JPH0610287B2 - Manufacturing method of metal powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for efficiently obtaining metal powder, particularly metal powder having a diameter of about 0.1 to 50 μm.

Conventional technology As a typical production method for producing powders of metals and alloys, molten metal is made to flow out from a small hole, high-pressure water or gas is sprayed onto this, and the molten metal is pulverized all at once by the pressure. Atomization to obtain metal powder is widely performed, but this method has a wide particle size distribution of 30 μm to 1 μm.
It is common to obtain particles having a particle size of about 00 μm.

In addition, a vacuum evaporation method recently developed as a method for producing ultrafine powder can obtain metal powder having a particle size of 100 nm (0.1 μm) or less.

Problems to be Solved by the Invention According to the above-mentioned conventional techniques, the particle size is 0.1 μm to 30 μm.
Although it is difficult to produce a metal powder having a size of about m, a particle size of 0.1 μm to 30 μm is required as a particularly preferable paste for patterning of recent printed circuits.

Means for Solving the Problems The present invention has been made in view of the above situation, and a metal and a heat having a viscosity higher than the melting point or the partial melting temperature of the metal are higher than the viscosity of the metal. Fine droplets or semi-molten liquid obtained by mixing and mixing a plastic resin at a temperature equal to or higher than the melting point of the metal or equal to or higher than the partial melting temperature of the metal and disperse the metal melt in a viscous medium made of a polymer material by the shearing force After forming droplets, and then solidifying the fine droplets by cooling, the thermoplastic resin is solubilized and removed to obtain metal powder, particularly metal particles having a particle diameter of 0.1 μm to 30 μm. Is.

When the metal and the thermoplastic resin are mixed in a molten state, the metal is dispersed very well. Since the metal melt usually has a low viscosity and a large surface tension, it has a property of being divided by a not so large shearing force and aggregating into a spherical shape due to a high surface tension. The present invention takes advantage of this property. It was used for.

Further, the viscous medium made of the thermoplastic resin used in the present invention is a viscous substance at the temperature at which the metal becomes a melt, and the viscosity is better as compared with the viscosity of the metal melt. When the viscosity of the viscous medium is small, the metal droplets divided by the shearing force are likely to be recombined to increase the diameter, and it becomes difficult to efficiently obtain the metal powder having the particle diameter intended by the present invention. .

As the viscous medium used in the present invention, various thermoplastic resins are suitable, for example, polyethylene, vinyl chloride, polypropylene, poly-methylpentene 1, polysulfone, polyether sulfone, polyether ether ketone, polyamide, polyester, polycarbonate. ,
Polyacrylic acid ester or the like can be used.

The metal may be a simple metal such as Cu, Al, Sn, Pb, Ia, Bi, or Sn-Pb, Sn-Zn, Sn-Sb-Cd, Sn-Pb-Bi, Sn-Pb.
-Cd-Bi, Bi-Sn-In, Bi-Pb-Sn-In, Bi-Pb-Sn-
Alloys such as Cd-In and Zn-Al can be used.

In the practice of the present invention, the viscosity of the thermoplastic resin is considerably high at each temperature, and the flexibility of selection is great in accordance with the temperature at which the metal melt is formed.

In a typical embodiment of the present invention, the viscosity of the viscous medium is at least 100 times higher than the viscosity of the metal melt, and it can be said that this degree facilitates surrounding and dispersing the metal melt as droplets by shearing force.

In consideration of the thermal decomposition temperature of the thermoplastic resin constituting the viscous medium used in the present invention, the range of the metal is not limited, and is limited to the metal having a melting point of about 300 ° C. or less. However, when using polyetheretherketone (made by PEEKCIC), which has a high thermal decomposition temperature, it is 400
It can also be applied to a metal having a melting point of about ° C.

Next, the method of solubilizing the thermoplastic resin that constitutes the viscous medium is basically arbitrary, but it is generally considered that the method of solubilizing the thermoplastic resin using a solvent that dissolves the thermoplastic resin is easy. As another special method, depolymerization of a polymer material can be used to lower the molecular weight. Basically, fine metal powder can be separated without damage.

