Segment joint body

Abstract

A segment joint body includes a plurality of honeycomb structure segments having at least one planar side face, in which the plurality of honeycomb structure segments are joined to each other at their planar side faces via a joining material, wherein for each of the plurality of honeycomb structure segments, among bending amount(s) of the at least one planar side face used to join the adjacent honeycomb structure segment, assuming a maximum bending amount is Smax (unit: mm), and a length of a line segment connecting a center of gravity of the first segment end face and a center of gravity of the second segment end face is L (unit: mm), Smax / L≤0.010 is satisfied.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present invention claims the benefit of priority to Japanese Patent Application No. 2025-59958 filed on Mar. 31, 2025 with the Japanese Patent Office, the entire contents of which are incorporated herein by reference in its entirety.FIELD OF THE INVENTION

[0002] The present invention is related to a segment joint body having a plurality of honeycomb structure segments joined to each other at their side faces via a joining material.BACKGROUND OF THE INVENTION

[0003] Particulate matter (hereinafter referred to as PM) in exhaust gas discharged from internal combustion engines such as diesel engines and gasoline engines contains soot. Soot is harmful to the human body, so its emission is regulated. Currently, in order to comply with exhaust gas regulations, filters made of porous ceramics with a pillar-shaped honeycomb structure, such as DPFs and GPFs, are widely used, which filter out soot and other PM by passing exhaust gas through porous ceramic partitions.

[0004] In order to continue using such a filter for a long period of time, the filter needs to be regenerated. That is, in order to eliminate the increase in pressure loss caused by PM that accumulates inside the filter over time, it is necessary to remove the PM that has accumulated inside the filter by burning it. During the regeneration of the filter, a large thermal stress is generated, which causes defects such as cracks and breaks in the filter.

[0005] In response to the demand for improved thermal shock resistance against such thermal stress, a filter has been proposed that has a segment structure in which the side faces of a plurality of honeycomb structure segments are joined together with a joining material to form a segment joint body that has the function of dispersing and mitigating thermal stress, and attempts also have been made to further improve its thermal shock resistance.

[0006] However, in recent years, there has been an increasing demand for larger filters, which leads to increased thermal stress during regeneration. In order to prevent the above-mentioned defects, there is a strong demand for improved thermal shock resistance. However, since the filter is made of porous ceramics, it is prone to bending when it is made large and long. Conventionally, known methods for suppressing bending of a filter include a method of adding a water-absorbent resin and a pore-forming material to a green body (Patent Literature 1) and a method of arranging a predetermined back plate on the inlet side of a die when the raw material for forming is subjected to extrusion molding (Patent Literature 2).PRIOR ARTPatent Literature[Patent Literature 1] Japanese Patent No. 4627498

[0008] [Patent Literature 2] Japanese Patent Application Publication No. 2023-149427SUMMARY OF THE INVENTION

[0009] The methods described in Patent Literature 1 and 2 contribute to suppressing the amount of bending of the honeycomb formed body before firing. However, since no consideration is given to bending during firing, there is still room for improvement in terms of suppressing bending of the fired product. Furthermore, the methods described in Patent Literatures 1 and 2 lack sufficient consideration for suppressing bending of the segment joint body, which is the final product. That is, there is insufficient consideration in view of the fact that the segment joint body is constructed by combining a plurality of honeycomb structure segments. The development of technology to suppress bending of the final product, the segment joint body, is expected to contribute to improving not only thermal shock resistance but also compressive strength, and therefore will be particularly beneficial in the field of filters, in which increase in size has been progressing.

[0010] In view of the above circumstances, an object of one embodiment of the present invention is to provide a segment joint body in which bending is suppressed.[Aspect 1]

[0011] A segment joint body,

[0012] wherein the segment joint body comprises a plurality of honeycomb structure segments having at least one planar side face, in which the plurality of honeycomb structure segments are joined to each other at their planar side faces via a joining material,

[0013] wherein each of the plurality of honeycomb structure segments comprises a first segment end face, a second segment end face, and the at least one planar side face connecting the first segment end face and the second segment end face, and porous ceramic partition walls partitioning a plurality of cells extending from the first segment end face to the second segment end face, and

[0014] wherein for each of the plurality of honeycomb structure segments, among bending amount(s) of the at least one planar side face used to join the adjacent honeycomb structure segment, assuming a maximum bending amount is Smax (unit: mm), and a length of a line segment connecting a center of gravity of the first segment end face and a center of gravity of the second segment end face is L (unit: mm), Smax / L≤0.010 is satisfied.[Aspect 2]

[0015] The segment joint body according to aspect 1, wherein each of the plurality of honeycomb structure segments has Smax of 2.0 mm or less.[Aspect 3]

[0016] The segment joint body according to aspect 1, wherein each of the plurality of honeycomb structure segments has Smax of 1.0 mm or less.[Aspect 4]

[0017] The segment joint body according to aspect 1 or 2, wherein each of the plurality of honeycomb structure segments has L of 50 to 350 mm.[Aspect 5]

[0018] The segment joint body according to any one of aspects 1 to 4, wherein the segment joint body has a cylindrical outer shape with an outer peripheral side face, a first circular end face, and a second circular end face, and

[0019] wherein assuming a line segment connecting a center of gravity of the first circular end face and a center of gravity of the second circular end face as a central axis, and assuming distances in a same radial direction from the central axis to the outer peripheral side face at a height position 10 mm inward from the first circular end face in a direction in which the central axis extends, a height position 10 mm inward from the second circular end face in the direction in which the central axis extends, and a height position of the midpoint of the central axis are R1, R2, and R3, respectively, and |R3−(R1+R2) / 2| in the radial direction where an absolute value of |R3−(R1+R2) / 2| is maximum is defined as Fmax, then Fmax is 2.0 mm or less.[Aspect 6]

[0020] The segment joint body according to aspect 5, wherein Fmax is 1.0 mm or less.[Aspect 7]

[0021] The segment joint body according to any one of aspects 1 to 6, wherein an isostatic breaking strength is 1.0 MPa or more.[Aspect 8]

[0022] The segment joint body according to any one of aspects 1 to 7, wherein when a step of heating the segment joint body in an electric furnace at a set temperature for 60 minutes (when a volume of the segment joint body is 5 L or less) or 120 minutes (when the volume of the segment joint body is more than 5 L), removing the segment joint body from the electric furnace, allowing the segment joint body to cool to room temperature, and then visually inspecting to see whether or not a crack having a length of 3 mm or more has occurred in the segment joint body, is repeated with an initial temperature set to 200° C. and the set temperature is increased by 50° C. each time until the crack is confirmed, the set temperature at which the crack is confirmed is 250° C. or higher.[Aspect 9]

[0023] The segment joint body according to any one of aspects 1 to 8, wherein each of the plurality of honeycomb structure segments has a thermal conductivity of 3 W / (m·K) or more at 50° C. as measured by a disc heat flow meter method in accordance with ASTM E1530.[Aspect 10]

[0024] The segment joint body according to any one of aspects 1 to 9, wherein each of the plurality of honeycomb structure segments has an average coefficient of linear expansion of 5.5×10−6 / K or less when measured in accordance with JIS R1618: 2002 at temperatures ranging from 40° C. to 800° C.[Aspect 11]

[0025] The segment joint body according to any one of aspects 1 to 10, wherein each of the plurality of honeycomb structure segments has a porosity of 70% or less.[Aspect 12]

[0026] The segment joint body according to aspect 11, wherein each of the plurality of honeycomb structure segments has a porosity of 30% or more and 70% or less.[Aspect 13]

[0027] The segment joint body according to any one of aspects 1 to 12, wherein each of the plurality of honeycomb structure segments comprises 70 parts by mass or more of silicon carbide with respect to a total of 100 parts by mass of silicon carbide and silicon.[Aspect 14]

[0028] The segment joint body according to any one of aspects 1 to 13, wherein each of the honeycomb structure segments comprises silicon oxide, strontium oxide, and aluminum oxide, and a content of aluminum oxide is 1.0% or more with respect to a total mass of silicon oxide, strontium oxide, and aluminum oxide.[Aspect 15]

[0029] The segment joint body according to any one of aspects 1 to 14, wherein each of the plurality of honeycomb structure segments comprises 0.2 to 2.5 parts by mass of aluminum oxide with respect to a total of 100 parts by mass of silicon carbide and silicon.[Aspect 16]

[0030] A segment joint body,

[0031] wherein the segment joint body comprises a plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via a joining material,

[0032] wherein each of the plurality of rectangular parallelepiped honeycomb structure segments comprises a first segment side face, a second segment side face, a third segment side face, a fourth segment side face, a first segment end face, a second segment end face, and porous ceramic partition walls partitioning a plurality of cells extending from the first segment end face to the second segment end face, and

[0033] wherein for each of the plurality of rectangular parallelepiped honeycomb structure segments, among bending amounts of the first segment side face, the second segment side face, the third segment side face, and the fourth segment side face used to join the adjacent honeycomb structure segment, assuming a maximum bending amount is Smax (unit: mm), and a length of a line segment connecting a center of gravity of the first segment end face and a center of gravity of the second segment end face is L (unit: mm), Smax / L≤0.010 is satisfied.[Aspect 17]

[0034] The segment joint body according to aspect 16, wherein among the plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via the joining material, at least two rectangular parallelepiped honeycomb structure segments have the side face with the maximum bending amount oriented in the same direction.[Aspect 18]

[0035] The segment joint body according to aspect 17, wherein 30% or more of a total number of the plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via the joining material have the side face with the maximum bending amount oriented in the same direction.[Aspect 19]

[0036] The segment joint body according to aspect 17, wherein all of the plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via the joining material have the side face with the maximum bending amount oriented in the same direction.

