JPS6346035B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a ceramic three-dimensional network structure, which is made of a ceramic material that is attracting attention as a catalyst carrier or various filter materials, and has a three-dimensional network cell structure with internal communication spaces, and a method for manufacturing the same. In particular, the present invention provides a three-dimensional network structure made of cordierite used as a catalyst carrier for automobile exhaust gas treatment, and a method for producing the same, which has particularly excellent thermal shock resistance,
The present invention also relates to a three-dimensional network structure made of cordierite that has high strength and low pressure loss, and a method for producing the same. Three-dimensional network structures made of cordierite are most suitable as catalyst carriers for automobile exhaust gas treatment, especially as filter materials for collecting particulate matter in diesel engines, and have been attracting attention in recent years. When used as such a carrier or filter material in an automobile, the following properties are particularly important. The first property is excellent thermal shock resistance, the second property is high mechanical strength, and the third property is low pressure loss. Conventionally, honeycomb filters have been proposed in addition to ceramic three-dimensional network structure filters to achieve this type of purpose and characteristics, but one of the present inventors has proposed a ceramic filter that is inferior to honeycomb filters. A method for improving the mechanical strength of a three-dimensional network structure filter has been developed and proposed, and a strength sufficient to withstand use for this type of purpose has been achieved.In addition, the present invention provides a method for reducing the strength. It is an object of the present invention to provide a three-dimensional ceramic network structure, in particular a three-dimensional network structure made of cordierite, which can realize lower pressure loss and improved thermal shock resistance, and a method for manufacturing the same. Thus, the structure of the present invention is characterized in that all the skeletons on the core and the external surface are continuous, and the thickness of the skeleton becomes thicker as it goes outward toward the surface. Furthermore, the method for producing a ceramic three-dimensional network structure of the present invention involves spraying and adhering ceramic slurry to the three-dimensional network skeleton appearing on the external surface of an organic porous body having a three-dimensional network cell structure. After that, the structure is immersed in ceramic slurry, the excess slurry is removed, and the process of drying is repeated to form a three-dimensional network structure appearing on the external surface of the structure thus obtained. It is characterized by spraying ceramic slurry onto the skeleton, adhering it to the skeleton, and then sintering it. Ceramic slurries used in the method of this invention include cordierite slurry, alumina slurry, mullite slurry, and aluminum titanate slurry. Among these, cordierite slurry is most often used. To prepare this cordierite slurry, a composition consisting of aluminum hydroxide, talc, and clay is mixed and kneaded, and then dried raw material powder and this raw material powder are mixed. Fired and crushed cordierite powder whose crystalline system is all cordierite is mixed in an appropriate ratio, and the above mixture is dispersed in water in which an organic binder such as polyvinyl alcohol and a surfactant have been dissolved in advance. This is done by letting Ceramic slurry such as cordierite slurry prepared as described above is atomized and adhered to the outer surface skeleton of an organic porous body such as a urethane foam having a three-dimensional network structure. After that, the organic porous material is immersed in this slurry, the slurry is adhered to the surface of the organic porous material, the excess slurry is removed, and the series of steps of further drying is repeated, resulting in the core 1 shown in the figure. can get. Next, this core 1
This slurry is sprayed and applied to the outer surface of the machine.
When the cordierite slurry adhered to the organic porous body is then dried and sintered in this manner, the organic porous body disappears and a three-dimensional network structure made of cordierite is obtained. In the method of this invention, if the slurry is coated so that the bulk density of the core 1 is in the range of 0.25 g/cm ³ to 0.45 g/cm ³ , a structure with low pressure loss and high strength can be obtained. . Note that the amount to be sprayed and attached to the external surface of the organic porous body at first is preferably 0.05 to 0.30 g/cm ² . Next, by repeating the series of steps of immersion in slurry, removal of excess slurry, and drying several times, a core 1 having the desired weight shown in the figure is obtained. In addition, when it is first applied in the form of a spray to the external surface of the organic porous body, it may be applied in the form of a spray only to the side surface 2 of the external surface that is not involved in ventilation. Next, a slurry is applied to the side surface 2 of the outer surface of the core 1 that does not participate in ventilation, but the amount thereof is preferably less than 0.3 g/cm ² . Although the slurry does not necessarily have to be applied to the side surface 2 in the form of a spray, it is more effective in terms of thermal shock resistance if it is applied in the form of a spray. Furthermore, among the external surfaces, a slurry is sprayed to adhere to the end face 3 of the core 1 which is involved in ventilation, and the amount of the slurry applied is 0.04 g/cm ² to 0.1
It is suitable that it is in the range of g/cm ² . Note that the arrow in the figure indicates the direction of ventilation. As described in detail above, according to the present invention, a predetermined amount of ceramic slurry such as cordierite slurry is applied in advance to the external surface of a structure in the form of a spray, and then immersed in this slurry.
