JP2010083738A - Method for producing aluminum titanate-based ceramic honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an aluminum titanate-based ceramic honeycomb structure which is hardly cracked by relieving the shrinkage occurring during firing. <P>SOLUTION: The method for producing an aluminum titanate-based ceramic honeycomb structure includes mixing, forming, and drying a material including a ceramic raw material including at least a titania powder and an alumina powder and a binder to form a dried honeycomb and firing the dried honeycomb. In the firing step, the honeycomb structure is fired under the following conditions: V1<V2 and V2>V3, wherein V1 is the heating rate in the temperature range where the shrinkage is mainly caused by the titania powder and the alumina powder; V2 is the heating rate in the temperature range where the synthetic reaction of aluminum titanate mainly proceeds; and V3 is the heating rate in the temperature range where the firing reaction of aluminum titanate mainly proceeds. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an aluminum titanate ceramic honeycomb structure. In particular, the present invention relates to a method for manufacturing an aluminum titanate ceramic honeycomb structure suitable for use in a ceramic honeycomb filter used for purifying exhaust gas containing PM discharged from a diesel engine or the like.

  In order to remove the fine particles contained in the exhaust gas discharged from the diesel engine, the partition walls of the ceramic honeycomb structure are made of a porous ceramic body, and the exhaust gas is passed through the partition walls, so that the fine particles in the exhaust gas are made into the partition walls A ceramic honeycomb filter for collecting fine particles (hereinafter abbreviated as “honeycomb filter”) having a structure for collecting particles has been put into practical use. In this honeycomb filter, if the collected fine particles are accumulated, the pores of the partition walls are clogged and the pressure loss becomes high. Therefore, it is necessary to burn and remove the accumulated fine particles and regenerate the honeycomb filter. . For this reason, as a function of the honeycomb filter, it is required to endure a use environment in which the deposited fine particles are repeatedly exposed to a high temperature when burning. Therefore, the honeycomb filter needs to have high heat resistance and high thermal shock resistance, and cordierite has been mainly used as a ceramic body constituting the partition walls. However, when the fine particles burn, the temperature of the ceramic honeycomb filter may exceed the melting point of cordierite of 1450 ° C. due to the combustion heat of the fine particles, and the partition wall may be melted and the filter function may not be performed. It was. Therefore, studies have been made to use aluminum titanate having a melting point of about 1860 ° C. This aluminum titanate has the advantages of a high melting point and a low coefficient of thermal expansion, but has a large shrinkage during firing, and it is necessary to suppress cracking during firing.

Patent Document 1 discloses a structure for use in high temperature applications, comprising about 50-90 wt% iron or magnesium stabilized aluminum titanate (Al ₂ TiO ₅ ) and about 10-50 wt% strontium. feldspar comprises a porous ceramic material consisting essentially of _{(SrO · Al 2 O · 2SiO} 2), about -10 × 10 ^-7 / ℃ from + 15 × 10 ^-7 / ℃ over the temperature range up to 1000 ° C. from room temperature Ceramic honeycomb structure having a thermal expansion coefficient of about 15-50 volume percent, preferably 40-50 volume percent porosity, and a median pore size of about 5-50 micrometers, preferably 8-15 micrometers Is described. In the examples, it is disclosed that firing is performed at a rate of 20 to 40 ° C./hour at various temperature intervals up to a maximum temperature of 1485 to 1500 ° C.

Also, US Pat. No. 6,057,056 includes mullite with high permeability, high interconnected porosity and large median pore size that can be used as a filter for diesel exhaust due to low pressure drop and low back pressure on the engine. The following is described as an aluminum titanate ceramic product. That is, an iron-aluminum titanate solid solution having a stoichiometric amount of Al _{2 (1-x)} Fe _2x TiO ₅ of 60 to 90%, where x is 0 to 0.1, expressed as a percentage by weight of the total, and 10 Contains -40% mullite (3Al ₂ O ₃ .2SiO ₂ ), expressed as weight percent on an oxide basis, 3 to 15% SiO ₂ , 55 to 65% Al ₂ O ₃ , 22 to 40% Porous diesel particulate filter made of mullite / aluminum titanate composed of a porous ceramic body consisting essentially of TiO ₂ and 0 to 10% Fe ₂ O ₃ and useful for diesel exhaust filtration is described Yes. And the embodiment discloses firing at a rate of 10 to 20 ° C./hour at various temperature intervals up to a maximum temperature of 1650 to 1700 ° C.

