JP2566886B2 - Method for producing porous sintered body having continuous pores - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a molten metal filter, a high temperature gas filter,
The present invention relates to a method for producing a porous sintered body having continuous ventilation holes suitable for a heat radiation plate, an automobile exhaust gas filter, a catalyst carrier, a bioreactor and the like.

[Conventional technology]

Conventionally, a porous sintered body having continuous vents with little pressure loss is manufactured by the method described below.

(1) A method of coating the surface of an organic three-dimensional network structure such as foamed urethane foam with a slurry of inorganic powder, followed by drying and firing. This method makes it possible to produce porous sintered bodies with various pore diameters by appropriately selecting the number of cells of the organic three-dimensional network structure. A quality sintered body can be obtained. However, in manufacturing, there is an unavoidable existence of a cavity, which is a skeleton of an organic skeleton, in the center of the skeleton of the sintered body, and there is a drawback that a porous sintered body having a high strength cannot be obtained.

(2) A method of firing a molded body obtained by three-dimensionally assembling rod-shaped or linear molded products of inorganic powder. Since the porous sintered body obtained by this method has a structure in which rod-shaped inorganic molded bodies are in point contact with each other, the strength thereof is extremely low. Further, it is impossible to strictly control the effective pore diameter in the production thereof, and there is a drawback that a filter which requires precise separation accuracy cannot be produced.

(3) A method of firing the filled body of the spherical ceramic molded product. According to this method, a porous sintered body having a desired effective pore size can be produced by appropriately selecting the particle size of the spherical inorganic molded body. However, the porosity cannot theoretically exceed about 25% which is the porosity of the close-packed body, so that there is a problem that the resulting porous sintered body has a large pressure loss.

(4) A method of filling the voids of a spherical organic substance filler with a slurry of inorganic powder, removing the organic substance after drying, and firing (Japanese Patent Application Laid-Open Nos. 50-75608 and 60-251182). This method can produce a porous sintered body having various effective pore diameters by appropriately selecting the particle diameter of the spherical organic substance. Furthermore, by giving a distribution to the particle size of the spherical organic substance, it is possible to manufacture a porous sintered body having a porosity of more than 75% and a low pressure loss. In addition, it is an excellent manufacturing method having a feature of extremely high strength due to its skeleton structure. But,
In the manufacturing process, it has a defect that cracks are easily generated. That is, a step of filling a slurry of inorganic powder and drying. Furthermore, there is a problem that cracks occur in the skeleton of the inorganic substance in the process of dissolving and removing the organic substance with an organic solvent or the process of thermally decomposing and incinerating the organic substance by heating, which makes stable industrial production difficult. .

Further, JP-A-60-251182 discloses a method of adding a self-hardening inorganic binder such as alumina cement to an aqueous slurry. However, this method has a basic defect that the inorganic substance introduced from the binder remains as an impurity in the porous sintered body after firing.

[Problems to be solved by the invention]

In view of the problems of the above existing methods, the present inventors have completed the present invention as a result of continued intensive research, and the object of the present invention is to provide a porous fired material having a small pressure loss and a high strength. It is an object of the present invention to provide a method capable of stably producing a bonded body without causing cracks.

[Means for solving problems]

The above-mentioned object is a method of manufacturing a porous sintered body by filling the voids of a resin particle molded body formed by binding resin particles with a slurry of an inorganic powder, in a slurry of the inorganic powder, a hardening type This is achieved by a method for producing a porous sintered body having continuous air holes, which is characterized by containing a resin.

Examples of the resin particles constituting the resin particle molded body applied to the present invention include polystyrene, polyethylene, polypropylene, nylon, polyester, acrylic, phenol, epoxy, ethylene-vinyl acetate copolymer, styrene-butadiene block polymer, styrene. -Isoprene block polymer, organic resin particles such as urethane and wax, and foamed products thereof can be used. Among them, styrene foam is preferable because it is inexpensive and the removal process is easy.

In order to obtain a porous sintered body having continuous pores, the resin particle molded body of the present invention needs to have particles in contact with each other. This resin particle molded body is prepared by the following method. That is, a method in which resin particles are filled in an appropriate container and compressed.
A method in which an appropriate container is filled with resin particles whose surface is coated with an adhesive and is molded. Fill the appropriate container with resin particles,
For example, a method of injecting a resin solvent for a short period of time to cause resin particles to adhere and adhere to each other and then removing the solvent.

Examples of the inorganic powder in the present invention include oxides such as alumina, zirconia, zircon, cordierite, mullite, silica, aluminum titanate, and titania, and silicon nitride,
Non-oxide powders such as boron nitride, aluminum nitride, silicon carbide and sialon can be used. Further, for the purpose of producing silicon nitride or silicon carbide by reaction sintering, metal silicon powder, carbon powder, etc. can be mentioned. Further, metal powders of nickel, iron, stainless steel, copper, aluminum, lead, zinc and the like can be mentioned.

