JP7151295B2 - Manufacturing method of ceramic honeycomb filter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a ceramic honeycomb filter used for purifying exhaust gas containing particulate matter discharged from a diesel engine or the like.

Exhaust gas from diesel engines contains PM (particulate matter), the main components of which are carbonaceous soot and SOF (soluble organic fraction) composed of high-boiling hydrocarbons. If this is released into the atmosphere, it may adversely affect the human body and the environment. For this reason, a ceramic honeycomb filter for trapping PM (hereinafter, the ceramic honeycomb filter is abbreviated as a "honeycomb filter") has been conventionally installed in the middle of an exhaust pipe of a diesel engine. An example of a honeycomb filter that collects and purifies PM in exhaust gas is shown in FIGS. 1(a) and 1(b). The honeycomb filter 10 comprises a ceramic honeycomb structure composed of a porous partition wall 2 forming a large number of outflow-side plugged channels 3 and inflow-side plugged channels 4 and an outer peripheral wall 1, an outflow-side plugged channel 3 and It consists of an upstream sealing portion 5a and a downstream sealing portion 5b that alternately seal an exhaust gas inflow side end face 6 and an exhaust gas outflow side end face 7 of the inflow side sealed flow path 4 in a checkered pattern. The outer peripheral wall 1 of the honeycomb filter is held by a holding member (not shown) made of metal mesh, ceramic mat, or the like so as not to move during use. are placed.

In the honeycomb filter 10, purification of exhaust gas is performed as follows. Exhaust gas flows in from the outflow-side sealed channel 3 opening at the exhaust gas inflow-side end surface 6, as indicated by the dotted arrow. PM contained in the exhaust gas is captured when passing through the partition wall 2, more specifically, when passing through communication holes formed by mutually communicating pores existing on the surface and inside of the partition wall 2. The purified exhaust gas flows out from the inflow-side sealed flow path 4 opening at the exhaust gas outflow-side end surface 7 and is released into the atmosphere.

A honeycomb filter is manufactured by the following steps. First, for example, a cordierite-forming raw material powder, a molding aid, a pore-forming agent, and water as ceramic raw materials are mixed and kneaded to obtain a ceramic clay. This ceramic clay is extruded into a honeycomb shape through a mold to obtain a formed body having a honeycomb structure having a large number of flow paths partitioned by partition walls. The compact is placed in a drying furnace to evaporate and dry the moisture in the compact, and then placed in a calcining furnace to remove molding aids and the like from the compact, followed by calcination. As a result, a honeycomb structure (fired body) having a predetermined shape and strength and having a large number of flow paths partitioned by porous partition walls is obtained. After filling predetermined channel ends of the obtained honeycomb structure with the plugging material slurry, it is dried and fired to form plugging portions, whereby the honeycomb filter 10 is obtained. An outer peripheral wall is formed on the outer periphery of the honeycomb filter for the purpose of further improving its mechanical strength.

In the manufacture of the honeycomb filter, when the plugging material slurry is filled into the channel ends and then dried and fired, the end faces and the center of the honeycomb fired body having the plugging material at the channel ends are formed. Thermal stress is generated due to the temperature difference between the two, and in particular, the temperature difference between the peripheral part of the end face of the honeycomb fired body and the central part tends to increase, and as shown in FIG. There is a problem that cracks 8 are generated in partition walls (intersecting portions) between plugging portions.

Japanese Patent Application Laid-Open No. 62-202870 (Patent Document 1) discloses a method of firing a honeycomb molded body by abutting a horse chestnut (sole plate) on both open end faces and using a horse chestnut having a ceramic honeycomb structure as at least one of the horse chestnuts. It is described that this method can suppress the local temperature rise of the upper end surface of the honeycomb molded body and prevent the occurrence of cuts. It is described that by making the shape of the horse chestnut into a honeycomb structure, the weight can be reduced, the frictional force with the honeycomb formed body can be reduced during firing, and the gas generated during firing can be easily diffused. Furthermore, it is described that a similar effect can be obtained by forming a chamfered portion on the outer periphery of the horseshoe and having grooves on the contact surface.

Japanese Patent Application Laid-Open No. 62-252886 (Patent Document 2) discloses that when a honeycomb molded body is fired, it is made of a honeycomb-structured ceramic plate having flow channels in the vertical direction, and is placed on a horse chestnut having a chamfered portion on the upper edge. A method for placing the honeycomb molded body is disclosed. Patent Literature 2 further discloses a configuration having a groove in the upper portion of the horseshoe. It is described that the use of such a horse-chestnut solves the problem of breakage of cell ribs due to the frictional resistance generated at the contact surface between the formed honeycomb body and the horse-chestnut during shrinkage or expansion during firing.

