JP2638271B2 - Production method of copper fine powder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing copper fine powder, and more particularly, to a method for producing spherical copper fine powder having a uniform particle size.

(Prior art) A conductor paste that forms a conductor thick film by coating on an insulating substrate such as glass or ceramics by a screen printing method, a direct drawing method, etc., and then firing is applied to gold, silver, silver / Pb, Powders of nickel, copper, etc. are used as conductive particles,
It is well known that there is a tendency to use a copper conductor paste in recent years.

Although the particle size of the copper powder used for the copper paste is 0.3 to 7.0 μm, it is effective to combine two or three types of rectified copper powder with a uniform grain system in order to obtain a dense conductor thick film. Furthermore, spherical copper powder is preferable from the viewpoint of screen printability, and since spherical copper powder has a smaller specific surface area than irregular-shaped copper powder, the amount of liquid organic medium (vehicle) necessary for pasting can be reduced. That is, since the oil absorption is small, a copper paste having a high concentration of copper powder can be obtained.

Furthermore, since spherical copper powder is more excellent in filling property than copper powder of irregular shape, it is easy to obtain a dense fired film.

As described above, a spherical sized copper fine powder is required as the copper powder used for the copper paste.

Here, “sizing” means that the particle sizes are uniform.

By the way, conventionally, as a method for producing copper fine powder, a mechanical pulverization method, an atomizing method, a gas phase reduction method, an in-gas evaporation method, an electrolytic method, and the like have been proposed, but a copper fine powder having a particle size of 0.3 to 7.0 μm has been proposed. A hydrazine reduction method can be cited as a production method for efficiently producing methane. That is, this is a method in which copper ions or copper powder in a solution or slurry is reduced with hydrazines, which are powerful reducing agents, to obtain metal powder.

Hitherto, the following proposals have mainly been made for the method for producing copper fine powder by the hydrazine reduction method.

A method of obtaining copper powder by adding hydrazine to an aqueous copper carbonate solution and heating. (JP-A-57-155302) A method in which a copper hydroxide slurry is converted into a copper oxide slurry with hydrazine or a hydrazine compound, and further reduced with hydrazine or a hydrazine compound (JP-A-62-99406).
issue).

A method of adding various surfactants to a reaction solution when reducing an aqueous solution of copper sulfate with hydrazine (JP-A-62-27508,
Nos. 62-40302, 62-77407 and 62-77408).

A method of adding a protective colloid to a reaction solution when reducing an aqueous copper sulfate solution with hydrazine (Japanese Patent Application Laid-Open No. 62-77406)
issue).

A method in which a reaction initiator is added when reducing an aqueous solution of copper sulfate with hydrazine (JP-A-63-27406).

A method of adding a protective colloid to a copper oxide slurry (Japanese Patent Publication No. 55562/1986).

A method in which the surface of copper oxide powder is coated with a silane coupling agent and then reduced with hydrazine (JP-A-2-34708).

A method in which a disproportionation reaction is caused on cuprous oxide with an acid, followed by hydrazine reduction (JP-A-2-129309).

(Problem to be Solved by the Invention) In the conventional hydrazine reduction method, when hydrazine is reduced from an aqueous solution of copper sulfate, not all divalent copper ions are directly reduced to metallic copper, but the following reaction is performed. Are mixed. Cu ²⁺ → Cu (OH) ₂ , Cu ²⁺ → Cu ₂ O, Cu (OH) ₂ → Cu
₂ O, Cu ²⁺ → Cu, Cu (OH) ₂ → Cu, Cu ₂ O → Cu.

For this reason, a uniform reduction reaction to metallic copper does not occur simply by adding the aqueous solution of copper sulfate hehydrazine, and the resulting fine copper powder has a wide particle size distribution and an irregular particle shape.

In the invention disclosed in Japanese Patent Application Laid-Open No. 62-99406, copper oxide is once formed from copper hydroxide using hydrazine or a hydrazine compound, and hydrazine or hydrazine is added to the copper hydroxide slurry thus obtained. When the compound is added, foaming occurs instantaneously (nitrogen gas generated by the reduction action of hydrazine), resulting in agglomerated copper oxide having a wide particle size distribution. Variation increases. Furthermore, when hydrazine is added to a copper hydroxide slurry, hydrazine easily reduces copper oxide to metallic copper, so that it is difficult to obtain uniform copper oxide.

In addition, even when copper oxide is used as a starting material, for the above-mentioned reason, in order to obtain a sized copper fine powder, a sized copper oxide powder must be obtained, and the sized copper oxide controlled to an arbitrary particle size. It is difficult and expensive to obtain flour industrially.