The slurry of the inorganic powder in the present invention comprises at least the above inorganic powder, a curable resin and a dispersion medium, and if necessary, the peptizer and the slurry for efficiently and stably dispersing the inorganic powder in the dispersion medium. It may contain a viscosity adjusting agent for making workability suitable, a drying rate adjusting agent such as ethylene glycol or polyethylene glycol, a defoaming agent or an antifoaming agent for reducing foaming property, a pH adjusting agent, etc. . The slurry of the inorganic powder is prepared by a conventional method using a dispersing device such as a ball mill or an attritor.

In the present invention, the solid content concentration of the slurry of the inorganic powder is appropriately determined by the workability of filling the slurry into the voids of the resin particle molding and the degree of occurrence of dry cracks of the resin particle molding filled with the slurry. To be done. When the concentration of the slurry of the inorganic powder is low, the viscosity of the slurry is low and the filling workability is good, but the shrinkage due to the evaporation of the dispersion medium is large in the drying step, and cracks are likely to occur. On the other hand, when the concentration of the slurry of the inorganic powder is high, the filling workability is poor, but dry cracks are less likely to occur. Usually, the concentration of the slurry is preferably 40 to 95% by weight.

The hard-curable resin in the present invention is in a slurry containing an inorganic powder, and its curing action enhances skeletal strength. Therefore, the skeleton is not cracked in the drying process and the resin particle removing process. As a curable resin,
There are dry-curable resins such as so-called resin emulsions and water-soluble resins, in which resin particles are fused and solidified by drying due to evaporation of a dispersion medium, and cross-linking reaction-type resins that form three-dimensional network bonds. Specifically, there are vinyl resins such as acrylic and vinyl acetate, and soluble or dispersed resins such as epoxy, phenol, urea, melamine, and urethane. Of these, crosslinkable resins, particularly epoxy resins that undergo a crosslinking reaction in the alkaline region where the peptizer effectively acts, are preferred.

In the present invention, the addition amount of the curable resin is preferably kept to the minimum necessary amount within the range where the object of the present invention is achieved. That is, the curable resin is removed by sintering in the manufacturing process of the porous sintered body and does not remain in the final product, and excessive addition is economically disadvantageous. Further, if the amount of the curable resin added is increased, the occurrence of cracks in the degreasing process tends to be promoted, and from this point too, it is preferable to avoid excessive addition. The content of the curable resin is preferably 1 to the inorganic powder.
35% by weight, most preferably 5 to 25% by weight.

As the dispersion medium for dispersing the inorganic powder in the present invention, water, methyl alcohol, ethyl alcohol, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone and the like can be mentioned, but the resin particles constituting the resin particle molded body It is preferable to appropriately select and use one that does not dissolve. Usually, water is used as the dispersion medium because of its ease of handling, but in the case of poor water resistance such as aluminum nitride, or in the case of inorganic powders that need to avoid surface oxidation, use a non-aqueous solvent. Good to do.

In the present invention, as a method for filling the voids of the resin particle molded body with the slurry of the inorganic powder, a simple pouring method,
The pressure injection method, the reduced pressure injection method, the vibration injection method, etc. can be mentioned. The inorganic powder enhances the strength of the skeleton by hardening the curable resin after the resin particle molding filled with the slurry is taken out from the container and dried while being held in the container, or in the process of being taken out from the container and dried. Curing conditions are appropriately selected depending on the type of curable aqueous resin used. In the case of dry-curing resin, air drying or heat drying method is used. In the case of a crosslinking reaction type resin, it is usually treated at 40 to 95 ° C for 0.5 to 10 hours. When the curing reaction is an exothermic reaction, it is advantageous because the temperature rise due to self-heating can be utilized. The resin particles are then removed from the molded body having the skeleton strength increased by the curing reaction. The removal method may be a method of impregnating the resin particles with a solvent that dissolves the resin particles, or a method of incinerating together with the curable water-based resin in a degreasing step prior to firing.

Degreasing and firing of the porous fired body are carried out by a conventional method. For example, in the case of oxide powder, the degreasing step gasifies and incinerates the contained organic matter by raising the temperature to 500 to 600 ° C. at a relatively moderate temperature raising rate. The firing process is usually 1200-1800
It is carried out by high temperature treatment at ℃. The atmosphere is usually an atmospheric atmosphere, but the degreasing firing conditions and the atmosphere thereof are appropriately selected depending on the type of inorganic powder and the like.

〔The invention's effect〕

According to the method of the present invention, it is possible to stably manufacture a porous sintered body having a small pressure loss and a high strength without generating cracks.

