Patent Application
20120313282
The present invention relates to: a holding material for a catalyst converter for holding, in a metal casing, a catalyst carrier used in a catalyst converter for removing particulates, carbon monoxide, hydrocarbons, nitrogen oxides and the like contained in exhaust gas discharged from an internal combustion engine such as a gasoline engine or a diesel engine; and a method for manufacturing the same.
A holding material for a catalyst converter (hereinafter simply referred to as a “holding material”) can be obtained by wet molding an aqueous slurry containing inorganic fibers and an organic binder using a dewatering molding tool having a given shape, and subjecting the resulting molded article to hot press. The holding material is incorporated in a metal casing in a state that the holding material is attached to a catalyst carrier (hereinafter referred to as “canning”). The organic binder contained in the holding material burns out by heat applied after canning, and the inorganic fibers confined in a compressed state by the organic binder expands in a thickness direction, thereby sealing a gap between the catalyst carrier and the casing, and additionally holding the catalyst carrier.
On the other hand, with progress in low-floor structure of automobiles, investigations are made to decrease a space necessary for mounting a catalyst converter by changing a cross-sectional shape of a catalyst carrier incorporated under a floor of automobiles from a true circle to a flattened shape, that is, an ellipse or a track shape. However, there may be cases that a way of heat transmission in the catalyst carrier becomes heterogeneous or residual stress in the production step of a casing varies depending on part of the casing. Therefore, after canning, partial thermal expansion difference occurs in the casing, and therefore, the degree of expansion becomes heterogeneous. As a result, gap difference between the catalyst carrier and the casing becomes heterogeneous, and sealing property and holding force of the holding material are impaired in more expanded sites.
A holding material in which the part contacting an outer periphery in a minor axis direction of a cross-section of a catalyst carrier has a thickness larger than that of the part contacting an outer periphery in a major axis direction thereof is proposed for the catalyst carrier having a cross-section of a flattened shape (see Patent Document 1). However, the holding material disclosed in Patent Document 1 has nonuniform thickness. Therefore, the holding material can be adapted to the system called “clam shell” in which a catalyst carrier having a holding material attached thereto is sandwiched using a casing having a two-sectioned structure, but cannot be applied to a system called “stuffing” in which a catalyst carrier in the state of having a holding material attached thereto is inserted with pressure in an integrated casing.
It is not limited to a holding material for a catalyst carrier having a cross-section of a flattened shape, weight of a catalyst carrier acts downward in a vertical direction to a holding material by the influence of gravity, and as a result, a large deterioration of the part holding the bottom of the catalyst carrier occurs. Furthermore, the holding material receives vibration during motoring. Therefore, the part of the holding material opposite the bottom of the catalyst carrier, that is, the part holding the top of the catalyst carrier is liable to be deteriorated. However, countermeasures to those problems have not hitherto been made in holding materials including the holding material disclosed in Patent Document 1.
The present invention has been made in view of the above circumstances, and has an object to provide a holding material for a catalyst converter, which exhibits sealing property and holding force comparable to the conventional one to a catalyst carrier having a cross-sectional shape of a flattened shape such as an ellipse or a track shape, can be adopted to a stuffing system, and is difficult to be affected by load of the catalyst carrier or vibration during motoring.
In order to solve the above problems, the present invention provides a holding material for a catalyst converter and a method for manufacturing the same.
(1) A holding material for a catalyst converter, in which the catalyst converter contains a catalyst carrier having a cross-section of a flattened shape, a metal casing to which the catalyst carrier is received, and the holding material attached to the catalyst carrier and interposed in a gap between the catalyst carrier and the metal casing, in which
the holding material has a first part positioned in a minor axis direction of the cross-section of the catalyst carrier and having a higher basis weight, a second part positioned in a major axis direction of the cross-section of the catalyst carrier and having a lower basis weight, and a third part having a basis weight gradually decreased toward the second part from the first part.
