WO2005121519A1

WO2005121519A1 - Holding web for an exhaust gas processing unit, associated device, production method and exhaust line

Info

Publication number: WO2005121519A1
Application number: PCT/FR2005/001113
Authority: WO
Inventors: Christian Sarda; Sylvain Pellissard
Original assignee: Faurecia Systemes D'echappement
Priority date: 2004-05-05
Filing date: 2005-05-03
Publication date: 2005-12-22
Also published as: JP2007536081A; KR20070039876A; DE112005001010T5; US20070269354A1; FR2869948A1; FR2869948B1

Abstract

The web (8) is arranged around a processing unit (14) between said processing unit (14) and an envelop (16) which defines a conduit (12) for the exhaust gas flow. The web (18) comprises a mattress whose external side is provided with an aluminosilicate-containing coating (30). The invention is used for motor vehicle exhaust lines.

Description

Support sheet for an exhaust gas treatment device, device, manufacturing method and associated exhaust line.

The present invention relates to a support ply of an engine exhaust gas treatment device, intended to be arranged around the treatment device between the treatment device and an envelope which delimits a circulation duct exhaust gases, the sheet comprising a mattress having an exterior coating. In order to clean up thermal engines, in particular diesel or petrol engines of motor vehicles, it is known to equip the exhaust line with one or more gas treatment devices, in particular catalytic treatment devices and / or devices incorporating particle filters. The treatment unit, made up depending on the case of a particulate filter or a catalytic purification unit, is arranged in a gas circulation duct delimited by an external envelope. To ensure the retention of the treatment member, and whatever the expansion conditions, it is known to interpose an intermediate ply between the treatment member and the envelope. This sheet may be of the intumescent type (IbidenlOO or XPEAV2 for example) or of the non-intumescent type (Ecoflex 200 ™ or Flec N263 ™ for example). The ply ensures on the one hand, the transverse maintenance of the treatment member with respect to a longitudinal axis of the envelope, and on the other hand the axial maintenance of this member by clamping in the envelope. Such devices are not entirely satisfactory. In fact, under the action of the exhaust gases, the sheet erodes when the exhaust pipe is used, which can adversely affect the maintenance of the processing member in the envelope. The main object of the invention is therefore to propose a support ply which ensures the maintenance of the processing member in the envelope in a reliable manner during prolonged use of the device. To this end, the subject of the invention is a sheet of the aforementioned type, characterized in that the coating comprises an aluminosilicate. According to particular embodiments, the sheet comprises one or more of the following characteristics: - the aluminosilicate comprises an alumina silicophosphate; the aluminosilicate comprises between 40% and 60% by mass of silica oxide, between 10% and 30% by mass of phosphorus oxide and between 10% and 30% by mass of aluminum oxide relative to the total mass of aluminosilicate; - the aluminosilicate also comprises between 5% and 10% by mass of sodium oxide and / or potassium oxide and between 0.5% and 2% by mass of iron oxide relative to the total mass aluminosilicate; - The aluminosilicate comprises a poly (silica-oxo-aluminate) having units of general formula: M _n [- (SiO ₂ ) _a - (AIO ₂ ) -] _n , in which n is an integer greater than 1; a is an integer between 1 and 30; and M is a cation chosen from Na ⁺ , K ⁺ , Li ⁺ , Ca ²⁺ , Ba ²⁺ , H ₃ θ ⁺ and their mixtures; the coating is capable of being obtained by a process for applying an aqueous dispersion to the mattress, the aqueous dispersion having a dry extract of between 20% and 50%. The invention further relates to a device for treating the exhaust gases of an engine, characterized in that it comprises: - a casing which delimits a duct for circulation of the exhaust gases; - at least one treatment device, arranged in the conduit; - A ply as defined above, the ply being disposed between the processing member and the envelope around the processing member. According to particular embodiments, the device comprises one or more of the following characteristics: - the ply comprises an upstream transverse face and a downstream transverse face substantially perpendicular to a longitudinal axis of the treatment member, at least one upstream transverse faces and downstream transverse faces having said coating; and - The ply has two side faces bearing respectively on the envelope and the processing member, at least one of the side faces having said coating. The invention further relates to a method for producing a device as described above, characterized in that it comprises the steps of: - at least partially coating one face of the sheet using a binder comprising an aluminosilicate to form the coating; - press the sheet against the processing device; - arrange the treatment unit and the ply in the conduit. The process can also include the following characteristic: - the exterior face is spray coated with the binder. The invention also relates to an exhaust line, characterized in that it comprises a device as defined above. The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the accompanying drawings, in which: - Figure 1 is a view in longitudinal section of a first device treatment according to the invention; and - Figure 2 is a view similar to Figure 1 of a second device according to the invention. In Figure 1 is illustrated an exhaust gas treatment device 10 forming a section of an exhaust line of a vehicle with a thermal engine, such as a diesel engine vehicle. This section includes an exhaust volume 12 containing a first treatment member 14 such as a catalytic purification member or a particle filter. The exhaust volume 12 is delimited by a cylindrical envelope 16 delimiting a passage for circulation of the exhaust gases. The ends of the cylindrical casing 16 are extended by a converging section and a diverging section considering the direction of flow of the gases in the exhaust volume. In all that follows, the terms “upstream” and “downstream” are understood with respect to the direction of circulation of the exhaust gases in the envelope 16. An intermediate ply 18 formed of an intumescent material