[0037] According to one embodiment of the present invention, there is provided a segment joint body in which bending is suppressed. The segment joint body with suppressed bending has significantly improved thermal shock resistance and compressive strength, and is therefore particularly suitable for use in filters such as DPFs and GPFs, in which increase in size has been progressing.BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1A is a schematic end face view of a segment joint body according to one embodiment of the present invention.

[0039] FIG. 1B is a schematic side view of a segment joint body according to one embodiment of the present invention.

[0040] FIG. 2 shows a schematic perspective view of a honeycomb structure segment constituting the segment joint body according to one embodiment of the present invention.

[0041] FIG. 3 shows a schematic cross-sectional view of a honeycomb structure segment constituting the segment joint body according to one embodiment of the present invention, observed from a cross section parallel to the direction in which the cells extend.

[0042] FIG. 4 shows a schematic diagram illustrating a method for measuring R1, R2, and R3 for a segment joint body having a cylindrical outer shape.

[0043] FIG. 5 shows a schematic diagram illustrating a method for measuring the bending amount of a honeycomb structure segment.DETAILED DESCRIPTION OF THE INVENTION

[0044] Hereinafter, embodiments of the present invention will now be described in detail with reference to the drawings. It should be understood that the present invention is not intended to be limited to the following embodiments, and any change, improvement or the like of the design may be appropriately added based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.(1. Configuration of Segment Joint Body)

[0045] The segment joint body according to one embodiment of the present invention can be used, for example, as filters such as a DPF (Diesel Particulate Filter) or GPF (Gasoline Particulate Filter) that is installed to an exhaust gas line from a combustion device, typically an engine mounted on a vehicle, for collecting soot. The filter can be installed, for example, in an exhaust pipe, and a cushioning mat can be interposed between the inner surface of the exhaust pipe and the filter to hold the filter in the exhaust pipe.

[0046] FIG. 1A shows a schematic end face view of a segment joint body 10 according to one embodiment of the present invention. FIG. 1B shows a schematic side view of a segment joint body 10 according to one embodiment of the present invention. The segment joint body 10 comprises a first end face 104 which serves as an inlet for the exhaust gas, and a second end face 106 which serves as an outlet for the exhaust gas. The exhaust gas flowing in from the first end face 104 is purified while passing through the segment joint body 10 and is discharged from the second end face 106. The segment joint body 10 has a structure in which the planar side faces 102 of a plurality of honeycomb structure segments 100 are joined together via a joining material 107. By joining a plurality of honeycomb structure segments 100 together to provide a segment joint body, it is possible to improve the thermal shock resistance. In addition, the segment joint body 10 can have an outer peripheral wall 103 that is formed by grinding the outer peripheral portion into a desired shape (for example, cylindrical shape), applying a coating material to the outer peripheral side face, and then drying and heat treating the coating material.

[0047] In one embodiment, the plurality of honeycomb structure segments 100 constituting the segment joint body 10 include a plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces 102 via a joining material 107. The number of rectangular parallelepiped honeycomb structure segments in the segment joint body 10 is not limited, but can be, for example, 4 to 100, typically 9 to 81, and more typically 16 to 64. In addition, the proportion of rectangular parallelepiped honeycomb structure segments among the honeycomb structure segments of the segment joint body 10 is not limited, but can be, for example, 0 to 60%, typically 10 to 55%, and more typically 25 to 50%.(2. Properties of Segment Joint Body)

[0048] Hereinafter, some properties that can be exhibited by a segment joint body according to one embodiment of the present invention will be described.[2-1. Isostatic Breaking Strength]

[0049] One measure of the compressive strength of a segment joint body is the isostatic breaking strength. In measuring the isostatic breaking strength of the segment joint body, a test is conducted in which the segment joint body is submerged in water in a pressure vessel and the water pressure is gradually increased to apply isotropic pressure to the segment joint body. The water pressure inside the pressure vessel gradually increases, eventually causing damage to the partition walls and outer peripheral wall of the segment joint body. The pressure value (breaking strength) at which breakage occurs is the isostatic breaking strength. The isostatic breaking strength is measured based on the automotive standard (JASO M505-87) issued by the Japan Automotive Engineering Society.

[0050] For application as an exhaust gas filter and / or catalyst carrier for an automobile, it is desirable that the isostatic breaking strength of the segment joint body be high. The segment joint body according to one embodiment of the present invention can exhibit an isostatic breaking strength of 1.0 MPa or more. More preferably, the segment joint body can exhibit an isostatic breaking strength of 2.0 MPa or more, and even more preferably 5.0 MPa or more. There is no particular upper limit set for the isostatic breaking strength of the segment joint body, but taking into account the producing cost, it is usually 20 MPa or less, typically 15 MPa or less, and more typically 10 MPa or less. Therefore, the segment joint body according to one embodiment of the present invention can exhibit an isostatic breaking strength of, for example, 1.0 to 20 MPa, preferably can exhibit an isostatic breaking strength of 2.0 to 15 MPa, and more preferably can exhibit an isostatic breaking strength of 5.0 to 10 MPa.[2-2. Bending Amount]

[0051] In one embodiment, the segment joint body 10 has a cylindrical outer shape with an outer peripheral side face, a first circular end face, and a second circular end face. In this case, the outer peripheral side face of the segment joint body 10 corresponds to the outer surface of the outer peripheral wall 103. Further, the first circular end face corresponds to the first end face 104, and the second circular end face corresponds to the second end face 106. Assuming a line segment connecting the center of gravity O1 of the first end face 104 and the center of gravity O2 of the second end face as a central axis C, and assuming the distances in the same radial direction from the central axis C to the outer peripheral side face 103 at a height position 10 mm inward from the first end face 104 in a direction in which t the central axis C extends, a height position 10 mm inward from the second end face 106 in the direction in which the central axis C extends, and a height position of the midpoint of the central axis C are R1, R2, and R3, respectively, and |R3−(R1+R2) / 2| in the radial direction where an absolute value of |R3−(R1+R2) / 2| is maximum is defined as Fmax, then it is possible to achieve Fmax of 2.0 mm or less (see FIG. 4). It can be said that the smaller Fmax is, the more the bending of the segment joint body 10 is suppressed.

[0052] The segment joint body according to one embodiment of the present invention can preferably exhibit Fmax of 1.0 mm or less, and more preferably exhibit Fmax of 0.8 mm or less. Although the lower limit of Fmax is not particularly set, it is usually 0.05 mm or more, typically 0.1 mm or more, and more typically 0.15 mm or more. Therefore, the segment joint body according to one embodiment of the present invention can exhibit Fmax of, for example, 0.05 to 2.0 mm, preferably 0.1 to 1.0 mm, and more preferably 0.15 to 0.8 mm.

[0053] Fmax is defined as the maximum value among the absolute values of |R3−(R1+R2) / 2| measured at 3000 equally spaced points around the entire circumference of the segment joint body using a laser displacement meter. In Examples, a laser displacement meter, model ILD2200-200, manufactured by Micro-Epsilon, was used.

[0054] FIG. 4 shows a schematic diagram illustrating a method for measuring Fmax using a laser displacement meter 122. First, the segment joint body 10 to be measured is placed on a turntable 121 installed on a horizontal surface with the first end face 104 or the second end face 106 facing downward. When placing the segment joint body 10 on the turntable 121, the distance between the center of gravity O1 of the first end face 104 or the center of gravity O2 of the second end face 106 and the rotation axis of the turntable 121 does not necessarily have to be 0, and even if they are far apart, R1, R2 and R3 can be calculated geometrically, and depending on the displacement meter, they can also be calculated automatically.

[0055] The turntable 121 is configured to be rotatable at a predetermined rotation speed around a rotation axis extending in the vertical direction by a driving means such as a servo motor. The servo motor can be equipped with an encoder for detecting the amount of displacement, such as the rotation angle, of the turntable 121. The laser displacement meter 122 is attached to a support pillar 126 and is configured to be movable in the vertical direction by a driving means such as a motor.