(2) A method for manufacturing a holding material for a catalyst converter, containing: pouring an aqueous slurry containing inorganic fibers into a dewatering molding tool sectioned into a deeper region, a shallower region, and a region having a depth gradually decreased toward the shallower region from the deeper region; dewatering molding the aqueous slurry to obtain a wet molded article; and drying the wet molded article while compressing the whole wet molded article in a thickness direction.
(3) A method for manufacturing a holding material for a catalyst converter, containing: pouring an aqueous slurry containing inorganic fibers into a dewatering molding tool sectioned into a region having a largest aperture ratio, a region having a smallest aperture ratio, and a region having an aperture ratio gradually decreased toward the region having a smallest aperture ratio from the region having a largest aperture ratio; dewatering molding the aqueous slurry to obtain a wet molded article; and drying the wet molded article while compressing the whole wet molded article in a thickness direction.
(4) A holding material for a catalyst converter, in which the catalyst converter contains a columnar catalyst carrier, a metal casing to which the catalyst carrier is received, and the holding material attached to the catalyst carrier and interposed in a gap between the catalyst carrier and the metal casing, in which
in the holding material, a middle point between a maximum load part to which a load of the catalyst carrier is most applied when the holding material is attached to the catalyst carrier and a minimum load part facing the maximum load part has a lower basis weight, and the basis weight is gradually increased toward the maximum load part and the minimum load part from the middle point.
(5) A method for manufacturing a holding material for a catalyst converter, containing: pouring an aqueous slurry containing inorganic fibers into a dewatering molding tool having a region in which a depth is gradually increased up to a first depth at one side and a region in which a depth is gradually increased up to a second depth at the other side, on the basis of a region having a shallower depth as a starting point; dewatering molding the aqueous slurry to obtain a wet molded article; and drying the wet molded article while compressing the whole wet molded article in a thickness direction.
(6) A method for manufacturing a holding material for a catalyst converter, containing: pouring an aqueous slurry containing inorganic fibers into a dewatering molding tool having a region in which an aperture ratio is gradually increased up to a first aperture ratio at one side and a region in which an aperture ratio is gradually increased up to a second aperture ratio at the other side, on the basis of a region having a smallest aperture ratio as a starting point; dewatering molding the aqueous slurry to obtain a wet molded article; and drying the wet molded article while compressing the whole wet molded article in a thickness direction.
The holding material of the present invention is a holding material for a catalyst carrier having a cross-sectional shape of a flattened shape such as an elliptical shape or a track shape, and, in the case of a catalyst carrier having an elliptical cross-section, the part positioned in a miner axis direction of the elliptical cross-section of the catalyst carrier and, in the case of a catalyst carrier having a track shaped cross-section, the part positioned in a direction of a flattened part of the cross-section of the catalyst carrier have a larger basis weight along its thickness direction, and the basis weight is gradually decreased. Due to such a gradated configuration of the basis weight, the amount of inorganic fibers expanded when thermally expanded is equivalent to the gradated configuration of the basis weight, and a gap between the holding material and the casing is filled over an overall periphery of the catalyst carrier, and the holding force becomes uniform. Furthermore, because the basis weight at the bottom and the top of the catalyst carrier is increased, deterioration of the holding material due to load of the catalyst carrier and vibration during motoring can be suppressed.
The present invention is described in detail below.
As shown in the cross-sectional view of
The term “basis weight” used herein means mass of fibers per unit area. In the holding material of the present invention, the range of the basis weight is not particularly limited so long as the advantage of the present invention can be exhibited, and may be from 450 to 4,500 g/m2. More specifically, the range of the basis weight varies depending on a size of a space (hereinafter also referred to a “gap”) between a catalyst carrier and a casing. For example, when the gap is from 2 to 6 mm, the basis weight may be in a range of from 450 to 1,800 g/m2; when the gap is from 6 to 10 mm, the basis weight may be in a range of from 1,800 to 3,600 g/m2; and when the gap is from 8 to 12 mm, the basis weight may be in a range of from 2,250 to 4,500 g/m2.
