JPH0711003B2 - Metal powder and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a metal powder used for metallic coating of automobiles, electronic devices and the like, electromagnetic shielding, antistatic and the like, and a method for producing the same.

[Prior Art] Aluminum powder is known as a pigment for metallic coating of automobiles, electric appliances and the like, and metal color ink. Copper as a conductive powder used for electromagnetic shielding and antistatic,
Silver-plated powders are known. (Japanese Patent Publication No. 47-3019,
(See JP-A-60-243277 and JP-A-61-163975) When aluminum powder is used as a pigment for metallic coating of automobiles, the color is limited to so-called silver color,
Lack of versatility. Copper powder is oxidized and turned black and is not suitable for metallic paint pigments. When used as a so-called conductive powder used for electromagnetic shielding and the like, the copper powder easily oxidizes and it is difficult to maintain the conductivity. In the case of aluminum powder, a dense oxide layer is formed on the surface and does not give sufficient conductivity.

[Problems to be Solved by the Invention] The present invention, when used as a pigment for metallic coating,
Pigment with a wide selection of color tones and no change in color tone,
Another object of the present invention is to provide a stable metal powder whose electric resistance does not change for a long time when used as a conductive metal powder and a method for producing the same.

[Means for Solving the Problems] The inventors of the present invention have made earnest studies on the metal powder with which the above problems have been solved, and as a result, found that the average composition is Cu _x Al _{1 -x} (however,
≦ X ≦ 0.995), and the surface Al / Cu ratio is
Found a metal powder characterized by being larger than Al / Cu,
The present invention has been reached. That is, the present invention has an average composition of Cu _x A
l _1-x (where 0.4 ≦ X ≦ 0.995), surface Al / C
The present invention relates to a metal powder having a u ratio larger than that of Al / Cu having an average composition and a method for producing the same.

In the metal powder Cu _x Al _1-x (0.4 ≦ X ≦ 0.995) of the present invention, X is 0.
Various colors such as light copper color, gold color, light yellow color, and silver yellow color can be obtained by changing the value between 4 and 0.995, and discoloration due to oxidation does not occur because of good oxidation resistance. When used as a metallic pigment for metallic coating, X is preferably 0.4 to 0.97, more preferably 0.5 to 0.97, still more preferably 0.5 to 0.9.

Since the metal powder of the present invention has excellent oxidation resistance, it is an excellent conductive metal powder without deterioration in conductivity over time. When used as a conductive metal powder, X is preferably 0.8 to 0.995, more preferably 0.90 to 0.99, and most preferably 0.92 to 0.98.

As a method for producing the metal powder of the present invention, a melt of copper and aluminum (hereinafter referred to as a melt) is collided with a high-speed rotating body having good thermal conductivity to solidify, and then crushed. A method of colliding a jetted melt of the present invention with a high-speed stream of an inert gas, a jetted melt of the present invention and a high-speed stream of an inert gas are collided, and then quickly with good thermal conductivity and high speed Examples include a method of colliding with a rotating body.

The high-speed rotating body with good thermal conductivity is preferably a metallic material such as copper, copper alloy, iron alloy, etc., the form is preferably a cylinder, a disc, etc., and the rotating peripheral speed is preferably 1,000 to 10,000 m / min at the collision position on average. , 1,000 to 5,000 m / min is more preferable. A cooling mechanism using a coolant such as water may be attached to the high-speed rotating body. The inert gas is a gas which reacts with the melt of the present invention at all or very slowly, and is, for example, argon, helium, nitrogen or a mixture thereof. The high-velocity stream of the inert gas must have a linear velocity required for refining the melt of the present invention and a flow rate required for cooling the melt of the present invention at a cooling rate of 10 ³ ° C / sec or more. I have to. A preferred method of adjusting the high velocity flow of the inert gas is to adiabatically expand the high pressure inert gas.

The surface of the metal powder of the present invention is rich in aluminum,
There is a region where the concentration of aluminum gradually increases toward the surface of the powder. The surface atomic ratio (Al / Cu) is at least 2 times, preferably at least 4 times, more preferably at least 10 times the average atomic ratio (Al / Cu). The surface composition is measured by XPS (X-ray photoelectron spectroscopy analyzer) using magnesium Kα ray as an X-ray source.

When measuring the surface composition, first, the deposits on the powder surface are removed in order to improve the measurement accuracy. That is, the powder uniformly dispersed on the XPS flat sample stage was etched with argon ions for 10 minutes under the conditions of an incident angle of 90 ° to the sample stage, an argon gas pressure of 10 ^-7 Torr, and an accelerating voltage of 3 KeV. analyse. This operation is repeated 5 times, and the average value of the analysis is taken as the surface composition.

The average composition is measured according to the following method. First, concentrated nitric acid is added to 1 g of the powder to completely dissolve it, and the solution is analyzed by the ICP method (high-frequency inductive coupling plasma emission spectrometer).

[Examples] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Example 1 126 g of copper powder having a purity of 99.9% or more (manufactured by Kojundo Chemical Co., Ltd.) and a purity of 999.
9 g or more of aluminum powder (manufactured by Kojundo Chemical Co., Ltd.) (5 g) was mixed and melt-mixed by high frequency induction heating in an argon atmosphere. This sample is melted in an alumina crucible (having a nozzle with a stopper at the bottom) by high frequency induction heating in an argon atmosphere, and the melt is heated at a gas pressure of 0.4 kg / cm ² at a normal pressure of 7200 rpm.
It was jetted in 6 seconds toward a disc (φ200 mm, thickness 10 mm copper disc, surface temperature: 20 to 50 ° C.) rotating at. 100k at the same time
High pressure argon gas 3300 NTP of g / cm ² G was released toward the melt in 6 seconds. The rapidly solidified powder was spherical with an average diameter of 40 μm.

