Honeycomb structure, molding raw material composition, and method for manufacturing porous body

Abstract

To provide a honeycomb structure containing a silicon-silicon carbide composite material capable of suppressing thermal expansion.SOLUTION: The honeycomb structure comprises a partition wall that divides and forms a plurality of cells extending from one end face to the other end face. The partition wall contains silicon carbide, silicon and a calcination aid, and the calcination aid contains aluminum oxide, silicon oxide and strontium oxide. When the total mass of aluminum oxide, silicon oxide, and strontium oxide per 100 pts.mass of silicon carbide and silicon in the partition wall is T1, and the pts.mass of aluminum oxide to 100 pts.mass of silicon carbide and silicon in the partition wall is A1, it satisfies 0.045≤A1 / T1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a honeycomb structure, and also to a raw material composition for forming a honeycomb structure and a method for producing a porous body using the same. [Background technology]

[0002] Silicon carbide (SiC) is used in a variety of ceramic products, such as heat sinks, exhaust gas filters, catalyst carriers, sliding parts, nozzles, heat exchangers, and semiconductor manufacturing equipment parts, taking advantage of its properties such as high heat resistance, high hardness, excellent chemical resistance, and excellent wear resistance. In particular, silicon-silicon carbide composites, which have excellent heat resistance, thermal shock resistance, and oxidation resistance, are known as a typical constituent material for honeycomb structures used in filters (e.g., DPFs) that capture fine particles in exhaust gases from internal combustion engines and boilers, and catalyst carriers for exhaust gas purification catalysts.

[0003] Honeycomb structures containing silicon-silicon carbide composites are manufactured, for example, by adding silicon (Si), a pore-forming agent, and a firing aid to silicon carbide powder, kneading the mixture, extruding the resulting clay into a honeycomb molded body using a specified die, and firing the resulting honeycomb molded body. Known firing aids include aluminum oxide (Al2O3), silicon oxide (SiO2), and alkaline earth metal oxides (oxides of Mg, Ca, Sr, and Ba). The addition of these firing aids improves the wetting of silicon (Si) with silicon carbide during melting, thereby increasing the bonding strength (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6043340 [Patent Document 2] International Publication No. 2012 / 132837 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, DPFs and catalyst carriers have become larger in size and have increasingly complex cell structures. Furthermore, the environments in which DPFs and catalyst carriers are used have become increasingly harsh. Therefore, honeycomb structures used in these applications are required to have improved thermal shock resistance. Suppressing the thermal expansion of honeycomb structures is known to be one effective means of improving thermal shock resistance, and it is desirable to develop new technologies that can suppress the thermal expansion of honeycomb structures.

[0006] In view of the above circumstances, an object of the present invention is to provide, in one embodiment, a honeycomb structure containing a silicon-silicon carbide composite material capable of suppressing thermal expansion. Also, an object of the present invention is to provide, in another embodiment, a forming material composition suitable for producing such a honeycomb structure and a method for producing a porous body. [Means for solving the problem]

[0007] The present inventors conducted extensive research to solve the above problems and found that adding aluminum oxide, silicon oxide, and strontium oxide as firing aids under certain conditions can produce a honeycomb structure containing a silicon-silicon carbide composite material with significantly suppressed thermal expansion. Suppressing thermal expansion reduces thermal stress, making it possible to improve the thermal shock resistance of the honeycomb structure. The present invention, which was completed based on this finding, is exemplified below.

[0008] [Aspect 1] A honeycomb structure having partition walls that define a plurality of cells extending from one end face to the other end face, the partition walls contain silicon carbide, silicon, and a firing aid; the firing aid contains aluminum oxide, silicon oxide, and strontium oxide, and satisfies 0.045≦A1 / T1, where T1 is the total part by mass of the aluminum oxide, silicon oxide, and strontium oxide relative to 100 parts by mass of the silicon carbide and silicon in the partition walls, and A1 is the part by mass of the aluminum oxide relative to 100 parts by mass of the silicon carbide and silicon in the partition walls. Honeycomb structure. [Aspect 2] 2. The honeycomb structure according to claim 1, wherein 0.045≦A1 / T1≦0.200 is satisfied. [Aspect 3] A honeycomb structure according to aspect 1 or 2, wherein B1 is the part by mass of silicon oxide relative to 100 parts by mass of the total of silicon carbide and silicon in the partition walls, and B1 / T1 satisfies 0.70≦B1 / T1≦0.90. [Aspect 4] A honeycomb structure according to any one of aspects 1 to 3, wherein C1 is the part by mass of strontium oxide relative to 100 parts by mass of the total of silicon carbide and silicon in the partition walls, and C1 / T1 satisfies 0.050≦C1 / T1≦0.200. [Aspect 5] 5. The honeycomb structure according to any one of aspects 1 to 4, wherein 10≦T1≦40 is satisfied. [Aspect 6] A honeycomb structure according to any one of aspects 1 to 5, wherein D1 is the part by mass of silicon carbide relative to 100 parts by mass of the total of silicon carbide and silicon in the partition walls, and D1 satisfies 70≦D1≦95. [Aspect 7] 7. A honeycomb structure according to any one of aspects 1 to 6, wherein the total mass concentration of silicon carbide and silicon in the partition walls satisfies 60≦E1≦95, where E1 is mass %. [Aspect 8] 8. The honeycomb structure according to any one of aspects 1 to 7, wherein the partition walls contain sepiolite. [Aspect 9] A honeycomb structure according to any one of Aspects 1 to 8, wherein F1 is the part by mass of sepiolite relative to 100 parts by mass of the total of silicon carbide and silicon, and satisfies 0.5≦F1≦5.0. [Aspect 10] 9. The honeycomb structure according to any one of aspects 1 to 8, wherein the partition walls have a porosity of 40% or more. [Aspect 11] 11. The honeycomb structure according to any one of aspects 1 to 10, further comprising plugging portions disposed at openings of predetermined cells on the one end face and at openings of remaining cells on the other end face. [Aspect 12] The average linear expansion coefficient measured according to JIS R1618:2002 when changing from 40°C to 800°C is 5.5 x 10 -6 12. The honeycomb structure according to any one of aspects 1 to 11, wherein the tensile strength is 1 / K or less. [Aspect 13] 13. The honeycomb structure according to any one of aspects 1 to 12, wherein the thermal conductivity measured at 50° C. according to the method of ASTM E1530 is 3.0 W / (m·K) or more. [Aspect 14] A molding raw material composition containing silicon carbide, silicon, a pore-forming material, and a sintering aid, The sintering aid contains aluminum oxide, silicon oxide, and strontium oxide, and the molding raw material composition satisfies 0.20≦A2 / T2, where T2 is the total parts by mass of aluminum oxide, silicon oxide, and strontium oxide per 100 parts by mass of silicon carbide and silicon, and A2 is the total parts by mass of aluminum oxide per 100 parts by mass of silicon carbide and silicon. [Aspect 15] 15. The molding raw material composition according to embodiment 14, wherein 0.20≦A2 / T2≦0.60 is satisfied. [Aspect 16] Aspect 16. The molding raw material composition according to aspect 14 or 15, wherein B2 is the part by mass of silicon oxide relative to 100 parts by mass of the total of silicon carbide and silicon, and satisfies 0.20≦B2 / T2≦0.60. [Aspect 17] 17. The molding raw material composition according to any one of aspects 14 to 16, wherein C2 is the part by mass of strontium oxide per 100 parts by mass of the total of silicon carbide and silicon, and satisfies 0.10≦C2 / T2≦0.50. [Aspect 18] 18. The molding raw material composition according to any one of aspects 14 to 17, wherein 1.0≦T2≦10.0 is satisfied. [Aspect 19] 19. The molding raw material composition according to any one of aspects 14 to 18, wherein D2 is the part by mass of silicon carbide relative to 100 parts by mass of the total of silicon carbide and silicon, and satisfies 70≦D2≦95. [Aspect 20] 20. The molding raw material composition according to any one of aspects 14 to 19, which contains sepiolite. [Aspect 21] Aspect 21. The molding raw material composition according to aspect 20, wherein F2 is the part by mass of sepiolite relative to 100 parts by mass of the total of silicon carbide and silicon, and satisfies 0.50≦F2≦5.0. [Aspect 22] 22. The molding raw material composition according to any one of aspects 14 to 21, wherein, when the parts by mass of the pore-forming material per 100 parts by mass of silicon carbide and silicon are taken as G2, the relationship 1.0≦G2≦30.0 is satisfied. [Aspect 23] a molding step of extruding the molding raw material composition according to any one of aspects 14 to 22 to produce a molded body; A firing step of firing the molded body to produce a porous body, Method for producing porous bodies. [Aspect 24] Aspect 24. The method for producing a porous body according to aspect 23, wherein the molded body has partition walls that define a plurality of cells extending from one end face to the other end face. [Effects of the Invention]

