JPH08215522A - Filter for exhaust gas and production thereof - Google Patents

Abstract

PURPOSE: To provide a filter for exhaust gas having high melting point, excellent heat resistance, high resistance against abnormal combustion, a small coefft. of thermal expansion, high strength against fatique due to thermal hysteresis, and excellent durability, and to provide production method thereof. CONSTITUTION: This filter for exhaust gas is equipped with a honeycomb columnar body essentially comprising aluminum titanate. The honeycomb columnar body has 29-63% porosity. The coefft. α of thermal expansion of this body in the extruding direction and in the perpendicular direction to the extrusion direction when the honeycomb body is produced satisfies |α|<=1.8×10<-6> deg.C<-1> . The pores have 8 to 42 average pore diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas filter for collecting and treating particulate matter such as soot contained in exhaust gas discharged from a combustion engine such as a diesel engine and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, as environmental problems have become more serious, attention has been paid to the treatment of particulate matter such as soot dispersed in the atmosphere together with exhaust gas exhausted from a combustion engine such as a diesel engine. These particulate matters are collected by an exhaust gas filter connected in the middle of the exhaust pipe.
When the exhaust gas filter collects particulate matter, its collection ability gradually decreases. Therefore, when a predetermined amount of collection is reached, the particulate matter must be burned to regenerate the exhaust gas filter.
An electric heater system is mainly used for regeneration of the exhaust gas filter. In the electric heater method, an electric heater is installed on the inflow side or the outflow side of the exhaust gas, and the electric heater is heated to heat the particulate matter to ignite and burn it. The combustion temperature is controlled by the amount of supplied air. Since the particulate matter does not burn as a whole at once, but gradually burns from the end, a temperature gradient occurs in the exhaust gas filter, and thermal stress or thermal shock occurs. At this time, the trapped amount of the particulate matter cannot be accurately detected, and the trapped amount fluctuates ± 40% with respect to the target trapped amount frequently, which may cause abnormal combustion. .
At this time, abnormal combustion means that if more particulate matter than the set value is collected, rapid combustion is performed during regeneration and the temperature is 1000
A phenomenon that rises above ℃. Exhaust gas filters must have heat resistance to withstand this abnormal combustion. Further, the exhaust gas filter is strongly required to have a low coefficient of thermal expansion and thermal shock resistance so that fatigue stress due to thermal stress or thermal shock caused by thermal history due to the regeneration treatment does not occur. Further, it is required that the collection efficiency of the particulate matter is high and the pressure loss is small, and the balance of these characteristics is extremely important. In order to meet these requirements, exhaust gas filters have been studied from various sides and various developments have been made.

For example, as a material used for an exhaust gas filter, a cordierite sintered body (2MgO.2Al ₂ O ₃ .5) is used.
SiO ₂ ). Cordierite crystals generally exhibit anisotropic thermal expansion and the coefficient of thermal expansion is 2.0 on the a-axis.
It differs from x10 ^-6 ° C ^-1 and -0.9x10 ^-6 ° C ^{-1 on} the c-axis. However, the plate crystals such as kaolin and talc contained in the raw material receive shearing force in the extrusion process and are dispersed in the direction parallel to the lattice. The c-axis of the crystal is slightly oriented in the extruding direction.
Therefore, the coefficient of thermal expansion in the extruding direction is 0.4 to 0.7 × in the combination of the crystallographic direction of cordierite and the plate-like crystal.
It becomes 10 ^-6 ° C ^-1 , and the coefficient of thermal expansion in the direction perpendicular to the extrusion direction is 0.9 to 1.5 x 10 ^-6 ° C ^-1 , which makes the coefficient of thermal expansion small in all directions, which is advantageous for thermal shock. Is being considered.

Further, another material for exhaust gas filters is aluminum titanate (Al ₂ O ₃ .TiO ₂ ). Aluminum titanate has a melting temperature of 1600 ° C.
As above, it is resistant to abnormal combustion that occurs when the exhaust gas filter is regenerated and has excellent heat resistance. However, the coefficient of thermal expansion of a crystal of aluminum titanate is 11.8 × 10 ⁻⁶ ° C. ^{−1 on the} a-axis and 19.4 × 10 ^{−6 on} the b-axis.
^It has an anisotropy of ⁻⁶ ° C. ⁻¹ , a c-axis of −2.6 × 10 ⁻⁶ ° C. ⁻¹ , and a crystal orientation. Also, in the case of aluminum titanate, the c-axis direction is oriented in the extrusion direction during extrusion molding, and at the same time, crystal grains grow in columnar or plate-like shapes in the extrusion direction due to grain growth during sintering. Therefore, the coefficient of thermal expansion in the extrusion direction is approximately -1.0 x 10 in the range of room temperature to 800 ° C.
^-6 ° C. ^-1, thermal expansion coefficient of the extrusion direction and the direction perpendicular tended to show a high value of about 3.0 × 10 ^-6 ℃ ^-1.

