KR100982042B1 - Method of manufacturing silver powder - Google Patents

Abstract

The present invention relates to a method for producing silver powder, wherein the method for producing silver powder is a mixed solvent of a solvent selected from the group consisting of water and ketones, alcohols and combinations thereof (here ketones, alcohols, and Preparing a silver salt solution by dissolving silver salt by adding a silver salt to a solvent selected from the group consisting of a combination thereof. Adding an alkali metal hydroxide to the silver salt solution to react the silver salt with the alkali metal hydroxide to precipitate the silver powder; Filtering, washing and drying the silver precipitated solution to obtain silver powder.

The production method of the silver powder of the present invention can reduce the manufacturing cost and simplify the manufacturing process by not using a reducing agent, it is possible to produce a silver powder having a uniform particle size distribution and shape.

Silver, reducing agent, silver salt, alkali metal hydroxide

Description

Manufacturing method of silver powder {METHOD OF MANUFACTURING SILVER POWDER}

The present invention relates to a silver powder manufacturing method, and more particularly, it is possible to reduce the production cost and simplify the manufacturing process by not using a reducing agent, and to produce a silver powder having a uniform particle size distribution and shape. It relates to a manufacturing method of.

Silver powder is a conductive filler for the production of silver pastes used in electronic components where reliability is important, such as thick film integrated circuits, printed wiring circuits, and thermosetting conductive pastes in the electronics industry. As is necessary material. The silver powder used for this purpose is a 99.99% pure silver ingot, which is a precious metal, which is expensive. Therefore, the recovery rate must be high, and the particle shape of the manufactured silver powder must be spherical and uniform and have an average particle size. The particle size distribution width should be narrow to 0.5 to 1 μm.

Conventional methods for producing silver powders include mechanical methods, liquid phase precipitation methods, gas phase reaction methods, wet reduction methods, and the like. In order to produce good silver powder, it is necessary to precisely control temperature, concentration, reaction rate, pH, etc., and existing processes are difficult to precisely control these reaction conditions. In addition, in the production method of the silver powder, the silver ingot having a purity of 99.99% is dissolved in nitric acid, and then the pH is adjusted to 10 to 11 by adding ammonia water, and reduced or precipitated by adding organic reducing agents such as formaldehyde, hydroquinone, hydrazine, and ascorbic acid. Or by injecting hydrogen gas into an autoclave after dissolving a silver ingot having a purity of 99.99% in nitric acid.

However, the method of preparing by adding organic reducing agents such as formaldehyde, hydroquinone and hydrazine in the silver powder manufacturing method, when the reduction and precipitation of silver ions (silver ions) contained in the solution, the reducing power is strong, the reduction reaction is rapid It is difficult to control the particle size and particle shape of the silver powder, and the particle size of the reduced and precipitated silver particles becomes coarse and coagulation occurs.In addition, these reducing agents are toxic to the human body. There is a disadvantage that the treatment cost of the generated wastewater is high.

In addition, the production of silver powder using an autoclave requires a lot of equipment cost and equipment cost. Also, since the reduction reaction proceeds at a high speed, it is impossible to control the particle size and particle form, and the aggregation phenomenon of the particles is very severe. There is this.

An object of the present invention is to provide a manufacturing method of silver powder that can reduce the production cost and simplify the manufacturing process by using a reducing agent, and can produce silver powder having a uniform particle size distribution and shape.

However, technical problems to be achieved by the present invention are not limited to the above-mentioned problems, and other technical problems will be clearly understood by the average technician from the following description.

In order to achieve the above object, an embodiment of the present invention is a mixed solvent of a solvent selected from the group consisting of water and ketones, alcohols and combinations thereof (here, the group consisting of ketones, alcohols and combinations thereof for water) Volume ratio of the solvent selected from is greater than 1) by adding a silver salt to dissolve to prepare a silver salt solution; Adding an alkali metal hydroxide to the silver salt solution to react the silver salt with the alkali metal hydroxide to precipitate the silver powder; It provides a method for producing silver powder comprising the step of obtaining a silver powder by filtering, washing and drying the solution in which the silver powder is precipitated.

Other specific details of embodiments of the present invention are included in the following detailed description.

The production method of silver powder according to the present invention does not use a reducing agent to reduce the manufacturing cost and simplify the manufacturing process, there is an advantage to produce a silver powder having a uniform particle size distribution and shape.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Conventionally, reducing agents such as formaldehyde, hydroquinone, hydrazine, and ascorbic acid were used to prepare silver powder by reducing silver ions in preparing silver powder. However, when such a reducing agent is used, it is difficult to precisely control the reaction conditions in the manufacturing process because of the strong reducing power and the reduction reaction proceeds rapidly, thereby reducing the reproducibility and productivity of the silver powder. There was a problem.

In addition, the reducing agent is very Not only is it harmful but it is very expensive to treat wastewater generated during the manufacturing process.

In addition, conventionally, the use of the autoclave during the manufacturing process of the silver powder, such a manufacturing method has a problem that takes a lot of equipment costs and equipment costs.

