JP2002349256A - Sealing material for holding catalyst converter and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material for holding a catalyst converter whose quality stability is excellent. SOLUTION: This sealing material 4 for holding a catalyst converter has an alumina-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. Dispersion in the fiber diameter of the alumina-silica fiber 6 is within ±3 μm. Dispersion in the fiber length is within ±4 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a holding seal material for a catalytic converter and a method for manufacturing the same.

[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.

An example of a method for manufacturing the above-described catalytic converter will be briefly introduced here. The spinning solution for the inorganic salt method prepared in advance is supplied to a centrifugal nozzle, and the spinning solution is blown out of the nozzle by centrifugal force acting on the centrifugal nozzle, thereby forming a precursor fiber. Next, the obtained precursor fibers are gathered and gathered in a mat shape. A band-shaped holding sealing material is produced by punching out the mat-shaped assembly with a mold. Next, after winding the holding sealing material around the outer peripheral surface of the catalyst carrier, the catalyst carrier is accommodated in a metal shell. As a result, a desired catalytic converter is completed. Since the holding sealing material is compressed in the thickness direction in such a housed state, a repulsive force (surface pressure) against the compressive force is generated in the holding sealing material. When the repulsive force acts, the catalyst carrier is held in the metal shell.

[0005]

However, when the ceramic fibers are formed by the blow-off method as described above, the positional dependence of the basis weight (weight per unit area) of the mat-like aggregate increases. That is, since the degree of fiber accumulation is not constant, if the position where the mat-shaped aggregate is punched is different, the surface pressure value of the obtained holding sealing material is also different.
Therefore, a holding sealing material having excellent quality stability could not be obtained.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a holding seal material for a catalytic converter having excellent quality stability. Another object of the present invention is to provide a manufacturing method suitable for obtaining the above-mentioned holding sealing material for a catalytic converter.

[0007]

According to a first aspect of the present invention, there is provided a catalyst carrier comprising a mat-shaped alumina-silica fiber as a component, and a catalyst carrier and the catalyst carrier. A catalytic converter holding sealing material disposed in a gap with a metal shell covering the outer periphery of
The variation in fiber diameter of the alumina-silica fiber is ± 3.
A gist of the present invention is a catalytic converter holding seal material having a thickness of not more than μm.

According to the second aspect of the present invention, there is provided a catalyst 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. A gist of the present invention is a holding sealing material for a catalytic converter, wherein the variation in the fiber length of the alumina-silica fiber is within ± 4 mm.

According to a third aspect of the present invention, there is provided a catalyst 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. A converter holding seal material, wherein the alumina-silica fiber has a fiber diameter variation of ± 3 μm or less and a fiber length variation of ± 4 mm or less. Make a summary.

[0010] The invention according to claim 4 is the invention according to claims 1 to 3.
In any one of the above items, the shot content is 3% by weight or less. According to the fifth aspect of the present invention, the alumina-silica-based fibers assembled in a mat form as constituent elements, and the catalyst converter holding member is disposed in a gap between the catalyst carrier and a metal shell covering the outer periphery of the catalyst carrier. A sealing material, wherein the average fiber diameter of the alumina-silica fiber is 5 μm to 15 μm and the variation of the fiber diameter is within ± 3 μm, the average fiber length is 5 mm to 20 mm, and the variation of the fiber length is ± 4 mm. SUMMARY OF THE INVENTION A gist of the present invention is a catalytic converter holding seal material containing no shot.

According to a sixth aspect of the present invention, there is provided a method for producing the holding sealing material for a catalytic converter according to any one of the first to fifth aspects, wherein an undiluted spinning solution containing an aluminum salt aqueous solution, a silica sol and an organic polymer is supplied from a nozzle. A spinning step of obtaining long fibers of the precursor fiber by continuous ejection, a cutting step of chopping the long fibers to a predetermined length to obtain short fibers, and a mat by gathering the short fibers three-dimensionally. A method of manufacturing a holding sealing material for a catalytic converter, comprising a forming step of forming a fibrous aggregate and a firing step of heating and sintering the mat-like fibrous aggregate.