[0056] Next, the height and orientation of the laser displacement meter 122 are adjusted to the appropriate conditions for measuring either R1, R2 or R3. Then, while the laser 124 is irradiated onto the surface of the outer peripheral wall 103 and the turntable 121 is rotated once, R1, R2 or R3 is measured at 3000 equally spaced points. This measurement allows to obtain the change in R1, R2 or R3 of the segment joint body 10 for one rotation. The change in R1, R2 or R3 for one rotation can be stored in a memory or the like in a computer in association with the rotation angle θ of the turntable 121. This allows R1, R2 or R3 to be associated with a particular radial direction on the surface of the outer peripheral wall 103. Similar measurements are carried out by changing the height of the laser displacement meter 122 to measure R1, R2 and R3, and Fmax is calculated based on the absolute value of |R3-(R1+R2) / 2| in the same radial direction. In addition, the direction of laser irradiation may be normal to the surface of the outer peripheral wall 103, but even if it is aimed in other directions, R1, R2 or R3 can be calculated geometrically, and depending on the displacement meter, they can also be calculated automatically.[2-3. ESP Crack Temperature]

[0057] According to one embodiment of the present invention, when an electric furnace spalling (E-sp) test is performed on the segment joint body under the following conditions, the set temperature at which cracks can be confirmed is 250° C. or higher, preferably 450° C. or higher, and typically 250° C. to 400° C. The electric furnace spalling test is a test in which the segment joint body is heated in an electric furnace at a set temperature for 60 minutes (when a volume of the segment joint body is 5 L or less) or 120 minutes (when the volume of the segment joint body is more than 5 L), then removed from the electric furnace and allowed to cool to room temperature, and then the segment joint body is visually inspected to see whether or not a crack having a length of 3 mm or more has occurred. This step is repeated with the initial temperature set to 200° C. while increasing the set temperature by 50° C. each time until the crack is confirmed, so that the set temperature at which the crack is confirmed is determined. In addition, the volume of the segment joint body is calculated based on the external dimensions of the segment joint body (for example, end face area×overall length).(3. Configuration of Honeycomb Structure Segment)

[0058] FIG. 2 shows a schematic perspective view of a honeycomb structure segment 100 constituting a segment joint body according to one embodiment of the present invention. FIG. 3 shows a schematic cross-sectional view of a honeycomb structure segment 100 constituting a segment joint body according to one embodiment of the present invention, observed in a cross section parallel to the direction in which the cells extend.

[0059] In one embodiment, the honeycomb structure segment 100 has a first segment end face 104S, a second segment end face 106S, and at least one planar side face 102 connecting the first segment end face 104S and the second segment end face 106S. When observing the honeycomb structure segment 100 from the side of the first segment end face 104S or the second segment end face 106S, it is typical that at least one planar side face 102 extends linearly, and two adjacent planar side faces 102 extend linearly in directions perpendicular to each other from a common vertex. The honeycomb structure segment 100 shown in FIG. 2 has an overall shape of a rectangular parallelepiped, and the outer surface of the outer peripheral side wall 113 is composed of a first segment side face 102A, a second segment side face 102B, a third segment side face 102C, and a fourth segment side face 102D.

[0060] Further, in one embodiment, the honeycomb structure segment 100 has an outer peripheral side wall 113 and partition walls 112 made of porous ceramics arranged on the inner side of the outer peripheral side wall 113, which partition a plurality of cells 108, 110 extending in parallel from the first segment end face 104S to the second segment end face 106S.

[0061] Each cell 108, 110 may penetrate from the first segment end face 104S to the second segment end face 106S by opening on both the first segment end face 104S and the second segment end face 106S. However, in order to improve the PM trapping performance, it is preferable that the honeycomb structure segment 100 have a plurality of first cells 108 extending from the first segment end face 104S to the second segment end face 106S, with the first segment end face 104S open and the second segment end face 106S plugged, and a plurality of second cells 110 adjacent to at least one first cell 108, extending from the first segment end face 104S to the second segment end face 106S, with the first segment end face 104S plugged and the second segment end face 106S open. In this case, the honeycomb structure segment 100 can be arranged such that the first cells 108 and the second cells 110 are alternately adjacent to each other with the partition walls 112 sandwiched therebetween so that both end faces have a checkerboard pattern.

[0062] When exhaust gas containing soot is supplied to the first segment end face 104S on the upstream side of the honeycomb structure segment 100, the exhaust gas is introduced into the first cells 108 and travels downstream within the first cells 108. Since the second segment end face 106S on the downstream side of the first cells 108 is plugged, the exhaust gas passes through the porous ceramic partition walls 112 that partitions the first cells 108 from the second cells 110 and flows into the second cells 110. Since the soot cannot pass through the partition walls 112, it is trapped and accumulated in the first cells 108. After the soot is removed, the clean exhaust gas that has flowed into the second cells 110 travels downstream within the second cells 110 and flows out from the second segment end face 106S on the downstream side.

[0063] The honeycomb structure segment 100 generally has a pillar outer shape. For example, it may be a pillar shape with polygonal end faces, or a pillar shape with the end faces formed by a combination of curve(s) and line segment(s). Examples of polygonal shapes include a quadrangle (a rectangle, a square, and the like), a hexagon, and the like. In a typical embodiment, the outer shape of the honeycomb structure segment 100 may be a rectangular parallelepiped.

[0064] When observing a honeycomb structure segment 100 according to one embodiment from the side of the first segment end face 104S or the second segment end face 106S, the side face 102 of the honeycomb structure segment 100 is composed of a curve constituting an arc, a first line segment extending from one end of the curve, and a second line segment extending from the other end of the curve in a direction perpendicular to the first line segment (100A in FIG. 1A). When observing a honeycomb structure segment 100 according to another embodiment from the side of the first segment end face 104S or the second segment end face 106S, the side face 102 of the honeycomb structure segment 100 is composed of a curve constituting an arc, a first line segment extending from one end of the curve, a second line segment extending from the other end of the curve, and a third line segment connecting the first line segment and the second line segment and extending in a direction perpendicular to both the first line segment and the second line segment (100B in FIG. 1A).

[0065] The size of the honeycomb structure segment 100 can be, for example, such that the area of the end face is 600 to 3600 mm2, typically 900 to 2500 mm2.

[0066] The length L (unit: mm) of the line segment connecting the center of gravity G1 of the first segment end face 104S and the center of gravity G2 of the second segment end face 106S can be, for example, 50 to 350 mm, and typically 100 to 250 mm. Within the above length range, from the viewpoint that the effect of improving thermal shock resistance by suppressing bending is more likely to become apparent, the length in the direction in which the cells of the honeycomb structure segment 100 extend is preferably 178 mm or more, more preferably 203 mm or more, and even more preferably 254 mm or more.

[0067] There are no limitations on the shape of the cells in a cross section orthogonal to the direction in which the first cells 108 and the second cells 110 extend (the height direction), but a quadrangle, a hexagon, an octagon, or a combination thereof is preferable. Among these, quadrangle and hexagonal shapes are preferable. By configuring the cell shape in this way, when the honeycomb structure segment 100 is used as a particulate filter, the pressure loss when exhaust gas flows through it is small, and the purification performance is excellent.

[0068] The means for suppressing bending of the segment joint body 10 includes: (1) a means for suppressing bending of each of the plurality of honeycomb structure segments 100 that constitute the segment joint body 10, and (2) a means for suppressing overall bending of the segment joint body 10 by devising an arrangement of the plurality of honeycomb structure segments 100 that constitute the segment joint body 10. Although either (1) or (2) may be adopted, it is preferable to adopt both means in combination.

[0069] First, the means (1) will be explained.

[0070] In one embodiment, each of the plurality of honeycomb structure segments 100 constituting the segment joint body 10 has at least one planar side face 102 used to join adjacent honeycomb structure segments. Each of the planar side face 102 of the honeycomb structure segments 100 used to join the adjacent honeycomb structure segments has a bending amount.

[0071] In another embodiment, each of the plurality of rectangular parallelepiped honeycomb structure segments 100 that constitute the segment joint body 10 has at least one of the first segment side face 102A, the second segment side face 102B, the third segment side face 102C, and the fourth segment side face 102D used to join adjacent honeycomb structure segments. The first segment side face 102A, the second segment side face 102B, the third segment side face 102C, and the fourth segment side face 102D are all planar side faces 102. Further, the first segment side face, the second segment side face, the third segment side face, and the fourth segment side face used to join the adjacent honeycomb structure segments each have a bending amount.

[0072] In any embodiment, for each honeycomb structure segment 100, among bending amount(s) of at least one planar side face used to join adjacent honeycomb structure segments, assuming the maximum bending amount is Smax (unit: mm), and the length of the line segment connecting the center of gravity G1 of the first segment end face 104S and the center of gravity G2 of the second segment end face 106S is L (unit: mm), it is preferable that Smax / L≤0.010 be satisfied. It is more preferable that in each of the plurality of rectangular parallelepiped honeycomb structure segments 100, Smax / L≤0.008 be satisfied, and it is even more preferable that Smax / L≤0.005 be satisfied. It is desirable that Smax / L be as small as possible, but taking into account the balance with producing costs, it is normal that 0.001≤Smax / L is satisfied, typically 0.002≤Smax / L is satisfied, and more typically 0.003≤Smax / L is satisfied. Therefore, for each of the plurality of rectangular parallelepiped honeycomb structure segments 100, it is preferable that, for example, 0.001≤Smax / L≤0.010 be satisfied, it is more preferable that 0.002≤Smax / L≤0.008 be satisfied, and it is even more preferable that 0.003≤Smax / L≤0.005 be satisfied.

