MXPA98010512A - Internal insulating coating self-treatment - Google Patents

Abstract

The present invention relates to a pollution control device for purifying exhaust gases from an internal combustion engine, the pollution control device, which comprises: a housing, a pollution control element disposed within the housing; end cone for connecting the housing with an exhaust pipe of an internal combustion engine, and an insulating cone having an internal surface and an external surface, placed inside the end cone, so that a substantial portion of the inner surface of the insulating cone is exposed to the flow of exhaust gases from the internal combustion engine, characterized in that: the insulating cone comprises inorganic materials that include at least one of the inorganic fibers and the inorganic particles, at least partially fused and sufficiently fused to withstand erosion due to the exposure of such escaping gas flow

Description

INTERNAL SELF-ASSEMBLED INSULATING COVER BACKGROUND OF THE INVENTION The present invention relates to devices of the exhaust system and for the control of contamination, such as catalytic converters, filters or traps of diesel particles, exhaust pipes and the like. In particular, the invention relates to an internal insulating coating used in high temperature applications. The application describes the invention in relation to an internal insulating end cone used to provide a transition from an exhaust pipe to the device for pollution control. The end cone comprises a conical metallic inlet or outlet housing with a cone composed of freestanding fiber placed inside the conical metallic housing. The fiber-based end cone does not require a protective internal conical metal housing. Pollution control devices such as catalytic converters and diesel particulate filters or traps are well known, and are more typically used to purify exhaust gases produced by internal combustion engines. These types of pollution control devices typically comprise a metal housing with a REP. 29017 monolithic element mounted securely inside the frame by an elastic and flexible mounting grid. The use of two types of devices - catalytic converters and diesel particulate filters or traps is currently widespread. The catalytic converters contain a catalyst, which is typically coated on a monolithic structure mounted on the converter. The monolithic structures are typically ceramic, although metal monoliths have also been used. The catalyst oxidizes carbon monoxide and hydrocarbons, and reduces nitrogen oxides in the exhaust gases of automobiles to control atmospheric pollution. Diesel particle filters or traps are wall flow filters, which have monolithic honeycomb structures typically made of porous crystalline ceramic materials. The alternative cells of the honeycomb structure are typically obstructed so that the exhaust gas enters a cell and is forced through the porous wall of the cell and out of the structure through another cell. Due to the relatively high temperatures found in the devices to control contamination, it is important that the device is well insulated. The insulation is typically provided by securely mounting the monolithic member within the frame using an insulating mounting grid comprising a suitable material. In addition, the inlet and outlet cones, which provide a transition from the exhaust pipe to the device for pollution control are also isolated. The inlet and outlet end cones have been previously insulated by providing a double-walled end cone comprising an outer metal housing and an internal metal housing, with a space defined between the internal and external conical housings. A suitable insulating material fills the space between the internal and external conical housings. Examples of double-walled end cones can be seen in, for example, U.S. Patent No. 5,408,828 to Kreucher et al. Kreucher et al., Show a catalytic converter having a double-wall diffuser leading from an exhaust pipe to the catalytic converter. An air barrier of thermal insulation is provided between the inner wall and the outer wall. Another example of double-wall end cones is seen in German Patent No. 3,700,070 Al, which shows an insulating grid placed between an outer and an inner end cone. The use of double-wall end cones has been required due to the nature of the insulating material used in the devices for the control of contamination. In particular, the use of low density fibrous insulation materials requires an internal cone, because exposure to exhaust gases causes rapid erosion and destruction of low density fibrous insulation material. In addition, when the fibrous insulating material is eroded it tends to obstruct the monolithic structure of the device for controlling the contamination and degrade its operation. In this way, the protective inner end cone is required to maintain the position and structural integrity of the insulating material. This is also true with other insulating materials, which have been used, such as ceramic beads, as shown in U.S. Patent No. 5,419,127 to Moore, III. Moore shows an isolated exhaust manifold that has a layer of insulating ceramic beads between an internal and external exhaust manifold. Although they are required to maintain the structural position and integrity of the insulating layer of the inner and outer cones, the use of a protective inner metallic cone has several disadvantages. In particular, the use of an internal metallic cone significantly increases the weight of the device, as well as the cost of manufacturing the device. Therefore, what is needed is an extreme insulating cone that does not require the use of an internal protective cone, and insulating material that resists the damage caused by exposure to exhaust gases and road crashes.