The "action" of the present invention will be described below. According to the first aspect of the present invention, in the case of a holding sealing material composed of alumina-silica-based fibers having a fiber diameter variation within ± 3 μm, the fibers are likely to be uniformly accumulated, and the position of the basis weight depends on the position. Is less effective. Therefore, the variation in the surface pressure value is reduced, and the quality is stable.

According to the second aspect of the present invention, in the case of a holding sealing material composed of alumina-silica fibers having a fiber length variation within ± 4 mm, the fibers are easily accumulated uniformly, and the basis weight is increased. Is less dependent on position. therefore,
The variation in the surface pressure value is reduced, and the quality becomes stable.

According to the third aspect of the present invention, the position dependency of the basis weight is further reduced due to the synergistic effect of reducing both the variation in the fiber diameter and the variation in the fiber length, and the variation in the surface pressure value is further reduced. Become smaller.

According to the present invention, the content of shot (non-fibrous) in the holding sealing material is 3% by weight.
From the following, the position dependency of the basis weight is further reduced, and the variation in the surface pressure value is further reduced.

According to the fifth aspect of the invention, the positional dependency of the basis weight is extremely low, and the variation in the surface pressure value is further reduced, and the surface pressure and the sealing performance can be improved. .

If the average fiber diameter is less than 5 μm, not only the strength of the fiber itself becomes low and it becomes difficult to obtain a sufficient surface pressure, but also the fiber is easily inhaled into the respiratory system. When the average fiber diameter is more than 15 μm, the airflow resistance becomes small when a mat-like fiber aggregate is formed, and the sealing property is deteriorated. In addition, the fracture strength may be reduced. This is considered to be due to an increase in small scratches accompanying an increase in the fiber surface area.

[0018] When the average fiber length is less than 5 mm, there is a disadvantage that the fibers are easily sucked into the respiratory system. In addition, the characteristics of the fibers are no longer substantially exhibited, and when the mat-like fiber aggregate is formed, suitable entanglement does not occur between the fibers, and it becomes difficult to obtain a sufficient surface pressure. When the average fiber length is more than 20 mm, the entanglement between the fibers becomes too strong, so that the fibers are likely to be unevenly accumulated when a mat-like fiber aggregate is formed. That is, the position dependency of the grammage is increased, which is a factor that hinders a reduction in variation in the surface pressure value.

When shots are contained, the dependence of the basis weight on the position increases, which is a factor that hinders a reduction in variation in the surface pressure value. According to the sixth aspect of the present invention, since the spinning is performed by the inorganic salt method, the fiber diameter can be controlled in a narrow range by appropriately setting the shape and size of the discharge portion. Therefore, variation in fiber diameter can be reduced. In addition, since the method is a method of obtaining short fibers by chopping long fibers, the fiber length can be controlled in a narrow range, unlike the method of obtaining fibers by blowing away.
Therefore, variation in fiber length can be reduced.
In addition to this, the occurrence of a shot can be avoided. Therefore, according to this manufacturing method, the above-mentioned holding sealing material can be easily and reliably obtained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A catalytic converter for an automobile exhaust gas purifying apparatus according to an embodiment of the present invention will now be described with reference to FIGS.
This will be described in detail with reference to FIG.

The catalytic converter 1 of this embodiment shown in FIG. 3 is provided in the body of an automobile at a position midway in the exhaust pipe of the 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 And a holding sealing material 4 arranged in the gap.

The catalyst carrier 2 is made of a ceramic material represented 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, when the winding method is employed 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 aggregates) gathered in a mat shape. In the present embodiment, alumina-silica fibers 6 are used as the ceramic fibers. In this case, the alumina-silica fiber 6 having a mullite crystal content of 0% by weight or more and 10% by weight or less is used.
It is more preferable to use This is because such a chemical composition reduces the amount of the amorphous component, thereby improving the heat resistance and increasing the repulsive force when a compressive load is applied. Therefore, even when a high temperature is encountered in a state where it is arranged in the gap, a decrease in the generated surface pressure is relatively unlikely to occur.

