SU1477240A3 - Method of producing silver powder - Google Patents

Abstract

The invention relates to powder metallurgy. The purpose of the invention is to increase the efficiency of the process. To the solution containing the colloid-forming substance and reducing agent, an aqueous solution of silver nitric acid partially converted to the complex is continuously added. Gum arabic, gelatin, polyethylene glycol or polyvinyl alcohol are used as colloid-forming substances. Unsaturated alcohols such as ethylene or acetylene, in particular, alkenols or alkynols, are used as reducing agents. To reduce the rate of reduction, rhodanine and its derivatives are used as a complexing agent. Water is used as a solvent. The process temperature is preferably in the range of 30 ° C — the boiling point of the solvent. The method allows to obtain silver powder with a particle size of 0.01-0.1 microns, does not require an elevated temperature, and provides chemical savings. Processing the powder with the resulting particle size is not difficult. 6 hp f-ly.

Description

one

The invention relates to powder metallurgy, in particular, to methods for producing silver powder with a high specific surface area of particles, which is used as a pigment in conductive pastes, varnishes and adhesives.

The purpose of the invention is to increase the efficiency of the process of obtaining a powder with a particle size of 0.1-1 µm.

Example 1. A solution of 40 g / l AgNOj, 1 g / l polyvinyl alcohol

and 0.08 g / l of P-dimethylamino-benzimidrodamin was added to 16 g / l of ascorbic acid solution. A highly dispersed precipitate is obtained with a particle size of 0.1 μm.

Example 2. A solution of 200 g / l AgN03 is added to 80 g / l of ascorbic acid solution containing 5 g / l of polyvinyl alcohol and 0.3 g / l of P-dimethylamino-benzylidene rodarodine. Silver Powder Grain Size

4i

 1 to

4i

 CM

is 1 micron. A precipitate is formed with a spongy structure.

Example 3 A solution of 200 g / l AgNO is added to 80 g / l of a solution of ascorbic acid containing 10 g / l of gelatin and 0.5 g / l of 1-nitro-2-naphthol. A well dispersed, slowly precipitating precipitate with a particle size of 1 µm is obtained, which changes its dark gray color to sand after several hours of storage.

Example 4. A solution of 200 g / l of AgN03 and 5 g / l of polyvinyl alcohol is added to an 80 g / l of ascorbic acid solution containing 10 g / l of gelatin and 1, 0 g / l of 1-nitroso-2-naphthol. A fine, dispersed, slowly precipitating silver powder with a grain size of less than 1 micron is obtained.

Example 5. A solution of 400 g / l AgNO and 5 g / l polyvinyl or alcohol is added to 160 g / l ascorbic acid solution containing 10 g / l gelatin and 1 g / l nitroso-R salt. A well dispersed silver powder with a grain size of 1 μm is obtained.

Example 6. To a solution of 400 g / l AgNO. , 40 g / l of gum arabic and 1 g / l of 1-nitroso-2-naphthol are added a mixture of propargyl alcohol and water (1: 1 ratio). Dark gray, slowly precipitated; silver powder with a grain size less than 1 µm. Example 7. In a solution of 200 g / l AgNO, 10 g / l gelatin and 1 g / l nitroso-R salt are added at 25 ° C out of

allyl alcohol and water (1: 1 ratio). A fine, slowly precipitating silver powder with a grain size of 0.1 µm is formed.

The technology of the proposed method is based on recovery in a single stage, in which an aqueous solution partially converted into silver nitric acid complex is continuously added to a solution containing a protective colloid and a reducing agent with constant stirring. Gum arabic, gelatin, polyethylene glycol or polyvinyl alcohol are used as a protective colloid (colloid-forming substance). As a reducing agent, ethylene or acetylene unsaturated alcohols can be used, in particular alkenols, for example

0

50

Q

five

five

allyl alcohol, metal alcohol, crotyl alcohol, oleyl alcohol, lino alcohol or alkynols, for example, prothargyl alcohol, cytronolol. In addition, easily oxidizable organic compounds containing parts of dienol molecules, in particular ascorbic acid, can be used as a reducing agent. To reduce the reduction rate, rhodamine and its derivatives (for example, P-dimethylbenzylidene-rhodamine) or nitrosonaphthol derivatives (for example, 1-nitroso-2-naphthol- and nitro-R, disodium salt) can be used as organic complexing agents. 1-nitroso-2-naphthol-3, 6-sulfonic acids). The solvent used is water, the reducing agent itself or a mixture of water and

reductant in the ratio of 1: 1.

The reaction temperature can vary from room temperature to 120 ° C.

 preferably from 30 ° C to the boiling point of the solvent.

When implementing the described method, the individual components of the solution are metered in an arbitrary sequence. A particularly fine grain size powder is obtained when a mixture of a colloid and a reducing agent is added to the mixture of silver nitrate and complexing agent.

Based on the initial amount of silver nitrate, 5-1 0% of a colloid-forming substance is used (pre- eminently 10-12.5% by weight) and 0.01% by weight of a complexing agent (mainly 0.07-0.5 wt.%}. The process is carried out with mixing (ultrasonic or mechanical).

The shape of the particles of the obtained powder is predominantly isothermal. To obtain a laminar structure, additional processing is carried out in a ball or vibratory mill by wet grinding. The use of the aquatic environment contributes to environmental protection, does not require the use of elevated temperature (the process is carried out at temperatures below 1 00 ° C),

Using the proposed method saves chemical reagents and reduces energy costs. Processing the powder with a particle size of 0.1-1 µm is not difficult. The resulting powder can

used in the electronics industry.

Claims (3)

Invention Formula / one . The method of obtaining silver a powder, which includes chemical precipitation of the powder by reducing silver from a nitrate solution at 4. The method according to paragraphs. 1 -3, about tl and h ayu yi, and with the fact that gum arabic or gelatin in an amount of 10 wt.% With respect to silver nitrate is taken as a colloid-forming substance. 5. The method according to paragraphs. 1-3, about tl and h a- yu u and with the fact that as a count In the absence of a colloid-forming substance, a substance that forms a substance that takes a mixture, which differs in that gelatins with 2.5 wt.% polyvinyl in order to increase the efficiency of the process of obtaining a powder with a particle size of 0.1-1 µm, the reduction is carried out from an aqueous solution of silver nitrate and with the complexing agent introduced into it. 2. A method according to claim 1, characterized in that an unsaturated alcohol, an alkeneol or an alkynol is taken as the reducing agent. 3. The method according to claim. Characterized in that a dienol type compound is taken as the reducing agent, predominantly L-ascorbic acid.25 wearing to silver nitrate. alcohol or polyethylene glycol with respect to silver nitrate. 6. Method according to paragraphs. 1-5, differing a-yu t and in that dimethylamino-benzidylenorodamine is used as a complexing agent in an amount of 0.02 wt.% Relative to silver nitrate. 7. Method according to paragraphs. 1-5, about tl and h ayu yi and so that, as a complexing agent use 1-nitroso-2-naphthol or a salt of nitroso-R in an amount of 0.5 wt.% By