JPS63274706A - Production of metallic fine powder - Google Patents

Abstract

PURPOSE:To produce metallic fine powder having the desired grain size under high yield by further adding metallic ion, reducing agent and pH conditioner after executing reduction reaction by adding reaction initiator to mixed water solution of the metallic ion, reducing agent and complexing agent. CONSTITUTION:The complexing agent water solution (citric acid, etc., about 0.01-1mol./l concn.) adjusted to the prescribed pH, is heated to >=about 50 deg.C and the metallic salt water solution (Ni, copper, etc.,) and the reducing agent water solution (sodium hypophosphite, etc.,) are added at suitable quantity and further a little quantity of the reaction initiator is added to execute reduction reaction of the metal. At the time of completing the reaction, further as the same way as the above, the metallic salt water solution and the reducing agent water solution are dripped at the fixed dripping speed to continue the reaction and pH in the solution during reaction is adjusted. When the dripping and the reaction complete, the solution is filtrated and after repulping-washing the filtrated residue, it is dried. By this method, the metallic powder having the desirable grain size and extremely stable quality with a little impurity is produced under good productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing fine metal powder, and particularly to a method for producing fine metal powder having a desired particle size in high yield.

[Prior Art] Conventionally, chemical methods and physical methods are known as methods for producing fine metal powder.

Chemical methods include a gas phase method in which the metal is heated to volatilize and metal vapor is condensed in a reducing atmosphere, and a precipitation method in which a reducing agent is added to a metal salt solution to obtain metal powder (Japanese Patent Laid-Open No. 60-23
No. 8406), etc. However, the gas phase method requires expensive equipment, low productivity, and is not economical, and the precipitation method has a low chemical utilization rate, consumes a large amount of pure water, and the liquid composition changes drastically between the initial and final stages of the reaction. Therefore, the metal powder produced is not homogeneous, and the particles produced are too fine (for example, 0
．． O1~0.03 p-s) Recovery work becomes difficult and productivity is low (neither is practical.

Among other chemical methods, there is a metal salt solution electrolysis method, which is mainly used to produce fine metallic copper powder, but this method does not allow oxygen or electrolyte to mix into the fine metallic copper powder.
The particle size is irregular and large (for example, 10~al(IILs)
) get something. In addition, there is a method of reducing an aqueous solution of copper oxide and cuprous oxide, but with this method, particles with high purity and a particle size of about 1 mm can be obtained, but particles with any particle size can be obtained according to the requirements. There are drawbacks that make it difficult.

On the other hand, physical methods include mechanically crushing two metals;
There are methods such as WA mist cooling of molten metal, but it is difficult to obtain fine powder in either method, and the powder surface is oxidized, resulting in poor conductivity and a wide particle size distribution. In order to obtain this, operations such as classification are required.
As a result, it becomes expensive.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned prior art, and uses an aqueous chemical reduction method to obtain particles with a desired a diameter within a defined particle size range and with good quality. The object of the present invention is to provide a method for producing extremely stable metal fine powder with few impurities with high productivity and high yield.

[Means for Solving Problem 171] Namely, the present invention involves adding a reaction initiator to a mixed aqueous solution consisting of metal ions, a reducing agent, and a complexing agent to cause a reduction reaction, and then adding metal ions, The present invention relates to a method for producing fine metal powder, which is characterized by adding a reducing agent and a 911 regulator.

Hereinafter, one aspect of the present invention will be explained in detail.

In the method for producing fine metal powder according to the present invention, in the first step, a complexing agent aqueous solution adjusted to a pH at which metal ions easily undergo a reduction reaction is heated at 50°C or higher, preferably at 60°C or higher.
Appropriate amounts of a pre-dissolved metal salt aqueous solution and a reducing agent aqueous solution are added to the complexing agent aqueous solution after heating to the boiling point, and a small amount of a reaction initiator is further added to initiate a metal reduction reaction.

A wide range of metal ions can be used without particular limitation, such as nickel ions, copper ions, iron ions, cobalt ions, silver ions, gold ions, etc., and fine metal powders corresponding to each metal ion are used. You can get it, but
Among these, the di-linker ion and the copper ion are particularly common.

Moreover, two or more types of metal ions can be used as the metal ions, and in this case, an alloy metal fine powder can be obtained. Furthermore, the metal ion can be used to obtain Xl-P, Ni-8 alloy, etc. by selecting the reducing agent used.

Complexing agents include citric acid and apple S6 lactic acid.