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a self-supporting insulating coating for use with the devices of the exhaust and pollution control systems. The application describes the invention in relation to an extreme insulating cone for use with devices for controlling contamination such as catalytic converters and filters or diesel particle traps. The end cone comprises an outer metallic end cone for connection to an exhaust system and a device for controlling contamination. Within the outer end cone there is an insulating cone positioned in such a way that a substantial portion of the inner surface of the insulating cone is exposed to the hot exhaust gases of the internal combustion engine, and the outer face of the insulating cone is placed adjacent to the internal combustion engine. external metallic end cone. The self-supporting insulating coating in this way eliminates the need for an internal metallic coating to protect the insulation. In a preferred embodiment, the insulating coating is formed of a composite material, which utilizes glass or ceramic fibers blended with a binder to create a rigid, insulating end cone, still shock-resistant.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a cross-sectional view of a prior art catalytic converter having internal and external metallic end cones. Figure 2 is a cross-sectional view of a catalytic converter using the end cone of the present invention. Figure 3 is a cross-sectional view of an alternative embodiment of the end cone of the present invention.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the Figures, Figure 1 shows a typical catalytic converter 10 of the prior art. The catalytic converter 10 comprises a metal housing 12 with a generally conical inlet 14 and outlet 16. The housing, which is also known as a can or frame, can be made of suitable materials known in the art, and is typically made of metal. Preferably, the housing is made of stainless steel. Placed inside the housing 12 is a monolithic catalytic element 18 formed of a honeycomb monolithic body, either ceramic or metal. The surrounding monolith 18 is a mounting and insulating grid 22. Referring now to the inlet 14 and the outlet 16, it can be seen that the inlet 14 and the outlet 16 comprise an external end conical housing 26 and an internal end conical housing 28. insulating material 30 is positioned between the outer conical housing 26 and the internal conical housing 28. As discussed above, the internal conical housing 28 was provided in the devices for controlling the prior art contamination to retain the insulating material. in its position and to prevent the insulating material 30 from being damaged by the hot exhaust gases passing through the device for controlling the contamination. However, the use of the internal conical housing 28 adds additional weight, complexity and cost to the device to control contamination. It is therefore desired to make use of the internal conical housing 28 unnecessary. The present invention provides a self-supporting internal insulating coating, and in particular an insulating end cone which does not require the use of an internal conical housing 28. In particular, the present invention uses a refractory material to provide an internal insulating cone, which is resistant to the damage caused by the exhaust gases as well as to the damage caused by the mechanical thermal shock. Useful refractory materials are capable of withstanding large temperature gradients for short periods of time without cracking. Temperature gradients may vary from temperatures below zero to more than 300 ° C for short periods of time, when a vehicle is started until it reaches cruising speed. The present invention utilizes a composite material that has sufficient rigidity to resist erosion of exhaust gases, and that also provides resistance to mechanical and thermal shock. The composite material comprises inorganic fibers and / or inorganic particles. The composition may optionally include one or more additional binders. Fibers useful in the practice of the invention include fibers made from alumina-boria-silica, alumina-silica-alumina-pentaxide phosphorus, zirconia-silica, zirconia-alumina, and alumina. The fibers can be formed by processes known in the industry such as blowing or centrifugation. A useful process is the centrifugation of a sol gel solution. Useful fibers are commercially available under the trademarks of SAFFIL from ICI Chemicals &; Polymers, FIBERMAX of Unifrax Co., ALCEN of Denka, and MAFTECH of Mitsubishi.