Next, a conventional method for manufacturing an exhaust gas filter will be described. First, a pore-forming agent is mixed and dispersed in ceramic powder to form a paste, which is then extruded through a honeycomb die to form a honeycomb structure. Next, the honeycomb structure is fired to burn off the pore-forming agent, and at the same time, the honeycomb structure is firmly bonded to produce an exhaust gas filter.

[0006]

However, in the above-mentioned conventional exhaust gas filter, when the exhaust gas filter reaches a high temperature around 1400 ° C. due to abnormal combustion, the cordierite is melted to cause melting loss. When melting loss occurs inside the exhaust gas filter, not only the ability to collect particulate matter due to shape change decreases but also the amount of particulate matter trapped inside the exhaust gas filter partially varies, causing new melting loss. However, there is a problem that the function of the exhaust gas filter is deteriorated, the pressure loss is large, and the diesel engine becomes abnormal. In addition, since aluminum titanate has a high melting point and thus has a high resistance to abnormal combustion and is excellent in heat resistance, it has anisotropy in the coefficient of thermal expansion depending on the crystal direction and the crystal orientation due to grain growth in the sintering step during manufacturing. The thermal expansion coefficient of the entire exhaust gas filter becomes high. Therefore, when the regeneration treatment is repeated, repeated stress of thermal expansion and thermal contraction occurs in the exhaust gas filter, thermal fatigue occurs, and finally cracks occur and the exhaust gas filter is damaged.

The present invention solves the above-mentioned conventional problems, and is an exhaust gas filter having a high melting point, excellent heat resistance, high resistance to abnormal combustion, small thermal expansion coefficient, fatigue resistance due to thermal history and excellent durability. In addition, an exhaust gas filter having excellent heat resistance and heat fatigue resistance can be manufactured with high productivity and mass productivity, and an exhaust gas filter with high manufacturing yield and a manufacturing method thereof are provided.

[0008]

In order to achieve this object, an exhaust gas filter according to claim 1 of the present invention is an exhaust gas filter provided with a honeycomb columnar body containing aluminum titanate as a main component. The columns are 29-
Porosity having a porosity of 63%, a coefficient of thermal expansion α in the extrusion direction and a direction perpendicular to the extrusion direction during manufacturing of the honeycomb columnar body is | α | ≦ 1.8 × 10 ⁻⁶ ° C. ⁻¹ . Is 8-4
It has a structure having an average pore diameter of 2 μm.

In the method for producing an exhaust gas filter according to claim 2 of the present invention, the average particle size is 20 to 61 μm with respect to 100 parts by weight of a powder containing aluminum titanate as a main component having an average particle size of 3 to 25 μm. And a mixing step of mixing 10 to 60 parts by weight of the pore-forming agent powder having an average aspect ratio of 1 to 2.0 and, if necessary, adding a binder, a plasticizer, and water to form a mixture. A molding step of extruding the mixture mixed in the step into a honeycomb columnar body shape;
And a firing step of heating the molded product extruded in the molding process to burn off the pore-forming agent powder to form pores and at the same time sinter the molded product.

The method for producing an exhaust gas filter according to a third aspect of the present invention is the method for producing an exhaust gas filter according to the second aspect, wherein the heating rate is 1 to 30 ° C./hour in the firing step.

According to a fourth aspect of the present invention, there is provided the method for producing an exhaust gas filter according to the second or third aspect, wherein the pore-forming agent powder is activated carbon, coke, synthetic resin, starch or graphite. At least one of them is included.