Since the production method of the silver powder according to the present invention does not use a reducing agent at all, it is harmless to the human body, can reduce the waste water treatment cost, and can uniformly control the reaction conditions in the manufacturing process. This has the advantage of improving the productivity and reliability of the silver powder. In addition, the production method of the silver powder according to the present invention does not use the autoclave at all, the manufacturing cost is reduced, the manufacturing process is simplified and has the advantage of producing a low-cost silver powder.

The production method of the silver powder of the present invention is a mixed solvent of a solvent selected from the group consisting of water and ketones, alcohols and combinations thereof (wherein the solvent selected from the group consisting of ketones, alcohols and combinations thereof for water) Volume ratio is greater than 1) to add a silver salt to dissolve to prepare a silver salt solution; Adding an alkali metal hydroxide to the silver salt solution to react the silver salt with the alkali metal hydroxide to precipitate the silver powder; Filtering, washing and drying the silver precipitated solution to obtain silver powder.

First, a mixed solvent of water and a solvent selected from the group consisting of ketones, alcohols and combinations thereof (wherein the volume ratio of the solvent selected from the group consisting of ketones, alcohols and combinations thereof with respect to water is greater than 1). Silver salt is added to dissolve to prepare a silver salt solution.

The mixed solvent is preferably a solvent selected from the group consisting of water, ketones, alcohols and combinations thereof in a volume ratio of 1: 2 to 1: 9, more preferably 1: 2 to 1: 3. . When it is out of the range of the volume ratio, silver powder is not produced, which is not preferable.

Acetone, ethyl methyl ketone, methyl ketone, etc. are mentioned as said ketone solvent. Ethanol, methanol, isopropanol, etc. are mentioned as said alcohol solvent.

As said silver salt, silver nitrate, silver chloride, silver sulfide, or these can be mixed and used.

The silver salt added to the mixed solvent is preferably contained in 0.5 to 2.0M with respect to the mixed solvent, more preferably 0.8 to 1.8M. If the content of the silver salt is less than 0.5M may not generate an appropriate amount of silver powder, if the amount exceeds 2.0M there is an inefficient problem because the amount of the silver powder is no longer increased .

An alkali metal hydroxide is added to the prepared silver salt solution to react the silver salt with the alkali metal hydroxide to precipitate the silver powder. That is, as the alkali metal hydroxide is added to the silver salt solution, Ag ₂ O and AgO, which are Ag-based complex oxides, are produced. In the present invention, the silver powder may be prepared from the Ag-based complex oxides without further processing. There is an advantage that can be simplified.

The silver salt and alkali metal hydroxide is preferably reacted for 1 to 3 hours. When the reaction time between the silver salt and the alkali metal hydroxide is less than 1 hour, the precipitation of the silver powder does not occur well, and when it exceeds 3 hours, the amount of precipitation of the silver powder does not increase any more than 3 hours. It is pointless to let.

The alkali metal hydroxide is preferably used in an amount of 0.5 to 5 moles (mole) per 1 mole of silver salt. When the amount of the alkali metal hydroxide is less than 0.5 mol It is not preferable because the Ag-based complex oxide is not formed, and when it exceeds 5 mol, the reaction of silver salt and alkali metal hydroxide is inhibited, which is not preferable.

The alkali metal hydroxide is used in an aqueous solution of 20 to 30% by weight.

Specific examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide and the like.

In the present invention, a dispersant may be further added to the silver salt solution.

The dispersant plays a role in that the dispersion is well performed by reducing the particle size of the silver powder. The dispersant is not particularly limited as long as it can easily disperse silver in the solution, but may be polyvinyl based such as polyvinyl alcohol (PVA), polyvinyl butyral (PVB), and polyvinyl pyrrolidone (PVP). (Polyvinyl-based) polymers, glucose (Glucose), sodium dodecyl sulfate (SDS), sodium citrate (SC; Sodium Citrate) and dispersing agents, such as one or two or more of them are dissolved in an aqueous solution. Among them, polyvinyl vinylpyrrolidone can be preferably used.

The dispersant is preferably added so that the silver salt is contained in an amount of 0.1 to 10% by weight based on the total amount of the mixture including the silver salt solution and the dispersant. If the content of the dispersant is within the above range, the uniformity of the silver powder is the best.

Subsequently, the silver precipitated solution is filtered, washed and dried to obtain silver powder. The silver powder produced according to the invention has a dumbbell shape.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention and the present invention is not limited to the following examples.

(Example 1)

Ultrapure water and acetone were mixed in a volume ratio of 1: 2 to prepare a mixed solvent, and silver nitrate was added to prepare a 1 M silver nitrate solution. In addition, 100 ml of an aqueous sodium hydroxide solution was prepared by dissolving 25 wt% sodium hydroxide in ultrapure water.

The silver nitrate solution was stirred at a constant rate at room temperature, and the prepared sodium hydroxide solution was added to the silver nitrate solution for 20 minutes using a metering pump. The content of added sodium hydroxide was 30 g. In the reaction process, the temperature may increase during the production of the silver powder, which may be dangerous in experiments. At this time, the temperature is maintained between 20 and 50 ° C.

