Silicon-carbide-based ceramic honeycomb structure and production method therefor

Abstract

Provided is a method for producing a silicon-carbide-based ceramic honeycomb structure, the method being characterized by including a step in which a molded ceramic honeycomb comprising an aggregate composed of silicon carbide particles and an inorganic binder comprising alumina-source particles and / or magnesia-source particles is placed inside a sagger and burned in an oxidizing gas atmosphere. The method is also characterized in that: a member constituting the sagger has a honeycomb structure having a large number of linear holes extending in one direction and separated by porous partitions; the sagger has a closed space for accommodating the molded ceramic honeycomb; and the proportion of the total cross-sectional area of linear holes whereby the outside of the sagger communicates with the closed space, with respect to the total area of the inner surfaces of the sagger which face the closed space, is 0-5%.

Description

Silicon carbide ceramic honeycomb structure and manufacturing method thereof

[0001] The present invention relates to a silicon carbide-based ceramic honeycomb structure used in a ceramic honeycomb filter for removing particulate matter (hereinafter simply referred to as "PM") and the like from exhaust gas emitted from an internal combustion engine such as a diesel engine, thereby purifying the exhaust gas, and a method for manufacturing the same.

[0002] Because NOx and PM contained in diesel engine exhaust gases can be released into the atmosphere and cause adverse effects on humans and the environment, a honeycomb structure supporting a NOx catalyst and a ceramic honeycomb filter for capturing PM have traditionally been installed in the exhaust pipe of diesel engines as exhaust systems. It is also known that refractory particles, such as silicon carbide (SiC) particles, which have excellent thermal shock resistance, are used as the constituent material of ceramic honeycomb filters for capturing PM in exhaust gases and purifying the exhaust gases. As such a silicon carbide-based ceramic honeycomb filter, a ceramic honeycomb filter 500 has been proposed, which has a structure in which multiple silicon carbide-based honeycomb segments 51 with a rectangular outer shape are integrally bonded together by a bonding material layer 530, as shown in FIG. 10 , to prevent defects such as cracks and fractures or melting damage caused by thermal stress due to thermal shock caused by sudden temperature changes in the exhaust gases.

[0003] A widely used method for manufacturing such silicon carbide-based honeycomb segments is one that uses silicon carbide aggregate particles and metallic silicon binder as raw materials and includes a debinding process for a ceramic honeycomb formed body, a firing process in an inert gas atmosphere, and an oxidation process in the atmosphere.

[0004] For example, Patent Document 1 discloses a method for manufacturing a silicon carbide honeycomb segment 51 used in a ceramic honeycomb filter 500 having a segment-bonded structure, which includes a firing step in which an extruded silicon carbide (Si / SiC) honeycomb molded body is heated in a firing furnace in an inert gas atmosphere together with a firing member (sagger) made of a ceramic material with an alumina content of 70% by weight or more, and an oxidation step in which the resulting sintered body is oxidized in the air, the firing step including a step of supplying an inert gas into the firing furnace and a step of adding a reducing gas into the firing furnace. However, the method of Patent Document 1 has a problem in that the firing step requires many steps because an inert gas is used, resulting in high costs.

[0005] In order to reduce firing costs, instead of using SiC and Si as raw materials for silicon carbide ceramics, ceramic particles consisting of silicon carbide particles and an inorganic binder are used, and a honeycomb molded body consisting of these ceramic particles is fired in an oxidizing atmosphere to produce silicon oxide on the surface of the silicon carbide particles, which bonds the silicon carbide particles together to produce an oxide-bonded silicon carbide-based honeycomb structure.

[0006] When a honeycomb formed body made of silicon carbide particles and an inorganic binder is fired in an oxidizing atmosphere, a sagger is required to prevent rapid oxidation of the silicon carbide particle surfaces. If a ceramic honeycomb formed body is fired in an oxidizing atmosphere without a sagger, the ceramic honeycomb formed body is directly exposed to the atmospheric gas, which tends to rapidly oxidize the silicon carbide particle surfaces, resulting in the formation of cristobalite and an increase in the thermal expansion coefficient of the honeycomb structure. If the thermal expansion coefficient is large, thermal shock caused by a sudden temperature change in the exhaust gas can cause large thermal stress in the ceramic honeycomb structure, which can lead to cracks.

[0007] Patent Document 2 discloses a ceramic setter (sagger) used in the firing process of ceramics for electronic devices, which is made of a tray-shaped ceramic member containing 98% by weight or more of alumina and 0.3% by weight or less of silica and having a relative density (bulk density / theoretical density x 100) of 95% or more, and which is honeycomb-shaped with a plurality of through-holes with inner diameters of 0.3 to 1 mm that open into a closed space that contains a ceramic honeycomb formed body. Patent Document 2 states that these through-holes enable uniform circulation of atmospheric gas between the inside and outside of the setter and can uniform the temperature distribution inside the setter.

[0008] However, when the ceramic setter (sagger) of Patent Document 2 is used to fire a ceramic honeycomb formed body made of silicon carbide particles and an inorganic binder in an oxidizing atmosphere, the ceramic setter has many through holes that open into the closed space that contains the ceramic honeycomb formed body, which results in a large amount of oxidizing atmosphere gas passing through the setter, making it impossible to prevent rapid oxidation of the silicon carbide particle surfaces.

[0009] JP 2018-154536 A JP 2003-306386 A Object of the invention

[0010] Therefore, an object of the present invention is to provide a method for manufacturing an oxide-bonded silicon carbide-based ceramic honeycomb structure that suppresses excessive oxidation of the silicon carbide particle surfaces when a ceramic honeycomb formed body is fired in an oxidizing gas atmosphere, thereby having thermal shock resistance equal to or greater than that of conventional structures, and to provide an oxide-bonded silicon carbide-based ceramic honeycomb structure obtained by this method.

[0011] As a result of intensive research to achieve the above-mentioned object, the inventors have discovered that when a ceramic honeycomb formed body made of silicon carbide particles and an inorganic binder is fired in an oxidizing atmosphere gas within a sagger, if the sagger is constructed of a member having a honeycomb structure with a large number of linear holes separated by porous partitions, the sagger has a closed space for accommodating the ceramic honeycomb formed body, and the ratio of the total cross-sectional area of ​​the linear holes connecting the outside of the sagger to the closed space is 0 to 5% relative to the total area of ​​the inner surface of the sagger facing the closed space, excessive oxidation of the silicon carbide particle surface can be suppressed, thereby obtaining an oxide-bonded silicon carbide-based ceramic honeycomb structure having thermal shock resistance equal to or greater than that of conventional structures, and have arrived at the present invention.

[0012] That is, the method of the present invention for manufacturing a silicon carbide-based ceramic honeycomb structure includes a step of placing a ceramic honeycomb formed body containing an aggregate consisting of silicon carbide particles and an inorganic binder including alumina source particles and / or magnesia source particles in a sagger and firing it in an oxidizing atmosphere gas, wherein the member constituting the sagger has a honeycomb structure having a plurality of linear holes extending in one direction separated by porous partitions, the sagger has a closed space for accommodating the ceramic honeycomb formed body, and the ratio of the total cross-sectional area of ​​the linear holes connecting the outside of the sagger to the closed space is 0 to 5% of the total area of ​​the inner surface of the sagger facing the closed space.