Here, the honeycomb structure preferably has a porosity of 29 to 63%. When the porosity is less than 29%, the pressure loss increases and the exhaust function deteriorates, which is not preferable. When the porosity exceeds 63%, the collection efficiency decreases, and the particulate matter is discharged to the outside, which is an environmental problem and is not preferable. When the honeycomb columnar body is manufactured, the thermal expansion coefficient α in the extrusion direction and the direction perpendicular to the extrusion direction is | α | ≦ 1.
It is preferably 8 × 10 ^-6 ° C ^-1 . As the thermal expansion coefficient α exceeds 1.8 × 10 ^-6 ° C ^-1 , the thermal stress generated during the regenerating treatment of the particulate matter tends to cause thermal expansion and contraction and thermal fatigue, which is not preferable. 8-42μ pores
An average pore size of m is preferred. When the average pore diameter is less than 8 μm, the pressure loss increases, exhaust gas is not sufficiently discharged, and the function of the diesel engine tends to deteriorate, which is not preferable. As the average porosity exceeds 42 μm, the particulate matter permeates the exhaust gas filter and the collection efficiency deteriorates, which is not preferable. The average particle size of the aluminum titanate powder is preferably 3 to 25 μm. When the average particle size is less than 3 μm, shrinkage during firing tends to be greatly deformed, which is not preferable. When the average particle size exceeds 25 μm, the sinterability due to the diffusion of atoms during sintering is insufficient and the strength tends to decrease, which is not preferable. The average particle diameter of the pore-forming agent particles is preferably 20 to 61 μm.
If the average particle size is less than 20 μm or more than 61 μm, the average pore size of the honeycomb structure tends to be 8 to 42 μm, which is not preferable. The average aspect ratio of the pore-forming agent particles is preferably 1 to 2.0. When the average aspect ratio is less than 1 or more than 2, the c-axis of aluminum titanate tends to be oriented during extrusion and the thermal expansion coefficient of the exhaust gas filter tends to increase, which is not preferable. The pore-forming agent powder is preferably mixed in an amount of 10 to 60 parts by weight with respect to 100 parts by weight of a powder containing aluminum titanate as a main component having a particle size of 3 to 25 μm. If the pore-forming agent is blended in an amount of less than 10 parts by weight or more than 60 parts by weight, the porosity tends to fall outside the range of 29 to 63%, which is not preferable. Temperature rising rate is 1 to 30 ° C
/ Hour is preferred. When the temperature rising rate is less than 1 ° C./hour, it takes only a short time and the productivity is poor, which is not preferable. When the temperature rising rate exceeds 30 ° C./hour, thermal stress is generated at the time of temperature rising, cracks are likely to occur and breakage is high, and the manufacturing yield tends to be low, resulting in poor mass productivity, which is not preferable.

[0013]

With this structure, the average pore diameter is 8 to 42 μm.
Since the porosity is formed to be 29 to 63%, the particulate matter trapping efficiency is high and at the same time the pressure loss is small and exhaust gas can be exhausted sufficiently. Further, the coefficient of thermal expansion is 1.8.
Since the temperature can be controlled to be not more than × 10 ^-6 ° C ^-1, the thermal stress generated by the thermal history experienced during the regenerating treatment of the particulate matter is small and the thermal fatigue resistance is excellent. Furthermore, since the material is aluminum titanate, it has a high melting point and can withstand high temperatures during abnormal combustion. Therefore, both heat resistance and heat fatigue resistance can be improved at the same time.

Further, the particle size of the powder containing aluminum titanate as a main component is 3 to 25 μm, and the particle size of the pore-forming agent powder is 20.
Since the average aspect ratio is controlled to 1 to 2.0 and the compounding ratio is controlled to 10 to 60 parts by weight, it is possible to obtain the pore diameter and the porosity excellent in the trapping efficiency of the particulate matter and the pressure loss. Further, since the pore-forming agent receives the shearing force applied at the time of extrusion, the crystal orientation of aluminum titanate is arranged in a substantially random direction, and the honeycomb structure after sintering is less likely to cause anisotropy and has a small thermal expansion coefficient as a whole. it can. Since the temperature rising rate is set to 1 to 30 ° C / hour, the pore-forming agent can be burned off smoothly and completely without impairing the productivity.
It is also possible to prevent the occurrence of cracks due to thermal stress when the temperature is raised. Since any one or more of activated carbon, coke, synthetic resin, starch, and graphite was used as a pore-forming agent, it has the strength to receive shearing force during extrusion, and it is burned off in a nearly complete state during sintering. Pores can be formed.

