JPH04116109A - Production of fine copper powder - Google Patents

Abstract

PURPOSE:To easily and efficiently produce spherical fine copper powder of uniform size by reducing copper hydroxide deposited from an aq. soln. of a copper salt into cuprous oxide and further reducing this cuprous oxide into metallic copper. CONSTITUTION:Alkali is added to an aq. soln. of a copper salt such as copper sulfate to form copper hydroxide powder. Reducing sugar such as anhydrous glucose is then added to form cuprous oxide particles. The resulting reactive liq. is heated to about 70 deg.C, a hydrazine type reducing agent such as hydrazine hydrate is added and they are brought into a reaction. Formed fine copper powder is separated by filtration and dried in vacuum. High-grade fine copper powder of uniform size useful as copper powder for copper paste is obtd. from low-cost starting material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing fine copper powder, and more particularly to a method for producing fine spherical copper powder with uniform particle size.

(Prior art) Gold, silver, silver/Pd, gold, silver, silver/Pd, etc. are used as conductor pastes, which are coated onto insulating substrates such as glass or ceramics by screen printing or direct writing, and then fired to form a thick conductor film. Powders such as nickel and copper are used as conductive particles, but
It is well known that there is a trend in recent years to use copper conductor paste.

The particle size of copper powder used in copper paste is 0.3 to 7.0μ
- However, in order to obtain a fine conductor thickness, it is effective to combine two to three types of sized copper powder with uniform particle sizes. Furthermore, spherical copper powder is preferable in terms of screen printability, and since spherical copper powder has a smaller specific surface area than irregularly shaped copper powder, the amount of liquid organic medium (vehicle) required for paste formation can be reduced. In other words, since the oil absorption is small,
It has the characteristic that a copper paste with a high concentration of copper powder can be obtained.

Furthermore, since spherical copper powder has better filling properties than irregularly shaped copper powder, it is easier to obtain a fired film that is less susceptible to cold damage.

As described above, LF-shaped sized fine copper powder is required as the copper powder used in the copper paste.

Here, "sized grains" means that the grain sizes are uniform.

By the way, mechanical pulverization method, atomization method, gas phase reduction method, evaporation method in gas, electrolysis method, etc. have been proposed as methods for producing fine copper powder, but A hydrazine reduction method can be cited as a manufacturing method for efficiently producing fine copper powder.

That is, this is a method in which the same ions or copper powder in a liquid or slurry are reduced with hydrazine, which is a strong reducing agent, to obtain metal powder.

The following main proposals have been made so far regarding the method for producing fine copper powder using the hydrazine reduction method.

■A method of obtaining copper powder by adding hydrazine to an aqueous copper carbonate solution and heating it. (Unexamined Japanese Patent Publication No. 57-155302) ■
A method in which copper hydroxide slurry is made into copper oxide slurry with hydrazine or a hydrazine compound, and then further reduced with hydrazine or a hydrazine compound (Japanese Patent Application Laid-Open No. 62-994
No. 06).

■A method of adding various surfactants to the reaction solution when reducing an aqueous copper sulfate solution with hydrazine (Japanese Patent Application Laid-open No. 6227508
No. 62-40302, No. 62-77407, No. 62-77408).

■A method of adding a protective colloid to the reaction solution when reducing sulfuric acid prepared water I8 solution with hydrazine (Japanese Patent Application Laid-Open No. 627740
No. 6).

(2) A method of adding a reaction initiator when reducing an aqueous copper sulfate solution with hydrazine (Japanese Patent Application Laid-Open No. 63-27406).

■A method of adding a protective colloid to copper oxide slurry (Japanese Patent Publication No. 55562/1983).

(2) A method in which the surface of copper oxide powder is coated with a silane coupling agent and then reduced with hydrazine (Japanese Unexamined Patent Publication No. 2-34708).

(2) A method in which cuprous oxide is subjected to a disproportionation reaction with an acid and then reduced with hydrazine (JP-A-2-129309).

(Problem to be solved by the invention) When reducing hydrazine from an aqueous copper sulfate solution in the conventional hydrazine reduction method, not all of the divalent copper ions are directly reduced to metallic copper, but the following reaction are mixed.

Cu2°−+Cu(Off)2, Cu”−+Cu2O
, Cu (OH) z→cuzo, Cu"→Cus C
u(Oft)z−+Cu.

CuzO-Cu.

For this reason, simply adding hydrazine to an aqueous copper sulfate solution does not cause a uniform reduction reaction to metallic copper, and the resulting fine copper powder has a wide particle size distribution and an amorphous particle shape.

