JP3980919B2 - Holding material for catalytic converter and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a support material for a catalyst carrier used, for example, in an exhaust gas purification catalytic converter of an automobile or the like.
[0002]
[Prior art]
As is well known, vehicles such as automobiles are equipped with a catalytic converter for exhaust gas purification in order to remove harmful components such as carbon monoxide, hydrocarbons and nitrogen oxides contained in the exhaust gas of the engine. Yes. Such a catalytic converter is generally mounted in a catalyst carrier 1 formed in a cylindrical shape, a metal casing 2 containing the catalyst carrier 1, and the catalyst carrier 1, as shown in a sectional view in FIG. 3. And a holding material 3 interposed in a gap between the catalyst carrier 1 and the casing 2.
[0003]
As the catalyst carrier 1, for example, a noble metal catalyst or the like supported on a cylindrical honeycomb formed body made of, for example, cordierite is generally used. Therefore, the catalyst carrier 1 is held in the gap between the catalyst carrier 1 and the casing 2. The material 3 is not purified from the function of holding the catalyst carrier 1 safely so that the catalyst carrier 1 does not collide with the casing 2 due to vibration or the like during driving of the automobile, and the gap between the catalyst carrier 1 and the casing 2. It is necessary to have a function of sealing so that the exhaust gas does not leak. Therefore, at present, there is a wide range of so-called “mat type” holding materials in which inorganic fibers such as alumina fibers, mullite fibers, or other ceramic fibers are gathered to a predetermined thickness using a binder and have appropriate elasticity. in use.
[0004]
However, this mat type holding material is required to be wound around the catalyst carrier 1 to hold the wound state with a tape or a nonwoven fabric, and to be press-fitted into the casing 2 when the catalytic converter is manufactured. A so-called “mold-type holding material” is also used in which inorganic fibers are formed into a cylindrical shape in accordance with the shape of the outer periphery of the catalyst carrier 1 and the inner periphery of the casing 2. Since this mold-type holding material can be wound around the catalyst carrier 1 as it is and can also be attached to the casing 2 as it is, the production work of the catalytic converter can be greatly reduced.
[0005]
[Problems to be solved by the invention]
In order to produce the above mold type holding material, an aqueous slurry containing inorganic fibers and a binder is attached to the surface of the cylindrical wire mesh, sucked from the inside of the cylindrical wire mesh, dehydrated, and then dried to form the cylindrical wire mesh. In general, a method called suction dehydration molding is used to demold.
[0006]
However, since the holding material needs to have a certain thickness, if it is to be molded to the same thickness as the mat type holding material, a large molding pressure of about 4 to 5 times is required, and a large facility is required. ing. Also, drying takes a considerably long time compared to the mat-type holding material.
[0007]
Thus, although the conventional mold-type holding material has an advantage in manufacturing the catalytic converter, the manufacturing of the holding material itself has problems in terms of the size of the equipment and the manufacturing cost. Accordingly, an object of the present invention is to provide a holding material for a catalytic converter that can be manufactured even if the manufacturing conditions are relaxed while having the advantages of a mold type holding material.
[0008]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that the manufacturing conditions can be relaxed by combining the mat-type holding material and the mold-type holding material, thereby completing the present invention. did.