[0015]

【Example】

(Examples 1 to 11 and Comparative Examples 1 to 9) Hereinafter, a first example of the present invention will be described with reference to the drawings. 1 is a perspective view of an essential part of an exhaust gas filter in the first embodiment, FIG. 2 is a partially enlarged sectional view of a lattice of an exhaust gas filter in the first embodiment, and FIG. 3 is a schematic view of an exhaust gas filter in the first embodiment. It is a partial cross section side view. 1 to 3
In 1, the diameter is about 144 mm and the length is 155 m
Exhaust gas filter in the first embodiment consisting of honeycomb columnar bodies of about m, 2 is a ventilation part through which particulate matter such as exhaust gas and soot passes, and 3 is a quadrangular, hexagonal, polygonal or circular cross section. Is formed in a lattice shape, through which exhaust gas permeates and particulate matter is deposited on the side wall, and a large number of pores are formed inside the lattice portion having a thickness of about 0.4 mm, and 4 are alternately arranged at the end portions of the lattice portion 3. A buried plug having a length of about 5 to 7 mm that distinguishes an inflow path from an inflow path, 5 is a pitch having a width of about 4 mm representing the distance between the lattice portions 3, and 6 is an exhaust gas advancing direction indicating a moving direction of exhaust gas. is there.

The method of manufacturing the exhaust gas filter having the above structure will be described below. Examples 1 to 1
1, aluminum titanate powder having an average particle diameter of 10 μm and an average particle diameter of 20 to 61 μm and an average aspect ratio of 1.
The pore-forming agent powder of 2 to 2.0 was mixed with the binder methylcellulose in a ratio of 10 to 60 parts by weight with respect to 100 parts by weight of a powder containing aluminum titanate as a main component. As the pore forming agent, activated carbon, coke, polyethylene resin, polystyrene resin, polyolefin resin, wheat starch, potato starch, and graphite were used. The shape and blending ratio of each raw material are shown in (Table 1).

[0017]

[Table 1]

Mixing was performed by dry mixing using a mixer.
Next, 3 to 6 parts by weight of plasticizer glycerin and 31 to 3 parts of water are added.
After adding 8 parts by weight and mixing with a kneader, the mixture was further uniformly dispersed and mixed with three rollers. The mixed sample was put into a vacuum extrusion molding apparatus, extruded into the shape of the honeycomb columnar body 1, and then dried. Next, the honeycomb columnar molded article was placed in a firing furnace to form pores and simultaneously fired to manufacture an exhaust gas filter. The heating rate at this time is 10 ° C /
Firing was performed by heating to 1500 ° C. for 4 hours and holding for 4 hours.

Next, a method for measuring the shape and structure of the raw material and the exhaust gas filter will be described. The average particle diameter of each raw material was measured using a laser type particle size distribution measuring device. The average particle size of the powder containing aluminum titanate as the main component of this example was 10 μm, and the median value was 8 to 9 μm, and the distribution was such that the median value was slightly smaller than the average particle size.

The aspect ratio is the ratio of the major axis to the minor axis and is an index showing the degree of deformation. The average aspect ratio was obtained by enlarging the pore-forming agent sample with a scanning electron microscope, measuring each side, and averaging 10 samples.

The average pore diameter and porosity of the exhaust gas filter were measured using a mercury porosimeter. Regarding the orientation of the crystal grains, 20 crystal grains were microscopically observed.

The coefficient of thermal expansion was measured by a thermal analysis (TMA) measuring device. The above measurement results are shown in (Table 1).

Next, the performance test of the exhaust gas filter will be described. In order to examine the heat resistance of each example, the sample was held in an electric furnace at a temperature of 1550 ° C. for 10 hours, then taken out of the electric furnace and the appearance was observed.

The pressure loss value and the collection efficiency were measured using a collection regeneration test device. The collection and regeneration test apparatus was equipped with a hot air generator and an acetylene carbon sprayer on the collection inlet side, and an electric heater and an air supply unit for burning acetylene carbon on the collection outlet side. A temperature measuring unit for charging a thermocouple to the side wall of the lattice unit 4 to measure the temperature and a pressure measuring unit for measuring the pressure difference between the collection inlet side and the collection outlet side were provided. The pressure loss value was obtained as follows. The electric heater was heated to control the amount of air supplied from the air supply to stabilize the exhaust gas filter at a temperature of 300 ° C. Acetylene carbon was introduced into the exhaust gas filter from the acetylene carbon spraying section, and the acetylene carbon was collected for 30 minutes. The pressure loss value was obtained by measuring the pressure difference between the collection inlet side and the collection outlet side immediately before the completion of the collection with a pressure measuring unit. The collection efficiency was obtained from the ratio of the amount of acetylene carbon used and the amount of acetylene carbon collected in the exhaust gas filter.