The ratio between the basis weight of the higher basis weight part and the basis weight of the lower basis weight part is not particularly limited so long as the advantage of the present invention can be achieved, and the ratio may be from 1.05 to 2.0 times, preferably from 1.1 to 1.8 times, and more preferably from 1.1 to 1.6 times. A casing 20 has a similarity shape of a catalyst carrier 10, and has an elliptical cross-section. Variability of the gap difference between the casing 20 and the catalyst carrier 10 is influenced by dimensional accuracy of the casing 20, residual stress, heating temperature and the like, but is generally 1.5 times or less. For this reason, even though such a gap difference is present, the holding material can uniformly seal over the entire periphery of the catalyst carrier 10 by adjusting the basis weight ratio to the above range.
Considering holding force, heat insulation property, sealing performance and the like, the holding material 1 preferably has a uniform thickness. Specifically, the thickness may be from 5 to 30 mm, and preferably from 6 to 12 mm. Variation of the thickness is preferably ±15% or less, more preferably ±10% or less, and further preferably ±5% or less.
The casing 20 is divided into two parts up and down in the embodiment shown in the figure. However, the holding material 1 can be canned by a stuffing system using an integrated casing. It can be expected that productivity of canning can be improved by making the thickness of the holding material 1 uniform.
When the holding material 1 is interposed in a gap between the catalyst carrier 10 and the casing 20, an average density thereof is preferably from 0.15 to 0.7 g/cm3, more preferably from 0.2 to 0.6 g/cm3, and particularly preferably from 0.25 to 0.5 g/cm3. The holding material 1 can well hold the catalyst carrier 10 by adjusting the average density to the above range.
A low friction sheet 30 having a friction coefficient of from 0.1 to 0.3 may be laminated on an outer periphery near the lowest basis weight part of the holding material 1. According to this constitution, since frictional resistance of both ends shown in the figure of the catalyst carrier 10 is decreased, when inserting with pressure into an integrated casing, the catalyst carrier 10 can smoothly be inserted into the casing. Furthermore, there can be avoided a problem that cracks and wrinkles are generated on an outer surface of the holding material 1 with the lower basis weight part pulled toward outside (casing side), in which the problem results from a decrease of curvature radius of the vicinity of the lower basis weight part when the holding material 1 is attached to the catalyst carrier 10. The cracks and wrinkles on an outer surface of the holding material 1 disturb canning, and are therefore not preferred. The low friction sheet 30 may be laminated on the entire outer surface of the holding material 1.
In the first embodiment, the lower basis weight part of the holding material 1 is only a point shown by the reference numeral 12. However, the lower basis weight part may have a given width as shown in the reference numeral 15 in
As shown in the cross-sectional view of
The thickness of the holding material 1A is preferably uniform, the basis weight ratio between the higher basis weight part and the lower basis weight part is the same as in the first embodiment, and the same low friction sheet may be laminated on the outer periphery of the part contacting the curved part 50.
The catalyst carrier 10A is inserted in a casing 20A having a similarity shape to the catalyst carrier 10A in a state on which the holding material 1A is wound. The casing 20A is an integrated casing.
In the third embodiment, the lower basis weight part of the holding material 1A is only a point shown by the reference numeral F. However, the lower basis weight part may have a given width as shown by the reference numeral 51 in
The catalyst carrier is not limited to have a cross-section of an ellipse or track shape, and may be, for example, a catalyst carrier 10B having a cross-sectional shape obtained by cutting (cutting plane M) such that both ends at the major axis side of an ellipse intersect with the major axis L as shown in
In addition, the catalyst carrier having a cross-section of a flattened shape may have a flattened cross-sectional view in which a circle is flattened out from intersected two diameter sides, or a cross-sectional shape having different elliptical curvature in each site, although not shown.