Patent Document 3 describes the following as a ceramic product suitable for high-temperature applications such as an automobile exhaust gas control system that does not have the disadvantages of existing materials. That is, u (Al ₂ O ₃ · TiO ₂ ) + v (R) + w (3Al ₂ O ₃ · 2SiO ₂ ) + x (Al ₂ O ₃ ) + y (SiO ₂ ) + z (1.1SrO · 1.5Al ₂ O ₃ 13.6SiO ₂ · TiO ₂ ) + a (Fe ₂ O ₃ · TiO ₂ ) + b (MgO · 2TiO ₂ ), where R is SrO · Al ₂ O ₃ · 2SiO ₂ or 11. 2SrO · 10.9Al ₂ O ₃ · 24.1SiO ₂ · TiO ₂ , and u, v, w, x, y, z, a and b are u + v + w + x + y + z + a + b = 1, 0.5 <u ≦ 0.95, 0.01 <v ≦ 0.5, 0.01 <w ≦ 0.5, 0 <x ≦ 0.5, 0 <y ≦ 0.1, 0 <z ≦ 0.5, 0 <a ≦ 0. 3. An aluminum titanate-based ceramic having a composition that is a weight fraction of each component such that 3 and 0 <b ≦ 0.3. Click products have been described. And the examples include a first holding temperature of 1200 ° C. for 4 hours and a second holding temperature of 1500 ° C. for 6 hours, with 20 ° C./hour to 40 ° C./hour over various temperature intervals. It is disclosed to fire at a rate that ranges from time to time.

  Patent Document 4 describes the following as a method for firing a honeycomb formed body that suppresses the generation of cracks that cause cracks in the honeycomb fired body. That is, an aluminum titanate honeycomb molded body is filled with ceramic powder in a ceramic container placed with a porous surface facing up and down, the honeycomb molded body is embedded, and the upper end of the honeycomb molded body embedded with the ceramic powder It is described that firing is performed while replenishing the ceramic powder from the storage portion of the ceramic container so that the porous surface of the ceramic and the upper part of the ceramic powder are substantially flush with each other.

  Further, in Patent Document 5, as a method for firing a ceramic honeycomb structure in which cracks do not occur in the opening end face of the ceramic honeycomb structure, which is a contact surface between the firing table and the ceramic honeycomb structure, a green ceramic honeycomb structure is provided. A method is described in which the open end face of is placed on a heat-resistant inorganic powder and fired.

  Further, Patent Document 6 describes a method of firing using a ceramic torch made of the same material as that of the raw honeycomb structure due to problems of cracking and adhesion of the honeycomb end face resulting from uneven temperature distribution during firing. Yes.

Special Table 2005-519834 JP 2005-534474 A JP 2005-534597 A JP-A-11-147773 JP 2004-59353 A Japanese Patent Laid-Open No. 2-40019

  However, even if the aluminum titanate ceramic honeycomb structure is fired under the firing conditions described in Patent Literature 1, Patent Literature 2, and Patent Literature 3, the temperature range in which aluminum titanate thermally shrinks and the liquid phase reaction proceeds. Large shrinkage occurs in the honeycomb structure in the temperature range. For this reason, it has been difficult to avoid cracks generated in the honeycomb structure due to the stress generated by the large shrinkage.

  Further, in the firing methods described in Patent Literature 4, Patent Literature 5, and Patent Literature 6, since the shrinkage is large when firing the aluminum titanate ceramic honeycomb structure, the end face of the honeycomb structure that comes into contact with the firing table or the torch In the part, the shrinkage is hindered due to the frictional resistance with the firing table and the torch. Therefore, there has been a problem that the outer diameter of the end face part of the honeycomb structure in contact with the firing table or the torch is larger than that of the other end face part, and cracking occurs on the end face part side.

