JP2571222B2 - Method for producing conductive filler - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a conductive filler, and more particularly, to a composite conductive material such as a conductive polymer, a conductive rubber, a conductive plastic, a conductive paint, and a conductive adhesive. The present invention relates to a method for producing a conductive filler used for imparting conductivity to a material.

Technical background of the invention and its problems Conventionally, in composite conductive materials such as conductive polymers, conductive rubber, conductive plastics, conductive paints, and conductive adhesives, gold, silver, Precious metals such as platinum, metal powders such as copper, aluminum and nickel, carbon powders, carbon fibers, and the like have been added to base materials serving as bases. However, although carbons are inexpensive, they have low conductivity, and copper, aluminum and nickel are easily oxidized and have poor reliability with respect to conductivity. In addition, noble metals such as gold have a problem that the production cost is high because they are expensive.

In order to solve such problems, fillers in which the surfaces of particles such as copper powder, glass beads or synthetic resin are plated with metal have been developed. However, when these fillers are used in paints and adhesives, if the material to be plated is copper powder, the filler will separate and settle out of the paint in a short time due to the large specific gravity difference from the vehicle. Each time the filler is used, the filler must be redispersed immediately before use, resulting in poor workability. When the material to be plated is glass beads, the difference in specific gravity from the vehicle is slightly improved compared to copper powder, but the glass beads have a particle size of several tens of μm at present, so the performance is sufficient. Could not be satisfied. Further, when the object to be plated is a resin, the above-mentioned problem has been solved. However, the conductive coating or the conductive material obtained by using the composite conductive material in which the conductive filler is dispersed has an external pressure. However, there is a problem that the resin is deformed or the conductive layer is peeled off when the metal is added.

An object of the present invention is to solve the problems associated with the prior art as described above, and when added to a base material such as a paint or an adhesive, the specific gravity of the base material with the vehicle is reduced. An object of the present invention is to provide a conductive filler which has a small difference and good dispersibility and is economically excellent.

SUMMARY OF THE INVENTION The method for producing a conductive filler according to the present invention comprises dispersing metal oxide particles or metal hydroxide particles as seed particles in a water-alcohol-based dispersion, while keeping the dispersion alkaline, Adding an alkoxide and hydrolyzing, depositing a metal alkoxide decomposition product on the seed particles to grow the seed particles, and applying a metal plating to the surface of the obtained particles to form a metal plating layer. Features.

DETAILED DESCRIPTION OF THE INVENTION The method for producing a conductive filler according to the present invention is characterized in that a metal plating layer is formed on the surface of particles obtained by a specific method. The method for producing particles will be described.

The particles to be used in the present invention are spherical and have a sharp particle size distribution.However, the production method will be described. First, metal oxide particles or metal hydroxide particles are dispersed as seed particles. The prepared water-alcohol dispersion is prepared. The seed particles dispersed in the water-alcohol-based dispersion liquid are metal oxide particles or metal hydroxide particles, but in some cases, other particles having a uniform particle diameter can be used. The particles used as the seed particles as described above preferably have a particle diameter as uniform as possible of about 0.05 to 9.0 μm.

Such a water-alcohol-based dispersion in which the seed particles are dispersed may be obtained by adding the seed particles to a water-alcohol-based mixed solution or by generating the seed particles in the water-alcohol-based dispersion. Among them, a water-alcohol-based dispersion in which seed particles obtained by hydrolyzing a metal alkoxide in a water-alcohol-based dispersion are dispersed is preferably used. Seed powder and powder metallurgy 23 , (4), 19-24 (1976) or Jou
rnal colloid & Interface Sci, 26 , 62-69 (1968).

In this way, a water-alcohol-based dispersion in which metal oxide particles or metal hydroxide particles are dispersed as seed particles is obtained, but this dispersion is used so that the seed particles in the dispersion do not aggregate and coalesce. Into a dispersion (hereinafter sometimes referred to as a heel sol) stabilized by adding an alkali. If the dispersion is not stabilized by adding an alkali, the seed particles may aggregate and precipitate. When the seed particles aggregate, adhesion of the metal alkoxide hydrolysis product also occurs at the joint (neck portion) of the aggregated particles, so that particles having a uniform particle size cannot be obtained.

As the alkali added to stabilize the dispersion, ammonia gas, aqueous ammonia, alkali metal hydroxides such as sodium hydroxide, quaternary ammonium salts,
Amines and the like are used alone or in combination.

The alcohol concentration in the water-alcohol dispersion in which the seed particles are dispersed is preferably 35 to 97% by weight. As the alcohol used here, lower alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butyl alcohol and isobutyl alcohol are used. Also, a mixed solvent of these lower alcohols can be used.

Further, as the water-alcohol dispersion, other organic solvents can be used in addition to water and alcohol.
As such an organic solvent, one having good compatibility with water and alcohol and good compatibility with metal alkoxide is used.