[0013] In one embodiment of the present invention, the sagger does not have any linear holes communicating between the outside and the closed space. Therefore, the total cross-sectional area of ​​the linear holes communicating with the closed space is 0% of the total area of ​​the inner surface of the sagger facing the closed space, which is 100%. In a preferred example, all linear holes extend parallel to the inner surface of the member constituting the sagger and therefore do not have ends opening to the inner surface. In another preferred example, some of the linear holes have ends on the inner surface of the sagger facing the closed space, but all of these linear holes are sealed on the inner and / or outer surface of the sagger so as not to communicate between the outside of the sagger and the closed space.

[0014] In another embodiment of the present invention, some of the linear holes have ends on the inner surface of the sagger facing the closed space, and the linear holes having ends on the inner surface comprise (a) linear holes that communicate between the outside of the sagger and the closed space, and (b) linear holes that are sealed on the inner surface and / or outer surface of the sagger so as not to communicate between the outside of the sagger and the closed space, and the proportion of linear holes that are sealed on the inner surface and / or outer surface of the sagger is 20% or more of the linear holes having ends on the inner surface.

[0015] The linear holes preferably have an inner diameter (circular equivalent diameter) of 1.35 to 1.60 mm. The cross-sectional area of ​​the linear holes is preferably 1.43 to 2.01 mm. 2 When the cross section of the linear hole is square, the length of one side is preferably 1.20 to 1.42 mm.

[0016] The bulk density of the sagger is 0.15 to 0.75 g / cm 3 It is preferable that:

[0017] The porosity of the partition walls of the sagger is preferably 35-70%.

[0018] The median pore size of the partition walls of the sagger is preferably 3 to 25 μm.

[0019] The thickness of the partition wall of the sagger is preferably 0.1 to 0.5 mm.

[0020] The cross-sectional area ratio of the linear holes in the sagger is preferably 50 to 80%.

[0021] It is preferable that the sagger is composed of a bottom plate, side plates and a cover plate, and that the linear hole extends horizontally within the bottom plate, side plates and cover plate.

[0022] The partition walls of the sagger are preferably made of ceramics containing at least one material selected from the group consisting of cordierite, alumina, mullite, silicon carbide, and silicon nitride as a main component, with cordierite being particularly preferred from the viewpoint of ease of forming porous partition walls.

[0023] The sagger is preferably placed on a heat-resistant ceramic base plate, which is preferably made mainly of mullite or alumina, has a porosity of 40% or less, and does not preferably have a honeycomb structure.

[0024] It is preferred to use a sagger assembly having multiple tiers of saggers with a heat-resistant ceramic base plate mounted beneath the bottom plate of each tier of saggers.

[0025] The silicon carbide-based ceramic honeycomb structure of the present invention is obtained by kneading ceramic particles containing an aggregate consisting of silicon carbide particles and an inorganic binder including alumina source particles and magnesia source particles with an organic binder, with water, extruding the resulting clay into a honeycomb shape, drying it to form a ceramic honeycomb formed body, and firing the ceramic honeycomb formed body, characterized in that the firing is carried out by placing the ceramic honeycomb formed body in a sagger, the components constituting the sagger have a honeycomb structure having a plurality of linear holes extending in one direction and separated by porous partitions, the sagger has a closed space to accommodate the ceramic honeycomb formed body, and the ratio of the total cross-sectional area of ​​the linear holes connecting the outside of the sagger to the closed space is 0 to 5% of the total area of ​​the inner surface of the sagger facing the closed space.

[0026] The method of the present invention makes it possible to suppress excessive oxidation of the surfaces of silicon carbide particles even during the firing process in an oxidizing atmosphere gas, and to produce a silicon carbide-based ceramic honeycomb structure having strength and thermal shock resistance equal to or greater than conventional structures.

[0027] 1 is an exploded perspective view schematically showing an example of a state in which a ceramic honeycomb formed body is placed on a first sagger. FIG. 2 is an exploded perspective view schematically showing an example of a state in which a ceramic honeycomb formed body is placed on a second sagger. FIG. 3 is an exploded perspective view schematically showing an example of a state in which a ceramic honeycomb formed body is placed on second saggers stacked in two tiers. FIG. 4 is an exploded perspective view schematically showing another example of a state in which a ceramic honeycomb formed body is placed on second saggers stacked in two tiers. FIG. 5 is an exploded perspective view schematically showing yet another example of a state in which a ceramic honeycomb formed body is placed on second saggers stacked in two tiers. FIG. 6 is an exploded perspective view schematically showing an example of a side plate constituting the sagger of the present invention. FIG. 7 is an exploded perspective view schematically showing another example of a side plate constituting the sagger of the present invention. FIG. 8 is an exploded perspective view schematically showing yet another example of a side plate constituting the sagger of the present invention. FIG. 9 is a perspective view schematically showing an example of a ceramic honeycomb structure. FIG. 10 is a perspective view schematically showing an example of a ceramic honeycomb segment. 1 is a perspective view showing an example of a ceramic honeycomb filter formed by integrally bonding ceramic honeycomb segments, and FIG. 2 is a side view showing a deformation amount δ in the width direction of a ceramic honeycomb formed body due to firing.

[0028] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited thereto, and various changes, modifications, or improvements can be made without departing from the technical spirit of the invention.

[0029] The method of the present invention for manufacturing a silicon carbide-based ceramic honeycomb structure includes the steps of kneading ceramic particles containing an inorganic binder including an aggregate made of silicon carbide particles and alumina source particles and / or magnesia source particles with water to prepare a clay, extruding the resulting clay into a honeycomb shape, drying the extruded body to form a ceramic honeycomb formed body, and firing the ceramic honeycomb formed body. By using alumina source particles and / or magnesia source particles as the inorganic binder and firing the ceramic honeycomb formed body in an oxidizing gas atmosphere, an oxide-bonded silicon carbide-based ceramic honeycomb structure can be obtained.

[0030] [1] Ceramic particles The silicon carbide-based ceramic honeycomb structure comprises an aggregate made of silicon carbide particles and an inorganic binder containing alumina source particles and / or magnesia source particles, and the aggregate of silicon carbide particles is bonded via the inorganic binder phase to form pores by firing.

[0031] (1) Silicon carbide particles The median particle size of the silicon carbide particles is preferably 20 to 55 μm. If the median particle size is less than 20 μm, the porosity of the partition walls is insufficient, and if it exceeds 55 μm, the porosity of the partition walls becomes too high. The median particle size of the silicon carbide particles is more preferably 25 to 40 μm.