In each of the above embodiments, the constituent materials of the holding materials 1, 1A and 1B are not limited so long as the constituent materials contain inorganic fibers and an organic binder. If required and necessary, the constituent materials may further contain fillers, an inorganic binder and the like which are conventionally used. Although those kinds are not limited, the preferred examples thereof are shown below.
As the inorganic fibers, use can be made of various inorganic fibers conventionally used in a holding material. For example, alumina fibers, mullite fibers, or other ceramic fibers can appropriately be used. More specifically, the alumina fibers, for example, preferably have Al2O3 content of 90% by weight or more (the remaining is SiO2 component) and low crystallinity based on an X-ray crystallography. The crystallinity may be 30% or less, preferably 15% or less, and more preferably 10% or less. The alumina fibers further preferably have an average fiber diameter of from 3 to 8 μm and a wet volume of 400 cc/5 g or more. The mullite fibers, for example, preferably have a mullite composition having Al2O3 component/SiO2 component weight ratio of from about 70/30 to 80/20, and low crystallinity based on an X-ray crystallography. The crystallinity may be 30% or less, preferably 15% or less, and more preferably 10% or less. The mullite fibers further preferably have an average fiber diameter of from 3 to 8 μm and a wet volume of 400 cc/5 g or more. The other ceramic fibers include silica alumina fibers and silica fibers, and each of them which are conventionally used in a holding material can be used. Further, glass fibers, rock wool or bio-soluble fibers may be blended.
The wet volume is calculated by the following method: 1) A dry fiber material is weighed to be 5 g by a balance having a precision of two places or more of decimals; 2) In 500 ml glass beaker is placed the weighed fiber material; 3) In the glass beaker of 2) above is placed about 400 cc of distilled water with a temperature of from 20 to 25° C., followed by stirring with a stirrer in a careful manner such that the fiber material does not cut, thereby dispersing the fiber material. The dispersion may be conducted using an ultrasonic washing machine; 4) To a 1,000 ml measuring cylinder is transferred the contents in the glass beaker of 3) above and added distilled water up to 1,000 cc in the scale; 5) The opening of the measuring cylinder of 4) above is clogged with hand or the like, and the measuring cylinder is turned upside down to stir while watching out that water does not leak. This operation is repeated 10 times. 6) After stopping the stirring, the measuring cylinder is allowed to stand at room temperature, and a volume of fibers precipitated after 30 minutes is visually measured. 7) The above operation is conducted using three samples, and its average value is taken as a measurement value.
The organic binder may be the conventional organic binders, and use can be made of rubbers, water-soluble organic polymer compounds, thermoplastic resins, thermosetting resins, and the like. Specifically, examples of the rubbers include a copolymer of n-butyl acrylate and acrylonitrile, a copolymer of ethyl acrylate and acrylonitrile, a copolymer of butadiene and acrylonitrile, and butadiene rubber. Examples of the water-soluble organic polymer compounds include carboxymethyl cellulose and polyvinyl alcohol. Examples of the thermoplastic resins include a homopolymer and a copolymer of acrylic acid, acrylic acid ester, acrylamide, acrylonitrile, methacrylic acid and methacrylic acid ester; an acrylonitrile-styrene copolymer and an acrylonitrile-butadiene-styrene copolymer. Examples of the thermosetting resins include bisphenol type epoxy resin and novolak type epoxy resin. Those organic binders can be used in combination of two kinds or more thereof. The amount of the organic binder used is not limited so long as it is an amount capable of binding the inorganic fibers, and may be from 0.1 to 10 parts by mass per 100 parts by mass of the inorganic fibers. Where the amount of the organic binder is less than 0.1 parts by mass, there is a concern that binding force is insufficient, and where the amount exceeds 10 parts by mass, there is a concern that the amount of the inorganic fibers is relatively decreased and holding performance and sealing performance required as a holding material are not obtained. Furthermore, when the amount of an organic component in the holding material is too large, there is also a concern that the organic component in the holding material volatilizes in initial use of an automobile and an amount of hydrocarbon component contained in the gas emitted exceeds the guideline value. The amount of the organic binder used is preferably from 0.2 to 6 parts by mass, and more preferably from 0.2 to 4 parts by mass.