  Accordingly, an object of the present invention is to provide a method for producing an aluminum titanate ceramic honeycomb structure that relaxes shrinkage that occurs during firing and does not easily cause cracks.

  That is, the present invention relates to an aluminum titanate ceramic in which a ceramic raw material containing at least titania powder and alumina powder and a material containing a binder are mixed, formed, dried to form a honeycomb dried body, and the honeycomb dried body is fired. A method for manufacturing a honeycomb structure, wherein in the firing, the temperature rise rate V1 in the shrinkage temperature region mainly of titania powder and alumina powder of the honeycomb structure, mainly in the temperature region where the synthesis reaction of aluminum titanate proceeds. The firing is characterized in that the temperature rise rate V2, mainly the temperature rise rate V3 in the temperature range in which the firing reaction of aluminum titanate proceeds, is V1 <V2 and V2> V3.

  In the present invention, in the firing, the heating rate V1 in the shrinkage temperature region mainly of the titania powder and the alumina powder of the honeycomb structure is 1 to 50 ° C./hr, and the temperature range in which the synthesis reaction of aluminum titanate proceeds mainly. The heating rate V2 is preferably 10 to 80 ° C./hr, and the heating rate V3 is preferably 1 to 50 ° C./hr in the temperature range where the firing reaction of aluminum titanate proceeds.

  In the present invention, the ceramic raw material preferably contains at least titania powder, alumina powder, silica powder, and magnesia powder.

  In the present invention, it is preferable to perform firing by firing the honeycomb dried body on a powder obtained by mixing and sintering titania powder, alumina powder, and silica powder in firing.

  In the present invention, it is preferable to perform firing by placing a honeycomb-shaped firing table made of the same material as the honeycomb dried body and placing the honeycomb dried body on the upper surface of the honeycomb-shaped firing table.

  In the present invention, in the firing, a honeycomb-shaped firing table made of the same material as the dried honeycomb body is placed on the powder obtained by mixing and sintering titania powder, alumina powder, and silica powder, and the honeycomb. It is preferable to perform firing by placing the dried honeycomb body on the upper surface of the shape firing table.

  In the present invention, the ceramic raw material preferably contains a pore former.

  In the present invention, the pore former is preferably a foamed foamed resin.

Next, the function and effect of the present invention will be described.
In the method for manufacturing an aluminum titanate ceramic honeycomb structure according to the present invention, a material containing at least a titania powder and an alumina powder and a material containing a binder are mixed, formed, and dried to obtain a honeycomb dried body. A method of manufacturing an aluminum titanate ceramic honeycomb structure in which the body is fired, wherein the honeycomb structure has a heating rate V1 in a shrinkage temperature region mainly of titania powder and alumina powder, mainly titanium. By firing at a temperature rise rate V2 in the temperature range where the synthesis reaction of aluminum oxide proceeds, mainly at a temperature rise rate V3 in the temperature range where the firing reaction of aluminum titanate proceeds, V1 <V2 and V2> V3. Have the following effects. That is, in the shrinkage temperature range (about 900 to about 1300 ° C) mainly due to the titania powder and alumina powder of the honeycomb structure, the titania (TiO ₂ ) shrinks, and the temperature at which the firing reaction of the aluminum titanate mainly proceeds In the region (about 1400 ° C. or higher), the synthesized aluminum titanate shrinks, and in the temperature region where these shrinkage occurs, cracking tends to occur if the rate of temperature rise is too fast. Therefore, the generation of cracks can be suppressed by slowing the heating rates V1 and V3 in this temperature range. In the temperature range (about 1300 to about 1400 ° C.) where the synthesis reaction of aluminum titanate proceeds mainly, shrinkage does not occur and cracking is unlikely to occur, so the temperature increase rate V2 in this temperature range can be increased. .

