JP2003097262A - Sealing material for catalyst converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material excellent in characteristics as that for an exhaust emission control catalyst converter such as heat resistance and durability. SOLUTION: This sealing material for the catalyst converter is used by inserting in between a columnar catalyst holder and a cylindrical metallic shell covering the outside of the catalyst holder. A seal mat composing the sealing material is formed by covering the mat which is prepared by impregnating both edges thereof in the exhaust gas inlet and outlet sides with an inorganic binder, with an airtight composite film which has a vapor deposited film of an inorganic material comprising either one of SiO2 , Al2 O3 or Al on the inner face of a multilayered film comprising either one of polyethylene, polypropylene or polyethylene terephthalate. In this case, the mat is packed with the above composite film under reduced pressure in such a state that the inorganic binder is not dry yet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing material for an automobile exhaust gas purifying catalytic converter.

[0002]

2. Description of the Related Art Conventionally, as an exhaust gas purifying catalytic converter mainly mounted on a vehicle, as shown in FIG.
It is known that the catalyst holder 4 and the metal shell 2 that covers the outer side of the catalyst holder 4 and a sealing material using an inorganic material sheet interposed between the two are known. In such a catalytic converter, the sealing material is used to prevent the exhaust gas from leaking from between the shell 2 and the catalyst holder 4, and is generally a silica / alumina ceramic fiber or an unexpanded vermiculite. A seal mat 3 formed by molding a mixture of an inorganic binder and an organic elastic material into a sheet.
Is used.

[0003]

However, in recent years,
Due to the high performance of automobiles and various legal regulations, the temperature of exhaust gas has risen remarkably, and in the conventional catalytic converter shown in FIG. 1, the heat resistance of the above-mentioned sealing material is insufficient, and sufficient sealing performance must be secured. Has become difficult. This is because the heat of exhaust gas embrittles the silica-alumina ceramic fiber in the sealing material and deteriorates the expansion characteristics of unexpanded vermiculite, so that the pulse pressure of the exhaust gas causes the seal layer to be eroded. It is believed that this is because.

On the other hand, as a technique for improving the durability of this sealing material, Japanese Patent Laid-Open No. 8-334015 discloses a sealing material in which a portion 1 to 10 mm from the end of the exhaust gas contact surface is hardened with an inorganic binder. Proposed. According to the sealing layer according to this proposal, it is possible to suppress the wind erosion of the sealing material by certainly sintering the inorganic binder at 300 to 600 ° C to fix the intersection of the silica and alumina fibers in the sealing layer. be able to.

However, such a sheet material is in a cured state by being dried, for example, at 80 ° C. for 12 hours until it is inserted between the catalyst holder and the metal shell covering the outside thereof. For this reason, there is a problem in that it is difficult to process into a cylindrical shape because of lack of flexibility and breakage during winding.

In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a catalytic converter sealing material having excellent characteristics as a sealing material for an exhaust gas purifying catalytic converter, such as heat resistance and durability. To propose. Another object of the present invention is to provide a sealing material which can be easily wound and assembled on a catalyst holder.

[0007]

[Means for Solving the Problems] As a result of intensive studies to achieve the above-mentioned purpose, in order to maintain the durability of the sealing material, it is necessary to impregnate the end portion, where gas contact is frequent, with an inorganic binder. The inventors have found that it is effective to pack the inorganic binder in an undried state under reduced pressure to be effective and to impart flexibility, and have arrived at the present invention. That is, the present invention is a sealing material for a catalytic converter that is used by being inserted between a columnar catalyst holder and a cylindrical metal shell that covers the outside of the catalyst holder, and has both ends on the exhaust gas inlet and outlet sides. A sealing material for a catalytic converter, wherein a sealing mat impregnated with an inorganic binder is vacuum-packed with an airtight film.