Japanese Patent Application Laid-Open No. 07-208873 (Patent Document 3) is composed of a ceramic honeycomb plate having a flow path connecting to an upper end face and a lower end face, and has a convex step portion inside at least one of the end faces. It discloses a ceramic firing table (tochi), which is said to maximize stress relief during firing and prevent cracks from occurring.

International Publication No. 2006/035674 (Patent Document 4) discloses a base plate for firing in which the main component of the crystal phase after firing is the same as that of the body to be fired, and the surface roughness Ra of the contact surface with the body to be fired is It discloses a firing floor plate of 8 to 50 μm, and a firing floor plate in which the outer peripheral corners of the contact surface with the object to be fired are chamfered in the range of 3 to 30 mm. In Patent Document 4, by using these firing sole plates, sticking between the body to be fired and the firing sole plate (tochi) is greatly suppressed, and cell breakage and cell chipping, and expansion/contraction behavior of the honeycomb fired body are prevented. It is described that it prevents firing chipping, cell distortion, cracks, deformation and poor reaction caused by mismatch.

In International Publication No. 2017/033774 (Patent Document 5), a honeycomb filter is manufactured by filling a plugging material into a predetermined flow passage end portion of a honeycomb-shaped formed body and firing the formed body and the plugging portions. In the manufacturing method, the molded body filled with the plugging material at the time of firing is placed with the first end surface facing downward and the second end surface facing upward, and the upper end surface member containing the ceramic raw material is placed on the second end surface. Disclosed is a method of firing in place. In Patent Document 5, the stress concentration caused by the temperature gradient at the peripheral edge of the upper end surface during temperature rise is transferred to the peripheral edge of the upper end surface member by firing with the upper end surface member placed thereon. As a result, it is possible to prevent cracks occurring inside the fired honeycomb filter.

International Publication No. 2008/044508 (Patent Document 6) discloses that plugging portions made of a cordierite-forming raw material are injected into predetermined flow paths of a cordierite ceramic honeycomb fired body having an outer diameter of 150 mm or more and dried. , the step of firing the plugged portions, wherein the firing step includes a step of raising the temperature, a step of holding the temperature, and a step of lowering the temperature, and heating from 800°C to the maximum holding temperature in the step of raising the temperature It discloses a method for producing a cordierite ceramic honeycomb filter characterized by having a heating rate of 70 to 500° C./hr.

JP-A-62-202870 JP-A-62-252886 JP-A-07-208873 WO 2006/035674 WO2017/033774 WO 2008/044508

The inventions described in these Cited Documents 1 to 5 relate to a member and/or a firing sole plate (tochi) to be placed on the upper end face of the honeycomb molded body when firing the unfired honeycomb molded body, The member and the base plate for firing suppress the local temperature rise of the honeycomb formed body, prevent the occurrence of cuts due to stress concentration, and reduce the frictional force between the honeycomb formed body and the horse chestnut (sole plate). It is used for the purpose of preventing the occurrence of cuts, cracks, etc. However, as the thickness of the partition walls becomes thinner due to the increase in the size of the honeycomb structure, the members and the base plate for firing described in these cited documents suppress the local temperature rise of the honeycomb formed body and prevent breakage due to stress concentration. There have been cases where the effect of preventing the occurrence of is not sufficiently obtained. In addition, in the manufacturing method described in Cited Document 6, since the plugging material slurry is filled into a predetermined flow path end portion of a fired body having a honeycomb structure, dried, and then fired, the plugging portions and the eyes are fired at the time of firing. Cracks may occur in the partition (intersecting portion) between the sealing portion, and the sole plate for firing (horse chestnut) described in these Cited Documents 1 to 5 could not obtain a sufficient preventive effect. In particular, this problem was serious when the temperature-lowering rate in the temperature-lowering process after firing was increased in order to increase production efficiency.

Accordingly, an object of the present invention is to provide a molded body having a honeycomb structure, or a fired body obtained by firing the molded body, by filling a predetermined channel end portion with a plugging material slurry and drying and then firing. An object of the present invention is to provide a honeycomb filter manufacturing method capable of preventing cracks from occurring in partition walls (intersecting portions) between plugging portions and plugging portions.

As a result of intensive research in view of the above object, the present inventors found that when a predetermined flow path of a fired body having a honeycomb structure is filled with a plugging material slurry and the plugged slurry is fired, The stress generated by the temperature difference between the end face and the inside is the cause of the crack, and in order to prevent a sudden temperature drop on the end face side during cooling, it is effective to place a heat insulating material on the end face. The inventors have found that it is effective and arrived at the present invention.

That is, the method for manufacturing a honeycomb filter of the present invention includes a molded body having a honeycomb structure composed of a large number of flow paths partitioned by porous partition walls, or a fired body obtained by firing the molded body at predetermined flow path ends. A method for manufacturing a ceramic honeycomb filter in which plugging portions are formed by filling the plugging material slurry in the portions, drying and firing the slurry, the method comprising:
Firing of the plugging material slurry is
One end face of the molded body or fired body filled with the plugging material slurry is turned up and the other end face is turned down, and a heat insulating member is placed on one end face,
The heat insulating member is characterized in that a ceramic honeycomb member having a large number of through holes partitioned by porous partition walls is provided with a sealing portion on at least one end face side of the through holes.