The possible range of the alumina content in the alumina-silica fiber 6 is 50% by weight to 100% by weight, and the possible range of the silica content is 0% by weight to 50% by weight. However, alumina 68% by weight to 83% by weight
And silica is preferably 32% by weight to 17% by weight,
Specifically, it is more preferable that Al ₂ O ₃ : SiO ₂ = 72: 28.

When the amount of alumina is less than 68% by weight or the amount of silica exceeds 32% by weight, it may not be possible to sufficiently improve the heat resistance and the resilience when a compressive load is applied. Similarly, when the alumina is more than 83% by weight or the silica is less than 17% by weight,
There is a possibility that the improvement in heat resistance and the improvement in repulsion force when a compressive load is applied may not be sufficiently achieved.

The average fiber diameter of the alumina-silica fiber 6 is preferably 5 μm to 15 μm, and the dispersion of the fiber diameter is preferably within ± 3 μm. In this case, it is more preferable that the average fiber diameter is 7 μm to 12 μm and the variation of the fiber diameter is within ± 2 μm.

If the average fiber diameter is less than 5 μm, not only the strength of the fiber itself becomes low and it becomes difficult to obtain a sufficient surface pressure, but also the fiber is easily sucked into the respiratory system. When the average fiber diameter is more than 15 μm, the airflow resistance becomes small when a mat-like fiber aggregate is formed, and the sealing property is deteriorated. In addition, the fracture strength may be reduced. This is considered to be due to an increase in small scratches accompanying an increase in the fiber surface area. Note that even when the fiber diameter variation exceeds ± 3 μm, the fibers are likely to be unevenly accumulated, and the position dependency of the basis weight is increased.

The average fiber length of the alumina-silica fiber 6 is preferably 5 mm to 20 mm, and the variation of the fiber length is preferably within ± 4 mm. In this case, it is more preferable that the average fiber length is 8 mm to 13 mm and the variation of the fiber length is within ± 2 mm.

When the average fiber length is less than 5 mm, there is a disadvantage that the fibers are easily sucked into the respiratory system. In addition, the characteristics of the fibers are no longer substantially exhibited, and when the mat-like fiber aggregate is formed, suitable entanglement does not occur between the fibers, and it becomes difficult to obtain a sufficient surface pressure. When the average fiber length exceeds 20 mm, the entanglement between the fibers becomes too strong, so that the fibers are likely to be unevenly accumulated when the mat-like fiber aggregate is formed. That is, the position dependency of the grammage is increased, which is a factor that hinders a reduction in variation in the surface pressure value. The variation in fiber length is ± 4 mm
Also in the case of exceeding, the fibers tend to accumulate unevenly, and the position dependency of the basis weight increases.

The shot content in the holding sealing material 4 is preferably 3% by weight or less, particularly preferably 0% by weight, that is, it is desirable that no shot is contained. This is because, when shots are contained, the position dependency of the basis weight increases, which is a factor that hinders a reduction in variation in the surface pressure value.

The tensile strength of the alumina-silica fiber 6 itself is 0.1 GPa or more, especially 0.5 GPa.
GPa or more is preferable. 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 elliptical shape, a substantially triangular shape, etc.).

Holding seal material 4 in state before assembly
Is about 1.1 times to 4.0 times the gap formed between the catalyst carrier 2 and the metal shell 3, and more preferably 1.5 times to
It is desirably about 3.0 times. The thickness is 1.1
If the ratio is less than twice, 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 for imparting spinnability to the spinning dope.

An antifoaming agent or the like may be added to the spinning dope. The chemical composition of the alumina-silica fiber 6 can be controlled to some extent by changing the ratio of the aluminum salt and the silica sol.

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, the prepared spinning dope is continuously jetted from the nozzle of the spinning device into the air, and the formed precursor fiber is wound while being drawn. In this case, for example, a dry pressure spinning method is preferably employed.