[0032] (2) Inorganic Binder (a) Alumina Source Particles The alumina source particles are preferably alumina (Al2O3) particles or particles of a compound that produces alumina (Al2O3) upon firing. Specifically, the alumina source particles are preferably alumina particles or aluminum hydroxide particles. The average particle size (median particle size) of the alumina source particles is preferably 1 to 15 μm.

[0033] (b) Magnesia Source Particles The magnesia source particles are preferably magnesia (MgO) particles or particles of a compound that produces magnesia (MgO) upon firing. Specifically, the magnesia source particles are preferably one or more of magnesium oxide particles, magnesium hydroxide particles, and talc particles. The average particle size (median particle size) of the magnesia source particles is preferably 1 to 15 μm.

[0034] (c) Other Inorganic Particles The inorganic binder may also contain inorganic particles such as spinel particles, mullite particles, forsterite particles, etc. When the entire inorganic binder is taken as 100 mass%, the proportion of inorganic particles other than the alumina source particles and the magnesia source particles is preferably 10 mass% or less, and more preferably 5 mass% or less.

[0035] (d) Blending Amount It is preferable to blend a total of 6 to 15 mass% of alumina source particles and / or magnesia source particles relative to 100 mass% of silicon carbide particles. If the alumina source particles and / or magnesia source particles are less than 6 mass%, the bonding strength of the bonding phase bonding the silicon carbide particles together decreases, resulting in a decrease in the strength of the ceramic honeycomb structure. On the other hand, if the amount exceeds 15 mass%, the thermal shock resistance of the resulting silicon carbide-based ceramic honeycomb structure decreases. The lower limit of the total amount of alumina source particles and / or magnesia source particles relative to 100 mass% of silicon carbide particles is preferably 7 mass%, more preferably 8 mass%. Furthermore, the upper limit of the total amount of alumina source particles and / or magnesia source particles is preferably 14 mass%, more preferably 13 mass%.

[0036] (e) Effects of Alumina Source Particles and / or Magnesia Source Particles The present invention does not use metallic silicon, which has been conventionally used as an inorganic binder, and therefore does not require firing in a non-oxidizing atmosphere and subsequent oxidation treatment, which are required when metallic silicon is used. Furthermore, because the alumina source particles and / or magnesia source particles are used as the inorganic binder and firing is performed in an oxidizing atmosphere, the firing temperature can be set lower than in the past. Therefore, the method of the present invention can reduce firing costs and enable the production of silicon carbide-based ceramic honeycomb structures more inexpensively than conventional techniques.

[0037] [2] Organic Binder: An organic binder is blended and mixed with ceramic particles (forming raw material) containing silicon carbide particles and an inorganic binder. Examples of organic binders include methyl cellulose, ethyl cellulose, ethyl methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl ethyl cellulose. Among these, hydroxypropyl methyl cellulose and / or methyl cellulose are preferred. The organic binder is preferably present in an amount of 5 to 15% by mass relative to 100% by mass of the forming raw material.

[0038] [3] Preparation of clay: A mixture of ceramic particles and an organic binder is kneaded with water to prepare a plastic clay. The water content is adjusted so that the clay has a hardness that allows it to be molded, and is preferably 20 to 50% by weight based on 100% of the molding raw materials.

[0039] [4] Molding and Drying The clay is extruded through a die for molding a honeycomb structure to form a rectangular prism-shaped body having a honeycomb structure. This body is dried to obtain a ceramic honeycomb molded body. The drying method is not particularly limited, but examples thereof include hot air drying, microwave heating drying, and high-frequency heating drying.

[0040] [5] Sagger (1) Structure The ceramic honeycomb formed body is fired in an oxidizing gas atmosphere while placed in a sagger as shown in Figures 1 to 5. The first sagger 100 shown in Figure 1 comprises a flat cover plate 13 and a bottom member 14 integrally having a flat bottom 141 and sidewalls 142 extending upward from the sides of the bottom 141. Both the cover plate 13 and the bottom member 14 have a honeycomb structure with numerous linear holes 22 separated by porous partition walls 21. The cover plate 13 and the bottom 141 and sidewalls 142 of the bottom member 14 form a closed space 15 that accommodates the ceramic honeycomb formed body. In the example shown in Figure 1, the cover plate 13 and the bottom 141 are rectangular, and the sidewalls 142 are four vertical rectangular wall plates standing from the four sides of the rectangular bottom 141.

[0041] In the cover plate 13, the linear holes 22 extend substantially horizontally (in a direction perpendicular to the thickness direction of the cover plate 13), and the open ends 22a of the linear holes 22 do not face the closed space 15. Here, "substantially horizontally" does not mean that all the linear holes 22 need to extend completely horizontally, and that less than 5% of the linear holes 22 may communicate between the closed space 15 and the outside due to slight inclination or curvature of the linear holes 22. However, in order to easily control the oxidizing atmosphere in the closed space 15, the percentage of the linear holes 22 communicating from the outside of the sagger 100 to the closed space 15 (penetration rate) is preferably less than 3%, and more preferably 0%.

[0042] In the bottom member 14, which integrally has a bottom 141 and sidewalls 142, the linear holes 22 extend substantially horizontally (in a direction perpendicular to the thickness direction of the bottom 141). Again, "substantially horizontally" has the same meaning as above. In the bottom 141, the linear holes 22 do not substantially open into the closed space 15, but in one of the two pairs of opposing sidewalls 142, the linear holes 22 necessarily open into the closed space 15. In the example shown in FIG. 1 , the linear holes 22 do not open on the inner surface 14a of the first pair of sidewalls 142a, but open on the inner surface 14b of the second pair of sidewalls 142b. In order to prevent the surfaces of the silicon carbide particles in the ceramic honeycomb formed body 5 from being excessively oxidized by the oxidizing atmosphere gas in the firing furnace flowing into the closed space 15 through the linear holes 22, at least a portion of the ends 22a of the linear holes 22 that open to the inner surface 14b are sealed with a ceramic material (referred to as sealed ends 22b). The ceramic material that seals the ends 22a of the linear holes 22 is preferably the same material as that of the sagger 100.

[0043] Of all the ends 22a, 22b of the linear holes 22 facing the closed space 15, the proportion of the sealed ends 22b in terms of cross-sectional area is preferably 20% or more, more preferably 50% or more, even more preferably 70% or more, most preferably 90% or more, and particularly preferably 100%. Therefore, of all the ends 22a, 22b of the linear holes 22 facing the closed space 15, the proportion of the open ends 22a in terms of cross-sectional area is preferably 80% or less, more preferably 50% or less, even more preferably 30% or less, most preferably 10% or less, and particularly preferably 0%. Here, the above-mentioned cross-sectional area of ​​the linear holes 22 refers to the area of ​​the cross section in a plane perpendicular to the longitudinal direction (horizontal plane).