[0009] According to one embodiment of the present invention, it is possible to provide a honeycomb structure containing a silicon-silicon carbide composite material capable of suppressing thermal expansion. There is a growing market need for honeycomb structures containing a silicon-silicon carbide composite material with improved thermal shock resistance, and this honeycomb structure can meet such market needs. Furthermore, according to another embodiment, it is possible to provide a forming material composition and a method for manufacturing a porous body suitable for manufacturing such a honeycomb structure. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view schematically showing a wall-through type honeycomb structure. [Figure 2] FIG. 2 is a schematic cross-sectional view of a wall-through honeycomb structure observed in a cross section parallel to the cell extension direction. [Figure 3] FIG. 1 is a perspective view schematically showing a wall-flow type pillar-shaped honeycomb structure. [Figure 4] 1 is a schematic cross-sectional view of a wall-flow type pillar-shaped honeycomb structure when observed from a cross section parallel to the cell extension direction. FIG. [Figure 5] 1A and 1B are a schematic end view and a side view of a honeycomb structure provided as a segment bonded body. DETAILED DESCRIPTION OF THE INVENTION

[0011] While the following describes specific embodiments of the present invention, the present invention should not be construed as being limited thereto, and various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the gist of the present invention. The multiple components disclosed in each embodiment can be appropriately combined to form various inventions. For example, some components may be omitted from all the components shown in the embodiments, or components from different embodiments may be appropriately combined.

[0012] (1. Honeycomb structure) A honeycomb structure according to one embodiment of the present invention includes partition walls that define a plurality of cells extending from one end face to the other end face. In one embodiment, the honeycomb structure is provided as a wall-through honeycomb structure in which both one end face and the other end face of a plurality of cells have openings. In another embodiment, the honeycomb structure is provided as a wall-flow honeycomb structure in which plugging portions are disposed in the openings of predetermined cells at one end face and the openings of the remaining cells at the other end face. The honeycomb structure is not particularly limited in its applications. For example, the honeycomb structure is used in various industrial applications such as heat sinks, filters (e.g., GPFs and DPFs), catalyst carriers, sliding parts, nozzles, heat exchangers, electrical insulating members, and semiconductor manufacturing equipment parts. In particular, the honeycomb structure is suitable for use as a filter for capturing particulate matter contained in exhaust gas from internal combustion engines, boilers, etc., and as a catalyst carrier for exhaust gas purification catalysts. In particular, the honeycomb structure is suitable for use as an exhaust gas filter and / or catalyst carrier for automobiles.

[0013] 1 and 2 show a schematic perspective view and a cross-sectional view, respectively, of a wall-through honeycomb structure 100. The honeycomb structure 100 includes an outer peripheral sidewall 102 and partition walls 112 disposed on the inner circumferential side of the outer peripheral sidewall 102. The partition walls 112 define a plurality of cells 108, each of which defines a fluid flow path (cell channel) from a first end face 104 to a second end face 106. In the honeycomb structure 100, both ends of each cell 108 are open. Exhaust gas that flows into one cell 108 from the first end face 104 is purified while passing through the cell and then flows out from the second end face 106. Note that, although the first end face 104 is defined as the upstream side of the exhaust gas and the second end face 106 is defined as the downstream side of the exhaust gas, the distinction between the first end face and the second end face is for convenience's sake. Alternatively, the second end face 106 may be defined as the upstream side of the exhaust gas and the first end face 104 as the downstream side of the exhaust gas.

[0014] 3 and 4 are a schematic perspective view and a cross-sectional view, respectively, of a wall-flow type honeycomb structure 200. This honeycomb structure 200 includes an outer peripheral side wall 202 and partition walls 212 disposed on the inner peripheral side of the outer peripheral side wall 202 and partitioning a plurality of cells 208a, 208b that form fluid flow paths (cell channels) from a first end face 204 to a second end face 206. In the honeycomb structure 200, the plurality of cells 208a, 208b can be classified into a plurality of first cells 208a that are disposed on the inner peripheral side of the outer peripheral side wall 202, extend from a first end face 204 to a second end face 206, have plugging portions 209 at the first end face 204, and have plugging portions 209 at the second end face 206, and a plurality of second cells 208b that are disposed on the inner peripheral side of the outer peripheral side wall 202, extend from the first end face 204 to the second end face 206, have plugging portions 209 at the first end face 204, and are open at the second end face 206. In this honeycomb structure 200, the first cells 208a and the second cells 208b are disposed adjacent to each other alternately with partition walls 212 sandwiched therebetween.

[0015] When exhaust gas containing particulate matter such as soot is supplied to the first end face 204 on the upstream side of the honeycomb structure 200, the exhaust gas is introduced into the first cells 208a and travels downstream within the first cells 208a. Because the first cells 208a have plugging portions 209 on the second end face 206 on the downstream side, the exhaust gas passes through the partition walls 212 that separate the first cells 208a and the second cells 208b and flows into the second cells 208b. Since the particulate matter cannot pass through the partition walls 212, it is captured and deposited within the first cells 208a. After the particulate matter is removed, the clean exhaust gas that has flowed into the second cells 208b travels downstream within the second cells 208b and flows out from the second end face 206 on the downstream side. Here, the first end face 204 is on the upstream side of the exhaust gas and the second end face 206 is on the downstream side of the exhaust gas, but the distinction between the first end face and the second end face is for convenience, and the second end face 206 may be on the upstream side of the exhaust gas and the first end face 204 may be on the downstream side of the exhaust gas.