The heat insulating member has an opening that opens to the other end surface of the through hole having the sealing portion, and the heat insulating member is arranged such that the other end surface is in contact with one end surface of the molded body or the sintered body. is preferably placed.

It is preferable that the outer peripheral shape of the heat insulating member is larger than the outer peripheral shape of the molded body or the sintered body.

It is preferable that the heat insulating member has a length of 10 to 100 mm in the direction of the through hole.

It is preferable that the sealing portion provided in the heat insulating member has a depth of 1 to 60% from the one end surface of the through hole of the heat insulating member.

The sealing portion provided in the heat insulating member may be provided in all the through holes of the heat insulating member, or may be provided only in the through holes in the peripheral portion of the heat insulating member.

The fired body having the honeycomb structure is made of cordierite ceramic,
The plugging material slurry is preferably a slurry containing cordierite powder or a cordierite-forming raw material.

The sintering of the plugging material slurry has a temperature rising process, a holding process at the sintering temperature, and a temperature decreasing process, and the temperature decreasing rate in the temperature decreasing process is from the sintering temperature to the sintering temperature -300°C. is preferably 40 to 300° C./hr in the range of .

Firing of the plugging material slurry is preferably carried out in a continuous furnace.

According to the manufacturing method of the present invention, the plugging material slurry is filled into a predetermined flow path end portion of a molded body or fired body having a honeycomb structure, dried, and then fired. It is possible to reduce the occurrence of cracks in the partition walls (intersecting portions) between

Fig. 3 is a schematic cross-sectional view showing an example of a honeycomb filter perpendicular to the flow path; Fig. 2 is a schematic cross-sectional view showing an example of a honeycomb filter parallel to the flow path; FIG. 4 is a schematic cross-sectional view showing how cracks are generated when the plugging material is fired. FIG. 4 is a schematic cross-sectional view showing an example of a method of baking the plugging material. It is a schematic cross section which shows an example of a heat insulating member. FIG. 3 is a schematic cross-sectional view showing another example of a heat insulating member; FIG. 3 is a schematic front view showing another example of a heat insulating member; FIG. 10 is a schematic cross-sectional view showing still another example of a heat insulating member; FIG. 4 is a schematic cross-sectional view showing another example of the method of baking the plugging material. Fig. 2 is a front view schematically showing a state in which the ceramic honeycomb filter is placed on an apparatus for inspecting cracks in the ceramic honeycomb filter; Fig. 2 is a side view schematically showing a state in which the ceramic honeycomb filter is placed on an apparatus for inspecting cracks in the ceramic honeycomb filter; FIG. 4 is a schematic diagram showing measurement positions of cracks in a ceramic honeycomb filter.

[1] Manufacturing method of ceramic honeycomb filter After filling the plugging material slurry in the road end, it is dried and baked to form the plugging portion. That is, after firing the molded body having the honeycomb structure to prepare a fired body having the honeycomb structure, a plugging material slurry is filled and dried, and the dried plugging material is fired (first method), and a method (second method) in which the molded body having the honeycomb structure is filled with a plugging material slurry and dried, and then the molded body and the dried plugging material are fired at the same time. be. The method for manufacturing the ceramic honeycomb filter of the present invention will be described in detail below using the first method as an example.

(A) First method for manufacturing a ceramic honeycomb filter The first method for manufacturing a ceramic honeycomb filter according to the present invention comprises the steps of obtaining a formed body having a honeycomb structure, firing the formed body, and firing the body having a honeycomb structure. A step of obtaining a body (hereinafter also referred to as a “honeycomb fired body”), filling a predetermined flow path end portion of the fired body having the honeycomb structure with a plugging material slurry, drying, and plugging after drying A step of baking the sealing material to form plugging portions is included. In the first method of the present invention, the sintering of the plugging material is carried out by placing the sintered body filled with the plugging material slurry and dried with one end surface facing upward and the other end surface facing downward. A heat insulating member is placed on the end surface of the Here, the heat insulating member is characterized in that a sealing portion is provided on at least one end surface side of the through holes of a ceramic honeycomb member having a large number of through holes partitioned by porous partition walls. The heat insulating member has an opening that opens to the other end surface of the through hole having the sealing portion, and the heat insulating member is arranged such that the other end surface is in contact with one end surface of the molded body or the sintered body. is preferably placed.