A small amount of organic fibers such as pulp can be blended as the organic binder. Since binding force is increased as the organic fiber is finer and longer, highly fibrilized cellulose, cellulose nanofiber and the like are preferably used. Specifically, the organic fiber has preferably a fiber diameter of from 0.01 to 50 μm and a fiber length of from 1 to 5,000 μm, and more preferably a fiber diameter of from 0.02 to 1 μm and a fiber length of from 10 to 1,000 μm.
The amount of the fibrilized fibers used is not limited so long as it is an amount capable of binding the inorganic fibers, and is from 0.1 to 5 parts by mass per 100 parts by mass of the inorganic fibers. Where the amount of the fibrilized fibers used is less than 0.1 parts by mass, there is a concern that binding force is insufficient, and where the amount exceeds 5 parts by mass, there is a concern that the amount of the inorganic fibers are relatively decreased, and holding performance and sealing performance required as a holding material are not obtained. The amount of the fibrilized fibers used is preferably from 0.1 to 2.5 parts by mass, and more preferably from 0.1 to 1 part by mass.
The fibrilized fibers may be used together with an inorganic binder. The combined use of the fibrilized fibers and the inorganic binder can well bind the inorganic fibers even in the case that the amount of the fibrilized fibers used is decreased in order to avoid the above-described disadvantages due to volatilization of the organic component at the time of use, and therefore can provide a holding material for a catalyst converter that can maintain the thickness equivalent to the conventional one. As the inorganic binder, use can be made of the conventional ones, and examples thereof include glass frit, colloidal silica, alumina sol, sodium silicate, titania sol, lithium silicate and liquid glass. Those inorganic binders can be used in combination of two kinds or more thereof. The amount of the inorganic binder used is not limited so long as it is an amount capable of binding the inorganic fibers, and is from 0.1 to 10 parts by mass per 100 parts by mass of the inorganic fibers. Where the amount of the inorganic binder used is less than 0.1 parts by mass, there is a concern that binding force is not sufficient, and where the amount exceeds 10 parts by mass, there is a concern that the amount of the inorganic fibers is relatively decreased, and holding performance and sealing performance required as a holding material are not obtained. The amount of the inorganic binder used is preferably from 0.2 to 6 parts by mass, and more preferably from 0.2 to 4 parts by mass.
The amount of the organic components contained in the holding material is preferably from 0.3 to 4.0 mass %, more preferably from 0.5 to 3.0 mass %, and particularly preferably from 1.0 to 2.5 mass %, based on the total amount of the holding material. The amount of a volatile gas generated when heat is applied after canning is reduced with decreasing the amount of the organic components in the holding material, which is preferred. The organic components can be defined by ignition loss after heating at 700° C. for 30 minutes.
The form of the holding materials 1, 1A and 1B is not particularly limited and may have a single mat shape (mat-shaped holding material) or may have a cylindrical shape (cylindrical holding material) of which a cross-sectional shape of an elliptical or tack-shaped. A mat-type holding material 1 (1A) is shown in
Each of the above embodiments is not limited to the constitution that both a higher basis weight part positioned downward in a vertical direction in a catalyst carrier and a higher basis weight part positioned upward in a vertical direction have the same basis weight, and the basis weight of the higher basis weight part positioned downward in a vertical direction may be set higher than that of the higher basis weight part positioned upward in a vertical direction, or conversely, the basis weight of the higher basis weight part positioned downward in a vertical direction may be set lower than that of the higher basis weight part positioned upward in a vertical direction.
