JP3362465B2 - Manufacturing method of sintered member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is de-molded body obtained by injection molding
The present invention relates to a method for manufacturing a sintered member to be greased and fired .

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for products having complicated shapes made of metal or ceramic, and attention has been paid to injection molding for obtaining products of near net shape. This injection molding method has been put to practical use because of its good dimensional accuracy and high molding productivity. However, in this injection molding method, it is necessary to add a large amount of a thermoplastic resin in order to impart plasticity to the raw material powder during molding. Therefore, the injection-molded article is generally degreased and fired at a very slow heating rate in order to remove the thermoplastic resin. This thermoplastic resin is used to bond the raw material powders to each other to give molding strength, and is generally called a binder because of the bonding action.
Hereinafter, also in the present invention, it is called a binder. The rate of temperature rise in the degreasing step of the injection-molded article is described in JP-A-58-9917.
1, JP-A-59-121150, JP-A-59-1955
77, etc., it requires a degreasing period of 2 to 7 days since it is moderate at 3 to 10 ° C./hour. Also, JP-A-58-99171 and JP-A-63-13
No. 9043, a method of shortening the degreasing time by using several kinds of binders in consideration of the decomposition characteristics of the binder upon heating, and Japanese Unexamined Patent Publication No.
As disclosed in 338155, a method of adding a low molecular weight organic compound to a binder has been adopted.

[0003] JP-A-57-17468, JP-A-67-14
4-68402, a method of degreasing in an atmosphere of a pressurized inert gas or in a vacuum as disclosed in JP-A-2-111703 or an organic solvent as disclosed in JP-A-55-114524. A method for eluting and removing a part of the binder has also been developed.

[0004]

In the process of removing a thermoplastic resin from an injection-molded article, efforts have been made to shorten the degreasing time by the above-mentioned prior art, but it has not been sufficient yet. In addition, a special degreasing furnace or expensive inert gas or organic solvent must be used in the removal step. An object of the present invention is to provide a method for manufacturing a sintered member that can be degreased inexpensively without using special equipment in a short time in a degreasing step of an injection molded body.

[0005]

SUMMARY OF THE INVENTION The present invention provides a method for spraying a raw material comprising a ceramic or metal raw material powder and a thermoplastic resin.
Out-molding to obtain a molded body, including alkali ions
By immersing the compact in an aqueous solution, the heat
A step of decomposing and removing a plastic resin to obtain a degreased body;
Baking the body; and
The present invention relates to a method for manufacturing a material .

Preferably, the ceramic or metal raw material powder has a particle size of 0.1 to 30 μm.

Preferably, the thermoplastic resin is at least one of acrylic resin, polyethylene, polypropylene, ethylene vinyl acetate, polyethylene wax, and derivatives or polymers thereof.

[0008]

The alkali ion is preferably at least one of lithium, sodium, potassium, rubidium and cesium.

[0010]

[0011]

[0012]

[Function] A raw material composed of a ceramic or metal raw material powder and a thermoplastic resin is injection-molded, and the obtained molded body is subjected to aluminum molding.
By immersing in an aqueous solution containing potassium ions,
The resin can be decomposed and removed, and degreasing can be performed at a lower cost than conventional degreasing methods using a special degreasing furnace, an expensive inert gas, or an organic solvent.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below. (Example 1) Beta alumina (Na ₂ O · 11Al ₂ O)
₃ ) 100 parts by weight and 12 parts by weight of ethyl acrylate are kneaded by a pressure kneader at 100 ° C. for 30 minutes. The kneaded product was granulated with a pelletizer to obtain a raw material (compound) for injection molding. Next, this compound is molded by an injection molding machine under molding conditions of an injection temperature of 150 ° C., a mold temperature of 30 ° C., an injection pressure of 1000 kg / cm ² , a holding pressure of 800 kg / cm ² and a molding time of 30 seconds to obtain a molded body. Was.
The molded body was immersed in a 10% aqueous solution of sodium orthosilicate kept at 50 ° C. for 5 hours. Then, the substrate was sufficiently washed with water to remove the hydrolyzed binder and silicate ions and sodium ions adsorbed on the molded body. After drying the degreased body, the weight was measured and the binder removal rate was calculated from the weight loss amount. As a result, it was found that 40% of the binder had been removed. The degreased body thus obtained is placed in air for 1 hour.
The residual binder was removed by heating to 500 ° C. at a heating rate of 00 ° C./hour. Subsequently, the degreased body was heated to 300 ° C /
The temperature was raised to 1400 ° C. at a temperature rising rate over time to obtain a sintered body. Cracks, blisters,
There was no deformation and the sintered density was 97% of the theoretical density.

