JP2011208519A - Holding material for catalytic converter, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive holding material for a catalytic converter, which reduces unnecessary components of the holding material, while securing a holding capacity of a catalyst carrier.SOLUTION: The holding material used for the catalytic converter is provided with: the catalyst carrier; a metal casing which accommodates the catalyst carrier; and the holding material which is mounted on the catalyst carrier and interposed to a gap between the catalyst carrier and the metal casing. In the holding material for the catalytic converter, a basis weight of a portion where the weight of the catalyst carrier is applied most when the material is mounted on the catalyst carrier is the largest, and the basis weight decreases gradually with increasing distance from the portion.

Description

  The present invention relates to a catalyst carrier used for a catalytic converter for removing particulates, carbon monoxide, hydrocarbons, nitrogen oxides, etc. contained in exhaust gas discharged from an internal combustion engine such as a gasoline engine or a diesel engine. The present invention relates to a holding material for a catalytic converter for holding in a casing and a manufacturing method thereof.

  A holding material for a catalytic converter (hereinafter also referred to as “holding material”) is obtained by wet-forming an aqueous slurry containing inorganic fibers and an organic binder using a dehydrating mold having a predetermined shape, and hot pressing. Then, it is incorporated in a metal casing while mounted on the catalyst carrier (hereinafter also referred to as “canning”), and the organic binder contained in the holding material is burned down by the heat applied after the canning, and is compressed by the organic binder. The inorganic fibers constrained by the expansion in the thickness direction seals the gap between the catalyst carrier and the casing and holds the catalyst carrier.

  Further, as shown in FIG. 18, since the weight of the catalyst carrier 10 acts downward due to the influence of gravity, the force applied to the holding material 1 is usually maximum at the portion G directly below the catalyst carrier 10. For this reason, the basic weight of the catalyst carrier 10 is uniformly set as a whole with a value necessary to hold the portion G immediately below the catalyst carrier 10. Therefore, the basis weight is more than necessary at the other part of the holding material 1, particularly the part in contact with the upper part U where the weight of the catalyst carrier 10 is not added at all, and the holding material constituting material including inorganic fibers is more than necessary. It is used for.

  Note that there are a wide variety of holding materials, and many patent applications have been filed.

  The present invention has been made in view of such a situation, and an object thereof is to provide an inexpensive holding material for a catalytic converter by reducing unnecessary holding material constituent materials while ensuring the holding capacity of a catalyst carrier. And

In order to solve the above-mentioned problems, the present invention provides a holding material for a catalytic converter and a method for producing the same as described below.
(1) A holding material used in a catalytic converter comprising a catalyst carrier, a metal casing that houses the catalyst carrier, and a holding material that is attached to the catalyst carrier and interposed between the catalyst carrier and the metal casing. Because
A holding material for a catalytic converter, characterized in that the basis weight of the portion to which the weight of the catalyst carrier is most applied when mounted on the catalyst carrier is maximum, and the basis weight gradually decreases as the catalyst carrier is separated from the portion.
(2) A step of pouring an aqueous slurry containing inorganic fibers into a dehydrating mold that gradually becomes shallow starting from the deepest region, a step of dehydrating the aqueous slurry to obtain a wet molded body, and a thickness of the entire wet molded body A method for producing a holding material for a catalytic converter, comprising a step of drying while compressing in a direction.
(3) A step of pouring an aqueous slurry containing inorganic fibers into a dehydrating mold whose opening ratio gradually decreases starting from a region having the largest opening ratio, a step of dehydrating the aqueous slurry to obtain a wet molded body, And a step of drying the entire molded body while compressing the entire molded body in the thickness direction.

  The holding material of the present invention has the largest basis weight in the portion immediately below the catalyst carrier to which the weight of the catalyst carrier is most applied, and gradually decreases toward the upper side and becomes the minimum in the portion immediately above the catalyst carrier. While securing, the holding material constituting material can be reduced and the cost becomes low.