In the present invention, the above seal mat
Is alumina, silica-alumina, silica, glass, etc.
It is a composite of any one or two and retains the catalyst.
Packing density of 0.15 when inserted between body and metal shell
~ 0.5g / cm³Is preferably adjusted to. Also,
In the present invention, each end of the seal mat is impregnated with
Machine binders are synthetic mica, montmorillonite, coro
Any selected from idal alumina and colloidal silica
It is preferable to use at least one kind. Also,
In the present invention, an inorganic binder for the end of the seal mat
The range of impregnation is 1 to 10 mm from both ends of the gas inlet / outlet side.
Preferably. Further, in the present invention, the above airtightness
As a film, polyethylene, polypropylene or
Multilayer film made of either polyethylene terephthalate
The inner layer is made of SiO ₂, Al₂O₃Or Al
Inorganic material vapor deposition film consisting of either one containing 1 nm to 1 μm
It is preferable to use a composite film. Furthermore, in the present invention
In addition, the sealing material is not cut into a predetermined size.
Machine fiber seal mat, polymerize the airtight film above
Adjust the vacuum to 500 to 755 mmHg when vacuum packing
It is preferable that

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As the above-mentioned catalyst holder constituting the exhaust gas purifying catalytic converter, for example, a honeycomb structure made of cordierite or alumina can be used. Further, as the metal shell, for example, a stainless steel tube having an elliptical cross section, a circular shape or the like, or a half-split stainless steel split tube can be used.

The sealing material inserted between the catalyst holder and the metal shell has a packing density of 0.15 to 0.5 g / in the state of being inserted between the catalyst holder and the metal shell. cm
^Use the one adjusted to be ³ . This is because if the packing density of the raw material is less than 0.15 g / cm ³ , a predetermined holding force cannot be obtained and the catalyst holder may be displaced. On the other hand, if the packing density is greater than 0.5 g / cm ³ , the inorganic fiber may be broken and scattered due to high compressive stress after assembly, and the catalyst holder may be crushed. The packing density of a more suitable inorganic sealing material is
It is in the range of 0.2 to 0.4 g / cm ³ .

The seal mat, which constitutes the main part of the sealing material, is based on one or more fibrous materials selected from alumina, silica-alumina, glass and silica.
It is preferable to use a composite of this with another inorganic material or organic material.

As the inorganic binder to be impregnated into both ends of the seal mat on the exhaust gas contact side, at least one selected from synthetic mica, montmorillonite, colloidal alumina and colloidal silica is used. In addition,
This inorganic binder is used as an aqueous solution,
An aqueous solution of synthetic mica is suitable in consideration of wrapping properties around the catalyst carrier.

In the treatment with the inorganic binder, the above-mentioned inorganic binder is applied and impregnated within a range of 1 to 10 mm from both ends of the seal mat. The reason why the seal mat is reinforced with an inorganic binder in a range of 1 to 10 mm is that if it is less than 1 mm, it is difficult to improve wind erosion resistance. Because it will be.

In addition, the seal mat, which has been treated with the end portion of the inorganic binder as described above, is packed with the inorganic binder in an undried state in order to improve the winding property and the assembling property. Two airtight films are used for the vacuum packing. An example of this film is a multi-layer film made of polyethylene, polypropylene or polyethylene terephthalate, with the inner layer
It is preferable that the composite film is prepared by vapor deposition of any one of SiO ₂ , Al ₂ O _{3 and} Al and the total thickness of which is adjusted to 10 to 100 μm. It should be noted that the reason for depositing SiO ₂ , Al ₂ O ₃ or Al on the inner surface of the composite film is that the presence of an evaporated film having a predetermined thickness on one surface of the film significantly improves the gas barrier performance and improves the inorganic sealing material. This is because the state immediately after the decompression pack can be maintained for a long time. The reason why the total thickness of the composite film is 10 to 100 μm is 10 μm.
If it is thinner, the gas barrier performance and pinhole resistance will be insufficient, while if it is thicker than 100 μm,
This is because the composite film itself becomes hard, and the wrapping property around the catalyst support deteriorates.

The thickness of the deposited film of SiO ₂ , Al ₂ O ₃ or Al is preferably adjusted to about 1 nm to 1 μm.
This is because if the film thickness is less than 1 nm, the thickness of the gas barrier layer becomes insufficient and it becomes difficult to maintain the state immediately after the reduced pressure pack for a long period of time. On the other hand, if the thickness exceeds 1 μm, the vapor deposition film becomes hard and it becomes difficult to wind the vapor deposition film around the catalyst holder, and the vapor deposition film is likely to be cracked or broken.