[0016] The end face shape of the honeycomb structure is not limited, and may be, for example, a circular shape, an elliptical shape, a racetrack shape, an oval shape, or other round shape, a polygonal shape such as a triangular shape or a square shape, or other irregular shapes. The honeycomb structure shown in the figure has a circular end face shape and is cylindrical as a whole.

[0017] There are no particular restrictions on the height of the honeycomb structure (the length from the first end face to the second end face) and it may be set appropriately depending on the application and required performance. The height of the honeycomb structure may be, for example, 40 mm to 450 mm. There are also no particular restrictions on the relationship between the height of the honeycomb structure and the maximum diameter of each end face (the maximum length of the diameters passing through the center of gravity of each end face of the honeycomb structure). Therefore, the height of the honeycomb structure may be longer than the maximum diameter of each end face, or the height of the honeycomb structure may be shorter than the maximum diameter of each end face.

[0018] The area of ​​each end face of the honeycomb structure is not particularly limited, but is, for example, 6200 to 93000 mm 2 Typically, the thickness is 16,200 to 73,000 mm. 2 It can be said that:

[0019] The honeycomb structure can be provided as an integrally molded product. Alternatively, as shown in Fig. 5, the honeycomb structures 100 and 200 can be provided as a bonded segment body by preparing a plurality of columnar honeycomb structures as segments 110 and bonding the outer peripheral side walls of the plurality of segments 110 together via a bonding material 117. By providing the honeycomb structure as a bonded segment body, the thermal shock resistance can be improved.

[0020] Although there are no limitations on the shape of the cells in a cross section perpendicular to the cell extension direction, a square, a hexagon, an octagon, or a combination thereof is preferred. Among these, a square and a hexagon are preferred. By using such a cell shape, the pressure loss when exhaust gas flows through the honeycomb structure is reduced, and the purification performance of the catalyst is improved. From the viewpoint of increasing the structural strength, a square is particularly preferred.

[0021] The partition walls (typically the partition walls and the outer peripheral side wall) contain silicon carbide and silicon. That is, the partition walls (typically the partition walls and the outer peripheral side wall) contain a silicon-silicon carbide composite. 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 between the silicon carbide particles. The partition walls (typically the partition walls and the outer peripheral side wall) contain a silicon-silicon carbide composite, which is advantageous for improving the heat resistance, thermal shock resistance, and oxidation resistance of the honeycomb structure. When the total mass concentration of silicon carbide and silicon in the partition walls (typically the partition walls and the outer peripheral side wall) is E1 mass%, it is preferable that 60≦E1≦95 is satisfied, and more preferably 70≦E1≦92.5 is satisfied. E1 of 60 or more is advantageous in terms of strength. An E1 of 95 or less is advantageous in terms of ease of production.

[0022] When the partition walls (typically the partition walls and the outer peripheral side wall) contain a silicon-silicon carbide composite, when the parts by mass of silicon carbide per 100 parts by mass of silicon carbide and silicon in the partition walls (typically the partition walls and the outer peripheral side wall) is D1, it is preferable that D1 satisfies 70≦D1≦95, and more preferably 75≦D1≦92.5. D1 of 70 or more is advantageous from the viewpoint of strength. D1 of 95 or less is advantageous from the viewpoint of strength and thermal conductivity.

[0023] Furthermore, the partition walls (typically the partition walls and the outer peripheral side wall) contain aluminum oxide, silicon oxide, and strontium oxide as firing aids. The inclusion of aluminum oxide, silicon oxide, and strontium oxide as firing aids is advantageous in terms of promoting melting of silicon. When the total mass parts of aluminum oxide, silicon oxide, and strontium oxide per 100 mass parts of silicon carbide and silicon in the partition walls (typically the partition walls and the outer peripheral side wall) is T1, and the mass parts of aluminum oxide per 100 mass parts of silicon carbide and silicon in the partition walls (typically the partition walls and the outer peripheral side wall) is A1, the thermal expansion of the honeycomb structure can be significantly suppressed by satisfying 0.045≦A1 / T1.

[0024] From the viewpoint of suppressing thermal expansion of the honeycomb structure, the partition walls (typically the partition walls and the peripheral side walls) preferably satisfy 0.050≦A1 / T1, and more preferably satisfy 0.055≦A1 / T1. On the other hand, from the viewpoint of increasing the thermal conductivity of the honeycomb structure, the partition walls (typically the partition walls and the peripheral side walls) preferably satisfy A1 / T1≦0.200, more preferably satisfy A1 / T1≦0.175, and even more preferably satisfy A1 / T1≦0.150. Increasing the thermal conductivity of the honeycomb structure is advantageous in terms of thermal shock resistance, since it suppresses the occurrence of temperature differences within the structure.

[0025] Therefore, in order to suppress the thermal expansion of the honeycomb structure and increase the thermal conductivity, it is preferable that the partition walls (typically the partition walls and the outer peripheral side walls) satisfy, for example, 0.045≦A1 / T1≦0.200, it is more preferable that they satisfy 0.050≦A1 / T1≦0.175, and it is even more preferable that they satisfy 0.055≦A1 / T1≦0.150.

[0026] When the partition walls (typically the partition walls and the outer peripheral side wall) contain aluminum oxide, silicon oxide, and strontium oxide as firing aids, when the total parts by mass of aluminum oxide, silicon oxide, and strontium oxide relative to 100 parts by mass of silicon carbide and silicon in the partition walls (typically the partition walls and the outer peripheral side wall) is T1, and the parts by mass of silicon oxide relative to 100 parts by mass of silicon carbide and silicon in the partition walls (typically the partition walls and the outer peripheral side wall) is B1, it is preferable to satisfy 0.70≦B1 / T1≦0.90, more preferably satisfy 0.725≦B1 / T1≦0.875, and even more preferably satisfy 0.75≦B1 / T1≦0.85. Setting B1 / T1 in this range provides the advantages of easy melting of silicon, which is advantageous for strength and thermal conductivity.

[0027] When the partition walls (typically the partition walls and the outer peripheral side wall) contain aluminum oxide, silicon oxide, and strontium oxide as firing aids, when the total parts by mass of aluminum oxide, silicon oxide, and strontium oxide relative to 100 parts by mass of silicon carbide and silicon in the partition walls (typically the partition walls and the outer peripheral side wall) is T1, and the parts by mass of strontium oxide relative to 100 parts by mass of silicon carbide and silicon in the partition walls (typically the partition walls and the outer peripheral side wall) is C1, it is preferable to satisfy 0.050≦C1 / T1≦0.200, more preferably satisfy 0.060≦C1 / T1≦0.190, and even more preferably satisfy 0.070≦C1 / T1≦0.180. Setting C1 / T1 in this range provides the advantages of easy melting of silicon, which is advantageous for strength and thermal conductivity.

