JP5313878B2 - Honeycomb structure using honeycomb segment - Google Patents

Description

  The present invention relates to a honeycomb segment used for constituting a honeycomb structure and a honeycomb structure constituted by integrally joining a plurality of the honeycomb segments.

  Honeycomb structures are widely used as filters for collecting exhaust gas, for example, diesel particulate filters (DPF) for capturing and removing particulate matter (particulates) such as soot contained in exhaust gas from diesel engines, etc. ing.

  Such a honeycomb structure is disposed so that a plurality of cells that are partitioned and formed by porous partition walls made of, for example, silicon carbide (SiC) are parallel to each other in the central axis direction. Have a structure. Moreover, the edge part of the adjacent cell is plugged alternately (in a checkered pattern). That is, one cell is open at one end and the other end is sealed, and another cell adjacent thereto is sealed at one end and the other end is open. doing.

  By adopting such a structure, the exhaust gas flowing into a predetermined cell (inflow cell) from one end is passed through a cell (outflow cell) adjacent to the inflow cell by passing through a porous partition wall. When the particulate matter (particulates) in the exhaust gas is captured by the partition wall when it is allowed to flow out and pass through the partition wall, the exhaust gas can be purified.

  In order to use such a honeycomb structure (filter) continuously for a long period of time, it is necessary to periodically regenerate the filter. That is, in order to reduce the pressure loss increased by the particulates accumulated with time in the filter and return the filter performance to the initial state, it is necessary to burn and remove the particulates accumulated in the filter. When the filter is regenerated, a large thermal stress is generated, and this thermal stress causes a defect such as a crack or breakage in the honeycomb structure. In order to meet this demand for improved thermal shock resistance against thermal stress, a honeycomb structure with a split structure that has a function of dispersing and relaxing thermal stress by integrally bonding a plurality of honeycomb segments with a bonding material layer A body has been proposed and its thermal shock resistance can be improved to some extent.

  However, in recent years, the demand for larger-sized filters has increased, and as a result, the thermal stress generated during regeneration also increases, and in order to solve the above problems, the thermal shock resistance of the structure is further increased. Improvement is now strongly desired. In order to realize this improvement in thermal shock resistance, a bonding material layer for integrally bonding a plurality of honeycomb segments is required to have an excellent stress relaxation function and bonding strength.

  As a means to meet these demands, the addition of inorganic fibers and organic binders to the sealing material (bonding material layer) suppresses the occurrence of migration during the drying and curing process, thereby preventing the occurrence of the aforementioned defects. A ceramic structure (honeycomb structure) that is intended to suppress and improve durability is disclosed (see Patent Document 1).

However, in the seal material (bonding material layer) used in the ceramic structure (honeycomb structure) disclosed in Patent Document 1, the structure realized by the intertwining of inorganic fibers and organic binders is shown in FIG. Thus, voids 20 are likely to be formed at the intersections 17 of the bonding material layer 9 formed between the honeycomb segments 2, and it becomes difficult to ensure the bonding strength at the interface between the honeycomb segment 2 and the bonding material layer 9, There has been a problem that deterioration such as peeling occurs at the interface after filter regeneration.
Japanese Patent No. 3121497

  The present invention has been made in view of such conventional circumstances, and has excellent thermal shock resistance, which is useful as an exhaust gas dust collection filter, particularly a DPF. In particular, defects such as cracks are generated during filter regeneration. The main object is to provide a honeycomb structure that is effectively suppressed.

  In order to achieve the above object, according to the present invention, the following honeycomb segment and honeycomb structure are provided.

