JPH07165460A - Production of formed magnesia - Google Patents

Abstract

PURPOSE:To produce a defect-free homogeneous formed article of magnesia by extrusion molding. CONSTITUTION:Magnesia powder is mixed with a sintering assistant and a deflocculating agent in wet state and dried. The obtained powder is mixed with a forming binder dissolved in an organic solvent and liquid paraffin and the mixture is extrusion-molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a magnesia compact by an extrusion molding method.

[0002]

2. Description of the Related Art High-purity magnesia sintered bodies have excellent heat resistance in an oxidizing atmosphere and excellent corrosion resistance to lead oxide and alkali, so that they can be used for firing electronic ceramic materials such as PZT and β-alumina. There are applications such as containers for thermocouples and protective tubes for thermocouples. Conventionally, containers used for such applications are made by casting. In this cast molding, a binder is added in order to prevent cracks from occurring in the molded body, but since the binder dissolves in the solvent and increases the viscosity of the solvent, the casting speed becomes slow and the molding time becomes long. was there. In addition, the cast molding is not suitable for mass production because only one molded body can be produced. On the other hand, the extrusion molding method has been practically used as a method suitable for mass production because continuous production is possible, but in the conventional method, defects remain in the molded body, so that a uniform molded body without defects is formed. Was difficult to obtain.

[0003]

The object of the present invention is to solve the above problems,
It is intended to provide a method capable of producing a defect-free homogeneous molded body by an extrusion molding method.

[0004]

According to the present invention, a powder obtained by wet-mixing a magnesia powder, a sintering aid and a deflocculant, and then drying the powder, and a molding binder dissolved in an organic solvent, and The present invention relates to a method for producing a magnesia molded body, which comprises adding and mixing liquid paraffin, and then extruding.

In the present invention, first, magnesia powder,
The sintering aid and the deflocculant are wet mixed and then dried to obtain a mixed powder. The magnesia powder has a BET specific surface area of 5 to 170 m ² / g (specific surface area diameter of 0.01 to 0.2 μm).
m), high-purity ultrafine single crystal magnesium oxide having a purity of 99.9% or more is preferable. Such high-purity ultrafine single crystal magnesium oxide can be synthesized by the method disclosed in Japanese Examined Patent Publication No. 2-289, that is, a method of oxidizing magnesium vapor and an oxygen-containing gas in a turbulent diffusion state. It is possible to produce magnesium oxide having a BET specific surface area of more than 170 m ² / g, and it is also useful in the present invention, but the production cost is extremely high, and it is difficult to handle ordinary powders. Therefore, the practicality is low at present. On the other hand, if the specific surface area is less than 5 m ² / g, the sintering activity of the powder is lowered, and a sintered body having a high density cannot be obtained, which is not preferable. ZrO ₂ , Y ₂ O ₃ or the like is used as the sintering aid.

The addition ratio of the sintering aid to the magnesia powder is 0.05 to 100 parts by weight of the magnesia powder.
0.5 part by weight and a deflocculant 0.5 to 5 parts by weight are preferred. The wet mixing is performed by adding an organic solvent such as alcohol or toluene to the magnesia powder, the sintering aid and the deflocculant, and using a ball mill or the like. Then, the solvent is removed by drying, and the mixture is crushed and sized into appropriate granules to obtain a mixed powder.

A molding binder dissolved in an organic solvent such as alcohol or toluene and liquid paraffin are added to the obtained mixed powder and mixed. The molding binder is not particularly limited, and a binder soluble in an organic solvent is used. The addition ratio of the molding binder is 0.1 to 5 parts by weight, especially 0.1% by weight, relative to 100 parts by weight of magnesia.
3 to 2 parts by weight is preferable. The addition amount and ratio of the organic solvent and the liquid paraffin may be appropriately selected so that a homogeneous molded body can be obtained. Usually, 5 to 20 parts by weight of the organic solvent and 5 to 5 parts of the liquid paraffin are added to 100 parts by weight of magnesia.
Used in the range of 20 parts by weight. In particular, the addition of liquid paraffin improves the fluidity of the powder during the molding process. The resulting mixture is then extruded, dried to remove the solvent, debindered and then sintered. Sintering is performed in an oxidizing atmosphere, for example, in air at 1500 to 18
It is carried out at a temperature of 00 ° C.

[0008]

EXAMPLES The present invention will be described more concretely with reference to the following examples. Examples 1 to 4 and Comparative Example 1 To 300 g of toluene, 400 g of high-purity ultrafine single-crystal magnesium oxide (specific surface area diameter 0.2 μm), sintering aid 0.
After adding 4 g and a deflocculant 8 g and performing ball mill mixing for 7 hours, it dried and the solvent was removed and it grind | pulverized and the mixed powder was obtained. A molding binder (Bind Serum SA541 (resin content 40%); manufactured by Mitsui Toatsu Chemicals, Inc.), toluene and liquid paraffin were added to the obtained mixed powder in the proportions shown in Table 1 and mixed. The resulting mixture is then
Extrusion speed 5 mm / min, extrusion ratio 6.3, outer diameter 10
It was extruded into a pipe shape with φ and an inner diameter of 6φ. The obtained molded product is dried to remove the solvent, and then in air at 0.5 ° C /
The binder was removed while the temperature was raised at a rate of min, followed by sintering at a temperature of 1600 ° C. or higher. The results of measuring the density of the molded body and the density of the sintered body after drying are shown in Table 2.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

According to the manufacturing method of the present invention, it is possible to produce a large amount of defect-free and homogeneous moldings by the extrusion molding method.

Claims (1)

[Claims] 1. A magnesia powder, a sintering aid, and a deflocculant are wet-mixed and then dried, and a molding binder and liquid paraffin dissolved in an organic solvent are added to and mixed with the powder. A method for producing a magnesia molded body, which comprises performing extrusion molding.