While repeating the steps of removing excess slurry and drying, a structure can be obtained in which the skeleton of the three-dimensional network structure becomes thicker as it goes outward toward the external surface. Therefore, it is possible to create a structure in which the core 1 shown in the figure and all the skeletons on the external surface are continuous, and the thickness of the skeleton becomes thicker toward the outside without sacrificing the strength of the conventional product. , a ceramic three-dimensional network structure having lower pressure loss and excellent thermal shock resistance can be obtained. In addition, in this invention, when the side surface 2 that does not participate in ventilation is finally formed by spraying the slurry in advance and attaching it to the external surface of the organic porous material, the joint portion between the core 1 and the side surface 2 is strengthened. It is possible to reduce the weight of the substantial parts involved in ventilation without reducing strength, and as a result, it is possible to create a three-dimensional ceramic network structure with low pressure loss and improved thermal shock resistance. . Note that one of the features of the structure of the present invention is that the side surface 2 is a continuous surface and has a structure that prevents gas from escaping. Example 1 17% by weight of aluminum hydroxide, 37% by weight of talc, and 46% by weight of clay were mixed, kneaded, and dried, and 10 parts by weight of the raw material powder was added.
After firing at a temperature of 1410℃ for 5 hours, the average particle size
Mix 90 parts by weight of cordierite powder whose crystalline system is all cordierite, crushed to a size of 10 microns, and thoroughly disperse the above mixture in water in which polyvinyl alcohol as an organic binder and a surfactant have been dissolved in advance. A cordierite slurry was prepared. This slurry is sprayed onto the side 2, which does not participate in ventilation, of the external surface of the three-dimensional mesh urethane foam (nominal mesh number used is #13) as an organic porous body, at a rate of 0.09 to 0.09 per unit area (cm ² ). 0.11g was deposited. Further, urethane foam was immersed in this slurry to adhere the slurry to the entire skeleton surface, and then the excess slurry was removed using centrifugal force and then dried. The steps of immersion in the slurry, removal, and drying were repeated 4 to 6 times to obtain the core 1 shown in the figure with a bulk density of 0.29 to 0.34 g/cm ³ (calculated from the weight and geometric volume after the final firing step). Ta. Next, 0.1 to 0.13 g of slurry is applied per unit area (cm ² ) of the side surface 2 to the side surface 2 of the external surface of the core 1 that is not involved in ventilation by partial immersion, and then 0.025 to 0.025 g is applied in the form of a spray. 0.05g of slurry was deposited. Next, on the end surface 3 of the outer surface of the core 1, which is involved in ventilation, per unit area (cm ² )
0.045 to 0.060 g of the slurry was sprayed and adhered to the end face skeleton without clogging, and after drying,
When sintered for 5 hours at a temperature of °C, the urethane foam is burnt out and the overall bulk density is 0.40g/ ^cm3.
A three-dimensional network structure made of cordierite was obtained. Regarding the above ceramic three-dimensional network structure,
We prototyped a ceramic three-dimensional network structure filter with a diameter of 93 mm and a height of 66 mm.
The properties of pressure drop, isostatic strength and thermal shock resistance were measured and the results are shown in the table below. Here, the method for measuring thermal shock resistance is to place the filter in an electric furnace at a predetermined temperature, treat it for 20 minutes, and then let it cool (about 1 hour) at room temperature (20-30℃). Starting from the same temperature, this operation was repeated twice at each temperature, and the treatment temperature was increased sequentially at 50°C intervals, and the temperature at which the filter sound changed from a clear sound to a dull sound was evaluated as the crack initiation temperature. After that, a crack appeared on the external surface, and as the crack progressed, a force was applied in the direction of rupturing the crack, and the temperature at which the crack broke was evaluated as the breaking temperature. Comparative Example 1 The overall bulk density was 0.44 in the same manner as in Example 1, except that the step of first spraying and adhering to the side surface 2, which does not participate in ventilation, of the external surface of the three-dimensional reticulated urethane foam was not carried out. A three-dimensional network structure made of cordierite with a weight of g/cm ³ was obtained. However, the bulk density of core 1 obtained by repeating the steps of immersion in slurry, removal, and drying is 0.29 to 0.34.
g/cm ³ , and the slurry that is then applied to the side surface 2 by partial immersion is 0.18 to 0.23 g per unit area (cm ² ).
And the slurry that is sprayed and attached to the side surface 2 is
The amount was 0.08 to 0.12 g per unit area (cm ² ). Further, the amount of adhesion to the end surface 3 was the same as in Example 1. The properties of this three-dimensional network structure were measured in the same manner as in Example 1, and the results are shown in the table below. Example 2 The slurry that is first sprayed and attached to the side surface 2 is 0.14 to 0.16 g per unit area (cm ² ), and the slurry that is attached by partial immersion to the side surface 2 after obtaining the core 1 is 0.07 to 0.10 g. A three-dimensional network structure made of cordierite having an overall bulk density of 0.38 g/cm ³ was obtained in the same manner as in Example 1, except that the total bulk density was 0.38 g/cm 3 . The properties of this three-dimensional network structure were measured in the same manner as in Example 1, and the results are shown in the table below. Example 3 First, the slurry that is sprayed and attached to the side surface 2 is set at 0.04 to 0.06 g per unit area (cm ² ), and after obtaining the core 1, the slurry that is attached to the side surface 2 by partial immersion is 0.18 to 0.20 g. Example 1 was carried out in the same manner as in Example 1, except that the slurry to be sprayed and attached was changed to 0.07 to 0.10 g, and the overall bulk density was 0.44.
A three-dimensional cordierite network structure of g/cm ³ was obtained. The properties of this three-dimensional network structure were measured in the same manner as in Example 1, and the results are shown in the table below. Example 4 A three-dimensional network made of cordierite with an overall bulk density of 0.38 g/cm ³ was prepared in the same manner as in Example 1, except that all the adhesion to the side surface 2 after obtaining the core 1 was done in the form of a spray. Obtained a structure. However, the amount of the slurry deposited in the form of a spray was 0.12 to 0.16 g per unit area (cm ² ). The properties of this three-dimensional network structure were measured in the same manner as in Example 1,
The results are shown in the table below.

