KR100891746B1 - Preparation method for copper powders using thiourea complexation - Google Patents

Abstract

The present invention relates to a method for producing a copper powder, and more particularly, to a copper complex formed by dissolving copper sulfate pentahydrate in distilled water and adding thiourea as a complexing agent, an aqueous hypophosphite solution is added as a reducing agent to fine copper. The present invention relates to a method for producing a copper powder which can be reduced at room temperature as compared to a conventional method for preparing a copper powder and does not require a surfactant and an organic solvent.

Copper, thiourea, hypophosphite aqueous solution

Description

Preparation method for copper powder using thiourea complexing agent

The present invention relates to a method for producing a copper powder, and more particularly, to a copper complex formed by dissolving copper sulfate pentahydrate in distilled water and adding thiourea as a complexing agent, an aqueous hypophosphite solution is added as a reducing agent to fine copper. The present invention relates to a method for producing a copper powder which can be reduced at room temperature as compared to a conventional method for preparing a copper powder and does not require a surfactant and an organic solvent.

Copper powder is an inexpensive metal material with good electrical conductivity. It is a circuit forming material for printed wiring boards, various electrical contact material materials, external electrode materials such as capacitors, internal electrodes of multilayer ceramic capacitors (MLCC), and PDP ( It is widely used as a material for securing electric current such as plasma display panel (FED), field emission display (FED) and automobile heating wire.

Research on the preparation of copper powder has been conducted for a long time and various methods such as evaporation / condensation, pyrolysis, chemical reduction, micro-emulsion, hydrothermal synthesis, and sol-gel Known. The gas phase reduction method is widely used due to the advantage of producing high purity copper powder, but has problems due to low productivity, use of a large amount of reducing gas, generation of harmful gases generated during decomposition of copper salts, and high reduction temperature. Compared to the gas phase reduction method described above, the chemical reduction method produces a low purity copper powder, but the disadvantages of the gas phase reduction method can be compensated for by the relatively low reduction temperature, fast reduction time, and high productivity.

As a method for producing copper powder by chemical reduction method known by domestic and Japanese patent applications, some water-soluble copper salts are used, but mostly insoluble copper salts (Cu ₂ O, CuO), copper hydroxide, and copper carbonate are surfactants. (A very part of the complexing agent) is dispersed in a water-soluble medium (or an organic solvent) to decompose the copper salt or reduce the copper ions by introducing hydrazine and hydrazine derivatives as reducing agents. Examples of patent applications in which a water-soluble copper salt is used as a method for producing a copper powder in place of an insoluble copper salt are as follows.

Japanese Patent Application Laid-Open No. 03-287707 discloses copper particles prepared by mixing hydrazine in an aqueous solution in which copper formate, copper chloride, and copper pyrophosphate (Cu ₂ P ₂ O ₇ ) are dissolved and heated and reduced at 20 to 150 ° C. Known methods. Japanese Patent Application Laid-Open No. 04-235205 discloses copper hydroxide produced by dissolving copper sulfate in distilled water, followed by addition of potassium sodium tartrate, gelatin as a surfactant, complete dissolution and addition of sodium hydroxide (or potassium hydroxide), It is known to manufacture copper powder from anhydrous glucose and hydrazine hydrate. Japanese Patent Laid-Open No. 63-310911 discloses a cuprous sulfate aqueous solution obtained by a catalytic reaction from a copper sulfate aqueous solution of pH 1 containing a metal copper net and a surfactant at a high temperature of 150 ° C. or higher as a non-oxidizing atmosphere, 100 ° C. or lower. Methods for producing monodisperse copper powders are known. Japanese Patent Laid-Open No. 62-077406 relates to a method for producing copper powder from arabic gum as a surfactant at 30 ° C, an aqueous solution of hydrazine hydrate as a reducing agent, and an aqueous solution of copper sulfate which is a water-soluble copper salt. Republic of Korea Patent No. 486604 relates to a method for producing fine copper particles by adding sodium hydroxide to an aqueous copper chloride solution to produce copper hydroxide and copper oxide, and by adding hydrazine as a reducing agent. Republic of Korea Patent Publication No. 2005-3169 relates to a method for producing copper particles using a water-soluble copper salt selected from copper sulfate, copper chloride, copper nitrate, ammonia water as a complexing agent, ascorbic acid as a reducing agent, a surfactant. The reduction temperature was maintained at 35 ° C. or lower. Korean Unexamined Patent Publication No. 2001-61982 discloses that copper hydroxide obtained by reacting a water-soluble copper salt with an alkali salt is first reduced as an aqueous solution of glucose, and then dispersed in distilled water. Hydrazine hydrate was added to the suspension as a reducing agent and secondary reduced to prepare copper particles.

