JP3359855B2 - Exhaust gas purification converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter for purifying exhaust gas, and more particularly to a converter for purifying exhaust gas of automobiles and the like.

[0002]

2. Description of the Related Art Conventionally, an exhaust gas purifying converter mainly mounted on a vehicle comprises a catalyst holder, a metal shell covering the outside of the catalyst holder, and an inorganic fiber mat disposed therebetween. . A catalyst such as platinum is supported on the catalyst holder. As the catalyst holder, for example, a cordierite carrier whose cross section is formed into a honeycomb shape is used.

[0003] Next, the inorganic fiber mat is mainly a mixture of vermiculite and ceramic fibers.
A fiber made of only inorganic fibers is also used. The inorganic fibers prevent the catalyst holder from being damaged when the catalyst holder comes into contact with the outer metal shell during driving of an automobile or the like, and also prevent exhaust gas from leaking from between the metal shell and the catalyst holder. Used for

As the inorganic fibers, those using a crystalline alumina fiber mat are used. However, since the crystalline alumina fiber mat is extremely bulky in an initial state, it is difficult to assemble a converter for purifying exhaust gas. Japanese Patent Application Laid-Open No. 8-174 discloses a method in which the initial thickness is reduced by vacuum packing with a resin film, or a method in which the mat is impregnated with a resin to reduce the thickness to improve the assemblability to the catalyst holder.
687 etc.

[0005]

When assembling an exhaust gas purifying converter by arranging the inorganic fibers composed of only the inorganic fibers between the catalyst holder and the metal shell, the inorganic fibers are sealed in advance with a plastic film, A method has been adopted in which the inside of the film is depressurized to a vacuum and the thickness of the inorganic fibers consisting of only the inorganic fibers is reduced, but after assembling the exhaust gas purification converter, the plastic film remains inside the exhaust pipe. Therefore, when the exhaust gas flows inside the exhaust gas purification converter, the heat of the exhaust gas causes the plastic film to vaporize and not only generate an unpleasant odor, but also adsorb to the catalyst, etc., and the exhaust gas purification system operates normally. There is a problem not to do.

On the other hand, there is a method of reducing the thickness by impregnating the mat with a resin, and a method of reducing the amount of resin impregnation in advance. However, when the amount of the resin is small, the mat has a small restoring force in the thickness direction. Is extremely large, it is difficult to reduce the initial thickness of the mat, and when assembling a converter for purifying exhaust gas, it is difficult to set the mat between the metal shell and the catalyst holder.

[0007]

According to the present invention, the packing density at the time of assembling between a catalyst support and a metal shell that covers the outside of the catalyst support is 0.2 g / cm ^{3 to} 0. 6g
/ Cm ³ , 5 to 30 wt% in the surface layer which is 0.1 to 15% in the thickness direction of the mat, and 9 to 9% in the thickness direction of the mat.
The inner layer of 9.9 to 85% contains an organic binder of 0.5 to 5% by weight, and the total content of the organic binder is not more than 10% by weight of the mat. In the exhaust gas purifying converter thus constituted, the organic binder uses a mixture of a non-electrolyte water-soluble polymer and an emulsion latex, and has a solid content mixing ratio of 1:10 to 10: 1. It is in the converter for purification.

First, for example, a honeycomb-shaped catalyst holder is used. Further, the catalyst holding body includes
For example, it is made of cordierite, alumina or the like. Next, the metal shell is, for example, a pipe having an elliptical or circular cross section, or a case divided into two in a shell shape.
Next, the mat is a crystalline alumina fiber.

Generally, crystalline alumina fibers are bulky,
It is necessary to reduce the initial thickness. In order to arrange a packing density of 0.2 g / cm ³ or more between the catalyst support and the metal shell, the bulk density of the crystalline alumina fiber mat before assembly must be at least 0.1 g / cm ^3. . The packing density of 0.2 g / cm ³ or more is for securing a necessary surface pressure for preventing the catalyst holder from shifting due to vibration or the like.
This is because if it is more than cm ³ , the restoring force of the mat will cause the catalyst holder to be crushed or the crystalline alumina fiber itself will be broken.

Since the crystalline alumina fibers are bulky, a resin impregnation treatment is performed to reduce the initial thickness. However, for the above-mentioned reason, the resin impregnation amount needs to be as small as possible. However, when the resin impregnation amount is reduced, the mat surface is rubbed with the shell when the mat is wound around the catalyst holder and then set on a metal shell, and the mat is peeled or torn. Therefore, at least the surface layer of the mat, that is, up to 0.1 to 15% in the thickness direction, needs to contain 5 to 30% by weight of the resin. Preferably, 0.5% of mat thickness
Contains 15% by weight of a resin.

Next, in order to reduce the initial thickness of the mat, a resin must be contained in the inner layer of the mat.
The remaining part of the surface layer, that is, 99.9 to 85 in the thickness direction.
% Of the resin. For the reasons described above, around 3 wt% is preferred.