[0073] The bending amount of the planar side face used to join adjacent honeycomb structure segments is measured by the following procedure. For example, when the honeycomb structure segment 100 has a rectangular parallelepiped shape, the segment joint body 10 is CT scanned using an X-ray CT scanning device to obtain a cross-sectional image parallel to the direction in which the cells of the honeycomb structure segment 100 to be measured extend, in which the first segment side face 102A and the third segment side face 102C (a pair of opposing side faces) are located at both left and right ends, the cross-sectional image taken at the center position in the depth direction of the honeycomb structure segment 100, as well as a cross-sectional image in which the second segment side face 102B and the fourth segment side face 102D (the other pair of opposing side faces) are located at both left and right ends, the cross-sectional image taken at the center position in the depth direction of the honeycomb structure segment 100 (see FIG. 5). Based on the cross-sectional image, the distance D (=bending amount) between the straight line Q connecting the upper and lower ends of the first segment side face 102A and the tangent line P to the first segment side face 102A that is parallel to the straight line Q and is farthest from the first segment side face 102A is calculated. The distance D (=bending amount) is similarly determined for the second segment side face 102B, the third segment side face 102C, and the fourth segment side face 102D, and the maximum value of the distance D is determined as the maximum amount of bending (Smax). If the honeycomb structure segment 100 is not rectangular parallelepiped, the bending amount can be similarly measured by performing a CT scan such that the planar side face 102, which is the object of measurement of the amount of bending, extends in the depth direction (from the front to the back) in the cross-sectional image.

[0074] It is also desirable that Smax itself be small. Therefore, each of the honeycomb structure segments 100 constituting the segment joint body 10 preferably has Smax of 2.0 mm or less, more preferably 1.0 mm or less, and even more preferably 0.5 mm or less. It is desirable that Smax be as small as possible, but considering the balance with producing costs, it is usually 0.1 mm or more, typically 0.3 mm or more, and more typically 0.4 mm or more. Therefore, for each of the honeycomb structure segments 100 constituting the segment joint body 10, Smax is preferably 0.1 to 2.0 mm, more preferably 0.3 to 1.0 mm, and even more preferably 0.4 to 0.5 mm.

[0075] Next, the means (2) will be explained. As described above, the segment joint body 10 according to one embodiment of the present invention includes a plurality of rectangular parallelepiped honeycomb structure segments 100 joined to each other at their side faces 102 via the joining material 107. Since it is difficult for all of the first segment side face 102A, the second segment side face 102B, the third segment side face 102C, and the fourth segment side face 102D that make up each rectangular parallelepiped honeycomb structure segment 100 to be flat, it is possible to identify the side face that has the maximum bending amount Smax among these. In this case, if the plurality of honeycomb structure segments are joined to each other in a state where the side faces having the maximum bending amount Smax are oriented in the same direction, the joint width becomes more uniform and stress concentration is avoided, resulting in improvement of thermal shock resistance and isostatic breaking strength.

[0076] Therefore, in the segment joint body 10 according to one embodiment of the present invention, among the plurality of rectangular parallelepiped honeycomb structure segments 100 joined to each other at their side faces via the joining material 107, at least two rectangular parallelepiped honeycomb structure segments 100 have the side face 102 with the maximum bending amount oriented in the same direction. In a preferred embodiment, 30% or more, more preferably 50% or more, and even more preferably 80% or more of the total number of the plurality of rectangular parallelepiped honeycomb structure segments 100 of the segment joint body 10 have the side face with the maximum bending amount oriented in the same direction. In the most preferred embodiment, all of the plurality of rectangular parallelepiped honeycomb structure segments 100 of the segment joint body 10 joined to each other at their side faces via the joining material have the side face with the maximum bending amount oriented in the same direction.

[0077] The material of the honeycomb structure segment 100 is not limited to, but may be, for example, porous ceramics. As the ceramics, mention can be made to cordierite, mullite, zirconium phosphate, aluminum titanate, silicon carbide, silicon-silicon carbide composite (for example, Si-bonded SiC), cordierite-silicon carbide composite, zirconia, spinel, indialite, sapphirine, corundum, titania, and silicon nitride. In addition, as the ceramics, one type can be contained alone, or two or more types may be contained in combination. Other materials for the honeycomb structure segment 100 include porous sintered metals containing alloy components whose main components are one or more elements selected from the group consisting of Fe, Cr, Mo, and Ni.

[0078] Among the above porous ceramics, silicon-silicon carbide composite is suitable for use in filters because they have excellent heat resistance, thermal shock resistance, and oxidation resistance. The silicon-silicon carbide composite contains silicon carbide particles as aggregate and silicon as a binder that bonds the silicon carbide particles, and it is preferable that a plurality of silicon carbide particles are bonded by the silicon so as to form pores among the silicon carbide particles.

[0079] However, segments made of silicon-silicon carbide composite are likely to bend due to shrinkage during firing. Further, when the porosity is high, the bending margin increases, and the segments are more likely to bend during firing. When joining a plurality of honeycomb structure segments 100 together with the joining material, if the bending amount of each honeycomb structure segment 100 is large, restrictions will be placed on the segments that can be joined, and furthermore, when the segments are joined together after the joining process and coating process, the bending is likely to become even larger. Therefore, when the honeycomb structure segment 100 contains a silicon-silicon carbide composite, typically when it contains 50% by mass or more of a silicon-silicon carbide composite, more typically when it contains 60% by mass or more of a silicon-silicon carbide composite, and even more typically when it contains 70% by mass or more of a silicon-silicon carbide composite, it is necessary to optimize the blending ratio of silicon and silicon carbide, as well as the type and blending ratio of the sintering aid such that bending is suppressed.

[0080] Specifically, because bending is more easily suppressed, the honeycomb structure segment 100 preferably contains 70 parts by mass or more, more preferably 75 parts by mass or more, and even more preferably 80 parts by mass or more of silicon carbide, with respect to the total of 100 parts by mass of silicon carbide and silicon. On the other hand, from the viewpoint of improving thermal conductivity and strength, the honeycomb structure segment 100 preferably contains 95 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 85 parts by mass or less of silicon carbide, with respect to the total of 100 parts by mass of silicon carbide and silicon. Therefore, the honeycomb structure segment 100 preferably contains, for example, 70 parts by mass or more and 95 parts by mass or less, more preferably 75 parts by mass or more and 90 parts by mass or less, and even more preferably 80 parts by mass or more and 85 parts by mass or less of silicon carbide, with respect to the total of 100 parts by mass of silicon carbide and silicon.

[0081] Furthermore, the honeycomb structure segment 100 preferably contains silicon oxide, strontium oxide, and aluminum oxide as firing aids to facilitate the melting of metallic silicon and thereby improve thermal conductivity and strength. In this case, from the viewpoint that the amount of silicon melted can be controlled, the honeycomb structure segment 100 preferably contains 1.0% or more, more preferably 3.0% or more, and even more preferably 6.0% or more of aluminum oxide relative to the total mass (100%) of silicon oxide, strontium oxide, and aluminum oxide. However, if the content of aluminum oxide becomes too high, the thermal conductivity and strength tend to decrease. Therefore, the honeycomb structure segment 100 preferably contains 15.0% or less, more preferably 12.0% or less, and even more preferably 9.0% or less of aluminum oxide, with respect to the total mass (100%) of silicon oxide, strontium oxide, and aluminum oxide. Therefore, the honeycomb structure segment 100 preferably contains, for example, 1.0 to 15.0%, more preferably 3.0 to 12.0%, and even more preferably 6.0 to 9.0% of aluminum oxide, with respect to the total mass (100%) of silicon oxide, strontium oxide, and aluminum oxide.

[0082] From the viewpoint of suppressing bending, it is preferable to control the content of silicon oxide, strontium oxide, and aluminum oxide with respect to the total mass of silicon carbide and silicon. Specifically, each of the plurality of rectangular parallelepiped honeycomb structure segments constituting the segment joint body, desirably all of the plurality of honeycomb structure segments constituting the segment joint body, preferably contains 5.0 to 35.0 parts by mass, more preferably 8.0 to 25.0 parts by mass, and even more preferably 11.0 to 20.0 parts by mass of silicon oxide, with respect to the total of 100 parts by mass of silicon carbide and silicon. In addition, each honeycomb structure segment preferably contains 0.0 to 10.0 parts by mass, more preferably 1.0 to 7.0 parts by mass, and even more preferably 2.0 to 5.0 parts by mass of strontium oxide, with respect to 100 parts by mass of the total of silicon carbide and silicon. Further, each honeycomb structure segment preferably contains 0.2 to 2.5 parts by mass, more preferably 0.5 to 2.0 parts by mass, and even more preferably 1.0 to 1.5 parts by mass of aluminum oxide, with respect to the total of 100 parts by mass of silicon carbide and silicon.

[0083] In order to suppress bending, it is also advantageous not to make the porosity of the honeycomb structure segment 100 too high. Specifically, the upper limit of the porosity of each of a plurality of rectangular parallelepiped honeycomb structure segments that constitute the segment joint body, and preferably all of the plurality of honeycomb structure segments that constitute the segment joint body, is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less. Making the porosity of the honeycomb structure segment 100 not too high is also advantageous in order to ensure strength and thermal conductivity. However, in order to prevent the pressure loss from increasing too much when the gas flows, the lower limit of the porosity of the honeycomb structure segment 100 is preferably 30% or more, more preferably 40% or more, and even more preferably 45% or more. Therefore, the porosity of the honeycomb structure segment 100 is, for example, preferably 30 to 70%, more preferably 40 to 60%, and even more preferably 45 to 50%.

[0084] Here, the porosity of the honeycomb structure segment 100 is defined as the average value when a plurality of samples of the partition walls 112 constituting the honeycomb structure segment 100 are taken from the honeycomb structure segment 100 without bias and the porosity of each sample is measured by mercury intrusion porosimetry. Specifically, the porosity is calculated using the mercury intrusion method (in accordance with JIS R 1655:2003).

