JP2002349255A - Sealing material for holding catalyst converter, its manufacturing method and catalyst converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material for holding a catalyst converter in which initial bearing pressure is high, aged deterioration of bearing pressure hardly occurs and sealing performance is excellent. SOLUTION: This sealing material 4 for holding has an alumna-silica fiber gathering in a mat state as its component and is arranged at a gap between a catalyst supporting body 2 and a metal shell 3. The crystallization rate gets larger from a first face S2 to a second face S2 in the sealing material 4 for holding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holding material for a catalytic converter, a method for manufacturing the same, and a catalytic converter.

[0002]

2. Description of the Related Art Conventionally, an internal combustion engine using gasoline or light oil as fuel has been used as a power source for vehicles, particularly automobiles, for more than 100 years. However, it is becoming increasingly problematic that exhaust gases harm health and the environment. Therefore, recently, C contained in exhaust gas
Various exhaust gas purifying catalytic converters for removing O, NOx, HC and the like, and various types of DPFs for removing PM and the like have been proposed. A typical catalytic converter for exhaust gas purification is
The fuel cell system includes a catalyst carrier, a metal shell that covers the outer periphery of the catalyst carrier, and a holding sealing material disposed in a gap between the two. As the catalyst carrier, a cordierite carrier formed in a honeycomb shape is used, on which a catalyst such as platinum is supported.

In recent years, research on the next clean power source not using oil as a power source has been advanced, and among them, a fuel cell, for example, is particularly promising. A fuel cell uses electricity obtained when water reacts with hydrogen to produce water as a power source. Oxygen is directly extracted from the air, while hydrogen is obtained by reforming methanol, gasoline, and the like. In this case, the reforming of methanol or the like is performed by a catalytic reaction. And
Such a fuel cell also uses a fuel cell catalytic converter including a catalyst carrier, a metal shell that covers the outer periphery of the catalyst carrier, and a holding sealing material disposed in a gap between the two. A cordierite carrier formed in a honeycomb shape is used as the catalyst carrier, and a copper-based catalyst is supported on the cordierite carrier.

[0004] A method of manufacturing the above catalytic converter will now be briefly described. First, a starting material containing an alumina source and a silica source is heated and melted at about 2000 ° C., and then spun and quenched to obtain ceramic fibers having the same alumina content and silica content. Thereafter, a material is prepared by gathering the ceramic fibers in a mat shape. A band-shaped holding sealing material is produced by punching out this material with a mold. Next, this holding sealing material is wound around the outer peripheral surface of the catalyst carrier, and in this state, the catalyst carrier is accommodated in a metal shell. As a result, the catalytic converter is completed.

[0005]

By the way, the holding sealing material of this type of catalytic converter is required to have a performance of reliably holding the catalyst carrier for a long period of time.

However, the conventional ceramic fibers produced by the above-mentioned melting method have an extremely low crystallization ratio (mullite ratio) of less than 1% by weight in addition to a large amount of non-crystalline components. For this reason, when the fiber is exposed to a high temperature for a long period of time, heat shrinkage occurs due to progress of crystallization, and the fiber becomes brittle and easily broken. Therefore, in the case of the holding sealing material produced using the same fiber, not only a sufficiently high initial surface pressure could not be expected, but also the degree of deterioration of the surface pressure with time was large.

Therefore, the crystallization rate of the ceramic fiber is set to 10
Countermeasures such as increasing to about% by weight can be considered. However, in this case, the elasticity and elasticity of the holding sealing material are impaired due to the hardening of the fibers, and the sealing property is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object the purpose of holding a catalytic converter having a high initial surface pressure, preventing the surface pressure from deteriorating with time, and having excellent sealing properties. It is to provide a sealing material and a catalytic converter.

Another object of the present invention is to provide a manufacturing method suitable for obtaining the above-mentioned holding sealing material.

[0010]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, a fiber aggregate of alumina-silica fibers aggregated in a mat shape is used as a constituent element,
A holding sealing material disposed in a gap between the catalyst carrier and a metal shell covering the outer periphery of the catalyst carrier,
The gist of the present invention is a holding seal material for a catalytic converter, characterized in that the crystallization ratio of the surface side portion and the crystallization ratio of the second surface side portion are different.

According to the second aspect of the present invention, a fiber aggregate of alumina-silica fibers aggregated in a mat shape is used as a constituent element, and a gap between a catalyst carrier and a metal shell covering the outer periphery of the catalyst carrier is formed. The gist of the present invention is a holding sealing material for a catalytic converter, wherein the holding sealing material is arranged such that the crystallization ratio increases from the first surface side to the second surface side.

According to the third aspect of the present invention, in the second aspect, the fiber assembly comprises one fiber assembly, and the crystallization ratio increases from the first surface side to the second surface side of the fiber assembly. I said

The invention described in claim 4 is the first to third aspects of the present invention.
In any one of the above items, the difference between the crystallization ratio of the first surface side portion and the crystallization ratio of the second surface side portion is 3% by weight or more. According to a fifth aspect of the present invention, in any one of the first to third aspects, the crystallization ratio of the first surface side portion is 0% by weight or less.
1% by weight, and the crystallization ratio of the second surface side portion was 1% by weight to 10% by weight.