[0009]
That is, in order to achieve the above object, the present invention provides a cylindrical catalyst carrier, a casing for housing the catalyst carrier, a gap between the catalyst carrier and the casing wound around the catalyst carrier. A method for producing the holding material used in a catalytic converter provided with a holding material interposed between the inorganic material- containing aqueous slurry and producing a sheet-like wet molded body by sucking and dehydrating the inorganic fiber- containing aqueous slurry; After forming the mat layer by processing the molded body into a cylindrical shape, a step of forming a mold layer by adhering an inorganic fiber- containing aqueous slurry to the surface of the mat layer by suction dehydration and a step of drying the whole are provided. the first method of manufacturing a catalytic converter for holding material, characterized in Rukoto or, forming a cylindrical mold layer by sucking dehydrating the inorganic fiber-containing aqueous slurry with a cylindrical network type, A step of producing a sheet-like wet molded body by sucking and dehydrating the machine fiber-containing aqueous slurry, and forming a mat layer by wrapping the sheet-like wet molded body around the mold layer, and then forming an inorganic fiber on the surface of the mat layer. A second method for producing a holding material for a catalytic converter, comprising: a step of forming a mold layer by adhering the aqueous slurry by suction dehydration; and a step of drying the whole. The holding material used in a catalytic converter comprising a catalyst carrier, a casing that accommodates the catalyst carrier, and a holding material that is wound around the catalyst carrier and interposed in a gap between the catalyst carrier and the casing. A holding for a catalytic converter obtained by the above manufacturing method, wherein the mold layer and the mat layer are laminated so that the mold layer is an outermost layer. To provide.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the holding material according to the present invention will be described in detail.
[0011]
As shown in FIG. 1, the holding member 3 of the present invention, the inner layer and the mat layer 30, a two-layer structure in which the outer layer and the mold layer 31 or urchin by are shown in FIG. 2, the innermost layer and the mold layer 31 the mat layer 30 is provided on the outside, Ru 3-layer structure der that the outermost and mold layer 31.
[0012]
The mat layer 30 is equivalent to a conventional mat type holding material and has moderate elasticity. On the other hand, the mold layer 31 is equivalent to a conventional mold holding material.
[0013]
As the inorganic fibers forming the mat layer 30 and the mold layer 31, various inorganic fibers conventionally used for holding materials can be used. For example, alumina fibers, mullite fibers, or other ceramic fibers can be used as appropriate. More specifically, as the alumina fiber, for example, Al ₂ O ₃ is preferably 90% by weight or more (the remainder is SiO ₂ minutes) and has a low crystallinity in terms of X-ray. An average fiber diameter of 3 to 7 μm and an average fiber length of 0.05 to 5 mm are preferable. As the mullite fiber, for example, a mullite composition having an Al ₂ O ₃ minute / SiO ₂ minute weight ratio of about 72/28 to 80/20 and having a low crystallinity in terms of X-ray is preferable. The average fiber diameter is preferably 3 to 7 μm and the average fiber length is 0.05 to 5 mm. Examples of other ceramic fibers include silica-alumina fibers and silica fibers, but any of them may be those conventionally used for holding materials. Moreover, you may mix | blend glass fiber and rock wool.
[0014]
The inorganic fibers forming the mat layer 30 and the inorganic fibers forming the mold layer 31 may be the same or different. The selection of the inorganic fibers of the mud layer 30 and the mold layer 31 and the combination of both layers can be appropriately performed according to the desired holding performance and sealing performance.
[0015]
In addition, the inorganic fiber forming the mold layer 31 that is the outermost layer has an average fiber length longer than the other mold layers (in the case of three or more layers as shown in FIG. 2) and the respective inorganic fibers forming the mat layer 30. Is preferably short. When average fiber length becomes long, the surface of the obtained holding material 3, ie, the surface of the mold layer 31, will become rough, and an external appearance and handleability will worsen.
[0016]
Further, the binder for binding the inorganic fibers may be the same as the conventional one, and rubbers, water-soluble organic polymer compounds, thermoplastic resins, thermosetting resins and the like can be used. Specifically, examples of rubbers include a copolymer of n-butyl acrylate and acrylonitrile, a copolymer of ethyl acrylate and acrylonitrile, a copolymer of butadiene and acrylonitrile, and butadiene rubber. Examples of the water-soluble organic polymer compound include carboxymethyl cellulose and polyvinyl alcohol. Examples of thermoplastic resins include homopolymers and copolymers such as acrylic acid, acrylic ester, acrylamide, acrylonitrile, methacrylic acid, methacrylic ester, acrylonitrile / styrene copolymer, acrylonitrile / butadiene / styrene copolymer Etc. Examples of the thermosetting resin include a bisphenol type epoxy resin and a novolac type epoxy resin. The amount of these binders used may be the same as that of a conventional mat type holding material or mold type holding material.