Oxycarboxylic acid or its alkali metal salts such as tartaric acid and gluconic acid, ammonium salts such as ammonia or ammonium sulfate and ammonium chloride, amine compounds such as ethylenediamine, ethylamine and EDTA, birophosphoric acid and hexametaphosphoric acid.

phosphate compounds such as alkali metal salts of tripolyphosphate;
1 selected from amino acids such as glycine and cyanide compounds,! ! The above compounds are used.

The phi of the complexing agent aqueous solution is adjusted to a range determined by the type of reducing agent used in one reaction, for example 0.

When hypophosphite is used as the reducing agent, the pH is adjusted to 4 to 8 degrees, and when an alkali boron hydride, hydrazine or formalin is used, the pH is adjusted to 8 to 13.

The appropriate concentration of the complexing agent aqueous solution is 0.1)1 to 1 mol/R; If the value is less than l mol! When /R is exceeded, more complexing agent than necessary is used, which becomes uneconomical.

In the method of mixing metal ions, reducing agents, and complexing agents in step 3 of the present invention, appropriate amounts of metal salts and reducing agents may be added and dissolved in a complexing agent solution in advance.

Alternatively, an appropriate amount of a metal salt aqueous solution and a reducing agent aqueous solution prepared separately may be added to the complexing agent solution, but the method is not necessarily limited to these methods.Next, a small amount of a reaction initiator may be added. and start the reaction.

Then, in the second step, after the reaction has subsided, 1
For example, after the bubbling phenomenon has subsided, the same metal salt aqueous solution and reducing agent aqueous solution are added dropwise at a constant dropping rate to continue the reaction. During one reaction, the pH of the solution is adjusted to pl+ by an automatic adjustment device or a similar method. Potassium hydroxide, sodium hydroxide aqueous solution, etc. are added as a regulator to maintain the initial pH.

After the dropping is completed and the reaction is completed, the solution is filtered, the filtration residue is repulped and washed, and then dried to obtain a fine metal powder.

In the present invention, the metal salt used is a compound having the target metal ion, for example, in the case of nickel ions, nickel salts such as nickel chloride, nickel sulfate, and nickel nitrate, and in the case of copper ions, nickel salts such as nickel chloride, nickel sulfate, and nickel nitrate; Copper salts such as copper and silver nitrate are used, and in the case of silver ions, silver cyanide, silver nitrate, etc. are used.

Since the higher the concentration of the metal salt aqueous solution, the more economical and desirable it is, a concentration close to the solubility is used. Further, the amount of the metal salt added is calculated empirically based on the desired particle size of the metal fine powder.

The reducing agent is alkali hypophosphite, alkali boron hydride,
Alkylamine borane, hydrazine, formalin, monosaccharides, polysaccharides, tartaric acid, etc. are used, and these may be appropriately selected and used depending on the type of metal ion.

The higher the concentration of the reducing agent aqueous solution is, the more economical and desirable it is.

In the present invention, the ratio of the amount of the metal salt to the reducing agent used varies depending on the reducing agent used.

First, regarding nickel salt and reducing agent, when using primary phosphite alkali as reducing agent, nickel salt l■oR
Alkali hypophosphite is 2.0 to 3.0 to reduce
■Requires oR.

In the case of alkali boron hydride, the concentration is 1.5 to 2.5 times that of nickel salt for the same reason! In the case of hydrazine, use 3 to 4 times the mall.

Next, regarding the copper salt and reducing agent, when hydrazine is used as the reducing agent, the moR is 1 to 2 times that of the copper salt, and when formalin is used as the reducing agent, the moR is 2.5 to 3.5 times that of the copper salt.
R is required.

Regarding silver salt and reducing agent, in the case of hydrazine, 2
~3 times ■oR, 1.5 to 3 times ■oR for formalin
, in the case of alkali boron hydride, 1 to 1.5 times l1of
! , for monosaccharides and polysaccharides, 0.5 to 2 times l1Of! is necessary.

Sodium hydroxide and potassium hydroxide are usually used as pH adjusters, and the amount used is just the amount necessary to maintain the initial PL, and is generally 2 to 6 times the amount of the metal salt.
! is used.

Any reaction initiator can be used as long as it induces the reduction reaction in the present invention, and specific examples thereof include noble metal ions and their colloids, alkali boron hydrides, and the like.

The amount of reaction initiator added is 1/100 of the generated metal fine powder.
It is preferably 0 or less.

The reaction temperature is usually 50° C. or higher, preferably 60° C. to the boiling point. If it is lower than 50° C., the reaction rate is slow and the productivity is lowered, which is not preferred.