The catalyst carrier having flattened cross-section is described in each of the above embodiments. In the holding material for a columnar catalyst carrier having circular cross-section, the higher basis weight part and the lower basis weight part can similarly be provided.
As shown in the cross-sectional view of
The present embodiment is also not limited to the constitution that both the higher basis weight part contacting the bottom G of the catalyst carrier 10C and the higher basis weight part contacting the top U have the same basis weight, and the basis weight of the part contacting the bottom G may be set higher than that of the part contacting the top U, or conversely, the basis weight of the part contacting the bottom G may be set lower than the basis weight of the part contacting the top U. One of those constitutions can be selected depending on the deterioration degree of the holding material due to vibration and the deterioration degree of the holding material due to load of the catalyst carrier 10C.
The constituent material of the holding material and the ratio between the higher basis weigh part and the lower basis weight part are the same as in other embodiments. The higher basis weigh part and the lower basis weight part may have a given width, and a low friction sheet 30 may be attached. Furthermore, the holding material can have a cylindrical shape other than a mat shape.
A method for manufacturing the above holding material is described below.
This manufacturing method is a method for manufacturing the holding material 1 shown in
Incidentally, the dewatering molding tool 100 is equipped with a frame surrounding the whole thereof, but the frame is omitted in
Subsequently, the dewatering molding tool 100 is removed. As a result, a wet molded article 200 having a cross-sectional shape that a top T corresponding to the bottom 101 of the dewatering molding tool 100 and a bottom B corresponding to the top 102 of the dewatering molding tool 100 alternatively appear continuously as shown in
Then, the wet molded article 200 is pressed from the upper side of the figure (which is shown by arrow p in
Next, as shown in
In this manufacturing method, the dewatering molding tool 100 may have a wave shape in the side view, in addition to a shape having the bottom 101 and the top 102 alternatively bent as in
This manufacturing method is also a method for manufacturing the holding material 1 shown in
Subsequently, the dewatering molding tool 110 is removed. As a result, a wet molded article 200 having a cross-sectional shape that a top T and a bottom B alternately appear continuously as shown in
Then, similar to the first manufacturing method, the wet molded article 200 is pressed from the upper side of the figure to have a uniform thickness, and then dried, thereby obtaining a long sheet 210 in which the part corresponding to the top T has a higher basis weight and the basis weight is gradually decreased toward the part corresponding to the bottom B of both ends, as shown in
Next, as shown in
This manufacturing method is a method for manufacturing the holding material 1 shown in
Subsequently, the dewatering molding tool 120 is removed. As a result, a wet molded article 200 having a cross-sectional shape that a top T corresponding to a bottom 121 of the dewatering molding tool 120 and a flat part C corresponding to a flat part 122 of the dewatering molding tool 120 are connected through a gradient surface as shown in
Then, similar to the first manufacturing method, the wet molded article 200 is pressed from the upper side of the figure to have a uniform thickness, dried, and then cut, thereby obtaining a mat-shaped holding material. Both ends thereof obtained are processed into a concavo-convex shape as shown in
This manufacturing method is a method for manufacturing the holding material shown in
An aqueous slurry containing constituent materials of the holding material is poured thereto from the upper side of the figure, and the constituent materials of the holding material are deposited to the entire surface of the dewatering molding tool 130 by dewatering molding. Then, the dewatering molding tool 130 is removed, thereby obtaining the wet molded article 200 shown in
Then, similar to the first manufacturing method, the wet molded article 200 is pressed from the upper side of the figure to have a uniform thickness, dried, and then cut, thereby obtaining a mat-shaped holding material. Both ends of the holding material obtained are processed into a concavo-convex shape as show in
This manufacturing method is a method for manufacturing the holding material 1A shown in
Subsequently, the dewatering molding tool 140 is removed. As a result, a wet molded article 300 having a cross-sectional shape that a part 300A corresponding to the planar part 142 of the dewatering molding tool has a large thickness and a part 300B having a thickness gradually decreased toward the center (corresponding to the top K) in response to the gradient surface of the chevron part 141 of the dewatering molding tool is formed at both ends thereof as shown in
Then, similar to the first manufacturing method, the wet molded article 300 is pressed from the upper side of the figure to have a uniform thickness, and then dried, thereby obtaining a sheet 310 having basis weight varied depending on the thickness. Specifically, as shown in
Next, as shown in
This manufacturing method is also a method for manufacturing the holding material 1A shown in
Subsequently, the dewatering molding tool 150 is removed. As a result, a wet molded article 300 in which a part 300A corresponding to the flat part 40 of the holding material 1A is formed and a part 300B corresponding to the curved part 50 of the holding material 1A is formed at both ends of the part 300A, can be obtained.