It is a figure which shows the holding | maintenance material for catalyst carriers with a circular cross section which concerns on this invention along the cross-sectional shape of a catalyst carrier. It is a figure which shows the holding | maintenance material for catalyst carriers of an elliptical cross section which concerns on this invention along the cross-sectional shape of a catalyst carrier. It is a figure which shows the holding | maintenance material for catalyst carriers of the cross-section track type which concerns on this invention along the cross-sectional shape of a catalyst carrier. It is a perspective view which shows a mat type | mold holding material. It is a perspective view which shows a cylindrical holding | maintenance material. It is a schematic diagram which shows the dehydration mold used for the 1st manufacturing method of this invention. (A) is sectional drawing which shows the wet molded object obtained by the 1st manufacturing method, (B) is sectional drawing which shows the sheet | seat obtained after compression and drying, (C) cut | disconnects a sheet | seat It is sectional drawing which shows the mat-shaped holding material obtained. It is a schematic diagram which shows the dehydration mold used for the 2nd manufacturing method of this invention. (A) is sectional drawing which shows the wet molded object obtained by the 2nd manufacturing method, (B) is sectional drawing which shows the sheet | seat obtained after compression and drying, (C) cut | disconnects a sheet | seat It is sectional drawing which shows the mat-shaped holding material obtained. It is a perspective view which shows the dehydration mold used for the 3rd manufacturing method of this invention. (A) is sectional drawing which shows the wet molded object obtained by the 3rd manufacturing method, (B) is sectional drawing which shows the sheet | seat obtained after compression and drying, (C) cut | disconnects a sheet | seat It is sectional drawing which shows the mat-shaped holding material obtained. It is a perspective view which shows the dehydration mold used for the 4th manufacturing method of this invention. (A) is sectional drawing which shows the wet molded object obtained by the 4th manufacturing method, (B) is sectional drawing which shows the sheet | seat obtained after compression and drying, (C) cut | disconnects a sheet | seat It is sectional drawing which shows the mat-shaped holding material obtained. It is a perspective view which shows the dehydration mold used for the 5th manufacturing method of this invention. It is a schematic diagram for demonstrating the 5th manufacturing method. It is a schematic diagram which shows the cylindrical wet molded object obtained by the method shown in FIG. It is a perspective view which shows the dehydration mold used for the 6th manufacturing method of this invention. It is a figure which shows the holding material for conventional catalyst converters along the cross-sectional shape of a catalyst carrier.

  Hereinafter, the present invention will be described in detail.

(Holding material)
As shown in a cross-sectional view in FIG. 1, the holding material 1 has a portion in contact with a portion G immediately below the catalyst carrier 1 to which the weight of the catalyst carrier 10 is most applied. The grammage is the largest along the portion U), and the grammage gradually decreases toward the portion in contact with the directly upper portion U, and the grammage along the thickness direction (portion indicated by reference numeral 12) at the directly upper portion U. The amount is set to be the smallest (hereinafter also referred to as “basis weight minimum portion”).

Here, the basis weight means the fiber mass per unit area. In the holding material of the present invention, the range is not particularly limited as long as the effect of the invention can be exhibited, and may be 450 to 4500 g / m ² . More specifically, the range varies depending on the size of the gap between the catalyst carrier 10 and the casing 20 (hereinafter also referred to as “gap”). For example, when the gap is 2 to 6 mm, 450 to 1800 g / m ^2. In the case of 6 to 10 mm, it may be 1800 to 3600 g / m ² , and in the case of 8 to 12 mm, it may be 2250 to 4500 g / m ² . The casing 20 is similar to the catalyst carrier 10 and has a circular cross section here.

  The ratio of the basis weight of the basis weight maximum portion and the basis weight of the basis weight minimum portion is not particularly limited as long as the effect of the present invention can be obtained, but may be 1.05 to 2.0 times. It is preferably 1.1 to 1.8 times, and more preferably 1.1 to 1.6 times. The variation in the gap difference between the casing 20 and the catalyst carrier 10 depends on the dimensional accuracy, residual stress, heating temperature, and the like of the casing 20, but is generally 1.5 times or less. Therefore, by setting the basis weight ratio as described above, even if there is such a gap difference, it becomes possible to uniformly seal the entire circumference of the catalyst carrier 10.

  The holding material 1 preferably has a constant thickness in consideration of holding power, heat insulating performance, sealing performance, and the like. Specifically, the thickness may be 5 to 30 mm, and preferably 6 to 12 mm. The thickness variation is preferably ± 15% or less, more preferably ± 10% or less, and further preferably ± 5% or less.