The reaction solution contains metal salts, reducing agents, PO regulators, etc., but if necessary, protective colloids such as gelatin or gum arabic, physical property improvers, etc. may be added.

After the reaction is completed, fine metal powder can be obtained by filtering, repulping, washing, and drying.

In this case, depending on the type of fine metal powder, for example, if it is easily oxidized such as fine copper powder, it may be necessary to separate the fine powder from the reaction liquid, wash it with repulp, and then dry it in a vacuum dryer to prevent oxidation. Desirable, and may also be washed and dehydrated using an organic solvent such as alcohol or acetone;
It is also possible to apply rust prevention treatment using a rust preventive agent before drying.

By the production method explained above, it is possible to obtain fine metal powder having a desired particle size within a particle size range, but especially when the average particle size is It is possible to easily obtain fine metal powder in the range of 0.05 to Igm.

[Function] In the first step of the method for producing fine metal powder of the present invention, a reduction reaction is induced by adding a reaction initiator to a mixed aqueous solution consisting of metal ions, a reducing agent, and a complexing agent. Metal nuclei are formed, and then in the second step, metal ions and reducing agent are gradually added dropwise to the reaction system while adjusting the pit, so that the metal ions and reducing agent in the reaction solution are always kept at a constant concentration. Since the reaction proceeds while the particles are retained, it is presumed that the metal core can be gradually lengthened by 11J, and fine metal particles having a desired particle size within a controlled particle size range can be obtained in high yield.

[Example] Hereinafter, the present invention will be explained in more detail by showing Examples and Comparative Examples.

Example 1 500ml of aqueous H solution was prepared by adding and dissolving IOg of Nilacel sulfate and 12g of sodium hypophosphite into 200ml of each complexing agent aqueous solution shown in Table 11). 0.1 g of sodium diborohydride powder, which had been placed in a glass beaker and heated to 90° C. on a hot water bath, was added to the above stirring solution.

During the reaction, the solution was pitted using an automatic TA device.
0 g/i' sodium hydroxide aqueous solution was added dropwise, and the initial p.
i (held in

After the reaction has subsided and the foaming has decreased.

l■oR/R nickel sulfate aqueous solution and 2.5■of! 1
1.6R of each 100g of primary sodium hypophosphite aqueous solution1)
During the 0 reaction, the p of the solution was added dropwise to the above reaction solution at a rate of
As above, H was kept constant at all times. After 0 drops and no bubbling stopped, the solution was filtered, the RP-passed material was washed twice with water, and then dried in a vacuum dryer to form a fine powder of phosphorus-nickel alloy. I got it. Table 2 shows the yield of fine powder of the obtained Phosphorus m=.Nkel alloy, the reaction yield, the average particle diameter measured by SEM photography, and the specific surface area of the particles measured by surface area measurement using the BET method.

Table 1 Table 2 Example 2 Nickel sulfate 53g/j), Sodium hypophosphite 64g
/j), p with a composition consisting of 40 g/i' of sodium tartrate
200 mA' of an aqueous solution of H6,5 was placed in a beaker and heated to 80°C on a hot water bath. Next, an amount of a 20 g/ρ palladium chloride aqueous solution shown in Table 3 was dropped into the aqueous solution while stirring. During the reaction, the pH of the solution was adjusted using an automatic adjustment device.
160g/l) by dropping an aqueous sodium hydroxide solution,
The initial pH was maintained.

After the foaming subsided, lmoR/12 nickel sulfate solution and 2.5 moi)/i) sodium hypophosphite aqueous solution were added dropwise in the amounts shown in Table 3 at a dropping rate of 20 mJ/min. During the reaction, the pH of the solution was kept constant as described above. After the dropping was completed and foaming had ceased, the solution was filtered, and the filtered material was washed twice with pulp water, and then dried in a vacuum dryer to obtain a fine powder of phosphorus-nickel alloy. Yield of fine powder of phosphorus-nickel alloy obtained, reaction yield,
Table 4 shows the average particle diameter measured by SEM photography and the specific surface area of the particles measured by surface area measurement using the BET method.

Table 3 (Note) 1 indicates a comparative example.

Table 4 (Note) 1 (Shows a seven-bite case.

Example 3 Nickel sulfate 53g/i), sodium borohydride 11g/i), ethylenediamine 15g/j! A 200 mj aqueous solution of PU 9.0 having a composition consisting of 20g#! An aqueous palladium chloride solution 1IIR was added dropwise to the above solution under stirring. During the reaction, the pH of the solution was adjusted to 160 using an automatic adjustment device.
g # of sodium hydroxide aqueous solution was added dropwise to maintain the initial pH.

