JP2002348740A - Alumina-silica-based fiber, method for producing the same, and maintaining sealant for catalyst converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of simply and certainly producing an alumina-silica-based fiber excellent in mechanical strengths. SOLUTION: A precursor fiber is produced by using an alumina-silica-based fiber dope for the inorganic salt method as a source material. Subsequently, the precursor fiber is heated under a condition in which the oxidation reaction of carbon component included in the precursor fiber is reduced. Thus, a alumina- silica-based fiber 6 is obtained by baking the precursor fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina-silica fiber, a method for producing the fiber, and a holding sealing material for 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, an alumina-silica fiber is spun by a melting method, and then a material is prepared by gathering the alumina-silica fiber in a mat shape. A band-shaped holding sealing material is produced by punching out this material 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, since the conventional holding sealing material is exposed to high temperatures such as vibration and exhaust gas during use, the surface pressure gradually decreases with time, and the holding sealing material is relatively early. There was a drawback that the retention and sealing properties of the catalyst carrier deteriorated. Therefore, alumina
There has been a demand for improving the initial surface pressure and preventing the surface pressure from deteriorating with time by improving the mechanical strength of the silica-based fiber itself.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object of the present invention is to provide a catalytic converter holding seal material having a high initial surface pressure and hardly causing deterioration with time of the surface pressure. is there.

It is a second object of the present invention to provide an alumina-silica fiber suitable for obtaining the above-mentioned holding sealing material because of its excellent mechanical strength, and a method for producing the same. Further, a third object of the present invention is to provide a production method capable of easily and reliably obtaining the above-mentioned alumina-silica fiber having excellent mechanical strength.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor has made intensive studies, and after many trials and errors, fortunately produced alumina-silica fibers having excellent mechanical strength. I came to. The alumina-silica fiber produced in this manner generally has a blackish color, and the properties are clearly different from those of the well-known white transparent alumina-silica fiber. In order to find out the cause of the occurrence of an unusual color, the inventor of the present application has conducted further studies. As a result, it was found that when the amount of residual carbon in the fiber increased, the fiber was colored in a blackish color, and that the presence of such residual carbon would contribute to an improvement in mechanical strength. Thus, the inventor of the present application has further developed the above findings, and has finally arrived at the following invention of the present application.

That is, according to the first aspect of the present invention, a spinning step of obtaining a precursor fiber from an alumina-silica fiber spinning solution for an inorganic salt method, and oxidizing a carbon component contained in the precursor fiber A method for producing an alumina-silica-based fiber, comprising a step of sintering the precursor fiber by heating the precursor fiber in an environment in which the reaction does not easily proceed.

According to a second aspect of the present invention, in the first aspect, the precursor fiber is heated to 1000 ° C. in a nitrogen atmosphere.
〜1300 ° C. According to a third aspect of the present invention, in the first or second aspect, the carbon component contained in the precursor fiber is an organic polymer added as a spinnability imparting agent to the alumina-silica-based fiber spinning solution. It was decided to be derived from coalescence.

The gist of the invention according to claim 4 is an alumina-silica fiber exhibiting a black color. The gist of the invention according to claim 5 is an alumina-silica-based fiber exhibiting a black color derived from a carbon component.

According to the invention of claim 6, the residual carbon content is 1% by weight or more, a black color derived from the residual carbon component is exhibited, and the fiber tensile strength is 1.2 GPa.
As described above, the gist is an alumina-silica fiber having a fiber bending strength of 1.0 GPa or more and a fracture toughness of 0.8 MN / m ^3/2 or more.

According to a seventh aspect of the present invention, the alumina-silica fiber according to any one of the fourth to sixth aspects, wherein the alumina-silica fiber according to any one of the fourth to sixth aspects is assembled as a component, a catalyst carrier and an outer periphery of the catalyst carrier The main object of the present invention is to provide a catalytic converter holding seal material disposed in a gap between the metal shell and the metal shell.

The "action" of the present invention will be described below. According to the first aspect of the present invention, the precursor fiber can be sintered without oxidizing the carbon component in the precursor fiber. For this reason, many carbon components can be left in the fiber, and a fiber having excellent mechanical strength can be easily and reliably obtained.

Incidentally, the carbon component in the precursor fiber is almost completely burned down in the course of reaching the sintering temperature, so that it hardly remains in the alumina-silica fiber obtained through the sintering step. However, when the precursor fiber is heated in an environment in which the oxidation reaction of the carbon component is difficult to proceed, it is considered that carbon remains in the fiber and is incorporated into the ceramic skeleton to some extent.