According to the present invention, the alumina-silica-based fibers assembled in a mat form are used as constituent elements, and the holding member is arranged in a gap between the catalyst carrier and a metal shell covering the outer periphery of the catalyst carrier. The gist of the present invention is a sealing material for a catalytic converter, which is a sealing material, wherein a crystallization ratio varies depending on a portion.

According to a seventh aspect of the present invention, there is provided the method for producing a holding sealing material according to any one of the first to fifth aspects, wherein a spinning step of obtaining a precursor fiber from a ceramic fiber spinning solution is used. A laminating step of laminating the precursor fibers to form a mat-like fiber aggregate, and providing a difference between a firing temperature on the first surface side and a firing temperature on the second surface side to form the fiber aggregate. A method for manufacturing a holding sealing material for a catalytic converter, comprising a sintering step of sintering.

According to an eighth aspect of the present invention, in the seventh aspect, the difference between the firing temperatures is set to 100 ° C. or more. According to a ninth aspect of the present invention, the sintering temperature of the first surface is set to 800 ° C. to 1100 ° C., and the sintering temperature of the second surface is set to 1100 ° C. to 1400 ° C. .

In the tenth aspect of the present invention, a catalyst carrier, a cylindrical metal shell for covering the outer periphery of the catalyst carrier, and an alumina-silica-based In a catalytic converter comprising a holding sealing material having fibers as a constituent element, the holding sealing material contacts a first surface side having a relatively small crystallization rate with the metal shell, and has a relatively low crystallization rate. Second big
The gist of the present invention is a catalytic converter characterized in that the catalytic converter is arranged between the gaps with its surface side in contact with the catalyst carrier.

Hereinafter, the "action" of the present invention will be described. According to the first aspect of the present invention, the crystallization ratio of the first surface side portion is different from the crystallization ratio of the second surface side portion. For this reason, the surface side having a relatively large crystallization rate and excellent in heat resistance is arranged on the high temperature side, and the surface side having a relatively small crystallization rate and excellent in elasticity and elasticity is located on the low temperature side. Can be arranged. Therefore, on the high temperature side, the fibers are not easily weakened, while on the low temperature side, a gap is hardly generated between the fibers and other members. Therefore, it is possible to realize a catalytic converter holding sealing material that has a high initial surface pressure and is unlikely to cause deterioration with time of the surface pressure, and also has excellent sealing properties.

According to the second aspect of the present invention, since the crystallization ratio increases from the first surface to the second surface, the second surface having excellent heat resistance is arranged on the high temperature side. At the same time, the first surface having excellent elasticity and elasticity can be arranged on the low temperature side. Therefore, on the high temperature side, the fibers are not easily weakened, while on the low temperature side, a gap is hardly generated between the fibers and other members. Therefore, it is possible to realize a catalytic converter holding sealing material that has a high initial surface pressure and is unlikely to cause deterioration with time of the surface pressure, and also has excellent sealing properties.

According to the third aspect of the present invention, unlike the case where a plurality of fiber aggregates having different crystallization ratios are formed, for example, an operation of stacking and bonding the fiber aggregates together becomes unnecessary. In addition, the number of man-hours during manufacturing is reduced. In addition, since the thickness can be reduced as compared with the multi-layer structure, it can be relatively easily arranged in a narrow gap. Further, in the case of a multi-layered structure, there is a possibility that the fluid may pass through the interface between the fiber aggregates, whereas in the case of the single-layer structure as in the present invention, since there is no interface in the first place, there is concern about the passage of the fluid. You don't have to. Therefore, the sealing performance is excellent.

According to the fifth aspect of the present invention, the crystallization ratio of the first surface side portion and the crystallization ratio of the second surface side portion are respectively set within the above-mentioned preferred ranges, so that the surface pressure characteristics and the sealing properties are improved. Can be reliably improved. When the crystallization ratio of the first surface side portion exceeds 1% by weight or when the crystallization ratio of the second surface side portion becomes less than 1% by weight, the difference in crystallization ratio between the two decreases. Too long, and the desired properties cannot be obtained. The crystallization ratio of the second surface side portion is 10% by weight.
If the ratio exceeds the range, the heat resistance of the site may be reduced.

According to the sixth aspect of the invention, the crystallization ratio is not uniform but varies depending on the portion. Therefore, a portion having a relatively large crystallization rate and excellent in heat resistance is arranged on the high temperature side, and a portion having a relatively small crystallization rate and excellent in elasticity and elasticity is arranged on the low temperature side. be able to. Therefore, on the high temperature side, the fibers are not easily weakened, while on the low temperature side, a gap is hardly generated between the fibers and other members. Therefore, it is possible to realize a catalytic converter holding sealing material that has a high initial surface pressure and is unlikely to cause deterioration with time of the surface pressure, and also has excellent sealing properties.

According to the seventh aspect of the present invention, the mat-like fiber aggregate is sintered by providing a difference between the firing temperature on the first side and the firing temperature on the second side.
A holding sealing material having a different crystallization ratio on both surfaces can be relatively easily and reliably manufactured. Further, such a manufacturing method is also suitable for manufacturing a holding sealing material in which the crystallization rate increases from the first surface side to the second surface side in one fiber aggregate. Moreover, according to this manufacturing method, it is possible to divert an existing firing apparatus without using a special firing apparatus. Therefore, an increase in equipment cost can be avoided.