In the invention disclosed in JP-A No. 62-99406, copper oxide is formed from copper hydroxide using hydrazine or a hydrazine compound. When the compound is added, foaming occurs instantaneously (nitrogen gas generated by the reducing action of hydrazine), resulting in agglomerated copper oxide with a wide particle size distribution. The barafuki becomes larger. Furthermore, when hydrazine is added to copper hydroxide slurry, hydrazine easily reduces copper oxide to metallic copper.
It is difficult to obtain uniform copper oxide.

Furthermore, even when copper oxide is used as a starting material, for the reasons mentioned above, in order to obtain sized fine copper oxide powder, sized copper oxide powder must be obtained. It is difficult and expensive to obtain powder industrially.

Thus, the first object of the present invention is to provide a method for easily and efficiently manufacturing sized fine copper 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 Problem) 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 powder, and After conducting various studies on the manufacturing method of The present invention was completed based on the knowledge that spheroidization is achieved by heating the reaction solution prior to addition of hydrazine, and that the resulting metallic copper powder also becomes spherical pollen.

The present invention comprises steps of precipitating copper hydroxide from an aqueous copper salt solution, and reducing the obtained copper hydroxide to cuprous oxide.
This is a method for producing fine copper powder, which is characterized in that it is then carried out through the step of reducing the cuprous oxide thus obtained to metallic copper.

According to a preferred embodiment of the present invention, a method for producing fine copper powder by reducing an aqueous copper sulfate solution using a hydrazine-based reducing agent is characterized in that an alkali and reducing sugar are added before adding hydrazine. do.

That is, according to the present invention, copper hydroxide powder is generated from divalent copper ions by adding alkali, then the copper hydroxide powder is reduced to cuprous oxide powder by adding glucose, and then cuprous oxide is produced by hydrazine. Rather than powder, it is reduced to a fine powder of metallic copper.

According to one embodiment of the present invention, in a method for producing fine copper powder by reducing 7 volumes of copper salt water using a hydrazine-based reducing agent, pl+ of the copper salt aqueous solution is added before adding the hydrazine-based reducing agent. After adjusting to 12 or more, reducing sugar may be added, and then a hydrazine-based reducing agent may be added.

According to another aspect of the present invention, the hydrazine reducing agent may be added after the reaction solution is adjusted to 60°C or higher before the addition of the hydrazine reducing agent.

In the present invention, the copper salt aqueous solution as a starting material is preferably a copper sulfate aqueous solution, but other copper salt aqueous solutions, such as charcoal M
It goes without saying that similar effects can be obtained by using aqueous solutions of copper, copper nitrate, copper chloride, and copper cyanide.However, copper sulfate is the most industrially available of these copper salts, and has a higher workability. Judging from waste liquid treatment etc., it is the most preferred copper salt.

Note that it is effective to use a complexing agent to stably dissolve Cu'' ions in an aqueous solution. Examples of complexing agents that can be used include sodium tartrate (Rotschul's salt), amino acids such as arginine or glycine, ammonia or Although known complexing agents such as ammonia compounds can be used, Kuchi-Nshuru salt is preferred in order to produce fine copper powder with a particle size suitable for copper powder for copper paste.

As the pHUi4 regulator used in the present invention, pl+ is 12
Alkaline PL + regulator that can be adjusted to above is preferable.
Examples include sodium hydroxide and potassium hydroxide.

In addition to grapevine, the reducing sugar used in the present invention can be
! Reducing sugars such as Class II, Class II, etc. 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 these include hydrazine hydrate, hydrazine sulfate, hydrazine hydrochloride, etc. However, safety in handling and From the viewpoint of detergency, hydrazine hydrate is preferred.

Such reducing agents may include agents other than the above-mentioned hydrazine and/or hydrazine compounds, if necessary, such as alkali hypophosphite, alkali borohydride, formalin, etc. Since it has lower reducing power and lower productivity than hydrazine, it is used in combination with hydrazine and/or hydrazine compounds.

The amount of the hydrazine-based reducing agent is related to its degree of water solubility, but basically it is preferable to make a mold that is necessary for the amount of linked rings produced in the steel mill.

The particle size JTj of the copper powder can be controlled by controlling the concentration of the reaction solution. Generally, the higher the concentration of reaction mW, the smaller the particle size of the copper powder.

In addition, in order to improve the fluidity, dispersibility, filling property, and oxidation resistance of the produced fine copper powder, protective colloids such as gelatin and gum arabic, various surfactants, benzotriazole, oleic acid, etc. are added to the reaction solution. It is okay to add rust inhibitors.