(1) Step of obtaining a formed article having a honeycomb structure A formed article having a honeycomb structure is obtained by molding a clay obtained by mixing and kneading forming raw materials into a honeycomb shape using a molding die having forming grooves of a honeycomb structure. obtained by extrusion to The forming raw material is preferably obtained by mixing and kneading a ceramic raw material, a binder, water, and, if necessary, a forming aid, a pore-forming material, and the like. The ceramic raw material is not particularly limited, but a cordierite-forming raw material composed of a silica source raw material, an alumina source raw material, and a magnesia source raw material, alumina, silica, silicon nitride, silicon carbide, aluminum titanate, LAS, etc. can be used. can. Among them, cordierite-forming raw materials are preferably used. As cordierite-forming raw materials, silica, talc, kaolin, alumina, aluminum hydroxide, and the like can be used. Materials such as foamed resin and graphite can be used as the pore-forming material.

(2) Step of obtaining a fired body having a honeycomb structure The obtained shaped body is placed in a drying furnace to evaporate the moisture in the shaped body, and then placed in a firing furnace to remove molding aids and the like from the shaped body. Then bake. As a result, a fired body having a predetermined shape and strength and having a honeycomb structure with fine pores in the partition walls can be obtained. In order to further improve the mechanical strength of the fired body having such a honeycomb structure, it is preferable to form an outer peripheral wall on the outer periphery thereof. For example, when a cordierite-forming raw material is used as a ceramic raw material, the molded body is fired by heating to a firing temperature of 1350 to 1450°C at a rate of 2 to 100°C/hr and holding at the maximum temperature for 5 to 30 hours. , cooling to 1000°C at a rate of less than 100°C/hr.

(3) Step of Forming Plugged Portions As shown in FIGS. After the plugging material slurry is filled so as to be plugged alternately, the dried plugging material is dried and fired to form plugged portions, thereby obtaining a ceramic honeycomb filter. As shown in FIG. 3, the plugging material is fired by placing a fired body 12 filled with a plugging material slurry 11 and dried on a base plate 13 with one end face up and the other end face down. A heat insulating member 14 is placed on one end face of the sintered body 12 . The plugging material is fired in a state in which a heat insulating member 14 having a honeycomb structure (hereinafter also simply referred to as a heat insulating member) is placed on the fired body 12 filled with the plugging material slurry 11 and dried. , the top surface is prevented from being rapidly cooled during the cooling process, and the occurrence rate of cracks (see FIG. 2) caused by the temperature difference between the top surface and the inside can be reduced.

As the plugging material slurry to be filled in the flow paths of the fired body having the honeycomb structure, those used in conventional honeycomb filters can be applied, such as cordierite, alumina, mullite, silicon nitride, silicon carbide, LAS, and titanium. A ceramic material whose main crystal is at least one selected from the group consisting of aluminum oxide, titania, zirconia, and aluminum nitride can be used. The plugging portions are preferably made of the same material as that of the fired honeycomb body (ceramic honeycomb structure). In particular, when the fired body having the honeycomb structure is made of cordierite ceramic, it is most preferable because it is inexpensive, has excellent heat resistance and corrosion resistance, and has low thermal expansion, and the plugging material slurry is cordierite powder or cordierite. It is preferably a slurry containing a conversion raw material. These slurries are obtained by mixing and kneading a cordierite powder or cordierite-forming raw material with a binder, water, and, if necessary, a molding aid, a pore-forming material, and the like. It is preferable that the length of the plugging portion is appropriately set according to the cross-sectional area of the channel. The pore-sealing portion formed in the heat insulating member can also be formed using the same plugging material as that used to fill the flow paths of the fired body having the honeycomb structure.

In the step of firing the plugging material, when the fired body having the honeycomb structure with the plugging material at the ends is cooled in the temperature-lowering process, the cooling rate of the end face portions becomes higher than the cooling rate of the central portion. As a result, the end faces are rapidly cooled, and a temperature difference from the central part occurs, which may cause cracks due to thermal stress. In particular, the temperature difference between the peripheral portion of the end surface and the central portion tends to be large. Therefore, it is effective to prevent cracks from occurring, especially by preventing rapid cooling of the periphery of the end face. preferably large. "Equal to the outer peripheral shape" means that the heat insulating member has a peripheral shape that covers the range of 80 to 100% of the upper end surface of the fired body, and "larger than the outer peripheral shape" The heat insulating member has an outer peripheral shape that covers the entire upper end surface of the sintered body.

Here, as the floor plate 13, a plate made of alumina, silicon carbide, or the like, or a plate having holes or slits as necessary can be used. It is also preferable to place a baking table 20 on the floor plate 13 as shown in FIG. In this case, as the firing table 20, a honeycomb body such as a ceramic honeycomb molded body or a ceramic honeycomb fired body cut to a desired thickness can be used.