[0044] In the first sagger 100, in which the ends of the linear holes 22 are present only on the inner surfaces 14b, 14b of a pair of opposing side wall portions 142b, 142b, and no ends of the linear holes 22 are present at all on the inner surface 13a of the cover plate 13, the inner surface of the bottom 141, or the inner surfaces 14a, 14a of the side wall portions 142a, 142a, the ratio of the total cross-sectional area of ​​the open ends 22a to the total area of ​​the inner surfaces of the first sagger 100 must satisfy the condition of 0 to 5%, but it is preferable that the ratio of the sealed ends 22b to all ends of the linear holes 22 (open ends 22a + sealed ends 22b) is 20% or more.

[0045] After placing a plurality of ceramic honeycomb formed bodies 5 on the bottom 141 of the bottom member 14, a cover plate 13 is placed on the upper surface of the side wall portion 142 to form a first sagger 100 containing a plurality of ceramic honeycomb formed bodies 5.

[0046] 2 shows a second sagger 200 made up of one bottom plate 11, four side plates 12, and one cover plate 13. In the illustrated example, the bottom plate 11 and the cover plate 13 are both rectangular flat plates in plan view, and the side plate 12 has a rectangular cross section. Four side plates 12 are arranged on the four sides of the upper surface of the rectangular bottom plate 11, and after placing a plurality of ceramic honeycomb formed bodies 5 on the bottom plate 11, the rectangular cover plate 13 is arranged on the upper surfaces of the side plates 12, thereby forming a closed space 15 containing a plurality of ceramic honeycomb formed bodies 5.

[0047] The bottom plate 11, the side plates 12, and the cover plate 13 all have a honeycomb structure with a large number of linear holes 22 separated by porous partition walls 21. In all of the bottom plate 11, the side plates 12, and the cover plate 13, the linear holes 22 extend horizontally. Therefore, in the bottom plate 11 and the cover plate 13, the ends 22a, 22a of the linear holes 22 do not open to the surfaces 11a, 13a that form the closed space 15. Therefore, the ratio of the total cross-sectional area of ​​the linear holes 22 that communicate between the outside and the closed space 15 to the total area of ​​the inner surfaces facing the closed space 15 is 0%.

[0048] In the second sagger 200 shown in FIG. 2, the linear holes 22 in the side plates 12 extend longitudinally (away from the closed space 15). However, the linear holes 22 in some side plates 12 may extend laterally (away from the closed space 15). In the example shown in FIG. 6, a pair of opposing side plates 212-1, 212-1 have linear holes 22 extending longitudinally, while another pair of opposing side plates 212-2, 212-2 have linear holes 22 extending laterally. To prevent excessive flow of the oxidizing atmosphere gas in the firing furnace into the sagger 200, at least a portion of the inner and / or outer ends 22a of the linear holes 22 in the side plates 212-2, 212-2 are preferably sealed with a ceramic material to form ends 22b. The ceramic material sealing the ends 22a of the linear holes 22 is preferably the same as that of the sagger 200.

[0049] With the sum of the open ends 22a and sealed ends 22b of the linear holes 22 communicating with the closed space 15 being 100%, the proportion of the sealed ends 22b in terms of cross-sectional area is preferably 20% or more, more preferably 50% or more, and most preferably 100%. Therefore, the proportion of the open ends 22a (penetration rate) in terms of cross-sectional area is preferably 80% or less, more preferably 50% or less, and most preferably 0%. Even in this case, the proportion of the total cross-sectional area of ​​the linear holes 22 communicating between the outside of the sagger 200 and the closed space 15 to the total area of ​​the inner surface of the sagger 200 facing the closed space 15 needs to be 0 to 5%.

[0050] Instead of the four side plates 12 with a rectangular cross section shown in Figure 2, four L-shaped side plates 121, 122, 123, and 124 shown in Figure 7(a) or two U-shaped side plates 125, 125 shown in Figure 7(b) may be used. Both the L-shaped side plates 121-124 and the U-shaped side plates 125, 125 have a honeycomb structure with a large number of horizontally extending linear holes 22 separated by porous partition walls. Because both the L-shaped side plates 121-124 and the U-shaped side plates 125, 125 have orthogonal sides, the linear holes 22 always have an open end 22a on some side that faces the closed space 15. In order to prevent excessive flow of the oxidizing atmosphere gas in the firing furnace into the sagger 200, it is preferable that at least a portion of the open end 22a on the inner and / or outer side that communicates with the closed space 15 is made into an end 22b sealed with a ceramic material (preferably the same material as the sagger 200).

[0051] In this case, too, the proportion of the sealed end 22b in terms of cross-sectional area is preferably 20% or more, more preferably 50% or more, and most preferably 100%, of the total of the open end 22a and the sealed end 22b, which is 100%. Therefore, the proportion of the open end 22a (penetration rate) in terms of cross-sectional area is preferably 80% or less, more preferably 50% or less, and most preferably 0%. Even in this case, the proportion of the total cross-sectional area of ​​the linear holes 22 connecting the outside of the sagger 200 to the closed space 15 needs to be 0 to 5% of the total area of ​​the inner surface of the sagger 200 facing the closed space 15.

[0052] Although a single sagger 200 may be used, it is preferable to use a sagger assembly 201 in which multiple saggers are stacked as shown in Figure 3 in order to improve the efficiency of firing the ceramic honeycomb formed body. The sagger assembly 201 can be formed by placing spacers 3 at the four corners of the bottom surface of the cover plate 13 of the first sagger 201a, and assembling the second sagger 201b on top of the spacers 3 in the same manner. Saggers from the third sagger onwards may also be formed. Stacking multiple saggers with spacers 3 between them makes it easier to handle the saggers when loading and unloading them from the firing furnace.

[0053] 4 shows a sagger assembly 202 in which a first sagger 201a is formed on spacers 3 placed at the four corners, and a second sagger 201b is formed on top of that via spacers 3. Placing spacers 3 at the four corners of the bottom plate 11 of the first sagger 201a makes it even easier to handle the sagger assembly 202 when it is taken in and out of the firing furnace.

[0054] For example, if spacers 3, 3 are placed at the four corners of the bottom surface of the bottom plates 11, 11 of each sagger 201a, 201b as shown in Figure 4 and a ceramic honeycomb formed body is fired, the weight of the ceramic honeycomb formed body may cause the bottom plates 11, 11 to deform at the firing temperature, which may result in deformation of the resulting honeycomb sintered body. In order to prevent such deformation of the honeycomb sintered body, it is preferable to place the saggers 201a, 201b on heat-resistant ceramic bottom plates 4, 4 as shown in Figure 5. It is preferable to place spacers 3 at the four corners of the underside of each heat-resistant ceramic bottom plate 4 to facilitate handling when loading and unloading the sagger assembly 203 into and out of the firing furnace.

[0055] The main component of the heat-resistant ceramic base plate 4 is preferably a heat-resistant ceramic material, such as mullite or alumina. The base plate 4 is preferably a porous body without a honeycomb structure. The heat-resistant ceramic base plate 4 may have open ends in the direction of the mounting surface. The shape, size, number, and location of the open ends are not particularly limited.