According to the eighth aspect of the present invention, by setting the difference in sintering temperature to 100 ° C. or more, the sintering easiness can be made different between the first surface side and the second surface side. It is possible to make the ratio different. Therefore, it is possible to more reliably manufacture holding sealing materials having different crystallization rates on both surfaces.

According to the ninth aspect of the invention, the firing temperature on the first surface is set lower than the firing temperature on the second surface. It is possible to obtain a holding sealing material in which the crystallization rate increases toward the surface side.

If the sintering temperature on the first surface side is lower than 800 ° C., the sintering reaction does not proceed sufficiently in the first place, and the required mechanical strength cannot be obtained. The firing temperature on the first side exceeds 1100 ° C., or the firing temperature on the second side is 11
If the temperature is lower than 00 ° C., the difference in crystallization ratio between the two is too small, and the desired properties cannot be obtained. If the sintering temperature on the second side exceeds 1400 ° C., crystallization may proceed too much, leading to a decrease in mechanical strength and heat resistance.

The operation of the invention described in claim 10 is as follows. Normally, when a catalytic converter is used, the temperature of the catalyst carrier directly exposed to the high-temperature fluid is higher, while the temperature of the metal shell is not as high as that of the catalyst carrier.
Therefore, high-temperature durability is particularly required on the surface side in contact with the catalyst carrier. In the present invention, in view of this fact, the second surface having a relatively large crystallization ratio, that is, the surface having excellent heat resistance, is brought into contact with the catalyst carrier. On the other hand, the first surface side having a relatively small crystallization ratio, that is, the surface side which is inferior in heat resistance but excellent in elasticity and elasticity, is brought into contact with the metal shell. Therefore, the fibers in the portion in contact with the catalyst carrier are less likely to be weakened, and as a result, the holding seal material has a high initial surface pressure and is unlikely to cause deterioration with time of the surface pressure. In addition, since elastic force acts on the part in contact with the metal shell,
A gap is less likely to be formed between the shell and the metal shell, and as a result, a holding sealing material having excellent sealing properties is obtained.

As described above, it is possible to realize a catalytic converter which is excellent in retention of the catalyst carrier, hardly leaks fluid, and has high processing efficiency.

[0029]

FIG. 1 shows a catalytic converter for an automobile exhaust gas purifying apparatus according to an embodiment of the present invention.
This will be described in detail with reference to FIG.

The catalytic converter 1 according to the present embodiment shown in FIG. 3 is provided in the body of an automobile in the middle of an exhaust pipe of an engine. Since the distance from the engine to the catalytic converter 1 is relatively short, about 700
Exhaust gas at a high temperature of from 900C to 900C is supplied. When the engine is a lean burn engine, the catalytic converter 1 is supplied with a still higher exhaust gas of about 900 ° C. to 1000 ° C.

As shown in FIG. 3, the catalytic converter 1 of the present embodiment basically includes a catalyst carrier 2, a metal shell 3 covering the outer periphery of the catalyst carrier 2, and a metal shell 3 between the two. And a holding sealing material 4 arranged in the gap.

The catalyst carrier 2 is made of a ceramic material typified by cordierite or the like. The catalyst carrier 2 is a columnar member having a circular cross section. Further, the catalyst carrier 2 is preferably a honeycomb structure having a large number of cells 5 extending along the axial direction. A noble metal catalyst such as platinum or rhodium that can purify exhaust gas components is supported on the cell walls. In addition, as the catalyst carrier 2, besides the above cordierite carrier, for example, a honeycomb porous sintered body of silicon carbide, silicon nitride or the like may be used.

As the metal shell 3, for example, when a press-fitting method is employed for assembling, a metal cylindrical member having an O-shaped cross section is used. In addition, as a metal material for forming the cylindrical member, a metal having excellent heat resistance and impact resistance (for example, a steel material such as stainless steel) is preferably selected. When a so-called canning method is adopted instead of the press-fitting method, a metal cylindrical member having an O-shaped cross section divided into a plurality of pieces along the axial direction (ie, a clam shell) is used.

In addition, in the case of employing a winding method for assembling, for example, a metal cylindrical member having a C-shaped or U-shaped cross section, in other words, a slit (opening) extending along the axial direction is provided at one place. Only a metal cylindrical member having only one is used. In this case, at the time of assembling the catalyst carrier 2, the one in which the holding sealing material 4 is fixed to the catalyst carrier 2 is housed in the metal shell 3, the metal shell 3 is wound up in that state, and the open end is joined ( Welding, bonding, bolting, etc.). Joining operations such as welding, bonding, and bolting are performed similarly when the canning method is adopted.

As shown in FIG. 1, the holding sealing material 4 is a long mat-like material, and has a concave mating portion 11 at one end and a convex mating portion 12 at the other end. Is provided. As shown in FIG. 2, at the time of winding around the catalyst carrier 2, the convex fitting portion 12 is
1 just engages.

The holding sealing material 4 of the present embodiment is composed mainly of ceramic fibers (that is, fiber aggregate M1) assembled in a mat shape. In the present embodiment, the alumina-silica fiber 6 is used as the ceramic fiber.
Is used.