As described above, the method for producing copper powder used a hydrazine compound, a surfactant, and a complexing agent as a reducing agent from copper oxide, copper carbonate, and copper hydroxide (when a water-soluble copper salt is used) as the copper compound. Compared to the copper production by conventional gas phase reduction, the chemical reduction method is advantageous in terms of relatively low reduction temperature, short reduction time, mass production, generation of harmful gas compounds and treatment. However, Ag and Pd compounds, which are used as nucleating agents for copper ions, are very expensive and have low purity because other ions are included in the copper particles after reduction, and low solubility and high temperature when the polyhydric alcohol is used as a medium for reducing and thermal decomposition. Without the reduction operation (180 ° C.), there is a limitation in mass production of copper particles. Although hydrazine derivative compounds and formaldehyde are powerful reducing agents with a wide pH range and few residual products, they have problems of high price (140 to 920 won / g) or high respiratory toxicity (carcinogenicity). Therefore, there is a need for a method of preparing copper powder for use of inexpensive reducing agents (18-34 won / g), exclusion of organic solvents, and relaxation of high temperature reduction conditions (when polyhydric alcohol or fatty acid ester is used as organic solvent). .

Accordingly, the present inventors have relatively little adverse effect on the human body from the results of the conventionally known copper powder manufacturing literature, avoiding surfactants and organic solvents using an inexpensive reducing agent, and can cause a copper reduction reaction at room temperature The method of copper reduction was studied and a method for producing copper powder can be satisfied by using copper sulfate pentahydrate as a water-soluble copper salt, hypophosphorous or hypophosphite aqueous solution as a reducing agent, and thiourea as a complexing agent. The present invention has been completed.

Therefore, an object of the present invention is to dissolve the copper sulfate pentahydrate in water at room temperature (20 ~ 30 ℃), to add a small amount of thiourea (thiourea) to prepare a copper ion and a thiourea complex compound, and then added a reducing agent to reduce the copper The present invention provides a method of preparing a powder powder by filtering, washing, and drying the powder solution, respectively.

In order to achieve the above object,

The present invention

Preparing an aqueous copper sulfate solution by dissolving copper sulfate pentahydrate in distilled water at 20 to 30 ° C;

Adding a thiourea as a complexing agent to the copper sulfate aqueous solution to generate a copper-thiourea complex compound;

Preparing a copper powder precipitate by adding a reducing agent to the complex; And

Filtering, washing and drying the precipitated copper powder

It characterized by a method for producing a copper powder comprising a.

As described above, the present invention can produce a large amount of copper powder from a copper sulfate aqueous solution using a reducing agent without requiring a high reduction temperature, a surfactant and an organic solvent. The copper powder thus prepared may be a circuit forming material of a printed wiring board, various electrical contact materials, external electrode materials such as a capacitor, an internal electrode of a multilayer ceramic capacitor (MLCC), a plasma display panel (PDP), or a FED. (Field Emission Display), automobile heating wire, etc. can be used.

The present invention provides a conventional copper powder by dissolving copper sulfate pentahydrate in distilled water and adding fine aqueous solution of hypophosphorous acid as a reducing agent to a copper-thiourea complex compound produced by adding thiourea as a complexing agent. Compared to the method of using a relatively low toxicity and inexpensive reducing agent (18 ~ 34 won / g), high temperature reducing conditions, a method for producing a copper powder capable of mass production without using a surfactant.

Hereinafter, the present invention will be described in more detail.

The maximum concentration of copper sulphate dissolved in distilled water at 20-30 ° C is determined from the equilibrium solubility of copper sulphate at atmospheric pressure, approximately 17-20 wt%. In order to reduce the filtration time of the reduced copper particles in the present invention, to generate secondary particles, and to avoid unnecessary side reactions, the concentration of copper sulfate pentahydrate was set as 2 to 5% by weight.

The weight ratio of thiourea to copper sulfate pentahydrate added for the production of copper-thiourea complexes was set in the range of 1: 2 to 1: 10. According to the research of Donna et al., The copper-thiourea compound is attached to 7 copper thioureas with two copper ions to form a complex so that the weight ratio of thiourea and copper sulfate pentahydrate is almost 1: 1, but if it is The sulfur component decomposed in urea is bound to the surface of the copper particles and is not removed. If the amount of the complexing agent is too small, the reduction reaction of copper does not proceed due to the high reduction potential of copper [Doona et al., Inorganic Chemistry, 35, 3210. (1996)].