The fiber diameter can be controlled in a narrow range by fixing the discharge conditions, stretching conditions, and winding conditions and appropriately setting the cross-sectional shape and size of the nozzle discharge portion. This contributes to a reduction in fiber diameter variation.

Subsequently, the long fibers of the precursor fibers obtained through the above steps are chopped to a length of about 0.5 mm to 10 mm to be shortened. The merits of such a short fiber shortening method are that the fiber length can be controlled to a narrow range so that the dispersion of the fiber length can be reduced, and the occurrence of shots can be avoided. In other words, the length of the obtained short fiber is
Basically, it depends on the mechanical accuracy of the cutting device, and its variation width is very small.

Thereafter, the staple fibers are collected, defibrated and laminated, or the fiber dispersion obtained by dispersing the staple fibers in water is poured into a molding die and dried by pressing and drying. A mat-like fiber aggregate is obtained.

Next, a firing step is performed to ceramicize (crystallize) the mat-like fiber aggregate, whereby the precursor fiber is cured to obtain the alumina-silica fiber 6. In the firing step, it is desirable to set firing conditions such that the mullite crystal content in the obtained alumina-silica fiber 6 is 10% by weight or less. For example, the firing temperature in the firing step is preferably set to 1000 ° C to 1300 ° C. If the firing temperature is lower than 1000 ° C., the precursor fiber cannot be completely dried and sintered, and it becomes impossible to reliably impart excellent heat resistance and a high repulsion force when a compressive load is applied to the holding sealing material 4. There is a risk.
Conversely, if the firing temperature exceeds 1300 ° C., mullite crystallization in the alumina-silica fiber 6 tends to proceed. For this reason, it is difficult to suppress the mullite crystal content to 10% by weight or less, and there is a possibility that excellent heat resistance and a high repulsive force when a high compressive load is applied cannot be reliably applied to the holding sealing material 4.

Further, the fiber assembly is punched into a predetermined shape to form a holding seal material 4. After that, if necessary, after impregnating the holding sealing material 4 with the organic binder,
Further, 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.

[0051]

EXAMPLES AND COMPARATIVE EXAMPLES (Examples) In the examples, samples for evaluating the surface pressure of the holding sealing material 4 were prepared as follows.

First, a basic aluminum chloride aqueous solution (2
3.5% by weight), silica sol (20% by weight, silica particle size 15 nm), polyvinyl alcohol (10% by weight) and an antifoaming agent (n-octanol) were mixed to prepare a spinning dope. Next, the obtained spinning stock solution was concentrated under reduced pressure at 50 ° C. using an evaporator to obtain a concentration of 38% by weight and a viscosity of 1000%.
It was prepared into a spinning solution of poise to 2000 poise.

The prepared spinning dope was continuously jetted from the nozzle of the spinning device into the air, and the formed precursor fiber was wound while being drawn. At that time, the following conditions were set for the purpose of controlling the fiber diameter. That is, the diameter of the nozzle discharge part is set to 0.1 mm to 0.2 mm, the length is set to 0.3 mm to 2.0 mm, and the discharge speed is set to 1.5 cm / s to 2.0 cm / s. The spinning solution was discharged. After stretching the precursor fiber derived from the spinning stock solution at a speed of 100 to 200 times the discharge speed, it was wound by a winder having a diameter of about 12 cm. A tube of 2 m to 4 m was provided between the nozzle discharge portion and the winder, and the precursor fiber was passed through the tube. The temperature in the upper half of the cylinder was set to 35 ° C to 40 ° C, and the temperature in the lower half of the cylinder was set to 25 ° C to 30 ° C.

Subsequently, using a guillotine cutter, the long fibers of the precursor fibers were chopped to a length of 10 mm to shorten the fibers. Thereafter, the short fibers (approximately 1.0 g) are dispersed in water, and the obtained fiber dispersion is poured into a molding die, followed by pressing and drying to obtain a mat-like fiber aggregate having a length and width of 25 mm square. Was.