[0028] When the partition walls (typically, the partition walls and the outer peripheral side wall) contain aluminum oxide, silicon oxide, and strontium oxide as firing aids, when the total parts by mass of aluminum oxide, silicon oxide, and strontium oxide relative to 100 parts by mass of silicon carbide and silicon in the partition walls (typically, the partition walls and the outer peripheral side wall) is T1, it is preferable that T1 satisfies 10 ≦ T1 ≦ 40, more preferably satisfies 12.5 ≦ T1 ≦ 35, and even more preferably satisfies 15 ≦ T1 ≦ 30. Setting T1 in this range provides the advantage of ease of production.

[0029] From the viewpoint of suppressing an increase in pressure loss, the lower limit of the porosity of the partition walls (typically the partition walls and the peripheral side wall) measured by mercury porosimetry is preferably 40% or more, more preferably 45% or more, and even more preferably 50% or more. Furthermore, from the viewpoint of ensuring strength, the upper limit of the porosity of the partition walls (typically the partition walls and the peripheral side wall) measured by mercury porosimetry is preferably 80% or less, more preferably 70% or less, and even more preferably 65% ​​or less. Therefore, the porosity of the partition walls (typically the partition walls and the peripheral side wall) measured by mercury porosimetry is, for example, preferably 40 to 80%, more preferably 45 to 70%, and even more preferably 50 to 65%. In this specification, "porosity" is measured by the mercury porosimetry specified in JIS R1655:2003. Furthermore, the porosity of the partition walls and the peripheral side wall is the average value measured when samples are taken from multiple locations on the honeycomb structure.

[0030] It is desirable that the thermal expansion of the honeycomb structure be small. Specifically, the average linear expansion coefficient measured according to JIS R1618:2002 when the temperature is changed from 40°C to 800°C is 5.5 × 10 -6 / K or less. -6 / K or less, the thermal stress during exhaust gas treatment and filter regeneration, when the temperature of the honeycomb structure becomes high, is reduced, and the thermal shock resistance is significantly improved. -6 / K or less is more preferable, and 5.3 × 10 -6 Although there is no particular restriction on the lower limit of the average linear expansion coefficient, from the viewpoint of ease of production, the average linear expansion coefficient is preferably 3.0×10 -6 / K or more is preferable, and 3.5 × 10 -6 / K or more is more preferable, and 4.0 × 10 -6 Therefore, the average linear expansion coefficient is, for example, 3.0×10 -6 / K or more 5.5×10 -6 / K or less, and 3.5 × 10-6 / K or more 5.4×10 -6 / K or less is more preferable, and 4.0 × 10 -6 / K or more 5.3×10 -6 It is even more preferable that the .beta..times ...

[0031] The average linear expansion coefficient of the honeycomb structure is measured by the following procedure: A rectangular columnar sample measuring 3 mm × 3 mm × 15 mm (length in the cell extension direction) is cut out from the center of the honeycomb structure in the radial and height directions, and the average linear expansion coefficient of the sample is measured under the above-mentioned temperature change conditions, and this is taken as the measured value.

[0032] Furthermore, it is desirable for the honeycomb structure to have high thermal conductivity. Specifically, the thermal conductivity measured at 50°C according to the ASTM E1530 method is preferably 3.0 W / (m·K) or more. A thermal conductivity of 3.0 W / (m·K) or more suppresses temperature differences within the structure, improving thermal shock resistance. Furthermore, the removal performance when PM trapped in the honeycomb structure is burned and removed for filter regeneration can be improved. The thermal conductivity is more preferably 3.3 W / (m·K) or more, and even more preferably 3.6 W / (m·K) or more. While there is no particular upper limit to the thermal conductivity, from the viewpoint of ease of manufacture, the thermal conductivity is preferably 35.0 W / (m·K) or less, more preferably 30.0 W / (m·K) or less, and even more preferably 25.0 W / (m·K) or less. Therefore, the thermal conductivity is, for example, preferably 3.0 W / (m·K) or more and 35.0 W / (m·K) or less, more preferably 3.3 W / (m·K) or more and 30.0 W / (m·K) or less, and even more preferably 3.6 W / (m·K) or more and 25.0 W / (m·K) or less.

[0033] The thermal conductivity of the honeycomb structure is measured by the following procedure: A rectangular columnar sample measuring 35 mm × 35 mm × 20 mm (length in the cell extension direction) is cut out from the center of the honeycomb structure in the radial and vertical directions, and the thermal conductivity of the sample is measured under the above-mentioned temperature conditions using a steady-state thermal conductivity measuring device conforming to ASTM E1530, and the measured value is used.

[0034] The cell density of the honeycomb structure (the number of cells per unit cross-sectional area perpendicular to the cell extension direction) is not particularly limited, but is preferably 98 to 497 cells / square inch (15 to 77 cells / cm). 2 ), more preferably 129 to 400 cells / in² (20 to 62 cells / cm²) 2 ), and particularly preferably 148 to 348 cells / square inch (23 to 54 cells / cm 2 Here, the cell density is calculated by dividing the total number of cells in one end face (if plugged cells exist, the calculation is performed assuming that the cells are not plugged) by the area of ​​the end face excluding the peripheral side wall of the honeycomb structure.

[0035] The upper limit of the average thickness of the partition walls in the honeycomb structure is preferably 500 μm or less, more preferably 400 μm or less, and even more preferably 300 μm or less, from the viewpoint of pressure loss. The lower limit of the average thickness of the partition walls in the honeycomb structure is preferably 100 μm or more, more preferably 125 μm or more, and even more preferably 150 μm or more, from the viewpoint of strength. Therefore, the average thickness of the partition walls in the honeycomb structure is, for example, preferably 100 to 500 μm, more preferably 125 to 400 μm, and even more preferably 150 to 300 μm. The thickness of the partition walls refers to the length of a line segment that intersects the partition walls when the line segment connects the centers of gravity of adjacent cells in a cross section perpendicular to the cell extension direction (height direction of the honeycomb structure). The average thickness of the partition walls is calculated based on the thickness of all the partition walls.

[0036] Although quantitative determination is difficult, it is preferable that the partition walls (typically the partition walls and peripheral side walls) in the honeycomb structure contain one or both of sepiolite and montmorillonite added to the forming raw material composition as inorganic binders, and it is more preferable that sepiolite is contained.

[0037] (2. Molding raw material composition) According to one embodiment of the present invention, there is provided a forming raw material composition that can be suitably used for manufacturing a porous body such as the above-mentioned honeycomb structure. In one embodiment, the forming raw material composition contains silicon carbide, silicon, a pore-forming agent, and a sintering aid.

[0038] The raw materials such as silicon carbide, silicon, a pore-forming agent, and a firing aid can be provided in the form of, for example, powder, and the molding raw material composition can be provided as, for example, a slurry in which these raw materials are dispersed in a dispersion medium.

