JPS6240431B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a composite powder in which a copper coating layer is formed on the surface of particles such as metal powder, alloy powder, or metal compound (hereinafter simply referred to as metal particles), and its uses include metal brushes, bearings, and current collectors. Our goal is to provide material powder that can be used for multiple purposes, such as brake materials and even building materials. General methods for coating metal particles with copper by depositing copper on the surface of the metal particles can be summarized as an electroless plating method. However, in this case, there is no problem if the metal particles themselves act as reducing agents in the aqueous solution, but there are particles that do not directly participate in the redox reaction. In this case, other substances that perform a reducing action are allowed to coexist in the system consisting of metal particles and copper liquid.
JP-A-48-88053 and JP-B-Sho.
There are publications such as No. 11258. The present invention relates to a method for producing a composite powder in which copper coating is applied to metal particles that cannot easily be used as a reducing agent.Therefore, the present invention relates to a method for producing a composite powder in which copper coating is applied to metal particles that cannot easily be used as a reducing agent. Become. This substance usually uses a metal such as iron, zinc, or aluminum, or a liquid reducing agent such as formalin, such as Fehling's solution.
In the conventional copper coating method using a metallic reducing agent, a large amount of reducing agent remains in the resulting powder, and high purity copper-coated metal particles cannot be obtained without an additional operation to remove the residual reducing agent, which complicates the manufacturing process. In addition, in the method using Fehring's solution, several types of auxiliary reagents are added in addition to copper salts as raw materials, but many of these auxiliary reagents are expensive, and copper-coated metal particles are also economically expensive. I had no choice but to do so. In the present invention, by adding copper salt crystals in an amount exceeding the solubility range with respect to the amount of water in the slurry to a slurry containing a mixture of metal particles to be coated with copper and a reducing agent for reducing copper ions, the surface of the metal particles is coated. It is possible to form a copper coating layer on the particles, reduce the rate of reducing agent mixed into the produced powder, and control the copper content in the copper coating particles according to the purpose.
Furthermore, even though the amount of reducing agent used is reduced compared to the conventional method, the residual copper concentration in the waste liquid can be reduced to ppm units, making waste liquid treatment easier. The method of the present invention will be explained in detail below. In the present invention, which relates to a copper coating method on metal particles, metal particles are added to a certain amount of water, and if necessary, a surfactant that imparts hydrophilicity to the particles is added. next,
A copper ion reducing agent is introduced, but the reducing agent used is a metal whose ionization tendency is more base than that of copper, such as zinc,
Use iron or aluminum, etc. Furthermore, copper salt crystals are added to the slurry of particles and reducing agent that has been fluidized by mechanical stirring. After the reaction is completed, the particles are sieved, dehydrated, washed with water, and dried by conventional methods to obtain copper-coated metal particles having the desired copper content. The diameter of the metal particles suitable for the present invention is preferably such that they can flow in water or liquid by stirring. Furthermore, when attempting to coat particles with poor hydrophilicity with copper, an organic or inorganic wetting agent may be added. As a reducing agent for copper ions, a metal whose ionization tendency is more base than copper is used. Among the various metals that can be used, zinc, iron, aluminum, etc. are suitable from the viewpoint of economy and availability. When considering the finish of the coated metal powder, such as the copper coating rate, the progress of oxidation of the coated copper, and the treatment of manufacturing waste liquid, zinc and iron are most suitable. These reactions are shown below. Cu ²⁺ +Zn=Cu+Zn ²⁺ ………(1) Cu ²⁺ +Fe=Cu+Fe ²⁺ ………(2) 3Cu ²⁺ +2Al=3Cu+2Al ³⁺ ………(3) Conventional method, that is, within the solubility range In the copper coating method on metal particles from a copper salt solution consisting of a concentration of In order to reduce the amount to 1.3 to 1.5 equivalents, the amount of reducing agent used must be increased to 1.3 to 1.5 equivalents. However, the large amount of reducing agent used