Further, in an electric furnace maintained in an air atmosphere, the mat-like fiber assembly
After heating (pretreatment) for 1 minute,
The firing was performed at 250 ° C. for 10 minutes.

As a result, a sample of the holding sealing material 4 comprising the perfect circular alumina-silica fiber 6 having a mullite crystal content of about 8% by weight and an alumina / silica weight ratio of 72:28 was obtained.

Alumina-silica fibers 6 were sampled from a plurality of locations in the sample of the example thus obtained, and the average fiber diameter (μm), its minimum and maximum values, the average fiber length (mm) and The minimum and maximum values and the shot content (%) were determined. Table 1 shows the results. According to this, in the examples, it was confirmed that the variation in the fiber diameter and the variation in the fiber length were extremely small, and were within the above-mentioned preferred ranges. Also, no shot was included in the sample.

Next, a plurality of 25 mm square samples were punched out from one large mat-like fiber aggregate, the basis weight was determined based on the area and weight thereof, and the surface pressure was measured by an autograph. These results are also shown in Table 1. Here, the measured surface pressure values are data when the GBD is set to 0.30 g / cm ³ . According to this, in the examples, it was confirmed that the variation in the basis weight and the variation in the surface pressure were small and the quality was stable. In addition, it was found that the average surface pressure value itself also increased. (Comparative Example) In a comparative example, the same spinning solution as in the example was concentrated under reduced pressure at 50 ° C. using an evaporator to obtain a concentration of 38% by weight.
It was prepared into a spinning stock solution having a viscosity of 10 poise to 100 poise.

As a spinning device, 0.2 mm to 0.8 m
50mm diameter with 16 ejection holes of m
A disc-shaped centrifugal nozzle of １００100 mm was used. Then, the spinning stock solution was discharged by the centrifugal force when the nozzle was rotated at a rotation speed of 1000 rpm to 2,000 rpm, and fiberized. Further, the obtained precursor fiber is 0.5 kPa-
It was blown with air at 1.0 kPa and 30 ° C., collected, and laminated to obtain a mat-like fiber aggregate. This was formed into a 25 mm square and then pre-treated and fired under the same conditions as in the above-mentioned example to make it ceramic.

Alumina-silica fibers 6 were sampled from a plurality of locations in the sample of the comparative example obtained by such a blowing method, and the average fiber diameter (μm), its minimum and maximum values, and the average fiber length (mm) were obtained. ), Its minimum and maximum values, and shot content (%). Table 1 shows the results. According to this, it was confirmed that in the comparative example, the variation in the fiber diameter and the variation in the fiber length were considerably larger than those in the examples. In addition, shots of 3% by weight or more were included in the sample.

Next, a plurality of 25 mm square samples were punched out from one large mat-like fiber aggregate, the basis weight was determined based on the area and weight thereof, and the surface pressure was measured by an autograph. These results are also shown in Table 1. Here, the measured surface pressure values are data when the GBD is set to 0.30 g / cm ³ . According to this, it was confirmed that in the comparative example, the variation in the basis weight and the variation in the surface pressure were larger than those in the example, and the quality was unstable. Moreover, the average surface pressure value was considerably lower than that of the example.

[0062]

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

(1) In the holding sealing material 4 of the present embodiment,
Variation in fiber diameter of alumina-silica fiber 6 is ± 3μ
m, the variation in fiber length is within ± 4 mm, and the shot content is 3% by weight or less. Therefore, due to these synergistic effects, the positional dependence of the grammage becomes extremely low, and the variation in the surface pressure value can be made very small. Therefore, it is possible to realize the holding seal material 4 that is stable in quality.

(2) According to the holding sealing material 4 of the present embodiment, since the surface pressure value itself is improved in addition to the variation in the surface pressure value, one holding sealing material 4 can be manufactured. The amount of the alumina-silica-based fiber 6 required for the process is small. Therefore, the cost of the holding sealing material 4 can be reduced.