Here, the heating rate V1 in the shrinkage temperature region mainly of the titania powder and the alumina powder of the honeycomb structure is 1 to 50 ° C./hr, and the heating rate V2 in the temperature region where the synthesis reaction of aluminum titanate mainly proceeds. Is preferably 10 to 80 ° C./hr, and the temperature rise rate V33 in the temperature range where the firing reaction of aluminum titanate proceeds is preferably 1 to 50 ° C./hr.
When the heating rate V1 in the shrinkage temperature range (about 900 to about 1300 ° C) mainly with titania powder and alumina powder is less than 1 ° C / hr, it is preferable because the time required for firing becomes longer and the productivity decreases. Absent. On the other hand, if it exceeds 50 ° C./hr, the rate of temperature rise becomes too fast, and cracking tends to occur, which is not preferable. Preferably, it is 5-40 degreeC / hr.
In addition, when the temperature increase rate V2 in the temperature range (about 1300 to about 1400 ° C.) where the synthesis reaction of aluminum titanate proceeds is less than 10 ° C./hr, the time required for firing becomes longer and the productivity is increased. Since it falls, it is not preferable. On the other hand, if it exceeds 80 ° C./hr, the rate of temperature rise becomes too fast, and crystallization of aluminum titanate in the liquid phase reaction becomes insufficient, which is not preferable. Preferably, it is 20-70 degreeC / hr.
In addition, when the temperature increase rate V3 in the temperature range (about 1400 ° C. or higher) where the firing reaction of aluminum titanate proceeds is less than 1 ° C./hr, the time required for firing becomes longer and the productivity is lowered. It is not preferable. On the other hand, if it exceeds 50 ° C./hr, the rate of temperature increase becomes too fast, and cracking tends to occur, which is not preferable. Preferably, it is 5-40 degreeC / hr.

  In the present invention, the ceramic raw material for constituting the aluminum titanate ceramic honeycomb structure includes at least titania powder, alumina powder, silica powder, and magnesia powder in a range having a high melting point and a low thermal expansion coefficient. be able to.

  Further, in the method for producing an aluminum titanate ceramic honeycomb structure of the present invention, in firing, titania powder, alumina powder and silica powder are mixed and sintered, and the honeycomb dried body is placed on the pulverized powder and fired. By performing the above, the following effects are obtained. That is, since the shrinkage is large during firing of the aluminum titanate ceramic honeycomb structure, the shrinkage is hindered at the end face of the honeycomb structure contacting the firing table due to frictional resistance with the firing table. The outer diameter of the end face part of the honeycomb structure in contact with the torch is larger than that of the other end face part, and cracking occurs on the end face part side. However, when the honeycomb structure shrinks by placing the sintered powder of titania powder, alumina powder, and silica powder on the firing shelf, spreading the pulverized powder, and placing the dried honeycomb body thereon, the firing shelf The powder on the top serves as a roller and has the effect of suppressing frictional resistance. Therefore, the end surface portion of the honeycomb structure easily contracts. As a result, the contraction of the upper surface and the lower surface of the dried honeycomb dried body becomes almost uniform, and cracking of the end surface portion hardly occurs. In addition, when the powder on the firing shelf is unsintered, the powder and the dried honeycomb body adhere to each other at the time of firing, and the powder does not easily serve as a roller, and the effect of suppressing the frictional resistance is reduced. Therefore, it is not preferable.

  Further, in the method for producing an aluminum titanate ceramic honeycomb structure of the present invention, in firing, a honeycomb-shaped firing table made of the same material as the honeycomb dried body is placed, and the honeycomb dried body is placed on the upper surface of the honeycomb-shaped firing table. By carrying out baking with the following effects are obtained. That is, since the shrinkage is large during firing of the aluminum titanate ceramic honeycomb structure, the shrinkage is hindered at the end face of the honeycomb structure contacting the firing table due to frictional resistance with the firing table. The outer diameter of the end face part of the honeycomb structure in contact with the torch is larger than that of the other end face part, and cracking occurs on the end face part side. However, when the honeycomb structure is contracted by placing the honeycomb-shaped firing table made of the same material as the honeycomb dried body on the firing shelf and placing the honeycomb dried body on the upper surface of the honeycomb-shaped firing table, The base and the honeycomb structure shrink together. The shrinkage is inhibited on the lower surface of the honeycomb-shaped firing table due to friction with the firing shelf, but the shrinkage is not inhibited on the upper surface of the honeycomb-shaped firing table, so the honeycomb dried body placed on the upper surface of the honeycomb-shaped firing table However, the shrinkage is not hindered, and the shrinkage of the upper surface and the lower surface of the dried honeycomb body becomes almost uniform, so that cracking hardly occurs. Since the honeycomb-shaped firing table is made of the same material as the honeycomb dried body, the honeycomb dried body and the honeycomb-shaped firing table shrink together as a result of firing. Compared to the end surface portion side, it is difficult to be large, and cracks are unlikely to occur on the end surface portion side.