[0039] When silicon carbide is in powder form, the median diameter (D50) of the silicon carbide particles constituting the silicon carbide powder is preferably 5 μm or more, more preferably 7.5 μm or more, and even more preferably 10 μm or more, from the viewpoint of reducing pressure loss. Furthermore, the median diameter (D50) of the silicon carbide particles constituting the silicon carbide powder is preferably 60 μm or less, more preferably 55 μm or less, and even more preferably 50 μm or less, from the viewpoint of improving the filtering performance. Therefore, the median diameter (D50) of the silicon carbide particles constituting the silicon carbide powder is, for example, preferably 5 to 60 μm, more preferably 7.5 to 55 μm, and even more preferably 10 to 50 μm. In this specification, the median diameter (D50) of the silicon carbide particles refers to the 50% diameter when the cumulative particle size distribution of the silicon carbide powder on a volume basis is measured by a laser diffraction / scattering method.

[0040] When silicon is in powder form, the median diameter (D50) of the silicon particles constituting the silicon powder is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less, from the viewpoint of increasing the strength of the porous body. Since finer silicon particles are preferable, there is no particular lower limit for the median diameter (D50). However, from the viewpoint of ease of availability, the median diameter (D50) of the silicon particles is usually 1 μm or more. Therefore, the median diameter (D50) of the silicon particles constituting the silicon powder is preferably, for example, 1 to 20 μm, more preferably 1 to 15 μm, and even more preferably 1 to 10 μm. In this specification, the median diameter (D50) of the silicon particles refers to the 50% diameter when the cumulative particle size distribution of the silicon powder on a volume basis is measured by a laser diffraction / scattering method.

[0041] The inclusion of silicon carbide and silicon in the molding raw material composition is advantageous in improving the heat resistance, thermal shock resistance, and oxidation resistance of the porous body. When the parts by mass of silicon carbide per 100 parts by mass of the total of silicon carbide and silicon contained in the molding raw material composition is defined as D2, it is preferable that D2 satisfies 70≦D2≦95, and more preferably 72.5≦D2≦90. Having D2 of 70 or more is advantageous in terms of strength. Having D2 of 95 or less is advantageous in terms of strength and thermal conductivity.

[0042] When the pore-forming material is in powder form, the median diameter (D50) of the pore-forming material particles constituting the pore-forming material powder is preferably 70 μm or less, more preferably 65 μm or less, and even more preferably 60 μm or less, from the viewpoint of PM collection performance. The median diameter (D50) of the pore-forming material particles constituting the pore-forming material powder is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 7.5 μm or more, from the viewpoint of pressure loss. Therefore, the median diameter (D50) of the pore-forming material particles constituting the pore-forming material powder is, for example, preferably 3 to 70 μm, more preferably 5 to 65 μm, and even more preferably 7.5 to 60 μm. In this specification, the median diameter (D50) of the pore-forming material particles refers to the 50% diameter when the cumulative particle size distribution of the pore-forming material powder on a volume basis is measured by a laser diffraction / scattering method.

[0043] When the sintering aid is in powder form, the median diameter (D50) of the sintering aid particles constituting the sintering aid powder is preferably 0.1 μm or more and 10 μm or less from the viewpoint of uniform powder mixing. In this specification, the median diameter (D50) of the sintering aid particles refers to the 50% diameter when the cumulative particle size distribution on a volume basis of the sintering aid powder is measured by a laser diffraction / scattering method.

[0044] In one embodiment, the sintering aid contains aluminum oxide, silicon oxide, and strontium oxide. The sintering aid containing aluminum oxide, silicon oxide, and strontium oxide is advantageous in terms of the ease of melting silicon.

[0045] If the total parts by mass of aluminum oxide, silicon oxide, and strontium oxide per 100 parts by mass of silicon carbide and silicon contained in the forming material composition is T2, and the parts by mass of aluminum oxide per 100 parts by mass of silicon carbide and silicon contained in the forming material composition is A2, from the viewpoint of obtaining a porous body with suppressed thermal expansion, it is preferable to satisfy 0.20≦A2 / T2, more preferably to satisfy 0.225≦A2 / T2, and even more preferably to satisfy 0.25≦A2 / T2. On the other hand, from the viewpoint of obtaining a porous body with improved thermal conductivity, the forming material composition preferably satisfies A2 / T2≦0.70, more preferably to satisfy A2 / T2≦0.65, and even more preferably to satisfy A2 / T2≦0.60. Therefore, the molding raw material composition preferably satisfies, for example, 0.20≦A2 / T2≦0.70, more preferably 0.225≦A2 / T2≦0.65, and even more preferably 0.25≦A2 / T2≦0.60.

[0046] If the total parts by mass of aluminum oxide, silicon oxide, and strontium oxide per 100 parts by mass of silicon carbide and silicon contained in the forming raw material composition is T2, and the parts by mass of silicon oxide per 100 parts by mass of silicon carbide and silicon contained in the forming raw material composition is B2, it is preferable to satisfy 0.20≦B2 / T2≦0.60, more preferably to satisfy 0.25≦B2 / T2≦0.575, and even more preferably to satisfy 0.30≦B2 / T2≦0.55. Setting B2 / T2 in this range has the advantage that silicon is easily melted and strength is obtained.

[0047] If the total parts by mass of aluminum oxide, silicon oxide, and strontium oxide per 100 parts by mass of silicon carbide and silicon contained in the forming raw material composition is T2, and the parts by mass of strontium oxide per 100 parts by mass of silicon carbide and silicon contained in the forming raw material composition is C2, it is preferable to satisfy 0.10≦C2 / T2≦0.50, more preferably to satisfy 0.125≦C2 / T2≦0.45, and even more preferably to satisfy 0.15≦C2 / T2≦0.40. Setting C2 / T2 in this range has the advantage that silicon is easily melted and strength is obtained.

[0048] If the total parts by mass of aluminum oxide, silicon oxide, and strontium oxide per 100 parts by mass of silicon carbide and silicon contained in the molding raw material composition is T2, then it is preferable to satisfy 1.0≦T2≦10.0, more preferably 1.5≦T2≦9.0, and even more preferably 2.0≦T2≦8.0. Setting T2 within this range provides the advantage that silicon is easily melted and strength is obtained.

[0049] If the parts by mass of the pore-forming material per 100 parts by mass of the silicon carbide and silicon contained in the molding raw material composition is defined as G2, then it is preferable that 1.0≦G2≦30.0 is satisfied, more preferably 2.0≦G2≦28.0 is satisfied, and even more preferably 3.0≦G2≦26.0 is satisfied. By setting G2 within this range, it is possible to obtain the advantage of excellent PM collection performance and pressure loss. Examples of pore-forming materials include, but are not limited to, graphite, foamed resin, wheat flour, starch, phenolic resin, polymethyl methacrylate, polyethylene, polymethacrylate, polyethylene terephthalate, etc. One type of pore-forming material may be used alone, or two or more types may be used in combination.

[0050] The molding raw material composition preferably contains a binder. Examples of binders include both organic and inorganic binders, with organic binders being more preferred for ease of molding and inorganic binders being more preferred for achieving the strength of the structure after firing. Examples of inorganic binders include, but are not limited to, magnesium silicate minerals having a 2:1 ribbon structure, smectite, alumina sol, silica sol, boehmite, gamma alumina, and attapulgite. One type of inorganic binder may be used alone, or two or more types may be used in combination. Among these, it is preferable to contain one or both of sepiolite and montmorillonite, and sepiolite is more preferable, because it increases the strength of the molded body when the organic binder is burned off. Examples of organic binders include, but are not limited to, methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, and the like. One type of organic binder may be used alone, or two or more types may be used in combination.