[ 1 ] A honeycomb segment bonded body in which a plurality of honeycomb segments are integrally bonded to each other through a bonding material layer formed by drying a bonding material composition containing moisture, and the honeycomb segment bonded body A honeycomb structure having a structure in which a plurality of cells serving as fluid flow paths are arranged so as to be parallel to each other in the central axis direction. A plurality of cells serving as fluid flow paths are arranged so as to be parallel to each other in the central axis direction, and the shape of the cross section perpendicular to the central axis direction of the honeycomb segment is a quadrangle, The shape of the cross section perpendicular to the central axis direction is a quadrangle, and the cells located on the outermost periphery of the honeycomb segment exist in parallel to the outer wall of the honeycomb segment. The thickness of the outer wall of the honeycomb segment measured in a diagonal direction in the rectangular cross section of the honeycomb segment and the thickness of the edge satisfy the relationship of the following formula (1): A honeycomb structure in which adjacent cells are plugged with a filler on opposite end surfaces .
Corner thickness / edge thickness> 1.05 (1)

  When a honeycomb structure is produced using the honeycomb segment of the present invention, large voids that cause a decrease in the strength of the interface between the honeycomb segment and the bonding material layer are unlikely to occur at the intersection of the bonding material layers, When used in a filter for collecting exhaust gas such as DPF, the occurrence of defects such as cracks during filter regeneration is effectively suppressed, and excellent thermal shock resistance is exhibited.

It is a perspective view showing typically an example of an embodiment of a honeycomb segment of the present invention. It is a perspective view which shows typically another example of embodiment of the honeycomb segment of this invention. It is AA sectional drawing in FIG. It is a perspective view showing typically an example of an embodiment of a honeycomb structure of the present invention. It is a principal part enlarged view of FIG. FIG. 3 is a plan view for explaining “corner thickness” in the honeycomb segment of the present invention. FIG. 4 is a plan view for explaining “the thickness of the edge” in the honeycomb segment of the present invention. It is a fragmentary sectional view which shows the cross | intersection part of the joining material layer formed between honeycomb segments.

Explanation of symbols

1: honeycomb structure, 2: honeycomb segment, 4: outer periphery coating layer, 5: cell, 6: partition wall, 7: filler, 8: outer wall, 9: bonding material layer, 10: bonded honeycomb segment body, 12: corner Part, 13: edge part, 17: crossing part, 20: void.

  Hereinafter, the present invention will be described based on specific embodiments, but the present invention should not be construed as being limited thereto and based on the knowledge of those skilled in the art without departing from the scope of the present invention. Various changes, modifications, and improvements can be added.

  As described above, the honeycomb segment of the present invention is a honeycomb segment in which a plurality of cells serving as fluid flow paths are arranged in parallel to each other in the central axis direction, and the thickness of the corner of the outer wall of the honeycomb segment Is thicker than the thickness of the edge.

In the honeycomb segment of the present invention, the “corner thickness” means the thickness t _{1 of} a plurality of corners (corner portions) 12 present on the outer wall 8 of one honeycomb segment 2 as shown in FIG. , T ₂ , t ₃ , t ₄ is the thickness of the thinnest one. Further, as shown in FIG. 7, the “thickness of the edge” means that the outer walls 8a, 8b, 8c, and 8d connecting the corners are equidistant from the corners 12 at both ends. The thicknesses T ₁ , T ₂ , T ₃ , and T ₄ of the outer wall at the position (intermediate position) are measured, and the average value of the obtained measured values is taken.

  As shown in FIG. 8, when a plurality of honeycomb segments 2 are combined and bonded via the bonding material layer 9, an intersection 17 is formed in the bonding material layer 9. In the intersecting portion 17 of the bonding material layer 9, the large void 20 that causes a decrease in bonding strength at the interface between the honeycomb segment 2 and the bonding material layer 9 is formed when the bonding material layer 9 is formed. When the bonding material composition obtained by kneading the constituent material of the bonding material layer 9 with water or the like into a paste is applied to the bonding surface (outer wall) of the honeycomb segment 2 and the honeycomb segments 2 are combined, the moisture in the bonding material composition However, it is thought that it is generated by being dried in a state where it is not so much absorbed by the surrounding honeycomb segment 2 and remains in a large amount in the bonding material composition.