Due to the fact that the structure and reduction reaction mechanism of the copper-thiourea complex compound was not fully identified and the slow reduction reaction rate, the amount of the aqueous hypophosphorous acid solution added in the present invention was set as 25 to 55 weight times based on the copper sulfate pentahydrate.

The present invention uses hypophosphorous acid or hypophosphorous acid solution as a reducing agent, commercially available aqueous hypophosphorous acid solution is applied to the concentration of hypophosphorous acid is 37% by weight or 50% by weight, both types can be used.

After the reduction reaction of copper is completed within 10 seconds to 5 minutes, copper powder is generated and settles to the bottom of the reactor, and the copper powder is recovered from the reaction mother liquor to the GF / C filter paper having a pore size of about 1.3 μm. The copper powder is washed with distilled water at 20-30 占 폚 and dried at 80-120 占 폚. Incomplete cleaning results in a greenish yellow precipitate on the surface of the copper particles.

Copper powder produced from the present invention is a circuit forming material of a printed wiring board, various electrical contact portion materials, external electrode materials such as capacitors, internal electrodes of a multilayer ceramic capacitor (MLCC), plasma display panel (PDP) , FED (Field Emission Display), automobile heating wire, etc. can be used.

Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited to these Examples.

Example 1

1.22 g of crystalline copper sulfate pentahydrate was completely dissolved in distilled water at 25 ° C. to obtain an aqueous solution of copper sulfate. The amount of distilled water added at this time was 42.7 g. After the copper sulfate pentahydrate was completely dissolved, 0.5 g of thiourea was added. After thiourea was completely dissolved in an aqueous copper sulfate solution, 49.49 g of a phosphinic acid solution as a reducing agent was added thereto. After addition of the reducing agent, the rapid reduction of copper ions proceeded rapidly (2 minutes 18 seconds), and a dark red copper powder precipitate was formed. The precipitate was filtered, washed with 1.3 μm GF / C filter paper and dried at 100 ° C. The copper powder obtained after drying was 0.347 g (yield 48.5%). 1 is an X-ray diffraction curve of the copper powder obtained in Example 1 [see FIG. 1].

Example 2

1.5 g of crystalline copper sulfate pentahydrate was completely dissolved in distilled water at 25 ° C. to obtain an aqueous solution of copper sulfate. The amount of distilled water added at this time was 40.03 g. After the copper sulfate pentahydrate was completely dissolved, 0.5 g of thiourea was added. After thiourea was completely dissolved in an aqueous copper sulfate solution, 40.13 g of an aqueous hypophosphite solution was added. A dark red copper powder precipitate formed after completion of the reduction reaction (3 minutes 11 seconds). The precipitate was filtered, washed with 1.3 μm GF / C filter paper and dried at 100 ° C. The copper powder obtained after drying was 0.626 g (yield 65.3%).

Example 3

1.12 g of crystalline copper sulfate pentahydrate was completely dissolved in distilled water at 25 ° C. to obtain an aqueous solution of copper sulfate. The amount of distilled water added at this time was 40.13 g. After the copper sulfate pentahydrate was completely dissolved, 0.15 g of thiourea was added. After thiourea was completely dissolved in an aqueous copper sulfate solution, 49.7 g of a phosphinic acid solution as a reducing agent was added thereto. A dark red copper powder precipitate formed after completion of the reduction reaction (41 seconds). The precipitate was filtered, washed with 1.3 μm GF / C filter paper and dried at 100 ° C. The copper powder obtained after drying was 0.594 g (yield 83%).

Example 4

1.19 g of crystalline copper sulfate pentahydrate was completely dissolved in distilled water at 25 ° C. to obtain an aqueous solution of copper sulfate. The amount of distilled water added at this time was 40.04 g. After the copper sulfate pentahydrate was completely dissolved, 0.14 g of thiourea was added. After thiourea was completely dissolved in an aqueous copper sulfate solution, 64.37 g of an aqueous hypophosphite solution was added. A dark red copper powder precipitate formed after completion of the reduction reaction (3 minutes 51 seconds). The precipitate was filtered, washed with 1.3 μm GF / C filter paper and dried at 100 ° C. The copper powder obtained after drying was 0.563 g (74% yield).

Figure 1 shows the XRD diffraction curve of the copper powder obtained in Example 1.

Claims (2)

Preparing an aqueous copper sulfate solution by dissolving copper sulfate pentahydrate in distilled water at 20 to 30 ° C; Generating a copper-thiourea complex compound by adding thiourea as a complexing agent to the copper sulfate aqueous solution; Preparing a copper powder precipitate by adding a reducing agent selected from hypophosphorous acid or hypophosphorous acid solution to the complex compound; And Filtering, washing and drying the precipitated copper powder Method for producing a copper powder, characterized in that consisting of. delete

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