[0017]
The ratio between the layer thickness of the mat layer 30 and the layer thickness of the mold layer 31 is not particularly limited, and the type and density of the inorganic fibers are taken into account so that the desired holding performance and sealing performance can be obtained. And set as appropriate. However, if the mold layer 31 becomes too thick, problems (high pressure, long-time drying, etc.) of the conventional mold-type holding material become apparent, which is not preferable. Therefore, it can be said that the thickness of the mold layer 31 is desirably 60% or less, preferably 50% or less of the total thickness of the holding material at the maximum.
[0018]
Next, a method for producing the holding material 3 of the present invention will be described.
[0019]
For example, to produce a holding material 3 having a two-layer structure shown in FIG. 1, first, pouring inorganic fiber-containing aqueous slurry is adjusted composition to form a mat layer 30 on a flat et halftone type, suction dried Thus, a sheet-like wet molded body may be obtained, and this may be wound around a cylindrical net and fixed with a tape or a nonwoven fabric. Next, an inorganic fiber-containing aqueous slurry whose composition has been adjusted to form the mold layer 31 is adhered to the surface of the cylindrical wet molded body, and suction dewatered. Then, after the whole is put in an oven and sufficiently dried, the cylindrical net is removed, whereby the holding material 3 having the inner layer as the mat layer 30 and the outer layer as the mold layer 31 is obtained.
[0020]
In order to manufacture the holding material 3 having the three-layer structure shown in FIG. 2, first, the inorganic fiber-containing aqueous slurry for the mold layer is attached to the surface of the cylindrical net-type, sucked and dehydrated, and then the same as described above. Thus, the mat layer 30 and the mold layer 31 may be formed sequentially.
[0021]
In the above manufacturing method, the pressure required for suction dehydration of the mold layer 31 depends on the layer thickness of the mold layer 31, but is one third to two minutes as compared with the case where the entire holding material is a mold. It can be reduced to about 1. Also, the drying time can be shortened from one third to about one half as compared with the case where the entire holding material is a mold.
[0022]
As shown in FIG. 3, the holding material 3 of the present invention formed as described above is wound around the catalyst carrier 1 and interposed in the gap with the casing 2 as in the prior art, but is previously formed into a cylindrical shape. Therefore, the winding work around the catalyst carrier 1 and the mounting work of the casing 2 can be easily performed.
[0023]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited at all by this.
[0024]
Example 1
A mat layer aqueous slurry containing 8 parts by weight of an organic binder (acrylic emulsion) per 100 parts by weight of alumina fibers having an average fiber diameter of 4 μm and an average fiber length of 3 mm was prepared. Further, an aqueous slurry for a mold layer containing 8 parts by weight of an organic binder (acrylic emulsion) with respect to 100 parts by weight of alumina fibers having an average fiber diameter of 4 μm and an average fiber length of 1 mm was prepared. First, an aqueous slurry for a mat layer was attached to the surface of a 200 mesh stainless steel flat mesh mold, and suction dewatered to obtain a wet molded body having a thickness of 8 mm. This wet molded body was pressurized using a 1 tank press to obtain a wet molded body having a thickness of 5 mm. Subsequently, an aqueous slurry for the mold layer was adhered to the surface of the wet molded body, and suction dehydration was performed to obtain a wet molded body having an inner layer thickness of 5 mm, an outer layer thickness of 2 mm, and a total thickness of 7 mm. Next, a cylindrical cover having an inner diameter of 114 mm is attached to the wet formed body, and the whole is heated and dried at 105 ° C. to obtain a cylindrical holding material having an inner diameter of 100 mm, a thickness of 7 mm, and a length of 100 mm. Obtained.
[0025]
(Comparative Example 1)
Using the aqueous slurry for mold layers of Example 1, adhesion to a cylindrical net, suction dehydration, and drying were performed to obtain a cylindrical holding material having the same shape.