is one of the factors that causes a large amount of reducing agent to remain in the produced powder, and it is necessary to add an operation for removing the residual reducing agent. However, in the method of the present invention in which copper salt crystals exceeding the solubility range are added, the residual copper concentration in the manufacturing waste liquid decreases to ppm units, even though the amount of reducing agent used is only 1.01 to 1.06 equivalents based on the reaction formula. Therefore, the reaction rate is improved, and the rate of unreacted reducing agent mixed into the produced powder can be reduced to about 0.3% or less. The reducing agent may have any external shape, such as square, rectangular, spherical, or even irregular shape, and if the size is expressed in terms of surface area, approximately 0.5 to 10 cm ² per piece is appropriate. If the surface area is less than 0.5 cm ² , the copper that is reduced and precipitated will coat the surface of the reducing agent itself instead of the particle surface, and if it exceeds about 10 cm ² , good flow of the reducing agent in the solution may not be achieved. However, the size of the reducing agent should be sized within the ^above range, as copper precipitates on the surface of the metal particles and segregates, and at the same time copper precipitates on the surface of the reducing agent itself in the same way as reducing agents smaller than 0.5 cm2. I hope that. As the copper salt crystal added as a copper source, salts with relatively high solubility, such as copper sulfate and copper chloride, are used. The solubility of copper sulfate (CuSO _{4.5H 2} O) in water is 18.2 g/100 g solution in terms of anhydride at 25°C, and the solubility of copper chloride (CuCl _{2.2H 2} O) is
43.6g/100g solution in terms of anhydride at 25℃ (published by Maruzen Co., Ltd., "Chemistry Handbook" published by the Chemical Society of Japan)
It is. The solubility of copper salts varies depending on the temperature of the solution, but the solubility in the present invention is determined based on the temperature of the water in which the copper salts are to be dissolved, and the amount of copper salts added is determined by the temperature of the water in which the copper salts are to be dissolved. This is the amount exceeding the solubility at temperature, and its upper limit is determined by the copper content to be coated. According to the method of the present invention, when copper salts are introduced into the reaction tank, a large amount of undissolved copper salt crystals flow in the tank, but as the reaction progresses, the crystals gradually dissolve and eventually Complete melting will result in all the copper coating the metal particles. In addition, the redox reaction is an exothermic reaction, and as the reaction progresses, the temperature of the solution rises, and depending on the amount of copper salts added, it reaches a boiling state. Dissolution also progresses. Note that the amount of copper salts added to the reaction tank may be sufficient as long as it satisfies the desired copper content of the resulting powder; however, care must be taken to prevent the salts that are generated from the substitution reaction between the copper salt and the reducing agent. It is also necessary to take into account the solubility of, for example, zinc sulfate, iron sulfate or aluminum sulfate. This is because the salts of these reducing agents are mixed into the produced powder, causing a decrease in the purity of the produced powder. However, in this case, the generated powder can be removed by washing with water, hot water, or other methods. In addition, the stirring reaction time is 20% regardless of the type of reducing agent.
~60 minutes is sufficient. The copper-coated metal particles thus obtained are made into a product powder through conventional dehydration, water washing, and drying steps. The examples shown below use lead powder as a representative example of metal powder, copper chromium alloy powder as a representative example of alloy powder,
Although molybdenum disulfide powder was illustrated as a representative example of water-insoluble metal salts, the method of the present invention is not limited to such metal powder particles. Example 1 200 g of lead powder having the particle size distribution shown in Table 1 and 212 g of flower-like zinc having a surface area of about 5 cm ² to 10 cm ² per piece were added to 1.3 g of tap water at 25°C, and the lead powder was Stirring was carried out to the extent that the zinc flowers flowed without settling (in this experimental device, 550 RPM, circumferential speed 145 m/min). To this, 809 g of industrial copper sulfate (equivalent to 200 g of copper) was added to aim for a copper content of 50% in the copper-coated lead powder. The above amount of zinc corresponds to 1.03 equivalents of the amount required to reduce copper in copper sulfate.