Then, similar to the first manufacturing method, the wet molded article 300 is pressed from the upper side of the figure to have a uniform thickness, and then dried, thereby obtaining a sheet 310 having a basis weight varied depending on the thickness. Specifically, as shown in
Next, as shown in
This manufacturing method is a method for manufacturing the holding material 1A shown in
Subsequently, the dewatering molding tool 160 is removed. As a result, a wet molded article 300 having a cross-sectional shape that a part 300A corresponding to the planar part 162 of the dewatering molding tool 160 has a large thickness and, continuously to gradient surfaces of which both ends are decreased, a flat part 300C having a smaller thickness is formed as shown in
Then, similar to the first manufacturing method, the wet molded article 300 is pressed from the upper side of the figure to have a uniform thickness, dried, and then cut, thereby obtaining a mat-shaped holding material. Both ends the holding material obtained are processed into a concavo-convex shape as show in
The wet molded article 300 shown in
This manufacturing method is a method for manufacturing the cylindrical holding material 1 shown in
This manufacturing method is a method for manufacturing a cylindrical holding material having a cross-section of a track shape (regarding the cross-sectional shape, refer to
This manufacturing method is a method for manufacturing the holding material 1C shown in
In the case that the higher basis weight part of the holding material 1C contacting the bottom G of the catalyst carrier 10C and the higher basis weight part contacting the top U thereof have different basis weight from each other, a dewatering molding tool 100A having the same interval between a bottom 101 and a top 102, and having a gradient angle (θ1) reaching one bottom 101 from the top 102 and a gradient angle (θ2) reaching the other bottom 101 from the top 102 that are different from each other as shown in
Alternatively, a dewatering molding tool 110B shown in
In the case that the holding material 1C is a cylindrical holding material, a flat plate-shaped dewatering molding tool shown in
The present invention is described in further detail below by reference to the following Examples and Comparative Examples, but it should be understood that the invention is not construed as being limited thereto. In Examples 1 and 2 and Comparative Example 1, holding materials for an elliptical catalyst carrier having a minor axis of 80 mm and a major axis of 120 mm were prepared, and in Example 3 and Comparative Example 2, holding materials for a columnar catalyst carrier having a diameter of 100 mm were prepared.