[0051] From the viewpoint of increasing the strength of the compact when the organic binder is burned off, the content of the inorganic binder in the molding raw material composition is preferably 0.5 to 10.0 parts by mass, more preferably 1.0 to 8.0 parts by mass, and even more preferably 1.5 to 6.0 parts by mass, relative to 100 parts by mass of the total of silicon carbide and silicon. For example, if F2 is the part by mass of sepiolite relative to 100 parts by mass of the total of silicon carbide and silicon, it is preferable that 0.50≦F2≦5.0 is satisfied, more preferably 1.0≦F2≦4.25 is satisfied, and even more preferably 1.5≦F2≦4.0 is satisfied.

[0052] The content of the organic binder in the molding raw material composition is preferably 3.0 to 9.0 parts by mass, more preferably 4.0 to 8.0 parts by mass, and even more preferably 5.0 to 7.0 parts by mass, per 100 parts by mass of the total of silicon carbide and silicon, from the viewpoints of improving the shape retention ability of the molded body, suppressing the occurrence of cracks due to abnormal heat generation during firing, and suppressing deformation by reducing the amount of drying shrinkage of the molded body.

[0053] The molding raw material composition preferably contains a dispersion medium. Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as an alcohol, with water being particularly preferred. From the viewpoints of improving quality stability during molding and suppressing deformation by reducing the drying shrinkage of the molded body, the content of the dispersion medium in the molding raw material composition is preferably 20 to 60 parts by mass, more preferably 25 to 55 parts by mass, and even more preferably 30 to 50 parts by mass, per 100 parts by mass of silicon carbide and silicon combined. In this specification, the content of the dispersion medium in the molding raw material composition refers to a value measured by a loss on drying method.

[0054] If necessary, the molding raw material composition may contain a surfactant. Examples of surfactants that can be used include ethylene glycol, dextrin, fatty acid soap, and polyether polyol. These surfactants may be used alone or in combination of two or more. When a surfactant is added to the molding raw material composition, the content may be, for example, 0.01 to 1.0 parts by mass per 100 parts by mass of the total of silicon carbide and silicon.

[0055] (3. Method for producing porous body) According to one embodiment of the present invention, there is provided a manufacturing method that can be suitably used for manufacturing a porous body such as the above-mentioned honeycomb structure. In one embodiment, the manufacturing method includes a molding step of extruding the above-mentioned molding raw material composition to produce a molded body, and a firing step of firing the molded body to produce a porous body. In one embodiment, the molded body has partition walls that define a plurality of cells extending from one end face to the other end face. Below, an exemplary method for manufacturing a honeycomb structure will be described in detail.

[0056] First, the above-mentioned molding raw material composition is kneaded to form a puddle, and then the puddle is extruded through a die that defines the opening shape of multiple cells to produce a honeycomb molded body having an outer side wall and a honeycomb molded body that is arranged on the inner side of the outer side wall, extends from a first end face to a second end face, and has openings on both the first end face and the second end face.

[0057] The kneading method of the forming raw material composition is not particularly limited, and can be performed by a method known in the art. For example, the kneading of the forming raw material composition can be performed using a kneader, a vacuum kneader, or the like. The desired honeycomb formed body, typically a cylindrical honeycomb formed body, is produced by molding the clay. Extrusion molding is preferably used as the molding method. During extrusion molding, by using a die having the desired overall shape, cell shape, partition wall thickness, cell density, etc., it is possible to produce a honeycomb formed body having partition walls that define a plurality of cells extending from one end face to the other end face.

[0058] The honeycomb molded body may be dried before firing. The drying method is not particularly limited, and hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying, etc. can be used. Among these, it is preferable to use dielectric drying, microwave drying, or hot air drying alone or in combination. Furthermore, the drying conditions are not particularly limited, but it is preferable to use a drying temperature of 30 to 150°C and a drying time of 1 minute to 2 hours. In this specification, the "drying temperature" means the temperature of the atmosphere in which drying is performed.

[0059] When manufacturing a honeycomb structure having plugging portions, the openings of predetermined cells of a honeycomb formed body or a dried body obtained by drying the formed body are plugged with a plugging material. As a method for plugging the openings of the cells, a method of filling the openings of the cells with a plugging material may be used. The method of filling the plugging material may be performed in accordance with a conventionally known method for manufacturing a honeycomb structure having plugging portions. As the plugging portion forming raw material for forming the plugging portions, a plugging portion forming raw material used in a conventionally known method for manufacturing a honeycomb structure may be used.

[0060] After drying the honeycomb formed body, a firing process is carried out to manufacture a honeycomb structure. A degreasing process for burning and removing the organic binder may be carried out before firing. The conditions for the degreasing process and the firing process may be well-known conditions depending on the material composition of the honeycomb formed body, and no particular explanation is required, but specific examples of conditions are given below.

[0061] The degreasing step will now be described. The combustion temperature of the organic binder is about 200°C, and the combustion temperature of the pore-forming material is about 300 to 600°C. Therefore, the degreasing step can be carried out by heating the honeycomb formed body to a temperature range of about 200 to 1000°C. The heating time is not particularly limited, but is usually about 3 to 10 hours. The honeycomb formed body after the degreasing step is called a calcined body.

[0062] The debinding process may be performed in an oxidizing atmosphere. However, if the compact contains a large amount of organic binder, the organic binder may burn violently with oxygen during calcination, causing the compact temperature to rise sharply. Therefore, the process may be performed in an inert atmosphere such as N2 or Ar to prevent abnormal temperature rise of the compact. This prevention of abnormal temperature rise is important when using raw materials with a large thermal expansion coefficient (vulnerable to thermal shock). For example, when 20 parts by mass or more of organic binder is blended with 100 parts by mass of silicon carbide and silicon combined, it is preferable to perform calcination in an inert atmosphere.

[0063] The degreasing step and the subsequent firing step may be carried out as separate steps in the same or different furnaces, or may be carried out as consecutive steps in the same furnace. When degreasing and firing are carried out in different atmospheres, the former is also preferred, but the latter is also preferred from the standpoint of the total firing time, furnace operating costs, etc.

[0064] Firing conditions vary depending on the material of the columnar honeycomb structure, but are preferably performed in an inert atmosphere such as nitrogen or argon at 1400 to 1500°C for 1 to 10 hours. After firing, in order to improve durability, it is preferable to perform oxidation treatment at 1100 to 1300°C for 1 to 20 hours. There are no particular limitations on the degreasing and firing methods, and firing can be performed using an electric furnace, gas furnace, etc.