 The present invention will be specifically described below with reference to examples.

Example 1 Styrofoam classified into a particle size of 8 mm was 50 × 100 × 100 mm.
After oscillating and filling a female container of dimensions, compress it to a size of 40 x 100 x 100 mm and fix it with a male type having an injection port in the center.
The alumina slurries having various compositions shown in Table 1 were vibrationally injected by the above injection. Here, the alumina slurry was prepared using a ball mill. After heat treatment at 80 ° C. and 100% relative temperature for 5 hours, it was air-cooled and demolded. The demolded molded body was immersed in ethyl acetate for 5 minutes to dissolve the styrofoam, and this was air-dried to obtain a green body. The green body was placed in an electric furnace having a silicon carbide heating element and fired at 600 ° C. for 2 hours and then at 1550 ° C. for 6 hours in an air atmosphere for firing.

The results obtained are shown in Table 1. Here, all the aqueous slurry compositions are shown in terms of pure content.

[Appearance Evaluation Criteria] O: No cracks are recognized.

Δ: A slight crack is recognized.

X: Many cracks are recognized.

[Evaluation method of compressive strength]

A test piece having a size of 30 × 50 × 50 mm was cut out, and a compression fracture test was performed at a head speed of 0.05 mm / min. The average value of a total of 5 measured values was taken as the compressive strength.

Example 2 A solvent-free epoxy resin was coated on the surface of Styrofoam particles having a particle diameter of 2 mm, and then the inner diameter was 50 mm and the length was 100 m.
It was filled in a cylindrical acrylic resin container of m. A pressure of 1 kg / cm ² was applied in the length direction, and the state was left for 1 day to prepare a resin particle molded body. An aqueous slurry having the composition shown below was poured into a resin particle molded body, heat-treated at 50 ° C. under a relative humidity of 100% for 12 hours, and then air-cooled and demolded. The demolded molded body was dried at room temperature and further heat-treated at 80 ° C. for 10 hours to obtain a green body. The green body was placed in the electric furnace shown in Example 1, heated to 500 ° C., and then held at 500 ° C. for 2 hours for degreasing treatment. Further, the temperature was maintained at 1400 ° C. for 5 hours for firing.

[Aqueous slurry composition]

Aluminum oxide powder 45 Cordierite powder 55 Peptizer 0.5 Ethylene glycol 2 Curable aqueous resin 20 Defoamer 1 (part) Water 39.2 Solid content concentration 75% wt% Curable resin / inorganic powder ratio 20% wt% Various resins shown in Table 2 were used. Second result obtained
Shown in the table.

Here, in No. 13 and No. 14, paratoluenesulfonic acid was added to the aqueous slurry to adjust its pH to 2 to 2.5.

Example 3 A green body was obtained according to Example 1 using a slurry having the composition shown below. The styrofoam used here was classified to have a particle size of 5 mm.

[Slurry composition]

Silicon nitride powder 90 Magnesium oxide powder 3 Aluminum oxide powder 2 Itcrum oxide powder 5 Peptizer 0.8 Denacol EX421 12.5 Triethylenetetramine 2.5 Defoamer 1 Ethyl alcohol 40 (parts) The obtained green body was defatted according to Example 2. Processed. Then, the degreased body obtained was placed in an atmosphere furnace,
Firing was carried out by holding at 1750 ° C. for 4 hours under nitrogen gas at atmospheric pressure. The obtained porous fired body was in a good state with no cracks or warpage.

Example 4 A green body was obtained according to Example 2 using a slurry having the composition shown below.

[Slurry composition]

SUS316 powder 100 Peptizer 1 Denacol EX421 8.3 Triethylenetetramine 1.7 Defoamer 1 Ethyl alcohol 30 (parts) The green body was degreased according to Example 2. Then, the obtained degreased body was placed in an atmosphere furnace and baked at 1260 ° C. for 1 hour under hydrogen gas at 1 atm for firing. The obtained porous fired body was in a good state with no cracks or warpage.

Claims (4)

(57) [Claims] 1. A method of manufacturing a porous sintered body by filling a void of a resin particle molded body formed by binding resin particles with a slurry of an inorganic powder, wherein a curing type is used in the slurry of the inorganic powder. A method for producing a porous sintered body having continuous air holes, characterized by containing a resin. 2. A method for producing a porous sintered body having continuous pores according to claim 1, wherein the curable resin is contained in an amount of 1 to 35% by weight based on the inorganic powder. . 3. A method for producing a porous sintered body having continuous ventilation holes according to claim 1, wherein the curable resin is contained in an amount of 5 to 25% by weight based on the inorganic powder. . 4. The method for producing a porous sintered body having continuous ventilation holes according to any one of claims (1) to (3), wherein the curable resin is an epoxy resin.