In the holding sealing material 4 of the present embodiment, the mullite crystallization rate is not uniform but differs depending on the portion. That is, the crystallization rate of the first surface side S1 portion and the crystallization ratio of the second surface side S2 portion in one fiber assembly M1 are different, and specifically, from the first surface side S1 to the second surface side S2. The crystallization ratio increases as going to.

The first side S of the holding sealing material 4
Reference numeral 1 denotes a surface which is fired at a relatively low temperature, and is arranged so as to come into contact with the metal shell 3 which does not require much heat resistance. Therefore, the first surface side S1
Can be regarded as a low-temperature sintering surface or a shell-side contact surface. On the other hand, the second surface side S2 is a surface side fired at a relatively high temperature and is arranged so as to be in contact with the catalyst carrier 2 side where heat resistance is required. Therefore, the second surface S2 can also be grasped as a high-temperature firing surface or a carrier-side contact surface.

Here, the difference between the crystallization ratio of the surface layer portion on the first surface side S1 and the crystallization ratio of the surface layer portion on the second surface side S2 is 3
It is preferred that the content be not less than% by weight. More specifically, the crystallization ratio of the surface layer portion on the first surface side S1 is 0% by weight to 1% by weight, and the crystallization ratio of the surface layer portion on the second surface side S2 is 1% by weight to 1% by weight.
It is preferably 0% by weight.

When the crystallization ratio of the surface portion on the first surface side S1 exceeds 1% by weight, or when the crystallization ratio of the surface portion on the second surface side S2 becomes less than 1% by weight, both of them are used. The crystallization rate difference between them becomes too small, and the desired properties cannot be obtained. If the crystallization ratio of the surface layer portion on the second surface side S2 exceeds 10% by weight, the heat resistance of the portion may be rather reduced. In addition, it is desirable that the crystallization ratio of the surface layer portion on the first surface side S1 is 0% by weight, in other words, that the portion is made of amorphous.

The amount of alumina in the alumina-silica fiber 6 is preferably 40 to 100% by weight, and the amount of silica is preferably 0 to 60% by weight. The average fiber diameter of the alumina-silica fiber 6 is 3 μm.
About 25 μm, more preferably about 5 μm to 1 μm.
More preferably, it is about 5 μm. If the average fiber diameter is too small, there is a disadvantage that the fiber is easily sucked into the respiratory system. The average fiber length of the alumina-silica fiber 6 is preferably about 0.1 mm to 100 mm, and more preferably about 2 mm to 50 mm.

Alumina-silica existing on the second surface side S2
As for the system fiber 6, the fiber tensile strength is 1.0 GPa or less.
Above, the fiber bending strength is 0.8 GPa or more, and the elastic modulus is 9.5.
× 10 ^TenN / m^TwoIt is better to be above. First surface side S1
About the alumina-silica fiber 6 existing in
Tensile strength of 2.0 GPa or more, fiber bending strength of 1.5 G
Pa or more, elastic modulus is 11.0 × 10^TenN / m^TwoIs over
Is better. The reason is that fiber tensile strength and fiber bending strength
When the degree is large, it is extremely resistant to tension and bending.
This is because the alumina-silica fiber 6 is obtained.

The cross-sectional shape of the alumina-silica fiber 6 may be a perfect circular shape or an irregular cross-sectional shape (for example, an elliptical shape, an oval shape, a substantially triangular shape, etc.). Before the assembly, the thickness of the holding sealing material 4 is 1.1 times or more the gap formed between the catalyst carrier 2 and the metal shell 3.
It is desirably about 4.0 times, and more preferably about 1.5 times to 3.0 times. If the thickness is less than 1.1 times, high support holding property cannot be obtained, and the catalyst support 2 may be displaced or rattled with respect to the metal shell 3. Of course, in this case, a high sealing property cannot be obtained, so that the leakage of the exhaust gas from the gap portion is likely to occur, and a high low pollution property cannot be realized. On the other hand, if the thickness exceeds 4.0 times, it is difficult to dispose the catalyst carrier 2 on the metal shell 3 especially when the press-fitting method is adopted. Therefore, there is a possibility that improvement in assemblability cannot be achieved.

Further, the holding sealing material 4 after the assembling is performed.
Has a GBD (bulk density) of 0.10 g / cm ^{3 to} 0.30.
g / cm ³ , and further 0.10 g / cm ^{3 to} 0.25 g /
It is preferably set to be cm ³ . GBD
Is extremely small, it may be difficult to realize a sufficiently high initial surface pressure. On the other hand, if the GBD is too large, the alumina-silica fiber 6
And the cost is likely to increase.

The initial surface pressure of the holding sealing material 4 in the assembled state is preferably 50 kPa or more, more preferably 70 kPa or more. This is because if the value of the initial surface pressure is high, even if the surface pressure deteriorates with time, a suitable holding property of the catalyst carrier 2 can be maintained.

The holding sealing material 4 may be subjected to a needle punching treatment, a resin impregnation treatment, or the like, if necessary. This is because by performing these processes, the holding sealing material 4 can be compressed in the thickness direction to be reduced in thickness.

