JP3224645B2 - Ceramics molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming ceramics, and more particularly, to a method for forming ceramics suitable for producing a ceramic formed body having a complicated shape.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a ceramic molded body having a complicated shape, an injection molding method, a slurry casting method, a wet pressure molding method, and the like are known.

Here, the injection molding method is a kind of plastic molding. In order to give plasticity to a ceramic powder, a considerable amount of an organic binder composed of a resin such as polyethylene and polystyrene and a wax is mixed with the ceramic powder. In this method, the obtained mixed raw material is injected at a high pressure into a mold tightly closed by an injection plunger or a screw to obtain a ceramic molded body.

In the slurry casting method, a uniform slurry is prepared by mixing a ceramic powder with a dispersion medium such as water and a deflocculant, and the slurry has a water absorption property such as a gypsum mold. This is a method of obtaining a ceramic molded body by injecting it into a mold.

[0005] Further, the wet pressure molding method refers to a method in which a molding aid such as water and a binder is added to and kneaded with a ceramic powder to prepare a ceramic clay, and the obtained ceramic clay is molded into a mold having a water absorbing property. Fill in a mold that can be suctioned,
This is a method for producing a ceramic molded body by applying pressure.

[0006]

However, here,
First, in the method for obtaining a ceramic molded body by the injection molding method described above, a degreasing step for removing the organic binder from the molded body is performed in order to mix a considerable amount of an organic binder into the ceramic powder at the time of its production. There is a problem that it takes a long time, and the molded article tends to be distorted or cracked due to a difference in degreasing speed between the inside and the outside of the molded article.

In the method of obtaining a ceramic molded body by the slurry casting method, cracks are liable to be formed in the molded article when drying and shrinking in the production of a complicated shaped product.
There is a problem that the molding itself takes a long time.

Further, in the above-mentioned wet pressure molding method, since the mold filled with the ceramic clay is pressed at a high pressure, the obtained molded body is in close contact with the mold, and it is difficult to release the molded body. And at the same time, there is a problem that cracks of the molded body easily occur at the time of mold release.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional ceramic molding method, and has as its object to shorten the molding time, to have good releasability, and to make the appearance crack or deform. It is an object of the present invention to provide a novel method for forming ceramics, which can obtain a molded article free of ceramics.

[0010]

The present inventors have made intensive studies to achieve the above object, and as a result, the non-aqueous solvent-type water-curable resin has high plasticity and cures immediately upon contact with water. The present inventors have paid attention to the fact that they have the property of stabilizing the shape, and have found that this is blended as a binder (forming aid) for the ceramic clay, thereby completing the present invention.

That is, according to the present invention, a ceramic clay obtained by mixing and kneading a non-aqueous solvent type water-curable resin as a binder with ceramic powder is injected under pressure into a hydrated porous molding die. The present invention provides a method for forming ceramics.

According to the method of forming a ceramic according to the present invention, the non-aqueous solvent-type water-curable resin present in the ceramic clay is injected under pressure into the hydrated porous forming die. Immediately after, it comes into contact with the moisture that has exuded from the mold, and cures the molded body without deforming it.
Since the molded body has sufficient strength for handling immediately, the molded body can be released from the molded body in a short time, and the releasability between the molded body and the mold is improved.

In the present invention, the preparation of a ceramic clay containing the non-aqueous solvent-type water-curable resin is performed,
It was performed by a vacuum kneading step (claim 2). Thereby, since the pressure is reduced during the preparation of the ceramic clay, the diffusion of the organic solvent in the clay becomes remarkable, and the formation of the liquid layer film of the clay becomes faster, so that a homogeneous clay is obtained. .

Further, in the present invention, the ceramic clay containing the non-aqueous solvent type water-hardening resin is injected under pressure into a molding die, and the ceramic clay is once held in the clay holding portion. This was performed later (claim 3). As a result, a homogeneous clay can be prepared, and the molding conditions such as the pressure injection speed can be easily set in accordance with the compact, and a compact without forming defects can be obtained.

The non-aqueous solvent-type water-curable resin used in the present invention includes a non-aqueous solvent-type water-curable polyurethane resin or a polyester derivative. The curable resin is used by being mixed with an organic solvent such as acetone or xylene depending on the hardness of the clay.

The ceramic clay used in the present invention comprises ceramic powder, a molding aid such as the above-mentioned non-aqueous solvent-type water-curable resin, and an organic solvent, and if necessary, a sintering aid. May be added. As the ceramic powder, other than oxides such as alumina and zirconia, nitrides such as silicon nitride, carbides such as silicon carbide, and composite materials thereof can be used. In particular, the type of the auxiliary is not particularly limited, and generally known Mg, Al, Y, Ce, Z
Sintering aids such as oxides such as r, Sr, B, and Ta, nitrides, and carbides can be used.

The mixing ratio of the non-aqueous solvent type water-curable resin and the organic solvent to the ceramic powder is 10 to 45 parts by weight of the organic solvent with respect to 100 parts by weight of the ceramic powder containing the sintering aid. It is preferable to use 0.5 to 30 parts by weight of a molding aid such as a non-aqueous solvent-type water-curable resin and a dispersant. This is because if the proportion of the organic solvent is less than 10 parts by weight, the kneading property is poor and a homogeneous molding clay cannot be obtained. This is because the density of the particles decreases and the firing shrinkage increases, making it difficult to obtain a product with high dimensional accuracy. When the amount of the molding aid such as the non-aqueous solvent-type water-curable resin and the dispersant is less than 0.5 part by weight, the effect is not obtained, and when the amount exceeds 30 parts by weight, it takes time to remove the molding aid. This is because cracks easily occur in the product.

When the ceramic clay is prepared by the vacuum kneading step, a generally used apparatus combining a back mill and an auger machine can be used as the vacuum kneading machine. The degree of vacuum in the kneading step may be in a reduced pressure state, but is usually 60 cm.
Hg or more is preferable. Further, in the production of a product requiring high strength, the degree of vacuum in the vacuum kneading step is preferably 70 cmHg or more, since air bubbles in the clay cause breakage.

As the porous mold used in the present invention for injecting the prepared ceramic clay under pressure, a conventionally known porous mold may be used as long as it has good air permeability and can guarantee the strength of the mold itself. And a porous mold having an average pore diameter of 0.1 to 50 μm is usually used. Also,
In a two-layer structure in which the average pore diameter is different between the molding surface layer and the lower surface layer, the molding surface layer has a pore diameter of 0.1 to 50 μm, and the lower surface layer has a coarse pore diameter of about 50 to 500 μm. Types can also be used. The material of the porous mold is not particularly limited, and may be gypsum, resin, ceramic,
Metals and composite materials thereof can be used.

The pressure for injecting the ceramic clay into the porous mold is preferably 5 kg / cm ² or more. This is because if the pressure is less than 5 kg / cm ² , the clay is not filled, or the density of the formed body is reduced, so that deformation is likely to occur. Although it is possible to use a high pressure exceeding 500 kg / cm ² as the injection pressure, the operability is poor because the molding die becomes large and heavy due to the high pressure, and the molding machine becomes large. Injection pressure is 50
It is preferable to carry out at 0 kg / cm ² or less.

In the case where the injection of the pressurized ceramic body into the forming mold is performed after the ceramic body is once held in the body holding section, the kneaded clay holding section is specifically described. Is preferably a plunger type extruder, and other ordinary cylinders and the like can also be used. Also,
It is necessary to set the size of the injection port of the kneaded material holding portion into the molding die according to the shape and volume of the molded body, but in order to reduce friction between the kneaded material holding portion and the kneaded material, The larger the size, the better.

[0022]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples according to the present invention and comparative examples, but the present invention is not limited to the following examples.

100 parts by weight of silicon carbide powder having an average particle diameter of 0.7 μm containing a sintering aid, 25 parts by weight of xylene, 1 part by weight of a dispersant, and a non-aqueous solvent-type water-curable resin as a binder A water-solvent water-curable polyurethane resin (trade name: Coronate 2014, manufactured by Nippon Polyurethane Industry Co., Ltd.) was prepared at the ratio shown in Table 1 and kneaded with a pressure kneader.

Thereafter, each of the above kneaded materials is vacuum kneaded, and a ceramic clay having a diameter of 20 mm and a length of 100 mm is extruded from a vacuum clay kneader, and the ceramic clay is removed from a turbine rotor (blade diameter: 85 mm, blade height: 30 mm) into the kneaded clay holding section of the forming apparatus, the pressurizing piston of the kneaded clay holding section is lowered, and the ceramic kneaded clay is temporarily removed in a state where the vacuum degassing in the kneaded clay holding section is performed. It was held in the kneaded clay holding part.

Thereafter, the ceramic clay held in the clay holding section is pressure-injected into a hydrated porous mold for forming a turbine rotor at each pressure shown in Table 1.
After 200 seconds, compressed air was introduced into the mold, whereby moisture in the mold was exuded to cure the molded body, and the molded body was released from the mold.

Table 1 shows the molding results (releasability, appearance cracks and the presence or absence of unfilled portions) of the molded articles obtained by the above operation. Further, the obtained molded body is placed in a thermostat for 1 hour.
Table 1 shows the presence or absence of appearance cracks of each degreased body obtained by heating to 450 ° C. at a heating rate of 0 ° C./hr to degrease the binder and the like in the molded body.

For comparison, a non-aqueous solvent-type water-curable resin was not used, and instead, ethyl cellulose was used as a binder. Table 1 also shows the molding results (release properties, presence / absence of appearance cracks and unfilled portions), and presence / absence of appearance cracks of the degreased body.

[0028]

[Table 1]

From Table 1, it can be seen that all of the products of Examples according to the present invention have good releasability, unlike the products of Comparative Examples. However, in the example product (Example 3) in which the injection pressure of the ceramic clay into the molding die is less than 5 kg / cm ² , there is an unfilled portion at the tip of the blade, and
In the example product (Example 4) in which the amount of the binder added was less than 0.5 wt%, cracks were observed in the molded body, and the
%, Cracks were observed in the degreased body. In addition, in the comparative example product, the releasability was poor, and cracks were observed in both the molded body and the degreased body.

[0030]

As described above, the ceramic molding method according to the present invention described above involves adding a non-aqueous solvent type water-curable resin as a binder and kneading the ceramic clay into a water-containing porous molding die. It has the greatest feature in pressure injection, which has a remarkable effect of improving the releasability of the molded body, shortening the molding time, and further improving the appearance of the molded body without cracks and deformation. Obtainable.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-261251 (JP, A) JP-A-63-299907 (JP, A) JP-A-54-105109 (JP, A) JP-A-5-105 178652 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B28B 1/24 B28B 1/00

Claims (3)

(57) [Claims] 1. A non-aqueous solvent-type water-curable resin is mixed and kneaded with a ceramic powder as a binder to prepare a ceramic clay, and then pressure-injected into a porous mold containing the ceramic clay. A method for forming a ceramic, comprising forming a ceramic formed body. 2. The method according to claim 1, wherein the preparation of the ceramic clay is performed by a vacuum kneading step.
The method for forming a ceramic according to the above. 3. The method according to claim 1, wherein the pressure injection of the ceramic clay into the forming mold is performed after the ceramic clay is once held in the clay holding portion. The method for forming a ceramic according to the above.