Next, a method of incorporating the resin into the mat is generally performed by spraying the resin using an aqueous solvent or impregnating the mat, followed by drying. However,
There is no problem when a high-concentration resin is contained, but when a low-concentration resin is contained as in the present invention, the resin concentration in the solvent is reduced and then added to the mat and dried. Due to the effect, the impregnated resin concentrates on the surface of the mat, and almost no resin remains inside the mat. Therefore, there is a problem that the initial thickness of the mat cannot be reduced.

For this reason, a method of preventing migration using a surfactant has been adopted. However, if migration does not occur at all, as in the present invention, the entire resin content is reduced and the mat surface layer is reduced. It is difficult to control the resin content of the inner layer.

In the present invention, a mixture of a non-electrolyte water-soluble polymer and an emulsion latex is used as the organic binder. This is because the non-electrolyte water-soluble polymer having a high molecular weight functions to stop the emulsion latex moving to the surface layer due to migration during drying.

It is possible to prepare a mat using only the non-electrolyte water-soluble polymer, but since the non-electrolyte water-soluble polymer has a high strength after drying, the mat after drying becomes too hard and the exhaust gas is exhausted. When assembling the gas purification converter, it becomes difficult to wind the converter around the catalyst holder. For this reason, the solid content mixing ratio of the non-electrolyte water-soluble polymer and the emulsion latex needs to be 1:10 to 10: 1. Preferably, 1: 1 is good.

[0016]

EXAMPLES Example 1 Cordierite monolith outer shape 130 as catalyst support
mm, length 100 mm, inner diameter 138 as a metal shell
mm, thickness 2.5mm, SUS304, length 300m
m, which is divided into two parts and a flange with a width of 15 mm is attached to the divided surface. A crystalline alumina fiber mat having a thickness of 25 mm and a bulk density of 0.06 g / cm ³ as an inorganic fiber sheet, polyacrylamide (Polyaclon V-05 manufactured by Misawa Ceramic Chemicals) as a non-electrolyte water-soluble polymer, and an emulsion latex (Nipole Latex LX-
874 Nippon Zeon Co., Ltd.).

First, polyacrylamide and emulsion latex were adjusted to a solid content weight ratio of 1: 1 and then diluted with water to a mixed solution concentration of 0.9%. Next, the crystalline alumina fiber mat was impregnated with the mixed solution, sandwiched between porous plates, and dried at 80 ° C. under pressure. The mat obtained after drying had a thickness of 5 mm and a bulk density of 0.3 g / cm ³ . Further, the organic content of the mat is 5.8%, and the content of the surface layer is 1%.
The organic content in mm was 10% and the other part was 3%.

When the mat is wound around the catalyst holder, the mating portion is temporarily fixed with an adhesive tape, and compressed with a metal shell from above and below to assemble the converter for purifying exhaust gas. No. The converter for exhaust gas purification was easily assembled without damaging the mat. When the converter for exhaust gas purification was actually mounted on an automobile and the engine was turned on, no odor or the like was felt.

[0019]

According to the present invention, the packing density at the time of assembly disposed between the catalyst holder and the metal shell covering the outside of the catalyst holder is 0.2 g / cm ^{3 to} 0.6 g / 0.6 g / cm ³ . a cm ^3, 5-30 wt% in the surface layer is 0.1 to 15% of the thickness direction of the mat, the thickness direction of the mat 99.9 to 85
% Of the mat contains 10 to 5 wt% of the organic binder, and the total content of the organic binder is 10 watts of the mat.
In a converter for purifying exhaust gas constituted by a holding sealing material comprising a crystalline alumina fiber mat of not more than t%, the organic binder uses a mixture of a non-electrolyte water-soluble polymer and an emulsion latex, and has a solid content mixing ratio. By setting the ratio to 1:10 to 10: 1, not only can the converter for exhaust gas purification be easily manufactured, but also the content of organic components inside the converter for exhaust gas purification can be reduced, and the unpleasant odor during use is reduced. And the exhaust gas purification system does not malfunction.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-9-201514 (JP, A) JP-A-6-305847 (JP, A) JP-A-1-204715 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) F01N 3/28 B01D 53/00

Claims (3)

(57) [Claims] 1. An exhaust gas purification converter comprising a holding sealing material made of a crystalline alumina fiber mat disposed between a catalyst holding body and a metal shell covering the outside of the catalyst holding body. The mat has a surface layer of 5 to 30 when the converter for purifying exhaust gas is assembled.
The organic layer contains 0.5 to 5% by weight of an organic binder, and the total content of the organic binder is 10 watts of the mat.
A converter for purifying exhaust gas, which is not more than t%. 2. The packing density of the holding sealing material at the time of assembling the converter for purifying exhaust gas is 0.2 g / cm ^{3 to} 0.6 g / cm ³ .
The exhaust gas according to claim 1, wherein the exhaust gas is cm ^3.
Converter for gas purification . 3. The mat according to claim 1, wherein the surface layer of the mat has a thickness of 0.1 to 15% in the thickness direction of the mat, and the inner layer of the mat has a thickness of 99.9 to 85% in the thickness direction of the mat.
The exhaust gas purifying converter according to claim 1.