[Table] After stirring for 40 minutes, the mixture was sieved through a standard sieve (28 mesh), and 24 g remained on the sieve. The amount of liquid obtained by suctioning and dehydrating the bottom of the sieve with a Buchner container was 1.34.
The amount of residual copper was 0.2 ppm. The copper coating amount of the copper-coated lead was 47.53wt%, and the zinc content was 0.23wt%. The residue on the standard sieve (28 mesh) consisted of zinc and copper, and the zinc content was 21.16 wt%. The particle size distribution of the copper-coated lead powder produced is shown in Table 2, and the percentage of copper coating on the lead particles was determined by microscopic observation to be 98.0% (out of 1000 particles).
980 particles). The attached photo shows the state of copper adhesion to the lead surface by EPMA.

[Table] Comparative example Industrial copper sulfate similar to Example 1 was added to tap water 4.
809g (equivalent to 200g of copper) was dissolved. In this case, the copper sulfate was completely dissolved and no undissolved crystals remained. 200 g of lead powder and 212 g of flower-like zinc were added to this, and the mixture was stirred at 550 RPM (peripheral speed 145 m/min) for 40 minutes. After sieving with a standard sieve (28 mesh), the liquid obtained by suctioning and dehydrating the bottom of the sieve was 4.05, the residual copper concentration was 17.99g/, and the copper content in the coated lead powder under the sieve was 38.35wt%. It was hot. Example 2 500g of lead powder similar to Table 1 in 4.5g of tap water at 25℃
and 471 g of iron pieces (iron content: 98.9%) with a surface area of about 0.5 cm ² to 4 ^{cm 2} , and stirred to the extent that the lead does not settle and the iron pieces flow (600 RPM and periphery in this experimental device). The speed was 158m/min). The iron used as the reducing agent was ordinary industrial steel material that did not contain modifying additives such as Cr and Ni. In addition to this, 2022g of industrial copper sulfate was added with the goal of achieving a copper content of 50% in the copper-coated lead powder.
(equivalent to 500 g of copper) was added. This amount of iron corresponds to 1.06 equivalents of the amount required to reduce copper in copper sulfate. After stirring for 30 minutes, the mixture was sieved through a standard sieve (28 mesh), and 86 g remained on the sieve. The amount of liquid obtained by suctioning and dehydrating the bottom of the sieve with a Buchner Too is
4.8, and the residual copper concentration was 1.7 ppm. The copper content of the copper-coated lead powder is 46.38wt%, and the iron content is
It was 0.27wt%. The iron content of the sieve residue is
It was 29.18wt%. In addition, the copper coating rate on lead particles is 95.4% (954 out of 1000 particles).
particles). Example 3 Add 300 g of lead powder to 1.5 liters of tap water at 25°C as in Table 1.
45 g of an aluminum piece (99.2% aluminum content) with a surface area of approximately 1 cm ² to 5 cm ²
and stirred to the extent that the lead powder does not settle and the aluminum pieces flow (530 RPM in this experimental equipment).
The circumferential speed was 140m/min). In addition to this, 1214g of industrial copper sulfate was added with the goal of achieving a copper content of 50% in the copper-coated lead powder.
(equivalent to 300 g of copper) and 20 mg of common salt were added to impart activity to the reducing agent. This amount of aluminum corresponds to 1.04 equivalents of the amount required to reduce copper in copper sulfate. After stirring for 50 minutes, the mixture was sieved through a standard sieve (28 mesh), and 44 g remained on the sieve. The amount of liquid obtained by suctioning and dehydrating the bottom of the sieve with a Buchner funnel was 1.6, and the residual copper concentration was 4.6 ppm. The copper content of the copper-coated lead was 46.58 wt%, and the aluminum content was 0.17 wt%. The aluminum content of the residue on the sieve was 21.27wt%. In addition, the copper coating rate on lead particles is completely coated.
It was 86.5% (865 particles out of 1000 particles). Example 4 Copper content using zinc as reducing agent as in Example 1
An experiment was conducted to produce 80% coated lead. 50g lead powder
The rest is the same as in Example 1. At this time, 20 g remained on the standard sieve. The liquid volume was 1.38, and the residual copper amount was 3.4 ppm. The copper content of copper-coated lead is
The zinc content was 78.56wt% and 0.39wt%.
The zinc content of the residue on the sieve was 24.18 wt%, and the percentage of copper coating on the lead particles was 99.2% (992 out of 1000 particles), which was completely coated by microscopic observation. Example 5 300 g of copper chromium alloy powder with -100 mesh particle size and 318 g of flower-shaped zinc having a surface area of about 0.5 cm ² to 10 ^{cm 2} were added to tap water 2 at 25°C, and the copper chromium alloy powder was allowed to settle. Stirring to the extent that Zukatsu flower-shaped zinc flows (in this experimental device, 550 RPM, circumferential speed 145 m/
min). In addition to this, 1214 g of industrial copper sulfate (copper amount 300
g) was added. The above amount of zinc corresponds to 1.03 equivalents of the amount required to reduce copper in copper sulfate.
After stirring for 40 minutes, the mixture was sieved through a standard sieve (28 mesh), and 23 g remained on the sieve. The amount of liquid obtained by suctioning the bottom of the sieve with a Buchner toe and dehydrating it is 2.08
The amount of residual copper was 0.2 ppm. The copper content of the copper-coated copper chromium alloy powder is 48.56wt%, and the zinc content is
It was 0.15wt%. The residue on the standard sieve (28mesh) consists of copper and zinc, and the zinc content is 27.56wt
It was %. Microscopic observation shows that 99% of copper chromium alloy powder particles are completely coated.
(990 particles out of 1000 particles). According to the attached photo
The state of copper adhesion to the surface of copper chromium alloy powder by EPMA is shown. Example 6 200 g of MoS ₂ powder having the particle size distribution shown in Table 3 and 212 g of flower-like zinc having a surface area of approximately 0.5 cm ² to 10 cm ² were added to 1.3 g of tap water at 25°C to form MOS ₂ powder.
Stirring was carried out to the extent that the powder did not settle and the zinc flowers flowed (530 RPM and peripheral speed of 140 m/min in this experimental device). To this, 809 g of industrial copper sulfate (equivalent to 200 g of copper) was added with the aim of achieving a copper content of 50% in the copper-coated MoS ₂ powder. The above amount of zinc corresponds to 1.03 equivalents of the amount required to reduce copper in copper sulfate. After stirring for 60 minutes, it was sieved using a standard sieve (28mesh).
15g remained on the sieve. The bottom of the sieve was suctioned and dehydrated using a Buchner funnel, and the amount of liquid obtained was 1.38, and the amount of residual copper was 0.2 ppm. The copper content of copper coated MoS ₂ is
The zinc content was 0.28 wt%.
The residue on the standard sieve (28mesh) consisted of zinc and copper, and the zinc content was 38.14wt%. The particle size distribution of the produced copper-coated MoS ₂ powder is shown in Table 4, and the percentage of copper coating on the MoS ₂ particles was 95% (950 out of 1000 particles) as determined by microscopic observation. . By EPMA with attached photo
The state of copper adhesion to the MoS ₂ surface is shown.