[0056] The sagger is constructed from a honeycomb structure having numerous linear holes 22 separated by porous partition walls, and most or all of the linear holes 22 are not open to the closed space 15. This prevents the ceramic honeycomb formed body 5 from being excessively exposed to the oxidizing atmosphere gas in the firing furnace through the linear holes 22. The oxidizing atmosphere gas that flows into the linear holes 22 passes through the porous partition walls 21 and gradually diffuses into the closed space 15 at an appropriate rate, thereby preventing excessive oxidation of the silicon carbide particle surfaces and enabling the production of an oxide-bonded silicon carbide-based ceramic honeycomb structure. Therefore, the silicon carbide-based ceramic honeycomb structure obtained by the method of the present invention has thermal shock resistance and strength equivalent to or superior to conventional structures. Furthermore, since the sagger made of porous ceramics having numerous linear holes 22 has a small heat capacity, not much heat is lost when heating the sagger. This allows for easier use of heat to heat the ceramic honeycomb formed body, and shortens the firing time.

[0057] (2) Composition Ceramics such as alumina, mullite, cordierite, silicon carbide, silicon nitride, etc. can be used as the main component of the partition walls of the sagger. Among these, ceramics containing cordierite as the main component are preferred in consideration of thermal shock resistance during firing and cost reduction during sagger production.

[0058] (2) Manufacturing: To manufacture cordierite saggers, cordierite-forming raw powders (kaolin powder, talc powder, silica powder, alumina powder, and aluminum hydroxide powder) are blended to a chemical composition of 48-52% by weight SiO2, 33-37% by weight Al2O3, and 12-15% by weight MgO (e.g., 50% by weight SiO2, 35% by weight Al2O3, and 15% by weight MgO). To the resulting powder mixture, methyl cellulose and / or hydroxypropyl methyl cellulose as an organic binder, a lubricant, and a foamed resin as a pore-forming agent are added and thoroughly mixed in a dry process. Water is then added and thoroughly kneaded to produce a plasticized ceramic moldable body. This moldable body is extruded into a honeycomb shape and cut to the desired dimensions to obtain a ceramic molded body with a honeycomb structure. After drying the ceramic molded body, it is fired at a maximum holding temperature of 1400°C to obtain a honeycomb sintered body having a large number of linear holes 22 separated by porous partition walls composed mainly of cordierite. Honeycomb sintered bodies having the size of the bottom plate 11, side plates 12, and cover plate 13 may be directly manufactured, or to improve productivity, large honeycomb sintered bodies may be manufactured and then cut to the size of the bottom plate 11, side plates 12, and cover plate 13. The inner and / or outer end portions 22a of the linear holes 22 in the obtained bottom plate 11, side plates 12, and cover plate 13 are sealed with a ceramic material as necessary.

[0059] (3) Properties (a) Inner Diameter of Linear Holes The inner diameter of the linear holes 22 (the diameter of a circle converted from the cross-sectional area) is preferably 1.35 to 1.60 mm. If the inner diameter of the linear holes 22 is less than 1.35 mm, the rate at which the oxidizing atmosphere gas is passed through the closed space 15 is too low, resulting in a long firing time. On the other hand, if the inner diameter of the linear holes 22 exceeds 1.60 mm, the rate at which the oxidizing atmosphere gas is passed through the closed space 15 is too high, which may result in excessive oxidation of the silicon carbide particle surfaces. The inner diameter of the linear holes 22 is preferably 1.35 to 1.52 mm, more preferably 1.36 to 1.45 mm. The cross-sectional area of ​​the linear holes 22 is 1.43 to 2.01 mm. 2 Furthermore, when the cross section of the linear hole 22 is square, the length of one side is preferably 1.20 to 1.42 mm.

[0060] (b) Bulk density The bulk density of the sagger is 0.15 to 0.75 g / cm 3 The above bulk density allows (a) the oxidizing atmosphere gas in the firing furnace to be appropriately ventilated into the closed space 15, and (b) the heat is not lost in heating the saggers, and the heat is easily used to heat the ceramic honeycomb formed body, thereby shortening the firing time without setting the firing temperature as high as before and preventing excessive oxidation of the silicon carbide particle surfaces.

[0061] The bulk density of the sagger is 0.15 g / cm 3 If the bulk density is less than 0.20 g / cm, the oxidizing atmospheric gas is easily passed through the closed space 15 of the sagger, causing excessive oxidation of the surfaces of the silicon carbide particles in the ceramic honeycomb formed body, and the thermal expansion coefficient of the resulting honeycomb structure becomes large. 3 More preferably, it is 0.25 g / cm or more. 3 That's all.

[0062] On the other hand, the bulk density of the sagger is 0.75 g / cm 3 If the bulk density of the sagger exceeds 0.65 g / cm, the heat capacity of the sagger increases, and a large amount of heat is lost when heating the sagger, which requires a higher set temperature for firing and a longer firing time, resulting in excessive oxidation of the silicon carbide particle surface. 3 or less, more preferably 0.55 g / cm 3 The following is the result.

[0063] Bulk density (g / cm 3 ) is calculated by the following formula (1): Bulk density (g / cm 3 ) = ρ × [1-(p-t) 2 / p 2 ] × (1 - P / 100) ... (1) (where p: sagger partition pitch (mm), t: sagger partition thickness (mm), P: sagger porosity (%), ρ: true specific gravity of the main component constituting the sagger partition (g / cm 3 ) and for cordierite ρ = 2.52.

[0064] (c) Porosity The porosity of the partition walls of the sagger is preferably 35 to 70%. This porosity (a) allows the oxidizing atmosphere gas to be adequately ventilated into the closed space 15, and (b) prevents a large amount of heat from being lost when heating the sagger, and instead allows the heat to be used more easily to heat the ceramic honeycomb formed body. This allows the firing time to be shortened without setting the firing temperature as high as in the past, thereby preventing excessive oxidation of the silicon carbide particle surfaces.

[0065] If the porosity of the partition walls of the sagger is less than 35%, the heat capacity of the sagger increases, and a large amount of heat is lost when heating the sagger, which requires a higher firing temperature and a longer firing time, resulting in excessive oxidation of the silicon carbide particle surfaces.The porosity of the partition walls of the sagger is preferably 45% or more, and more preferably 50% or more.

[0066] On the other hand, if the porosity of the partition walls of the sagger exceeds 70%, the ceramic honeycomb formed body becomes more susceptible to exposure to an oxidizing atmosphere gas, and the strength of the sagger decreases, making it more susceptible to breakage. If the sagger breaks, the oxidizing atmosphere gas flows into the closed space 15 from the broken part, causing excessive oxidation of the silicon carbide particle surfaces. The porosity of the partition walls of the sagger is preferably 68% or less, and more preferably 65% ​​or less.