(XPEAV2 ™ from Unifrax) is interposed between the processing device 14 and the cylindrical envelope 16. This sheet is formed for example of a mattress of intertwined ceramic fibers, or joined together using a mineral or organic binder. The ply 18 has a thickness of the order of 3 mm. The casing 16, generally cylindrical, has, downstream of the treatment member 14 a cone 20 internally defining a support shoulder for the ply 18 and axial retention of the treatment member 14. In particular, the section outside of the processing member 14 is greater than the inner section of the casing 12, beyond the cone 20. A second processing member (not shown) may be provided in the casing 16, downstream of the first member 14. Depending on the case, it is a catalytic purification device or a particulate filter. It is arranged and in particular retained, like the first member 14, by a peripheral ply. As illustrated in FIG. 1, the ply 18 is of generally tubular shape, for example parallelepipedic. It is able to be wound around the processing member 14. Its cross section is thus of complementary shape to the outer cross section of the processing member 14. The ply 18 has an inner side face 22 and an outer side face 24 arranged respectively in abutment on an external surface of the processing member 14 and on an internal wall of the cylindrical envelope 16. The ply 18 also has at each end an upstream annular transverse face 26 and a downstream annular transverse face 28 substantially perpendicular to a longitudinal axis XX ′ of the treatment member 14. In the example illustrated in FIG. 1, the internal lateral face 22 and the external lateral face 24 have on their surface a coating 30 which comprises an aluminosilicate. The coating 30 based on aluminosilicate increases the coefficient of friction between, on the one hand, the external face 24 of the ply 18 and the casing 16 and on the other hand the internal face 22 and the treatment member 14. In addition, the coating 30 maintains the cohesion of the sheet 18, particularly if the latter consists of interlaced fibers devoid of mineral or organic binder. The coating 30 has a thickness, taken along an axis perpendicular to the longitudinal axis XX 'of less than 2 mm, and preferably between 50 μm and 1 mm. The coating 30 on the interior and exterior faces 22 and 24 is continuous. Alternatively, it has internal porosity. The term "aluminosilicate" denotes a body comprising oxides of silica and oxides of aluminum, preferably chemically bonded, as described below. Preferably, the aluminosilicate comprises an alumina silicophosphate. In the example illustrated, the alumina silicophosphate comprises between