  Although the casing 20 is divided into upper and lower parts in the illustrated example, the holding member 1 can be canned by a stuffing method using an integral casing, and the thickness of the holding member 1 can be made constant. It can be expected to improve productivity.

  A low friction sheet 30 having a friction coefficient of 0.1 to 0.3 may be laminated on the entire outer periphery of the holding material 1. Thereby, the frictional resistance when canning the integrated casing is reduced, and the canning operation is facilitated.

  In addition, the catalyst carrier 10 may have a flat cross-sectional shape such as an ellipse or a track shape in addition to a circular cross-section as illustrated.

  FIG. 2 is a cross-sectional view showing the holding material 1A that holds the catalyst carrier 10A having an elliptical cross section. However, the weight of the catalyst carrier 10A is maximized at a lower point G where the ellipse and the minor axis H intersect. The portion along the thickness 11 is the maximum basis weight portion, and the portion in contact with the upper point U where the ellipse of the catalyst carrier 10A intersects the short diameter H is the minimum basis weight portion along the thickness 12. Become. Further, the basis weight gradually decreases from the basis weight maximum portion to the basis weight minimum portion. In addition, the code | symbol 20A in a figure is a casing.

  When the low friction sheet 30 is laminated, it may be the entire outer periphery of the holding material 1A, but it is provided only on the outer peripheral surface of the portion in contact with the points D and D where the ellipse and the major axis L of the catalyst carrier 10A intersect. May be. When the holding material 1A is mounted on the catalyst carrier 10A, the radius of curvature is small in the vicinity of the portion in contact with the points D and D, so this portion is pulled to the outside (casing side) and is placed on the outer surface of the holding material 1A. It is possible to avoid problems that cause cracks and wrinkles. Such cracks and wrinkles on the outer surface of the holding material 1 are undesirable because they hinder canning.

  FIG. 3 is a cross-sectional view showing the holding material 1B for holding the catalyst carrier 10B having a track-shaped cross section. The weight of the catalyst carrier 10B is uniformly maximized over the entire portion 40 in contact with the lower plane portion 10a. Therefore, this portion 40 is set as the basis weight maximum portion. Moreover, the part 41 which contact | connects the upper plane part 10b becomes a basic weight minimum part. Further, in the portion 50 in contact with the curved portion 10c of the catalyst carrier 10B, the basis weight gradually decreases from the end portions E and E of the portion 40 toward the end portions F and F of the portion 41. In addition, the code | symbol 20B in a figure is a casing, and you may laminate | stack a low friction sheet | seat (not shown) on the outer peripheral surface of the part 50. FIG.

  In addition, although not shown, the catalyst carrier may have a flat cross-sectional shape obtained by crushing a catalyst carrier circle from two orthogonal diameter sides, or a cross-sectional shape in which the curvature of an ellipse is different in each part.

  In the above, there is no restriction | limiting in the constituent material of holding | maintenance material 1, 1A, 1B, What is necessary is just to contain an inorganic fiber and an organic binder. Moreover, there is no restriction | limiting in these types which may contain the filler, inorganic binder, etc. which are used conventionally as needed, A preferable example is shown below.

As the inorganic fiber, various inorganic fibers conventionally used for holding materials can be used. For example, alumina fibers, mullite fibers, or other ceramic fibers can be used as appropriate. More specifically, as the alumina fiber, for example, Al ₂ O ₃ is preferably 90% by weight or more (the rest is SiO ₂ minutes), and preferably has a low crystallinity based on X-ray crystallography, The crystallinity may be 30% or less, preferably 15% or less, and more preferably 10% or less. Further, the average fiber diameter is preferably 3 to 8 μm and the wet volume is 400 cc / 5 g or more. As the mullite fiber, for example, it is preferable that the mullite composition has an Al ₂ O ₃ minute / SiO ₂ minute weight ratio of about 70/30 to 80/20 and has a low crystallinity based on X-ray crystallography. The crystallinity may be 30% or less, preferably 15% or less, and more preferably 10% or less. Further, the average fiber diameter is preferably 3 to 8 μm and the wet volume is 400 cc / 5 g or more. Examples of other ceramic fibers include silica-alumina fibers and silica fibers, but any of them may be those conventionally used for holding materials. Moreover, you may mix | blend glass fiber, rock wool, and a biosoluble fiber.