Thus, a first object of the present invention is to provide a method for easily and efficiently producing sized copper fine powder.

A second object of the present invention is to provide a method for easily and efficiently producing spherical sized copper fine powder.

(Means for Solving the Problems) Therefore, the present inventor focused on the fact that it is advantageous to reduce sized copper oxide powder with hydrazine in order to produce sized fine powders. After various studies on the production method of copper, copper hydroxide was first generated by addition of alkali, this was once converted to copper oxide with a reducing sugar, and finally reduced with hydrazine to produce reduced-sized copper fine powder. In particular, the present inventors have found that spheroidization is performed by heating the reaction solution prior to the addition of hydrazine, and that the resulting metallic copper powder also becomes spheroidized powder, thereby completing the present invention.

The present invention is a step of precipitating copper hydroxide from a copper salt aqueous solution,
Then, the obtained copper hydroxide is adjusted to pH 12 or higher, and then a reducing sugar is added to reduce to cuprous oxide.Then, the reaction solution of the cuprous oxide thus obtained is adjusted to 50 ° C or higher. And then reducing to metallic copper by adding a hydrazine-based reducing agent.

From another aspect, the present invention provides a method for producing a copper fine powder by reducing an aqueous copper salt solution using a hydrazine-based reducing agent, wherein the pH of the aqueous copper salt solution is adjusted before adding the hydrazine-based reducing agent.
After adjusting to 12 or more, reducing sugar was added and the reaction solution was heated to 50 ° C.
A method for producing copper fine powder, characterized by adding a hydrazine-based reducing agent after the above adjustment.

That is, according to the present invention, 2
Copper hydroxide powder is generated from the divalent copper ions, then the pH is adjusted to 12 or higher, and then the glucose hydroxide is reduced to cuprous oxide powder by adding glucose, and the reaction solution is adjusted to 50 ° C or higher. And
Thereafter, the powder is reduced from cuprous oxide powder to fine metallic copper powder with hydrazine.

In the present invention, the aqueous copper salt solution as a starting material is preferably an aqueous copper sulfate solution, but the same effect can be obtained by using an aqueous solution of another copper salt, for example, an aqueous solution of copper carbonate, copper nitrate, copper chloride and copper cyanide. Needless to say, there is. However,
Copper sulfate is the most preferred copper salt among these copper salts, because it is most industrially available and is judged from workability, waste liquid treatment and the like.

The use of a complexing agent is effective for stably dissolving Cu ²⁺ ions in an aqueous solution. As a usable complexing agent, known complexing agents such as sodium tartrate (Roschel's salt), amino acids such as arginine or glycine, and ammonia or an ammonia compound can be used. In order to produce copper fine powder having

As the pH adjuster used in the present invention, an alkaline pH adjuster capable of adjusting the pH to 12 or more is preferable. As an example,
Examples include sodium hydroxide and potassium hydroxide.

As the reducing sugar used in the present invention, besides glucose, reduction of ordinary monosaccharides, polysaccharides and the like can be used.

The hydrazine-based reducing agent used in the present invention as a reducing agent includes hydrazine compounds in addition to hydrazine, and includes hydrazine hydrate, hydrazine sulfate,
Hydrazine hydrochloride and the like can be mentioned, and hydrazine hydrate is preferred from the viewpoint of safety in handling and detergency.

As such a reducing agent, those other than the above-mentioned hydrazine and / or hydrazine compound may be blended if necessary, and examples thereof include alkali hypophosphite, alkali borohydride, and formalin. It is used in combination with hydrazine and / or a hydrazine compound because it has a lower reducing power and lower productivity.

Although the amount of the hydrazine-based reducing agent is related to the degree of its water solubility, it is basically preferable that the amount is at least the amount required for the theoretical production amount of the copper fine powder.

The particle size of the copper powder can be controlled by controlling the concentration of the reaction solution. Generally, as the concentration of the reaction solution increases, the particle size of the copper powder decreases.

In order to improve the fluidity, dispersibility, filling properties and oxidation resistance of the resulting copper fine powder, protective colloids such as gelatin and gum arabic, various surfactants, benzotriazole, oleic acid, etc. No rust inhibitor can be added.

The copper fine powder generated in the reaction solution can be collected by decantation, natural gravity filtration, filtration under reduced pressure, or the like.

Drying of the recovered copper fine powder can be performed by heating under a natural atmosphere or a vacuum atmosphere. The heating temperature is preferably 90 ° C. or less to prevent oxidation of the surface of the copper powder.