  Further, in the method for manufacturing an aluminum titanate ceramic honeycomb structure of the present invention, in firing, titania powder, alumina powder, and silica powder are mixed and sintered, and the pulverized powder is made of the same material as the honeycomb dried body. By placing the honeycomb-shaped firing table and firing the honeycomb dried body on the upper surface of the honeycomb-shaped firing table, the following effects are obtained. That is, since the shrinkage is large during firing of the aluminum titanate ceramic honeycomb structure, the shrinkage is hindered at the end face of the honeycomb structure contacting the firing table due to frictional resistance with the firing table. The outer diameter of the end face part of the honeycomb structure in contact with the torch is larger than that of the other end face part, and cracking occurs on the end face part side. However, on the firing shelf, titania powder, alumina powder, and silica powder are mixed and sintered, and the pulverized powder is laid, and a honeycomb-shaped firing table made of the same material as the dried honeycomb body is placed on the firing shelf. By placing the honeycomb dried body on the upper surface of the firing table, when the honeycomb structure shrinks, the honeycomb shaped firing table and the honeycomb structure shrink as a whole, and further, the powder under the honeycomb shaped firing table, In the honeycomb-shaped firing table, the shrinkage frictional resistance becomes small, so that the shrinkage of the honeycomb-shaped firing table is difficult to be inhibited. As a result, the honeycomb dried body placed on the honeycomb-shaped firing table has shrinkage on the upper surface and the lower surface. It becomes uniform and the crack of the end face portion is less likely to occur.

  Here, titania powder, alumina powder, and silica powder are mixed and sintered, and the pulverized powder is used for the role of the roller when the honeycomb-shaped firing table placed on this powder shrinks during firing. This is because there is an effect of suppressing frictional resistance. If this powder is unsintered, this powder and the honeycomb-shaped firing table are fixed at the time of firing, so that the powder does not play a role of a roller and the effect of suppressing the frictional resistance is reduced, which is not preferable.

  In addition, since the honeycomb-shaped firing table is made of the same material as the honeycomb dried body, the honeycomb dried body and the honeycomb-shaped firing table shrink together as a result of firing. Compared to the end surface portion side, it is difficult to be large, and cracks are unlikely to occur on the end surface portion side.

  Further, in the method for manufacturing a ceramic honeycomb formed body of the present invention, the pore volume of the partition walls of the honeycomb structure is increased by including the pore former in the ceramic raw material, and the pressure loss is small when used as a honeycomb filter. This is preferable. In addition, it is preferable that the pore former is a foamed foamed resin, because when the foamed resin is burned off during firing, the dried honeycomb body does not expand, and cracking hardly occurs.

  According to the method for manufacturing an aluminum titanate ceramic honeycomb structure of the present invention, it is possible to obtain a method for manufacturing an aluminum titanate ceramic honeycomb structure in which shrinkage generated during firing is reduced and cracking is unlikely to occur.