After the foaming subsided, a solution of nickel sulfate R/R and a 1.5soi'/i' aqueous sodium borohydride solution (500 ha each) were added dropwise at a rate of 51 p/min. During the reaction, the pH of the solution was kept constant in the same way as above.After the addition of one drop was completed and the bubbling stopped, the reaction solution was filtered, and the filtered material was washed twice with pulp, and then dried in a vacuum drier. A fine powder of boron-nickel alloy was obtained. The yield of the obtained boron-nickel alloy fine powder was 31.58
g, the reaction yield was 99.6%, the average particle diameter measured by SEM photography was 0.617 zm, and the specific surface area of the particles was 0.92 ■''/g by surface measurement by BET method.

Example 4 An aqueous solution 2001 of 20 g/l of Otsuiel salt, pl+ 9.0 was placed in a beaker, heated to 70°C, and then 1 wol! /R nickel sulfate aqueous solution and 4 moR
/R hydrazine aqueous solution 50s each! ! was added dropwise to the above stirring solution at a rate of 10tj'/min. Also, at the same time as dropping the pre-medicinal solution, 20g/I! Palladium chloride aqueous solution lp
was added.

During the reaction, the pH of the solution was adjusted using an automatic adjustment device, and 160 g
#! An aqueous sodium hydroxide solution was added dropwise to maintain the initial pH.

After the dripping is finished and the foaming has subsided, add l■ol!
/R nickel sulfate aqueous solution and 4 moR/j! Aqueous hydrazine solutions of 500*i' each were added dropwise at a rate of 4 ails/min.

During the reaction, the p++ of the solution was maintained at a constant pH in the same manner as described above.After the dropwise addition was completed and foaming had stopped, the solution was rp
The filtrate was washed with pulp twice, and then dried in a vacuum dryer to obtain a fine powder of metallic nickel. The yield of the obtained fine powder of metallic nickel was 31.85 g, and the reaction yield was 98 g.
, 6%, and the average particle diameter measured by SEM photograph was 0.
The specific surface area of the particles was 1.00 m''/g by surface measurement using the BET method.

Comparative Example 1 In a LM three-day flat bottom flask, 10g of nickel chloride, 10g of quench! 8.8 g was added and dissolved with 800 mA' of pure water. Thereafter, the mixed solution in the Sanro flat-bottomed flask was sufficiently degassed by blowing nitrogen gas through a gas blowing tube provided at the mouth of the flask while stirring with a stirrer bead.

At this time, the exhaust port was sealed with water to prevent backflow of air.

Next, 3 g of sodium borohydride was dissolved in sufficiently degassed pure water (200+++j), this solution was placed in a bilette, and the mixture was stirred and nitrogen was blown into the mixed solution at a rate of 201 R/min. Dropped and subjected to reduction reaction 0
The above operations were performed at room temperature. The product was washed with methanol and then collected by filtration.

The yield of the obtained boron-nickel alloy powder was 0.21g.
The reaction yield was 8.5%, the average particle diameter measured by SEM photography was 0.02:l ps, and the specific surface area of the particles was 36 ff 17 g by surface measurement using the BET method.

Comparative Example 2 A reaction was carried out in exactly the same manner as in Comparative Example 1 using 4.5 mjl of hydrazine as a reducing agent, 8.8 g of citric acid as a complexing agent, and a reaction temperature of 90"C, and 0.17 g of metallic nickel powder.
The obtained zero reaction yield was 6.9%, the average particle diameter measured by SEM photography was 0.019 p■, and the specific surface area of the particles was 35 m''/g by surface measurement using the BET method.

Example 5 Copper sulfate 0.2 oi'/i', formalin 1 oj'/
j! , Take 200 mA' of an aqueous solution of pH 12.5 consisting of EDTAO, Imof/j' in a beaker,
After heating to 80°C on a hot water bath, palladium chloride 20
g/j! During the reaction, 5 liters of an aqueous solution of
12 drops of sodium hydroxide 100g/i) aqueous solution
,0 to 12,5.

After the foaming subsided, the amounts of 1 woR/R copper sulfate aqueous solution and 3 moR/R formalin aqueous solution shown in Table 5 were each added dropwise at a rate of 5 mR/min.The pH of the solution during the reaction was 12 as above. After the addition of 9 drops at a temperature of 0 to 12.5 was completed and no bubbling had stopped, the solution was filtered, and the filtrate was washed twice with a valve, and then dried in a vacuum dryer to obtain a fine powder of metallic copper. . Yield of fine powder of metallic copper obtained,
Reaction yield, average particle diameter measured by SEX photograph, B
Table 5 shows the specific surface area measured by the ET method.