As a method for packing the seal mat under reduced pressure, it is preferable to cut the seal mat to a predetermined size, stack the composite films, heat seal the peripheral portion in a reduced pressure atmosphere, and perform vacuum packaging. In this treatment, the degree of vacuum is preferably adjusted to 500 to 755 mmHg. This is because when the pressure is less than 500 mmHg, the reduced pressure packed state is insufficient and the residual air is contained, so that the winding property and the assembling property around the catalyst holder are deteriorated. On the other hand, if it is higher than 755 mmHg, the inorganic fiber mat-like material will be densified in the reduced pressure packed state, and the flexibility of the seal mat will be impaired, so that it will be difficult to wind it around the catalyst holder.

The seal material thus packed under reduced pressure is filled with the seal material interposed between the catalyst holder and the metal shell, and the seal material is filled with the seal material interposed between the catalyst holder and the metal shell. It is packed in a density of 0.15 to 0.50 g / cm ³ , wound around a catalyst support under such conditions, and attached to a metal shell for use. The packing density of the seal layer that is sandwiched between the catalyst holder and the metal shell
The reason why it is set to 0.15 g / cm ³ or more is that if it is smaller than this, a predetermined holding force cannot be obtained in the metal shell 2 and the mounting position of the catalyst holding body may be displaced.
If it is larger than g / cm ³ , the inorganic fiber may be broken and scattered. More preferably 0.30-0.40 g / cm
^{Is 3} .

[0018]

EXAMPLE 1 Hereinafter, a sheet material of an exhaust gas purifying converter according to the present invention will be described with reference to FIG.
It will be described based on 2. As shown in the figure, the exhaust gas purifying converter 1 according to the present invention has a gap between a catalyst holder 4 made of cordierite having a honeycomb structure cross section and a metal shell 2 covering the outer peripheral surface of the catalyst holder 4, Packing density
The sealing material adjusted to 0.3 g / cm ³ is inserted. Here, the inorganic sealing material is obtained by cutting a mat-shaped material (sealing mat 3) of alumina fibers into a predetermined size, and then impregnating both ends of the exhaust gas contact with an aqueous synthetic mica solution, and then impregnating the impregnating part 3a. On the upper and lower surfaces of the seal mat having the above, a composite film having a thickness of 50 μm and having a polyethylene terephthalate as a base material and a vapor deposition layer 5 of SiO ₂ as an inner layer is laminated, and at the same time the outer peripheral portion of the seal mat 3 is heat-sealed , Vacuum packed at a vacuum degree of 500 mmHg. In this example, SiO ₂
The thickness of the vapor deposition film 5 was 100 nm.

The inorganic sealing material produced as described above is
After being left at room temperature for one month, it was attached to the exhaust gas purifying catalytic converter shown in FIG. 1, and as a result, there was no problem in winding and assembling the inorganic sealing material around the catalyst holder, and it was satisfactory. Also, the result of exposure to a high-temperature exhaust gas flow in an actual vehicle was good, with no fiber scattering.

Example 2 A seal having the same catalytic converter structure as in Example 1, except that only the composite film was made of polypropylene as a base film, and Al ₂ O ₃ was vapor-deposited to a thickness of 100 nm on the inner layer of the base film. As a result of changing the material to an attempt to manufacture, there was no particular problem. Further, as in Example 1, the inorganic sealing material was left to stand at room temperature for one month, and as a result of the production test, there was no problem in winding and assembling the inorganic sealing material around the catalyst holder, and high temperature exhaust gas was used in an actual vehicle. The results of exposure to the flow were also good, with no fiber scattering.

Comparative Example 1 With respect to the same sealing material for catalytic converters as in Example 1, there was no inorganic binder impregnation treatment portion 3a at the side end of the exhaust gas,
Moreover, as a result of trying production using a polyethylene terephthalate film having a thickness of 50 μm and having no vapor deposition layer 5 on the film, there is no particular problem if an inorganic sealing material immediately after the reduced pressure pack is used, but 1 hour after the reduced pressure pack. At this point, the inorganic sealing material had swollen, making it difficult to wind it around the catalyst holder.