As described above, it has been found that degreasing and firing can be performed in a short time without using special equipment, as compared with the conventional example.

Example 2 Alpha alumina (Al ₂ O)
₃ ) 100 parts by weight, 14 parts by weight of butyl acrylate and 2 parts by weight of ethylene acetate vinyl were mixed with a pressure kneader to obtain 10 parts by weight.
The mixture was kneaded at 0 ° C for 30 minutes. The kneaded product was granulated with a pelletizer to obtain a compound. Next, the compound was injected at an injection temperature of 150 ° C. and a mold temperature of 3 using an injection molding machine.
0 ° C, injection pressure 1000kg / cm ² , holding pressure 800k
Molding was performed under molding conditions of g / cm ² and a molding time of 30 seconds to obtain a molded body. The molded body was immersed in a 10% aqueous solution of sodium orthosilicate kept at 50 ° C. for 5 hours. Then, the substrate was sufficiently washed with water to remove the hydrolyzed binder and silicate ions and sodium ions adsorbed on the molded body. After the degreased body was dried, the weight was measured and the binder removal rate was calculated from the weight loss amount. As a result, it was found that 30% of the binder had been removed. The degreased body thus obtained was heated to 500 ° C. in air at a rate of 100 ° C./hour to remove the residual binder. Subsequently, the degreased body was heated to 1650 ° C. at a rate of 300 ° C./hour to obtain a sintered body. The sintered body thus obtained had no cracks, blisters, deformation, etc., and the sintered density was 99% of the theoretical density. In this example, ethylene vinyl acetate which is not hydrolyzed was used in combination to maintain the molding strength after degreasing.

As described above, it has been found that degreasing and firing can be performed in a short time without using special equipment, as compared with the conventional example.

Example 3 Barium titanate (BaO.
100 parts by weight of TiO ₂ ) and 15 parts by weight of butyl methacrylate were kneaded by a pressure kneader at 130 ° C. for 30 minutes. The kneaded product was granulated with a pelletizer to obtain a compound. Next, the compound was injected with an injection molding machine at an injection temperature of 170 ° C., a mold temperature of 30 ° C., and an injection pressure of 1000 k.
The molding was performed under molding conditions of g / cm ^{2 ,} holding pressure of 1000 kg / cm ² and molding time of 30 seconds to obtain a molded body. This compact was immersed in a 10% aqueous solution of potassium orthosilicate kept at 50 ° C. for 5 hours. Then, the substrate was sufficiently washed with water to remove the hydrolyzed binder and silicate ions and potassium ions adsorbed on the molded body. After drying the degreased body, the weight was measured and the binder removal rate was calculated from the weight loss amount. As a result, it was found that 70% of the binder had been removed. The degreased body thus obtained was heated to 400 ° C. at a heating rate of 100 ° C./hour in air to remove the residual binder. Subsequently, the degreased body was heated to 1350 ° C. at a rate of 300 ° C./hour to obtain a sintered body. The sintered body thus obtained had no cracks, blisters, deformation, etc., and the sintered density was 97% of the theoretical density.

