JPS61243105A - Production of pulverous silver particles - Google Patents

Abstract

PURPOSE:To produce a pulverous monodisperse silver particles having a narrow grain size distribution by adding a cationic surface active agent into a reactive soln. in the stage of reducing an ammoniac silver nitrate complex soln. by using a reducing agent in a hydrophobic reaction vessel. CONSTITUTION:The ammoniac silver nitrate complex soln. prepd. by adding ammonia water to an aq. silver nitrate soln. is put into the reaction vessel of which the inside surface is made hydrophobic by oil coating, etc. An aq. soln. prepd. by adding the cationic surface active agent such as 'Arkard(R)', 'Esomin(R)', 'Armack(R)' to aq. soln. of grape sugar as the reducing agent for the silver nitrate is then added to the ammoniac silver nitrate complex soln. to reduce and deposit Ag. The Ag having the narrow distribution width of the grain sizes and about 1mum grain size is produced in the monodisperse state.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing fine silver particles.

(Prior art and its problems) Conventionally, as a method for producing silver fine particles, a method has been used in which an ammoniacal silver nitrate complex solution is reduced using glucose as a reducing agent in a hydrophobic reaction tank. However, this method has the drawback that only fine silver particles with a wide particle size distribution in which the precipitated fine particles attract each other and aggregate are obtained.

(Objective of the Invention) The present invention has been made to solve the above-mentioned drawbacks, and aims to provide a method for producing fine silver particles having a narrow dispersed particle size distribution.

(Means for Solving the Problems) The present invention provides a method for producing silver fine particles by reducing an ammoniacal silver nitrate complex solution using a reducing agent in a hydrophobic reaction tank. This method is characterized in that monodispersed silver particles are obtained by adding an agent.

The reason why the inner surface of the reaction tank is kept hydrophobic in the production method of the present invention is that when the inner surface of the reaction tank is hydrophilic, the precipitation reaction occurs on the wall of the container, so only aggregated silver particles with a wide particle size distribution can be obtained. This is because by keeping the inner surface of the reaction tank hydrophobic, the precipitation reaction can occur uniformly in the aqueous solution.

Furthermore, the reason for adding a cationic surfactant to the reaction solution is to reduce the ammoniacal silver nitrate complex solution so that the silver fine particles precipitated in the aqueous solution do not aggregate and maintain a monodisperse state. .

In the present invention, methods for keeping the inner surface of the reaction tank hydrophobic include oil coating, surfactant coating, Teflon coating, etc. Cationic surfactants added to the reaction solution include Alucard, Esomin, Armac, and Surflon. S-121, Duomin, etc.

Examples of the present invention will now be described.

(Example 1) 50 g of Grape F is dissolved in 300 ml of water at 50° C., 1 Oml of the cationic surfactant Esomin is added to this solution, and the mixture is stirred in a Teflon-coated beaker. Also, in another beaker, add 10 g of silver nitrate to 20 m
I! of water, and add 8 m of 28% ammonia water to this.
1 to obtain an ammoniacal silver nitrate complex solution, which is gradually added to the above glucose + esomine solution. The obtained silver particles were thoroughly washed with water by decantation, and subjected to particle size distribution measurement and electron microscopic observation.

As a result, the silver fine particles had an average particle diameter of 1.2 μm, a narrow particle size distribution as shown in the figure, and a substantially spherical and monodisperse shape.

(Example 2) 100 g of glucose was dissolved in 500 ml of water at 50°C, and 1.7 m of the cationic surfactant Duomin was added to this solution.
j! Add and stir in a beaker coated with silicone oil. Further, in another beaker, 25 g of silver nitrate is dissolved in 50 ml of water, and 20 ml of 28% aqueous ammonia is added thereto to obtain an ammoniacal silver nitrate complex solution, which is gradually added to the above glucose + Duomin solution.

The obtained silver particles were thoroughly washed with water by decantation, and subjected to particle size distribution measurement and electron microscopy observation.

As a result, the silver fine particles had an average particle diameter of 0.9 μm, had a narrow particle size distribution as shown in the figure, had a substantially spherical shape, and were monodispersed.

(Conventional Example) 70 g of glucose is dissolved in 400 ml of water at 50° C., and this solution is stirred in a Teflon-coated beaker. In another beaker, add 15g of silver nitrate to 30ml!
of water, add 13 ml of 28% ammonia water to obtain an ammoniacal silver nitrate complex solution, and gradually add this to the glucose solution. The obtained silver particles were thoroughly washed with water by decantation, and subjected to particle size distribution measurement and electron microscopic observation. As a result, the silver particles were agglomerated with an average particle size of 6.2 μm and a wide particle size distribution as shown in the figure.

(Effects of the Invention) As is clear from the above explanation, the production method of the present invention is a method for producing silver fine particles by reducing an ammoniacal silver nitrate complex solution using a reducing agent in a hydrophobic reaction tank. , by adding a cationic surfactant to the reaction solution,
Since it is possible to produce fine root nodules with a narrow, monodisperse particle size distribution that could not be obtained using conventional methods, it can be said to be an epoch-making method that can replace conventional production methods.

[Brief explanation of drawings]

The figure shows the results of measuring the particle size distribution of each fine silver particle using a light transmission type particle size distribution measuring device, with the horizontal axis representing the particle diameter and the vertical axis representing the cumulative percentage.

Claims (1)

[Claims] In a method for producing silver fine particles by reducing an ammoniacal silver nitrate complex solution using a reducing agent in a hydrophobic reaction tank, monodispersed silver fine particles are produced by adding a cationic surfactant to the reaction solution. A method for producing silver fine particles characterized by obtaining