JPS6161978B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a porous ceramic structure used in a carrier for collecting particulate (carbon-based fine particles) discharged from a diesel engine, a high-temperature filter, a catalyst carrier, a heat exchanger, etc. .

As a conventional example of this type, a porous ceramic structure having an internal communication space formed by a ceramic skeleton having a three-dimensional network structure is known.

Such a conventional structure has a weak strength because of its structure, and therefore, it is necessary to reinforce its outer periphery with a ceramic reinforcing wall, and various inventions and ideas have been proposed in this regard.

The present invention aims to improve the strength and thermal shock strength of the porous ceramic structure by reinforcing the outer periphery of the porous ceramic structure as described above with a ceramic reinforcing wall of a new structure.

The present invention will be explained in detail below using specific examples. In FIGS. 1A and 1B, reference numeral 1 denotes a cylindrical porous ceramic body, and when used for collecting particulate matter of exhaust gas, this porous ceramic body 1 becomes a collection part. This porous ceramic body 1 has a ceramic skeleton 1a having a complicated three-dimensional network structure, and an internal communication space 1b formed between them.

2 is a reinforcing wall. This reinforcing wall 2 is provided over the entire outer periphery of the porous ceramic body 1 (excluding both end faces). This reinforcing wall 2 is composed of voids 2a having a three-dimensional network structure and a ceramic body 4 having micro voids 3 therein. This ceramic body 4 is arranged so as to be surrounded by voids 2a having a three-dimensional network structure.

In addition, the size of the microgap 3 is about 10 to 2000μ.

Note that FIG. 1B mentioned above shows only the reinforcing wall 2 in cross section, and the cross section of the skeleton 1a of the porous ceramic body 1 is as shown in FIG. In FIG. 2, 1c is a cavity inside the skeleton 1a, which is formed by combustion and scattering of the organic substance skeleton, which will be described later.

Next, a general method for manufacturing the above-mentioned porous ceramic structure will be described by giving a specific example. As raw materials for the porous ceramic body 1, 100 parts of cordierite raw material powder (parts by weight; the same applies hereinafter), 100 to 150 parts of water,
A cordierite slurry is prepared by kneading 3 to 7 parts of an organic binder (eg, methylcellulose, polyvinyl alcohol). An organic material with a three-dimensional network structure (e.g., polyurethane foam) having a cylindrical shape with 8 to 13 cells/inch per unit length is immersed in this slurry, and after immersion, the cord remaining in the organic material is immersed. Remove excess Elite slurry by centrifugation, compressed air, etc., and heat at 100 to 120℃ for 2 to 3 hours.
Dry for an hour. The above dipping-drying process is repeated until the skeletal surface of the organic substance is completely covered with the raw material fine powder.

On the other hand, as raw materials for the reinforcing wall 2, 100 parts (parts by weight) of cordierite raw material powder, 40 to 60 parts of water, 3 to 7 parts of an organic binder (for example, methyl cellulose, polyvinyl alcohol), and the sintering temperature of the cordierite raw material 10 to 20 parts of combustible fine particles (e.g. carbon particles) that burn out at low temperatures are mixed to prepare a slurry. This slurry has a higher viscosity because it contains less water than the previous slurry.

The number of cells per unit length of this slurry is 30 to 50/
Using a spatula, etc., apply the slurry evenly to the surface of a three-dimensional network-structured organic material (e.g., polyurethane foam) with a thickness of 1 to 3 mm and a length equal to the outer circumference of the porous ceramic body 1. Push it into. This is wrapped around the outer periphery of the above-mentioned organic substance, the ends are completely aligned, and then dried. After drying,
Add 100 parts of cordierite raw material powder, 100 to 150 parts of water, and an organic binder (e.g., methyl cellulose, polyvinyl alcohol) to the combined organic substances.
The process of immersing in the material obtained by kneading 3 to 7 parts and drying is performed several times. Then 1300-1470
Bake at ℃ for 5-10 hours.

By such firing, a porous ceramic structure having the structure shown in FIGS. 1A and 1B is obtained.