[0067] The porosity of the partition walls can be measured by mercury intrusion porosimetry. A test piece (10 mm x 10 mm x 10 mm) cut from the sagger is placed in a measuring cell of a Micromeritics Autopore III, and after the pressure inside the cell is reduced, mercury is introduced to apply pressure, and the relationship between the pressure and the volume of mercury forced into the pores in the test piece is determined. When the mercury pressure is 1800 psi (1.26 kg / mm 2 The cumulative pore volume of the pores (corresponding to a pore diameter of approximately 0.1 μm) is taken as the total pore volume. The porosity P (volume %) is calculated by the formula P = ρV / (1 + ρV) × 100 (where V is the measured value of the total pore volume (cm 3 / g), and ρ is the true specific gravity (g / cm 3 ) and for cordierite ρ = 2.52 g / cm 3 ) is calculated as follows.

[0068] (d) Median pore diameter of partition walls The median pore diameter d50 of the partition walls of the sagger is preferably 3 to 25 μm. When the median pore diameter d50 of the partition walls is within the range of 3 to 25 μm, the oxidizing atmosphere gas can diffuse into the closed space 15 through the partition walls of the sagger at an appropriate speed. The median pore diameter d50 of the partition walls is more preferably 3 to 15 μm, and most preferably 3 to 10 μm. The pore diameter d10 at which the cumulative pore volume of the partition walls is 10% of the total pore volume is preferably 0 to 3 μm, and the pore diameter d90 at which the cumulative pore volume is 90% is preferably 10 to 30 μm. The pore diameters d50, d10, and d90 of the partition walls can be measured by mercury intrusion porosimetry, similar to the porosity.

[0069] (e) Cross-sectional area ratio of linear holes The cross-sectional area ratio of the linear holes 22 of the sagger is preferably 50 to 80%. Here, the "cross-sectional area ratio of linear holes" refers to the ratio of the cross-sectional area of ​​the linear holes 22 to the unit cross-sectional area including the partition walls 21 and the linear holes 22 in a cross section perpendicular to the longitudinal direction. For example, if the cross section of the linear holes 22 is square, the unit cross-sectional area including the partition walls 21 and the linear holes 22 is (partition wall pitch) 2 and the cross-sectional area of ​​the linear hole 22 is (partition wall pitch - partition wall thickness) 2 Therefore, the cross-sectional area ratio of the linear holes 22 is (partition wall pitch - partition wall thickness) 2 / (Partition wall pitch) 2 It can be calculated using the formula:

[0070] The above cross-sectional area ratio allows an appropriate amount of oxidizing atmosphere gas to flow into the linear holes 22, and therefore an appropriate amount of oxidizing atmosphere gas is diffused into the closed space 15 through the partition walls of the sagger. As a result, not much heat is lost in heating the sagger, and the heat is more easily used to heat the ceramic honeycomb formed body. This allows the firing time to be shortened without setting the firing temperature as high as before, and prevents excessive oxidation of the silicon carbide particle surfaces.

[0071] If the cross-sectional area ratio of the linear holes 22 of the sagger is less than 50%, the heat capacity of the sagger increases, and a large amount of heat is lost when heating the sagger, which requires a higher firing temperature setting and takes too long for the oxidizing atmosphere gas to diffuse into the closed space 15. The cross-sectional area ratio of the linear holes 22 is preferably 55% or more, and more preferably 60% or more.

[0072] On the other hand, if the cross-sectional area ratio of the linear holes 22 exceeds 80%, the amount of oxidizing atmosphere gas flowing into the linear holes 22 becomes too large, making it difficult to suppress excessive oxidation of the silicon carbide particle surfaces. Furthermore, the strength of the sagger decreases and it may break, allowing the oxidizing atmosphere gas to flow into the closed space 15 through the broken portion, facilitating excessive oxidation of the silicon carbide particle surfaces. The cross-sectional area ratio of the linear holes 22 is preferably 75% or less, and more preferably 70% or less.

[0073] (f) Thickness of Partition Walls The thickness of the partition walls 21 of the sagger is preferably 0.1 to 0.5 mm. This allows the ambient gas to be appropriately ventilated into the closed space 15, and the heat is not lost in heating the sagger, but is used more efficiently to heat the ceramic honeycomb formed body. This allows the firing time to be shortened without setting the firing temperature as high as before, thereby preventing excessive oxidation of the silicon carbide particle surfaces.

[0074] If the thickness of the partition wall 21 of the sagger is less than 0.1 mm, the amount of oxidizing atmosphere gas flowing from the linear holes 22 through the partition wall 21 into the closed space 15 will be too large, causing excessive oxidation of the silicon carbide particle surfaces. Furthermore, the strength of the sagger will be reduced, making it more susceptible to breakage during handling. In a broken sagger, the oxidizing atmosphere gas will flow into the closed space 15 from the broken portion, causing excessive oxidation of the silicon carbide particle surfaces. The thickness of the partition wall 21 is preferably 0.15 mm or more, and more preferably 0.20 mm or more.

[0075] On the other hand, if the thickness of partition wall 21 exceeds 0.5 mm, the heat capacity of the sagger increases, and a large amount of heat is lost to heat the sagger, making it necessary to set a higher firing temperature and a longer firing time, which leads to excessive oxidation of the surfaces of the silicon carbide particles. The thickness of partition wall 21 is preferably 0.45 mm or less, and more preferably 0.40 mm or less.

[0076] (4) Assembly For example, when assembling the second sagger 200 shown in FIG. 2, multiple ceramic honeycomb molded bodies 5 are placed on the bottom plate 11, side plates 12 are erected on each side of the bottom plate 11, and a cover plate 13 is placed on the top of the side plate 12. When forming a sagger assembly 201 consisting of multiple tiers of saggers 201a and 201b as shown in FIG. 3, spacers 3 are placed on the four corners of the bottom surface of the cover plate 13 of the first tier sagger 201a, and the second tier sagger 201b is similarly formed on top of that. The third and subsequent tiers of saggers can be assembled in a similar manner. When spacers 3 are placed on the four corners of the bottom surface of the bottom plate 11 of the first tier sagger 201a as shown in FIG. 4, the first tier sagger 201a is formed on the spacers 3, and the second tier sagger 201b is similarly formed on the cover plate 13 of the first tier sagger 201a with the spacers 3 interposed therebetween.

[0077] When placing each sagger 201a, 201b on a heat-resistant ceramic base plate 4 as shown in Figure 5, the first base plate 4 is placed on the spacer 3, the first sagger 201a is formed on the first base plate 4, the second base plate 4 is placed on the cover plate 13 of the sagger 201a via the spacer 3, and the second sagger 201b is formed on the second base plate 4 in the same manner as above.

[0078] [6] Manufacturing of ceramic honeycomb structure The ceramic honeycomb formed body is placed in a sagger and fired in an oxidizing gas atmosphere (e.g., air) at a temperature of 1100 to 1350°C for 0.5 to 5 hours. This produces an oxide-bonded silicon carbide-based ceramic honeycomb structure 50 having numerous flow channels 53, 54 separated by porous partition walls 52, as shown in Figure 8.

[0079] [7] Manufacturing of Ceramic Honeycomb As shown in Figures 8 and 9, plugging portions 56b are formed at the open ends of the first flow paths 53 of a silicon carbide-based ceramic honeycomb structure 50 on the second end face 55b side, and plugging portions 56a are formed at the open ends of the second flow paths 54 adjacent to the first flow paths 53 on the first end face 55a side, thereby obtaining a honeycomb segment 51 having plugging portions. As the plugging material used to form the plugging portions, a slurry containing silicon carbide particles is preferably used. Note that the plugging portions may be formed before firing the silicon carbide-based ceramic honeycomb structure.

[0080] After applying the bonding material paste to the outer peripheral wall surface of each honeycomb segment 51, the outer peripheral wall surfaces of the multiple honeycomb segments 51 are pressed together via the bonding material paste as shown in Fig. 10 to integrally bond the multiple honeycomb segments 51 via the bonding material layer 530, and the bonding material layer 530 is then dried. The bonding material paste preferably contains silicon carbide particles and colloidal silica. Next, the resulting mixture is fired at a temperature of 1000 to 1400°C to obtain a bonded honeycomb segment body.

[0081] The outer periphery of the obtained honeycomb segment bonded body is machined into a circle using a lathe, and then coated with an outer skin material containing silicon carbide particles and inorganic particles (colloidal silica) to form an outer wall 510, and dried to obtain the silicon carbide-based ceramic honeycomb filter 500.

[0082] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[0083] Example 1 (1) Production of Molded Body 90.9% by mass of silicon carbide particles (median particle size: 40 μm) as aggregate, 9.1% by mass of alumina particles (median particle size: 5 μm) and magnesium hydroxide particles (median particle size: 3 μm) as inorganic binders, and hydroxypropyl methylcellulose as organic binder were mixed, and the resulting mixture was kneaded with water to prepare a plastic clay. This clay was extruded from a honeycomb structure molding die of a screw molding machine and then dried in a hot air dryer at 120 °C for 2 hours to obtain 20 ceramic honeycomb molded bodies with a square cross section, 34 mm on a side, and 304 mm in length.

[0084] (2) Sagger Manufacturing and Arrangement of Compacts A cordierite-forming raw material powder having a chemical composition of 50% by mass of SiO2, 35% by mass of Al2O3, and 15% by mass of MgO was prepared using a powder of cordierite-forming raw materials (kaolin, talc, silica, alumina, and aluminum hydroxide). To this was added methyl cellulose and hydroxypropyl methyl cellulose as organic binders, a lubricant, and a foamed resin as a pore-forming agent. After thorough dry mixing, water was added and the mixture was thoroughly kneaded to prepare a plasticized ceramic clay.

[0085] The ceramic clay was extruded from a honeycomb structure forming die of a screw extrusion machine, dried, and then fired at a maximum holding temperature of 1400°C. The obtained sintered body had a honeycomb structure with numerous linear pores 22 separated by porous partition walls composed mainly of cordierite, and had a density of 0.370 g / cm 3 the bulk density of 1.27 mm, a partition wall porosity of 58%, a median pore diameter d50 of 13 μm, a d10 of 3 μm, a d90 of 22 μm, a partition wall thickness of 0.305 mm, a partition wall pitch of 1.575 mm, linear pores which were square with a side of 1.27 mm and had a circle-equivalent diameter (inner diameter) converted from the cross-sectional area of ​​1.43 mm, and a linear pore cross-sectional area ratio of 65%.

[0086] The sintered body was cut to prepare two sets each of bottom plate 11 and cover plate 13 shown in Fig. 2, and side plates 212-1 and 212-2 shown in Fig. 6. Bottom plate 11 had dimensions of 410 mm long x 580 mm wide x 30 mm thick, and cover plate 13 had dimensions of 410 mm long x 580 mm wide x 20 mm thick. Side plate 212-1 had dimensions of 20 mm wide x 50 mm high x 540 mm long, and side plate 212-2 had dimensions of 20 mm wide x 50 mm high x 410 mm long.

[0087] In each of the bottom plate 11 and the cover plate 13, the linear holes 22 extended horizontally (perpendicular to the thickness direction), and the ends of the linear holes 22 did not open to the inner surfaces 11a, 13a that constitute the closed space 15. On the other hand, as shown in Figure 6, the linear holes 22 in the side plate 212-1 did not have ends that opened to the inner surface 12a that constitutes the closed space 15, but the linear holes 22 in the side plate 212-2 had ends 22a that opened to the inner surface 12a that constitutes the closed space 15. Therefore, all of the ends 22a of the linear holes 22 in the side plate 212-2 were sealed with a ceramic material having the same composition as the sagger to form sealed ends 22b. Therefore, the proportion of sealed ends 22b to all ends (the sum of the open ends 22a and sealed ends 22b) of the linear holes 22 in the side plates 212-1 and 212-2 was 100%. Therefore, the ratio of the total cross-sectional area of ​​the linear holes 22 communicating between the outside of the sagger and the closed space 15 to the total area of ​​the inner surface of the sagger facing the closed space 15 was 0%.

[0088] As shown in Fig. 4, ten ceramic honeycomb formed bodies 5 were placed on a bottom plate 11 placed on 30 mm high spacers 3 arranged at the four corners, four side plates 212-1 and 212-2 shown in Fig. 6 were arranged on the sides of the bottom plate 11, and a cover plate 13 was placed on the side plates 212-1 and 212-2 to assemble a first sagger 201a. Next, 30 mm high spacers 3 were arranged at the four corners of the bottom surface of the cover plate 13 of the first sagger 201a, and a second sagger 201b containing ten ceramic honeycomb formed bodies 5 was assembled in the same manner, thereby obtaining a two-tiered sagger assembly 202.

[0089] (3) Firing of Ceramic Honeycomb Formed Body The sagger assembly 202 containing a total of 20 ceramic honeycomb formed bodies 5 was placed in a firing furnace and fired in an air atmosphere at 1300° C. for 2 hours.

[0090] (4) Measurement of honeycomb structure characteristics (a) Thermal expansion coefficient Test pieces with a cross section of 4.5 mm × 4.5 mm and a length of 50 mm were cut out from the obtained honeycomb structure so that the longitudinal direction was approximately aligned with the flow path direction. Using a compression load / differential expansion type thermomechanical analyzer TMA (Thermo Plus, manufactured by Rigaku Holdings Corporation), the increase in longitudinal length was measured when the honeycomb structure was heated from room temperature to 800°C at a heating rate of 10°C / min while applying a constant load of 20 g, and the average thermal expansion coefficient between 40 and 800°C was calculated. As a result, the thermal expansion coefficient of the honeycomb structure fired using the sagger assembly 202 of Example 1 was 45.5 × 10 -7 / ℃.

[0091] (b) Deformation The deformation (deflection) δ in the width direction of the ceramic honeycomb formed body due to firing was measured as shown in FIG. 11, and the ratio of the deformation δ to the length of the honeycomb structure (deformation / total length) was calculated to be 2.0×10 -3 It was.

