JP2001348602A - Composition as powder material for sintering and method for producing the sintered product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintered product of metal powder, or the like, in a short time without causing physical defects in the process of compacting, degreasing, sintering, or the like, for obtaining the same. SOLUTION: The powder sintered product is obtained by using a composition obtained by blending powder for sintering composed of 100 pts.wt. in organic powder or metal powder or their mixture and 5 to 25 pts.wt. of an organic binder containing 10 to 50 vol.% of a graft polymer in which the main chain is composed of a compound selected from polypropylene, an ethylene-vinyl acetate copolymer and an ethylene-ethyl acrylate copolymer, and the side chains are composed of a compound selected from polystyrene, polymethylmethacrylate and polybutylmethacrylate and 30 to 70 vol.% of at least one kind of organic compound whose the melting points is 40 to 100 deg.C, and melting viscosity at 120 deg.C is <=1,000 mPa.s, in total as essential components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition as a powder sintering material comprising a binder and a sinterable powder such as an inorganic powder such as various ceramics or a metal powder, and a composition using the composition. The present invention relates to a method for manufacturing a sintered product.

[0002]

2. Description of the Related Art As is well known, an injection molding method is used to obtain a product having a complicated shape by using a sinterable powder. In the practice of the injection molding method, various methods are used to impart fluidity to the powder. And an organic compound, particularly a thermoplastic resin, is added and kneaded with heat. Thus, a sintered product can be obtained by injection-molding the kneaded material as a raw material for molding and degreased and sintered the molded product.

For example, in an injection molding composition using a metal powder, conventionally, as a high molecular weight organic compound, polyethylene, polypropylene, methacrylate copolymer,
And a binder comprising an ethylene-vinyl acetate copolymer and paraffin wax, carnauba wax or the like as a low molecular weight compound (JP-A-59-22).
No. 93403), a binder comprising polystyrene, polybutyl methacrylate and an ethylene-vinyl acetate copolymer as essential components (Japanese Patent Publication No. Hei 7-68567).
No.).

However, when these organic compounds are used as a binder, if the temperature rise rate is high, when the binder is melted and thermally decomposed, the molded product tends to swell, crack and deform, and the organic binder is completely removed. In order to remove it, heating at a high temperature for a long time is required.

[0005]

SUMMARY OF THE INVENTION The inventor of the present invention has made intensive studies to eliminate the above-mentioned physical defects that occur during the degreasing and sintering of a compact and to shorten the heat treatment time.
The invention of the following molding composition and a method for producing a sintered body using the same have been achieved.

[0006]

According to the present invention, there is provided an A.I. B. 100 parts by weight of a sintering powder composed of an inorganic powder, a metal powder, or a mixture thereof; The main chain is composed of a compound selected from polypropylene, ethylene-vinyl acetate copolymer and ethylene-ethyl acrylate copolymer, and the side chain is composed of a compound selected from polystyrene, polymethyl methacrylate, or polybutyl methacrylate.
vol% of a graft polymer (b1) and at least one organic compound having a melting point of 40 ° C. to 100 ° C. and a melt viscosity at 120 ° C. of 1000 mPa · s or less, having a total amount of 30 to 70 vol% (B
A composition as a material for powder sintering, characterized by comprising 5 to 25 parts by weight of an organic binder containing 2) as an essential component.

The above composition is molded, and the molded body is put into a heat treatment furnace and degreased and sintered to form a sintered product. In the composition, as for the mixing ratio of the sintering powder A and the organic binder B, if the amount of the binder is less than the minimum value of 5 parts by weight based on 100 parts by weight of the sintering powder, Fluidity is significantly reduced, making molding difficult. When the amount of the binder exceeds the maximum value of 25 parts by weight, it is observed after degreasing that cracks and internal air bubbles are apt to be generated at the time of molding, and that gas generated by decomposition of the binder at the time of degreasing causes cracks and swelling.

In the organic binder of the above B, 10 to 10
The graft polymerization polymer (or “graft copolymer”) occupying 50 vol% increases the strength of the molded article, prevents deformation during degreasing, and is not necessary because it does not remain in the sintering step after degreasing. It is an element that cannot be done. Therefore, when the graft polymer is 10 vol.
%, The strength of the molded body is low, and the deformation at the time of degreasing increases. Conversely, if it exceeds 50 vol%, the temperature during molding will increase, and molding defects will easily occur, and cracking and swelling will occur due to rapid thermal decomposition during degreasing.