After the aqueous sodium hydroxide solution was added, the mixed solution of silver nitrate was stirred for 50 minutes.

The stirred silver nitrate precipitated silver powder precipitated in the mixed solution was washed several times using ultrapure water and ethanol, filtered and dried at 85 ℃ for 12 hours.

(Example 2)

The same procedure was followed as in Example 1 except that 5 wt% PVP K-90 was dissolved in the silver nitrate solution.

(Example 3)

Ultrapure water and acetone were mixed in the same manner as in Example 1 except that the volume ratio was 1: 3.

(Example 4)

1.5 M silver nitrate was carried out in the same manner as in Example 1 except for preparing a mixed solution.

(Example 5)

Ultrapure water and acetone were mixed in a volume ratio of 1: 3, and then a mixed solution was prepared, except that 1.5 M of silver nitrate mixed solution was prepared in the prepared solution.

(Example 6)

2M silver nitrate was carried out in the same manner as in Example 1 except for preparing a mixed solution.

(Comparative Example 1)

Ultrapure water and acetone were mixed in a volume ratio of 3: 1, and then a mixed solution was prepared, except that 2M silver nitrate mixed solution was prepared in the prepared solution.

(Comparative Example 2)

Ultrapure water and acetone were mixed in a volume ratio of 3: 1, and then a mixed solution was prepared. The same process as in Example 1 was performed except that 1.5M of silver nitrate was mixed in the prepared solution.

(Comparative Example 3)

The same procedure as in Example 1 was carried out except that ultrapure water and acetone were mixed at a volume ratio of 3: 1.

Silver powder analysis by scanning electron microscope

1 to 9 are photographs of silver powders prepared according to Examples 1 to 6 and Comparative Examples 1 to 3 using a scanning electron microscope.

As shown in Figures 1 to 6, it can be seen that the silver powder prepared according to Examples 1 to 6 has the form of a dumbbell. However, as shown in FIGS. 7 to 9, it can be seen that silver powder was not produced by the method for preparing silver powders according to Comparative Examples 1 to 3.

From this it can be seen that the manufacturing process of the silver powder prepared according to the present invention has the advantage of reducing the manufacturing cost and simplifying the manufacturing process without using a reducing agent.

Particle size analyzer  Silver Powder Analysis

Tables 1 and 2 show the results of analyzing the silver powder prepared according to Examples 1 to 7 using a particle size analyzer.

Example One 2 3 4 5 6 Silver particle size (㎛) D50 =
10-14 D50 =
4-8 D50 =
10-14 D50 =
10-14 D50 =
10-14 D50 =
10-14

As shown in Table 1, it can be seen that the silver powder prepared according to Examples 1 to 7 has a uniform particle size. However, in the manufacturing method of silver powder which concerns on Comparative Examples 1-3, silver powder was not produced and silver particle size could not be measured. From this it was confirmed that the silver powder prepared according to the present invention has a uniform particle size and shape.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

1 to 6 are photographs taken through a scanning electron microscope of the silver powder prepared according to Examples 1 to 6 of the present invention.

7 to 9 are photographs of silver powders prepared according to Comparative Examples 1 to 3 through a scanning electron microscope.

Claims (9)

The silver salt is mixed with a mixed solvent of water and a solvent selected from the group consisting of ketones, alcohols and combinations thereof (wherein the volume ratio of the solvent selected from the group consisting of ketones, alcohols and combinations thereof with respect to water is greater than 1). Adding to dissolving to prepare a silver salt solution; Adding an alkali metal hydroxide to the silver salt solution to react the silver salt with the alkali metal hydroxide to precipitate the silver powder; And Filtrating, washing and drying the solution in which the silver powder is precipitated to obtain a silver powder. The method of claim 1, The volume ratio of the solvent selected from the group consisting of water, ketones, alcohols and combinations thereof is 1: 2 to 1: 9. The method of claim 1, The content of the silver salt added to the mixed solvent is 0.5 to 2.0M method of producing a silver powder. The method of claim 1, The alkali metal hydroxide is a method for producing silver powder is used in an amount of 0.5 to 5 moles per 1 mole of silver salt. The method of claim 1, The time for the reaction of the silver salt and alkali metal hydroxide is 1 to 3 hours to produce a silver powder. The method of claim 1, The silver salt solution is a method of producing a silver powder further comprises a dispersant. The method of claim 6, The dispersant is a polyvinyl-based polymer, glucose, sodium dodecyl sulfate, sodium citrate, and a method of producing a silver powder is selected from the group consisting of a combination thereof. The method of claim 7, wherein The polyvinyl polymer is polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), and a method of producing a silver powder is selected from the group consisting of these. The method of claim 6, The dispersing agent is a method for producing silver powder is added so that the silver salt is contained in an amount of 1 to 10% by weight based on the total amount of the mixture containing the silver salt solution and the dispersant.

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