The separation and classification of the metal powder after the solution of the thermoplastic resin can be performed by any method. That is, for example, coarse particles are separated and then separated by a centrifugal separator, and classification is performed according to the sedimentation speed. Alternatively, it is also possible to classify once with a dry powder and then classify with a cyclone.

Examples Example 1 A combination of an alloy of lead: tin 1: 1 and an ethylene vinyl acetate copolymer of 14% vinyl acetate, which was controlled at a blending ratio and an operation of both, at a temperature range of 185 to 220 ° C. Kneaded

The first is that the weight mixing ratio of the alloy and the copolymer is 1: 1 and the kneading temperature is a temperature at which all the alloys are melted.
C. and kneaded with a closed blade rotary kneader.
After the alloy was dispersed, it was cooled to 150 ° C., taken out, made into a sheet by a roll, and further pulverized by a pretizer.

In No. 2, the weight mixing ratio of the alloy and the copolymer was set to 10: 1, and the kneading temperature was set to 185 to 205 ° C. at which the alloy was partially melted.

Both were separately dissolved in toluene to dissolve the copolymer,
Coarse particles were removed using a 0 mesh wire mesh. 10 more
The solution was allowed to stand for a minute to have sedimentation, and the sedimentation portion and the suspended matter in the liquid were separated.

The suspended matter in the liquid according to No. 1 was collected as powder by a centrifugal separator. The second settling fraction and the first centrifugally separated powder were washed with toluene and the yield particle size was measured.

The product obtained by the process 1 had a yield of 51% and a particle size of 0.5.
Was ~ 5 μm.

The product obtained by the process 2 had a yield of 85% and a particle size of 10
Was about 30 μm.

Example 2 Polystyrene and indium were kneaded and extruded by an extruder in a weight ratio of 1: 1.2. Kneading temperature is 160-1
It was extruded from the extruder at 75 ° C. as a cord having a diameter of about 2 mm. Next, after the cord body was crushed, polystyrene was dissolved with titanium dichloride. The powder size distribution of the obtained powder is 0.5 ~
5 μm 53%, 5-30 μm 39%, 30 μm or more 8%
Met.

Example 3 Silver 3% lead alloy and melt fluorate (MFR) 0.03
The high-density polyethylene of was kneaded at a weight ratio of 1: 1. The kneading temperature is 305 to 315 ° C. The kneading machine used was a closed blade rotating type.

After the alloy was sufficiently dispersed in polyethylene, it was cooled to 220 ° C. and 50 parts by weight of dioctyl phthalate was added to 100 parts by weight of polyethylene and kneaded. This addition is to soften the polyethylene. The kneaded mixture was taken up from a kneader, rolled into a sheet, and pulverized by a pretizer.

Next, xylene was added to this powder to dissolve polyethylene, and the metal powder was separated. The obtained metal powder has a particle size of 0.5.
The yield of ˜5 μm was 60%.

Example 4 100% of polyvinyl alcohol to which 30% by weight of water was added was added with steam by a closed type kneader.
Keep the temperature of ℃, 1 per 1 part by weight of polyvinyl alcohol
0 parts by weight of a bismuth-lead-tin alloy having a melting point of 95 ° C. was added and kneaded. Next, this was cooled to 50 ° C. and then taken out and pulverized.

This was treated with hot water to dissolve polyvinyl alcohol and separate the metal powder.

The yield of the metal powder of this example having a particle size of 10 to 30 μm was 78%.

In the present invention, as described above, formal resin, urethane resin, polyamide resin, polyester resin and the like can be used, but these resins can be easily made into a solution by hydrolyzing with an alkali.

As described above, the method of the present invention is a relatively simple method,
It is possible to obtain metal powder having a particle size of 0.1 to 30 μm, which was difficult to produce by the conventional method.

Claims (1)

[Claims] 1. A viscosity produced by kneading a metal and a thermoplastic resin having a viscosity higher than that of the metal at a temperature equal to or higher than the melting point of the metal or equal to or higher than a partial melting temperature of the metal to melt the thermoplastic resin. Manufacture of metal powder characterized by dispersing a metal melt in a medium to form fine metal droplets, then cooling and solidifying the metal droplets, and then removing the thermoplastic resin by solution. Method.