The main chain component of the graft polymer is composed of polyolefin polypropylene, ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer, so that it has high compatibility with waxes. In the present invention, the best ratio of the main chain and the side chain of the graft polymerized polymer is 50 to 90 of the main chain compound.
vol%, and 10 to 50 vol% of the side chain compound.

That is, when the main chain component of the graft polymer is less than 50 vol% and the side chain component is more than 50 vol%, compatibility with waxes is lost and the molded article becomes brittle. Conversely, if the main chain component exceeds 90 vol% and the side chain component is less than 10 vol%, the compatible waxes are less liable to volatilize during the heating and heating process, and swelling and cracking are likely to occur in the molded product.

[0011] In the present invention, 30 to 7 in the organic binder
It is an organic compound occupying 0 vol%, and has a melting point of 40 ° C.
Melt viscosity at 120 ° C at 100 ° C is 1000 mP
As at least one kind of organic compound having a · S or less, any one or more of paraffin wax, carnauba wax, urethanized wax, hardened castor oil, fatty acid ester, and phthalic acid ester are employed. Among the characteristic conditions of this organic compound, the melting point is 40%.
If the temperature is lower than 100 ° C., these compounds are separated at the time of molding, causing problems to the molded body. If the temperature is higher than 100 ° C., the molding temperature is increased and the solidification upon cooling is increased, so that defects such as bubbles are likely to occur in the molded body. The melt viscosity at 120 ° C. is 10
If it exceeds 00 mPa · S, these organic compounds cannot be easily decomposed at the time of degreasing, and swelling and cracking tend to occur during degreasing.

Regarding the occupancy rate of these organic compounds in the binder, if it is less than 30 vol%, the melt viscosity at the time of molding rises and welds and cracks are liable to be formed in the molded article. If it exceeds 70 vol%, deformation occurs during degreasing. It will be easier.

The components of the organic binder of the present invention are preferably set as described above. However, in order to increase the strength of the molded product and the fluidity during molding while maintaining the range of the amount of each component, the organic binder is desirably used. A thermoplastic resin such as amorphous polyolefin, polyvinyl butyral, or polybutyl methacrylate can be added accordingly.

As the sintering powder of the present invention, powders of stainless steel, iron-based materials, titanium, copper, nickel and the like can be used for metals, and oxide ceramics, nitride ceramics or carbide ceramics can be used for inorganic materials. . The average particle size of these powders is desirably 0.1 to 30 μm. If the average particle size of the powder is 0.1 μm or less, the amount of binder necessary for molding increases, and defects such as deformation, cracking, and swelling are likely to occur during degreasing. When the average particle diameter of the powder is 30 μm or more, the powder and the binder are easily separated during molding, and the density after sintering is low,
The strength of the sintered body also decreases.

Next, a method for producing a sintered body of the present invention using the above composition will be described. First, in a pressure kneader, heat kneading is performed until the powder obtained by adding the organic binder to the sinterable powder is uniformly dispersed, and the kneaded material is pulverized or formed into a bar shape or a pellet shape having a diameter of several millimeters by an extruder. Obtain molding material. The molding material is finished into a molded product having a desired shape using an in-line screw type or plunger type injection molding machine or extrusion molding machine. This compact is degreased and sintered in a processing furnace to obtain a powder sintered product as a final object. Although degreasing and sintering can be performed in an integrated processing furnace, the degreasing and sintering may be performed individually and sequentially in respective dedicated furnaces or in a continuous furnace using a conveyor.

In the processing furnace, the temperature exceeds the normal temperature and is 50 ° C. to 40 ° C.
If the heating rate when the temperature is raised to 0 ° C. is 5 ° C./hr or less, it takes 70 hours or more during that time, and the time until degreasing becomes longer, and extremely long until the product is finally completed. It will take time. In addition, the heating rate is 100 ° C./hr.
In the case described above, cracks, blisters, and other defects are likely to occur due to a rapid rise in temperature during degreasing. Therefore, it is desirable that the heating rate be in the range of about 15 to 50 ° C./hr.

