an inorganic binder.
Regarding the ratio of each component, when inorganic fiber and inorganic binder or inorganic particle and inorganic binder are contained as main components, the inorganic fiber or inorganic particle is 70 to 95 parts by weight with respect to the solid content of 5 to 30 parts by weight. In the case where inorganic fibers, inorganic particles, and an inorganic binder are included as main components, 35 to 65 parts by weight of inorganic particles and 30 to 60 parts by weight of inorganic fibers with respect to 5 to 30 parts by weight of the solid content of the inorganic binder. Is preferred.

The adhesive layer may contain an organic binder, but when used as an exhaust gas filter for a vehicle, it becomes high temperature, so that it easily decomposes and disappears and causes fluctuations in adhesive strength. It is desirable that the amount is contained.

Examples of the inorganic binder include silica sol and alumina sol. These may be used alone or in combination of two or more. Among inorganic binders, silica sol is desirable.

Examples of the inorganic fibers include ceramic fibers such as silica-alumina, mullite, alumina, and silica. These may be used alone or in combination of two or more. Among inorganic fibers, alumina fibers are desirable.

Examples of inorganic particles include carbides and nitrides, and specific examples include inorganic powders made of silicon carbide, silicon nitride, and boron nitride. These may be used alone or in combination of two or more. Among the inorganic particles, silicon carbide having excellent thermal conductivity is desirable.

The adhesive strength between the honeycomb fired bodies sandwiching the adhesive layer depends on the type and content of the inorganic binder in the adhesive layer, the type of inorganic particles and inorganic fibers, and the density of the adhesive layer.

Moreover, in order to adjust the adhesive strength between the honeycomb fired bodies, a pore forming agent such as balloons that are fine hollow spheres, spherical acrylic particles, or graphite may be added. This is because voids are formed in the adhesive layer.
The balloon is not particularly limited, and examples thereof include an alumina balloon, a glass micro balloon, a shirasu balloon, a fly ash balloon (FA balloon), and a mullite balloon. Of these, alumina balloons are desirable.

The thickness of the adhesive layer is preferably 0.5 to 2.0 mm.
If the thickness of the adhesive layer is less than 0.5 mm, the adhesive strength may be greatly reduced, and if it exceeds 2.0 mm, the cell opening ratio will be reduced, so that the function when used as an exhaust gas filter is reduced. It will decline. Moreover, when the thickness of the sealing material layer exceeds 2.0 mm, the pressure loss may increase.

Next, a method for manufacturing a honeycomb structure by binding a plurality of honeycomb fired bodies will be described.
FIG. 4 is an explanatory diagram showing a state in which a plurality of honeycomb fired bodies are bundled using an adhesive paste layer to produce a large prism-shaped honeycomb fired body 13 laminate.
In order to manufacture the honeycomb structure 10 by binding a plurality of honeycomb fired bodies, for example, as shown in FIG. After placing the honeycomb fired body 13 in an inclined state on the V-shaped base 100, an adhesive paste that becomes the adhesive layer 14 is applied to the two side surfaces 130a and 130b facing upward. The adhesive paste layer 140 is formed by coating with a uniform thickness, and the process of sequentially stacking the other honeycomb fired bodies 13 on the adhesive paste layer 140 is repeated, and a large prismatic shape having a predetermined size is formed. A laminated body of the honeycomb fired bodies 13 is produced.

In the present invention, the adhesive paste for adhering the central honeycomb fired bodies to each other at that time is an adhesive paste adjusted to have an adhesive strength of 0.02 to 0.2 MPa. On the other hand, as the adhesive paste for bonding the outer peripheral honeycomb fired bodies to each other, the adhesive layer adjusted to have higher adhesive strength than the adhesive layer for bonding the central honeycomb fired bodies to each other is formed. An adhesive paste layer is formed using an adhesive paste.

The adhesive strength of the adhesive layer (see 14c in FIG. 1 (a) and 24c in FIG. 3) between the central honeycomb fired body and the outer peripheral honeycomb fired body is not particularly limited. It may be the same as the adhesive strength A between the fired bodies, may be the same as the adhesive strength B between the outer peripheral honeycomb fired bodies, or may be an adhesive strength intermediate between them.