[Table] Comparing the results of Example 1 and Comparative Example 1 shown in the table, it is found that in the method of this invention, the three-dimensional network skeleton that appears on the external surface of the organic porous material having a three-dimensional network cell structure By applying the ceramic slurry in the form of a spray, it is possible to reduce pressure loss and provide good thermal shock resistance without substantially reducing the strength of the ceramic three-dimensional network structure. It is clear that it is effective against This means that coatings such as γ-alumina are applied to this base material, which is necessary to improve the trapping rate of diesel particulate or to support catalyst precious metals for efficient combustion removal. It plays a role in helping to increase the amount of coating when the coating is applied. In other words, if the upper limit of pressure loss is determined from the viewpoint of reducing fuel costs when installed in a vehicle, in order to cope with it, the amount of coating of γ-alumina etc. has conventionally been forced to be limited. However, as shown above, the coating amount of γ-alumina can be increased in the present invention. Furthermore, as is clear from comparing the results of Example 1 and Examples 2 and 3, the amount initially sprayed and deposited was 0.09 to 0.11 g per unit area (cm ² ) as in Example 1. is found to be optimal. That is, as shown in Example 2, if a larger amount is deposited, the effect on pressure loss reduction and the effect on thermal shock resistance are the same, but the strength is slightly reduced, and as shown in Example 3. As shown, it is clear that if a smaller amount is deposited, both the effect of reducing pressure loss and the effect of improving thermal shock resistance will be small. Next, as shown in Example 4, core 1
It is clear that the thermal shock resistance can be further improved by spraying and adhering the material to the side surface 2 which does not participate in ventilation after forming the material. Although not included in the above embodiments, the range of the bulk density of the core 1 and the weight range of the slurry per unit area attached to the side surfaces 2 and end surfaces 3 of the core 1 shown above are all based on pressure loss, strength, and This is a suitable range for the three properties of thermal shock resistance to complement each other, and various combinations can be considered within this range, but for any range, as long as the three properties are within this suitable range, the three properties All of these are excellent when used as catalyst carriers for automobile exhaust gas treatment, and especially when used as filter materials for collecting particulate matter in diesel engines, they meet the required properties for the three properties. I have confirmed that it will.

[Brief explanation of the drawing]

The figure is a schematic diagram for explaining the names of each part of the ceramic three-dimensional network structure filter shown in Examples and Comparative Examples of the present invention. 1... Core of ceramic three-dimensional network structure,
2... Side face of the ceramic three-dimensional network structure core, 3... End face of the ceramic three-dimensional network structure core.

Claims (1)

[Scope of Claims] 1. A three-dimensional ceramic network structure characterized in that all the skeletons of the core and the external surface are continuous, and the thickness of the skeleton becomes thicker as it goes outward toward the surface. 2. Ceramic slurry is sprayed and adhered to the three-dimensional network skeleton appearing on the external surface of an organic porous material having a three-dimensional network cell structure, and then the structure is immersed in the ceramic slurry to remove the excess. The process of removing the slurry and then drying it is repeated, and the ceramic slurry is sprayed and adhered to the skeleton of the three-dimensional network structure that appears on the external surface of the structure obtained in this way, and then A method for manufacturing a ceramic three-dimensional network structure, characterized by sintering it. 3. The method for producing a three-dimensional ceramic network structure according to claim 2, wherein the ceramic slurry is cordierite slurry.