The furnace pressure is such that the furnace temperature is 50 ° C. to 25 ° C.
During the period of 0 ° C., by applying a reduced pressure, the exudation, vaporization and evaporation of the low-melting organic compound such as paraffin wax added are promoted, and the organic compound which is thereafter degreased at a higher temperature is accelerated. Since the binder component can be smoothly decomposed, defects such as cracks and blisters during degreasing do not occur even in a thick molded product. The reduced pressure is preferably 0.
Should be 1 torr to 500 torr, 0.1 t
When the pressure is lower than orr, particularly when the pressure is 0.01 torr or less, the decomposition of the wax is rapidly promoted. Therefore, if the thickness of the molded body is large, defects such as cracks and swelling are caused. Further, when the pressure exceeds 500 torr, the pressure becomes close to the atmospheric pressure, and the leaching, vaporization and evaporation of the above-mentioned paraffin wax and the like are not promoted, and the organic binder component thereafter is not smoothly decomposed. Swelling and the like will occur.

By the above-described composition for injection molding and the treatment method thereof within the frame of the present invention, the long degreasing step which has conventionally been a problem in the production of powder molded / sintered bodies can be shortened. At the same time, defects such as deformation, cracking, and swelling during degreasing are eliminated, and a sintered body having excellent dimensional accuracy without physical and external defects after degreasing and sintering can be obtained.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention and comparative examples will be described.

[0020]

EXAMPLES Example 1 The following materials were used as raw materials. SUS316L powder (powder for sintering) 100 parts by weight Total binder amount 5.8 parts by weight

The binder composition is as follows. Graft polymer 20.0 vol% (main chain: polypropylene 70 wt%, side chain polystyrene 30 wt%) Graft copolymer 20.0 vol% (main chain: ethylene vinyl acetate copolymer 70 wt%, side chain: polystyrene 30 wt%) Paraffin wax (Melting point 63 ° C) 50.0 vol% polybutyl methacrylate 10.0 vol%

First, in a pressure kneader heated to 160 ° C., first, as a graft polymer, a resin whose main chain is made of polypropylene and a side chain is made of polystyrene, and a main chain is made of an ethylene-vinyl acetate copolymer. Is charged with a resin made of polystyrene and melted.
6 L powder (average particle size: 10 μm), paraffin wax (melting point: 63 ° C.) and polybutyl methacrylate were charged,
After kneading for 40 minutes and taking out, pulverize the kneaded material,
A molding composition was obtained. Next, a rectangular parallelepiped molded product having a thickness of 4 mm, a width of 10 mm, and a length of 60 mm was obtained at a molding temperature of 150 ° C.

Example 2 The following raw materials were used. SUS316L powder (powder for sintering) 100 parts by weight Total binder amount 5.8 parts by weight

The binder composition is as follows. Graft polymer 20.0 vol% (main chain: polypropylene 70 wt%, side chain polystyrene 30 wt%) Graft copolymer 20.0 vol% (main chain: ethylene vinyl acetate copolymer 70 wt%, side chain: polymethyl methacrylate) Paraffin wax (melting point 63 ° C) 50.0 vol% Polybutyl methacrylate 10.0 vol%

First, in a pressure kneader heated to 160 ° C., a resin whose main chain is made of polypropylene and whose side chain is made of polystyrene as a graft polymerized polymer, and whose main chain is made of an ethylene-vinyl acetate copolymer, Is charged with a resin made of polymethyl methacrylate, and after melting, SUS316L powder (average particle size: 10 μm), paraffin wax (melting point 63 ° C.), and polybutyl methacrylate are charged, kneaded for 40 minutes, and then taken out. The kneaded product was pulverized to obtain a molding composition. Next, molding temperature 1
4mm thick, 10mm wide, 60mm long at 50 ° C
Was obtained.

