JPH0257603A - Metal powder and its production - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

[Prior Art] Aluminum powder is known as a pigment for metallic coatings for automobiles, electrical appliances, etc., metallic color inks, and the like. Copper is used as a conductive powder used for electromagnetic shielding and antistatic purposes.
Silver-plated powders are known. (Tokuko Showa 47-301
No. 9, JP-A No. 60-243277, JP-A No. GL-16
(Refer to No. 3975) When aluminum powder is used as a pigment for metallic coatings of automobiles, etc., the color is limited to so-called silver color and lacks diversity. Copper powder becomes oxidized and turns black, making it unsuitable as a pigment for metallic paints. When copper powder is used as a so-called conductive powder for electromagnetic shielding, oxidation progresses to the container, making it difficult to maintain conductivity. In the case of aluminum powder, a dense oxide layer is formed on the surface and does not provide sufficient electrical conductivity.

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

[Means for Solving the Problems] As a result of intensive studies by the present inventors on metal powders in which the above problems were solved, we found that the average composition was CuX''A 11-x'
(However, 0.4 ≦ . That is, in the present invention, the average composition is Cux A l+
, x (0.4≦X≦0.995), and the surface A I /Cu ratio is the average composition A I /
The present invention relates to a metal powder characterized by being larger than Cu and a method for producing the same.

Metal powder Cu X A l +-x (0,4
≦X≦0.995), by changing X between 0.4 and 0.995, various colors such as bright bronze, gold, bright yellow, and silver color can be obtained, and the oxidation resistance is good. Therefore, discoloration due to oxidation does not occur. When used as a metal pigment for metallic coatings, X is preferably 0.4 to 0.97, and 0.5
-0.97 is more preferable, and 0.5-0.9 is even more preferable.

Since the metal powder of the present invention has excellent oxidation resistance, its conductivity does not deteriorate over time and is an excellent conductive metal powder. When used as a conductive metal powder, X is preferably 0.8 to 0.995, more preferably 0.90 to 0.99, and 0.
．． 92 to 0.98 is most preferred.

The method for producing the metal powder of the present invention is to collide a copper and aluminum melt (hereinafter referred to as melt) against a high-speed rotating body with good thermal conductivity, preferably in an inert gas, to solidify it, and then crush it. A method of colliding the ejected melt of the present invention with a high-speed airflow of inert gas, a method of colliding the ejected melt of the present invention with a high-speed airflow of inert gas, and then immediately colliding the ejected melt of the present invention with a high-speed airflow of inert gas, and then immediately Examples include a method of colliding with a rotating body.

The high-speed rotating body with good thermal conductivity is preferably made of metal such as copper, copper alloy, or iron alloy, and preferably has a shape such as a cylinder or a disk, and has an average rotational circumferential speed of 1.000 to 10.00 at the collision position.
0 m/min is preferable, 1,000 to 5,000 m/min
min is more preferred. A cooling mechanism using a coolant such as water may be attached to the high-speed rotating body. An inert gas is a gas that does not react at all or only very slowly with the melt of the present invention, such as argon, helium,
Nitrogen or a mixture thereof. The high-speed airflow of inert gas must have a linear velocity necessary to atomize the melt of the present invention and a flow rate necessary to cool the melt of the present invention at a cooling rate of 103° C./sec or more. No. A preferred method of preparing a high velocity stream of inert gas includes substantially adiabatic expansion of the high pressure inert gas.

The surface of the metal powder of the present invention is rich in aluminum,
It has a region where the concentration of aluminum gradually increases toward the surface of the powder. The surface atomic ratio (AI/Cu) is at least twice the average atomic ratio (AI/Cu), preferably 4
It is at least twice that amount, more preferably at least 10 times. The surface composition is measured using an XPS (X-ray photoelectron spectrometer) using Ka rays of magnesium as an X-ray source.

When measuring the surface composition, first remove deposits from the powder surface in order to improve measurement accuracy. That is, XPS
Powder uniformly dispersed on the flat sample stand
Etching is performed with argon ions for 10 minutes at an incident angle of 10°, an argon gas pressure of 10-7 Torr, and an acceleration voltage of 3 KeV, and then analyzed. This operation is repeated five 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, 1g of powder
,:;a Add nitric acid to completely dissolve, and then ICP the solution.
method (high-frequency inductively coupled plasma emission spectrometer).

[Example] Hereinafter, the present invention will be specifically explained using Examples and Comparative Examples.

Example 1 Copper powder with purity of 99.9% or more (manufactured by Kojundo Kagaku) 126g
and 5 g of aluminum powder with a purity of 999.9% or higher (manufactured by Kojundo Kagaku Co., Ltd.) were mixed and melted and mixed by high-frequency induction heating in an argon atmosphere. This sample was melted by high-frequency induction heating in an argon atmosphere in an aluminum crucible (with a nozzle with a stopper at the bottom), and the melt was 0.4 kg/cI11
A disk (φ200 mm, thickness LO ■ copper disk, surface temperature is 20 mm) rotating at 7200 rpm at normal pressure with a gas pressure of 2
~50°C) in 6 seconds. 100kg at the same time
/cm'G high pressure argon gas 330ON TP
51 was ejected into the melt in 6 seconds. The rapidly solidified powder was spherical with an average diameter of 40 μl.