[0085] The average thickness of the partition walls 112 in the honeycomb structure segment 100 is not particularly limited, but is preferably 0.1 mm to 0.5 mm. By setting the average thickness of the partition walls 112 to be preferably 0.1 mm or more, and more preferably 0.2 mm or more, the strength of the honeycomb structure segment 100 can be ensured. Further, by setting the average thickness of the partition walls 112 to preferably 0.5 mm or less, more preferably 0.4 mm or less, the pressure loss when the exhaust gas flows through the honeycomb structure segment 100 can be kept low.

[0086] As used herein, the thickness of the partition wall refers to a crossing length of a line segment that crosses the partition wall when the centers of gravity of adjacent cells are connected by this line segment in a cross-section orthogonal to the direction in which the cells extend. The average thickness of the partition walls refers to the average value of the thicknesses of all the partition walls in each honeycomb structure segment.

[0087] The cell density of the honeycomb structure segment is preferably 50 to 400 cells / inch2 (7.7 to 62.0 cells / cm2), more preferably 70 to 370 cells / inch2 (10.8 to 57.3 cells / cm2), and even more preferably 80 to 320 cells / inch2 (12.4 to 49.6 cells / cm2). If the cell density of the honeycomb structure segment is less than 50 cells / in2 (7.7 cells / cm2), sufficient strength may not be obtained. On the other hand, if the cell density of the honeycomb structure segment exceeds 400 cells / in2 (62.0 cells / cm2), the pressure loss becomes too high, which may result in a decrease in engine output when used as a DPF. As used herein, the cell density is a value obtained by dividing the number of cells by the area of one of the end faces (the first end face or the second end face) of the honeycomb structure segment (the total area of the partition walls and cells excluding the outer peripheral side wall).

[0088] In each honeycomb structure segment, the average thickness of the outer peripheral side wall 113 is not limited, but considering the balance between the strength and filter performance of the honeycomb structure segment 100, it can be, for example, 0.1 mm to 0.5 mm, and preferably 0.15 mm to 0.4 mm. As used herein, the average thickness of the outer peripheral side wall refers to an average value obtained by measuring the thicknesses of multiple points of the outer peripheral side wall without bias in a cross section orthogonal to the direction in which the cells extend.(4. Properties of Honeycomb Structure Segment)

[0089] Hereinafter, some properties that can be exhibited by a honeycomb structure segment according to one embodiment of the present invention will be described.[4-1. Thermal Conductivity]

[0090] The higher the thermal conductivity of the honeycomb structure segment is, the more the occurrence of temperature differences within the honeycomb structure segment is suppressed, and therefore the thermal shock resistance is improved. Further, the higher the thermal conductivity of the honeycomb structure segment is, the more the removal performance improves when PM trapped in the honeycomb structure segments is burned and removed for filter regeneration. In this regard, the honeycomb structure segment according to one embodiment of the present invention can exhibit high thermal conductivity. Specifically, the plurality of rectangular parallelepiped honeycomb structure segments constituting the segment joint body, preferably all of the plurality of honeycomb structure segments constituting the segment joint body, have a thermal conductivity at 50° C. measured by a disc heat flow meter method in accordance with ASTM E1530 of 3 W / (m·K) or more, preferably 10 W / (m·K) or more, and more preferably 20 W / (m·K) or more. There is no particular upper limit set for the thermal conductivity, but taking into account the producing cost, it is usually 40 W / (m·K) or less, typically 30 W / (m·K) or less, and more typically 25 W / (m·K) or less. Therefore, each honeycomb structure segment can exhibit a thermal conductivity of, for example, 3 to 40 W / (m·K), preferably 10 to 30 W / (m·K), and more preferably 20 to 25 W / (m·K).

[0091] The thermal conductivity of the honeycomb structure segment is measured by the following procedure. A rectangular pillar-shaped sample measuring 35 mm×35 mm×20 mm (length in the direction in which the cells extend) is cut out from the center of the honeycomb structure segment in the radial and height directions, and the thermal conductivity of the sample is measured using a measuring device in accordance with ASTM E1530 under the temperature conditions described above, which is taken as a measured value.[4-2. Average Coefficient of Linear Expansion (CTE)]

[0092] It is desirable that the honeycomb structure segments have low thermal expansion. Specifically, it is preferable that a plurality of rectangular parallelepiped honeycomb structure segments that constitute the segment joint body, and preferably all of the plurality of honeycomb structure segments that constitute the segment joint body, have an average coefficient of linear expansion of 5.5×10−6 / K or less when measured in accordance with JIS R1618: 2002 when the temperature is changed from 40° C. to 800° C. When the average coefficient of linear expansion is 5.5×10−6 / K or less, the thermal stress during exhaust gas treatment and filter regeneration, when the temperature of the honeycomb structure segments becomes high, is reduced, and thus the thermal shock resistance is significantly improved. The average coefficient of linear expansion is more preferably 5.4×10−6 / K or less, and even more preferably 5.3×10−6 / K or less. There is no particular lower limit to the average coefficient of linear expansion, but from the viewpoint of ease of production, the average coefficient of linear expansion is preferably 3.0×10−6 / K or more, more preferably 3.5×10−6 / K or more, and even more preferably 4.0×10−6 / K or more. Therefore, the average coefficient of linear expansion is, for example, preferably 3.0×10−6 / K or more and 5.5×10−6 / K or less, more preferably 3.5×10−6 / K or more and 5.4×10−6 / K or less, and even more preferably 4.0×10−6 / K or more and 5.3×10−6 / K or less.

[0093] The average coefficient of linear expansion of the honeycomb structure segment is measured by the following procedure. A rectangular pillar-shaped sample measuring 3 mm×3 mm×15 mm (length in the direction in which the cells extend) is cut out from the center of the honeycomb structure segment in the radial and height directions, and the average coefficient of linear expansion of the sample is measured under the above-mentioned temperature change conditions, which is taken as a measured value.(5. Joining Material)

[0094] The joining material 107 serves to join the side faces 102 of the honeycomb structure segments 100 together. In one embodiment, the joining material 107 is interposed in a layer form between the side faces 102 of the honeycomb structure segments 100 facing each other. The thickness of the joining material 107 (the length in the direction perpendicular to the joining surface of the joining material with the honeycomb structure segment) is determined taking into consideration the joining force (shear strength) between the honeycomb structure segments 100, and is appropriately selected, for example, in the range of 0.5 to 3.0 mm.

[0095] In one embodiment, the joining material 107 is porous. When the joining material 107 is porous, the higher the porosity, the more likely it is to achieve thermal shock resistance due to the stress relaxation effect. Therefore, the lower limit of the porosity of the joining material is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more. However, from the viewpoint of ensuring the joining strength, the upper limit of the porosity of the joining material is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. Therefore, the porosity of the joining material is, for example, preferably 40 to 80%, more preferably 50 to 75%, and even more preferably 60 to 70%.

[0096] The porosity of the joining material is calculated using a plurality of samples of the joining material collected from the segment joint body 10 without bias, based on the total pore volume (unit: cm3 / g) by mercury intrusion porosimetry (in accordance with JIS R 1655:2003) and the apparent density (unit: g / cm3) by the underwater Archimedes method. That is, the porosity here is the porosity before the catalyst is carried.

[0097] The joining material may contain one or more of ceramics or other inorganic substances, such as cordierite, mullite, alumina, silica, alumina silicate, wollastonite, mica, zirconium phosphate, aluminum titanate, silicon carbide, silicon-silicon carbide composite (for example, Si-bonded SiC), cordierite-silicon carbide composite, zirconia, spinel, indialite, sapphirine, corundum, titania, and silicon nitride. When the honeycomb structurer segment 100 contains the silicon-silicon carbide composite, the joining material preferably contains silicon carbide, alumina silicate, mullite, or alumina.(6. Method for Producing Segment Joint Body)

[0098] In a first embodiment of the method for producing a segment joint body according to the present invention comprises:

[0099] a step 1 of preparing a plurality of pillar-shaped honeycomb structure segments made of porous ceramics, having an outer peripheral side wall and partition walls that partition a plurality of cells extending from a first end face to a second end face on the inner peripheral side of the outer peripheral side wall; and

[0100] a step 2 of joining the side faces of the plurality of pillar-shaped honeycomb structure segments made of porous ceramics to each other using a joining slurry and drying the joining slurry;

[0101] In the step 1, a plurality of honeycomb structure segments made of porous ceramics are prepared, each having an outer peripheral side wall and partition walls that partition a plurality of cells extending from a first end face to a second end face on the inner peripheral side of the outer peripheral side wall. The honeycomb structure segment made of porous ceramics can be produced by adding some innovations to the producing process in accordance with a known method for producing a honeycomb structure, and an example of the procedure is given below.

[0102] First, a raw material composition containing a ceramic raw material, a dispersion medium, a pore-forming material, and a binder is kneaded to prepare a green body, and then the green body can be extrusion molded and dried to produce a honeycomb formed body. Additives such as dispersants can be blended into the raw material composition as needed. In the extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, and the like can be used.

