JPH0772100B2 - Powder molding composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a powder molding composition, and more specifically, it facilitates degreasing after mixing ceramic or metal powder with an organic material and molding. Related to organic materials.

[Prior Art] A ceramic compact is obtained by compacting a raw material powder and then sintering it. However, since it is not easy to form a ceramic powder alone, a composition obtained by adding an organic material to a ceramic powder is usually compacted. After that, organic matter is removed from the molded body (referred to as degreasing), and then sintered. However, when it is difficult to mold the powder-solvent system, a resin material as a binder, a lubricant, a plasticizer, etc. are hot mixed and molded. The present invention relates to such an organic material in the case of being hot-formed, but the powder is not limited to ceramics and is applicable to metal.

Examples of the organic material used in such hot molding, particularly the binder, include, for example, polyethylene, polypropylene, polyvinyl acetate, and polybutyl methacrylate in the extrusion molding method, and atactic polypropylene, polyethylene, polystyrene in the injection molding method. , Ethylene-vinyl acetate copolymer, polybutene, paraffin, stearic acid, dibutyl phthalate and the like.

[Problems to be solved by the invention]

However, an organic material (usually a thermoplastic resin) used for hot molding as described above is generally a component having a high thermal decomposition temperature, and the maximum temperature required for degreasing is as high as 450 to 600 ° C. Therefore, the temperature increase rate of degreasing may depend on the wall thickness of the molded product, but since it is generally 1 to 10 ° C / H, it takes a long time for degreasing and there is a problem of poor economic efficiency. .

Further, such a conventional organic material is not completely decomposed by heat during degreasing and does not disappear, and only a small amount (about 1 to 5%) of carbon content remains, which causes the following problems.

In oxide ceramics such as Al ₂ O ₃ , CO gas is generated by the reduction reaction and bubbles are generated in the sintered body.

In Si ₃ N ₄ to which oxides such as Al ₂ O ₃ , MgO, MgAl ₂ O ₄ and Y ₂ O ₃ are added as a sintering aid, bubbles are generated in the sintered body during the sintering of the compact.

In the case of a metal powder compact such as iron powder, the mechanical properties of the sintered compact tend to become brittle (toughness decreases) due to the effect of residual carbon.

[Means for solving problems]

The present inventor has found that it is possible with a specific organic material in the course of intensive research for the purpose of reducing the degreasing temperature to 350 ° C. or lower in order to solve the problems of the above-described conventional techniques, The present invention has been completed.

That is, the present invention comprises a ceramic or metal powder and an organic substance which is solid at room temperature, the organic substance comprises dimethyl terephthalate, paraffin and dicyclohexyl phthalate, and the weight ratio of paraffin to dicyclohexyl phthalate is 1 to 4 And a weight ratio of dimethyl terephthalate to a mixture of paraffin and dicyclohexyl phthalate is 0.01 to 0.2.

In the above composition, dicyclohexyl phthalate is responsible for the shape retention of the molded product, and paraffin is responsible for the fluidity of the molding material (composition). Therefore, if the ratio of paraffin / dicyclohexyl phthalate is too small, the fluidity becomes poor and molding of a complicated shape becomes difficult. On the other hand, if the ratio is too large, the molded body becomes too soft and easily deforms. Dimethyl terephthalate has a function of facilitating degreasing. This is because dimethyl terephthalate is easily volatilized from the molded body, the total amount of the dimethyl terephthalate disappears by 200 ° C, a hole is formed in the molded body, and then a path for gas emitted from paraffin and dicyclohexyl phthalate is formed to facilitate degreasing. Because.

The powder molding composition according to the present invention is typically prepared by heating and kneading a ceramic or metal powder and an organic material and then pelletizing the resulting pellet, and extruding the obtained pellet by a method similar to that of plastic extrusion or injection molding. Alternatively, injection molding is performed. The primary molded body thus obtained can be degreased at a temperature of 350 ° C. or lower.

〔Example〕

A kneaded material A was prepared by adding 15.8 wt% of the resin composition shown in Table 1 to 84.2 wt% of iron powder (average particle size of about 0.6 μm). A kneaded material B was prepared by adding 16.2 wt% of the resin composition shown in Table 1 to 83.8 wt% of silicon nitride powder (average particle size: about 0.9 μm).

The above kneaded materials A and B are each pelletized, and the injection temperature is 135 ° C.
By injection molding to obtain a molded body of φ20 × length 150 (mm ² ).

When the weight ratio was less than 1, the fluidity was deteriorated, and significant defective filling appeared at the tip of the rod-shaped sample (on the side opposite to the sprue). On the other hand, when the ratio is larger than 4, the molded body is soft and the rod-shaped test piece is liable to be flexibly deformed during demolding.

The samples No. 2 to No. 8 in Table 1 had no problem as the molded body.

Next, the molded body was embedded in alumina sphere powder having a diameter of about 0.2 mm, and the iron powder was degreased in an atmosphere of argon and the silicon nitride in a nitrogen atmosphere at a maximum temperature of 350 ° C. for 66 hours.

When the weight ratio of was less than 0.01, swelling, peeling and cracking were likely to occur in the degreased body, and when it was more than 0.2, swelling was likely to occur mainly. The above ratio is 0.01 to 0.2
A good degreased body was obtained within the range.

The amount of carbon in the defatted body was quantified, but there was no problem at the residual carbon level of about 10 ppm.

[Effects of the Invention] According to the present invention, the time required for degreasing can be performed because degreasing of a primary compact obtained by kneading and molding a ceramic or metal powder with an organic material while hot can be performed at about 350 ° C or less. Can be significantly shortened. Further, since the amount of residual carbon in the degreased body is reduced, the inconveniences such as the generation of bubbles during firing due to the presence of residual carbon and the embrittlement of the sintered body are eliminated.

Claims (1)

[Claims] 1. A ceramic or metal powder and an organic substance which is solid at room temperature, and the organic substance comprises dimethyl terephthalate, paraffin and dicyclohexyl phthalate, and the paraffin and dicyclohexyl phthalate have a weight ratio of 1 to 4. A powder molding composition, characterized in that the weight ratio of dimethyl terephthalate to the mixture of paraffin and dicyclohexyl phthalate is 0.01 to 0.2.