[0026]
(Comparison of manufacturing conditions)
In Comparative Example 1, the thickness was restored after drying, and was about 10% larger than the target. Accordingly, the bulk density of the molded body is smaller than 0.16 g / cm ³ and the target of 0.175 g / cm ^3. On the other hand, in Example 1, only 2% of the thickness was restored and the bulk density was 0.173 g / cm ³ , and it was easy to mold to the target thickness and bulk density.
[0027]
(Mounting test)
The holding material obtained in Example 1 was wound around a cordierite catalyst carrier having a cylindrical honeycomb structure with an outer diameter of 100 mm and a length of 110 mm, and mounted on a stainless steel casing to produce a catalytic converter. And the produced catalytic converter was connected to the exhaust pipe of the gasoline engine, and let the exhaust gas pass. Analysis of the gas discharged from the catalytic converter during the passage of the exhaust gas revealed that no unpurified exhaust gas that would have come from the leakage of the holding material was detected and the sealing performance was good.
[0028]
【The invention's effect】
As described above, according to the present invention, the holding material for the catalytic converter having the advantages of the mold type holding material can be obtained under manufacturing conditions that are relaxed compared with the case of manufacturing the conventional mold type holding device.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a holding material of the present invention.
FIG. 2 is a perspective view showing another example of the holding material of the present invention.
FIG. 3 is a cross-sectional view schematically showing a catalytic converter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Catalyst carrier 2 Casing 3 Holding material 30 Mat layer 31 Mold layer

Claims (6)

A catalytic converter comprising a catalyst carrier formed in a cylindrical shape, a casing for housing the catalyst carrier, and a holding member wound around the catalyst carrier and interposed in a gap between the catalyst carrier and the casing A method for producing the holding material used,
A step of sucking and dehydrating the inorganic fiber- containing aqueous slurry to produce a sheet-like wet molded body;
Forming the mold layer by processing the wet molded body into a cylindrical shape to form a mat layer, and then attaching an inorganic fiber- containing aqueous slurry to the surface of the mat layer by suction dehydration;
The process of drying the whole
Method of manufacturing a catalytic converter for holding material, characterized in Rukoto equipped with. A catalytic converter comprising a catalyst carrier formed in a cylindrical shape, a casing for housing the catalyst carrier, and a holding member wound around the catalyst carrier and interposed in a gap between the catalyst carrier and the casing A method for producing the holding material used,
A step of sucking and dewatering the inorganic fiber-containing aqueous slurry using a cylindrical net to form a cylindrical mold layer;
A step of sucking and dehydrating the inorganic fiber-containing aqueous slurry to produce a sheet-like wet molded body;
Forming a matte layer by winding a sheet-like wet compact around the mold layer, and then adhering an inorganic fiber-containing aqueous slurry to the surface of the matte layer by suction dehydration; and
The process of drying the whole
Manufacturing method of that catalytic converter for holding material to said Rukoto equipped with. And inorganic fibers forming the mat layer, according to claim 1 or 2 method for producing a catalytic converter for holding material wherein Rukoto changing the inorganic fibers forming the mold layer. And inorganic fibers forming the mat layer, the manufacturing method according to claim 1 or 2 catalytic converter holding material, wherein same to Rukoto the inorganic fibers forming the mold layer. Inorganic fibers forming the mold layer comprising an outermost layer, either of the preceding claims, characterized in Rukoto with shorter average fiber length than that of the inorganic fiber forming the other mold layer and mat layer 1 The manufacturing method of the holding | maintenance material for catalytic converters as described in a term. A catalytic converter comprising a catalyst carrier formed in a cylindrical shape, a casing for housing the catalyst carrier, and a holding member wound around the catalyst carrier and interposed in a gap between the catalyst carrier and the casing The holding material used, obtained by the manufacturing method according to any one of claims 1 to 5 , wherein the mold layer and the mat layer are laminated so that the mold layer is an outermost layer. Characteristic holding material for catalytic converter.

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