[0103] In the drying step, a conventionally known drying method such as hot gas drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying, and the like can be used. Among these, a drying method that combines hot gas drying with microwave drying or dielectric drying is preferred, since it allows the entire formed body to be dried quickly and uniformly. As to plugging portions, they can be formed by forming plugging portions at predetermined positions on both end faces of the dried honeycomb formed body and then drying the plugging portions.

[0104] The ceramic raw material is a raw material of a portion that remains after firing and constitutes the skeleton of a pillar-shaped honeycomb formed body (pillar-shaped honeycomb structure) after firing as ceramics such as metal oxides and metals. Therefore, a firing aid is also a type of ceramic raw material. The ceramic raw material can be provided in the form of, for example, powder. As the ceramic raw material, mention can be made to raw materials for obtaining ceramics such as cordierite, mullite, zirconium phosphate, aluminum titanate, silicon carbide, silicon-silicon carbide composite (for example, Si-bonded SiC), cordierite-silicon carbide composite, zirconia, spinel, indialite, sapphirine, corundum, titania, silicon nitride, and the like. Specific examples include, but are not limited to, silicon carbide, silicon, silica, talc, alumina, kaolin, serpentine, pyroferrite, brucite, boehmite, mullite, magnesite, and aluminum hydroxide. In addition, silicon oxide, strontium oxide, aluminum oxide, and the like, which are added as firing aids, are also types of ceramic raw materials. As the ceramic raw material, one type may be used alone or two or more kinds may be used in combination.

[0105] The dispersion medium may be water or a mixed solvent of water and an organic solvent such as alcohol, and water is particularly preferred.

[0106] The pore-forming material is not particularly limited as long as it becomes pores after firing, and examples thereof include wheat flour, starch, foamed resin, water-absorbent resin, silica gel, carbon (for example, graphite, coke), ceramic balloon, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic, and phenol. As the pore-forming material, one type may be contained alone, and two or more types may be contained in combination. From the viewpoint of increasing the porosity of the honeycomb structure, the content of the pore-forming material is preferably 1 part by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, with respect to 100 parts by mass of the ceramic raw material. From the viewpoint of ensuring the strength of the honeycomb structure, the content of the pore-forming material is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, with respect to 100 parts by mass of the ceramic raw material.

[0107] As the binder, examples thereof include organic binders such as methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. In particular, it is preferable to use methylcellulose and hydroxypropylmethylcellulose in combination. In addition, from the viewpoint of increasing the strength of the honeycomb formed body before firing, the content of the binder is preferably 4 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 6 parts by mass or more, with respect to 100 parts by mass of ceramic raw material. From the viewpoint of suppressing cracks due to abnormal heat generation during the firing process, the content of the binder is preferably 9 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less, with respect to 100 parts by mass of the ceramic raw material. As the binder, one type may be used alone, or two or more types may be used in combination.

[0108] As the dispersant, ethylene glycol, dextrin, fatty acid soap, polyether polyol, and the like can be used. As the dispersant, one type may be used alone, or two or more types may be used in combination. The content of the dispersant is preferably 0 to 2 parts by mass with respect to 100 parts by mass of the ceramic raw material.

[0109] When plugging the end face of the honeycomb formed body, the method is not particularly limited, and a well-known method can be used, in which cell openings on the end face after a predetermined mask is attached on the end face are filled with a slurry for plugging. The material of the plugging portion is not particularly limited, but is preferably ceramic from the viewpoint of strength and heat resistance. As the ceramic, it is preferably a ceramic material containing one or more of cordierite, mullite, zirconium phosphate, aluminum titanate, silicon carbide, silicon-silicon carbide composite (for example, Si-bonded SiC), cordierite-silicon carbide composite, zirconia, spinel, indialite, sapphirine, corundum, titania, silicon nitride, and the like. The plugging portions are preferably formed of a material containing these ceramics in a total amount of 50% by mass or more, and more preferably 80% by mass or more. It is even more preferable that the plugging portions have the same material composition as the main body of the honeycomb formed body since this allows the coefficient of expansion during firing to be the same and leads to improved durability.

[0110] The dried honeycomb formed body is subjected to a degreasing step and a firing step, whereby a honeycomb structure segment can be produced. The conditions for the degreasing step and the firing step may be any known conditions that correspond to the material composition of the honeycomb formed body, and no particular explanation is necessary, but specific examples of the conditions are listed below.

[0111] The degreasing step will be described below. The combustion temperature of the binder is about 200° C., and the combustion temperature of the pore-forming material is about 300 to 1000° C. Therefore, the degreasing step may be carried out by heating the honeycomb formed body to a temperature in the range of about 200 to 1000° C. The heating time is not particularly limited, but is usually about 10 to 100 hours. The honeycomb formed body after the degreasing step is called a calcined body.

[0112] The firing step may be carried out by, for example, heating the calcined body to 1350 to 1600° C. in an air atmosphere and holding the calcined body for 3 to 10 hours, although depending on the material composition of the honeycomb formed body.

[0113] In order to suppress bending of the pillar-shaped honeycomb structure segments thus produced, it is important to minimize the amount of shrinkage of the honeycomb formed body during firing. Specifically, the shrinkage ratio (before firing / after firing) of the honeycomb formed body during firing is preferably 1.000 to 1.040 in the overall length direction and 1.000 to 1.050 in the radial direction, more preferably 1.000 to 1.020 in the overall length direction, and 1.000 to 1.030 in the radial direction, and even more preferably 1.000 to 1.010 in the overall length direction, and 1.000 to 1.020 in the radial direction. The shrinkage ratio in the overall length direction is calculated by measuring with a vernier caliper the change in the length L of the line segment connecting the center of gravity G1 of the first segment end face 104S and the center of gravity G2 of the second segment end face 106S before and after firing. The radial shrinkage ratio is determined by calculating the change in the length of the line segment M connecting the centers of gravity G3 and G4 of the opposing side faces 102 before and after firing using a vernier caliper for each of the two pairs of the opposing side faces 102, and the larger value is taken as the measured value.

[0114] In order to reduce the shrinkage ratio during firing, it is also preferable to make the particle size of the ceramic raw material powder fine and uniform (for example, a median diameter of 1 to 50 μm as determined by a laser diffraction / scattering method), and to adjust firing conditions such as the firing temperature (for example, 1400 to 2000° C.), holding time (for example, 1 to 5 hours), and atmosphere composition (for example, an inert atmosphere). In particular, when the objective is to produce a pillar-shaped honeycomb structure segment containing a silicon-silicon carbide composite, as mentioned above, it is important to optimize the blending ratio of silicon and silicon carbide, as well as the type and blending ratio of the firing aid.

[0115] Other methods for suppressing bending of honeycomb structure segments include lowering the firing temperature and reducing the amount of binder.

[0116] In the step 2, the side faces of a plurality of porous ceramic pillar-shaped honeycomb structure segments are joined to each other using a joining slurry, and the joining slurry is then dried. As a result, the joining slurry is converted into a joining material, and a segment joint body is prepared. Specifically, the segment joint body can be produced by the following procedure. With a film for preventing adhesion of the joining material attached to both end faces of each honeycomb structure segment, the joining slurry is applied to the joining surfaces (side faces). Next, these segments are placed adjacent to each other such that their side faces face each other, and the adjacent segments are pressed together, followed by heating and drying. In this way, a segment joint body is prepared in which the side faces of adjacent segments are joined to each other with the joining material.

[0117] The material of film for preventing adhesion of the joining material is not particularly limited, but suitable materials include synthetic resins such as polypropylene (PP), polyethylene terephthalate (PET), polyimide, and Teflon (registered trademark). In addition, the film preferably has an adhesive layer, and the material of the adhesive layer is preferably an acrylic resin, a rubber resin (for example, a rubber containing natural rubber or synthetic rubber as the main component), or a silicone resin.

[0118] The joining slurry can be prepared by mixing, for example, anisotropic inorganic powder, aggregate, pore-forming material, dispersion medium (for example, water and the like), and, if necessary, additives such as binders and dispersants.

[0119] As the material for the anisotropic inorganic powder, natural minerals or artificial ceramic fibers may be used. As natural minerals, mention can be made to needle-like or plate-like natural minerals such as wollastonite, mica, talc, sepiolite, palygorskite, and attapulgite. In addition, as artificial ceramic fibers, suitable ceramic fibers include RCF (amorphous refractory ceramic fiber mainly composed of alumina and silica), alumina fiber, mullite fiber, carbon fiber, silicon carbide fiber, boron nitride fiber, potassium titanate fiber, and zinc oxide fiber. The anisotropic inorganic powder may be used alone or in combination of two or more kinds.

[0120] As to materials for aggregate, mention can be made to ceramics such as cordierite, mullite, zirconium phosphate, aluminum titanate, silicon carbide, silicon-silicon carbide composite (for example, Si-bonded SiC), cordierite-silicon carbide composite, zirconia, spinel, indialite, sapphirine, corundum, titania, and silicon nitride.

[0121] The binder may be either an inorganic binder or an organic binder. As the organic binder, mention can be made to organic binders such as methyl cellulose, hydroxypropoxyl methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, and methyl cellulose. As the inorganic binder, mention can be made to clay minerals such as bentonite, montmorillonite, sepiolite, attapulgite, and the like. As the binder, one type can be used alone, or two or more types may be used in combination.