Next, the laminated body of the honeycomb fired bodies 13 is heated to dry and solidify the adhesive paste layer 140 to form the adhesive layer 14, and then, for example, a diamond cutter or the like is used to surround the outer peripheral portion of FIG. The ceramic block 15 is produced by cutting into a cylindrical shape as shown in a) and (b).

Then, by forming the sealing material layer 16 on the outer periphery of the ceramic block 15 using the sealing material paste, a plurality of honeycomb fired bodies 11, 12, and 13 are bundled through the adhesive layer 14. The structure 10 can be manufactured.

Examples of the organic binder contained in the adhesive layer include polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and the like.
These may be used alone or in combination of two or more.

Next, the entire manufacturing process of the honeycomb structure will be described.
First, as a ceramic raw material, two types of silicon carbide powders with different average particle sizes and an organic binder are dry mixed to prepare a mixed powder, and a liquid plasticizer, a lubricant and water are mixed to prepare a mixed liquid. Then, the mixed powder and the mixed liquid are mixed using a wet mixer to prepare a wet mixture for manufacturing a molded body.

The particle size of the silicon carbide powder is not particularly limited, but it is preferable that the honeycomb fired body produced through the subsequent firing step is smaller than the honeycomb formed body, for example, an average of 0.1 to 50 μm A combination of 100 parts by weight of powder having a particle diameter and 5 to 65 parts by weight of powder having an average particle diameter of 0.1 to 1.0 μm is preferable.

Subsequently, the wet mixture is charged into an extruder.
When the wet mixture is charged into an extruder, the wet mixture becomes a honeycomb formed body having a predetermined shape by extrusion. The honeycomb formed body is cut to a predetermined length and then dried using a dryer to obtain a dried honeycomb formed body.

Next, a predetermined amount of a sealing material paste serving as a sealing material is applied to the gas outflow side end of the cell group in which the gas inflow end surface opens and the gas inflow end of the cell in which the gas outflow end surface opens. Fill and seal the cell. When sealing the cells, for example, a sealing mask is applied to the end face of the honeycomb formed body (ie, the cut surface after the cutting process), and only the cells that need to be sealed are filled with the sealing material paste. Can be used.
A cell-sealed honeycomb formed body is manufactured through such steps.

Next, a degreasing process of heating the organic matter in the cell-sealed honeycomb molded body in a degreasing furnace is performed, and the honeycomb molded body is transported to the firing furnace and subjected to the firing process to produce a honeycomb fired body.
Thereafter, an adhesive paste set to have a predetermined adhesive strength is applied to the side surface of the honeycomb fired body by using the above-described method to form an adhesive paste layer having a predetermined thickness, and then another layer is formed thereon. A honeycomb structure is manufactured by repeating the step of stacking the honeycomb fired bodies to produce a laminated body of prism-shaped honeycomb fired bodies 13 having a predetermined size, and then performing drying to form a cylindrical shape. To do.

Hereinafter, effects of the honeycomb structure according to the present embodiment will be listed.
(1) During the regeneration process of the honeycomb structure, the central portion of the honeycomb structure is likely to have a higher temperature than the outer peripheral portion, and thus is considered to receive a larger thermal stress than the outer peripheral portion. In the honeycomb structure according to the first embodiment, the adhesive strength A between the central honeycomb fired bodies is as low as 0.02 to 0.2 MPa, so that the thermal stress received by the central honeycomb fired body is reduced by the adhesive layer. It is possible to prevent cracks from occurring at the center of the honeycomb structure.

(2) Furthermore, in the honeycomb structure according to the first embodiment, the adhesive strength B between the peripheral honeycomb fired bodies is higher than the adhesive strength A between the central honeycomb fired bodies, and the peripheral honeycomb Since the fired bodies have sufficient adhesive strength to maintain the shape of the honeycomb structure, the shape of the honeycomb structure does not collapse and the position of the honeycomb fired body does not shift.

(3) Since the bonding strength A between the center honeycomb fired bodies is 0.02 MPa or more, the center honeycomb fired body is difficult to come off from the honeycomb structure, and the above bond strength A is 0.2 MPa or less. The thermal stress received by the central honeycomb fired body is easily dispersed, and cracks and the like are less likely to occur.

Examples that more specifically disclose the first embodiment of the present invention are shown below, but the present invention is not limited to these examples.