Therefore, in the honeycomb segment of the present invention, as shown in FIG. 1, when the honeycomb segments are combined, the thickness of the corner portion 12 of the outer wall 8 in contact with the intersecting portion of the bonding material layer is larger than the thickness of the edge portion 13. I did it. When the corner 12 is thus thickened, when the bonding material composition as described above is applied to the bonding surface of the honeycomb segment 2 and the honeycomb segments 2 are combined, the moisture in the bonding material composition is More corners 12 around the intersection 17 are absorbed and the amount of moisture remaining in the intersection 17 is reduced. This causes a decrease in the bonding strength at the interface between the honeycomb segment 2 and the bonding material layer 9. Such a large void 20 is less likely to occur.

In the honeycomb segment 2 of the present invention, the thickness of the corner 12 of the outer wall 8 and the thickness of the edge 13 preferably satisfy the relationship of the following formula (1), and satisfy the relationship of the following formula (2). More preferably, it is still more preferable to satisfy | fill the relationship of the following Formula (3).
Corner thickness / edge thickness> 1.05 (1)
Corner thickness / edge thickness> 1.10 (2)
Corner thickness / edge thickness> 1.15 (3)

  In the case where the thickness of the corner 12 of the outer wall 8 and the thickness of the edge 13 do not satisfy the relationship of the above formula (1), the water in the bonding material composition is sufficient for the corner 12 around the intersection 17. Large voids that are not absorbed and that cause a decrease in the bonding strength at the interface between the honeycomb segment 2 and the bonding material layer 9 are likely to occur at the intersections 17, making it difficult to ensure the necessary bonding strength. There is a case.

  The honeycomb segment of the present invention has a structure in which each cell is plugged on one of the end faces in the same manner as a honeycomb segment conventionally used for manufacturing a honeycomb structure used as a filter for collecting dust such as DPF. It can be. FIG. 2 is a perspective view schematically showing an example of the honeycomb segment of the present invention to which such a plugging structure is applied, and FIG. 3 is a cross-sectional view taken along line AA in FIG. In this example, adjacent cells 5 of the honeycomb segment 2 have a structure in which plugs 7 are plugged at opposite end surfaces.

  A honeycomb structure of the present invention includes a honeycomb segment bonded body in which a plurality of the honeycomb segments of the present invention are integrally bonded with each other through a bonding material layer, and an outer peripheral surface of the honeycomb segment bonded body. The outer peripheral coat layer to be coated has a structure in which a plurality of cells serving as fluid flow paths are arranged so as to be parallel to each other in the central axis direction.

  Since the honeycomb structure of the present invention is configured using the honeycomb segment of the present invention as described above, it may cause a decrease in strength of the interface between the honeycomb segment and the bonding material layer at the intersection of the bonding material layers. Such large voids are unlikely to be generated, and when used in a dust collection filter for exhaust gas such as DPF, the occurrence of defects such as cracks during filter regeneration is effectively suppressed, and excellent thermal shock resistance is exhibited.

  FIG. 4 is a perspective view schematically showing an example of an embodiment of the honeycomb structure of the present invention produced using the honeycomb segment shown in FIG. 2, and FIG. 5 is an enlarged view of a main part of FIG.

  This honeycomb structure 1 is obtained by integrally bonding the honeycomb segments of the present invention as shown in FIG. In the honeycomb structure 1 of the present invention, the honeycomb segment 2 is joined to obtain the honeycomb segment joined body 10, and then the outer peripheral portion thereof is processed into a desired shape such as a cylindrical shape by grinding or the like, if necessary. Therefore, by coating the outer peripheral surface with a coating material and forming the outer peripheral coat layer 4, an arbitrary cross sectional shape can be obtained.

  The cells 5 are arranged so as to be parallel to each other in the central axis direction of the honeycomb structure 1, and the respective end portions of the adjacent cells 5 are alternately sealed with the fillers 7. That is, in a predetermined cell 5 (inflow cell), as shown in FIG. 3, the left end side is open, while the right end side is sealed with the filler 7, and another cell 5 adjacent thereto is sealed. In the (outflow cell), the left end side is sealed with the filler 7, but the right end side is open. By such sealing, as shown in FIG. 2, the end face of the honeycomb segment 2 has a checkered pattern. When such a honeycomb structure 1 to which a plurality of honeycomb segments 2 are joined is arranged in an exhaust gas exhaust system, the exhaust gas flows into the cells 5 of each honeycomb segment 2 from the left side in FIG. 3 and moves to the right side. .