The wet volume is calculated by the following method.
1) Weigh 5 g of dried fiber material with a scale having an accuracy of two decimal places or more.
2) Place the weighed fiber material into a 500 g glass beaker.
3) About 400 cc of distilled water having a temperature of 20 to 25 ° C. is placed in the glass beaker of 2), and carefully stirred and dispersed using a stirrer so as not to cut the fiber material. An ultrasonic cleaner may be used for this dispersion.
4) Transfer the contents of the glass beaker of 3) to a 1000 ml graduated cylinder and add distilled water to a scale of 1000 cc.
5) Close the mouth of the graduated cylinder of 4) with your hands, and stir it upside down, taking care not to leak water. This is repeated a total of 10 times.
6) After the stirring is stopped, the mixture is allowed to stand at room temperature, and the fiber sedimentation volume after 30 minutes is visually measured.
7) The above operation is performed on three samples, and the average value is taken as the measured value.

  The organic binder may be a known one, and rubbers, water-soluble organic polymer compounds, thermoplastic resins, thermosetting resins, and the like can be used. Specifically, examples of 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 compound include carboxymethyl cellulose and polyvinyl alcohol. Examples of thermoplastic resins include homopolymers and copolymers such as acrylic acid, acrylic ester, acrylamide, acrylonitrile, methacrylic acid, methacrylic ester, acrylonitrile / styrene copolymer, acrylonitrile / butadiene / styrene copolymer Etc. Examples of the thermosetting resin include a bisphenol type epoxy resin and a novolac type epoxy resin. In addition, these organic binders can also be used in combination of 2 or more types. Although there will be no restriction | limiting if the usage-amount of an organic binder is the quantity which can bind inorganic fiber, What is necessary is just 0.1-10 mass parts with respect to 100 mass parts of inorganic fibers. When the organic binder is less than 0.1 parts by mass, the binding force is insufficient, and when it exceeds 10 parts by mass, the amount of inorganic fibers is relatively reduced, and the holding performance and sealing performance required as a holding material may not be obtained. Concerned. The preferable amount of the organic binder is 0.2 to 6 parts by mass, and the more preferable amount is 0.2 to 4 parts by mass.

  Moreover, it is also possible to mix | blend a small amount of organic fibers, such as a pulp, as an organic binder. The thinner and longer the organic fiber, the higher the binding force, and highly fibrillated cellulose and cellulose nanofiber are preferred. Specifically, the fiber diameter is preferably 0.01 to 50 μm, the fiber length is preferably 1 to 5000 μm, the fiber diameter is preferably 0.02 to 1 μm, and the fiber length is more preferably 10 to 1000 μm.

  The amount of such fibrillated fibers used is not limited as long as it is an amount capable of binding inorganic fibers, but is 0.1 to 5 parts by mass with respect to 100 parts by mass of inorganic fibers. If the fibrillated fiber is less than 0.1 parts by mass, the binding force is insufficient, and if it exceeds 5 parts by mass, the amount of inorganic fibers is relatively reduced, and the holding performance and sealing performance required as a holding material cannot be obtained. The preferable amount of the fibrillated fiber is 0.1 to 2.5 parts by mass, and the more preferable amount is 0.1 to 1 part by mass.

  Moreover, you may use together such a fibrillated fiber and an inorganic binder. According to the combined use of the fibrillated fiber and the inorganic binder, the inorganic fiber can be used even when the amount of the fibrillated fiber is reduced in order to avoid the above-mentioned problem caused by the volatilization of the organic component in use. Can be satisfactorily bound, and a catalytic converter holding material capable of maintaining the same thickness as the conventional one can be provided. Such inorganic binders may be known ones, and include glass frit, colloidal silica, alumina sol, sodium silicate, titania sol, lithium silicate, montmorillonite clay minerals, water glass and the like. In addition, these inorganic binders can also be used in combination of 2 or more types. Although there will be no restriction | limiting if the usage-amount of an inorganic binder is an quantity which can bind an inorganic fiber, It is 0.1-10 mass parts with respect to 100 mass parts of inorganic fibers. If the inorganic binder is less than 0.1 parts by mass, the binding force is insufficient, and if it exceeds 5 parts by mass, the amount of inorganic fibers is relatively reduced, and the holding performance and sealing performance required as a holding material cannot be obtained. A preferable amount of the inorganic binder is 0.2 to 6 parts by mass, and a more preferable amount is 0.2 to 4 parts by mass.

