JPH0613722B2 - Resin coating method for metal powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a metal powder used for a conductive paste, a sintered alloy, a magnetic material, a paint and the like. Excellent quality metal powder can be obtained.

[Prior Art] When molding a metal powder for a sintered alloy, the metal powder was often used as it was.

However, there is one in which the surface of the metal powder particles is coated with a resin, a liquid surfactant or the like for the purpose of preventing the adhesion and aggregation of the metal powder particles.

[Problems to be Solved by the Invention] If metal powder is used as it is, it is very susceptible to the influence of ambient gas such as rapid oxidation, and if it is used as a conductive paste, the metal powder alone will affect the substrate. Is not well established. Therefore, generally, a solvent is added to a resin or the like to form a paint or ink, which is applied to a metal powder or immersed in the metal powder, and then the solvent is dried or removed, or the metal powder is added to the solution. It was used by directly applying a mixture of

Further, in the case where metal powder is coated with a liquid surfactant or the like, it is difficult to handle because the coating layer is a liquid, and the thickness of the coating after evaporation of the liquid component is also extremely thin, so the coating may break. It became easy to peel off, and the non-contact property between metal powders was not good. In addition, there is also a point that the dispersibility of the metal powder, which affects the quality of the molding, and the ability to retain heat, are lacking, such as when the metal powder of the material does not reach the metal powder sufficiently during the filling during molding, melting begins. I was not satisfied.

The present invention is to solve these problems and to produce a metal powder that is easy to handle and has good moldability.

[Means for Solving the Problem] In the present invention, in the stirring and mixing apparatus, the resin powder is fused to the particle surface of the metal powder by the compressive force and the frictional heat to form the composite particles, and then the organic particles are added to the organic particles. After adding a solvent to swell the resin powder layer of the coating while stirring and mixing to regulate the particle size, heat drying to remove the solvent content is to coat the metal powder with the resin. State.

[Function] The particle surface of the metal powder is activated by mixing the metal powder and the resin powder, and the stirring and mixing action accompanied by the compressive force is repeatedly applied, and the resin powder causes the particle surface of the metal powder to be generated by the generation of frictional heat. Will be fused to. further,
When the resin powder is adhered and bonded thereon, the resin powder layer of the coating grows to form resin composite particles having a sufficient thickness.

Next, when a small amount of an organic solvent is uniformly added to this, the solvent also permeates from the surface of the composite particles into the particles of the resin powder in the coating layer to wet the resin layer of the coating from inside and outside the surface, The resin layer is swollen and a part of the surface of the resin powder is melted.

In this state, when the composite particles are subjected to the above-mentioned compression and stirring / mixing action, the resin powders are welded and bonded to each other, and the gas and the like in the coating layer are also extruded, so that there is no gap or pore between the resin powders. There are layers.

Furthermore, by heating and drying this, the solvent component can be volatilized and removed, and the resin surface of the coating layer can be softened and melted to adjust the particle size to one having a smooth surface without unevenness.

[Effects of the Invention] As described above, the present invention is capable of coating a metal powder with a resin very efficiently and firmly, and the composite metal powder produced in this manner is excellent in the following points. .

In other words, because it is firmly and airtightly coated with resin,
It has excellent storability because it is not affected by oxidation, nitriding, sulfurization, chlorine, water vapor, and other solvent gases.

Since it is possible to increase the coating amount of the resin with respect to the metal powder and to thicken the coating layer, it is possible to improve the non-contact property between the metal powders and increase the melt holding resistance during molding and filling.

Further, since the composite metal powder is sized, the particles are less likely to aggregate, the dispersibility is good, and the moldability is good.

Further, in the present invention, gold, silver, copper, iron, chromium, nickel,
It is applicable to a wide range of metals such as cobalt, titanium, tungsten, molybdenum, and aluminum, and the coating resin is polyethylene, polypropylene, polyester, polymethylmethacrylate (PMMA), styrene,
Polyamide, polyimide, etc. can be freely selected.

Example A copper powder having an average particle size of 10 μm was used as a metal powder, PMMA having a particle size of 0.05 to 0.5 μm was used as a resin powder, and butyl acetate was used as a solvent. The weight ratio of these metal powder, resin powder and solvent is 90%, 9.5% and 0.5%. As a device for stirring and mixing the metal powder and the resin powder for drying, the mixing and drying device shown in FIG. 1 was used.

A stirring blade 4 swirls along the wall surface 2 in the stirring chamber 1 by the rotating shaft 3. A nozzle 12 for adding a solvent is additionally provided in the stirring chamber 1. A gas blow-in port 5 is provided at the center of the bottom of the stirring chamber 1 and communicates with a lower air chamber 6 having a hot air inlet 7 therebelow.

A drying chamber 8 having an exhaust port 9 and provided with a filter 10 is arranged above the stirring chamber 1. The upper part of the drying chamber 8 is formed into a curved surface shape so that the raw material that has risen along the wall surface 2 goes around to the center and descends and circulates upward. A jacket 11 connected to a heat source (not shown) is attached to the outer walls of the stirring chamber 1, the lower air chamber 6, and the drying chamber 8.

In the above apparatus, all steps from stirring and mixing to coating and compounding, solvent addition, sizing, and drying are performed in the stirring chamber 1, but mixing and compounding are mainly performed by the stirring blade 4 and drying is performed. In addition to sending heated air from the lower part to fluidize it, it is also performed by heat transfer from the jacket 11.

The volatilized solvent gas is passed through the filter 10 and escaped from the exhaust port 9.

Thus, the copper powder coated with PMMA has an average particle size of about 1
It has a thickness of 0.5 μm, is uniform and has good dispersibility, and is also excellent when used as a conductive paste.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing an outline of a mixing and drying apparatus for carrying out this embodiment. In the figure, 1 ... stirring chamber, 4 ... stirring blade, 5 ... gas inlet, 7 ... hot air inlet, 8 ... drying chamber, 9 ... exhaust port, 10 ... filter, 11 ... jacket, 12 ... Nozzle.

Claims (1)

[Claims] 1. A particle size of 0.3 to 20 μm in a stirring and mixing apparatus.
The step of fusing the resin powder to the surface of the metal powder particles of m by a compressive force and frictional heat to form composite particles, and adding an organic solvent to the composite particles to swell the resin powder layer of the coating while stirring and mixing. A method for coating a metal powder with a resin, which comprises coating the metal powder particles with a resin by a step of sizing the composite particles and a step of heating and drying the composite particles to remove a solvent component.