The fibers can be used as fibers or can be used as a fibrous mesh. A fiber mesh can be formed by blowing the fibrous material over ~. a collection screen as practiced in the non-woven fabric industry. A commercially available fiber mesh useful is the SAFFIL LD alumina fiber mesh from ICI Chemicals & Polymers. The cone can also be formed from inorganic particulate materials such as clays, ceramic or glass powders, ceramic or glass beads and hollow ceramic or glass spheres. Additionally, combinations of fibers and -particles can be used. The fibers and particles can act as binders. When the fibers and / or particles are heated to high temperatures, for example, of more than 500 ° C, they can melt or soften enough to bind to other fibers and particles in the cone. The fibers and particles can also be sintered. By selecting fibers or particles with different melting points, it is possible to achieve several modes of union between them. For example, a combination of fiberglass and ceramic fiber can be joined because the glass fibers soften and can melt at temperatures lower than the melting temperatures of the ceramic fibers. Additionally, the ceramic fibers can be sintered to other ceramic fibers without substantial melting of the fibers. It may be useful to add other binders to aid processing or to provide greater resistance to elevated temperatures. Organic binders can be used to keep the inorganic material together at room temperature to form the cone. When the cone is heated above about 300 ° C, the organic binder is burned leaving the cone, which can then be burned at elevated temperatures to sinter the inorganic materials together. Organic binders are particularly useful for molding and injection molding processes. Useful organic binders include waxes with low melting temperatures and polyethylene glycol. Inorganic binders can also be used. Those binders include sol and gel sol materials such as alumina sols, colloidal silica suspensions, refractory liners such as silicon carbide suspensions and solutions such as a monoaluminum phosphate solution. Colloidal silica suspensions are commercially available from Nalco Co. under the trademark NALCO. The inorganic binders can be incorporated into the cone by adding the binders to the composition to form the cone, infiltrate a cone formed with the sol or suspension, or by brushing a refractory lining or solution onto a cone surface. Inorganic binders help make cones stiff. When the binder solution or coating is applied only to one surface of the cone, for example, the inner surface, the inner surface becomes stiffer, while the outer surface can still be compressible. In use, binders on the surface can help prevent erosion of the cone by hot exhaust gases. Other adjuvants to assist processing may also be included such as dispersion aids, wetting agents, thickeners and the like. As described below in the Examples, the self-supporting fibrous end cone may be formed in a variety of ways such as with a flexible mold, mold with a mud mold, press-molding or injection molding. Fiber meshes can also be formed in a form similar to papier-mâché in which strips of the fibrous mesh are saturated in a binder solution and placed superimposed on a conical surface. As detailed below, each of these methods of forming the self-supporting fibrous end cone results in a cone, which is resistant to damage from exposure to hot exhaust gases., thermal shock and road shock. The end cone is typically secured within an outer metallic end cone. The metal end cone is made of metals resistant to high temperatures such as stainless steel and Inconel. The end cone can be secured within the outer metallic end cone 2-6 of a device for controlling contamination in a variety of ways. For example, as seen in Figure 2, the fibrous end cone 40 is compressed against the monolith 18 and a mounting grid or mesh 22 so that the fibrous end cone 40 is restrained against movement. Alternatively or in addition to such a friction arrangement, tabs 42 could be used to restrict the fibrous cone 40 within the outer end cone 26, as illustrated in Figure 3. The tabs 42 are shown extending from the exhaust pipe 44, but they could also extend from the end cone 26 or the frame 12, for example. Instead of individual tabs 42, as seen in Figure 3, a solid retaining ring (not shown) could also be used. Of course, the fibrous end cone 40 could be restricted within the outer end cone 26 in a variety of other ways, depending on the particular application desired by the user.

The objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof should not constitute an undue limitation of this invention. All parts and percentages are by weight, unless otherwise stated. Although the examples belong to an extreme insulating cone for use as a catalytic converter, the present invention is equally applicable for use in other areas of an exhaust system, such as diesel particulate filters or traps, exhaust manifolds, and exhaust pipes. escape. The utility of the invention is likewise not limited to the conical shape of the examples, but is useful in any high temperature application where an internal insulating coating is required and the use of a separate internal protective surface is not desired. .