The fine copper powder produced in the reaction solution can be recovered by decantation, natural gravity filtration, vacuum filtration, or the like.

The recovered steel mill powder can be dried by heating in a natural atmosphere or in a vacuum atmosphere. The heating temperature is preferably 90'C or less in order to prevent oxidation of the surface of the copper alloy.

(Function) The process of producing fine copper powder according to the present invention is to produce fine copper powder (divalent Cu ions -> copper hydroxide -> cuprous oxide), and each process involves addition of alkali, addition of reducing sugar, and reduction of hydrazine. It progresses reliably over time by adding the agent.

In other words, unlike the conventional hydrazine reduction method, a complex reaction in which metallic copper is generated from each state of Cu" ions, divalent copper hydroxide, monovalent cuprous oxide, etc. is not performed, but a state of sized cuprous oxide is generated. Metallic steel mill $5) powder is produced uniformly from the powder, so that a finely sized metal powder with extremely uniform particle size can be obtained.Furthermore, sufficient spheroidization is possible by heat treatment at the cuprous oxide stage.

Each process will be described below.

First, all Cu ions in a copper salt aqueous solution, such as a copper sulfate aqueous solution, are precipitated as copper hydroxide powder by adding, for example, a sodium hydroxide aqueous solution as a ρI+ 31 stabilizer (alkali). Next, by adding anhydrous glucose, which is a reducing sugar, all of the above-mentioned copper hydroxide powder is reduced to cuprous oxide powder. The produced cuprous oxide powder is a sized powder with an extremely narrow particle size distribution. Note that reducing sugars such as anhydrous grapes do not have the power to reduce metallic copper (the powder produced is completely cuprous oxide powder. In other words, this reducing sugar converts copper hydroxide into cuprous oxide powder). However, if ρ11 is about 11 or less, cuprous oxide by the grape tIMi1 element is not generated and copper hydroxide remains.

Finally, by adding a hydrazine-based reducing agent, uniform reduction of only the sized cuprous oxide powder to metallic copper occurs, resulting in the production of sized fine copper powder with an extremely sharp particle size distribution.

Note that if the reaction solution is kept at 60° C. or higher prior to the addition of the hydrazine-based reducing agent, spherical sized fine copper powder can be obtained. If the temperature of the reaction solution is 50° C. or lower, the production rate of copper fine powder is slow, crystal habit is produced, and the powder becomes granular, which may not be spherical.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 40 g of copper sulfate pentahydrate was dissolved in 320 ml of water, and 0
．． 811 g of tartrate dihydrate were added and the resulting solution was kept at 60°C. Next, 100 ml of a sodium hydroxide aqueous solution prepared by dissolving 160 g of sodium hydroxide in 11 water was added to this solution to bring the pl+ to 1.
Adjusted to 2.0. Deep blue copper hydroxide powder was produced in the solution. Next is anhydrous grape tJ! Inject i14.4g,
Cuprous oxide particles were produced. The cuprous oxide particles were cubic particles with an extremely narrow particle size distribution of 4.0 μm±0.2 μm. Next, the reaction solution was heated to 70°C and 35 stones of hydrazine hydrate (80%) were added! and reacted for 60 minutes.

After filtering the produced fine copper powder, vacuum drying is performed at 90°C.
A spherical sized copper fine powder with a particle size of 0.5 μm ±0.1 μm was obtained.

Example 2 40 g of copper sulfate pentahydrate was dissolved in 320 ml of water, and 0
．． 811 g of sodium tartrate trihydrate was added and the resulting solution was kept at 60°C. Then, in this solution,
Add 200ml of a sodium hydroxide aqueous solution prepared by dissolving 160g of sodium hydroxide in 11 parts of water to reduce p++ to 1.
Adjusted to 2.6. Deep blue copper hydroxide 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 with 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 mff1 of hydrazine hydrate (80%) was added, and the reaction solution was allowed to react for 60 minutes.

After filtering the produced fine copper powder, vacuum drying is performed at 90°C.
A spherical sized copper fine powder with a particle size of 0.7 μm±0.1 μm was obtained.

Example 3 40 g of copper sulfate pentahydrate was dissolved in 320 mQ of water, and 0
．． 811 g of sodium tartrate dihydrate was added and the resulting solution was maintained at 60'C. Next, 100 ml of a sodium hydroxide aqueous solution prepared by dissolving 160 g of sodium hydroxide in 11 water was added to this solution to make po 12
Adjusted to 0. Next is Anhydrous Buto! 14.4 g was added to generate cuprous oxide particles.