  In addition, it is preferable that the organic content to contain is 0.3-4.0 mass% with respect to the holding | maintenance material whole quantity, It is more preferable that it is 0.5-3.0 mass%, 1.0-2 It is particularly preferable that the content be 5% by mass. The smaller the organic content, the more preferable the volatile gas is reduced when heat is applied after canning. Here, the organic component can be substituted by the ignition loss rate after heating at 700 ° C. for 30 minutes.

  The holding materials 1, 1 </ b> A, and 1 </ b> B are not particularly limited in form, and may be a single mat shape (mat-type holding material), and a cylindrical shape having a circular, elliptical, or track-shaped cross section ( It may be a cylindrical holding material). FIG. 4 shows the mat-type holding material 1. A concave portion is formed at one end portion, a convex portion is formed at the other end portion, and the concave portion and the convex portion are joined so as to engage with each other. In addition, the junction part of a convex part and a recessed part becomes a basic weight minimum part. FIG. 5 shows a cylindrical holding member having a circular cross section shown in FIG. Since the mat type holding material needs to be wound around the catalyst carrier, the cylindrical holding material is more advantageous in consideration of labor and cost.

  Below, the manufacturing method of said holding | maintenance material is demonstrated.

(First manufacturing method)
In manufacturing the holding member 1 having the circular cross section and the holding member 1A having the elliptical cross section, the bottom 101 (the deepest region) and the top 102 (the shallowest region) appear at equal intervals as shown in FIG. An aqueous slurry containing the holding material constituent material is poured from above in the drawing using the dehydrating mold 100 folded in the figure, and the holding material constituting material is attached to the entire surface of the dehydrating mold 100 by dehydration molding. Here, a region gradually becoming shallower from the bottom 101 toward the top 102 is formed. Further, the opening ratio of the dehydrating mold 100 is uniform over the entire surface.

  The dehydration mold 100 includes a frame that surrounds the whole, but the frame is omitted here. The same applies to the subsequent manufacturing methods. Further, the dehydration mold 100 only needs to be able to transmit moisture in the aqueous slurry and leave the constituent material of the holding material such as inorganic fibers on the mold surface. For example, a metal net, a flat plate in which many fine holes are formed, or the like Can be used. Here, a wire mesh will be described as an example.

  Next, when the dehydrating mold 100 is removed, as shown in FIG. 7A, the top T corresponding to the bottom 101 of the dehydrating mold 100 and the bottom B corresponding to the top 102 of the dehydrating mold 100 are alternately arranged. A wet molded body 200 having a continuously appearing cross-sectional shape is obtained.

  Next, the wet molded body 200 is pressed from above in the drawing so as to have the same thickness, and dried at, for example, 100 to 200 ° C., so that the basis weight of the portion corresponding to the top portion T as shown in FIG. Is obtained, and a long sheet 210 having a grammage gradually decreasing toward the bottom B at both ends is obtained.

  Next, as shown in FIG. 7C, the holding member 1 is obtained by cutting the sheet 210 along “bottom B-top T-bottom B” as one unit and along the bottom B at both ends. The holding material 1 has a flat mat shape, and both ends are processed into an uneven shape as shown in FIG.

  In this manufacturing method, the dehydration mold 100 may have a waveform in a side view as well as a shape in which the bottom 101 and the top 102 are bent as shown in FIG.

(Second manufacturing method)
Similar holding materials 1 and 1A are obtained also by this manufacturing method. That is, as shown in FIG. 8, a flat dehydration mold 110 alternately connected to the first region 111 in which the aperture ratio gradually decreases and the second region 112 in which the aperture ratio gradually increases is used. In the first region 111 of the dehydrating mold 110, the aperture ratio gradually decreases with the starting point (point A) as the maximum, and in the second region 112 connected to the first region 111, the aperture ratio is the same as that of the first region 111. The connecting part (X point) is the smallest and gradually increases. The dehydrating mold 110 repeats such an increase / decrease pattern of the aperture ratio. Then, an aqueous slurry containing the holding material constituting material is poured into the dehydrating mold 110, and the holding material constituting material is adhered to the entire surface of the dehydrating mold 110 by dehydrating molding. Here, the dehydration mold 100 is preferably flat (the depth is uniform over the entire surface), but the depth can be partially changed.