According to the second aspect of the present invention, an inexpensive nitrogen atmosphere is used as an inert atmosphere during the firing step, so that the manufacturing cost can be reduced. In addition, since the sintering temperature is heated within the above-described preferred range, it is possible to stably obtain a high-strength alumina-silica fiber.

If the heating temperature of the precursor fiber is lower than 1000 ° C., the sintering of the precursor fiber tends to be incomplete, and even if the residual carbon content is large, a high-strength alumina-silica fiber can be stably used. It is difficult to obtain. Conversely, even if the heating temperature of the precursor fiber is set to exceed 1300 ° C.,
Alumina-silica fiber does not lead to remarkable increase in strength, but on the contrary, economic efficiency is reduced.

According to the third aspect of the present invention, the organic polymer not only functions as a spinnability imparting agent, but also provides a precursor fiber for imparting suitable strength to the alumina-silica fiber. Will also serve as a carbon source to be added to the steel. Therefore, there is no need to separately add a carbon source to the spinning dope, and the composition of the spinning dope is not significantly changed. Therefore, there is no fear that the balance of the composition of the stock solution is lost, and the deterioration of the basic physical properties of the alumina-silica fiber can be prevented beforehand. Further, since no additional carbon source is required, the production cost can be reduced. In addition, since the organic polymer is easily dispersed in the spinning dope, the carbon source is uniformly dispersed in the precursor fiber. Therefore, the amount of residual carbon in the obtained alumina-silica fiber becomes uniform, and the mechanical strength is hardly uneven.

Incidentally, this kind of organic polymer is usually 50
Since it is burned off at a temperature of about 0 ° C. to 600 ° C., there is no residue in the alumina-silica fiber obtained through the firing step. However, when the precursor fiber is heated in an environment where the oxidation reaction of the carbon component is difficult to proceed, it is considered that carbon constituting the organic polymer remains in the fiber and is incorporated into the ceramic skeleton to some extent.

According to the invention described in claims 4, 5 and 6,
Alumina-silica-based fibers exhibiting a black color generally have excellent mechanical strength. By using such fibers, it is possible to realize a holding sealing material having a high initial surface pressure and hardly causing deterioration with time of the surface pressure. If the fiber tensile strength, fiber bending strength, and fracture toughness are at least the above values, the alumina-silica fiber is extremely strong against tension and bending, and is supple and hard to break. Therefore, it is possible to further improve the initial surface pressure and surely prevent the surface pressure from deteriorating with time.

According to the seventh aspect of the present invention, since the alumina-silica-based fiber having excellent mechanical strength is used as a constituent element, the holding pressure for the catalytic converter is high in the initial surface pressure and the surface pressure is hardly deteriorated with time. Material can be obtained.

[0022]

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

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 this embodiment basically includes a catalyst carrier 2, a metal shell 3 covering the outer periphery of the catalyst carrier 2, And a holding sealing material 4 arranged in the gap.

The catalyst carrier 2 is made of a ceramic material such as cordierite. 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 where the winding method is adopted 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 mat-shaped ceramic fibers (ie, fiber aggregates). 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 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 fiber 6 of the present embodiment
Is characterized by having a black color unlike normal alumina-silica fibers which are white and transparent. The black color coloring the alumina-silica fiber 6 is derived from the carbon component contained in the spinning dope.

The amount of the carbon component remaining in the alumina-silica fiber 6 is preferably 1% by weight or more, preferably 1% to 20% by weight, more preferably 5% by weight.
-10% by weight. If the residual carbon content is less than 1% by weight, the mechanical strength may not be sufficiently improved. Conversely, if the residual carbon content is too large, the basic physical properties (for example, heat resistance) of the alumina-silica fiber 6 may deteriorate.

The alumina-silica fiber 6 preferably has a fiber tensile strength of 1.2 GPa or more, particularly 1.5 GPa or more. The fiber bending strength is preferably 1.0 GPa or more, particularly preferably 1.5 GPa or more. 0.8 fracture toughness
MN / m ^3/2 or more, particularly good that is 1.3MN / m ^3/2 or more. The reason is that if the fiber tensile strength, fiber bending strength, and fracture toughness increase, the alumina-silica fiber 6 is extremely strong against tension and bending, and is supple and hard to break.

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 dope, and in this embodiment, a component that also plays a role as a carbon source that imparts suitable mechanical strength to the alumina-silica fiber 6. But also. As the organic polymer, a linear polymer containing carbon, such as PVA (polyvinyl alcohol), can be used. The substance serving as a carbon source is not limited to linear polymers only, and any compound containing carbon may be a relatively low-molecular compound having no chain structure (polymer Is not possible).