(3) According to the production method of the present embodiment, the fiber diameter can be controlled in a narrow range because the spinning is performed by the inorganic salt method, and the fiber diameter variation can be reduced. In addition, since the method is a method of obtaining short fibers by mechanically chopping long fibers, the fiber length can be controlled in a narrow range, unlike the method of obtaining fibers by blowing away. Therefore, variation in fiber length can be reduced. In addition to this, the occurrence of a shot can be avoided. Therefore, according to this manufacturing method, the holding sealing material 4 can be easily and reliably obtained.

As apparent from the above, it can be said that the manufacturing method of this embodiment is a very suitable method for obtaining the above-mentioned holding sealing material 4. The embodiment of the present invention may be modified as follows.

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

The composition of the stock solution for spinning is not limited to those exemplified in the embodiment, and may be arbitrarily changed as long as the spinnability and the physical properties of fibers are not significantly reduced. .

Instead of the method of the embodiment in which the long fibers of the precursor fibers are chopped into short fibers and then fired, firing may be performed before chopping the long fibers into short fibers.

The long fibers may be cut using a mechanical cutting device other than the guillotine cutter. In the embodiment, the example in which the holding sealing material 4 of the present invention is used for the catalytic converter 1 for an exhaust gas purifying device has been described. 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, technical ideas grasped by the above-described embodiment will be listed below. (1) a spinning step of continuously discharging a spinning solution containing an aqueous solution of an aluminum salt, a silica sol and an organic polymer from a nozzle to obtain a long fiber of a precursor fiber; A method for producing a ceramic short fiber having a small fiber length variation and a small fiber diameter variation, comprising a cutting step of obtaining a fiber and a firing step of heating and sintering the short fiber.

[0072]

As described in detail above, according to the first to fifth aspects of the present invention, it is possible to provide a holding sealing material for a catalytic converter having excellent quality stability.

According to the sixth aspect of the present invention, it is possible to provide a manufacturing method suitable for obtaining the above-mentioned holding sealing material for a catalytic converter.

[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 partial sectional view of the catalytic converter of the embodiment.

[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.

Continued on the front page F term (reference) 3G091 AA02 AB01 BA39 GB10Z HA27 HA29 4D048 BB18 CC04 CC06 CC08 CC10 4G069 AA20 EE01

Claims (6)

[Claims] 1. A holding seal material for a catalytic converter, comprising an alumina-silica fiber assembled 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. A variation in the fiber diameter of the alumina-silica fiber is within ± 3 μm. 2. A holding material for a catalytic converter, 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. A variation in fiber length of the alumina-silica fiber is within ± 4 mm. 3. A holding material for a catalytic converter, comprising alumina-silica fibers aggregated in a mat shape as components, and disposed in a gap between a catalyst carrier and a metal shell covering the outer periphery of the catalyst carrier. And a variation in fiber diameter of the alumina-silica fiber is within ± 3 μm, and a variation in fiber length is within ± 4 mm. 4. A holding sealing material for a catalytic converter according to claim 1, wherein the shot content is 3% by weight or less. 5. A holding seal material for a catalytic converter, comprising alumina-silica-based fibers assembled in a mat shape as components, and disposed in a gap between a catalyst carrier and a metal shell covering the outer periphery of the catalyst carrier. The average fiber diameter of the alumina-silica fiber is 5 μm to 15 μm, the dispersion of the fiber diameter is within ± 3 μm, and the average fiber length is 5 mm to 2 μm.
A holding seal material for a catalytic converter, characterized in that it has a variation of 0 mm and a fiber length within ± 4 mm and does not contain a shot. 6. A method for producing a holding sealing material for a catalytic converter according to claim 1, wherein a stock solution for spinning containing an aqueous solution of aluminum salt, silica sol and an organic polymer is continuously discharged from a nozzle. A spinning step of obtaining precursor fiber long fibers, a cutting step of chopping the long fibers into a predetermined length to obtain short fibers, and forming the short fibers three-dimensionally into a mat-like fiber aggregate. And a sintering step of heating and sintering the mat-shaped fiber aggregate to produce a holding seal material for a catalytic converter.