Next, a procedure for manufacturing the catalytic converter 1 will be described. First, an aluminum salt aqueous solution, a silica sol, and an organic polymer are mixed to prepare a spinning solution. In other words, a spinning stock solution is prepared by the inorganic salt method. The aqueous solution of an aluminum salt as an alumina source is also a component for imparting viscosity to the spinning dope. It is preferable to select an aqueous solution of a basic aluminum salt as such an aqueous solution. Silica sol, which is a silica source, is also a component for imparting high strength to fibers. The organic polymer is a component that plays a role as a spinnability imparting agent in the spinning solution, and in the present embodiment, for example, PVA (polyvinyl alcohol)
Etc. are used.

Next, the obtained spinning dope is concentrated under reduced pressure to obtain a spinning dope adjusted to a concentration, temperature, viscosity and the like suitable for spinning. Here, the spinning stock solution, which was about 20% by weight, is preferably concentrated to about 30% to 40% by weight. Further, the viscosity is preferably set to 10 poise to 2000 poise.

Further, when the prepared spinning dope is discharged from the nozzle of the spinning device into the air, precursor fibers having a cross-sectional shape similar to the opening shape of the nozzle are continuously obtained. The precursor fibers spun in this manner are sequentially wound while being drawn. In this case, for example, a dry pressure spinning method is preferably employed.

Subsequently, the long fibers of the precursor fibers are chopped to a predetermined length to shorten the fibers to some extent. Thereafter, by collecting, defibrating and laminating the staple fibers, or by pouring a fiber dispersion obtained by dispersing the staple fibers in water into a molding die and pressing and drying, a mat-like shape is obtained. Fiber assembly M
Get 1.

Subsequent to the laminating step, a firing step of the fiber assembly M1 is performed, and the precursor fiber is sintered to be ceramicized (crystallized). Thereby, the precursor fiber is cured to obtain the alumina-silica fiber 6. FIG. 4 illustrates an electric furnace 21 as a firing device used in the present embodiment.

The electric furnace 21 is an apparatus for continuously heating and firing the object to be fired while transporting the object in the horizontal direction. In a main body 22 constituting the electric furnace 21, a net conveyor 23 as a conveying means is accommodated. On the net conveyor 23, the mat-like fiber aggregate M1 which is an object to be fired is placed. Above the net conveyor 23, an upper electric heater 24 as a first heating means is spaced apart, and below the net conveyor 23, a lower electric heater 25 as a second heating means is spaced apart. These electric heaters 24 and 25 are connected to a power supply via temperature control means (not shown). In this device, the temperature control of the two types of electric heaters 24 and 25 can be individually performed.

In the firing step, after the fiber assembly M1 is preheated (pre-treated) in the electric furnace 21 maintained at atmospheric pressure and normal pressure, the electric furnace 21 is also maintained at atmospheric pressure and normal pressure. The main heating (firing) is performed in 21.

At this time, the temperature settings of the two types of electric heaters 24 and 25 are changed to give a certain temperature difference. That is, a difference is provided between the firing temperature of the first surface side S1 and the firing temperature of the second surface side S2 so that the fiber assembly M1 is provided.
To be sintered. In the present embodiment, the set temperature of the upper electric heater 24 is set higher than the set temperature of the lower electric heater 25.

In this case, the difference in temperature set during firing is 1
The temperature is preferably set to 00 ° C. or higher, and more preferably to 200 ° C. or higher. If the temperature difference is less than 100 ° C., it is not possible to provide a sufficient difference in sintering easiness between the first surface side S1 and the second surface side S2, and it is possible to provide a difference in crystallization ratio. Because it becomes difficult.

Further, the sintering temperature of the first surface S1 is 800 ° C.
１1100 ° C., and the firing temperature of the second surface side S2 is 11
It is preferable that the temperature is set to 00 ° C to 1400 ° C. 1st surface side S
If the sintering temperature is less than 800 ° C., the sintering reaction does not proceed sufficiently in the first place, and the required mechanical strength cannot be obtained. The firing temperature of the first surface S1 is 1100 ° C.
Or when the firing temperature of the second surface S2 is lower than 1100 ° C., the difference in crystallization ratio between the two becomes too small, and the desired properties cannot be obtained. If the sintering temperature of the second surface S2 exceeds 1400 ° C., crystallization may proceed too much, leading to a reduction in mechanical strength and heat resistance.

Further, the firing time (specifically, the time for holding at the maximum heating temperature) is preferably set to 10 minutes to 60 minutes. If the firing time is too short, the sintering reaction may not proceed sufficiently even if a sufficiently high temperature is set. Therefore, the required mechanical strength cannot be obtained. If the firing time is too long, not only does the production efficiency decrease, but crystallization may proceed too much, leading to a reduction in mechanical strength and heat resistance.

In the subsequent punching step, the mat-like fiber aggregate M1 that has undergone the firing step is punched into a predetermined shape to form the holding sealing material 4. After that, if necessary, the holding sealing material 4 may be impregnated with the organic binder, and then the holding sealing material 4 may be compression-molded in the thickness direction. In this case, examples of the organic binder include latex such as acrylic rubber and nitrile rubber, as well as polyvinyl alcohol and acrylic resin.

Then, the holding sealing material 4 is wound around the outer peripheral surface of the catalyst carrier 2, and the organic tape 13 is fixed. Thereafter, if press-fitting, canning or winding is performed, a desired catalytic converter 1 is completed.

Hereinafter, examples and comparative examples of the above embodiment will be described.