In the following examples and comparative examples, a honeycomb structure is manufactured by the method according to the above-described embodiment and the conventional method, and the bonding strength A between the honeycomb fired bodies at the center and the honeycomb fired bodies at the outer periphery are obtained. The adhesive strength B was measured by a three-point bending test according to JIS R 1601. In addition, durability against cycle operation (thermal shock) was tested.

Example 1
(1) Wet-mixing 52.8% by weight of silicon carbide coarse powder having an average particle size of 22 μm and 22.6% by weight of fine powder of silicon carbide having an average particle size of 0.5 μm with respect to the resulting mixture 2.1% by weight of acrylic resin, 4.6% by weight of organic binder (methyl cellulose), 2.8% by weight of lubricant (Unilube manufactured by NOF Corporation), 1.3% by weight of glycerin, and 13.8% by weight of water % And kneaded to obtain a mixed composition, followed by extrusion molding, and a raw honeycomb molded body that is substantially the same shape as the honeycomb fired body 13 shown in FIG. Was made.
In addition, said each composition is a ratio with respect to the mixed composition obtained.

(2) Next, these raw honeycomb formed bodies are cut so that the length in the longitudinal direction is 150 mm, and then the raw honeycomb formed bodies are dried using a microwave dryer or the like, After forming the dried honeycomb molded body, a paste having the same composition as that of the generated molded body was filled in a predetermined cell, and dried again using a dryer.

(3) Next, the dried honeycomb formed body was degreased at 400 ° C., and fired in a normal pressure argon atmosphere at 2200 ° C. for 3 hours, thereby producing a honeycomb fired body 13.
The size of the honeycomb fired body 13 made of the manufactured silicon carbide fired body is 34.3 mm × 34.3 mm × 150 mm, the number of cells 13a (cell density) is 46.5 cells / cm ² , and the cell wall 13a The thickness was 0.25 mm and the porosity was 45%.

(4) Further, as an adhesive paste for bonding the central honeycomb fired bodies and an adhesive paste for bonding the peripheral honeycomb fired bodies, alumina fibers having an average fiber length of 20 μm and silicon carbide particles having an average particle diameter of 0.6 μm , Heat-resistant adhesive paste a, adhesive paste b, adhesive paste c, adhesive containing silica sol (silica content 30% by weight in sol), carboxymethylcellulose, ceramic balloon and water in the proportions shown in Table 1 Paste d and adhesive paste e were prepared and used in this example and Examples 2-5 and Comparative Examples 1-4 described below.
In this example, the adhesive paste for bonding the central honeycomb fired bodies and the adhesive paste for bonding the peripheral honeycomb fired bodies to each other shown in Table 2 were used, and the method shown in FIG. Then, an adhesive paste according to the place is applied to the side surface of the honeycomb fired body 13 so as to have the same thickness, and the honeycomb fired bodies 13 are stacked to be bundled to form a stack of large prismatic honeycomb fired bodies 13. A body was prepared and dried at 120 ° C. The thickness of the adhesive layer was 1.0 mm. As the adhesive paste for bonding the central honeycomb fired body and the outer peripheral honeycomb fired body, the same adhesive paste as that for bonding the central honeycomb fired bodies was used. The same applies to the following examples and comparative examples.

(5) Next, the cylindrical ceramic block 15 was produced by cutting using a diamond cutter.
(6) Next, ceramic fiber made of alumina silicate as inorganic fiber (shot content: 3%, average fiber length: 100 μm) 23.3% by weight, silicon carbide powder 30. 30 μm in average particle diameter as inorganic particles. 2% by weight, silica sol as inorganic binder (content of SiO _{2 in} the sol: 30% by weight) 7% by weight, organic binder as 0.5% by weight of carboxymethyl cellulose and 39% by weight of water mixed, kneaded and sealed A material paste was prepared.

Next, a sealing material paste layer having a thickness of 0.2 mm was formed on the outer peripheral portion of the ceramic block 15 using the sealing material paste. And this sealing material paste layer was dried at 120 degreeC, and the cylindrical honeycomb structure 10 of diameter 143.8mm x length 150mm was manufactured.

(Examples 2 to 5)
In the same manner as in Example 1 except that the composition of the adhesive paste for bonding the central honeycomb fired bodies in (4) and the adhesive paste for bonding the peripheral honeycomb fired bodies shown in Table 2 were used. A honeycomb structure was manufactured.

