JPH04325604A - Production of porous sintered body - Google Patents

Abstract

PURPOSE:To mass-produce a porous sintered body of desired shape and uniformity pore distribution. CONSTITUTION:The mixture of a sintering material powder and a binder consisting essentially of an org. high molecular compd. is added with a foaming agent, expanded and injection-molded or extrusion-molded to obtain a porous formed body. The formed body is then degreased and sintered.

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 porous sintered body, which is excellent in freedom of shape, mass productivity, and uniformity of pores.

0002

[Prior Art] Porous sintered bodies are used as functional materials for various catalysts, filters, etc., and as structural materials for parts that require weight reduction and reduction of raw materials. It is becoming more important due to demands for multi-functionality and weight reduction.

Various proposals have been made as methods for producing porous sintered bodies, as shown below. (1) Raw material powder for sintering is mixed with various organic and inorganic powders as a pore-forming agent, compression molded, and then sintered. (2) As shown in Japanese Patent Application Laid-Open No. 55-125202 (title of invention: Method for manufacturing electrodes for alkaline batteries), raw material powder for sintering is kneaded with an organic binder to produce foamed resin and resin fibers. Coat it on the core, degrease it, and sinter it. (3) As shown in Japanese Patent Application Laid-Open No. 2-277703 (title of invention: Through-cell iron-based porous body and method for manufacturing the same), a kneading liquid of raw material powder for sintering and a binding liquid is mixed inside. It is poured into a mold filled with many organic polymer spheres, dried, degreased, and sintered.

0004

However, these methods cannot be said to be superior in terms of pore uniformity, mass productivity, and degree of freedom in product shape. Each method will be specifically described below.

[0005] The method (1) above has excellent mass productivity;
Although there is a certain degree of freedom in shape, the difference in density between the raw material powder for sintering and the pore-forming agent results in non-uniform molding within the mold, resulting in non-uniform pores. In some cases, they separate and molding becomes impossible.

Although method (2) above has excellent pore uniformity, it is poor in mass production, the shapes obtained are limited to simple ones, and the dimensional accuracy is also low, so it cannot be used for specific products. In order to obtain the desired shape, extensive post-processing of the sintered body is required.

The method (3) above also has excellent pore uniformity, but is inferior in mass production, and the detailed shape of the product depends on the size of the organic polymer spheres used, resulting in a limited degree of freedom in shape. Inferior.

The object of the present invention is to eliminate the above-mentioned drawbacks and
It is an object of the present invention to provide a method for manufacturing a porous sintered body that satisfies freedom of shape, mass productivity, and uniformity of pores at the same time.

[0009]

[Means for Solving the Problems] According to the present invention, a mixture containing a raw material powder for sintering and a binder containing an organic polymer compound as a main component is subjected to foam injection molding with the addition of a foaming agent. and foam extrusion molding to obtain a porous molded body; and degreasing and sintering the porous molded body. can get.

As a result of extensive research, the present inventors focused on foam molding used in plastic molding, and by applying this, they were able to solve the above-mentioned drawbacks.

[0011] Plastic foam molding usually involves heating and molding a plastic made by mixing polyethylene, polypropylene, EVA (ethylene-vinyl acetate copolymer), etc. with a foaming agent such as a carbonate or an azo compound. By this process, a molded body having pores is obtained. Foam molding can be applied to ordinary plastic molding methods such as injection molding, extrusion molding, and compression molding, so it has excellent mass productivity.
Injection molding and extrusion molding in particular have the advantage of providing a degree of freedom in shape that cannot be obtained with ordinary compression molding of powder, together with high dimensional accuracy. In addition, in injection molding and extrusion molding,
Since the raw material for molding and the blowing agent are uniformly kneaded by a screw, the resulting molded product has uniform pores.

0012

EXAMPLES The present invention will be explained below using examples. Ni-Zn ferrite pre-sintered powder with an average particle size of about 1 μm was prepared as a raw material powder for sintering, and 90.0% by weight of the Ni-Zn ferrite pre-sintered powder was mixed with 5.5% of low density polyethylene.
% by weight, 3.0% by weight of paraffin wax, and 1.5% by weight of dioctyl phthalate were mixed, kneaded, and crushed to obtain a molding raw material.

Next, 95% by weight of the raw material for molding was mixed with 5% by weight of azobisisobutyronitrile as a blowing agent, and injection molding was performed at a cylinder temperature of 160°C. A porous molded body was obtained. Next, this molded body was heated to 300° C. at a heating rate of 20° C./hr to perform degreasing. The obtained degreased body was heated to 1200℃
A sintered body was obtained by sintering in the air. The density of the obtained sintered body was 52%, and when the cross section was observed, the pores were uniformly dispersed.

[0014] As is clear from these results, by using the present invention, a method with excellent mass productivity and freedom of shape can be achieved.
It can be seen that a porous sintered body with uniform pores can be obtained.

It should be noted that the present invention is not limited to the above embodiments. For example, instead of Ni-Zn ferrite powder,
Other sinterable powders are applicable. Also, other blowing agents such as other azo compounds and carbonates can be used as long as they generate gas when heated.

[0016]

[Effects of the Invention] According to the present invention, since a plastic molding method can be applied, products with complex shapes can be manufactured with high dimensional accuracy, and the post-processing of sintered bodies that has been necessary until now can be reduced. . Moreover, it is excellent in mass production, so
The production according to the present invention has a large cost reduction effect compared to conventional methods and is extremely important industrially.

Claims (1)

[Claims] Claim 1: A mixture containing a raw material powder for sintering and a binder containing an organic polymer compound as a main component is subjected to one of foam injection molding and foam extrusion molding with the addition of a foaming agent. 1. A method for producing a sintered body, comprising the steps of: obtaining a porous molded body by molding the porous molded body; and degreasing and sintering the porous molded body.