The concentration of the seed particles in the water-alcohol dispersion is
The concentration is preferably 0.05 to 20.0% by weight in terms of oxide. If the concentration in terms of oxide of the seed particles is less than 0.05% by weight, new seed particles may be generated in the subsequent step of attaching the metal alkoxide hydrolysis product to the seed particles, and the particle size distribution of the obtained particles Is not preferred because it becomes broad. On the other hand, the oxide equivalent concentration of the seed particles is
If it exceeds 20.0% by weight, the particles are aggregated in the step of attaching the metal alkoxide hydrolysis product to the seed particles, which is not preferable.

Next, a metal alkoxide is added to the heel sol, which is a water-alcohol-based dispersion liquid in which the alkali-stabilized seed particles obtained as described above are dispersed, while maintaining the heel sol in an alkaline state, followed by hydrolysis. And depositing the metal alkoxide hydrolysis product on the seed particles to grow the seed particles.

As the metal alkoxide, any metal alkoxide can be used as long as it can form an alkoxide. The carbon number of the ester group forming the alkoxide is preferably about 1 to 7, and more preferably about 1 to 4. Such a metal alkoxide may be used after diluting it with an alcohol or the like, or may be used as a stock solution.

When adding a metal alkoxide to the dispersion,
It is preferable to add a water-alcohol mixed solution together with the metal alkoxide. It is preferable that these metal alkoxide and water-alcohol mixed solution are gradually added to the heel sol. When the metal alkoxide is added to the heel sol, the metal alkoxide starts to hydrolyze,
At this time, the pH of the heel sol changes rapidly. If the heel sol is not alkaline as described above, seed particles may aggregate or new seed particles may be generated, and the particle size distribution of the finally obtained particles is not preferred. Therefore, the addition of the metal alkoxide is performed while keeping the heel sol alkaline. The heel sol preferably has a pH of 10-13. In order to keep the heel sol alkaline, an alkali may be added to the heel sol. Specifically, as the added alkali, ammonia gas, aqueous ammonia, amines, alkali metal hydroxides, and quaternary ammonium salts are used. Used alone or in combination.

The temperature at which the metal alkoxide is hydrolyzed is not particularly limited, but when a temperature equal to or higher than the boiling point of water or alcohol is employed, it is preferable that the solution be pressurized so as to maintain a liquid phase. However, it is preferable to perform the decomposition reaction of the metal alkoxide at a temperature higher than the critical temperature of the alcohol or the like present in the reaction system, because the composition ratio in the liquid phase may change, so that the reaction is performed at a temperature lower than the critical temperature.

The metal alkoxide decomposition product is attached to the seed particles as described above to grow the seed particles, and the concentration of the grown particles in the reaction system is 0.05 to
It is preferably 20.0% by weight, more preferably 0.05 to 15.0% by weight. When the concentration of the particles is less than 0.05% by weight,
The productivity is low and a large amount of alcohol is required, and the economic efficiency is poor. On the other hand, if the concentration of the particles exceeds 20% by weight, agglomeration between the particles occurs during the growth of the seed particles, and the particle size distribution of the obtained particles is broad. Is not preferred.

When depositing the metal alkoxide hydrolysis product on the seed particles, the alcohol concentration in the reaction system is 35 to
Preferably it is 97% by weight. If the alcohol concentration is less than 35% by weight, it is not preferable because the compatibility with the metal alkoxide to be added is poor and the emulsion is formed, and the seed particles are agglomerated or an amorphous product that is not spherical is obtained. Exceeding the weight percent is not preferred because the rate of hydrolysis of the metal alkoxide becomes too slow. The alcohol concentration in the reaction system can be adjusted by adding water and an alcohol together with the metal alkoxide in the reaction system.The alcohol is in a ratio of 0.4 to 1.1 mol based on the alkoxide, and the water is based on the alkoxide. Preferably, it is added at a ratio of 2.0 to 24.0 mol.

The particles dispersed in the water-alcohol dispersion medium thus obtained are spherical, have a particle diameter of about 0.1 to 10 μm, have a sharp particle size distribution (σ ≦ 0.5), and are agglomerated in the dispersion medium. Monodispersed without. According to the method for producing particles as described above, the particle size of the obtained particles is 0.
It can be controlled to any value within the range of 1 to 10 μm. Further, the concentration of the particles on an oxide basis is 0.05 to 20.0% by weight, which can be significantly increased as compared with a conventional method for producing particles using a metal alkoxide. Therefore, the production efficiency of the particles can be increased and the production cost can be reduced.

In order to further enhance the stability of the particles monodispersed in the dispersion obtained according to the present invention, if a stabilizer such as an alkali is added to the obtained dispersion and the mixture is aged, the dispersion can be used for a long time. The particles inside do not agglomerate. Further, the alcohol in the dispersion can be replaced with another organic solvent. By drying such a dispersion, particles having good dispersibility can be obtained, and these are used as particles to be plated in the present invention.

In some cases, when the particles obtained as described above are heat-treated in an air atmosphere or an inert gas atmosphere at a temperature of 250 ° C. or higher, preferably 250 to 1000 ° C., the white particles become black. Although varying, the black particles having good dispersibility obtained in this way can be used as the particles to be plated.