(Comparative Examples 1-4)
In the same manner as in Example 1 except that the composition of the adhesive paste for bonding the central honeycomb fired bodies in (4) and the adhesive paste for bonding the peripheral honeycomb fired bodies shown in Table 2 were used. A honeycomb structure was manufactured.

(Measurement of adhesive strength between honeycomb fired bodies)
As described above, the adhesive strength between the honeycomb fired bodies was measured by a three-point bending test performed by a method according to JIS R 1601.
That is, from the obtained honeycomb structure, a sample was cut out so that there was an adhesive layer in the vertical direction of the middle part, and a honeycomb fired body was present on both sides of the adhesive layer. Was set so that the load point would be, and a three-point bending test was performed using an Instron testing machine (manufactured by Instron), and the bending strength was calculated based on the following equation (1).

σ = 3P (L−L ₁ ) / 2Bh ² (1)
In the formula (1), σ is a three-point bending strength. Support span _{(L-L 1)} is, 57 mm, the width B of the specimen, 34.3 mm, the thickness (height) h of the test piece is 25 mm. The results are shown in Table 2.

(Durability against cycle operation)
First, the honeycomb structures according to Examples 1 to 5 and Comparative Examples 1 to 4 are respectively arranged in the exhaust passage of the engine, and further, a commercially available catalyst carrier (diameter: 144 mm, length) on the gas inflow side from the honeycomb structure. : 100 mm, cell (cell density): 400 cells / inch ² , platinum carrying amount: 5 g / L) is used as an exhaust gas purification device, and the engine is caught at a rotational speed of 3000 min ⁻¹ and a torque of 50 Nm for 7 hours. Gathered. The amount of particulates collected was 8 g / L in all cases.

After that, the engine was set at a rotational speed of 1250 min ⁻¹ and a torque of 60 Nm, and the filter temperature was kept constant for 1 minute, followed by post-injection, and using the oxidation catalyst on the gas inflow side to set the exhaust temperature. Raised and burned the particulates.
The post-injection conditions were set such that the center temperature of the honeycomb structure became substantially constant at 600 ° C. one minute after the start of post-injection. And the said process was repeated 10 times and it was observed whether the crack etc. generate | occur | produced in the honeycomb structure. The results are shown in Table 2.

As is clear from the results shown in Table 2, the honeycomb structures according to Examples 1 to 5 in which the adhesive strength A between the central honeycomb fired bodies is lower than the adhesive strength B between the peripheral honeycomb fired bodies are cycled. Comparative Example 1 in which no cracks or the like were observed in the honeycomb structure even though the adhesion strength A between the central honeycomb fired bodies was higher than or the same as the adhesive strength B between the outer peripheral honeycomb fired bodies. In the honeycomb structure according to ˜4, cracks were observed in the adhesive layer.

(Second embodiment)
In the first embodiment, as the honeycomb fired body constituting the honeycomb structure, a honeycomb fired body in which a sealing material layer is formed at either end of the cell is used. However, the honeycomb fired body constituting the honeycomb structure is Unlike the honeycomb fired body 13 shown in FIG. 2A, a honeycomb fired body in which the sealing material layer 13c is not formed at any end of the cell 13a may be used.
A honeycomb structure made of such a honeycomb fired body can be suitably used as a catalyst carrier. Among these, by carrying a catalyst such as a noble metal, harmful gas components such as CO, HC and NOx in the exhaust gas can be purified.

In this case, it is desirable to form a catalyst support layer on the honeycomb structure and then support the catalyst on the catalyst support layer.
The material for forming the catalyst supporting layer is preferably a material having a high specific surface area and capable of supporting the catalyst in a highly dispersed state, and examples thereof include oxide ceramics such as alumina, titania, zirconia, and silica. .
These materials may be used alone or in combination of two or more.
Among these, it is desirable to select one having a high specific surface area of 250 m ² / g or more, and γ-alumina is particularly desirable.

The method for forming the catalyst support layer made of alumina is not particularly limited, and the honeycomb structure is impregnated with a solution of a metal compound containing aluminum, for example, an aqueous solution of aluminum nitrate. Alternatively, a method may be used in which an alumina film is coated on the cell wall, and the honeycomb structure is dried and fired.

As the catalyst to be supported on the surface of the catalyst supporting layer, for example, a noble metal such as platinum, palladium, rhodium or the like is desirable, and among these, platinum is more desirable. As other catalysts, for example, alkali metals such as potassium and sodium, alkaline earth metals such as barium, and oxide catalysts can be used. These catalysts may be used alone or in combination of two or more.