TEST PROCEDURES Hot Vibration Test The Hot Vibration Test was used to evaluate an extreme cone for use with a catalytic converter by subjecting a catalytic converter with the extreme cone to the vibration and hot gas of a gasoline engine (Mode 1) or hot air (Mode 2). The two test modes are described more fully later.

MODE 1 - A catalytic converter, with the end cone securely mounted inside it, was attached to a solid device placed on a vibrating plate (Electrodynamic Vibrating Plate Model TC 208 from Unholtz-Dickie Corp., Allingford, CT). The catalytic converter was then connected through a flexible coupling to the exhaust system of a 7.5-liter V-8 petrol internal combustion engine from Ford Motor Co., coupled to an Eaton 8121 air current dynamometer. The converter was tested using an inlet exhaust temperature of 900 ° C at an engine speed of 2200 rpm with a load of 30.4 kg-meter, while the converter was vibrated at 100 Hz and an acceleration of 30 g on the vibrating plate. The converter was tested under these conditions for 25 hours. The converter was then disassembled and the end cone visually examined for signs of decay, erosion and fracture. For a successful test, the end cone must be intact and exhibit no visible damage. MODE 2 - This test mode was conducted in a similar way to Test Mode 1. A catalytic converter and an extreme cone were mounted on a vibrating board (available from Unholtz-Dickie), which vibrated the converter with an acceleration of 30 g at a frequency of 100 Hz. The heat source is a natural gas burner, which supplies an inlet gas temperature of 900 ° C. The converter was subjected to three heating and cooling cycles (during vibration), where one cycle includes a heating period to reach the gas inlet temperature of 900 ° C, keeping the inlet gas temperature at 900 ° C for a period of 8 hours, and cool to room temperature (approximately 21 ° C). As in Mode 1, the extreme cone must not exhibit any visible signs of damage.

Example 1 Example 1 illustrates how the end cone of ceramic fibers was prepared using a flexible mold and a mixture of fibers with organic binder. (The same composite mixture could also be injection molded). A rubber mold was prepared by mixing 10 parts of a rubber that cures at room temperature (SILASTIC K RTV Silicone Rubber available from Dow Corning Co.) and a part of curing agent (SILASTIC K RTV Curing Agent available from Dow Corning Co.). The rubber mixture was molded around a master steel cone having the desired finished dimensions of the fiber cone. The mold was cured for 24 hours at room temperature (approximately 21 ° C).

The glass fibers (6.35 mm long S-2 Glass Fibers available from Owens-Corning Fiberglas Corp.) were heated, cleaned and crushed to a fiber length of approximately 0.5 mm. Ceramic fibers (ceramic fibers SAFFIL from ICI Chemicals &; Polymers LTD) were milled to a length of about 0.25 mm. A mixture of fibers was prepared by mixing 37.8 grams of each of the crushed glass and ceramic fibers. The fiber mixture was then poured into a planetary mixer (1 gallon Ross Mixer Model LDM available from Charles Ross & Son Co.) with a content of 150 grams of binder (polyethylene glycol 1000 m.w., available from Aldrich Chemical Inc.) and 0.75 grams of a dispersion adjuvant (Dispersant KD-5 available from ICI Americas). The mixture was heated to 100 ° C in the mixer to melt the binder, and then mixed under a vacuum of 25 mm Hg for about 30 minutes. The resulting fiber-binder mixture was poured into a rubber mold, which had been heated to 40 ° C. The filled mold was then placed in a fixed vacuum chamber to a vibrating plate (SYTRON vibrating plate from FMC Corp.). The vacuum chamber was evacuated to 30 mm Hg, and the plate was vibrated for 5 minutes to remove air from the mixture and increase the flow of the mixture into the mold. The mold was then removed from the vacuum chamber and cooled to room temperature. The hardened fiber cone was removed from the mold, packed into a bed of alumina plate beads (1.5 mm diameter beads available from Microcel Technologies, Inc.), and heated at 250 ° C for about 3 hours. The beads were used to prevent the cone from sinking and deforming while a substantial portion of the binder burned. The cone was then removed from the bed and burned in an oven at 1100 ° C for 4 hours to join the fibers in the cone. The cone was cooled to room temperature, inserted into the metal conical housing for a catalytic converter, and subjected to the Hot Vibration Test "- Mode 2 described above.After the test, the cone was found to be intact and it exhibited no fractures or other visible signs of erosion or disintegration.

