JPH0570213A - Production of sintered body - Google Patents

Abstract

PURPOSE:To provide a method for efficiently producing a high quality sintered body almost free from pores and having high sintered density. CONSTITUTION:A molded body consisting of ceramics and/or a metal, an org. principal binder, an org. auxiliary binder, a solvent-extractable substance and a sublimable substance is dewaxed by solvent extraction, further dewaxed by heating 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 sintered body, and more specifically, it has a small number of pores and a high sintered density.
The present invention relates to a method for efficiently producing a high-quality sintered body. The sintered body obtained by the present invention is widely and suitably used in the fields of mechanical, electric and electronic devices.

[0002]

As one of the methods for producing a sintered body of ceramics or metal, it has plasticity by adding an organic binder main agent and an organic binder auxiliary agent to a raw material powder. There is a method of forming a kneaded clay, injection molding the same, further degreasing and firing. However, in this method, when preparing the kneaded clay having plasticity, a large amount of binder of 30 to 60% by volume relative to the raw material is required. When such a large amount of binder is mixed, cracks, voids, and
Crack expansion occurs. Such cracks in the degreasing process,
In order to remove the organic binder main agent and the organic binder auxiliary agent so that voids, cracks, expansion and the like do not occur, 300 to 4 at a small heating rate of about 5 ° C./hr.
Must be heated to 00 ° C. Therefore, in the conventional method, the degreasing process requires a long time, which causes a problem of low productivity and inefficiency.

In order to solve the above problems and shorten the time required for the degreasing process, an organic binder base agent, an organic binder auxiliary agent, and a solvent extraction substance are added to the powder raw material at the same time, and the degreasing process after molding is performed. In, to remove the solvent extraction substance using a solvent, to form fine pores in the surface layer of the molded body,
A method has also been proposed for facilitating removal of the organic binder main agent and the organic binder auxiliary agent during degreasing by heating.

However, in this method, if the temperature is raised at a high rate during heating and degreasing, the organic binder main agent and the organic binder auxiliary agent inside the molded body are not sufficiently discharged into the smooths, so cracks and voids are generated. ,crack,
Expansion etc. still occurs. Therefore, in this method, it is not possible to efficiently obtain a high-quality sintered body having a high sintering density without deforming, and to shorten the degreasing time sufficiently so that the improvement in productivity is achieved. There was a problem that I could not.

Further, Japanese Patent Application Laid-Open No. 62-3064 proposes a method of shortening the degreasing time by adding a sublimable substance. According to this method, by sublimation of the sublimable substance during heating degreasing, fine pores are formed in the surface layer of the molded body, so that it is possible to easily degrease the remaining organic binder main agent and organic binder auxiliary agent, It is said that the degreasing time can be shortened.

However, with this method, the degreasing time can be shortened, but the molded body is liable to lose its shape, and the high sintered density and strength desired in the fields of mechanical, electrical, and electronic equipment can be obtained. There is a problem in that it is not possible to efficiently obtain a high quality sintered body of the present invention. Therefore, there has been a demand for an efficient method for producing a sintered body that does not have the above-mentioned problems.

The present invention has been completed as a result of intensive research conducted by the inventors to solve the above problems. The object of the present invention is to add a solvent-extracting substance and a sublimable substance in addition to an organic binder main agent and an organic binder auxiliary agent to the raw material at the same time, so that the time of the degreasing step consisting of extraction and heating after molding. It is an object of the present invention to provide a manufacturing method capable of significantly shortening the time, maintaining the shape, and efficiently obtaining a high-quality sintered body with a high sintered density. Accordingly, the present invention provides a method suitable for producing a thick-walled molded product or a molded product having a complicated shape as a sintered body.

[0008]

[Means for Solving the Problems] A method for producing a sintered body according to the present invention for solving the above problems is a ceramics and / or metal, an organic binder main agent, an organic binder auxiliary agent, a solvent extraction substance, and sublimation. It is characterized in that a molded product obtained from the organic substance is subjected to solvent extraction degreasing and heat degreasing, and then sintered. Hereinafter, the present invention will be described in detail.

In the present invention, the molded body is obtained by molding kneaded clay.

The kneaded clay is prepared by adding ceramics and / or metal powder, an organic binder main agent, an organic binder auxiliary agent, a solvent extraction substance and a sublimable substance,
It can be prepared by kneading. As the ceramics, silica, feldspar, porcelain stone, lithium ore,
Silimanite, alumina, zirconia, silicon carbide, silicon nitride, non-plastic materials such as aluminum nitride and kaolin, plastic clay, frog clay, plastic materials such as fire clay, and the like, and as the metal,
Pure iron, stainless steel, titanium, etc. may be mentioned. In the present invention, these simple substance powders and composite powders can be used.