(i) Heat Insulation Member The heat insulation member is a ceramic honeycomb member having a large number of through holes partitioned by porous partition walls, and a sealing portion provided on at least one end face side of the through holes. The ceramic honeycomb member used as the heat insulating member may be an unfired honeycomb formed body, or may be a fired body after firing the honeycomb formed body. As shown in FIGS. 3 and 4, the heat insulating member 14 has a sealed portion 17 formed on the entire upper end surface of the through hole 16 of the ceramic honeycomb member 15, and the end surface on the side where the sealed portion 17 is formed (one side). The end face (the other end face 15b) on the opposite side of the end face 15a) has an opening 18 in which the through hole 16 is opened, and the other end face 15b is in contact with one end face of the fired body 12, that is, is sealed. It is preferable to place the heat insulating member 14 on the upper end surface of the sintered body 12 so that the end surface where the hole 17 is formed faces upward and the end surface of the through hole 16 on the opening 18 side contacts the upper end surface of the sintered body 12 . preferable. It is preferable that the outer peripheral shape of the heat insulating member is larger than the outer peripheral shape of the fired body.

The heat insulating member 14 having the structure in which the sealing portions 17 are formed on the upper end surfaces of the through holes 16 of the ceramic honeycomb member 15 in this way can be made lighter by adopting the honeycomb shape, and the sealing portions 17 allow the through holes 16 to be closed. By sealing one end of the through hole 16, a layer of air is formed in the through hole 16 where the sealing portion 17 is not formed, and has a high heat retaining effect. In addition, by forming the sealing portion 17 on the entire surface of the upper end surface of the through hole 16, when foreign matter floating in the firing furnace is generated, the foreign matter can be prevented from adhering to the fired body 12 having the honeycomb structure. .

In addition, by using the same material for the heat insulating member 14 as the fired body 12 having a honeycomb structure, it is possible to eliminate the difference in thermal expansion between the fired body 12 and the heat insulating member 14 during firing. It is possible to prevent scratches and cracks from occurring due to friction with the heat insulating member 14. Due to the heat-retaining effect of the heat-retaining member 14, even if the cooling rate during firing is increased, cracks are less likely to occur, making it possible to shorten the manufacturing time.

The heat insulating member 14 in which the sealing portion 17 is formed on the upper end surface side (one end surface 15a side) of the through hole 16 of the ceramic honeycomb member 15 is the depth of the sealing portion 17 provided in the heat insulating member 14 (the sealing portion 17 length in the direction of the through hole) is preferably 1 to 60%, more preferably 1 to 50%, of the thickness of the heat insulating member (total length of the through hole).

As shown in FIG. 4, the heat insulating member 14 may be configured by providing the sealed portions 17 on the entire surface of the ceramic honeycomb member 15. However, as shown in FIGS. The heat insulating member 14' may be formed by forming the sealing portion 17 only in the peripheral portion of the member 15. As shown in FIG. As described above, in the step of firing the plugging material, when the fired body 12 having the honeycomb structure is cooled, the cooling rate of the peripheral portion is higher than that of the central portion. The heat insulating member 14' having the sealing portion 17 provided only on the peripheral portion is effective in enhancing the heat insulating effect of the peripheral portion as compared with the central portion. When the sealing portions 17 are provided only in the peripheral portion of the ceramic honeycomb member 15, the ratio of the number of the through holes 16 in which the sealing portions 17 are provided is not particularly limited, but is preferably 30% to 90%.

Alternatively, as shown in FIG. 6, both end surfaces 15a and 15b of the ceramic honeycomb member 15 may be provided with sealed portions 17a and 17b to form a heat insulating member 14''. In this case, as shown in the figure, it is preferable to provide a gap 19 between one sealing portion 17a and the other sealing portion 17b.

The thickness (length in the through hole direction) of the heat insulating member is preferably 10 to 100 mm, more preferably 20 to 50 mm. If the thickness of the heat-retaining member is less than 10 mm, the strength of the heat-retaining member is insufficient and it may break during handling. Also, if it is too thick, it will occupy too much space in the firing furnace in a batch type furnace, reducing the number of firings that can be fired and lowering production efficiency. There is

The ceramic honeycomb member 15 constituting the heat insulating member preferably has a partition wall thickness of 0.1 to 0.5 mm, a cell density of 100 to 600 cells/in 2 , and a porosity after firing of 40 to 70%. The ceramic honeycomb member 15 may be produced using a ceramic honeycomb structure.

(iii) Firing Firing of the plugging material is preferably carried out at 1350 to 1450° C. when the plugging material is made of a cordierite-forming raw material. Firing can be carried out in a batch furnace, but is preferably carried out in a continuous furnace. A continuous furnace is one in which a material to be treated is continuously charged from one port of the furnace and heat-treated while being conveyed at a predetermined speed. The interior of the furnace is heated to a predetermined temperature for each zone, and the temperature of the workpiece changes as the workpiece is conveyed through the furnace. is done. The rate of temperature increase, the holding time at the sintering temperature, and the rate of temperature decrease are determined by the temperature setting and conveying speed of each zone. The effects of the present invention are more effective when the temperature drop rate in the temperature drop process is 40 to 300°C/hr in the range from the firing temperature to the firing temperature -300°C.