  Next, when the dehydration mold 110 is removed, as shown in FIG. 9A, a wet molded body 200 having a cross-sectional shape in which the top portions T and the bottom portions B appear alternately and continuously is obtained. The larger the aperture ratio, the more water is sucked and the inorganic fibers are sucked along with it, so that the amount of attached fibers is the largest at point A and the amount of attached fibers is the smallest at point X. The cross-sectional shape is as shown in (A).

  Next, in the same manner as in the first manufacturing method, the wet molded body 200 is pressed from above in the drawing to have the same thickness, and dried to correspond to the top T as shown in FIG. 9B. A long sheet 210 having the largest basis weight of the portion and gradually decreasing toward the bottom B at both ends is obtained.

  Next, as shown in FIG. 9C, the holding member 1 is obtained by cutting the sheet 210 along “bottom B-top T-bottom B” as one unit and along the bottom B at both ends. The holding material 1 has a flat mat shape, and both ends are processed into an uneven shape as shown in FIG.

(Third production method)
In order to manufacture the holding member 1B having a track-shaped cross section as shown in FIG. 3, as shown in FIG. 10, the aperture ratio is uniform over the entire surface, and the flat bottom region 121 is gradually increased from both ends of the bottom region 121. The dehydration mold 120 in which the inclined region 122 inclined upward and the flat top region 123 continuous to the highest position of the inclined region 122 is formed is used. The width of the bottom region 121 corresponds to the distance between EEs, the width of the inclined region 122 corresponds to the arc length of the curved portion 50 (distance between EFs), and the width of the top region 123 corresponds to the distance between FFs. Then, an aqueous slurry containing the holding material constituting material is poured from above in the figure, and the holding material constituting material is adhered to the entire surface of the dehydrating mold 120 by dehydration molding.

  Next, when the dehydrating mold 120 is removed, as shown in FIG. 11 (A), the (T1-T2) portion corresponding to the bottom region 121 is thick and the both ends thereof are thick corresponding to the inclined regions 122 as shown in FIG. The wet molded body 300 in which the (B-T1) portion and the (T2-B) portion with gradually decreasing lengths are continuous and the thinnest (BB) portion is formed corresponding to the top region 123 is obtained.

  Next, the wet molded body 300 is pressed from above in the figure to have the same thickness, and dried to obtain a sheet 310 having a basis weight changed according to the thickness. That is, as shown in FIG. 11B, the sheet 310 has the largest basis weight in the portion corresponding to the (T1-T2) portion of the wet molded body 300, and the (B-T1) portion and the (T2-B) portion. ) The basis weight gradually decreases in the portion corresponding to the portion, and the basis weight is the smallest in the portion corresponding to the (BB) portion.

  Next, as shown in FIG. 11C, the holding material 1B is obtained by cutting at a position that is half the width of the (BB) portion. Moreover, both ends are processed into a concavo-convex shape as shown in FIG.

(Fourth manufacturing method)
A similar holding material 1B is also obtained by this manufacturing method. That is, as shown in FIG. 12, the first area 131 having the largest and uniform aperture ratio, the second area 132 that gradually decreases as the aperture ratio moves away from the first area, and the second area 132 continuously. A flat dehydrating mold 130 in which a third region 133 having a minimum aperture ratio and a uniform area is formed. Then, an aqueous slurry containing the holding material constituting material is poured from above the dehydrating mold 130, and the holding material constituting material is adhered to the entire surface of the dehydrating mold 130 by dehydration molding.

  Next, when the dehydrating mold 120 is removed, as shown in FIG. 13 (A), the (T1-T2) portion corresponding to the bottom region 131 is thick in the cross-sectional shape, and thick at both ends corresponding to the inclined region 132. The wet molded body 400 is obtained in which the (B-T1) portion and the (T2-B) portion where the thickness gradually decreases and the thinnest (BB) portion corresponding to the top region 133 is formed.