As the organic binder main agent, polyethylene, atactic polypropylene, polybutene, polystyrene, ethylene-vinyl acetate copolymer, cellulose acetate, polybutyl methacrylate, acrylic resin, polyvinyl alcohol, carboxymethyl cellulose, glucose, methyl cellulose, starch , Dextrin, molasses, gelatin, pulp waste liquid, peptone, polyvinyl ether, ethyl cellulose, acetyl cellulose, wax, liquid paraffin, heavy oil, machine oil, phenol resin, ethyl silicate and the like.
Usually, these can be used alone or as a mixture of two or more kinds. Of these, polyethylene, atactic polypropylene, polystyrene, ethylene-vinyl acetate copolymer, polybutyl cellulose, cellulose acetate, and wax are particularly preferable for preparing the kneaded clay in the present invention.

Examples of the organic binder aid include a lubricant and a plasticizer. Examples of the lubricant include higher fatty acids such as stearic acid, aluminum stearate, and metal salts of higher fatty acids such as magnesium stearate, higher fatty acid esters such as diglycol stearate, waxes, bread crumbs, and mineral oil. .. Among these, higher fatty acids are preferable, and stearic acid is particularly preferable. Examples of the plasticizer include fatty acid diesters such as diethyl phthalate, dibutyl phthalate, and dioctyl phthalate, and fatty acid monoesters. Of these, fatty acid diesters are preferable, and dibutyl phthalate is particularly preferable.

The solvent-extracting substance is easily dissolved in a solvent that does not dissolve the organic binder main agent, the organic binder auxiliary agent, and the sublimable substance, and further, the organic binder main agent, the organic binder auxiliary agent, and the sublimation agent. Examples thereof include polymer substances having many lipophilic groups that can be uniformly mixed with the organic substance and having a hydrophilic group such as a hydroxyl group that can be easily extracted with an extraction solvent.

Specific examples of the solvent extraction substance include higher alcohols having a molecular weight of 500 to 2,000 such as polyethylene glycol, ethylphenyl glycol, alkylallyl polyether alcohol and glycerin monooleate, or polyoxyethylene. Mention may be made of nonionic surfactants such as esters. Particularly preferred among these is polyethylene glycol having a molecular weight of about 1,000.

The sublimable substance is a substance which vaporizes at 400 ° C. or lower, such as camphor, perylene, naphthacene,
α-naphthol, tetraphenylmethane, acenaphthenequinone, 1,6-naphthalenediol, 2,6-naphthalenediol, 2,7-naphthalenediol, 1,4-
Naphthoquinone, 1-anthracenecarboxylic acid, 5,6-
Chrysenequinone, 2-methylanthracene, 3,4-dimethylbenzoic acid, 3,5-dimethylbenzoic acid, 2,6-
Dimethylanthracene, 2,3-dimethyl-p-benzoquinone, 2,5-dimethyl-p-benzoquinone, 2,6
-Dimethyl-p-benzoquinone, 1,2,5,8-tetrahydroxyanthracene, 4,5,7-hydroxy-
Sublimable cyclic hydrocarbons such as 2-methylanthraquinone and oxides thereof, or substances having a difference between the boiling point and the melting point of 250 ° C. or less and easily vaporized, for example,
Naphthalene, anthracene, phenanthrene, adamantane, trimethylene norbornane, cyclododecane, pyrene, chrysene, acenaphthene, acenaphthylene, fluorene, fluoranthene, β-naphthol, β-methyl-naphthalene, diphenylene oxide, tolan, tra
ns-stilbene, durene, pentamethylbenzene,
Mention may be made of cyclic hydrocarbons such as hexamethylbenzene and their oxides. These are single or 2
It can be used in a mixture of more than one kind. Of these, particularly preferred are adamantane, trimethylene norbornane, cyclododecane, naphthalene, anthracene,
They are cyclic hydrocarbons such as phenanthrene and camphor, and their oxides.

The proportion of the above-mentioned composition is such that ceramics and / or
Alternatively, the organic binder main agent is usually 2 to 8% by weight, preferably 3 to 5% by weight, and the organic binder auxiliary is usually 2 to 8% by weight, preferably 3 to the metal raw material powder.
˜5% by weight, solvent extracted substance is usually 2 to 16% by weight, preferably 6 to 10 and sublimable substance is usually 0.5 to 4.0% by weight, preferably 0.5 to 1.5% by weight. ..