Example 4 100 parts by weight of tungsten carbide-cobalt-based metal (WC-Co) and 30 parts by weight of butyl methacrylate were pressed at 130 ° C. by a pressure kneader.
Kneaded for 0 minutes. The kneaded product was granulated with a pelletizer to obtain a compound. Next, the compound was injected with an injection molding machine at an injection temperature of 170 ° C., a mold temperature of 30 ° C., an injection pressure of 900 kg / cm ² , a holding pressure of 900 kg / cm ² ,
Molding was performed under molding conditions of a molding time of 30 seconds to obtain a molded body. This compact was immersed in a 10% aqueous solution of potassium orthosilicate kept at 50 ° C. for 5 hours. Then, the substrate was sufficiently washed with water to remove the hydrolyzed binder and silicate ions and potassium ions adsorbed on the molded body. After drying the degreased body, the weight was measured and the binder removal rate was calculated from the weight loss amount. As a result, it was found that 50% of the binder had been removed. The degreased body thus obtained was heated to 400 ° C. at a rate of 100 ° C./hour in an inert gas to remove the residual binder. Subsequently, the degreased body was
The temperature was raised to 1350 ° C. at a temperature rising rate of ゜ C / hour to obtain a sintered body. The sintered body thus obtained had no cracks, blisters, deformation, etc., and the sintered density was 98% of the theoretical density.

The ceramic or metal raw material applicable to the present invention is not limited to the above embodiments, but includes barium titanate, zirconium titanate, ferrite, and the like.
Oxide ceramics such as alumina, zirconia, magnesia, beryllia, mullite, and forsterei, tungsten carbide, silicon carbide, boron nitride,
Non-oxide ceramics such as aluminum nitride and silicon nitride, iron, copper, tin, zinc, chromium, manganese, nickel, molybdenum, tungsten, titanium, aluminum, silicon, beryllium, germanium, stainless steel alloy, titanium alloy, The present invention may be applied to any powder material such as a simple metal such as a zirconium alloy or a metal alloy. The thermoplastic resin constituting the raw material for molding may be anything that can be hydrolyzed, and may be any acrylic resin, such as methyl acrylate, ethyl acrylate,
Propyl acrylate, butyl acrylate, ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, phenyl acrylate
, Methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, ethyl hexyl methacrylate, lauryl methacrylate, stearyl methacrylate, using at least one material selected from such as cyclohexyl methacrylate Further, in order to secure the strength of the molded body after the acrylic resin is decomposed and removed, the thermoplastic resin may contain general-purpose thermoplastic resins such as polyethylene, polypropylene, polystyrene, and ethylene vinyl acetate. If necessary, a wax, stearic acid, or the like may be used as a lubricant so that the molded product can be easily removed from the mold. The mixing ratio between the above ceramic or metal material and the thermoplastic resin is such that the thermoplastic resin in the mixture is 20 to 20% by volume percentage.
It is preferable that the mixing ratio includes 50%.

Further, the aqueous solution for decomposing and removing the above-mentioned thermoplastic resin includes an alkali ion containing at least one of sodium, potassium, rubidium and cesium, for example, sodium orthosilicate, potassium orthosilicate, sodium hydroxide, potassium hydroxide. Can be used.

[0021]

According to the present invention, a molded product obtained by injection molding a raw material comprising a ceramic or metal raw material powder and a thermoplastic resin.
Is immersed in an aqueous solution containing alkali ions,
The plastic resin can be easily removed from the molded body.
Such as ceramic or metal parts by the result injection molding
In the case of applying injection molding to the production of complex shaped products, degreasing can be performed at a lower cost than in the conventional degreasing method using a special degreasing furnace, expensive inert gas, or organic solvent, etc. , Shortening the production period and reducing the manufacturing cost.

Claims (3)

(57) [Claims] 1. A step of obtaining a molded body by injection molding a raw material comprising a ceramic or metal raw material powder and a thermoplastic resin.
And immersing the molded body in an aqueous solution containing alkali ions
By decomposing and removing the thermoplastic resin, degreasing
Obtaining a body, and baking the degreased body.
A method for producing a sintered member . 2. The thermoplastic resin is at least one of acrylic resin, polyethylene, polypropylene, ethylene vinyl acetate, polyethylene wax and derivatives or polymers thereof.
2. The method for producing a sintered member according to 1 . Wherein the alkali ions are lithium, sodium, potassium, rubidium, method for producing a sintered member according to claim 1 or 2, characterized in that at least one of cesium.