The average Al composition ratio (versus Cu) measured by ICP was 0.09. The measurement results using XPS are Al / Cu (atomic ratio) of 10,9,8,7,6 from the surface, and the Al composition ratio of the surface (to Cu) (average of the above 5 measured values) is It was 8.

The obtained powder (30 g) was dispersed in a liquid of acrylic thermoplastic resin (20 g) and ethyl cellosolve (5 g), coated on a polyester film, and dried at 50 ° C. The thickness of the coating film was 45 μm.
The volume resistivity of the coating film measured by the 4-terminal method was 3 × 10 ⁻³ Ωcm. The coated film was left to stand in the air at 80 ° C. and 70% humidity for 400 hours. The volume resistivity was almost unchanged.

Example 2 126 g of copper powder and 1 g of aluminum powder were mixed and melt-mixed in an argon atmosphere. The average composition was Al / Cu = 0.02.
After melt-mixing, the mixture was filled in an alumina crucible having the same shape as in Example 1, further melted by high-frequency induction heating, and jetted under normal pressure at a gas pressure of 0.4 kg / cm ² G for 10 seconds. At the same time, 100kg / cm
High-pressure argon 3800 NTP ² was jetted toward the melt. The rapidly solidified powder was a spherical powder having an average diameter of 10 μm.

The average Al composition ratio was 0.09. The measurement results using XPS are Al / Cu (atomic ratio) of 7,6,5,4,3 from the surface, and the Al composition ratio (vs. Cu) of the surface (average of the five measured values) is It was 5. 35 g of the obtained powder was added to 20 g of acrylic thermoplastic resin.
And dispersed in a solution of 5 g of ethyl cellosolve, applied on a polyester film, and dried at 50 ° C. Coating thickness is 50 μm
Met. The volume resistivity of the coating film measured by the 4-terminal method is 1.5.
It was × 10 ^-3 Ωm. The coated film was left to stand in the air at 80 ° C. and 70% humidity for 400 hours. The volume resistivity was almost unchanged.

Example 3 63 g of copper powder and 5 g of aluminum powder were mixed and melt-mixed in an argon atmosphere. The average composition was Al / Cu = 0.18.
After melt-mixing, high-frequency induction heating and melting were performed in an alumina crucible having the same shape as in Example 2, and the melt was melted at a gas pressure of 0.4 kg / cm ^2.
50 from the center of the disk (same as in Example 1) rotating at 000 rpm
Ejected in 8 seconds to a radial position of mm (peripheral speed 1800 m / s). At the same time, argon with a pressure of 100 kg / cm ² was spouted toward the melt with 20 NTP / g melt. The rapidly solidified powder had an average diameter of 40 μm.

The powder had a golden color. The average Al composition ratio was 0.19. The measurement results using XPS are Al / Cu (atomic ratio) of 13,12,11,10,9 from the surface, and the Al composition ratio of the surface (to Cu)
The (average of the five measured values) was 11. Also powder
2 g was placed in a dimethylethanolamine aqueous solution (pH = 9.2), kept at 50 ° C. for 1 hour, and the amount of hydrogen generated was measured and found to be 0.06 ml (NTP).

Example 4 63 g of copper powder and 27 g of aluminum powder were mixed and melt-mixed under the same conditions as in Example 3. The average composition was Al / Cu = 1. After melt mixing, the mixture was put into an alumina crucible having the same shape as in Example 3, and was melted by high frequency induction heating. The melt was rotated at 7200 rpm to a radial position of 50 mm from the center of the disk (the same shape as the disk used in Example 3) (peripheral speed 2200 m / s), and a gas pressure of 0.4 kg / cm ² G for 6 seconds. Gushed at. At the same time, argon with a pressure of 100 kg / cm ² was ejected toward the melt with a gas amount of 30 NTP / g melt. The rapidly solidified powder was spherical with an average diameter of 30 μm. The powder had a yellow color. The average Al composition was 1.0. X
The measurement results using PS show that Al / Cu (atomic ratio) of 30,
29, 28, 27, 26, and the Al composition ratio of the surface (to Cu) (5 above)
The average of the individual measured values) was 28. Also, put 2g of powder in dimethylethanolamine aqueous solution (pH = 9.2),
It was kept at ℃ for 1 hour and the amount of hydrogen generated was measured and found to be 0.03
It was ml (NTP).

Comparative Example 1 10 g of a commercially available copper powder (FCC115) was coated as in Examples 1 and 2. The initial volume resistivity of the coating film is 1 × 10 ^-3 (Ω · cm)
Met. When left in the air at 80 ° C and 70% humidity for 400 hours, it increased to 6 × 10 ^-3 (Ω · cm).

[Effects of the Invention] As described above, the present invention provides a metallic powder pigment for metallic coating which has a novel color and is resistant to discoloration, and a conductive metallic powder which does not deteriorate with time.

Claims (4)

[Claims] 1. The average composition is represented by Cu _x Al _1-x (0.4 ≦ X ≦ 0.995), and the Al composition ratio (to Cu) on the surface is larger than the average Al composition ratio (to Cu). Metal powder characterized by. 2. The average composition is represented by Cu _x Al _1-x (0.4 ≦ X ≦ 0.97), and the surface Al composition ratio (to Cu) is larger than the average Al composition ratio (to Cu). Metal powder pigment characterized by. 3. The average composition is represented by Cu _x Al _1-x (0.8 ≦ X ≦ 0.995), and the surface Al composition ratio (to Cu) is larger than the average Al composition ratio (to Cu). Conductive metal powder characterized by: 4. A melt of aluminum and copper is rapidly solidified in an inert gas atmosphere.
Item 7. A method for producing a metal powder according to any one of items.