Example 3 The following raw materials were used. Zirconia powder (powder for sintering) 100 parts by weight Total binder amount 5.8 parts by weight

The binder composition is as follows. Graft polymerized copolymer 20.0 vol% (main chain: polypropylene 70 wt%, side chain polystyrene 30 wt%) Graft polymerized polymer 20.0 vol% (main chain: ethylene vinyl acetate copolymer 70 wt%, side chain: polystyrene 30 wt%) Paraffin Wax (melting point: 63 ° C.) 40.0 vol% Polybutyl methacrylate 10.0 vol% Stearic acid 5.0 vol% Dibutylphthalate 5.0 vol%

First, in a pressure kneader heated to 160 ° C., a resin whose main chain is made of polypropylene and whose side chain is made of polystyrene as a graft polymerization polymer, an ethylene-vinyl acetate copolymer whose main chain is made of Is charged with a resin made of polystyrene and melted, and then zirconia powder (5.4% yttrium oxide added, average particle size: 0.1%).
5 μm), paraffin wax (melting point 46 ° C.), polybutyl methacrylate, stearic acid, and dibutyl phthalate were added, kneaded for 40 minutes, taken out, and the kneaded product was pulverized to obtain a molding composition. Next, the molding temperature 15
Under the condition of 0 ° C., a rectangular parallelepiped molded product having a thickness of 4 mm, a width of 10 mm, and a length of 60 mm was obtained.

Comparative Example 1 The following raw materials were used. SUS316L powder (powder for sintering) 100 parts by weight Total binder amount 5.8 parts by weight

The binder composition is as follows. Ethylene vinyl acetate copolymer 20.0 vol% Polystyrene 15.0 vol% Polybutyl methacrylate 15.0 vol% Paraffin wax (melting point 46 ° C) 50.0 vol%

First, an ethylene-vinyl acetate copolymer, which is a thermoplastic resin, is placed in a pressure kneader heated to 160 ° C.
After charging and melting polystyrene and polybutyl methacrylate, SUS316L powder (average particle size: 1)
0 μm) and paraffin wax (melting point: 46 ° C.) were kneaded for 40 minutes, and the kneaded product was pulverized to obtain a molding composition. Next, at a molding temperature of 140.degree.
mm, a width of 10 mm and a length of 60 mm were obtained.

Comparative Example 2 The following raw materials were used. Zirconia powder (powder for sintering) 100 parts by weight Total binder amount 20 parts by weight

The binder composition is as follows. Ethylene vinyl acetate copolymer 20.0 vol% Polystyrene 15.0 vol% Polybutyl methacrylate 15.0 vol% Paraffin wax (melting point 46 ° C) 50.0 vol%

First, an ethylene-vinyl acetate copolymer, which is a thermoplastic resin, is placed in a pressure kneader heated to 160 ° C.
After polystyrene and polybutyl methacrylate were charged and melted, zirconia powder (5.4% yttrium oxide added, average particle size: 10 μm) and paraffin wax (melting point: 46 ° C.) were kneaded for 40 minutes, and then taken out.
The kneaded product was pulverized to obtain a molding composition. Next, at a molding temperature of 140 ° C., a thickness of 4 mm, a width of 10 mm, and a length of 6 mm.
A rectangular parallelepiped molded article of 0 mm was obtained.

The injection molded articles obtained in Examples 1 and 2 and Comparative Example 1 were placed in a furnace and heated from 50 ° C. to 260 ° C. at a rate of 30 ° C./hr at a pressure of 5 torr under a nitrogen atmosphere. , 260 ° C to 400 ° C, heating rate 50
Degreasing was performed at ° C / hr. The presence or absence of defects in the molded body after degreasing was confirmed. The results are as shown in Table 1.

[0036]

[Table 1]

In Comparative Example 1, no further heat treatment (sintering) was carried out because no good compact was obtained, and Examples 1 and 2
Sintering of only the compact was performed. The results were good as shown in Table 2.

[0038]

[Table 2]

The injection-molded articles obtained in Example 3 and Comparative Example 2 were placed in a furnace, and heated from 50 ° C. to 400 ° C. under a condition of a heating rate of 20 ° C./hr in the air and the atmosphere to degrease them. Was done. The presence or absence of defects in the molded body after degreasing was confirmed. The results are as shown in Table 3.

[0040]

[Table 3]

In Comparative Example 1, no further heat treatment (sintering) was performed because a good molded body was not obtained, and only the molded bodies according to Examples 1 to 3 were sintered. The results were good as shown in Table 4.