  Next, the wet molded body 400 is pressed from above in the drawing to have the same thickness, and dried to obtain a sheet 410 having a basis weight changed according to the thickness. That is, as shown in FIG. 13B, the sheet 410 has the largest basis weight in the portion corresponding to the (T1-T2) portion of the wet molded body 400, and the (B-T1) portion and the (T2-B) portion. ) The basis weight gradually decreases in the portion corresponding to the portion, and the basis weight is the smallest in the portion corresponding to the (BB) portion.

  Next, as shown in FIG. 13C, the holding material 1B is obtained by cutting at a position that is half the width of the (BB) portion. Moreover, both ends are processed into a concavo-convex shape as shown in FIG.

(Fifth manufacturing method)
This manufacturing method is a method for manufacturing the cylindrical holding member 1 shown in FIG. FIG. 14 shows the dewatering mold 110A used, but the first region 111 and the second region 112 of the flat plate dewatering mold 110 shown in FIG. 8 are cut out, and the A points on both ends are connected to form a cylindrical shape. Is formed. Therefore, the aperture ratio becomes the minimum at the point B as the connecting portion. Then, as shown in FIG. 15, the cylindrical dewatering mold 110A is immersed in the aqueous slurry 106 stored in the slurry reservoir 105 and sucked by the suction pump 107 from the inside of the cylindrical dewatering mold 110A. Thereby, as shown in FIG. 16, the inorganic fiber 108 adheres to the surface of the cylindrical dewatering mold 110A, and the cylindrical wet molded body 401 is obtained. Next, after removing the mold, the cylindrical shape is held, compressed to the same thickness, and dried to obtain a cylindrical holding material having a circular cross section.

(Sixth manufacturing method)
This manufacturing method is a method for manufacturing a cylindrical holding member having a cross-sectional track shape (see FIG. 3 for a cross-sectional shape). FIG. 17 shows a dehydrating mold 130A to be used, but “third area 133−second area 132−first area 131−second area 132−third area” of the flat plate dehydrating mold 130 shown in FIG. 133 "is cut out and connected at a position half the width of the third regions 133 and 133 at both ends. Then, in the same manner as in the fifth production method, it is immersed in an aqueous slurry stored in a slurry reservoir, and sucked with a suction pump from the inside to obtain a cylindrical wet molded body. Next, after removing the mold, the cylindrical shape is held, compressed to the same thickness, and dried to obtain a cylindrical holding material having a cross-sectional track shape.

  Examples The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereby. In either case, a holding material for a catalyst carrier having a circular cross section with a diameter of 100 mm was produced.

Example 1
An aqueous slurry of 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 10000 parts by mass of water is produced with respect to 100 parts by mass of alumina fibers (alumina 96 mass%, silica 4 mass%). did. Next, as shown in FIG. 6, using a dehydrating mold folded so that the opening ratio is uniform over the entire surface and the top and bottom portions appear at equal intervals, an aqueous slurry is poured, and dehydration molding is performed to form a wet molded body. Obtained. The maximum difference between the top and bottom was 10 mm. Then, the entire wet molded body is dried at 100 ° C. while being compressed so as to have the same thickness in the thickness direction, and has a width of 40 mm as shown in FIG. A sheet with the largest amount and a gradually decreasing basis weight toward both sides was obtained. And as shown in FIG.7 (C), it cut | disconnected along two top parts which pinch | interpose a bottom part, and obtained the mat-shaped holding material. The thickness of the obtained holding material was almost constant and averaged 6.7 mm, which was ± 0.5 mm or less. The basis weight of the portion corresponding to the bottom portion was 1100 g / cm ² , the basis weight of the portion corresponding to the bottom portion was 1000 g / cm ² , and the basis weight ratio was 1.1 times. In addition, 96.6% by mass of inorganic fiber, 0.5% by mass of organic binder, and 2.9% by mass of inorganic binder are contained with respect to the total amount of the holding material. It was 5% by mass.

  As shown in FIG. 1, the obtained holding material was wound around the catalyst carrier so that the portion corresponding to the bottom coincided with the portion directly above the catalyst carrier to obtain a catalyst carrier unit. This catalyst carrier unit was press-fitted into an SUS casing having an outer diameter of 111 mm and a wall thickness of 1.5 mm (gap 4.0 mm) to form a catalytic converter.