[0122] The joining slurry may further contain a dispersant such as polyethylene glycol oleate.

[0123] Examples of the pore-forming material include organic substances such as hollow or solid organic balloons (such as foamed resin), water-absorbent resins, starch, and inorganic substances such as fly ash balloons. The pore-forming material may be used alone or in combination of two or more.

[0124] If the solid content concentration of the joining slurry is too low, the joint width will be thin, whereas if it is too high, the joint width will be thick. Therefore, the solid content concentration of the joining slurry is, for example, preferably 50 to 90% by mass, more preferably 60 to 80% by mass, and even more preferably 65 to 75% by mass.

[0125] The outer periphery of the segment joint body produced by the above procedure may be ground to form a desired shape (for example, cylindrical), and a coating material may be applied to the outer periphery side face, followed by drying and heat treatment to form an outer periphery wall. The drying and heat treatment can be carried out under conditions of, for example, heating in an air atmosphere at 400 to 700° C., preferably 500 to 600° C., for 0.5 to 3 hours, preferably 0.5 to 1 hour. The coating material is not particularly limited, and known outer periphery coating materials can be used. Examples of the outer coating material include a slurry obtained by adding and kneading inorganic raw materials such as inorganic fibers, colloidal silica, clay, and ceramic particles with additives such as organic binders, foamed resins and dispersants, and water. In addition, the method for applying the outer periphery coating material is not particularly limited, and any known method can be used.

[0126] The filter may carry an appropriate catalyst depending on the application. An example of a method for carrying a catalyst on the filter includes introducing a catalyst slurry into the cells by a conventionally known suction method or the like, to adhere it to the surfaces and pores of the partition walls, and then performing a high-temperature treatment to bake the catalyst contained in the catalyst slurry onto the partition walls.

[0127] Examples of the catalyst include, but are not limited to, oxidation catalysts (DOCs) for increasing the exhaust gas temperature by oxidizing and burning hydrocarbons (HC) and carbon monoxide (CO), PM combustion catalysts for assisting in the combustion of PM such as soot, SCR catalysts and NSR catalysts for removing nitrogen oxides (NOx), and three-way catalysts capable of simultaneously removing hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). The catalyst may appropriately contain, for example, precious metals (Pt, Pd, Rh, and the like.), alkali metals (Li, Na, K, Cs, and the like.), alkaline earth metals (Ca, Ba, Sr, and the like.), rare earths (Ce, Sm, Gd, Nd, Y, La, Pr, and the like.), transition metals (Mn, Fe, Co, Ni, Cu, Zn, Sc, Ti, Zr, V, Cr, and the like.), and the like.

[0128] In particular, in DPFs for passenger cars, to simultaneously perform soot trapping and NOx purification, the DPF is loaded with an SCR catalyst such as Cu-substituted zeolite or Fe-substituted zeolite. In this case, NOx can be purified using ammonia obtained by decomposing urea on the vehicle.EXAMPLES

[0129] Hereinafter, the following examples are provided to provide a better understanding of the present invention and its advantages, but the present invention is not limited to these examples.Examples 1 to 6, Comparative Examples 1 to 3(1. Preparation of Honeycomb Structure Segment)

[0130] Silicon carbide (SiC) powder, silicon (Si) powder, silicon oxide (SiO2) powder, strontium oxide (SrO) powder, and aluminum oxide (Al2O3) powder were mixed in the mass ratios shown in Table 1 corresponding to the test number. To this mixture was added a pore-forming material (starch), an organic binder (hydroxypropylmethylcellulose), and a surfactant (oleic acid ester) in the mass ratios shown in Table 1, and then an appropriate amount of water was added to obtain a green body. Table 1 shows the median diameters of the silicon carbide (SiC) powder, silicon (Si) powder, and pore-forming material measured by a laser diffraction / scattering method.TABLE 1Raw material compositionSupplementary raw materials*Values when the total amount of ceramic Ceramic raw materialraw materials is 100 parts by massSiCSiPore-forming materialOrganic MedianMedian SiO2Al2O3SrOMedianbinderSurfactants[% by diameter[% by diameter[% by [% by [% by Parts diameterParts Parts Test No.mass][μm]mass][μm]mass]mass]mass]by mass[μm]by massby massExample 17730205.01.00.51.53.0205.50.1Example 27730205.01.00.51.53.0205.50.1Example 37725195.02.20.51.314256.50.1Example 47820175.03.40.31.322355.00.1Example 57630215.02.80.20.03.0205.50.1Example 67630195.01.00.53.50.5155.50.1Comparative6525315.02.00.51.52.5205.50.1Example 1Comparative7825175.03.40.11.513255.00.1Example 2Comparative8415115.03.10.41.530355.00.1Example 3

[0131] This green body was extrusion mold through a predetermined die and dried to obtain a rectangular parallelepiped honeycomb formed body having an outer peripheral side wall and partition walls that partition a plurality of cells extending from the first end face to the second end face. Plugging portions were formed at one end of each cell of the rectangular parallelepiped honeycomb formed body so that both end faces thereof would have a checkered pattern. That is, plugging portions were formed such that adjacent cells were plugged at the ends opposite to each other. The plugging portions were made of the same material as that of the pillar-shaped honeycomb formed body. After forming the plugging portions in this manner and drying, the pillar-shaped honeycomb formed body was degreased at approximately 450° C. in an air atmosphere and further fired at approximately 1450° C. in an Ar atmosphere to bond the SiC particles in the formed body with Si, thereby obtaining a rectangular parallelepiped honeycomb structure segment with the following specifications.

[0132] End face shape: Square with sides of 35 mm

[0133] Overall length (length L of the line segment connecting the center of gravity of the first segment end face and the center of gravity of the second segment end face): As listed in Table 3

[0134] Porosity: As listed in Table 2

[0135] Average partition wall thickness: 0.305 mm

[0136] Cell cross-sectional shape: Square

[0137] Cell density: 44 cells / cm2

[0138] Average outer side wall thickness: 0.5 mm

[0139] Composition: As listed in Table 2 (Composition analysis was performed using fluorescent X-rays and inert gas fusion method.)

[0140] Table 3 also shows the results of measuring the shrinkage ratio (in the overall length direction and in the radial direction) of the honeycomb formed body during firing for each test number using the method described above. The honeycomb structure segments for each test number were prepared in the number necessary to produce a segment joint body, which will be described later, and Table 3 shows the average values thereof.(2. Preparation of Joining Slurry)

[0141] Next, anisotropic inorganic powder (mullite fiber), aggregate (silicon carbide, cordierite), pore-forming material (foamed resin), binder (carboxymethyl cellulose), and dispersant (PEG monophosphate ester) were mixed in a mixer to obtain a joining slurry (solid content concentration=73% by mass).(3. Production of Segment Joint Body)

[0142] The joining slurry was applied to the side of a rectangular parallelepiped honeycomb structure segment obtained by the above-mentioned producing procedure to a thickness of approximately 1 mm, and the process of placing another honeycomb structure segment obtained by the above-mentioned producing procedure on top of it was repeated to prepare a segment stack consisting of a total of 16 honeycomb structure segments combined in a 4×4 matrix. Then, after the entire segment stack was joined by applying external pressure as appropriate, it was dried at 120° C. for 2 hours to obtain a segment joint body. In the segment joint body, the side faces of the plurality of rectangular parallelepiped honeycomb structure segments were joined to each other via the joining material.

[0143] When assembling the segment joint body, the percentage of the rectangular parallelepiped honeycomb structure segments having the side face with the maximum bending amount oriented in the same direction out of the total number of sixteen rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via the joining material was changed depending on the test number as shown in Table 3.

[0144] The outer periphery of this segment joint body was ground to form a cylindrical outer shape, and then a coating material with the same composition as the joining slurry was applied to the ground surface to reform the outer periphery wall. The segment joint body was then dried and hardened in the air atmosphere at 600° C. for 2 hours to obtain the final segment joint body (q160 mm) for each test example. The number of rectangular parallelepiped honeycomb structure segments in the segment joint body was 4. The thickness of the joining material was about 1.1 mm. In addition, a number of segment joint bodies required to carry out the following evaluation tests was produced.(4. Properties of Segment Joint Body)

[0145] The segment joint body obtained above was evaluated for the following properties as described above. The results are shown in Table 3.

[0146] (1) Maximum bending amount Smax of honeycomb structure segment

[0147] The maximum bending amount Smax of each honeycomb structure segment constituting the segment joint body corresponding to each test number was measured according to the method described above. The maximum value of the multiple Smax values measured for each honeycomb structure segment is shown in Table 3 as “Smax.” Table 3 also shows the ratio of “Smax” to the overall length L (Smax / L).

[0148] (2) Bending Fmax of segment joint body

[0149] (3) Thermal conductivity at 50° C. (measured by selecting an arbitrary segment before joining, but the same value would be obtained when measured for the joint body.)

[0150] (4) Average coefficient of linear expansion (CTE) when the temperature is changed from 40° C. to 800° C. (measured by selecting an arbitrary segment before joining, but the same value would be obtained when measured for the joint body).