[0065] When providing a honeycomb structure as a bonded segment body, the bonded segment body can be manufactured, for example, by the following procedure. A plurality of columnar honeycomb structures are prepared as segments, and a film for preventing adhesion of a bonding material is attached to both end faces of each segment, and a bonding material is applied to the side faces (bonding surfaces). Next, these segments are arranged adjacent to each other so that their side faces face each other, and adjacent segments are pressure-bonded together. After pressure-bonding, any undried bonding material that protrudes from at least one of the side faces, first end face, and second end face of the bonded segment body is scraped off, and the body is then heated and dried. After drying, the film for preventing adhesion of a bonding material is peeled off. In this way, a bonded segment body is manufactured in which the side faces of adjacent segments are bonded together with a bonding material.

[0066] The material of the film for preventing adhesion of a bonding material is not particularly limited, but suitable materials include synthetic resins such as polypropylene (PP), polyethylene terephthalate (PET), polyimide, and Teflon (registered trademark). The film preferably has an adhesive layer, and the adhesive layer is preferably made of an acrylic resin, a rubber resin (e.g., a rubber whose main component is natural rubber or synthetic rubber), or a silicone resin.

[0067] The bonding material may be, for example, a cement prepared by mixing ceramic powder, a dispersion medium (e.g., water), and, if necessary, additives such as a binder, a deflocculating agent, and a foaming resin. Ceramics include cordierite, mullite, zirconium phosphate, aluminum titanate, silicon carbide, silicon-silicon carbide composites (e.g., Si-bonded SiC), cordierite-silicon carbide composites, zirconia, spinel, indialite, sapphirine, corundum, titania, and silicon nitride, and it is more preferable that the bonding material be made of the same material as the columnar honeycomb structure segments. Examples of binders include polyvinyl alcohol and methyl cellulose.

[0068] Furthermore, if desired, the outer peripheral side wall of the joined segment assembly may be ground to form a desired shape (e.g., a cylindrical shape). In this case, it is preferable to apply a coating material to the outer peripheral side surface of the joined segment assembly after grinding, and then dry and heat treat it to form a new outer peripheral side wall.

[0069] The coating material is not particularly limited, and known peripheral coating materials can be used. Examples of peripheral coating materials include those obtained by adding additives such as organic binders, foamed resins, and dispersants, and water to inorganic raw materials such as inorganic fibers, colloidal silica, clay, and ceramic particles, and kneading them to form a slurry. In addition, the method for applying the peripheral coating material is not particularly limited, and known methods can be used.

[0070] When the honeycomb structure is used as a catalyst carrier, the partition walls can be made to support a catalyst. The method for supporting the catalyst on the partition walls is not particularly limited, and any known method can be used. For example, a method in which a catalyst composition slurry is brought into contact with porous partition walls, followed by drying and firing can be mentioned.

[0071] The catalyst composition slurry desirably contains a catalyst appropriate for its application. Examples of catalysts include, but are not limited to, oxidation catalysts, reduction catalysts, and three-way catalysts for removing pollutants such as soot, nitrogen oxides (NOx), soluble organic fractions (SOF), hydrocarbons (HC), and carbon monoxide (CO). In particular, when the honeycomb structure is used as a filter such as a DPF or GPF, particulate matter (PM) such as soot and SOF in the exhaust gas is trapped in the filter, so it is preferable to support a catalyst that supports the combustion of the particulate matter. The catalyst may appropriately contain, for example, noble metals (e.g., Pt, Pd, Rh), alkali metals (e.g., Li, Na, K, Cs), alkaline earth metals (e.g., Ca, Ba, Sr), rare earths (e.g., Ce, Sm, Gd, Nd, Y, Zr, Ca, La, Pr), transition metals (e.g., Mn, Fe, Co, Ni, Cu, Zn, Sc, Ti, V, Cr), and the like. [Example]

[0072] <1. Manufacturing of honeycomb structure> The following raw material powders were prepared: Silicon carbide (SiC) with a median diameter (D50) of 30 μm Silicon (Si) with a median diameter (D50) of 5 μm Starch (pore former) with a median diameter (D50) of 35 μm Hydroxypropyl methylcellulose (organic binder) Sepiolite (inorganic binder) Montmorillonite (inorganic binder) Aluminum oxide (Al2O3) (sintering aid) Silicon oxide (SiO2) (sintering aid) Strontium oxide (SrO) (sintering aid)

[0073] These were powder-mixed to satisfy the blending conditions listed in Table 1 according to the test number (Examples 1 to 12, Comparative Examples 1 and 2), and approximately 30 to 60 parts by mass of water was added to 100 parts by mass of silicon carbide and silicon combined, followed by kneading using a kneader. The resulting mixed clay was extruded from a predetermined die in an extrusion molding machine to form a rectangular parallelepiped honeycomb molded body. The honeycomb molded body had an outer peripheral side wall and partition walls disposed on the inner peripheral side of the outer peripheral side wall, which partitioned and formed a plurality of cells extending from one end face to the other end face.

[0074] The honeycomb molded body was microwave-dried, then dried at 120°C for 2 hours using a hot air dryer, and processed as needed, such as cutting off both end faces to a predetermined length, to obtain a dried honeycomb body. Next, the dried honeycomb body was placed in a continuous electric furnace and degreased (by burning off the organic binder) by heating at 450°C or less for 5 hours in an air atmosphere to obtain a degreased honeycomb body. Next, the degreased honeycomb body was fired at 1450°C for 2 hours in an Ar atmosphere to obtain a honeycomb structure. The obtained honeycomb structure had dimensions of 35mm length x 35mm width x 150mm height (in the cell extension direction), an average partition wall thickness of 305µm, a square cell cross-sectional shape, and a cell density of 44 cells / cm. 2 The honeycomb formed bodies and honeycomb structures were manufactured in the numbers required for the evaluation of the following characteristics.

[0075] [Table 1]

[0076] <2. Evaluation of honeycomb structure properties> The honeycomb structures obtained above were each subjected to the following characteristic evaluations.

[0077] (2-1. Composition analysis) A 10 g partition wall sample was collected from the honeycomb structure, and the composition of the partition walls was analyzed using a sequential type X-ray fluorescence analyzer (manufactured by Rigaku Corporation: Model ZSX Primus II), and the following values ​​were calculated. The results are shown in Table 2. T1: total mass parts of aluminum oxide, silicon oxide, and strontium oxide per 100 mass parts of silicon carbide and silicon in the partition walls A1: parts by mass of aluminum oxide relative to 100 parts by mass of the total of silicon carbide and silicon in the partition walls B1: Parts by mass of silicon oxide per 100 parts by mass of the total of silicon carbide and silicon in the partition walls C1: parts by mass of strontium oxide relative to 100 parts by mass of the total of silicon carbide and silicon in the partition wall D1: Parts by mass of silicon carbide per 100 parts by mass of the total of silicon carbide and silicon in the partition walls E1: Total mass concentration of silicon carbide and silicon in the partition wall (mass%) In view of the manufacturing method, it is presumed that the outer peripheral side wall has the same composition as the partition wall.

[0078] (2-2. Porosity) Partition wall samples were collected from a plurality of locations of the honeycomb structure, and the porosity was determined by the mercury intrusion method specified in JIS R1655:2003, and the average value was taken as the measured value.