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.

Next, a baking step is performed to sinter the precursor fiber and turn it into a ceramic (crystallized), whereby the precursor fiber is hardened and the alumina-silica fiber 6 is obtained. In the firing step, it is necessary to heat the precursor fiber in an environment where the oxidation reaction of the carbon component (that is, the organic polymer) contained in the precursor fiber is difficult to proceed. In this embodiment, specifically, the heating is performed under a nitrogen atmosphere which is a typical inert atmosphere.

When heating in a nitrogen atmosphere, the temperature is 1000 ° C. to 1300 ° C., preferably 1050 ° C. to 12 ° C.
The temperature is preferably set to 50 ° C. Heating temperature is 1000 ℃
If it is less than 1, the sintering of the precursor fiber tends to be incomplete, and even if the residual carbon content is large, a high-strength alumina-
It is difficult to obtain the silica fibers 6 stably. Conversely, even if the heating temperature is set to exceed 1300 ° C.,
The alumina-silica-based fiber 6 does not lead to a remarkable increase in strength, but on the contrary, the economic efficiency is reduced.

Subsequently, the long fibers of the alumina-silica fiber 6 obtained through the above-described steps 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. Obtain a fiber assembly. Further, the fiber assembly is punched into a predetermined shape to obtain a black sealing seal material 4.

After that, if necessary, the holding sealing material 4 may be impregnated with an 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.

[0047]

EXAMPLES AND COMPARATIVE EXAMPLES (Example 1) In Example 1, first, a basic aluminum chloride aqueous solution (23.5% by weight), silica sol (20% by weight, silica particle diameter 15 nm)
And a spinning agent, polyvinyl alcohol (10% by weight) was mixed to prepare a spinning solution. Next, the obtained spinning dope was concentrated under reduced pressure at 50 ° C. using an evaporator to prepare a spinning dope having a concentration of 38% by weight 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 while being drawn. Next, after heating the precursor fibers at 250 ° C. for 30 minutes (pretreatment) in an electric furnace maintained at a normal pressure and a nitrogen atmosphere, the interior of the electric furnace is also maintained at a normal pressure and a nitrogen atmosphere. At 1250 ° C. for 10 minutes.

As a result, the weight ratio of alumina / silica was 7
2:28, a perfect circular alumina-silica fiber 6 having an average fiber diameter of 10.5 μm and a residual carbon content of 5% by weight was obtained (see Table 1). When the mechanical strength of the alumina-silica fiber 6 was measured by a conventionally known method, the fiber tensile strength was 2.0 GPa, the fiber bending strength was 1.8 GPa, and the fracture toughness was 1.5 MN / m ^3/2. Was. That is, the alumina-silica fiber 6 of Example 1 had extremely excellent mechanical strength.

When the obtained alumina-silica fiber 6 was observed, it was found that the diameter and the cross-sectional shape were uniform and the quality was extremely stable. The alumina-silica fiber 6 has a black color (so-called carbon black), which is a novel one.

Subsequently, the long fiber of the alumina-silica fiber 6 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 and dried under pressure to obtain a mat-like fiber aggregate. Then, a sample was prepared from this fiber aggregate, and a measurement test on surface pressure was performed as follows.

First, a fiber assembly was punched out into a 25 mm square to prepare a sample for surface pressure measurement, which was sandwiched by a special jig so that the bulk density (GBD) became 0.30 g / cm ³ . The surface pressure measurement sample in this state was kept at an atmospheric pressure of 1000 ° C., and the surface pressure was measured after 1 hour, 10 hours, and 100 hours. In addition, the surface pressure with no clamping and no heating was positioned as "initial surface pressure", and the surface pressure after 100 hours was positioned as "surface pressure after endurance". Further, (surface pressure after endurance / initial surface pressure) × 100 (%) was calculated and defined as the surface pressure aging deterioration rate. Table 1 shows the results.

According to this, in the sample of the first embodiment,
Both the initial surface pressure and the surface pressure after endurance exceeded 100 kPa, and the time-dependent deterioration rate of the surface pressure was within 50%, which was relatively small.
When the sample after 100 hours had passed was observed, the properties of the alumina-silica-based fiber 6 were not particularly changed, and were still black. The residual carbon content also remained at 5% by weight.