FIG. 3 shows a case where the left side of the honeycomb segment 2 serves as an exhaust gas inlet, and the exhaust gas flows into the honeycomb segment 2 from the open cells 5 (inflow cells) without being plugged. The exhaust gas flowing into the cell 5 (inflow cell) passes through the porous partition wall 6 and flows out from the other cell 5 (outflow cell). When passing through the partition walls 6, particulate matter (particulates) containing soot in the exhaust gas is captured by the partition walls 6. In this way, exhaust gas can be purified. By such trapping, particulate matter containing particulates (particulates) containing soot accumulates with time in the honeycomb segment 2 and the pressure loss increases, so regeneration that soot is burned is performed.

  In the present embodiment, the shape of the cross section perpendicular to the central axis direction of the honeycomb segment is a quadrangle, but other shapes such as a triangle and a hexagon may be used. Moreover, the cross-sectional shape of the cell may be a shape other than a quadrangle such as a triangle, a hexagon, a circle, and an ellipse.

  The bonding material layer 9 is formed from a bonding material composition obtained by kneading the constituent material of the bonding material layer 9 together with water or the like into a paste, and is applied to the outer wall surface (bonding surface) of the honeycomb segment 2 to bond the honeycomb segments 2 to each other. Functions to join. The bonding material composition for forming the bonding material layer 9 may be applied to the outer wall surfaces of the adjacent honeycomb segments 2, but between the adjacent honeycomb segments 2, You may do it only for one side. Such application to only one side of the corresponding surface is preferable because the amount of the bonding material composition for forming the bonding material layer 9 can be saved.

  The direction in which the bonding material composition for forming the bonding material layer 9 is applied is particularly limited, such as the longitudinal direction in the honeycomb segment outer wall surface, the direction perpendicular to the longitudinal length in the honeycomb segment outer wall surface, and the direction perpendicular to the honeycomb segment outer wall surface. Although not necessarily applied, it is preferably applied in the longitudinal direction in the outer wall surface of the honeycomb segment. The thickness of the bonding material layer 9 is determined in consideration of the bonding force between the honeycomb segments 2 and is appropriately selected within a range of 0.5 to 3.0 mm, for example.

  The bonding material layer preferably contains inorganic fibers as fillers, and as other components, for example, inorganic binders, organic binders, inorganic particles, foamed particles, and the like are preferably contained.

Examples of the inorganic fiber include oxide fibers such as aluminosilicate, alumina, SiO ₂ —MgO and SiO ₂ —CaO—MgO, and other fibers (for example, SiC fibers). Examples of the inorganic binder include silica sol, alumina sol, clay and the like. Examples of the organic binder include polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), methyl cellulose (MC) and the like. Examples of the inorganic particles include ceramics such as silicon carbide, silicon nitride, cordierite, alumina, and mullite. Examples of the expanded particles include microcapsules (such as acrylic resin microcapsules).

  The content of the inorganic fiber is preferably 20 to 45% by mass, and more preferably 30 to 40% by mass. When the content of the inorganic fiber is less than 20% by mass, elasticity may not be imparted to the bonding material layer. When the content exceeds 45% by mass, a large amount of water is required to obtain a paste that can be applied. The use of a large amount of water may increase the shrinkage during drying of the bonding material layer and generate cracks.

  The shot content of the inorganic fibers is preferably 10 to 50% by mass. If the shot content is less than 10% by mass, a large amount of water is required to obtain a paste that can be applied, and the use of this large amount of water increases the shrinkage when the bonding material layer is dried and generates cracks. There are things to do. On the other hand, if the shot content exceeds 50% by mass, elasticity may not be imparted to the bonding material layer.

  The inorganic fiber preferably has an average diameter value in a cross section perpendicular to the major axis direction of 1 to 20 μm, and more preferably 2 to 15 μm. If the average diameter value in the cross section perpendicular to the major axis direction of the inorganic fiber is less than 1 μm, the bonding material layer may not be given elasticity, and if it exceeds 20 μm, the thickness of the bonding material layer is greatly affected. In some cases, it may be difficult to uniformly apply onto the outer wall surface of the honeycomb segment.