A continuous furnace is one in which the material to be treated is continuously charged from one port of the furnace and conveyed at a predetermined speed. In particular, when firing the plugging material filled in the end of the flow path of the ceramic honeycomb fired body, the shock and vibration during transportation are difficult to transmit so that the ceramic honeycomb fired body will not crack due to vibrations and impacts generated during transportation. A continuous furnace of conveyor type is preferably used. Belts, hangers, rollers, and the like can be used for conveyor type transport. Among them, in the roller hearth type using rollers, since the ceramic honeycomb fired body placed on a tray or the like is transported on rotating rollers arranged at an appropriate pitch, the rotation of the rollers can be set arbitrarily, and the It is easy to adjust the heating rate and the cooling rate.

(B) Second method of manufacturing a ceramic honeycomb filter The second method of the present invention for manufacturing a ceramic honeycomb filter comprises the steps of obtaining a molded body having a honeycomb structure, and A step of filling the road end with the plugging material slurry, drying, and firing the molded body having the honeycomb structure and the plugging material to form a honeycomb fired body having plugged portions. In the second method of the present invention, the molded body and the plugging material are fired by placing the molded body filled with the plugging material slurry with one end face up and the other end face down. A heat insulating member is placed on one end surface of the molded body. Here, the same heat insulating member as used in the first manufacturing method can be used.

That is, in the second manufacturing method, the plugging material slurry is directly filled into the formed body having the honeycomb structure without going through the step of firing the formed body having the honeycomb structure to produce the fired body having the honeycomb structure. In this method, the molded body and the plugging material are dried and fired at the same time. Therefore, the manufacturing method is the same as the first manufacturing method except that the plugging material slurry is filled into the molded body having the honeycomb structure without performing the step of manufacturing the fired body having the honeycomb structure.

The present invention will be explained in more detail by examples, but the present invention is not limited to them.

Example 1
A fired body having a honeycomb structure (honeycomb fired body) was manufactured by a known method. First, powders of kaolin, talc, silica, alumina and aluminum hydroxide were used to prepare cordierite with a chemical composition of 50% by weight _SiO2 , ₃₅ % by weight _Al2O3 and 15% by weight MgO. Raw material powders were prepared (these contents can be adjusted in the range of SiO ₂ : 48-52% by mass, Al ₂ O ₃ : 33-37% by mass, and MgO: 12-15% by mass). Methyl cellulose and hydroxypropyl methyl cellulose as binders, a lubricant, and a foamed resin as a pore-forming agent were added to the mixture, and the mixture was thoroughly mixed in a dry process. . This kneaded material was extruded and cut to obtain a molded body having a honeycomb structure. After drying, the compact was fired at a maximum holding temperature of 1400° C. to obtain a cordierite-based ceramic honeycomb fired body. This ceramic honeycomb fired body had an outer diameter of 150 mm, a length of 202 mm, a partition wall thickness of 0.3 mm, a partition wall pitch of 1.5 mm, and a porosity of 61%.

Next, as shown in FIGS. 1(a) and 1(b), a plugging material slurry was alternately applied in a checkered pattern to the flow paths of both end surfaces of the honeycomb fired body by a known method, and a length of 3.0 to 8.0 mm was applied. filled and dried. The plugging material slurry was prepared by adjusting powders of kaolin, talc, silica, and alumina so that the chemical composition was 50% by mass of _SiO2 , 35% by mass of _{Al2O3 ,} and 15% by mass of MgO. Methyl cellulose, a lubricant, and water were added to the elite-generating raw material powder to be used.

As shown in FIG. 3, a fired body 12 filled with plugging material slurry and dried is placed on a base plate 13 made of silicon carbide and having a thickness of 20 mm. A heat insulating member 14 having the shape shown is placed, and the plugging material is fired at a maximum holding temperature of 1390°C using a roller hearth type continuous furnace (roller hearth kiln). It was cooled down to 300°C at a cooling rate of 90°C/hr to fabricate a cordierite ceramic honeycomb filter. The heat insulating member was obtained by cutting a cordierite ceramic honeycomb fired body (outer diameter 180 mm, partition wall thickness 0.3 mm, partition pitch 1.8 mm, porosity 61%) to a thickness of 25 mm, and all through-holes A sealing portion 17 was formed on one end surface 15a side of the heat insulating member to a depth of 5% of the thickness of the heat insulating member. The pore-sealing portion was formed using the same plugging material slurry as described above.

