JPH0672043B2 - Manufacturing method of magnesia porcelain - 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 manufacturing magnesia (MgO) porcelain, and is particularly suitable for manufacturing various magnesia porcelains used for crucibles, sheaths, boards, etc. for firing electronic materials or melting metals. The present invention relates to a method for manufacturing magnesia porcelain.

[0002]

2. Description of the Related Art Magnesia porcelain is widely used for crucibles, sheaths, boards, etc. for firing electronic materials or melting metals.

Conventionally, a rubber pressing method and a die pressing method have been mainly adopted as a molding method in the manufacturing process of magnesia porcelain. In these molding methods,
Since the fluidity of the particles is extremely important, in molding, first, the raw material of electro-melted magnesia or deadburn clinker-like magnesia particles is finely pulverized into primary particles,
Secondary particles are formed from the primary particles to form a molding raw material. When forming the secondary particles, since magnesia is a hydratable substance, the primary particles are suspended in an alcoholic solution to form a slurry, and the particles are spheroidized by a spray drying method to obtain secondary particles.

The molded body molded by such a conventional molding method is usually fired at 1400 to 1700 ° C. to manufacture a porcelain. At this time, B ₂ is added to improve sinterability.
It is common to add a sintering aid such as O ₃ , CaO, or SiO ₂ and then calcinate.

[0005]

In such a conventional method, in order to prevent the hydration of the magnesia raw material such as electro-melted magnesia or deadburn clinker-like magnesia particles, the secondary particles are suspended. The turbid solvent is limited to non-aqueous solvents such as alcohols. Therefore, the cost required for granulation is high, and since alcohols may pollute the environment, enormous cost is required for pollution control equipment, resulting in a high cost of the product.

[0006]

According to the present invention, when fine particles of electromelted or dead-burned magnesia are pulverized to produce primary particles, water is added to the raw material so that the surface of the primary particles is 5 to 15% by weight. % Of partial digestion, water is added to the obtained primary particles to form a slurry, and secondary particles formed by granulating and drying are molded and then fired. The gist is a method of manufacturing magnesia porcelain.

The present invention will be described in detail below.

In the present invention, first, electromelting or dead-burning (deadburn clinker-like) magnesia is preferably finely pulverized to a particle size of about 20 μm or less to obtain primary particles.

In the present invention, when crushing electromelted or dead-burned magnesia, water, preferably a concentration of 0.1 to
An aqueous solution containing 2.0% by weight of surfactant is added. By adding water, magnesia is digested and obtained 1.
A partial digestion layer is formed on the surface of the secondary particles. By forming this partially digested layer, the sinterability can be improved, but if the partially digested layer is too large, the sinterability will be adversely affected. Therefore, the addition amount of water or a surfactant-containing aqueous solution is
The partial digestion ratio of the obtained primary particles is 5 to 15% by weight.
The amount should be If the digestion ratio is less than 5% by weight, the digestion layer is not formed uniformly on the particle surface, and the effect of improving the sinterability is low. If it exceeds 15% by weight, the compact may crack during sintering, or Problems such as the density not increasing may occur.

The primary particles obtained by grinding are then granulated to form secondary particles. In the present invention, the primary particles are granulated with water or 0.1 to 2.0% by weight. It is suspended in an aqueous solution containing a surfactant having a concentration to form a slurry, which is granulated and dried.

As a granulating and drying method, it is advantageous to adopt a spray dry method using a spray dryer. Of course, in the present invention, the granulation method is not limited to the spray dry method, and the partial digestion and granulation described above can be performed by a fluidized bed method or the like.

By such granulation and drying, secondary particles which are spherical and preferably have a particle size of about 30 to 100 μm, which are rich in fluidity and excellent in moldability, are formed.

The surfactant used in the present invention is not particularly limited, but ether type, ester type and other nonionic surfactants are generally used.

The secondary particles obtained by the above-mentioned granulation method are molded, and the obtained molded body is fired to obtain a magnesia porcelain.

As the molding method, various conventionally used methods such as a slip casting method and a die pressing method can be adopted.

The obtained molded product is usually dried at 140
It is fired at a temperature of about 0 to 1700 ° C.

In the production of the porcelain of the present invention, a sintering aid may be used, but since the secondary particles used for molding in the present invention are extremely excellent in sinterability, a sintering aid or the like is particularly necessary. Not taken

[0018]

In the method of the present invention, since a non-aqueous solvent such as alcohol is not necessary when granulating magnesia, granulation can be performed at low cost and pollution prevention equipment is not necessary.
By partially digesting the surface of the primary particles of electromelted or dead-burned magnesia to a partial digestion amount of 5 to 15% by weight, secondary particles having good fluidity are granulated. The secondary particles have extremely excellent sinterability, the grain boundaries of the sintered particles are extremely small, and they sinter well. Although the details of this reason are not clear, the secondary particles are in a state in which the surface of the magnesia fine particles is uniformly coated with a magnesium hydroxide layer, which is completely different from the state in which magnesia is mixed with magnesium hydroxide. It is presumed that it is due to being in a state.

By using the secondary particles having excellent fluidity and sinterability, it is possible to easily and satisfactorily perform molding and sintering, and the obtained porcelain is a porcelain body which is dense and has extremely high strength. Become.

[0020]

EXAMPLES Examples will be described below.

In the following examples, "%" means "% by weight".

Examples 1 and 2, Comparative Example 1 0.5 parts by weight per 100 parts by weight of fused magnesia having a particle size of 0.5 mm.
The partial digestion amount of primary particles is 5% in an aqueous solution containing a surfactant (ester type nonionic surfactant) at a concentration of 5%.
(Example 1), 15% (Example 2), and 30% (Comparative Example 1) were added, and the mixture was pulverized by a media stirring type pulverizer to obtain electromelting magnesia primary particles having a particle size of 20 μm or less. Manufactured.

Next, 45 parts by weight of the aqueous surfactant solution was added to 100 parts by weight of the primary particles to form a slurry, and the slurry having a particle size of 2 as shown in Table 1 was prepared by a spray drying method.
Next granulated particles were obtained. The secondary particles were molded by a die pressing method and fired at the temperatures shown in Table 1 to manufacture magnesia porcelain.

Table 1 shows the density of the obtained magnesia porcelain.

[0025]

[Table 1]

Comparative Example 2 In Example 1, alcohol (ethyl alcohol) was used in place of the aqueous solution of the surfactant in the process of producing the primary particles, and 25 parts by weight of the alcohol was further added during spray drying. Other than the above, in the same manner, the particles were granulated to have an average particle size of 80 μm, molded, and fired. The measurement results of the density of the obtained porcelain are as shown in Table 2.

[0027]

[Table 2]

From Tables 1 and 2, it is clear that according to the method of the present invention, it is possible to obtain a highly dense porcelain, which enables extremely high density sintering.

In Examples 1 and 2, the fluidity of the material was extremely good, and the molding operation was extremely easy.

[0030]

As described above in detail, according to the method of manufacturing a magnesia ceramic of the present invention, a magnesia ceramic that is dense and has excellent characteristics such as strength can be easily manufactured.

Claims (1)

[Claims] 1. Electro-melting or dead-burning magnesia is pulverized to 1
In producing the secondary particles, water is added to the raw material to partially digest the surface of the primary particles to a partial digestion amount of 5 to 15% by weight, and water is added to the obtained primary particles to form a slurry form. The method for producing a magnesia porcelain is characterized in that the secondary particles formed by granulating and drying are shaped and then fired.