As a result of XPS, the A I /Cu atomic ratio on the surface was 10. 30 g of the prepared powder was dispersed in 20 g of acrylic thermoplastic resin, applied onto a polyethylene terephthalate film, and dried at 50°C. The volume resistivity of the coating film was 9.5×10→(Ω·C11).

Further, the coating film was left in air at 80° C. and 70% humidity. The volume resistivity after 400 hours is 9.5X10' (Ω・c
m) was almost the same.

Example 2 126 g of copper powder and 1 g of aluminum powder were mixed and melted and mixed in an argon atmosphere. Average composition Al/Cu =
It was 0.02. After melting and mixing, it was filled into an aluminum crucible with the same shape as in Example 1, further melted by high-frequency induction heating, and placed under normal pressure at a gas pressure of 0.4 kg/co+'G.
It erupted in 0 seconds. At the same time, 100 kg/cm' high pressure argon 380ON T P 51 was jetted toward the melt. The rapidly solidified powder was a spherical powder with an average diameter of 10 μm.

As a result of XPS analysis, the A I / Cu atomic ratio on the surface is 7.
Met. 30 g of the prepared powder was dispersed in 20 g of an acrylic thermoplastic resin, applied onto a polyethylene terephthalate film, and dried at 50°C. The volume resistivity of the coating film was lXl0-' (Ω·am). Also,
The coating film was left in air at 80° C. and 70% humidity. 400
The volume resistivity after hours was approximately the same as 1×1 O −3 (Ω·cm).

Example 3 83 g of copper powder and 5 g of aluminum powder were mixed and melted and mixed in an argon atmosphere. Average composition Al/Cu-0
, 18. After melting and mixing, it was melted by high-frequency induction heating in an aluminum crucible with the same shape as in Example 2, and 0.4 kg was obtained.
The melt is rotated at 501 radial position (
It ejected in 8 seconds to a circumferential speed of 1,800 m/s. At the same time pressure 1
Argon of 00 kg/cm 2 was injected toward the melt at 2ONTP/g melt. Rapidly solidified powder has an average diameter of 40μ
It was l.

The powder had a golden color. When measured with XPS,
The surface composition was AI/Cu-13.

In addition, 2 g of powder was added to a dimethylethanolamine aqueous solution (p
H-9,2) and kept at 50°C for 1 hour, and the n1 value of generated hydrogen was determined to be 0.06o+1 (NTP).

Example 4 83 g of copper powder and 27 g of aluminum powder were mixed and melted and mixed under the same conditions as in Example 3. Average composition AI/Cu-
It was 1. After melting and mixing, the mixture was placed in an aluminum crucible having the same shape as in Example 3, and melted by high-frequency induction heating. Melt 72
A radial position 50 mm from the center of a disk (same shape as the disk used in Example 3) rotating at 0 rpm (peripheral speed 2200
m/s) at a gas pressure of 0.4 kg/cII' G for 6 seconds. At the same time, argon at a pressure of 100 kg/cm 2 was spouted toward the melt using 7 g of gas melon 3ONT P i . The rapidly solidified powder was spherical with an average diameter of 30 μl. The powder had a yellow color. When mj was determined by XPS, the surface composition was AI/Cu-30. Also,
2 g of powder was dissolved in dimethylethanolamine aqueous solution H (pH-9).
, 2) and kept at 50° C. for 1 hour, and the amount of hydrogen generated was measured, and it was found to be 0.03 ml (NTP).

Comparative Example 1 Commercially available copper powder (FCC115) Log was formed into a coating film in the same manner as in Example 1.2. The initial volume resistivity of the coating film is lXl0
-3 (Ω·cll). When left in air at 80℃ and 7% humidity for 400 hours, the resistance was 6×1O-3 (Ω
・am).

[Effects of the Invention] As explained above, the present invention provides a metal powder pigment for metallic coatings that has a novel color and is less likely to change color, and a conductive metal powder that does not deteriorate over time.

Patent applicant: Asahi Kasei Industries, Ltd. Agent Patent Attorney Hidetake Komatsu

Claims (4)

[Claims] (1) The average composition is Cu_XAl_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). (2) The average composition is Cu_XAl_1_-_X (0.4≦
X≦0.97), and the surface Al composition ratio (
A metal powder pigment characterized in that the Al composition ratio (to Cu) is larger than the average Al composition ratio (to Cu). (3) The average composition is Cu_XAl_1_-_X (0.8≦
A conductive metal powder having a surface Al composition ratio (to Cu) greater than an average Al composition ratio (to Cu). (4) The method for producing metal powder according to any one of claims 1 to 3, characterized in that the melt of aluminum and copper is rapidly solidified in an inert gas atmosphere.