The slurry for forming the reinforcing wall 2 has a higher viscosity than the slurry for forming the porous ceramic body 1, so when applied to the surface of the organic matter, it will not only affect the surface of the skeleton of the three-dimensional network structure, Sludge also adheres to the internal communication space between the skeletons. Moreover, the space is filled with slurry by repeating the slurry dipping and drying process described above.

When an organic substance under such conditions is fired, its three-dimensional network skeleton burns and scatters.
At the same time, the combustible particles (for example, carbon particles) are also burned and scattered. Therefore, the structure of the reinforcing wall 2 is as shown in FIGS. 1A and 1B.

According to the above structure, when the porous ceramic body 1 is used as a collection material for particulate matter discharged from a diesel engine,
Collect the particulate matter. On the other hand, the reinforcing wall 2 serves to improve the mechanical strength of the structure and also to prevent gas that has flowed into the porous ceramic body 1 from leaking from the side surfaces.

By the way, the internal structure of the reinforcing wall 2 has a three-dimensional network structure in which the gaps between the organic skeletons are replaced with ceramic, and the presence of traces of the organic skeleton and the flammable fine particles added to the ceramic slurry, which are uniformly dispersed inside the ceramic. It has a structure in which the generated pores are used as voids.

With this structure, a uniform load can be applied from the outer periphery compared to a reinforced wall with a similar structure to the organic skeleton (hereinafter referred to as a comparative example), which is made by attaching a ceramic raw material to the surface of the organic skeleton and firing it. In terms of isostatic strength, which measures the resistance force, the strength of the present invention is 30 to 40 Kg/cm ² , which is superior to that of the comparative example, which is 10 to 15 Kg/cm ² . This is because inside each ceramic skeleton of the reinforcing wall in the comparative example, a cavity remains as a trace of the organic skeleton that became the core material, making it look like a hollow pipe, and the proportion of the ceramic material in the reinforcing wall is 5. On the other hand, the reinforcing wall 2 of the structure of the present invention has a structure in which the reinforcing wall 2 of the structure of the present invention surrounds the ceramic body 4 having the void 3 by the void 2a of the three-dimensional network structure. The ceramic content in the reinforcing wall 2 is as large as approximately 90% by volume, and therefore the strength of the reinforcing wall 2 in the present invention is improved, which in turn improves the strength of the entire structure.

On the other hand, with regard to thermal shock resistance, it is known that this property is mainly determined by porosity and strength, and materials with high porosity and excellent strength have excellent thermal shock resistance. Although the comparative example is very good in terms of porosity, the strength of each skeleton of the reinforced wall is weak, so large cracks occur in the reinforced wall at 600 to 650℃ during the thermal shock test. In the structure of the present invention, although the apparent porosity tends to decrease, due to the improvement in strength, the thermal shock resistance temperature is 700 to 750°C, which is higher than that of the comparative example. In addition, in the cordierite structure shown in this example, the raw material is
By utilizing the fact that the particle size of the MaO (magnesia) supply component has a large effect on the porosity of the produced cordierite ceramic itself, it is possible to make the ceramic itself porous, which further increases its resistance to heat shock. . Furthermore, since the amount of combustible fine particles added to the ceramic slurry that is the raw material for the reinforcing wall 2 can be arbitrarily selected, there is also the advantage that both strength and thermal shock resistance can be achieved in accordance with the purpose of the structure.

In the examples of the present invention, carbon particles were used as the combustible particles, but other inorganic or organic substances (for example, wood chips) may be used, as long as they are dispersed by combustion.

Further, the material of the porous ceramic structure is not limited to cordierite, and various ceramic materials can be used.

In summary, the present invention has the effect of improving the mechanical strength and thermal shock resistance of a porous ceramic structure.

[Brief explanation of the drawing]

1A and 1B are a perspective view and a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line XX in FIG. 1B. 1... Porous ceramic body, 1a... Skeleton, 1b
...Space, 2...Reinforcement wall, 2a...Void in three-dimensional network structure, 3...Minute void, 4...Ceramic body.

Claims (1)

[Claims] 1. A ceramic structure in which a reinforcing wall is provided around the outer periphery of a porous ceramic body having an internal communication space formed by a ceramic skeleton with a three-dimensional network structure,
A porous ceramic structure in which the reinforcing wall is constituted by a structure including a ceramic body having micro voids inside around the voids of a three-dimensional network structure.