An aqueous slurry consisting of 100 parts by mass of alumina fibers (alumina: 96 mass %, silica: 4 mass %), 0.5 parts by mass of an acrylic resin as an organic binder, 3 parts by mass of colloidal silica as an inorganic binder, and 10,000 parts by mass of water was prepared. The aqueous slurry was poured into a dewatering molding tool having a uniform aperture ratio over the entire surface, and folded such that a top and a bottom appear at an equal interval as shown in
The holding material obtained was wound around a catalyst carrier such that a site corresponding to the top of the molded article coincides with an intersection point between an outer periphery of cross-section (ellipse) of the catalyst carrier and a minor axis of the ellipse as shown in
An aqueous slurry consisting of 100 parts by mass of alumina fibers (alumina: 80 mass %, silica: 20 mass %) as inorganic fibers, 0.5 parts by mass of an acrylic resin as an organic binder, 3 parts by mass of colloidal silica as an inorganic binder, and 10,000 parts by mass of water was prepared. The aqueous slurry was poured into a flat dewatering molding tool in which the aperture ratio is continuously changed from 50% to 75% as shown in
The holding material obtained was wound around a catalyst carrier such that a site corresponding to the top of the molded article coincides with an intersection point between an outer periphery of cross-section (ellipse) of the catalyst carrier and a minor axis of the ellipse as shown in
The same aqueous slurry as used in Example 1 was poured into a flat dewatering molding tool having a uniform aperture ratio over the entire surface, followed by dewatering molding, compression and drying, thereby obtaining a holding material having a thickness of 6.7 mm and a basis weight of 1,000 g/m2.
The holding material obtained was wound around a catalyst carrier, thereby obtaining a catalyst carrier unit. The catalyst carrier unit obtained was inserted with pressure in an elliptical cylindrical SUS casing having an outer minor axis of 91 mm, an outer major axis of 131 mm and a thickness of 1.5 mm (gap: 4.0 mm), thereby preparing a catalyst converter. After the insertion with pressure, the outer major axis remained unchanged, but the outer minor axis expanded 0.8 mm. From this fact, a gap at a major axis part was 4.4 mm. As a result, the holding material had density of 0.25 g/cm3 at a major axis part and a density of 0.227 g/cm3 at a minor axis part.
Regarding the catalyst converters obtained in Examples 1 and 2 and Comparative Example 1, holding force of the holding material was evaluated using a heating vibrator. The evaluation conditions are as follows. The results obtained are shown in Table 1.
Test temperature: 900° C.
Acceleration: 60G
It can be seen from the above results that the holding materials of Examples 1 and 2 according to the present invention can hold the carrier with a uniform force from the whole circumferential directions.
An aqueous slurry consisting of 100 parts by mass of alumina fibers (alumina: 96 mass %, silica: 4 mass %), 0.5 parts by mass of an acrylic resin as an organic binder, 3 parts by mass of colloidal silica as an inorganic binder, and 10,000 parts by mass of water was prepared. The aqueous slurry was poured into a dewatering molding tool having a uniform aperture ratio over the entire surface, and folded such that a top and a bottom appear at an equal interval as shown in
The holding material obtained was wound around a catalyst carrier such that the part having a higher basis weight coincides with the top and the bottom of the catalyst carrier as shown in
The same aqueous slurry as used in Example 3 was poured into a flat dewatering molding tool having a uniform aperture ratio over the entire surface, followed by dewatering molding, compression and drying, thereby obtaining a holding material having a thickness of 6.7 mm and a basis weight of 900 g/m2.
The holding material obtained was wound around a catalyst carrier, thereby obtaining a catalyst carrier unit. The catalyst carrier unit obtained was inserted with pressure in a cylindrical SUS casing having a diameter of 108 mm and a gap of 4.0 mm, thereby preparing a catalyst converter. As a result, the holding material had a density of 0.225 g/cm3 in all of sites thereof
Each of the catalyst converters obtained in Example 3 and Comparative Example 2 was attached to a heating vibrator, and was vibrated in a vertical direction to the openings of the catalyst carrier for 200 hours. Decreasing rate of carrier holding force before and after the test was measured using a load cell. The evaluation conditions are as follows, and the results obtained are shown in Table 2. Regarding Example 3, the converter was attached to the heating vibrator such that the top faces up and the bottom faces down.
Test temperature: 900° C.
Acceleration: 60G
While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the present invention.
This application is based on Japanese Patent Application No. 2010-026498 filed on Feb. 9, 2010, the contents of which are incorporated herein by way of reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-026498 | Feb 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/052651 | 2/8/2011 | WO | 00 | 8/9/2012 |