Next this? After cooling the 8 solution to 50°C, 35 mff of hydrazine hydrate (80%) was added, and the solution was heated for 20 minutes.
The temperature was raised to 0°C and the reaction was carried out for 60 minutes.

After filtering the produced fine copper powder, it was vacuum dried at 90° C. to obtain spherical copper powder with a particle size of 1.2 μm±0.271 m.

Example 4 40 g of copper sulfate pentahydrate was dissolved in 420 ml of water, and 0
．． 811 g of sodium tartrate dihydrate was added and the resulting solution was kept at 60°C. Then, in this solution,
50ml of sodium hydroxide aqueous solution made by dissolving 320g of sodium hydroxide in 1β water! Add pl+ to 12.0
Adjusted to. Next, 14.4 g of anhydrous glucose was added to generate cuprous oxide particles.

Next, after cooling this solution to 50°C, 35 mf of hydrazine hydrate (80%) was added, and the mixture was heated to 70°C for 20 minutes.
The temperature was raised to 1, and the reaction was carried out for 60 minutes.

After filtering the produced fine copper powder, vacuum drying is performed at 90°C.
Spherical copper powder with 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, and 0
．． Adding 811 g of tartaric acid l-I) umnihydrate;
The resulting solution was kept at 60°C. Next, 70ml of a sodium hydroxide aqueous solution in which 320g of sodium hydroxide was dissolved in 1R of water was added to this /8 liquid. The pH was adjusted to 12.0 by adding []. Next, 14.4 g of anhydrous glucose was added to generate cuprous oxide particles.

Next, after cooling this solution to 50°C, 35mj2 of hydrazine hydrate (80%) was added, and the solution was heated to 70°C over 20 minutes.
The temperature was raised to °C and the reaction was carried out for 60 minutes.

The generated steel machine! 5) After filtering the powder, vacuum drying was performed at 90°C to obtain spherical copper↑5] with a particle size of 3.1 μm±0.3 μm.

Comparative Example 1 40g of copper sulfate pentahydrate was added to 320mI! dissolved in water,
0.811 g of tartaric acid (IJ) was added and the resulting F1'8Wi was maintained at 60°C. this? ′
? (160g of sodium hydroxide in 1f of water in liquid I)
Add 70cc of dissolved sodium hydroxide aqueous solution to p
H was adjusted to 11.0. Next, anhydrous glucose 14,4
g was added, but no cuprous oxide powder was produced. Next, this solution was heated to 70°C and hydrazine hydrate (80%
) When 35 mf was added, intense foaming occurred. Thereafter, it was allowed to react for 60 minutes.

After filtering the produced copper fine powder, vacuum drying was performed at 90°C, and copper powder with a particle size of 0.05 to 0.2 μm was obtained.

Comparative Example 2 40g of copper sulfate pentahydrate was dissolved in 320ml of water,
．． 811 g of sodium tartrate dihydrate was added and the solution was kept at 60°C. To this solution, 100 cc of a sodium hydroxide aqueous solution prepared by dissolving 160 g of sodium hydroxide in IJ2 water was added to adjust the pH to 12.0.

This solution was then cooled to 25°C and hydrazine hydrate (8
When 0%) was added, intense foaming occurred.

After the foaming subsided, the temperature was raised to 70°C over 30 minutes.
The reaction was allowed to proceed for 60 minutes.

After filtering the produced fine copper powder, it was vacuum dried at 90°C to obtain copper powder with a particle size of 0.03 to 0.20 μm.

(Effects of the Invention) According to the present invention, high-grade sized fine copper powder can be obtained from inexpensive raw materials that are easily available industrially, and can be used as raw material copper for copper pesto.
It is extremely useful as such.

Claims (3)

[Claims] (1) A step of precipitating copper hydroxide from an aqueous copper salt solution, a step of reducing the obtained copper hydroxide to cuprous oxide, and then reducing the thus obtained cuprous oxide to metallic copper. A method for producing fine copper powder, characterized in that it is carried out in steps. (2) In the method of producing fine copper powder by reducing a copper salt aqueous solution using a hydrazine-based reducing agent, the pH of the copper salt aqueous solution is adjusted to 12 or higher before adding the hydrazine-based reducing agent, and then the reducing sugar A method for producing fine copper powder, which comprises adding a hydrazine-based reducing agent after the addition of a hydrazine-based reducing agent. (3) The reaction solution before adding the hydrazine reducing agent was
3. The method for producing fine copper powder according to claim 2, wherein the hydrazine-based reducing agent is added after the temperature is adjusted to 0° C. or higher.