[0092] Example 2 Twenty ceramic honeycomb formed bodies were produced by the same method as in Example 1. Furthermore, as shown in FIG. 5 , a sagger assembly 203 was assembled in the same manner as in Example 1, except that the bottom plates 11, 11 of the saggers 201a, 201b of each stage were placed on a mullite bottom plate 4 (length 580 mm × width 410 mm × thickness 15 mm). The 20 ceramic honeycomb formed bodies were fired under the same conditions as in Example 1. The bottom plate 4 had a porosity of 38% and was not substantially deformed by firing. Therefore, the bottom plates 11, 11 were also not substantially deformed by firing. The thermal expansion coefficient of the resulting honeycomb structure was 45.5 × 10 -7 / °C, and the ratio of deformation δ (deformation / total length) is 3.0 × 10 -4 It was less than.

[0093] Comparative Example 1 Twenty ceramic honeycomb formed bodies produced by the same method as in Example 1 were placed in a sagger assembly 202 of the same shape and size as in Example 1 except that they were made of porous mullite without linear pores, and fired under the same conditions as in Example 1. The resulting honeycomb sintered bodies were incompletely fired.

[0094] As is clear from Examples 1 and 2, the silicon carbide-based ceramic honeycomb structures manufactured using the saggers of the present invention had a good thermal expansion coefficient and a small deformation amount δ. In particular, in Example 2, in which each stage of saggers was placed on a heat-resistant ceramic base plate 4, the deformation amount of the obtained honeycomb sintered body was smaller than that of Example 1. On the other hand, in Comparative Example 1, a lot of heat was lost in heating the saggers, and the ceramic honeycomb formed body was not heated sufficiently, so that firing was not completed within the same firing time as in Example 1.

[0095] 100, 200: sagger 201, 202, 203: sagger assembly 201a, 201b: saggers of each stage 11: bottom plate 11a, 12a, 13a, 14a, 14b: inner surface facing closed space 12, 121, 122, 123, 124, 125, 212-1, 212-2: side plate 13: cover plate 14: bottom member 141: bottom 142: side wall 15: closed space 21: partition wall of sagger 22: linear hole 22a: open end of linear hole 22b: sealed end of linear hole 3: spacer 4: heat-resistant ceramic base plate 5: ceramic honeycomb formed body 50, 51: ceramic honeycomb structure (honeycomb segment) 52: partition wall of ceramic honeycomb structure 53: First flow path 54: Second flow path 55a: First end face 55b: Second end face 56a: Plugging portion of first end face 56b: Plugging portion of second end face 500: Ceramic honeycomb filter 510: Peripheral wall 530: Bonding material layer

Claims

1. A method for manufacturing a silicon carbide-based ceramic honeycomb structure, comprising the steps of placing a ceramic honeycomb formed body containing an aggregate made of silicon carbide particles and an inorganic binder containing alumina source particles and / or magnesia source particles in a sagger and firing the body in an oxidizing gas atmosphere, characterized in that a member constituting the sagger has a honeycomb structure having a large number of linear holes extending in one direction and separated by porous partitions, the sagger has a closed space for accommodating the ceramic honeycomb formed body, and the ratio of the total cross-sectional area of ​​the linear holes connecting the outside of the sagger to the closed space to the total area of ​​the inner surface of the sagger facing the closed space is 0 to 5%.

2. A method for producing a silicon carbide-based ceramic honeycomb structure according to claim 1, characterized in that the sagger does not have any linear holes communicating between the outside and the closed space.

3. A method for manufacturing a silicon carbide-based ceramic honeycomb structure as described in claim 1, characterized in that a portion of the linear holes have ends on the inner surface of the sagger, and the linear holes having ends on the inner surface consist of (a) linear holes connecting the outside of the sagger with the closed space and (b) linear holes not connecting the outside of the sagger with the closed space, the ends of the linear holes (b) are sealed on the inner surface side and / or the outer surface side of the sagger, and the ratio of the linear holes (b) to the linear holes having ends on the inner surface is 20% or more.

4. A method for producing a silicon carbide ceramic honeycomb structure according to claim 1, characterized in that the inner diameter of said linear holes is 1.35 to 1.60 mm.

5. The bulk density of the sagger is 0.15 to 0.75 g / cm 3 2. The method for producing a silicon carbide based ceramic honeycomb structure according to claim 1, wherein the silicon carbide based ceramic honeycomb structure is a silicon carbide based ceramic honeycomb structure.

6. A method for producing a silicon carbide-based ceramic honeycomb structure according to claim 1, characterized in that the porosity of the partition walls of the sagger is 35 to 70%.

7. A method for producing a silicon carbide-based ceramic honeycomb structure according to claim 1, characterized in that the median pore size of the partition walls of the sagger is 3 to 25 μm.

8. A method for producing a silicon carbide-based ceramic honeycomb structure according to claim 1, characterized in that the partition walls of the saggers have a thickness of 0.1 to 0.5 mm.

9. A method for manufacturing a silicon carbide ceramic honeycomb structure according to claim 1, characterized in that the cross-sectional area ratio of said linear holes in said sagger is 50 to 80%.

10. A method for manufacturing a silicon carbide-based ceramic honeycomb structure as described in claim 1, characterized in that the sagger is composed of a bottom plate, a side plate and a cover plate, and the linear holes extend horizontally within the bottom plate, side plate and cover plate.

11. A method for manufacturing a silicon carbide-based ceramic honeycomb structure according to claim 1, characterized in that the partition walls of the saggers are made of ceramics containing as a main component at least one material selected from the group consisting of cordierite, alumina, mullite, silicon carbide and silicon nitride.

12. A method for producing a silicon carbide based ceramic honeycomb structure according to claim 1, characterized in that the sagger is placed on a heat resistant ceramic base plate.

13. A method for producing a silicon carbide based ceramic honeycomb structure according to claim 11, characterized in that the heat-resistant ceramic base plate is composed mainly of mullite or alumina.

14. A method for producing a silicon carbide ceramic honeycomb structure according to claim 11, wherein the heat-resistant ceramic base plate has a porosity of 40% or less.

15. A method for manufacturing a silicon carbide-based ceramic honeycomb structure as described in claim 1, characterized in that a sagger assembly is used having multiple tiers of saggers, with a heat-resistant ceramic base plate placed under the bottom plate of each tier of saggers.

16. A silicon carbide-based ceramic honeycomb structure obtained by kneading ceramic particles containing an aggregate consisting of silicon carbide particles, an inorganic binder containing alumina source particles and magnesia source particles, and an organic binder with water to obtain a clay, extruding the resulting clay into a honeycomb shape, drying the extruded clay to form a ceramic honeycomb formed body, and firing the ceramic honeycomb formed body, wherein the firing is carried out by placing the ceramic honeycomb formed body in a sagger, the member constituting the sagger has a honeycomb structure having a large number of linear holes extending in one direction and separated by porous partitions, the sagger has a closed space that contains the ceramic honeycomb formed body, and the ratio of the total cross-sectional area of ​​the linear holes connecting the outside of the sagger to the closed space to the total area of ​​the inner surface of the sagger facing the closed space is 0 to 5%.

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