(Action) The process of producing the copper fine powder according to the present invention is divalent Cu ion → copper hydroxide → cuprous oxide → copper fine powder, and each process includes addition of alkali, addition of reducing sugar, and addition of hydrazine-based reducing agent. Progresses with time.

That is, it is not a complicated reaction in which metallic copper is generated from various states such as Cu ²⁺ ion, divalent copper hydroxide and monovalent cuprous oxide as in the conventional hydrazine reduction method. Since the metal copper fine powder is uniformly generated from the state, a sized metal fine powder having extremely uniform particle size can be obtained. In addition, sufficient spheroidization can be achieved by performing heat treatment in the step of cuprous oxide. The following describes each process.

First, Cu ions in a copper salt aqueous solution, for example, a copper sulfate aqueous solution, are all precipitated as copper hydroxide powder by addition of, for example, a sodium hydroxide aqueous solution as a pH adjuster (alkali). Next, by adding anhydrous glucose which is a reducing sugar, all the above-mentioned copper hydroxide powder is reduced to cuprous oxide powder. The produced cuprous oxide powder is a sized powder having an extremely narrow particle size distribution. Note that reducing sugars such as anhydrous glucose do not have the power to reduce metal copper, and the resulting powder is completely cuprous oxide powder. In other words, the reducing sugar is not limited to a specific one as long as copper hydroxide is used as cuprous oxide powder. However, when the pH is about 11 or less, cuprous oxide due to glucose reduction is not generated and copper hydroxide remains.

Finally, the addition of the hydrazine-based reducing agent uniformly reduces only the sized cuprous oxide powder to metallic copper, thereby producing a sized copper fine powder having an extremely sharp particle size distribution.

If the reaction solution is kept at 50 ° C. or higher before the addition of the hydrazine-based reducing agent, spherical sized copper powder can be obtained. In order to obtain more suitable sized copper powder, it is preferable to maintain the reaction solution at 60 ° C. or higher in order to obtain certainty. When the temperature of the reaction solution is lower than 50 ° C., the rate of forming the copper fine powder is low, and there is a possibility that a crystal habit is formed to be granular and not spherical.

Next, the present invention will be described more specifically with reference to examples.

Example 1 40 g of copper sulfate pentahydrate was dissolved in 320 ml of water, 0.811 g of sodium tartrate dihydrate was added, and the resulting solution was heated to 60 ° C.
Held. Then, in this solution, sodium hydroxide
160 g of sodium hydroxide solution dissolved in 1 water
0 ml was added to adjust the pH to 12.0. Deep blue copper hydroxide powder was formed in the solution. Next, 14.4 g of anhydrous glucose was added to generate cuprous oxide particles. The cuprous oxide particles were cubic particles having an extremely narrow particle size distribution of 4.0 μm ± 0.2 μm. Next, the temperature of the reaction solution was raised to 70 ° C., 35 ml of hydrazine hydrate (80%) was added, and the mixture was reacted for 60 minutes. After filtering the generated copper fine powder, vacuum drying was performed at 90 ° C., and the particle size was 0.5 μm.
A spherical sized copper fine powder of ± 0.1 μm was obtained.

Example 2 40 g of copper sulfate pentahydrate was dissolved in 320 ml of water, 0.811 g of sodium tartrate dihydrate was added, and the resulting solution was heated to 60 ° C.
Held. Then, in this solution, sodium hydroxide
A solution of 160 g of sodium hydroxide in 1
The pH was adjusted to 12.6 by adding 0 ml. Deep blue copper hydroxide powder was formed in the solution. Next, 14.4 g of anhydrous glucose was added to generate cuprous oxide particles. The cuprous oxide particles were spherical particles having an extremely narrow particle size distribution of 3.9 μm ± 0.2 μm. Next, the temperature of the reaction solution was raised to 70 ° C., 35 ml of hydrazine hydrate (80%) was added, and the mixture was reacted for 60 minutes.

After filtering the generated copper fine powder, perform vacuum drying at 90 ° C,
A spherical sized copper fine powder having a particle size of 0.7 μm ± 0.1 μm was obtained.

Example 3 40 g of copper sulfate pentahydrate was dissolved in 320 ml of water, 0.811 g of sodium tartrate was added, and the resulting solution was kept at 60 ° C. Next, 160 g of sodium hydroxide was added to this solution.
100 ml of an aqueous sodium hydroxide solution dissolved in water was added to adjust the pH to 12.0. Next, 14.4 g of anhydrous glucose was added to generate cuprous oxide particles.