As a compounding procedure, the organic binder main agent, the organic binder auxiliary agent, the solvent extractable substance and the sublimable substance may be thoroughly mixed, and then this and the raw material may be compounded. Alternatively, the raw material, the organic binder main agent, the organic binder auxiliary agent, the solvent extraction substance, and the sublimable substance may be mixed simultaneously or sequentially. The kneading can be carried out, for example, by using a kneading machine such as a ball mill, a plastomill, a pressure kneader, a heating kneader, or a cokneader which gives a shearing force at the same time as heating, and the kneading conditions are 0 to 160 ° C. 0.5 to 3 hours, preferably 1
It is 0.5 to 1 hour at 00 to 120 ° C.

The kneaded material obtained by kneading can be formed, for example, by a soft mud method, a semi-soft mud method, a plastic pressure molding method, a mechanical lathe method, a roller machine method, an extrusion molding method, a hard mud method, a hydrostatic pressing method. It can be molded into a desired shape by a rubber pressing method, a tamping method, a high temperature pressure molding method, an injection molding method, or the like. Among these various molding methods, the injection molding method is particularly preferable. This is because the kneaded clay for molding according to the present invention can favorably perform injection molding even when the pressure and temperature during injection molding are low, and shortens the time required for degreasing after injection molding. Because you can. To further explain the injection molding, the kneaded material is granulated by a roll, pelletized by a pelletizer, powdered by cold crushing by a kneader, or powdered by cold extruding and cutting into a sheet by a roll. To obtain pellets or powder as a molding material, and after these molding materials are subjected to a plunger type, a pre-plastic type or a screw in-line type injection molding machine, they are filled in a mold of a desired shape to obtain a molded body. .. The injection molding conditions are, for example, 80 to 205 ° C. and 300 to 1,500 kg / cm.
It can be performed under the conditions of ² .

The degreasing is composed of solvent extraction degreasing and heat degreasing. The solvent degreasing may be followed by heat degreasing, or conversely the solvent degreasing may be followed by solvent extraction degreasing.
Particularly preferably, the solvent extraction substance is extracted with a solvent, and solvent extraction degreasing for forming fine pores in the surface layer of the molded body is first performed, and then by heating, the sublimable substance is sublimated and discharged while expanding the fine pores. It is preferable to carry out heating and degreasing followed by removing the remaining organic binder main agent and binder auxiliary agent outside the molded body.

In the solvent extraction degreasing, the molded body is placed in a stationary or fluid solvent at room temperature, and optionally under heating,
It is performed by immersing for a certain period of time. The solvent is not particularly limited as long as it can dissolve the solvent extraction substance, and examples thereof include lower alcohols such as methanol, ethanol, propanol and butanol. In the solvent extraction degreasing in the present invention, methanol is particularly preferable as a solvent at room temperature for 3 to 5 hours. The heating degreasing is performed, for example, in the atmosphere at 20 to 3
It can be carried out by raising the temperature to 300 to 400 ° C. at a temperature raising rate of 00 ° C./hr and holding the temperature after raising the temperature for, for example, 0 to 12 hours. Such a rate of temperature increase is adopted as a suitable example when the heat energy is less than 20 ° C./hr.
The consumption is large, the productivity is low and it may not be efficient, and when it exceeds 300 ° C./hr, the degreasing rate is large, and the organic binder main agent and auxiliary agent do not come out smoothly from the fine pores of the molded body. Cracks, voids, cracks,
This is because expansion or the like may occur.

Sintering is carried out by pressureless sintering such as normal pressure sintering, reaction sintering, two-stage sintering or hot pressing, hot still water pressure sintering, gas pressure sintering, pressurized self-combustion sintering, ultrahigh pressure sintering and the like. It can be performed by a pressing method. In the present invention, among these, at 2,200 ° C. in the air or in an inert gas,
Sintering of a molded body by a normal pressure sintering method in which sintering is performed for several hours below is preferable, and in particular, at a temperature of 1,500 to 1,600 ° C. including 1,600 ° C. in the air as a suitable sintering temperature,
It is preferable to adopt a sintering condition of heating for 10 hours.

According to the above steps, the molding clay can be easily injection-molded without agglomeration, and the residual amount of the organic binder main agent and the binder auxiliary agent can be reduced and the degreasing time can be greatly reduced. Can be shortened,
After sintering, cracks, voids, cracks, deformations such as expansion do not occur, the surface is smooth, the sintered density and bending strength are large, and it has a dense and homogeneous microstructure with few pores, mechanical, electrical, It is possible to efficiently obtain a high-quality, thick-walled, complex-shaped sintered body, which is desired in the electronic device field.