(Third embodiment)
Fig.5 (a)-(c) is a perspective view which shows one Embodiment of a honeycomb calcination body, respectively.
In the first and second embodiments, the honeycomb structure 10 to be manufactured is obtained by bonding the honeycomb fired bodies 11 to 13 through the adhesive layer 14, and the sealing material layer is formed on the outer periphery ( FIG. 1 (b)) shows a honeycomb structure according to the present invention, in which the honeycomb fired bodies 31, 32, and 33 as shown in FIGS. 5 (a) to 5 (c) are bonded via an adhesive layer to form a columnar shape. A honeycomb structure in which the aggregate is formed and the sealing material layer is not formed may be used.

In this case, the honeycomb fired body 31 corresponds to the honeycomb fired body 11 shown in FIG. 1 (b), and the honeycomb fired body 32 corresponds to the honeycomb fired body 12. However, a wall portion also exists in the portion corresponding to the outer periphery. Since it is formed, a sealing material layer is not particularly required.
Further, in the honeycomb structure having such a structure, it is not necessary to cut a cylindrical body after cutting a large square pillar-shaped honeycomb fired body by bonding the honeycomb fired bodies together. A honeycomb structure can be manufactured efficiently.
Even when a honeycomb structure is manufactured using the honeycomb fired bodies 31, 32, and 33, a sealing material layer may be formed as necessary to increase the strength of the outer peripheral wall.

(Other embodiments)
The shape of the honeycomb structure of the present invention is not limited to the columnar shape shown in FIG. 1B, and may be any column shape such as an elliptical column shape or a polygonal column shape.
Further, the number of honeycomb fired bodies constituting the honeycomb structure is not limited to 16 or 25 as in the above-described embodiment, but may be any other number.

The porosity of the honeycomb structure of the present invention is desirably 30 to 70%.
This is because the strength of the honeycomb structure can be maintained and the resistance when the exhaust gas passes through the cell walls can be kept low.

On the other hand, if the porosity is less than 30%, the cell walls may be clogged at an early stage. On the other hand, if the porosity exceeds 70%, the strength of the honeycomb structure is lowered and easily broken. May be.
The porosity can be measured by a conventionally known method such as a mercury intrusion method, an Archimedes method, or a measurement using a scanning electron microscope (SEM).

The cell density in the cross section perpendicular to the longitudinal direction of the honeycomb structure is not particularly limited, but a desirable lower limit is 31.0 cells / cm ² (200 cells / in ² ), and a desirable upper limit is 93.0 cells / cm ^2. (600 / in ² ), more desirable lower value is 38.8 / cm ² (250 / in ² ), and more desirable upper limit is 77.5 / cm ² (500 / in ² ).

The main component of the constituent material of the honeycomb structure is not limited to silicon carbide, and other ceramic raw materials include, for example, nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride, zirconium carbide, It may be a carbide ceramic such as titanium carbide, tantalum carbide or tungsten carbide, a composite of metal and nitride ceramic, a composite of metal and carbide ceramic, or the like.
In addition, ceramic raw materials such as silicon-containing ceramics in which metallic silicon is mixed with the above-described ceramics, and ceramics bonded with silicon or a silicate compound are also included as constituent materials.

The main component of the constituent material of the honeycomb structure is particularly preferably silicon carbide. It is because it is excellent in heat resistance, mechanical strength, thermal conductivity and the like.
In addition, silicon carbide containing metal silicon (silicon-containing silicon carbide) is also desirable.

The organic binder used when preparing the wet mixture is not particularly limited, and examples thereof include carboxymethyl cellulose, hydroxyethyl cellulose, and polyethylene glycol. Of these, carboxymethylcellulose is desirable. In general, the blending amount of the organic binder is desirably 1 to 10 parts by weight with respect to 100 parts by weight of the ceramic powder.

The plasticizer and lubricant used when preparing the wet mixture are not particularly limited, and examples of the plasticizer include glycerin and the like. Examples of the lubricant include polyoxyalkylene compounds such as polyoxyethylene alkyl ether and polyoxypropylene alkyl ether.
Specific examples of the lubricant include polyoxyethylene monobutyl ether and polyoxypropylene monobutyl ether.
In some cases, the plasticizer and the lubricant may not be contained in the wet mixture.