The thermal shock resistance was evaluated as follows. After measuring the collected weight of acetylene carbon of the above-mentioned collection and regeneration test device, the acetylene carbon collected by the electric heater is burned to be regenerated, and the cycle of the collection and combustion is set as one cycle. By repeating the above, the number of times when the collection efficiency was extremely lowered was taken as the number of times of regeneration and used as the evaluation value of the thermal shock resistance.

The results of the above evaluations are shown in (Table 1).
As is clear from (Table 1), in the exhaust gas filters of Examples 1 to 11, the coefficient of thermal expansion was 0.
7-0.8x10 ^-6 ° C ^-1 , vertical direction 1.5-1.8x
It was found to be extremely small in both directions at 10 ^-6 ° C ^-1 .
It was found that the orientation of crystal grains was almost random and did not have anisotropy. The average pore diameter is 8 to 42.
The value was μm, and the porosity was 29 to 63%.
As a result of the heat resistance test, it was proved that the material had excellent heat resistance without causing melting loss and the like even with slight shrinkage in Examples 1 to 11. It was found that the pressure loss was between about 700 and about 2000 mmaq and the collection efficiency was in the range of 71 to 84%, and the exhaust gas permeation capacity and the particulate matter collection capacity were appropriately harmonized and compatible with each other. . It was found that the impact resistance is extremely high, without deterioration even after 100 times of reproduction.

Next, as Comparative Examples 1 to 9, exhaust gas filters were manufactured by using raw materials partially outside the scope of the present invention. The manufacturing method was the same as in Examples 1 to 11, and the structures and evaluation tests of the obtained Comparative Examples 1 to 9 were also performed in the same manner. The results are shown in (Table 2).

[0028]

[Table 2]

As is clear from (Table 2), in Comparative Example 1 in which the pore-forming agent was not used, the pressure loss and the collection efficiency could not be measured, and it was found that the exhaust gas filter did not function at all. In Comparative Example 2 in which the proportion of the pore-forming agent was increased, it was found that the collection efficiency was as low as 68% and the thermal shock resistance was inferior. The deterioration of the thermal shock resistance is because the strength was lowered and it was not possible to withstand the stress due to the thermal history. In Comparative Example 3 in which the average particle diameter of the pore-forming agent was small, it was found that the pressure loss was as large as 3220 mmaq. In Comparative Example 4 in which the average particle size of the pore-forming agent was large, it was found that the collection efficiency was as low as 49%. It was found that Comparative Examples 5 and 6 having a large particle size of aluminum titanate showed a low thermal shock resistance of 21 or 29 times of regeneration. It was found that Comparative Examples 7 to 9 having a large average aspect ratio of the pore-forming agent also had an extremely low number of reproductions of 15 or less.
The thermal expansion coefficients of Comparative Example 1 and Comparative Examples 5 to 9 are as large as 2.2 to 2.9 × 10 ⁻⁶ ° C. ^{−1 in the} vertical direction. This is because in Comparative Example 1, the aluminum titanate powder was subjected to shearing force during extrusion and the c-axis was oriented because there was no pore-forming agent. In Comparative Examples 5 and 6, the particle size is large, and in Comparative Examples 7 to 9, the average aspect ratio of the pore-forming agent is large, so that the c-axis of the aluminum titanate powder is oriented without disturbing the stress field of shearing force during extrusion. Because it is done.

Next, the influence of the temperature rising rate in the firing process of this embodiment will be described. The heating rate in the firing step is 1 ° C./hour, 10 ° C./hour, 30 ° C./hour, 50 ° C. /
An exhaust gas filter was manufactured in the same manner as in Example 3 except that the time was set to four stages. When the heating rate was 1 to 30 ° C./hour, the structure of the exhaust gas filter and the result of the evaluation test were good. When the temperature rising rate was 50 ° C./hour, cracks occurred and were damaged during the firing process. This is because the pore-forming agent causes a rapid combustion reaction due to a rapid temperature rise, and a partial temperature difference occurs. When this temperature difference becomes extremely large, thermal stress causes cracks.

As described above, according to this embodiment, the average pore diameter, the porosity, and the coefficient of thermal expansion are made of aluminum titanate and are optimally controlled, so that they have heat resistance capable of withstanding abnormal combustion and also have a coefficient of thermal expansion. Is small and has high resistance to thermal shock resistance. In addition, the exhaust gas characteristics are well balanced with high pressure collection efficiency with low pressure loss. Also,
Activated carbon, coke, polyethylene resin, polystyrene resin, polyolefin resin, wheat starch, potato starch, and graphite are used as the pore-forming agent, so it can be surely burned out in the firing process and pores can be reliably formed, resulting in excellent workability and productivity. Rich in mass productivity.