[0042]

[Table 4]

Next, a study was conducted using a graft polymer having a main chain of polypropylene and a side chain of polystyrene, and polypropylene and polystyrene without graft polymerization.

Example 4 The following materials were used as raw materials. SUS304L powder (powder for sintering) 100 parts by weight Total binder amount 6.0 parts by weight

The binder composition is as follows. Graft polymer 20.0 vol% (main chain: polypropylene 70 wt%, side chain polystyrene 30 wt%) Graft copolymer 20.0 vol% (main chain: ethylene vinyl acetate copolymer 70 wt%, side chain: polystyrene 30 wt%) Paraffin wax (Melting point 63 ° C) 40.0 vol% Carnauba wax 10.0 vol% Polybutyl methacrylate 10.0 vol%

In a pressure kneader heated to 160 ° C., first, as a graft polymer, a resin whose main chain is made of polypropylene and a side chain is made of polystyrene, and a main chain is made of an ethylene-vinyl acetate copolymer. Is charged with a resin made of polystyrene and melted.
4 L powder (average particle size: 10 μm), paraffin wax (melting point: 63 ° C.) and polybutyl methacrylate were charged,
After kneading for 40 minutes and taking out, pulverize the kneaded material,
A molding composition was obtained.

Comparative Example 3 The following materials were used as raw materials. SUS316L powder (powder for sintering) 100 parts by weight Total binder amount 6.0 parts by weight

The binder composition is as follows. Polystyrene 20.0 vol% Polypropylene 20.0 vol% Paraffin wax (melting point 63 ° C) 40.0 vol% Carnauba wax 10.0 vol% Polybutyl methacrylate 10.0 vol%

First, a resin composed of polypropylene and polystyrene was charged into a pressure kneader heated to 160 ° C. and melted, and then SUS316L powder (average particle diameter: 1)
0 μm), paraffin wax (melting point 63 ° C.), carnauba wax, and polybutyl methacrylate.
After kneading for minutes, the kneaded product was pulverized to obtain a molding composition.

Using the molding compositions of Example 4 and Comparative Example 3, two steps were provided in the lengthwise half of the rectangular parallelepiped as shown in FIG. 1 to form a molding having many corners and a thin tip. Created by injection molding. The results are as shown in Table 5 and show the superiority of Example 4 according to the present invention.

[0051]

[Table 5]

[0052]

As is evident from the above, the present invention does not cause defects such as cracks and swelling in the green body,
In addition, it is possible to obtain a sound degreased molded body without causing defects such as cracks and blisters even after degreasing, and as a result, to provide a technology for manufacturing a good sintered body without defects in a short time. is there.

[Brief description of the drawings]

FIG. 1 is a view showing a side surface (A) and a back surface (B) of a molded article obtained by injection molding a composition in one example.

Claims (4)

[Claims] 1. A. First Embodiment B. 100 parts by weight of a sintering powder composed of an inorganic powder, a metal powder, or a mixture thereof; The main chain is composed of a compound selected from polypropylene, ethylene-vinyl acetate copolymer, and ethylene-ethyl acrylate copolymer, and the side chain is composed of a compound selected from polystyrene, polymethyl methacrylate, or polybutyl methacrylate. And at least one organic compound having a melting point of 40 ° C. to 100 ° C. and a melt viscosity at 120 ° C. of 1000 mPa · s or less, and a total amount of 30 to 70 vol% (b2) And 5 to 25 parts by weight of an organic binder containing (1) as an essential component. 2. The composition according to claim 1, wherein the ratio of the main chain to the side chain of the graft polymer is 50 to 90 vol% of the main chain compound and 10 to 50 vol% of the side chain compound. 3. The method according to claim 1, wherein the melting point is 40.degree.
The organic compound having a melt viscosity at 20 ° C. of not more than 1000 mPa · s comprises at least one of paraffin wax, carnauba wax, urethanized wax, hardened castor oil, fatty acid ester and phthalate ester. Item 3. The composition according to Item 1 or 2. 4. An injection molding or an extrusion molding is performed using the composition according to any one of claims 1 to 3, and the obtained molded body is placed in a heat treatment furnace to perform degreasing and sintering. A method for producing a powder sintered product, characterized by obtaining a sintered product.