[0023]

EXAMPLES Next, the present invention will be described more specifically by showing Examples and Comparative Examples of the present invention. (Example 1) As a raw material, zirconia (Daiichi Rare Element Chemical Industry Co., Ltd.)
Manufactured by: HSY-3.0B, specific surface area 5.1 m ² / g, average particle size 0.8 μm, using an ethylene-vinyl acetate copolymer (Tosoh Co., Ltd.) as a binder that constitutes an organic binder main agent. ): UE722) and amorphous polyolefin (Eastman Kodak: M5-)
F) is stearic acid as a lubricant constituting an organic binder aid, and dibutyl phthalate is selected as a plasticizer, and these are used as a solvent extraction substance.
Approximately 1,000 molecular weight of 10% by weight based on raw material powder
Polyethylene glycol as a sublimable substance,
2% by weight of adamantane was selected and used with respect to the raw material powder, these were added to the raw material at the same time as the above organic binder, and kneaded by a pressure kneader to prepare plastic clay.

Next, after supplying this clay to a plunger type injection molding machine, the injection temperature is 140 ° C. and the injection pressure is 660.
It was molded into a top shape under the condition of kg / cm ² · G.
Next, the molded body is dipped in methanol for 3 hours at room temperature.
The mixture was allowed to stand for a period of time, and the polyethylene glycol which was the solvent extraction substance in the molded body was solvent extracted.

Next, the molded body after solvent extraction is vacuum dried for 30 minutes, and then, in the air, from room temperature to 400 ° C.
Up to 250 ° C./hr, and kept at 400 ° C. for 2 hours. During this period, adamantane, which is a sublimable substance, first sublimes and is discharged while further expanding the micropores that form from the inside of the molded body formed during solvent extraction to the surface layer, and then expands the organic binder main agent and auxiliary agent. It was discharged through the fine pores to the outside of the molded body.

The molded body thus degreased by heating was heated to 1,500 ° C. in the air at a temperature rising rate of 100 ° C./hr.
The temperature was raised to 4 and the mixture was sintered at the same temperature for 4 hours. The sintered body thus obtained has no deformation such as cracks, voids, cracks and expansion, and has a sintered density of 6.03 g / c.
c, and the bending strength was 98 kg / mm ² , which was a high quality molded product.

Comparative Example 1 A molded body was manufactured in the same manner as in Example 1 except that adamantane which was a sublimable substance was not used.

Twenty injection-molded articles were subjected to solvent extraction treatment in the same manner as in the above-mentioned embodiment, and then vacuum dried to 250 ° C.
/ Hr. The temperature was raised to 400 ° C. at a heating rate of and held at 400 ° C. for 2 hours.

As a result, cracks were found in 18 of the 20 sintered bodies, the molded body had many voids, and the sintered body had a low sintered density.

(Comparative Example 2) As in Comparative Example 1, 2
After molding 0 moldings, solvent treatment and vacuum drying were performed, and 200 ° C./hr. The temperature was raised up to 400 ° C. at a heating rate of and held at 400 ° C. for 2 hours.

As a result, cracks were found in two of the 20 sintered bodies. In the two sintered bodies,
The sintered body had many pores and had low sintered density and surface smoothness.

(Comparative Example 3) After molding was performed using the same raw material composition as in Example 1 except that the solvent extraction substance polyethylene glycol was not added, no solvent extraction treatment was carried out and the same procedure as in Example 1 was performed. Similarly, heat degreasing treatment was performed. As a result, the obtained molded product had a shape loss at its corners.

[0033]

EFFECTS OF THE INVENTION According to the method for producing a sintered body according to the present invention, degreasing can be reasonably performed at a high temperature rising rate, and the organic binder main agent and binder auxiliary agent can be sufficiently degreased in a short time. It has a good quality, is free from cracks, voids, cracks, expansion, etc. after firing, has a smooth surface, has excellent dimensional accuracy, and is a dense and homogeneous micropore with few holes, which is desired in the fields of machinery, electrical and electronic equipment. Have an organization,
It is possible to efficiently obtain a high quality sintered body having a high sintered density and bending strength.

Claims (1)

[Claims] 1. A molded body obtained from ceramics and / or metal, an organic binder main agent, an organic binder auxiliary agent, a solvent extraction substance and a sublimable substance is subjected to solvent extraction degreasing and heat degreasing, followed by sintering. A method for producing a sintered body, comprising: