JP3175455B2 - 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. More specifically, the present invention relates to a method for forming a dense ceramic molded body that does not include fine voids.

[0002]

2. Description of the Related Art Ceramics are excellent in strength, fire resistance, corrosion resistance, insulation and the like, and are currently important materials for various electronic materials and mechanical parts. Various methods for forming such ceramic products are known, and examples thereof include a casting method, an extrusion method, and a pressing method. Among them, the extrusion method is to obtain a rod-shaped molded body by attaching a die having a desired cross-sectional shape to an extruder and extruding a clay-like material composed of ceramic powder, water, and a binder component therefrom. is there.

[0003] The above-mentioned extrusion molding method aims at producing a product having a long and uniform cross section such as a rod or a pipe, and is not suitable for producing a product whose cross section changes in the longitudinal direction. In order to manufacture a product having such a cross section that changes in the longitudinal direction, it is necessary to perform in-mold extrusion. However, conventional extrusion molding materials do not consider the releasability at all, and therefore, such When performing extrusion molding in a mold using a suitable extrusion molding material, the molded body sticks to the mold due to the effect of the binder component contained in the material, and it is difficult to remove the molded body from the mold. Was.

[0004] In order to solve this problem, the present inventor has previously performed in-mold extrusion molding using a predetermined amount of a ceramic composition containing methylcellulose, stearic acid, glycerin and water. It has been found that a molded article having no cracks and good releasability can be obtained (Japanese Patent Laid-Open No. 5-155028).

[0005] However, even when the above composition is used, in molding by extrusion in a mold, when the clay-like material is filled into the mold, air is entrapped inside the composition due to shearing, so that the entire molded article is formed. Was difficult to densify.

In order to obtain a dense ceramic molded body, a vibration molding method has conventionally been used. In this method, a ceramic powder is mixed with a solvent such as water, a dispersant, a lubricant, and the like, if necessary, a high-concentration slip of the ceramic powder is prepared, and the slip is filled in a gypsum mold while applying vibration. This is for molding.

In this method, in order to obtain a high-strength ceramic sintered body, it is necessary to use very fine ceramic powder (average particle size of about 0.3 μm) as a material. However, when such a fine powder is used, it is difficult to prepare a slip having a high powder concentration. This means that the finer the particles, the greater their specific surface area, and therefore the amount of solvent for preparing the slip needs to be increased,
As a result, a high-concentration slip cannot be prepared.

Further, in order to prepare a high-concentration slip, it is necessary to examine a dispersant for dispersing the ceramic powder in a solvent. A slip is not always obtained, and it is difficult to prepare a high-concentration slip in this respect as well.

In addition, in the above-mentioned vibration molding method, it takes a very long time to remove the solvent from the molded body. Further, in order to absorb water in the mold, it is necessary to dry the mold after molding, it takes time to prepare the mold, and it is difficult to perform precise processing with the plaster mold, and it is later processed to obtain a desired shape. There are problems such as necessity.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an in-mold molding method for ceramics which solves the above-mentioned disadvantages of the conventional ceramic molding method and gives a dense molded body.

[0011]

The inventor of the present invention has conducted intensive studies to solve the above-mentioned problems of the conventional ceramic molding method, and as a result, the above-described ceramic molding composition proposed by the present inventor. The present invention was found to granulate the composition using a material, fill the mold into a mold, and then apply vibration, whereby the particles are fluidized, and a dense ceramic molded body containing no voids can be obtained. Was completed.

That is, in the method for molding ceramics of the present invention, 0.3 to 0.6 parts by weight of methylcellulose (MC) and 0.6 to 0.6 parts by weight of stearic acid (S) are added to 100 parts by weight of ceramic powder.
1.2 parts by weight, glycerin (G) 0.7 to 1.1 parts by weight, and 34
~ 37 parts by weight of water, and the total amount of MC + S + G is 1.8 ~
After supplying 2.9 parts by weight of a granulated product for ceramics molding into a mold, vibration is applied under pressure.

The ceramic powder used in the molding method of the present invention includes oxide ceramics such as alumina, zirconia, and mullite; carbide ceramics such as silicon carbide and titanium carbide; nitride ceramics such as silicon nitride and boron nitride; Or a mixture thereof, and a sintering aid such as yttrium oxide and spinel may be added thereto. The particle size of the ceramic powder, from the point of sintering,
It is preferably fine.

The composition of the binder component is ceramic powder
0.3-0.6 parts by weight of methylcellulose (MC), 0.6-1.2 parts by weight of stearic acid (S), glycerin
(G) 0.7 to 1.1 parts by weight, and the total amount of MC + S + G is 1.
It is preferably from 8 to 2.9 parts by weight, most preferably 0.3 parts by weight of methylcellulose, 0.6 parts by weight of stearic acid and 1.0 part by weight of glycerin.

If the amount of each component of the binder component is less than the lower limit of the above range, the fluidity of the material is low, so that when the in-mold molding is performed, the material is not filled into the mold neatly. When the amount of each component of the binder component is larger than the upper limit of the above range, the material becomes soft, and further, cracks occur when sintered. When the amount of methylcellulose is less than the above lower limit, cracks are likely to occur in the ceramic molded body after drying, and when the amount is more than the upper limit, the ceramic molded body becomes soft and shape retention is easily impaired. If the amount of stearic acid is less than the above lower limit, desired releasability cannot be obtained, and if it is more than the upper limit, defects tend to occur in the sintered ceramic. If the glycerin content is less than the above lower limit, the density does not increase and the slip of the ceramic material is deteriorated. If the glycerin content is more than the upper limit, the molded article becomes soft and sticky.

The amount of water is such that the granulated article of the ceramic composition is fluidized when vibration is applied to the granulated article. This amount is 34 parts per 100 parts by weight of ceramic powder.
~ 37 parts by weight (110 ~ 100% by volume of ceramics powder)
120% by volume) is most preferred. If the amount is less than 34 parts by weight, the ceramic is unlikely to be liquefied. If the amount is more than 37 parts by weight, the liquid remains in the mold even after the vibration is stopped, and the shape retention is poor.

In the method of the present invention, a ceramic molding composition comprising the above components is granulated. The granulation method is not particularly limited, and a general method may be used. The granulated product thus granulated does not need to be fine particles as used in the conventional vibration shaping method, and may have a size of about 500 μm or less.

Next, the granulated product is supplied into a mold. There is no particular limitation on the mold, and a mold having a simple cylindrical shape, as well as a valve whose shape changes in the axial direction, such as a valve, can be used.

After supplying the granulated product into the mold, vibration is applied to the entire mold. At this time, a punch or the like is placed on the granulated product to prevent the granulated product from jumping out of the mold. The vibration device is not particularly limited. By applying the vibration, the granulated product is liquefied, and in the process, the internal air is exhausted, and as a result, a dense compact is obtained. Therefore, it is necessary to apply sufficient vibration to cause such an effect. As a vibration condition causing such an action, for example, an acceleration of 60 m / s ² or more is preferable.

By applying this vibration, the granulated product is fluidized and densified into the shape of a mold, and a molded product having a desired shape is obtained. Thereafter, the molded body is taken out of the mold and sintered by a usual method to obtain a ceramic sintered body.

[0021]

According to the method of the present invention, the granulated product of the ceramic molding composition is vibrated in a mold to liquefy the granulated product from a solid state. Therefore, the liquefied ceramic molding composition moves along the shape of the mold and gives a compact having a dense desired shape. In addition, the water contained in the granulated product oozes out during molding and forms a water film between the molded body and the inner surface of the mold. And the molded body can be smoothly removed from the mold.