After the mat-like fiber assembly was punched into a predetermined shape to actually produce a holding sealing material 4, this was wound around the catalyst carrier 2 and pressed into the metal shell 3. The catalyst carrier 2 has an outer diameter of 130 mmφ and a length of 1
A 00 mm cordierite monolith was used. The metal shell 3 has a thickness of 1.5 mm and an inner diameter of 140 mmφ.
A SUS304 cylindrical member having an O-shaped cross section was used. Catalytic converter 1 assembled in this way
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. The wind erosion performance was also favorable. (Examples 2 and 3) In Examples 2 and 3, alumina-silica-based fibers 6 were produced basically according to the procedure of Example 1 except that the firing temperature and the firing time were changed as shown in Table 1. did. As a result, it was possible to obtain the alumina-silica fiber 6 having extremely excellent mechanical strength.

Further, a sample for measuring surface pressure was prepared, and the initial surface pressure, the surface pressure after endurance, and the surface pressure aging rate were measured.
Good results were obtained as in Example 1 (see Table 1). Of course, no change was observed in color or residual carbon content.

Further, the holding sealing material 4 was prepared as the catalytic converter 1 and mounted thereon, and a continuous operation test was performed. 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. Comparative Example In a comparative example, spinning was performed using a spinning dope having the same composition as in Example 1 to form a precursor fiber. Next, in an electric furnace maintained at normal pressure and in an active atmosphere (atmosphere) containing oxygen, the precursor fiber is heated at 250 ° C. and 30 ° C.
After heating (pre-treatment) for 1 minute, 1250 ° C. in an electric furnace also maintained in an active atmosphere (atmosphere) and normal pressure.
The firing was performed for 10 minutes.

As a result, the weight ratio of alumina / silica was 7
2:28, perfect circular and transparent alumina-silica fiber 6 having an average fiber diameter of 10.2 μm and a residual carbon amount of 0% by weight 6
(See Table 1). The mechanical strength of the alumina-silica fiber 6 was as shown in Table 1, and was about half that of Examples 1 to 3. That is, the alumina-silica fiber 6 of the comparative example was clearly inferior in mechanical strength as compared with Examples 1 to 3.

Further, a sample for measuring the surface pressure was prepared, and the initial surface pressure, the surface pressure after the endurance test, and the deterioration rate with time of the surface pressure were measured.
It was clearly inferior to Examples 1 to 3 (see Table 1).

[0059]

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

(1) The alumina-silica fiber 6 used for the holding sealing material 4 has a black color derived from the carbon component, and has a fiber tensile strength, fiber bending strength,
Excellent in mechanical strength such as fracture toughness. Therefore, by using this, it is possible to realize the holding sealing material 4 in which the initial surface pressure is high and the surface pressure hardly deteriorates with time. Therefore, it is possible to obtain the catalytic converter 1 excellent in the holding performance and the sealing performance of the catalyst carrier 2.

(2) When the catalytic converter 1 is formed using the black alumina-silica fiber 6, even if a black substance such as soot adheres to the holding seal material 4, the holding seal material 4 looks Change is hard to appear. That is, since the holding seal material 4 is black in the first place, there is no significant change in color before and after use. Therefore, it does not give the user the impression of “deteriorated” or “dirty”
This is advantageous in that.

(3) In the manufacturing method of the present embodiment, a firing step of sintering the precursor fiber is performed by heating in an environment where the oxidation reaction of the carbon component contained in the precursor fiber is difficult to proceed. I have. Therefore, many carbon components can be left in the alumina-silica-based fiber 6, and the alumina-silica-based fiber 6 having excellent mechanical strength can be easily and reliably obtained.

(4) In the manufacturing method of this embodiment, an inexpensive nitrogen atmosphere is used as an inert atmosphere when performing the firing step. For this reason, the manufacturing cost of the holding sealing material 4 can be reduced. In addition, since the firing temperature is heated in the above-mentioned preferable range, it is possible to stably obtain the alumina-silica fiber 6 having high strength.

(5) In the case of the production method of the present embodiment, the carbon component contained in the precursor fiber is derived from an organic polymer added as a spinnability imparting agent to the spinning dope. Therefore, there is no need to separately add a carbon source to the spinning dope,
It does not involve a significant change in the composition of the spinning dope. Therefore, there is no fear that the balance of the composition of the undiluted solution may be lost.
Deterioration of the basic physical properties of the silica-based fiber 6 can also be prevented. Further, since no additional carbon source is required, the manufacturing cost of the holding sealing material 4 can be reduced. In addition, since the organic polymer is easily dispersed in the spinning dope, the carbon source is uniformly dispersed in the precursor fiber. Therefore, the amount of residual carbon in the obtained alumina-silica fiber 6 is also uniform, and unevenness in mechanical strength is unlikely to occur.