[0061]

Examples and Comparative Examples (Examples) In the examples, first, a basic aluminum chloride aqueous solution (23.5% by weight), silica sol (20% by weight, silica particle size of 15 nm) and polyvinyl as a spinnability imparting agent were used. An alcohol (10% by weight) was mixed to prepare a spinning dope. Subsequently, the obtained spinning stock solution was concentrated under reduced pressure at 50 ° C. using an evaporator to obtain a concentration of 38%.
It was prepared as a spinning solution having a weight percentage of 1500 poise and a viscosity of 1500 poise.

The prepared spinning dope was continuously jetted into the air from a nozzle (circular cross section) of a spinning device, and the formed precursor fiber was wound up while being stretched. Subsequently, the long fiber of the precursor fiber was chopped to a length of 5 mm to be shortened. Thereafter, the short fibers were dispersed in water, and the obtained fiber dispersion was poured into a molding die, followed by pressing and drying to obtain a mat-like fiber aggregate M1.

In the firing step following the above-mentioned laminating step, the fiber assembly M is placed in an electric furnace 21 maintained at atmospheric pressure and normal pressure.
After heating (pretreatment) at 250 ° C. for 30 minutes for 1 in advance, it was fired in an electric furnace 21 also maintained at atmospheric pressure and normal pressure.

In this embodiment, the first surface S
The temperature of the upper electric heater 24 was set higher so that the surface temperature of No. 1 became 1250 ° C., and the temperature of the lower electric heater 25 was set lower so that the surface temperature of the second surface S2 became 1000 ° C. . That is, a firing temperature difference of 250 ° C. was provided. The firing time was 30 minutes.

The alumina-silica-based fibers 6 in the surface layer portion on the first surface side S1 and the surface layer portion on the second surface side S2 of the fiber assembly M1 thus obtained were respectively collected and investigated for several items. Was done. Table 1 shows the results.

Regarding the crystallization ratio of the alumina-silica fiber 6, the surface layer on the first side S1 is closer to the second side S2.
It was clearly smaller than the surface layer of vice versa,
Regarding the fiber tensile strength, fiber bending strength, elastic modulus, and elongation of the alumina-silica fiber 6, the surface portion on the first surface side S1 was larger than the surface portion on the second surface side S2.

The weight ratio of alumina / silica was 72:
28, the average fiber diameter was 10.5 μm, and the cross-sectional shape of the fiber was a perfect circle. The above-mentioned mat-like fiber assembly M1 is 25 mm
Punched into a corner to obtain a surface pressure measurement sample, which was clamped by a special jig, and had a bulk density (GBD) of 0.3 g / cm ^3.
It was made to become. One sample for surface pressure measurement in this state
Held at atmospheric pressure of 000 ° C., after 1 hour and 10 hours,
The surface pressure after 100 hours was measured. In addition, the surface pressure after 1 hour was positioned as "initial surface pressure", and the surface pressure after 100 hours was positioned as "after-durability surface pressure". Further, (surface pressure after endurance / initial surface pressure) × 100 (%) was calculated and defined as the surface pressure aging deterioration rate. The results are shown in the graph of FIG.

According to this, in the sample of the example, both the initial surface pressure and the surface pressure after endurance exceeded 100 kPa, and the rate of deterioration with time of the surface pressure was relatively small. Further, after the mat-like fiber assembly M1 was punched into a predetermined shape to actually produce the holding sealing material 4, this was wound around the catalyst carrier 2 and pressed into the metal shell 3. As the catalyst carrier 2, a cordierite monolith having an outer diameter of 130 mmφ and a length of 100 mm was used. 1.5m thick metal shell 3
SUS3 having a diameter of 140 mm and an O-shaped cross section
A cylindrical member made of 04 was used. A test was conducted in which the catalytic converter 1 thus assembled was actually mounted on a 3-liter gasoline engine and operated continuously. As a result, no abnormal noise was generated during running and no looseness of the catalyst carrier 2 was recognized, and it was proved that the improvement of the initial surface pressure and the prevention of the deterioration with time of the surface pressure were surely achieved. In addition, no leakage of exhaust gas was observed and the sealing performance was excellent, and the wind erosion performance was also favorable. (Comparative Example) In the comparative example, firing was performed at 1250 ° C for 30 minutes without any difference in firing temperature. The other conditions were basically set to the same conditions as in the example, to produce a fiber assembly M1.

In the comparative example, the physical properties (crystallization rate, fiber tensile strength, fiber bending strength, elastic modulus and elongation) of the alumina-silica fiber 6 exist in the surface layer portion on the second surface side S2 of the embodiment. The physical properties of the alumina-silica fiber 6 were almost the same. That is, there was no particular difference in the degree of crystallization between the sites.

After a sample for measuring surface pressure was prepared according to the examples, the initial surface pressure, the surface pressure after endurance, and the deterioration rate with time of surface pressure were measured. As a result, as shown in the graph of FIG. 5, the sample of the comparative example was clearly inferior to the example.

[0071]

[Table 1] Therefore, according to the present embodiment, the following effects can be obtained.