[0151] (5) Isostatic breaking strength (isostatic strength)

[0152] (6) ESP crack temperature

[0153] In addition, the porosity of the joining material was about 70% for all of the joining segments.TABLE 2ProductSiC per 100 SiO2 per 100SrO per 100Al2O3 per 100Al2O3 ratio inparts by mass parts by mass parts by mass parts by mass sintering aid [%]of Si + SiCof Si + SICof Si + SiCof Si + SICAl2O3 / (SiO2 +PorosityText No.[parts by mass][parts by mass][perts by mass][parts by mass]SrO + Al2O3)[%]Example 181.911.62.61.06.943.2Example 281.911.62.61.06.943.2Example 385.512.72.61.48.248.0Example 489.623.53.02.07.162.5Example 578.310.90.00.262.345.0Example 680.910.47.31.47.336.5Comparative68.213.53.10.905.141.0Example 1Comparative86.318.32.70.180.845.3Example 2Comparative90.523.22.71.86.570.3Example 3TABLE 3Matching Shrink-rate of age Shrink-segment ratioage bending ESP (overall ratioTotaldirection ThermalIso-cracklength(radiallength whencon-CTEstatictem-Test direc-direc-LSmaxSmax / joined Fmaxductivity[ppm / strengthper-No.tion)tion)[mm][mm]L[%][mm][W / mK]K][MPa]atureEx-1.0101.0131800.450.00251000.1420.64.98.0450ample 1Ex-1.0101.0131800.450.0025 250.2120.64.96.0400ample 2Ex-1.0171.0202050.7 0.00321000.1719.14.92.4375ample 3Ex-1.0201.0322050.7 0.00341000.19 6.85.02.9375ample 4Ex-1.0151.0201801.4 0.0075 380.8826.04.85.5250ample 5Ex-1.0101.0101801.0 0.0056 440.2722.54.87.5250ample 6Com-1.0401.0511802.6 0.01461002.1033.94.50.9350parativeEx-ample 1Com-1.0421.0512052.6 0.01291002.1020.24.70.8325parativeEx-ample 2Com-1.0421.0531803.1 0.01751002.602.15.70.5200parativeEx-ample 3DESCRIPTION OF REFERENCE NUMERALS10: Segment joint body100: Honeycomb structure segment102: Side face

[0157] 102A: First segment side

[0158] 102B: Second segment side

[0159] 102C: Third segment side

[0160] 102D: Fourth segment side

[0161] 103: Outer peripheral wall

[0162] 104: First end face

[0163] 104S: First segment end face

[0164] 106: Second end face

[0165] 106S: Second segment end face

[0166] 107: Joining material

[0167] 108: First cell

[0168] 110: Second cell

[0169] 112: Partition wall

[0170] 113: Outer peripheral side wall

[0171] 121: Turntable

[0172] 122: Laser displacement meter

[0173] 124: Laser

[0174] 126: Support pillar

Claims

1. A segment joint body,wherein the segment joint body comprises a plurality of honeycomb structure segments having at least one planar side face, in which the plurality of honeycomb structure segments are joined to each other at their planar side faces via a joining material,wherein each of the plurality of honeycomb structure segments comprises a first segment end face, a second segment end face, an outer peripheral side wall having the at least one planar side face connecting the first segment end face and the second segment end face, and porous ceramic partition walls arranged on an inner side of the outer peripheral side wall and partitioning a plurality of cells extending from the first segment end face to the second segment end face, andwherein for each of the plurality of honeycomb structure segments, among bending amount(s) of the at least one planar side face used to join the adjacent honeycomb structure segment, assuming a maximum bending amount is Smax (unit: mm), and a length of a line segment connecting a center of gravity of the first segment end face and a center of gravity of the second segment end face is L (unit: mm), Smax / L≤0.010 is satisfied.

2. The segment joint body according to claim 1, wherein each of the plurality of honeycomb structure segments has Smax of 2.0 mm or less.

3. The segment joint body according to claim 1, wherein each of the plurality of honeycomb structure segments has Smax of 1.0 mm or less.

4. The segment joint body according to claim 1, wherein each of the plurality of honeycomb structure segments has L of 50 to 350 mm.

5. The segment joint body according to claim 1, wherein the segment joint body has a cylindrical outer shape with an outer peripheral side face, a first circular end face, and a second circular end face, andwherein assuming a line segment connecting a center of gravity of the first circular end face and a center of gravity of the second circular end face as a central axis, and assuming distances in a same radial direction from the central axis to the outer peripheral side face at a height position 10 mm inward from the first circular end face in a direction in which the central axis extends, a height position 10 mm inward from the second circular end face in the direction in which the central axis extends, and a height position of the midpoint of the central axis are R1, R2, and R3, respectively, and |R3−(R1+R2) / 2| in the radial direction where an absolute value of |R3−(R1+R2) / 2| is maximum is defined as Fmax, then Fmax is 2.0 mm or less.

6. The segment joint body according to claim 5, wherein Fmax is 1.0 mm or less.

7. The segment joint body according to claim 1, wherein an isostatic breaking strength is 1.0 MPa or more.

8. The segment joint body according to claim 1, wherein when a step of heating the segment joint body in an electric furnace at a set temperature for 60 minutes (when a volume of the segment joint body is 5 L or less) or 120 minutes (when the volume of the segment joint body is more than 5 L), removing the segment joint body from the electric furnace, allowing the segment joint body to cool to room temperature, and then visually inspecting to see whether or not a crack having a length of 3 mm or more has occurred in the segment joint body, is repeated with an initial temperature set to 200° C. and the set temperature is increased by 50° C. each time until the crack is confirmed, the set temperature at which the crack is confirmed is 250° C. or higher.

9. The segment joint body according to claim 1, wherein each of the plurality of honeycomb structure segments has a thermal conductivity of 3 W / (m·K) or more at 50° C. as measured by a disc heat flow meter method in accordance with ASTM E1530.

10. The segment joint body according to claim 1, wherein each of the plurality of honeycomb structure segments has an average coefficient of linear expansion of 5.5×10−6 / K or less when measured in accordance with JIS R1618: 2002 at temperatures ranging from 40° C. to 800° C.

11. The segment joint body according to claim 1, wherein each of the plurality of honeycomb structure segments has a porosity of 70% or less.

12. The segment joint body according to claim 11, wherein each of the plurality of honeycomb structure segments has a porosity of 30% or more and 70% or less.

13. The segment joint body according to claim 1, wherein each of the plurality of honeycomb structure segments comprises 70 parts by mass or more of silicon carbide with respect to a total of 100 parts by mass of silicon carbide and silicon.

14. The segment joint body according to claim 1, wherein each of the honeycomb structure segments comprises silicon oxide, strontium oxide, and aluminum oxide, and a content of aluminum oxide is 1.0% or more with respect to a total mass of silicon oxide, strontium oxide, and aluminum oxide.

15. The segment joint body according to claim 1, wherein each of the plurality of honeycomb structure segments comprises 0.2 to 2.5 parts by mass of aluminum oxide with respect to a total of 100 parts by mass of silicon carbide and silicon.

16. A segment joint body,wherein the segment joint body comprises a plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via a joining material,wherein each of the plurality of rectangular parallelepiped honeycomb structure segments comprises:an outer peripheral side wall having a planar first segment side face, a planar second segment side face, a planar third segment side face, and a planar fourth segment side face,a first segment end face,a second segment end face, andporous ceramic partition walls arranged on an inner side of the outer peripheral side wall and partitioning a plurality of cells extending from the first segment end face to the second segment end face, andwherein for each of the plurality of rectangular parallelepiped honeycomb structure segments, among bending amounts of the first segment side face, the second segment side face, the third segment side face, and the fourth segment side face used to join the adjacent honeycomb structure segment, assuming a maximum bending amount is Smax (unit: mm), and a length of a line segment connecting a center of gravity of the first segment end face and a center of gravity of the second segment end face is L (unit: mm), Smax / L≤0.010 is satisfied.

17. The segment joint body according to claim 16, wherein among the plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via the joining material, at least two rectangular parallelepiped honeycomb structure segments have the side face with the maximum bending amount oriented in the same direction.

18. The segment joint body according to claim 17, wherein 30% or more of a total number of the plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via the joining material have the side face with the maximum bending amount oriented in the same direction.

19. The segment joint body according to claim 17, wherein all of the plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via the joining material have the side face with the maximum bending amount oriented in the same direction.

20. A segment joint body,wherein the segment joint body comprises a plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via a joining material,wherein each of the plurality of rectangular parallelepiped honeycomb structure segments comprises a first segment side face, a second segment side face, a third segment side face, a fourth segment side face, a first segment end face, a second segment end face, and porous ceramic partition walls partitioning a plurality of cells extending from the first segment end face to the second segment end face,wherein for each of the plurality of rectangular parallelepiped honeycomb structure segments, among bending amounts of the first segment side face, the second segment side face, the third segment side face, and the fourth segment side face used to join the adjacent honeycomb structure segment, assuming a maximum bending amount is Smax (unit: mm), and a length of a line segment connecting a center of gravity of the first segment end face and a center of gravity of the second segment end face is L (unit: mm), Smax / L≤0.010 is satisfied, andwherein 30% or more of a total number of the plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via the joining material have the side face with the maximum bending amount oriented in the same direction.

21. The segment joint body according to claim 20, wherein all of the plurality of rectangular parallelepiped honeycomb structure segments joined to each other at their side faces via the joining material have the side face with the maximum bending amount oriented in the same direction.

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