The embodiment of the present invention may be modified as follows. The environment in which the oxidation reaction of the carbon component does not easily proceed is not necessarily limited to only the inert atmosphere, but also includes, for example, a reduced-pressure atmosphere. This is because if the firing is performed in a reduced-pressure atmosphere, the progress of the oxidation reaction is suppressed as compared with the case where the firing is performed in the normal-pressure atmosphere.

The baking may be performed in an inert atmosphere other than nitrogen, for example, argon, or may be performed under a reduced pressure inert atmosphere. The carbon component contained in the precursor fiber may not be derived from the organic polymer added as a spinnability imparting agent, and may be derived from a carbon source added separately. In this case, the material is not limited to an organic material such as an organic polymer, but may be an inorganic material such as carbon.

The “black-colored” alumina-silica fibers 6 not only refer to black (black) fibers, but also
Also includes those that are black and gray. The shape of the holding sealing material 4 can be arbitrarily changed. For example, the alignment portions 11 and 12 having a concave-convex shape may be omitted and a simpler shape may be adopted.

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 is also
The shape may be changed to an elliptical shape, an elliptical shape, or the like accordingly.

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, technical ideas grasped by the above-described embodiment will be listed below. (1) In Claim 1, in the firing step, the precursor fibers are heated under an inert atmosphere and / or under reduced pressure. Therefore, according to the invention described in the technical idea 1, an alumina-silica fiber having excellent mechanical strength can be stably obtained.

[0072]

As described in detail above, according to the first to third aspects of the present invention, there is provided a manufacturing method capable of easily and reliably obtaining an alumina-silica fiber having excellent mechanical strength. be able to.

According to the second aspect of the present invention, the fibers can be stably obtained while reducing the cost. According to the third aspect of the invention, it is possible to maintain the basic physical properties of the fiber while reducing the cost.

According to the invention as set forth in claims 4 to 6, an alumina-silica-based material suitable for obtaining a holding sealing material which is excellent in mechanical strength and has a high initial surface pressure and is unlikely to cause deterioration with time of the surface pressure. Fiber can be provided.

According to the invention described in claim 7, it is possible to provide a catalytic converter holding seal material having a high initial surface pressure and hardly causing deterioration with time of the surface pressure.

[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.

[Explanation of symbols]

2 ... catalyst carrier, 3 ... metal shell, 4 ... holding seal material for catalytic converter, 6 ... alumina-silica fiber.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/28 B01D 53/36 C F-term (Reference) 3G091 AB01 BA07 GA06 GB01X GB01Z GB05W GB06W GB10X GB10Z GB13X GB15X GB16Z GB17X HA27 HA29 4D048 BB02 BB18 CA07 CC04 CC06 CC08 4G069 AA20 DA06 EA18 EE01 4L037 AT05 CS20 FA01 FA03 FA06 FA12 PA39 PA42 PA45 PF12 PF19 PS12 UA20

Claims (7)

[Claims] 1. A spinning process for obtaining a precursor fiber using an alumina-silica fiber spinning stock solution for an inorganic salt method as a material, and in an environment where an oxidation reaction of a carbon component contained in the precursor fiber is difficult to proceed. And baking the precursor fibers by heating the precursor fibers. 2. The method according to claim 1, wherein the precursor fiber is placed in a nitrogen atmosphere.
The method for producing an alumina-silica fiber according to claim 1, wherein the heating is performed at 000C to 1300C. 3. The carbon component contained in the precursor fiber,
The method for producing alumina-silica-based fibers according to claim 1 or 2, wherein the alumina-silica-based fibers are derived from an organic polymer added as a spinnability-imparting agent to the stock solution for spinning alumina-silica-based fibers. 4. An alumina-silica fiber having a black color. 5. An alumina-silica fiber which exhibits a black color derived from a carbon component. 6. The residual carbon content is 1% by weight or more, a black color derived from the residual carbon component is exhibited, the fiber tensile strength is 1.2 GPa or more, and the fiber bending strength is 1.0% or more.
An alumina-silica fiber having GPa or more and a fracture toughness of 0.8 MN / m ^3/2 or more. 7. A catalyst carrier comprising the alumina-silica fiber according to any one of claims 4 to 6 assembled in a mat shape, and a metal shell covering the outer periphery of the catalyst carrier. Holding seal material for catalytic converter arranged in the gap.