40% and 60% by mass of silica oxide, between 10% and 30% by mass of phosphorus oxide, and between 10% and 30% by mass of aluminum oxide relative to the total mass of aluminosilicate in coating 30. In addition, the alumina silicophosphate comprises between 5% and 10% by mass of sodium oxide and / or potassium oxide and between 0.5% and 2% by mass of oxide of iron relative to the total mass of aluminosilicate in the coating. Preferably, the coating comprises a mineral polymer material, of the poly (silica-oxo-aluminate) or "poly (sialate)" type. This type of mineral polymer comprises a network formed by tetrahedra SiO4 and AIO4 linked alternately by oxygen atoms. This network can be bidirectional or tridirectional. In addition, aluminum is in coordination (IV) in this network. Cations chosen from alkali, alkaline earth or other cations are present in the structural cavities defined by the network to balance the negative charge of aluminum in coordination (IV). Preferably, the cations are chosen from the group consisting of Na ⁺ , K ⁺ , Li ⁺ , Ca ²⁺ , Ba ²⁺ , H ₃ θ ⁺ and their mixtures. Thus, the poly (sialate) has units of general formula: Mn [- (Si0 ₂ ) _a - (AIO ₂ ) -] _n (1) in which: n is an integer greater than 1; a is an integer between 1 and 30; M is a cation chosen from Na ⁺ , K ⁺ , Li ⁺ , Ca ⁺ , Ba ²⁺ , H ₃ O ⁺ and their mixtures. Preferably, the molar ratio between silica and aluminum in the aluminosilicate is greater than 3 and between 3 and 6. This type of poly (sialate) is for example obtained by a process for the polymerization of a base mixture comprising a silicate and aluminosilicate powder and a strongly alkaline aqueous solution of soluble silicate. The silicate and aluminosilicate powder comprises for example an aluminosilicate oxide powder of composition between (2 Si0 ₂ , AIO ₂ ) and (40 Si0 ₂ , AIO ₂ ). The aqueous strongly alkaline silicate solution has for example an M ₂ O / SiO ₂ molar ratio of between or equal to 0.5 and 1, in which M ₂ 0 is either sodium oxide or potassium oxide, or a mixture of sodium oxide and potassium oxide. A metal phosphate preferably chosen from an aluminum phosphate, an iron phosphate, a copper phosphate, a zinc phosphate and their mixtures, is preferably added to the basic mixture before polymerization. Examples of poly (sialate) and of process for obtaining these poly (sialate) are for example described in patent application FR 2 838733. Preferably, the coating 30 is obtained by application of an aqueous dispersion of silicophosphate d alumina on the sheet 18, as described below. This aqueous dispersion has a dry extract of between 20% and 50%. The term “dry extract” designates, for a given sample of aqueous dispersion, the ratio between the mass of dry matter which remains after drying of this sample in an oven at a temperature above 100 ° C., and the initial mass of the sample before drying. In the example illustrated in FIG. 2, the aqueous dispersion of alumina silicophosphate applied to the sheet 18 to form the coating

30 is the binder Géopolymite ^® CT AB 04 from the French company GEOPOLYMERE.

This binder has a dry extract of 35%, and an oxide composition illustrated in the table below.

A method of producing the device 10 shown with reference to FIG. 1 will now be described by way of example. Initially, the lateral faces 22 and 24 of a ply intumescent XPEAV2 ™ 18 type of the company UNIFRAX, are coated with the aqueous binder dispersion GEOPOLYMITE ^® CTAB 04. This coating may be carried out by soaking the web 18 in a container containing the binder or by spraying the binder on the faces of the sheet 18. The soaking allows the coating of all the faces of the sheet

18, while the spraying allows a selective coating of one or more faces of the web 18. The method then comprises a heat treatment step in an oven at 120 ° C for one hour. Alternatively, the heat treatment step can be omitted. The coating thus formed has a thickness of less than 10 mm. The ply 18 is then wound around the processing member 14, bearing on the exterior surface of this member 14. Then, the assembly formed by the processing member 14 and the ply 18 is forcefully introduced into the envelope 16. The sheet 18 and the processing member 14 are held in the envelope 16 by clamping. As previously specified, the coating 30 based on aluminosilicate increases the coefficient of friction between, on the one hand, the external face 24 of the ply 18 and the casing 16 and on the other hand the internal face 22 and the member treatment 14. As a result, the relative movement of the treatment member 14 relative to the casing 16 along the longitudinal axis XX 'is greatly limited, even if the pressure of the exhaust gases, downstream of the processing member 14 is high. Furthermore, the coating 30 ensures the cohesion of the fibers forming the sheet 18, particularly if the latter is devoid of mineral or organic binder. The physical and chemical properties of the ply 18 are thus maintained for an extended period of use, at the temperatures of use of the muffler, for example between 400 and 800 ° C. In the second device 40 according to the invention, shown opposite FIG. 2, the coating 30 based on aluminosilicate is disposed on the upstream and downstream annular faces 26 and 28 of the sheet 18. In this variant, the coating 30 is substantially continuous and thus prevents the penetration of exhaust gases within the web 18 which limits its chemical degradation. The method for producing this second device 40 differs from the first method according to the invention by the step of coating the annular faces 26 and 28 of the ply 18 which is carried out after the treatment member 14 and the ply 18 have were inserted into the envelope 16. In this case, the coating has a thickness less than or equal to about 10 mm. The presence of the coating 30 makes it possible, at a lower cost, to maintain the treatment member 14 in position relative to the envelope 16, in a durable manner, while protecting the sheet 18 against erosion. As a variant, all the external faces 22, 24, 26, 28 of the ply 18 have a coating 30 comprising an aluminosilicate.