Next, the present invention will be described based on embodiments.
Mixing, kneading, extruding, drying, titania powder, alumina powder, silica powder, magnesia powder, molding aid, and additive as ceramic raw material powder to make aluminum titanate composition, outer diameter 50mm, long A honeycomb structure 1 shown in FIG. 1 having a green body having a thickness of 90 mm, a partition wall thickness of 0.25 mm, and a partition wall pitch of 1.4 mm was obtained.
Further, as a honeycomb-shaped firing table, the honeycomb-shaped firing table 2 having a length of 30 mm was manufactured by extrusion molding with an outer diameter of 70 mm in the same manner as the above-described raw material honeycomb structure.
On the other hand, cordierite, alumina, mullite, silica, aluminum titanate synthetic powder (AT synthetic powder), and aluminum titanate raw powder (AT raw powder) were prepared as powders 3 constituting the firing table. A mixture of titania, alumina, and silica was used as a raw material for the aluminum titanate synthetic powder and the aluminum titanate raw powder. The aluminum titanate synthetic powder was obtained by forming the material of the same composition into a honeycomb shape, firing it in a batch-type firing furnace, and pulverizing it with a ball mill. Each of these powders was laid on a firing shelf, a honeycomb-shaped firing table was placed thereon, a green honeycomb dried body was placed thereon, and firing was performed in a batch-type firing furnace. The firing was performed at a temperature increase rate of 15 ° C./hr up to 900 ° C., and 900 ° C. or higher was performed at the maximum temperature of 1600 ° C. at the temperature increase rate shown in Table 1. Then, after firing, a visual inspection for cracks was performed on the opening end face of the ceramic honeycomb structure, and it was judged that the cells were continuously cut at two or more locations as cracks. , The number ratio of the fired body in which cracking occurred was less than 1% (◎), 1% or more and less than 3% (◯), 3% or more and less than 5% ( (Triangle | delta)) What was 5% or more was evaluated as (x).

As shown in Table 1, the manufacturing method of the ceramic honeycomb structure of Examples 1 to 16 can provide a manufacturing method of the ceramic honeycomb structure that hardly causes cracking. On the other hand, it can be seen that the methods for manufacturing the ceramic honeycomb structures of Comparative Examples 1 to 3 have cracks and have problems.

It is a schematic diagram showing firing of a ceramic honeycomb structure according to the present invention.

Explanation of symbols

1: Ceramic honeycomb structure 2: Honeycomb-shaped firing table 3: Powder constituting the firing table 4: Firing shelf

Claims (8)

Production of an aluminum titanate ceramic honeycomb structure in which a ceramic raw material containing at least titania powder and alumina powder and a material containing a binder are mixed, formed, dried to obtain a honeycomb dried body, and the honeycomb dried body is fired. In the firing, in the firing, a heating rate V1 in a shrinkage temperature region mainly of a titania powder and an alumina powder of the honeycomb structure, a heating rate V2 in a temperature region in which a synthesis reaction of aluminum titanate mainly proceeds, A method for producing an aluminum titanate ceramic honeycomb structure, characterized in that firing is performed such that a temperature increase rate V3 in a temperature range in which a firing reaction of aluminum titanate mainly proceeds is V1 <V2 and V2> V3. In the firing, the heating rate V1 in the shrinkage temperature region mainly of titania powder and alumina powder of the honeycomb structure is 1 to 50 ° C./hr, and the heating rate in the temperature region where the synthesis reaction of aluminum titanate mainly proceeds. 2. The aluminum titanate according to claim 1, wherein V2 is 10 to 80 ° C./hr, and a temperature rising rate V3 in a temperature range in which the firing reaction of aluminum titanate mainly proceeds is 1 to 50 ° C./hr. For producing a high-quality ceramic honeycomb structure. The method for manufacturing a ceramic honeycomb structure according to claim 1 or 2, wherein the ceramic raw material includes at least titania powder, alumina powder, silica powder, and magnesia powder. 4. The firing according to claim 1, wherein in the firing, titania powder, alumina powder, and silica powder are mixed and sintered, and the dried honeycomb body is placed on the pulverized powder and fired. 5. A method for producing a ceramic honeycomb structure according to claim 1. In the firing, the honeycomb-shaped firing table made of the same material as the honeycomb dried body is placed, and the honeycomb dried body is placed on the upper surface of the honeycomb-shaped firing table and fired. 4. A method for producing a ceramic honeycomb structure according to any one of 3 above. In the firing, titania powder, alumina powder, and silica powder are mixed and sintered, and a honeycomb-shaped firing table made of the same material as the dried honeycomb body is placed on the pulverized powder, and the upper surface of the honeycomb-shaped firing table is placed. The method for manufacturing a ceramic honeycomb structure according to any one of claims 1 to 3, wherein the dried honeycomb body is placed and fired. The method for manufacturing a ceramic honeycomb structure according to any one of claims 1 to 6, wherein the ceramic raw material includes a pore former. The method for manufacturing a ceramic honeycomb structure according to claim 7, wherein the pore former is a foamed foamed resin.

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