[0022]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 Ceramic powder (Si ₃ N ₄ : 90 parts by weight, Y ₂ O ₃ : 6 parts by weight,
MgAl ₂ O ₃ : 4 parts by weight) 100 parts by weight, methyl cellulose 0.3
Parts by weight, 1.0 part by weight of glycerin, 0.6 part by weight of stearic acid and about 40 parts by weight of water were sufficiently mixed and kneaded by a kneader. The kneaded material was pulverized in a mortar and passed through a sieve having an opening of 500 μm (hereinafter referred to as a granulated product).

Next, the water content of the granulated product is measured and, if necessary, dried, and the water content is determined based on 100 parts by weight of the ceramic.
Adjusted to 31, 34 and 37 parts by weight.

Next, this granulated product is used as shown in FIG.
The mold was placed in a mold having a cavity having a diameter of 20 mm and a length of 70 mm. Thereafter, as shown in FIG. 2, a punch for determining the upper shape of the molded body was inserted on the granulated product. This punch was fixed to the mold with rubber to prevent it from coming off the mold when subjected to vibration. In this state, the exciter was started and 180,
Vibration was applied so as to give an acceleration of 120 and 60 m / s ² to perform molding. Immediately after molding, the molded body was taken out of the mold.

Thereafter, the molded body was dried at 30 ° C. for 24 hours and degreased at 480 ° C. The relative density of each of the obtained degreased bodies was measured. The results are shown in Table 1 and FIG. This was fired at a maximum temperature of 1650 ° C. for 4 hours, and the relative density of the fired body obtained was measured.
% TD, and it was found that it was fired densely.

Example 2 0.7 parts of glycerin was added to 100 parts by weight of ceramic powder.
Except for using parts by weight, a molded article was produced in the same manner as in Example 1, and the relative density was measured. The results are shown in Table 1 and FIG. A dense molded article was obtained by the method of the present invention.

Example 3 A molded body was produced in the same manner as in Example 1, except that 0.6 parts by weight of methylcellulose, 1.1 parts by weight of glycerin, and 1.2 parts by weight of stearic acid were used per 100 parts by weight of the ceramic powder. The relative density was measured. Table 1 shows the results.
And FIG. A dense molded article was obtained by the method of the present invention.

[0029]

[Table 1]

[0030]

According to the method of the present invention, after filling a molding material in a mold, vibration is applied to change the material in the mold from a solid state to a liquid at normal temperature, and the material is moved so as to follow the shape of the mold. ,
A molded article having a desired shape is obtained. Therefore, since the material is liquefied in the mold, it is not necessary to liquefy the material before filling the material into the mold, and an apparatus for the liquefaction can be omitted.
In addition, since it is solidified in the mold after molding, there is no need to perform dehydration as in the case of using a gypsum mold, and the molding time can be shortened. Furthermore, the method of the present invention has good productivity such as press molding, and a shape that is difficult to mold by press molding, for example, a shape whose shape changes in the axial direction such as a valve, also uses a mold. It is possible to mold.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a mold used in the method of the present invention.

FIG. 2 is a schematic view of a molding apparatus used in the method of the present invention.

FIG. 3 shows the moisture content, the vibration conditions, and the water content of the granulated product in Example 1.
3 is a graph showing the relationship between the relative density of the obtained molded body and the obtained molded body.

FIG. 4 shows the moisture content, vibration conditions, and the like of the granulated product in Example 2.
3 is a graph showing the relationship between the relative density of the obtained molded body and the obtained molded body.

FIG. 5 shows the moisture content, vibration conditions, and
3 is a graph showing the relationship between the relative density of the obtained molded body and the obtained molded body.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B28B 3/02 C04B 35/628 C04B 35/632

Claims (1)

(57) [Claims] Claims 1. A cellulose powder (100 parts by weight), methyl cellulose (MC) 0.3 to 0.6 parts by weight, stearic acid
(S) 0.6 to 1.2 parts by weight, glycerin (G) 0.7 to 1.1 parts by weight, and 34 to 37 parts by weight of water, and the total amount of MC + S + G is 1.8 to 2.9 parts by weight for ceramic molding. A method for forming a ceramic, comprising: applying a vibration under pressure after supplying a granulated product into a mold.