  The inorganic fiber has an average length in the major axis direction of preferably 10 to 600 μm, and more preferably 50 to 300 μm. If the average length of the inorganic fibers in the major axis direction is less than 10 μm, the bonding material layer may not be provided with elasticity, and if it exceeds 600 μm, the coating strength may be lowered.

  The material of the honeycomb segment 2 is a silicon-silicon carbide based composite material formed from silicon carbide (SiC), silicon carbide (SiC) as an aggregate and silicon (Si) as a binder from the viewpoint of strength and heat resistance. And at least one selected from the group consisting of silicon nitride, cordierite, mullite, alumina, spinel, silicon carbide cordierite composite, lithium aluminum silicate, aluminum titanate, and Fe-Cr-Al metal. Things can be mentioned. Among these, those made of silicon carbide (SiC) or a silicon-silicon carbide based composite material are preferable.

  For example, the honeycomb segment 2 is prepared by adding a binder such as methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol, a surfactant, water as a solvent, and the like to those appropriately selected from the above materials. Thus, it is possible to obtain a plastic clay, extrude the clay so as to have the above-mentioned shape, and then dry it with microwaves, hot air or the like and then sinter.

  As the filler 7 used for plugging the cells 5, the same material as that of the honeycomb segment 2 can be used. For example, the plugging with the filler 7 is performed by immersing the end face of the honeycomb segment 2 in the slurry-like filler 7 in the state where the cells 5 that are not plugged are masked (opened). This can be done by filling the cell 5. Filling of the filler 7 may be performed before or after firing after the formation of the honeycomb segment 2, but is preferably performed before firing because the firing process is completed once.

  After manufacturing the honeycomb segment 2 as described above, a paste-like bonding material composition is applied to the outer wall surface of the honeycomb segment 2 to form a bonding material layer 9, and a predetermined three-dimensional shape (the entire honeycomb structure 1 is formed). A plurality of honeycomb segments 2 are assembled so as to have a structure, and after being bonded in this assembled state, they are heated and dried. In this manner, a joined body in which the plurality of honeycomb segments 2 are integrally joined is manufactured. Thereafter, if necessary, the outer peripheral portion of the joined body is ground into a predetermined shape, and a coating material for forming the outer peripheral coat layer 4 is coated on the outer peripheral surface, followed by heat drying. In this way, the honeycomb structure 1 shown in FIG. 1 is manufactured. As the material of the coating material, the same material as the bonding material layer 9 can be used. The thickness of the coating material is appropriately selected within a range of 0.1 to 1.5 mm, for example.

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

(Manufacture of honeycomb segments)
As a honeycomb segment raw material, SiC powder and metal Si powder are mixed at a mass ratio of 80:20, and starch and foamed resin are added as a pore former, and methylcellulose and hydroxypropoxylmethylcellulose, a surfactant and water are added. Thus, a plastic clay was produced. This kneaded clay is extruded and dried with microwaves and hot air, and the partition wall thickness is 310 μm, the cell density is about 46.5 cells / cm ² (300 cells / square inch), the cross section is a square with a side of 35 mm, A honeycomb segment molded body having a length of 152 mm was obtained. Next, one end face of each cell was plugged so that the end face of the honeycomb segment formed body had a checkered pattern. That is, plugging was performed so that adjacent cells were sealed at opposite ends. As the plugging filler, the same material as the honeycomb segment raw material was used. After the cells were plugged and dried in this manner, the porous silicon-silicon carbide system was degreased at about 400 ° C. in an air atmosphere and then fired at about 1450 ° C. in an Ar inert atmosphere. The honeycomb segments of Examples 1 to 6 and Comparative Examples 1 and 2, which are composed of a composite material and have the thicknesses of the corners and edges of the outer wall and the ratio of the thicknesses shown in Table 1, were obtained.

