JPH08164508A - Molding of ceramics - Google Patents

Abstract

PURPOSE: To prevent the generation of molding inferiority and to shorten a degreasing process by injecting a molding material prepared by mixing a binder to which a foaming agent is added with a ceramic powder into a mold and foaming the same under low pressure. CONSTITUTION: A molding material is injected into the cavity 2 formed to the fixed mold 1 of an injection mold constituted of the fixed mold 1 and a movable mold 5 through a runner 4 and a gate 3 to be foamed under low pressure. The molding material is prepared by mixing a binder to which a foaming agent is added with a ceramic powder and used in a pelletized state. Next, the molded object is degreased to be baked at predetermined temp. Since the foaming agent is added to the binder, the interior of the molded object becomes a porous state such that extremely fine cells are distributed and trouble such as a sink or a pore is not generated. Since the interior of the molded object is porous, the binder is well extracted and a degreasing process can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of molding ceramics, and more particularly to a method of molding ceramics used for electronic equipment, substrates of electronic equipment and the like.

[0002]

2. Description of the Related Art Conventionally, in order to mold ceramics into a predetermined shape, a high molecular substance such as acrylic or wax was mixed as a binder with ceramic powder and the mixture was injected into a mold. The injection molded green body is then degreased and fired.

[0003]

By the way, in the conventional injection molding method in which a polymer material is used as a binder, there is a problem that molding defects such as sink marks and pores occur in the thick portion of the green body (molded product). Had. As a countermeasure, increase the holding pressure, raise the mold temperature, the cylinder temperature,
Alternatively, the gates and runners are made thicker to increase the internal pressure, but there are limits, and this is not a reliable measure.

Also, the degreasing process of the green body requires at least 7 days for a product with a wall thickness of about 20 mm because the binder is not easily removed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramics molding method in which molding defects are not generated and the degreasing process can be shortened.

[0006]

In order to solve the above problems, in the method of molding ceramics according to the present invention, a molding material obtained by mixing a binder to which a foaming agent is added and ceramic powder is injected into a mold, and low pressure is applied. It is characterized by foaming.

[0007]

[Function] Since the foaming agent is added to the binder, the injected material foams in the mold, and the inside of the molded body becomes a porous state with minute cells distributed, eliminating the occurrence of sink marks and pores. It Further, since it is in a porous state, the binder can be easily removed, and the degreasing time can be shortened.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a ceramics molding method according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a main part of a mold for injection molding. 1 is a fixed-side mold, 5 is a movable-side mold, and a cavity 2 formed in the fixed-side mold 1.
Communicate with the material supply source through the gate 3 and the runner 4.

The molding material is BaTiO ₃ , CaTiO ₃ ,
A ceramic powder such as MgTiO ₃ mixed with a binder to which a foaming agent is added is pelletized. A polymer material such as polystyrene, polyethylene or wax is used as the binder, and azodicarbonamide or p, p-oxybenzenesulfonyl hydrazide is used as the foaming agent. Addition ratio of foaming agent to binder is about 2
wt%.

The above molding material is injected into the molds 1 and 5,
Low pressure foaming. An example of this molding condition is as follows. Cylinder temperature: 230 ° C Mold temperature: 60 ° C Injection pressure: 1448kg / cm ² Holding pressure: 271.5kg / cm ² Injection time: 4.72sec Cooling time: 89sec

Under the above molding conditions, the expansion ratio is about 1.1 times. The molded body (green body) is then degreased and fired at a predetermined temperature. The degreasing step is performed under normal pressure and normal temperature, but the temperature may be set arbitrarily between 0 and 400 ° C. Alternatively, it may be performed under vacuum. The degreasing step is 3 to 4 days, and 4 days is sufficient even for a thick molded body.

In this example, since the foaming agent was added to the binder, the inside of the molded body was in a porous state in which extremely small cells were distributed, and no sink mark or pore was found. Further, the reason that the degreasing process is short is because the inside is in a porous state, so that the binder can be easily removed.

The method of molding ceramics according to the present invention is not limited to the above-mentioned embodiment, but can be variously modified within the scope of the invention. Especially ceramic powder,
The binder and the type of the foaming agent can be arbitrarily combined.

[0014]

As is apparent from the above description, according to the present invention, since the foaming agent is added to the binder, the molding material injected into the mold has a porous structure in which extremely minute cells are distributed, and molding is performed. Defects such as sink marks and pores do not occur on the body, and the binder is removed well, so that the degreasing process can be shortened.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a mold used in a molding method according to the present invention.

[Explanation of symbols]

 1 ... Fixed side mold 2 ... Cavity 5 ... Movable side mold

Claims (1)

[Claims] 1. A method of molding ceramics, which comprises injecting into a mold a molding material obtained by mixing a binder to which a foaming agent has been added and ceramic powder, and foaming at low pressure.