[0032]

As described above, the present invention is an exhaust gas filter including a honeycomb columnar body containing aluminum titanate as a main component, the honeycomb columnar body having a porosity of 29 to 63%, and When the honeycomb columnar body is manufactured, the thermal expansion coefficient α in the extrusion direction and the direction perpendicular to the extrusion direction is
Since α | ≦ 1.8 × 10 ⁻⁶ ° C. ⁻¹ and the pores have an average pore diameter of 8 to 42 μm, the trapping efficiency for trapping particulate matter is high and the pressure loss during permeation of exhaust gas is small. Both can be balanced and excellent collection efficiency can be obtained. In addition, since it has a high melting point, does not melt even at high temperatures during abnormal combustion, retains its shape, has excellent heat resistance, and has a small coefficient of thermal expansion, the amount of deformation of expansion and contraction is small even in the thermal history that occurs during the regeneration treatment of particulate matter and fatigue. It is possible to realize an exhaust gas filter that does not easily break and has excellent thermal shock resistance.

In the present invention, the average particle size is 3 to 25 μm.
10 to 60 parts by weight of a pore-forming agent powder having an average particle diameter of 20 to 61 μm and an average aspect ratio of 1 to 2 with respect to 100 parts by weight of a powder containing aluminum titanate as a main component of Since a mixing step of adding a binder, a plasticizer, and water to form a mixture is provided, the optimum average particle diameter and porosity can be stably produced with good productivity and mass productivity. In addition, since a pore-forming agent with an appropriate shape is used, the pore-forming agent receives the shearing force during extrusion and can prevent the orientation of the c-axis of aluminum titanate, reducing the overall coefficient of thermal expansion and reducing thermal fatigue and thermal shock resistance. It is possible to realize an improved exhaust gas filter manufacturing method.

Further, according to the present invention, since the heating rate is 1 to 30 ° C./hour in the firing step, the burning of the pore-forming agent proceeds reliably and smoothly, and the pores are stably formed without partial abnormal heating. It is possible to realize a method of manufacturing an exhaust gas filter that is formed and is excellent in productivity and mass productivity.

In the present invention, the pore-forming agent powder is at least one of activated carbon, coke, synthetic resin, starch and graphite.
As described above, it is possible to realize a method for manufacturing an exhaust gas filter which is surely burned during heating, has stable pores, has a high manufacturing yield, and is excellent in productivity and mass productivity.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of an exhaust gas filter according to a first embodiment.

FIG. 2 is a partially enlarged sectional view of a lattice of an exhaust gas filter in the first embodiment.

FIG. 3 is a side sectional view of an essential part of the exhaust gas filter in the first embodiment.

[Explanation of symbols]

 1 Exhaust gas filter in 1st Example 2 Ventilation part 3 Lattice part 4 Plugging 5 Pitch 6 Exhaust gas advancing direction

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukinori Ikeda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Makoto Ogawa, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. ( 72) Inventor Koichi Watanabe 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. An exhaust gas filter comprising a honeycomb columnar body containing aluminum titanate as a main component, wherein the honeycomb columnar body has a porosity of 29 to 63%, and at the time of manufacturing the honeycomb columnar body. Coefficient of thermal expansion α in the direction of extrusion and in the direction perpendicular to the direction of extrusion is | α | ≦ 1.8 × 1
An exhaust gas filter having a mean pore diameter of 0 to 42 µm at 0 ^-6 ° C ^-1 . 2. 100 parts by weight of a powder containing aluminum titanate as a main component having an average particle diameter of 3 to 25 μm has an average particle diameter of 20 to 61 μm and an average aspect ratio of 1.
Mixing 10 to 60 parts by weight of the pore-forming agent powder of ~ 2.0,
If necessary, a binder, a plasticizer, and a mixing step of adding water to form a mixture, a molding step of extruding the mixture mixed in the mixing step into a honeycomb columnar shape, and an extrusion step of the molding step. And a baking step of heating the molded product to burn off the pore-forming agent powder to form pores and at the same time sinter the molded product. 3. The temperature rising rate is 1 to 3 in the firing step.
The exhaust gas filter manufacturing method according to claim 2, wherein the temperature is 0 ° C./hour. 4. The exhaust gas according to claim 2, wherein the pore-forming agent powder comprises at least one of activated carbon, coke, synthetic resin, starch, and graphite. Filter manufacturing method.