[0079] (2-3. Average linear expansion coefficient) Measurement samples were taken from the honeycomb structure, and the average coefficient of linear expansion (CTE) was measured according to JIS R1618:2002 at temperatures ranging from 40°C to 800°C using the procedure described above. A thermal analyzer (model TD5000SE) manufactured by Netsch Japan was used for the measurements. The results are shown in Table 2.

[0080] (2-4. Thermal conductivity) Measurement samples were taken from the honeycomb structure, and the thermal conductivity was measured at 50°C according to the ASTM E1530 method using the procedure described above. A steady-state thermal conductivity measuring instrument (model GH-1) manufactured by Advance Riko Co., Ltd. was used for the measurement. The results are shown in Table 2.

[0081] <3. Evaluation of honeycomb molding properties> The dried honeycomb body during the manufacturing of the above honeycomb structure was cut into a size of 35 mm x 35 mm x 20 mm (length in the cell extension direction), and after degreasing (burning and removing the organic binder), the structure was compressed in the cell extension direction and measured by a method of calculating the strength at break. The results are shown in Table 2.

[0082] [Table 2]

[0083] <4. Consideration> All of Examples 1 to 12 and Comparative Examples 1 and 2 were honeycomb structures containing a silicon-silicon carbide composite material, and contained aluminum oxide, silicon oxide, and strontium oxide as firing aids. However, in Comparative Examples 1 and 2, the aluminum oxide content was too low, resulting in an A1 / T1 ratio of less than 0.045, resulting in a high average linear expansion coefficient. Furthermore, comparing the Examples, it was found that a practically high thermal conductivity could be obtained by not having an A1 / T1 ratio that was too high (especially when it was 0.120 or less). It was also found that adding sepiolite to the molding raw material composition significantly improved the strength after the organic binder was burned off. [Explanation of symbols]

[0084] 100: Honeycomb structure 102: Outer wall 104: First end surface 106: Second end face 108: Cell 110: Segment 112: Bulkhead 117: Bonding material 200: Honeycomb structure 202: Outer wall 204: First end surface 206: Second end face 208a: First cell 208b: Second cell 209: Plugging part 212: Bulkhead

Claims

1. A honeycomb structure having partition walls that define a plurality of cells extending from one end face to the other end face, the partition walls contain silicon carbide, silicon, and a firing aid; The sintering aid contains aluminum oxide, silicon oxide, and strontium oxide, and the total parts by mass of the aluminum oxide, silicon oxide, and strontium oxide relative to 100 parts by mass of the silicon carbide and silicon in the partition walls is T 1 and the mass parts of aluminum oxide relative to a total of 100 mass parts of silicon carbide and silicon in the partition wall is A 1 Then, 0.045≦A 1 / T 1 fulfill, Honeycomb structure.

2. 0.045≦A 1 / T 1 The honeycomb structure according to claim 1, wherein the ratio satisfies ≦0.

200.

3. The mass parts of silicon oxide relative to 100 mass parts of the total of silicon carbide and silicon in the partition wall is B 1 Then, 0.70≦B 1 / T 1 The honeycomb structure according to claim 1, wherein the ratio satisfies ≦0.

90.

4. The mass parts of strontium oxide relative to 100 mass parts of the total of silicon carbide and silicon in the partition wall is C 1 Then, 0.050≦C 1 / T 1 The honeycomb structure according to claim 1, wherein the ratio satisfies ≦0.

200.

5. 10≦T 1 The honeycomb structure according to claim 1, wherein the ratio satisfies ≦40.

6. The mass parts of silicon carbide relative to 100 mass parts of the total of silicon carbide and silicon in the partition wall is D 1 Then, 70≦D 1 The honeycomb structure according to claim 1, wherein the honeycomb structure satisfies the following condition: ≦95.

7. The total mass concentration of silicon carbide and silicon in the partition wall is E 1 In terms of mass%, 60≦E 1 The honeycomb structure according to claim 1, wherein the honeycomb structure satisfies the following condition: ≦95.

8. 2. The honeycomb structure according to claim 1, wherein the partition walls contain sepiolite.

9. The mass parts of sepiolite relative to 100 mass parts of silicon carbide and silicon in total is F 1 Then, 0.5≦F 1 The honeycomb structure according to claim 8, wherein the ratio satisfies ≦5.

0.

10. 2. The honeycomb structure according to claim 1, wherein the partition walls have a porosity of 40% or more.

11. 2. The honeycomb structure according to claim 1, further comprising plugging portions disposed in openings of predetermined cells at said one end face and in openings of remaining cells at said other end face.

12. The average linear expansion coefficient measured according to JIS R1618:2002 when the temperature was changed from 40°C to 800°C was 5.5 x 10 -6 2. The honeycomb structure according to claim 1, wherein the tensile strength is 1 / K or less.

13. 2. The honeycomb structure according to claim 1, wherein the thermal conductivity measured at 50° C. in accordance with the method of ASTM E1530 is 3.0 W / (m·K) or more.

14. A molding raw material composition containing silicon carbide, silicon, a pore-forming material, and a sintering aid, The sintering aid contains aluminum oxide, silicon oxide, and strontium oxide, and the total parts by mass of aluminum oxide, silicon oxide, and strontium oxide relative to 100 parts by mass of silicon carbide and silicon is T 2 The parts by mass of aluminum oxide relative to 100 parts by mass of silicon carbide and silicon combined is A 2 Then, 0.20≦A 2 / T 2 A molding raw material composition that satisfies the above.

15. 0.20≦A 2 / T 2 The molding material composition according to claim 14, which satisfies ≦0.

60.

16. The mass parts of silicon oxide per 100 mass parts of silicon carbide and silicon combined is B 2 Then, 0.20≦B 2 / T 2 The molding material composition according to claim 14, which satisfies ≦0.

60.

17. The mass parts of strontium oxide per 100 mass parts of silicon carbide and silicon combined is C 2 Then, 0.10≦C 2 / T 2 The molding material composition according to claim 14, which satisfies ≦0.

50.

18. 1.0≦T 2 The molding material composition according to claim 14, which satisfies ≦10.

0.

19. The mass parts of silicon carbide per 100 mass parts of silicon carbide and silicon combined is D 2 Then, 70≦D 2 The molding raw material composition according to claim 14, which satisfies a viscosity of ≦95.

20. The molding raw material composition according to claim 14, which contains sepiolite.

21. The mass parts of sepiolite relative to 100 mass parts of silicon carbide and silicon in total is F 2 Then, 0.50≦F 2 The molding material composition according to claim 20, which satisfies a value of ≦5.

0.

22. The mass parts of the pore-forming material relative to 100 mass parts of silicon carbide and silicon in total is G 2 Then, 1.0≦G 2 The molding material composition according to claim 14, which satisfies a value of ≦30.

0.

23. A molding step of extruding the molding raw material composition according to any one of claims 14 to 22 to produce a molded body; A firing step of firing the molded body to produce a porous body, Method for producing porous bodies.

24. The method for producing a porous body according to claim 23, wherein the molded body has partition walls that define a plurality of cells extending from one end face to the other end face.

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