【table】

【table】 [Brief explanation of the drawing]

The figure is a photograph substituted for a drawing, and was taken using an EPMA (X-ray microanalyzer, 500x) when the copper coating method according to the present invention was applied. Figure 1 shows the case of copper-coated lead powder, and A shows the composition. Statue, ro is Cu
- X-ray image of Kα, C is X-ray image of Pb-Lα, second
The figure shows the case of copper-coated copper chromium alloy powder, where A is the composition image, B is the X-ray image of Cu-Kα, and C is the X-ray image of Cr-Kα.
Line image, Figure 3 is the case of copper-coated MoS ₂ powder, A is the composition image, B is the X-ray image of Cu-Kα, C is the X-ray image of Mo-Lα
It is a line image.

Claims (1)

[Scope of Claims] 1. In a method for forming a copper coating layer on the surface of metal particles such as metal powder, alloy powder, water-insoluble metal salt powder, etc., the copper ion is added to reduce the metal particles to be coated and copper ions. Copper salt crystals are added in an amount exceeding the solubility relative to the amount of water in the slurry to a slurry containing a reducing agent of a metal whose ionization tendency is more base than that of copper, such as zinc, iron, or aluminum. A method for coating metal particles with copper, characterized in that the amount added is 1.01 to 1.06 equivalents relative to the amount of copper in the added copper salt crystal. 2 The surface area of the reducing agent is approximately 0.5 to 10 cm ² per piece.
A method for coating metal particles with copper according to claim 1.