Examples 2-4 Examples 2-4 illustrate how a ceramic end cone was prepared using a suspension of water and ceramic fibers. For each of Examples 2-4, a conical mold was prepared by cutting and fabricating a perforated metal sheet to the shape of an end cone of a catalytic converter. The mold was then covered with a wire mesh (25 mesh). The end of the largest diameter of the cone was sealed by wrapping the end shot with a filament tape, and the smaller diameter end of the mold was attached to a 3.8 mm diameter vacuum hose of a vacuum cleaner (Shopvac available from Sears). For Example 2, a suspension was prepared by mixing 14 liters of tap water, 200 grams of ceramic fibers (7000M ceramic fibers available from Unifrax Co., Niagara Falls, N.Y.) with an air mixer of approximately 10 minutes. Mixing continuously, 2 liters of a suspension of colloidal silica were added (NALCO 2327 available from Nalco Chemical Co.) and dispersed. The mold was then placed in the suspension and the vacuum was fired for approximately 5 seconds. The mold was removed immediately, after the vacuum was turned off, and a layer of 6.3 mm thick fibers was deposited on the cone. The cone of fibers was removed from the mold and dried at 100 ° C for about 2 hours. The fiber cones of Examples 3-4 were prepared as for Example 2, except that a coating was applied with a brush to the inner surface of each cone. The coatings of Examples 3-4 made the inner surfaces of the cones stiffer while the outer surfaces of the cones remained compressible. In addition to the coatings that were used in Examples 3-4, it was also contemplated that other coatings such as a Silicon Carbide suspension (available from ZYP Coatings, Inc.) could also be used. The coatings for each of the examples were as follows: EXAMPLE 3 Colloidal Silica Suspension (Nalco 2327) Example 4 Monoaluminum Phosphate (50% Solution, Technical Grade available from Rhone-Poulec Basic Chemical Co.) The cones of the Examples 2, 3 and 4 were tested using the Hot Vibration Test described above - Mode 2, and exhibited no fracture, disintegration or erosion.

Example 5 Example 5 illustrates how a ceramic end cone was prepared using a ceramic fiber mesh material. A ceramic fiber mesh (SAFFIL Type LD available from ICI Chemicals &Polymers) was cut into strips measuring approximately 5.1 cm by 10.2 cm. The strips were immersed in a suspension in colloidal silica (NALCO 2327), and applied on the inner surface of an outer metallic conical portion of a catalytic converter.

(The outer end cone acted as a forming mold). The strips were superimposed and placed to form a cone having a thickness of approximately 6.35 mm. An internal cone of the catalytic converter (acting as an inner mold for the strips) was then bent over the layers to sandwich the layers of the mesh material between the outer and inner metal end cones. The assembly was dried at 100 ° C for about 5 hours in an air oven. The inner metallic cone was then removed, and the outer metallic cone with the mesh c * '- each was heated at 900 ° C for about 1 hour to form a cone of rigid fiber. The cone of fiber was removed and then subjected to the Hot Vibration Test - Mode 1. The cone exhibited no fracture, disintegration or erosion. The test results of Examples I- ^ demonstrate that the end cone composed of freestanding fiber can withstand the flows of the exhaust gas and the vibrational movement of a treatment environment after exhaust. In addition to the Examples provided herein, it was also contemplated that the free standing fiber cone may also be formed by additional methods, such as injection molding. Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (9)