(1) Normally, when the catalytic converter 1 is used, the temperature of the catalyst carrier 2 directly exposed to the high-temperature exhaust gas is higher, while the temperature of the metal shell 3 is not as high as that of the catalyst carrier 2. Therefore, high-temperature durability is particularly required on the surface in contact with the catalyst carrier 2. In the present embodiment, in view of this fact, the second surface side S2 having a relatively large crystallization rate, that is, the surface side having excellent heat resistance is brought into contact with the catalyst carrier 2. On the other hand, the first surface side S where the crystallization ratio is relatively small
1, that is, the surface side which is inferior in heat resistance but excellent in elasticity and elasticity is brought into contact with the metal shell 3. Therefore, the fibers at the portion in contact with the catalyst carrier 2 are less likely to be weakened,
As a result, the holding sealing material 4 having a high initial surface pressure and hardly causing deterioration with time of the surface pressure is obtained. Further, since an elastic force acts on a portion in contact with the metal shell 3, a gap is hardly generated between the shell 3 and the metal shell 3, and as a result, the holding sealing material 4 having excellent sealing properties is obtained.

As described above, it is possible to realize the catalytic converter 1 which is excellent in the holding performance of the catalyst carrier 2 and hardly leaks the exhaust gas and has high processing efficiency. (2) The holding sealing material 4 of the present embodiment is composed of one fiber assembly M1, and the crystallization rate gradually increases from the first surface side S1 to the second surface side S2 of the fiber assembly M1. Has become. Therefore, unlike the one constituted by a plurality of fiber aggregates M1 having different crystallization rates, there is no need to perform an operation such as overlapping and bonding the fiber aggregates M1.
Man-hours during manufacturing are reduced. Therefore, the holding sealing material 4 that can be easily manufactured can be obtained.

Further, the thickness can be made thinner than that of the multi-layer structure, so that it can be relatively easily arranged in a narrow gap. Therefore, at the time of canning, not only tightening but also press-fitting can be easily performed.

Further, in the case of a multi-layer structure, the exhaust gas may pass through the interface between the fiber aggregates M1. On the other hand, in the case of a one-piece structure such as the holding sealing material 4, since there is no interface in the first place, there is no need to worry about the passage of the exhaust gas. Therefore, the sealing performance is excellent.

(3) In the holding sealing material 4, the crystallization ratio of the first surface side S1 site and the crystallization ratio of the second surface side S2 site are set within the above preferred ranges. Therefore, the surface pressure characteristics and the sealing properties can be reliably improved, and a high-performance catalytic converter 1 can be realized.

(4) In the manufacturing method of the present embodiment, the firing is performed so as to provide a difference between the firing temperature of the first surface S1 and the firing temperature of the second surface S2 of the mat-like fiber assembly M1. It is carried out. For this reason, the holding sealing materials 4 having different crystallization ratios on the front and back sides can be relatively easily and reliably manufactured. In addition, such a manufacturing method is extremely suitable for manufacturing the holding sealing material 4 in which the crystallization rate increases from the first surface side S1 to the second surface side S2 in one fiber aggregate M1. . Moreover, according to this manufacturing method, it is possible to divert an existing firing apparatus without using a special firing apparatus. Therefore, an increase in equipment cost can be avoided.

(5) In the present embodiment, the sintering is performed while the sintering temperature of the first surface S1 and the second surface S2 is set within the above preferable range. Therefore, it is possible to reliably manufacture the holding sealing material 4 of the present embodiment in which the crystallization rate gradually increases from the first surface side S1 to the second surface side S2.

Note that the embodiment of the present invention may be modified as follows. -Like another example of the catalytic converter 1 shown in FIG.
A plurality of holding sealing materials 4 having different crystallization rates (here, 2
), And these fiber assemblies M1 may be overlapped and bonded. In this case, it is necessary to bring the fiber aggregate M1 having a low crystallization rate into contact with the metal shell 3 and bring the fiber aggregate M1 having a high crystallization rate into contact with the catalyst carrier 2.

The firing step may be performed using a firing apparatus other than the electric furnace 21 exemplified in the embodiment. The holding sealing material 4 exemplified in the embodiment has a different crystallization ratio along the thickness direction, so to speak. On the other hand, a holding sealing material having a different crystallization ratio along the length direction or a holding sealing material having a different crystallization ratio along the width direction may be used. For example, when the latter holding sealing material is wound around the catalyst carrier 2, the crystallization ratio is different between one end and the other end of the catalyst carrier 2. In other words, one end has excellent heat resistance, and the other end has excellent elasticity and elasticity. Therefore, by arranging the end having a high crystallization ratio and excellent heat resistance toward the exhaust gas inflow side, it is possible to realize the catalytic converter 1 having excellent durability and wind erosion.

The shape of the holding sealing material 4 can be arbitrarily changed. For example, the uneven positioning unit 1
A simpler shape may be omitted by omitting 1 and 12. The sectional shape of the catalyst carrier 2 is not limited to a perfect circle, but may be, for example, an ellipse or an ellipse.
In this case, the cross-sectional shape of the metal shell 3 may be changed to an elliptical shape or an elliptical shape according to the shape.

As the catalyst carrier 2, a cordierite carrier formed into a honeycomb shape as in the embodiment is used, or a honeycomb porous sintered body such as silicon carbide or silicon nitride may be used. .

In the embodiment, an example is shown in which the holding sealing material 4 of the present invention is used for the catalytic converter 1 for an exhaust gas purification device. Of course, the holding sealing material 4 of the present invention is also allowed to be used for a material other than the catalytic converter 1 for an exhaust gas purifying device, for example, a diesel particulate filter (DPF), a catalytic converter for a fuel cell reformer, and the like.

Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the above-described embodiments are listed below together with their effects. (1) A holding seal material comprising alumina-silica fibers aggregated in a mat shape as a constituent element and disposed in a gap between a catalyst carrier and a metal shell covering an outer periphery of the catalyst carrier. A holding sealing material for a catalytic converter, wherein the side portion is amorphous and the second surface side portion is crystalline. Therefore, according to the invention described in the technical idea 1, it is possible to provide a holding seal material for a catalytic converter that has a high initial surface pressure, hardly causes deterioration of the surface pressure with time, and also has excellent sealing properties.

[0085]

As described above in detail, according to the first to sixth aspects of the present invention, the catalyst which has a high initial surface pressure, hardly causes deterioration with time of the surface pressure, and has excellent sealing properties. A holding sealing material for a converter can be provided.

According to the inventions described in claims 7 to 9, it is possible to provide a manufacturing method suitable for obtaining the above-mentioned holding sealing material. According to the tenth aspect of the present invention, it is possible to provide a catalytic converter that has a high initial surface pressure, is unlikely to cause deterioration with time of the surface pressure, and has excellent sealing properties.

[Brief description of the drawings]

FIG. 1 is a perspective view of a catalytic converter holding sealing material according to an embodiment of the present invention.

FIG. 2 is a perspective view for explaining a manufacturing process of the catalytic converter of the embodiment.

FIG. 3 is a sectional view of the catalytic converter of the embodiment.

FIG. 4 is a schematic view for explaining a firing step of a mat-like fiber assembly in the embodiment.

FIG. 5 is a graph showing time-dependent deterioration of surface pressure in Examples and Comparative Examples.

FIG. 6 is a cross-sectional view of another example of a catalytic converter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Catalytic converter, 2 ... Catalyst support, 3 ... Metal shell, 4 ... Catalytic converter holding sealing material, 6 ... Alumina-silica fiber, M1 ... Fiber assembly, S1: 1st surface side,
S2: Second surface side.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 35/06 D04H 1/42 D C04B 35/80 B01D 53/36 C D04H 1/42 C04B 35/80 K F term (reference) 3G091 AA12 AB01 GA06 GB06W GB10Z GB15X GB17X HA27 HA29 4D048 BA03X BA06X BA42X BB08 BB18 4G069 AA01 AA08 BA03A BA03B CA03 DA06 EA19 EC22X EC26 EC28 ED03 FB33 4L047 AA04 AB

Claims (10)

[Claims] 1. A holding sealing material which is composed of a fiber aggregate of alumina-silica fibers gathered in a mat shape and is disposed in a gap between a catalyst carrier and a metal shell covering the outer periphery of the catalyst carrier. A crystallization ratio of the first surface side portion and a crystallization ratio of the second surface side portion are different from each other. 2. A holding sealing material disposed in a gap between a catalyst carrier and a metal shell that covers an outer periphery of the catalyst carrier, wherein a fiber aggregate of alumina-silica fibers aggregated in a mat shape is a constituent element. A holding sealing material for a catalytic converter, wherein the crystallization ratio increases from the first surface side to the second surface side. 3. The fiber assembly according to claim 2, wherein the fiber assembly comprises a single fiber assembly, and the crystallization rate increases from the first surface side to the second surface side of the fiber assembly. Holding seal material for catalytic converter. 4. The method according to claim 1, wherein a difference between a crystallization ratio of the first surface side portion and a crystallization ratio of the second surface side portion is 3% by weight or more. The holding sealing material for a catalytic converter according to the above. 5. The crystallization ratio of the first side portion is 0% to 1% by weight, and the crystallization ratio of the second side portion is 1% to 10% by weight.
The holding sealing material for a catalytic converter according to any one of claims 1 to 3, wherein: 6. A holding sealing material comprising alumina-silica fibers aggregated in a mat shape as a constituent element and disposed in a gap between a catalyst carrier and a metal shell covering the outer periphery of the catalyst carrier, wherein A holding sealing material for a catalytic converter, characterized in that the conversion ratio varies depending on the part. 7. The method for producing a holding sealing material according to claim 1, wherein a spinning step of obtaining a precursor fiber using a stock solution for spinning a ceramic fiber as a material, and laminating the precursor fiber. And a sintering step of sintering the fiber assembly by providing a difference between the sintering temperature on the first side and the sintering temperature on the second side. A method for producing a holding sealing material for a catalytic converter, comprising: 8. The method according to claim 7, wherein the difference between the firing temperatures is set to 100 ° C. or higher. 9. The sintering temperature of the first surface is set at 800 ° C. to 1100 ° C.
° C and the firing temperature on the second surface side is 1100 ° C to 140 ° C.
The method according to claim 7, wherein the temperature is set to 0 ° C. 10. A catalyst carrier, a cylindrical metal shell covering the outer periphery of the catalyst carrier, and a holding member comprising alumina-silica fibers arranged in a gap between the gaps and having a mat shape. In a catalytic converter comprising a sealing material, the holding sealing material contacts a first surface side having a relatively small crystallization rate with the metal shell, and a second surface side having a relatively large crystallization rate. A catalytic converter, wherein the catalytic converter is arranged between the gaps while being in contact with the catalyst carrier.