Next, the solution was cooled to 50 ° C, 35 ml of hydrazine hydrate (80%) was added, and the temperature was raised to 70 ° C over 20 minutes.
The reaction was performed for 60 minutes.

After filtering the generated copper fine powder, perform vacuum drying at 90 ° C,
A spherical copper powder having a particle size of 1.2 μm ± 0.2 μm was obtained.

Example 4 40 g of copper sulfate pentahydrate was dissolved in 420 ml of water, 0.811 g of sodium tartrate dihydrate was added, and the resulting solution was heated to 60 ° C.
Held. Then, in this solution, sodium hydroxide
50 g of an aqueous sodium hydroxide solution obtained by dissolving 320 g in 1 water
The pH was adjusted to 12.0 by adding ml. Next, anhydrous glucose 14.0
g was added to produce cuprous oxide particles.

Next, the solution was cooled to 50 ° C, 35 ml of hydrazine hydrate (80%) was added, and the temperature was raised to 70 ° C over 20 minutes.
The reaction was performed for 60 minutes.

After filtering the generated copper fine powder, perform vacuum drying at 90 ° C,
A spherical copper powder having a particle size of 2.2 μm ± 0.3 μm was obtained.

Example 5 40 g of copper sulfate pentahydrate was dissolved in 520 ml of water, 0.811 g of sodium tartrate dihydrate was added, and the resulting solution was heated to 60 ° C.
Held. Then, in this solution, sodium hydroxide
An aqueous sodium hydroxide solution obtained by dissolving 320 g in
The pH was adjusted to 12.0 by adding ml. Next, anhydrous glucose 14.4
g was added to produce cuprous oxide particles.

Next, the solution was cooled to 50 ° C, 35 ml of hydrazine hydrate (80%) was added, and the temperature was raised to 70 ° C over 20 minutes.
The reaction was performed for 60 minutes.

After filtering the generated copper fine powder, perform vacuum drying at 90 ° C,
A spherical copper powder having a particle size of 3.1 μm ± 0.3 μm was obtained.

Comparative Example 1 40 g of copper sulfate pentahydrate was dissolved in 320 ml of water, and 0.811 g of sodium tartrate dihydrate was added.
Held. 160 g of sodium hydroxide is added to this solution.
70 cc of an aqueous solution of sodium hydroxide dissolved in water was added to adjust the pH to 11.0. Next, 14.4 g of anhydrous glucose was added, but no cuprous oxide powder was generated. Then add this solution to 70
The temperature was raised to ° C., and 35 ml of hydrazine hydrate (80%) was added, resulting in vigorous foaming. Thereafter, the reaction was carried out for 60 minutes.

The resulting copper fine powder was filtered and vacuum-dried at 90 ° C. to obtain a copper powder having a particle size of 0.05 to 0.2 μm.

Comparative Example 2 40 g of copper sulfate pentahydrate was dissolved in 320 ml of water, 0.811 g of sodium tartrate dihydrate was added, and the solution was kept at 60 ° C. To this solution was added 100 cc of an aqueous solution of sodium hydroxide in which 160 g of sodium hydroxide was dissolved in 1 water, and the solution was adjusted to pH.
Was adjusted to 12.0. The solution was then cooled to 25 ° C. and hydrazine hydrate (80%) was added, causing severe foaming. After the foaming subsided, the temperature was raised to 70 ° C. over 30 minutes, and the reaction was performed for 60 minutes.

The resulting fine copper powder was filtered and vacuum-dried at 90 ° C. to obtain a copper powder having a particle size of 0.03 to 0.20 μm.

(Effect of the Invention) According to the present invention, high-quality sized copper fine powder can be obtained from inexpensive raw materials that are easily available industrially, and are extremely useful as raw material copper powder for copper paste.

Claims (2)

(57) [Claims] A step of precipitating copper hydroxide from an aqueous copper salt solution;
Then, the obtained copper hydroxide is adjusted to pH 12 or more, and then a reducing sugar is added to reduce it to cuprous oxide, and then the reaction solution of the thus obtained cuprous oxide is adjusted to 50 ° C or more. And then reducing to metallic copper by adding a hydrazine-based reducing agent. 2. A method for producing a copper fine powder by reducing an aqueous copper salt solution using a hydrazine-based reducing agent, wherein the pH of the copper salt aqueous solution is adjusted to 12 or more before adding the hydrazine-based reducing agent. A method for producing fine copper powder, comprising adding a reducing sugar to adjust the reaction solution to 50 ° C. or higher, and then adding a hydrazine-based reducing agent.