Claims

CLAIMS 1. Tablecloth (18) for supporting a member (14) for treating the exhaust gases of an engine, intended to be arranged around the treatment member (14) between the treatment member (14 ) and an envelope (16) which delimits an exhaust gas circulation duct (12), the sheet (18) comprising a mattress having an exterior coating (30); characterized in that the coating (30) comprises an aluminosilicate. 2. Tablecloth (18) according to claim 1, characterized in that the aluminosilicate comprises an alumina silicophosphate. 3. Tablecloth (18) according to one of claims 1 or 2, characterized in that the aluminosilicate comprises between 40% and 60% by mass of silica oxide, between 10% and 30% by mass of phosphorus and between 10% and 30% by mass of aluminum oxide relative to the total mass of aluminosilicate. 4. Tablecloth (18) according to any one of the preceding claims, characterized in that the aluminosilicate further comprises between 5% and 10% by mass of sodium oxide and / or potassium oxide and between 0, 5% and 2% by mass of iron oxide relative to the total mass of aluminosilicate. 5. Tablecloth (18) according to any one of the preceding claims, characterized in that the aluminosilicate comprises a poly (silica-oxo-aluminate) having units of general formula: M _n [- (SiO ₂ ) _a - ( AIO ₂ ) -] _n , where n is an integer greater than 1; a is an integer between 1 and 30; and M is a cation chosen from Na ⁺ , K ⁺ , Li ⁺ , Ca ²⁺ , Ba ²⁺ , H ₃ 0 ⁺ and their mixtures. 6. Tablecloth (18) according to any one of the preceding claims, characterized in that the coating (30) is capable of being obtained by a process for applying an aqueous dispersion to the body of the sheet (18) , the aqueous dispersion having a dry extract of between 20% and 50%. 7. Device (10, 40) for treating the exhaust gases of an engine, characterized in that it comprises: - an envelope (16) which delimits a duct (12) for circulation of the exhaust gases; - at least one treatment member (14), disposed in the conduit (12); - A ply (18) according to any one of the preceding claims, the ply (18) being disposed between the processing member (14) and the casing (16) around the processing member (14). 8. Device (40) according to claim 7, characterized in that the ply (18) comprises an upstream transverse face (26) and a downstream transverse face (28) substantially perpendicular to a longitudinal axis (XX ') of the treatment member (14), at least one of the upstream transverse faces (26) and downstream transverse face (28) having said coating (30). 9. Device (10) according to one of claims 7 or 8, characterized in that the ply (18) has two lateral faces (22, 24) bearing respectively on the envelope (16) and the processing member (14), at least one of the side faces (22, 24) having said coating (30). 10. A method of manufacturing a device (10, 40) according to any one of claims 7 to 9, characterized in that it comprises the steps of: - at least partially coating one face (22, 24, 26, 28) of the sheet (18) using a binder comprising an aluminosilicate to form a coating (30), - press the sheet (18) against the treatment member (14), - arrange the member treatment (14) and the web (18) in the envelope (16). 1 1. Method according to claim 10, characterized in that the face (22, 24, 26, 28) is spray coated with the binder. 12. Exhaust line, characterized in that it comprises a device (10, 40) according to any one of claims 7 to 9.