Comparative Example 2 With respect to the same sealing material for catalytic converters as in Example 1, there was no impregnated portion 3a for impregnating the inorganic binder at the side end of the exhaust gas,
And having a film SiO ₂ vapor deposition layer 5 of 100 nm and a thickness of 50 μm
m of polyethylene terephthalate film was vacuum-packed and left at room temperature for 1 month, and the exhaust gas purifying catalytic converter shown in Fig. 1 was attached. As a result, in winding and assembling the inorganic sealing material around the catalyst holding body. Was good without problems. However, as a result of exposure to a high temperature exhaust gas flow in an actual vehicle, scattering of fibers was observed on the gas inlet side.

[0023]

As described above, according to the seal material of the present invention, both end portions of the seal mat in the seal layer, which serve as the exhaust gas contact surface of the seal mat, on the gas inlet and outlet sides are impregnated with the inorganic binder, and Since the seal mat uses a film containing a vapor-deposited layer such as SiO ₂ as an airtight film, exhaust gas can be sealed without damaging the catalyst support, and the heat resistance and durability of the sealing material are good. is there. Particularly, in the case of the sealing material according to the present invention, it has good flexibility and is excellent in mounting in the metal shell, that is, in winding property and assembling property.

[Brief description of drawings]

FIG. 1 is a sectional view of a catalytic converter.

FIG. 2 is a perspective view illustrating a structure of a sealing material according to the present invention.

[Explanation of symbols]

1 Converter 2 Metal Shell 3 Seal Mat 3a Inorganic Binder-Impregnated Part 4 Catalyst Support 5 SiO ₂ Deposition Film 6 Plastic Film

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keiji Yamada             3-200 Kawama-cho, Ogaki City, Gifu Prefecture IBIDEN CORPORATION             Inside the Kawama Factory (72) Inventor Keiichi Sakashita             3-200 Kawama-cho, Ogaki City, Gifu Prefecture IBIDEN CORPORATION             Inside the Kawama Factory (72) Inventor Hiroshi Tamura             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. F-term (reference) 3G091 AA02 AB01 BA07 BA10 BA39                       FB03 GB01Z GB17Z HA26                       HA27 HA29                 4D048 BB18 CC04 CC06

Claims (6)

[Claims] 1. A seal material for a catalytic converter, which is used by being inserted between a columnar catalyst holder and a cylindrical metal shell covering the outside of the catalyst holder, wherein both ends of the exhaust gas inlet and outlet sides are made of inorganic material. A sealing material for a catalytic converter, wherein a seal mat impregnated with a binder is vacuum-packed with an airtight film. 2. The seal mat is alumina,
It is a composite of one or two kinds of silica-alumina, silica, glass, etc., and the packing density in a state of being inserted between the catalyst support and the metal shell is adjusted to 0.15 to 0.5 g / cm ^3. The sealing material for a catalytic converter according to claim 1, wherein 3. The inorganic binder impregnated at each end of the seal mat is at least one selected from synthetic mica, montmorillonite, colloidal alumina and colloidal silica.
A sealing material for a catalytic converter according to item 1. 4. The catalytic converter according to claim 1, wherein the end of the seal mat is impregnated with the inorganic binder from 1 to 10 mm from both ends of the gas inlet / outlet side. Sealing material. 5. The airtight film is composed of a multilayer film made of any one of polyethylene, polypropylene and polyethylene terephthalate, and has an inner layer as an inner layer.
SiO _2, Al ₂ O ₃ or a catalytic converter for sealing material according to any one of claims 1 to 4, characterized in that a composite film comprising 1nm~1μm either become more inorganic materials deposited film of Al . 6. The vapor deposition film of the inorganic material has a thickness of 1
The sealing material for a catalytic converter according to any one of claims 1 to 5, wherein the sealing material has a thickness of nm to 1 µm.