(Preparation of bonding material composition)
Using aluminosilicate fiber as inorganic fiber, colloidal silica and clay as inorganic binder, SiC as inorganic particles, adding water, organic binder (CMC, PVA), foaming resin and dispersant to the mixture of these, in a mixer Kneading was performed for 30 minutes to obtain a paste-like bonding material composition.

(Preparation of honeycomb structure)
The outer surface of the honeycomb segment is coated with a bonding material composition so as to have a thickness of about 1 mm to form a bonding material layer, and a process of placing another honeycomb segment thereon is repeated. A honeycomb segment laminated body composed of 16 honeycomb segments combined into four was manufactured, pressure was applied from the outside, the whole was bonded, and then dried at 140 ° C. for 2 hours to obtain a bonded honeycomb segment. The outer periphery of the bonded honeycomb segment assembly thus obtained was ground into a cylindrical shape, and the outer peripheral surface was coated with a coating material to form an outer peripheral coat layer, which was dried and cured at 700 ° C. for 2 hours to obtain a honeycomb structure. It was.

(Evaluation of honeycomb structure)
A shear test was performed using the obtained honeycomb structure, and the strength measured by the test was used as the bonding strength at the interface between the honeycomb segment and the bonding material layer, and the results are shown in Table 1. The obtained honeycomb structure was subjected to an engine test (E / G test), and the results are shown in the same table. In addition, the specific method of a shear test and an engine test (E / G test) is as follows.

Shear test:
Two adjacent segments were cut out from the honeycomb structure in a joined state, one honeycomb segment was fixed, and a load F was applied to the other honeycomb segment from the major axis direction.

Engine test (E / G test):
The exhaust gas from the diesel engine is allowed to flow through the honeycomb structure to deposit about 14 g / L of particulates in the honeycomb structure, and then heated under a temperature condition such that the temperature at the center of the honeycomb structure becomes 1000 ° C. The particulates thus deposited were burned and removed, and then it was examined whether peeling occurred at the interface between the honeycomb segment of the honeycomb structure and the bonding material layer. In Table 1, “◯” indicates that no peeling occurred, and “x” indicates that peeling occurred.

(Discussion)
As shown in Table 1, the honeycomb structure manufactured using the honeycomb segments of Examples 1 to 6 in which the thickness of the corner / the thickness of the edge> 1.05 is obtained at the interface between the honeycomb segment and the bonding material layer. Bonding strength was high, and peeling at the interface after the E / G test was not observed. On the other hand, the honeycomb structure manufactured using the honeycomb segments of Comparative Examples 1 and 2 where the thickness of the corner / the thickness of the edge ≦ 1.05 has a low bonding strength at the interface between the honeycomb segment and the bonding material layer. , Peeling at the interface after the E / G test was observed. This peeling is considered to be because the bonding strength at the interface could not withstand the thermal stress generated during the E / G test.

  The honeycomb structure formed using the honeycomb segment of the present invention can be suitably used as a dust collection filter for exhaust gas such as DPF.

Claims (1)

A honeycomb segment bonded body in which a plurality of honeycomb segments are integrally bonded to each other through a bonding material layer formed by drying a bonding material composition containing moisture, and an outer peripheral surface of the honeycomb segment bonded body A honeycomb structure having a structure in which a plurality of cells serving as fluid flow paths are arranged so as to be parallel to each other in the central axis direction.
The honeycomb segment is arranged such that a plurality of cells serving as fluid flow paths are parallel to each other in the central axis direction,
The shape of the cross section perpendicular to the central axis direction of the honeycomb segment is a quadrangle,
The shape of the cross section perpendicular to the central axis direction of the cell is a quadrangle,
The cells located on the outermost periphery of the honeycomb segment exist parallel to the outer wall of the honeycomb segment;
The thickness of the corner and the edge of the outer wall of the honeycomb segment measured in the diagonal direction in the rectangular cross section of the honeycomb segment satisfy the relationship of the following formula (1):
A honeycomb structure in which adjacent cells of the honeycomb segment are plugged with a filler on opposite end surfaces .
Corner thickness / edge thickness> 1.05 (1)

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