Example 2
Instead of the heat insulating member 14 used in Example 1, a heat insulating member 14' having a structure in which the sealing portion 17 is not formed in the central portion as shown in FIGS. 5(a) and 5(b) is used. A cordierite-based ceramic honeycomb filter was produced in the same manner as in Example 1, except that the plugging material was fired. The diameter of the portion where the sealing portion 17 is not formed is 35% of the diameter of the fired body 12, and the ratio of the number of through holes 16 provided with the sealing portion 17 is 88% of the total number of through holes. rice field.

Example 3
As shown in FIG. 7, partition walls cut to a thickness of 40 mm from the ceramic honeycomb fired body 12 were placed between the ceramic honeycomb fired body 12 filled with the plugging material slurry and the base plate 13, with a partition wall thickness of 0.3 mm and a partition wall pitch of 1.5. A cordierite-based ceramic honeycomb filter was produced in the same manner as in Example 1, except that the plugging material was fired on a firing table 20 having a honeycomb structure of 3 mm.

Comparative example 1
A cordierite ceramic honeycomb filter was produced in the same manner as in Example 1 except that the plugging material was fired without using the heat insulating member 14 .

200 pieces of each of the ceramic honeycomb filters of Examples 1 to 3 and Comparative Example 1 were produced, and the occurrence of cracks was inspected by the following method. 8(a) and 8(b) show a state in which the ceramic honeycomb filter 10 is placed on an inspection device 100 for inspecting cracks in the ceramic honeycomb filter. The inspection apparatus 100 includes a pedestal 101, fixing members 102a and 102b for placing the ceramic honeycomb filter 10 to be inspected provided on the pedestal 101 at a predetermined position, and one partition wall of the ceramic honeycomb filter 10. is arranged at a position facing the first transmitting side probe 103a for transmitting an acoustic signal in the direction in which the first transmitting side probe 103a extends, and from the first transmitting side probe 103a A first reception side probe 103b for receiving the transmitted acoustic signal through the one partition wall, and a position shifted by 90° from the first transmission side probe 103a, the other side of the ceramic honeycomb filter 10 A second transmitting probe 104a for transmitting an acoustic signal in the direction in which the partition extends, and a second transmitting probe 104a arranged at a position facing the second transmitting probe 104a. A second receiving probe 104b for receiving the acoustic signal transmitted from 104a through the other partition wall, a first transmitting probe 103a, a first receiving probe 103b, a second A cylinder 105 for contacting and separating the transmitting side probe 104a and the second receiving side probe 104b from the ceramic honeycomb filter 10, and supporting these transmitting side and receiving side probes so that they can be raised and lowered. and a support member 106 for

A ceramic honeycomb filter 10 to be inspected is placed on a pedestal 101 of an inspection device 100 with one end surface facing downward so as to abut on fixing members 102a and 102b provided on the pedestal 101. As shown in FIG. The first and second transmitting side probes 103a and 104a and the first and second receiving side probes 104a and 104b are moved to predetermined positions (first positions) by the support member 106, and the cylinder 105 is brought into contact with the ceramic honeycomb filter 10. An acoustic signal is transmitted from the first transmitting probe 103a at a frequency of 0.5 MHz, and the acoustic signal is received by the first receiving probe 103b. On the other hand, an acoustic signal is transmitted from the second transmitter probe 104a, and the acoustic signal is received by the second receiver probe 104b. After the measurement is completed, the ceramic honeycomb filter 10 is separated by the cylinder 105, moved to the second position by the supporting member 106, and the measurement is performed in the same manner. Inspection of the ceramic honeycomb filter 10 for cracks is carried out at positions 10 mm from both end faces of the ceramic honeycomb filter 10 (arrows a and f) and positions dividing the distance into 5 equal parts (arrows b to There are 6 points in e), and since each point was measured in orthogonal directions with two pairs of probes, a total of 12 points were measured.

The UT values (the ratio of the intensity of the acoustic signal received by the receiving probe to the intensity of the acoustic signal emitted by the transmitting probe) measured at 12 locations and the master product known to be defect-free in advance. The UT value was compared with the measured UT value, and if it was below the UT value of the master product even in one place, it was judged as NG. Here, when a crack occurs between the transmitting side probe and the receiving side probe, since the sound wave signal does not propagate through the cracked portion, the sound signal is greatly attenuated and the UT value becomes a low value. Therefore, it was determined that a ceramic honeycomb filter with a lower UT value than a defect-free master had cracks at that site.

Of the 200 ceramic honeycomb filters produced, the ratio of the ceramic honeycomb filters for which the UT value was lower than that of the defect-free master product was evaluated as the crack generation rate (NG rate). Example 2 was 1.0%, Example 3 was 0%, and Comparative Example 1 was 10%.

In addition, the end faces of the ceramic honeycomb filters were visually checked, and out of 200 ceramic honeycomb filters produced, the number of ceramic honeycomb filters with foreign substances adhering to the end faces was calculated as the end face foreign substance occurrence rate. %, 1.5% in Example 2, 0% in Example 3, and 8% in Comparative Example 1.