1. A device for controlling the pollution for purifying the exhaust gas of an internal combustion engine, the device for controlling the contamination is characterized in that it comprises: a housing, an element for controlling the contamination placed inside the housing, - an end cone for connecting the housing to an exhaust pipe of an internal combustion engine, and an insulating cone having an inner surface and an outer surface, the insulating cone comprises inorganic materials including at least one of inorganic fibers and inorganic particles, at least partially fused together, the insulating cone placed inside the end cone, so that a substantial portion of the inner surface of the insulating cone is exposed to the exhaust gas flow of the internal combustion engine, the insulating cone is sufficiently fused together to resist erosion of exposure to such exhaust gas flow.

2. The device for controlling contamination according to claim 1, characterized in that the insulating cone includes a fibrous binder.

3. The device for controlling the contamination according to claim 2, characterized in that the fibrous binder is made of ceramic fibers.

4. The device for controlling contamination according to claim 1, characterized in that the insulating cone was formed from an inorganic fibrous material.

5. A device for controlling pollution for purifying exhaust gas from an internal combustion engine, the device for controlling the contamination is characterized in that it comprises: a housing, an element for controlling the contamination placed inside the housing, an end cone for connecting the housing to an exhaust system of an internal combustion engine, and a layer of insulating material placed within the end cone, the insulating material comprises at least one inorganic material including inorganic fibers and inorganic particles, at least partially fused together , the insulating material is exposed to the exhaust gas of the internal combustion engine and the inorganic material is sufficiently melted together to resist erosion of the exhaust gas flow

6. A method for forming a self-supporting fibrous end cone to be placed within a metal end cone of a device to control the contamination The method is characterized in that it comprises: providing a mold having the dimensions of the inner surface of an outer metallic conical portion of a device for controlling contamination, saturating strips of a ceramic fiber mesh with a colloidal silica suspension, place the saturated ceramic fiber strips on the internal surface of the mold, - compress the saturated ceramic fiber strips against the mold to provide the desired external and internal diameters of the insulating end cone, cure the composition of ceramic fiber and colloidal silica suspension, and remove the fibrous insulating end cone from the mold.

7. The method of compliance with the claim 6, characterized in that the ceramic fiber strips are superimposed and stratified within the mold. 10. The device for controlling pollution according to claim 1, characterized in that the insulating cone includes at least one inorganic particle selected from the group consisting of clays, ceramic powders, glass powders, ceramic beads, glass beads, hollow spheres of ceramic and glass hollow spheres. The device for controlling the contamination according to claim 1, characterized in that at least one of the inorganic fibers and inorganic particles are sintered together. "" 12. The device for controlling the contamination according to claim 1, characterized in that the insulating cone includes inorganic fibers. The device for controlling contamination according to claim 12, characterized in that the inorganic binders are selected from the group consisting of sol and gel-sol materials. The device for controlling the contamination according to claim 1, characterized in that at least the material defining the inner surface of the insulating cone is treated to form a rigid surface. 15. The device for controlling contamination according to claim 1, characterized in that the inorganic materials are substantially fused together. 25

8. A method for forming an internally self-supporting insulating end cone for use with a device for controlling contamination, the method is characterized in that it comprises: - providing a rubber mold having the desired finished dimensions of the fibrous insulating cone, heating the rubber mold, pour a mixture of glass and ceramic fibers, and inorganic and organic binders into the hot rubber mold, cool the mold to harden the fiber-binder mixture, remove the hardened fiber cone from the mold, heat the hardened fiber cone to remove the organic binders, and bake the hardened cone to sinter the fibers and binders. The device for controlling the contamination according to claim 1, characterized in that the insulating cone includes at least one inorganic fiber selected from the group consisting of alumina-boria-silica, alumina-silica, alumina-phosphorus pentoxide, zirconia- silica, zirconia-alumina, and alumina.