Example 6 Copper sulfate 0.2mof'/i), hydrazine 0.8moj
200 mj) of an aqueous solution of p)l 13.0 having a composition of 0.05 mof+/i' of Rochelle salt was taken in a beaker and heated to 90°C on a water bath. Next, a small amount (approximately 0.1 g) of potassium boron hydride powder was added to the above aqueous solution under pressure of m to induce a self-decomposition reaction. During the zero reaction, the pH of the solution was adjusted using an automatic adjustment device. sodium oxide 100
g/i' aqueous solution was added dropwise to maintain the temperature at 12.5 to 13.5.

After the foaming subsided, 1 moR/ρ copper sulfate aqueous solution and 2 moR/R hydrazine aqueous solution were added dropwise in the amounts shown in Table 6 at a rate of 15 ml/min, respectively.
The pH of the solution was maintained at 12.5 to 13.5 as above. After the addition of 0 drops was completed and foaming had stopped, the solution was filtered, and the filtered material was washed twice with pulp and then dried in a vacuum dryer. A fine powder of metallic copper was obtained. Yield of fine powder of metallic copper obtained,
Reaction yield, average particle diameter measured by SEM photograph, BE
Table 6 shows the specific surface area measured by the T method.

Example 7 Silver cyanide 0.2 moi'/J? , sodium borohydride 0.24voi', EDTA-4NaO,
Aqueous solution 20 with a pH of 3.0 and a composition of 1 moR/i'
0■p was placed in a beaker and heated to 80°C on a hot water bath. Next, a 10 g/R aqueous solution of silver nitrate (10 tj) was added to the above aqueous solution under stirring to start the reaction.During the reaction, the pH of the solution was adjusted using an automatic adjustment device, with 2 tj of sodium hydroxide, It was kept at 12-13.

After the foaming subsides, 1 mol;! /R silver potassium cyanide aqueous solution and 1,2soR/j) sodium borohydride, 5uglyoR/R sodium hydroxide mixed aqueous solution 11) were each added dropwise at a rate of 15 ml/min. The pH was maintained at 12-13 as before.

After the dropping was completed and foaming had ceased, the solution was filtered, and the filtered portion was washed twice with pulp and dried in a vacuum dryer to obtain fine silver powder. The yield of the obtained fine silver powder was 111.8
5g, the reaction yield was 99.7%, the average particle diameter as measured by SEM photograph was 0.13 μm, and the specific surface area measured by BET method was 6.60 m”/g.

[Effects of the Invention] As explained above, according to the method for producing fine metal powder of the present invention, it is possible to produce fine metal powder with a desired particle size within two particle size ranges, extremely stable quality, and few impurities. It can be obtained in high yield. In particular, nickel, copper, and Nt-P, Ni-[1] alloys with average particle diameters of 0.01 to 1 can easily be 11
The industrial value of something that can be done is extremely high.

In addition, the equipment is inexpensive, has high productivity, and has a drug efficiency of 100%.
% effective, 100% of the metal salt used is reduced to fine metal powder, and the amount of reducing agent used can be smaller than conventional methods, so it is very economically advantageous. Furthermore, since one reaction is carried out slowly and always within a limited concentration, a stable and constant quality charge can be obtained.

The stable quality fine metal powder or fine alloy powder obtained by the production method according to the present invention can be used as a conductive filler as it is or by further coating with a blue metal Tg, and can be used as a conductive filler, as a PI material, resin, rubber, paste, etc. Used for kneading in adhesives, inks, etc. One more alloy.

It can also be used as a raw material for powder metallurgy.

Claims (4)

[Claims] (1) A reaction initiator is added to a mixed aqueous solution consisting of a metal ion, a reducing agent, and a complexing agent to cause a reduction reaction, and then a metal ion, a reducing agent, and a pH adjuster are added. A method for producing fine metal powder. (2) The method for producing fine metal powder according to claim 1, wherein the metal ions are nickel ions, copper ions, or silver ions. (3) The method for producing fine metal powder according to claim 1, wherein the reducing agent is selected from sodium hypophosphite, alkali borohydride, hydrazine, or formalin. (4) The metal fine powder is a fine powder of nickel, copper, or an alloy containing at least one of them, and has an average particle size of 0.05 to
A method for producing fine metal powder according to any one of claims 1 to 4, which has a particle size in the range of 1 μm.