In preparing the wet mixture, a dispersion medium liquid may be used. Examples of the dispersion medium liquid include water, alcohols such as methanol, and organic solvents such as benzene.
Furthermore, a molding aid may be added to the wet mixture.
The molding aid is not particularly limited, and examples thereof include ethylene glycol, dextrin, fatty acid, fatty acid soap, polyalcohol and the like.

Furthermore, a pore-forming agent such as balloons that are fine hollow spheres containing oxide ceramics, spherical acrylic particles, and graphite may be added to the wet mixture as necessary.
The balloon is not particularly limited, and examples thereof include an alumina balloon, a glass micro balloon, a shirasu balloon, a fly ash balloon (FA balloon), and a mullite balloon. Of these, alumina balloons are desirable.

In addition, the organic content in the wet mixture is desirably 10% by weight or less, and the moisture content is desirably 8 to 30% by weight.

Although it does not specifically limit as a sealing material paste which seals a cell, The thing from which the porosity of the sealing material manufactured through a post process becomes 30 to 75% is desirable, For example, the thing similar to a wet mixture is used. be able to.

Even in the case of a honeycomb structure in which either end of the cell is sealed and functions as a filter, the catalyst can be supported. Thereby, the same effect as in the case of the catalyst carrier can be obtained. That is, by supporting an oxide catalyst or the like on a honeycomb structure including a honeycomb fired body in which a sealing material layer is formed at any end of the cell, the combustion temperature of the particulates can be lowered, Curate can be burned efficiently. In addition, by supporting a catalyst such as a noble metal, harmful gas components such as CO, HC and NOx in the exhaust gas can be purified.

FIG. 1A is a longitudinal sectional view showing an embodiment of a honeycomb structure of the present invention, and FIG. 1B is a perspective view of the honeycomb structure. Fig.2 (a) is a perspective view which shows the honeycomb fired body 13 which comprises the honeycomb structure shown to Fig.1 (a) and (b), (b) is the sectional view on the AA line. . FIG. 3 is a longitudinal sectional view of a honeycomb structure 20 in which 25 honeycomb fired bodies 21, 22, 23, and 27 are bundled in 5 vertical × 5 horizontal. FIG. 4 is an explanatory diagram showing a state in which a plurality of honeycomb fired bodies are bundled using an adhesive paste layer to produce a large prism-shaped honeycomb fired body 13 laminate. Fig.5 (a)-(c) is a perspective view which shows one Embodiment of the honeycomb fired body which comprises the honeycomb structure of this invention.

Explanation of symbols

10, 20 Honeycomb structure 11, 12, 13, 31, 32, 33 Honeycomb fired bodies 14 (14a, 14b, 14c), 24 (24a, 24b, 24c), adhesive layers 15, 25 Ceramic blocks 16, 26 Seals Material layer 13a, 31a, 32a, 33a Cell 13b, 31b, 32b, 33b Cell wall 13c Sealing material 130a, 130b Side surface

Claims (4)

Columnar honeycomb fired bodies in which a large number of cells are arranged in parallel in the longitudinal direction across the cell wall are a honeycomb structure in which a plurality of cells are bound via an adhesive layer,
Among the honeycomb fired bodies, the adhesive strength A measured by a three-point bending strength test between the center-part honeycomb fired bodies located at the center of the cut surface obtained by cutting the honeycomb structure with a cross section perpendicular to the longitudinal direction is: 0.02 to 0.2 MPa, and
The adhesive strength A is lower than the adhesive strength B measured by a three-point bending strength test between the outer peripheral honeycomb fired bodies constituting part of the outer periphery of the honeycomb structure of the honeycomb fired bodies. Honeycomb structure. Difference (BA) between adhesive strength A measured by a three-point bending strength test between the central honeycomb fired bodies and adhesive strength B measured by a three-point bending strength test between the peripheral honeycomb fired bodies The honeycomb structure according to claim 1, which has a pressure of 0.02 to 0.2 MPa. The honeycomb structure according to claim 1 or 2, wherein any one end of the cell is sealed. The honeycomb structure according to any one of claims 1 to 3, wherein the adhesive layer is mainly composed of inorganic fibers and an inorganic binder, inorganic particles and an inorganic binder, or inorganic fibers, an inorganic particle, and an inorganic binder.

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