(Example 2)
For 100 parts by mass of alumina fibers as inorganic fibers (80% by mass of alumina and 20% by mass of silica), 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 An aqueous slurry was made. Next, using a flat dehydrating mold whose opening ratio continuously changed from 50% to 75% as shown in FIG. 8, an aqueous slurry was poured and dehydrated to obtain a wet molded body. Then, the entire wet molded body is dried at 100 ° C. while being compressed so as to have the same thickness in the thickness direction, and has a width of 40 mm as shown in FIG. The largest sheet was obtained with the grammage gradually decreasing toward both sides. And as shown in FIG.9 (C), it cut | disconnected along two bottom parts which pinch | interpose a top part, and obtained the mat-shaped holding material. The thickness of the obtained holding material was almost constant and averaged 6.7 mm, which was ± 0.5 mm or less. The basis weight of the portion corresponding to the top portion was 1100 g / cm ² , the basis weight of the portion corresponding to the bottom portion was 1000 g / cm ² , and the basis weight ratio was 1.1 times. In addition, 96.6% by mass of inorganic fiber, 0.5% by mass of organic binder, and 2.9% by mass of inorganic binder are contained with respect to the total amount of the holding material. It was 5% by mass.

  As shown in FIG. 1, the obtained holding material was wound around the catalyst carrier so that the portion corresponding to the bottom coincided with the portion directly above the catalyst carrier to obtain a catalyst carrier unit. The catalyst carrier unit was press-fitted into an elliptical cylindrical SUS casing having an outer diameter of 111 mm and a wall thickness of 1.5 mm (gap 4.0 mm) to prepare a catalytic converter.

(Comparative Example 1)
The same aqueous slurry as in Example 1 was poured into a flat dewatering mold, dewatered, compressed and dried to obtain a uniform holding material having a thickness of 6.7 mm and a basis weight of 1000 g / m ² .

  The obtained holding material was wound around a catalyst carrier to obtain a catalyst carrier unit. Then, a catalytic converter was manufactured by press-fitting into an elliptical cylindrical SUS casing having an outer minor axis of 91 mm, an outer major axis of 131 mm, and a wall thickness of 1.5 mm (gap 4.0 mm).

(Retention force evaluation)
About the catalytic converters of Examples 1 and 2 and Comparative Example 1, in Examples 1 and 2, the catalytic converter was placed in a state where the catalytic converter was placed so that the portion with the largest basis weight of the holding material was positioned directly below. The holding power of the holding material was evaluated. In Comparative Example 1, since the basis weight is uniform throughout the holding material, the catalytic converter was mounted on the heating shaker without considering the arrangement. The evaluation conditions are as follows, and the results are shown in Table 1.
Test temperature: 900 ° C
・ Acceleration: 60G

  From the above results, it can be seen that the holding materials of Examples 1 and 2 according to the present invention can hold the carrier with a uniform force from the entire circumferential direction.

1, 1A, 1B Holding material 10, 10A, 10B Catalyst carrier 20 Casing 30 Low friction sheet 100, 110, 120, 130 Flat plate dewatering mold 110A, 130A Cylindrical dewatering mold 200, 300 Wet molded body

Claims (3)

A holding material used in a catalytic converter, comprising a catalyst carrier, a metal casing that houses the catalyst carrier, and a holding material that is attached to the catalyst carrier and interposed in the gap between the catalyst carrier and the metal casing. ,
A holding material for a catalytic converter, characterized in that the basis weight of the portion to which the weight of the catalyst carrier is most applied when mounted on the catalyst carrier is maximum, and the basis weight gradually decreases as the catalyst carrier is separated from the portion.   A process of pouring an aqueous slurry containing inorganic fibers into a dewatering mold that gradually becomes shallow starting from the deepest region, a process of dehydrating the aqueous slurry to obtain a wet molded body, and compressing the entire wet molded body in the thickness direction And a step of drying while providing a method for producing a holding material for a catalytic converter.   A step of pouring an aqueous slurry containing inorganic fibers into a dewatering mold in which the opening ratio gradually decreases starting from the region having the largest opening ratio, a step of dehydrating the aqueous slurry to obtain a wet molded body, and the entire wet molded body And a step of drying while compressing in the thickness direction. A method for producing a holding material for a catalytic converter.

Images