10 Honeycomb filter
1・・・peripheral wall
2... Porous partition wall
3... outflow side sealing channel
4・・・Inflow-side sealed flow path
5a・・・Upstream sealing part
5b・・・Downstream sealing part
6・・・Exhaust gas inflow side end face
7・・・Exhaust gas outflow end face
8 Crack
11 ... plugging material slurry
12... sintered body
13・・・Side plate
14,14',14''・・・Insulation material
15・・・Ceramic honeycomb member
16 ... through hole
17,17a,17b・・・sealing part
18... opening
19 Gap
20・・・Baking table
100 Inspection device
101 Pedestal
102a, 102b・・・Fixing member
103a ... the first transmitting side probe
103b ... the first receiving probe
104a . . . second transmitting probe
104b ... second receiving probe
105 Cylinder
106 Support member

Claims (8)

A plugging material slurry is filled into predetermined channel ends of a molded body having a honeycomb structure consisting of a large number of channels partitioned by porous partition walls, or a fired body obtained by firing the molded body, and then dried. and firing to manufacture a ceramic honeycomb filter having plugging portions formed,
The sintering of the plugging material slurry is carried out by placing a molded body or a sintered body filled with the plugging material slurry with one end surface facing upward and the other end surface facing downward, and placing a heat insulating member on one end surface. one end surface of the heat insulating member is placed upward and the other end surface is downward;
The heat insulating member comprises a ceramic honeycomb member having a large number of through holes partitioned by porous partition walls, and a sealing portion provided on at least one end surface side of the through holes of the heat insulating member ,
The heat insulating member has an outer peripheral shape that covers 80 to 100% of one end face of the molded body or fired body, or an outer periphery that completely covers one end face of the shaped body or fired body. has the shape
A method for manufacturing a ceramic honeycomb filter , wherein the sealing portions provided in the heat insulating member are provided in all the through holes of the heat insulating member . A plugging material slurry is filled into predetermined channel ends of a molded body having a honeycomb structure consisting of a large number of channels partitioned by porous partition walls, or a fired body obtained by firing the molded body, and then dried. and firing to manufacture a ceramic honeycomb filter having plugging portions formed,
The sintering of the plugging material slurry is carried out by placing a molded body or a sintered body filled with the plugging material slurry with one end surface facing upward and the other end surface facing downward, and placing a heat insulating member on one end surface. one end surface of the heat insulating member is placed upward and the other end surface is downward;
The heat insulating member comprises a ceramic honeycomb member having a large number of through holes partitioned by porous partition walls, and a sealing portion provided on at least one end surface side of the through holes of the heat insulating member,
The heat insulating member has an outer peripheral shape that covers 80 to 100% of one end face of the molded body or fired body, or an outer periphery that completely covers one end face of the shaped body or fired body. has the shape
The sealing portion provided in the heat insulating member is provided only in the through holes in the peripheral portion of the heat insulating member, and the ratio of the number of through holes provided with the sealing portion is 30% or more. A method for manufacturing a ceramic honeycomb filter . In the method for manufacturing a ceramic honeycomb filter according to claim 1 or 2 ,
The heat insulating member has an opening that opens to the other end surface of the through hole having the sealing portion, and the heat insulating member is arranged such that the other end surface is in contact with one end surface of the molded body or the sintered body. A method for manufacturing a ceramic honeycomb filter, characterized by placing In the method for manufacturing a ceramic honeycomb filter according to any one of claims 1 to 3,
A method for manufacturing a ceramic honeycomb filter, wherein the heat insulating member has a length of 10 to 100 mm in the through-hole direction. In the method for manufacturing a ceramic honeycomb filter according to any one of claims 1 to 4,
A method for producing a ceramic honeycomb filter, wherein the sealing portion provided in the heat insulating member has a depth of 1 to 60% from the one end surface of the through hole of the heat insulating member. In the method for manufacturing a ceramic honeycomb filter according to any one of claims 1 to 5 ,
The fired body having the honeycomb structure is made of cordierite ceramic,
A method for manufacturing a ceramic honeycomb filter, wherein the plugging material slurry is a slurry containing cordierite powder or a cordierite forming raw material. In the method for manufacturing a ceramic honeycomb filter according to any one of claims 1 to 6 ,
The sintering of the plugging material slurry has a temperature rising process, a holding process at the sintering temperature, and a temperature decreasing process, and the temperature decreasing rate in the temperature decreasing process is from the sintering temperature to the sintering temperature -300°C. A method for manufacturing a ceramic honeycomb filter, characterized in that the temperature is 40 to 300°C/hr in the range of In the method for manufacturing a ceramic honeycomb filter according to any one of claims 1 to 7 ,
A method for producing a ceramic honeycomb filter, wherein the plugging material slurry is fired in a continuous furnace.

Images