The reason why the white particles are converted to black particles by heat treatment at a temperature of 250 ° C. or higher is considered to be as follows. That is, inside the particles before the heat treatment, there is an organic substance such as an unreacted metal alkoxide, and the organic substance such as the unreacted metal alkoxide is heated to a temperature of 250 ° C. or more and decomposed or carbonized. The particles will blacken.

The heat treatment temperature of the white particles is, as described above, 250 ° C. or higher, preferably 250 to 1000 ° C.
If the temperature is lower than ℃, the blackening of the white particles occurs, but it is not preferable because the blackening takes a long time.On the other hand, if the heat treatment temperature exceeds 1000 ° C, it is not preferable because sintering between particles may occur. .

In general, when the particle size of white particles is small,
Heat treatment in a relatively low temperature range in the temperature range of 250 to 1000 ° C. causes blackening, but as the particle size increases, heat treatment in a relatively high temperature range becomes necessary.

Further, in the present invention, water-
When the metal alkoxide is added to the alcohol-based dispersion, an organic substance to be dissolved or dispersed is added to the water-alcohol-based dispersion, and the organic substance is attached to the seed particles together with the metal alkoxide decomposition product, Next, when the obtained particles are heat-treated to a temperature of 250 ° C. or higher, the color tone of the obtained black particles can be further blackened. Alternatively, by subjecting the white particles obtained by drying the dispersion to heat treatment, the white particles are impregnated with a solution of an organic substance to adhere the organic substance to the pores of the particles, and then heat-treated. Also, the color tone of the black particles obtained can be further blackened.

The black particles obtained as described above are JIS Z 8
The Y value corresponding to the brightness of the color displayed based on the tristimulus values XYZ of the color measured in accordance with 701-82 usually has a value of 10% or less, and is extremely black. Are better.

The particles for plating obtained by the above-mentioned manufacturing method,
Since the particle size is 0.1 to 10 μm and the particle size distribution is sharp (σ ≦ 0.5), the conductive filler obtained by applying metal plating to the surface of the particles is a conductive polymer, a conductive rubber, a conductive plastic. It has good dispersibility when added to a base material such as a conductive paint or conductive adhesive, and also has excellent performance as a conductive filler.

In order to apply metal plating to the surface of the particles to be obtained as described above, a conventionally known method such as chemical plating can be adopted. The thickness of the metal plating layer is 100 mm
It is preferable that it is above. Metal plating layer thickness is 100
When the value is less than Å, the conductivity of the obtained conductive filler is undesirably low.

As the metal to be plated with metal, specifically, platinum,
Gold, silver, copper, nickel, palladium and the like are used. Alternatively, different types of metals can be sequentially plated to form a multilayer metal plating layer.

If an example of a specific method of performing metal plating on the surface of the particles to be plated by chemical plating is described, the particles are sufficiently dispersed in an aqueous ammoniacal metal nitrate aqueous solution, and a reducing organic compound such as formalin is used. By reducing and depositing the metal uniformly on the particle surface and attaching it,
Metal plating can be formed on the surface of the particles. At this time, by appropriately adjusting the ratio between the amount of the metal to be deposited and the amount of the particles to be metal-plated, various ones having various volume resistivity can be obtained.

When it is desired to improve the adhesion of metal plating, a small amount of an acidic metal salt of a plating metal that can be dispersed or dissolved in a water-alcohol mixture at the time of adding a metal alkoxide in the method for producing particles for plating is added at the same time. good.
Alternatively, the obtained particles for plating may be impregnated with an acidic metal salt.

Effect of the Invention The conductive filler obtained in the present invention is a conductive polymer,
It is added to composite conductive materials such as conductive rubber, conductive plastic, conductive paint, and conductive adhesive, but has a small difference in specific gravity from the vehicle and good dispersibility, and has excellent performance as a conductive filler. And is economically low cost.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 A mixture of 487 g of ethyl alcohol and 389 g of water was maintained at 35 ° C. while stirring, and 71.7 g of ammonia gas was dissolved in the mixture. 17.4 g of 28% ethyl silicate in this mixture
0.5 was added, the terms of SiO ₂ followed by subsequent 2 hours of stirring
A cloudy liquid in which seed particles corresponding to the weight% were dispersed was obtained.

An aqueous solution in which 0.03 g of NaOH was immediately dissolved in this cloudy liquid 3.3
g was added to obtain a heel sol (A) in which seed particles were dispersed in a water-alcohol dispersion.

97 g of the obtained heel sol (A) was maintained at 35 ° C. with stirring, and while controlling the pH at 11.5 with ammonia gas, a mixture of 455 g of ethyl alcohol and 886 g of water and 28 g
570 g of% ethyl silicate were gradually added simultaneously over 19 hours. After adding the whole amount, an aqueous solution in which 1 g of NaOH is dissolved
103 g was added, and this was heated to 70 ° C. and kept for 2 hours to obtain a dispersion liquid (I). The dispersion (I) was dried at 200 ° C. to obtain powder particles. The powder particles had a particle size of 2.0 μm and σ = 0.1 μm.

On the other hand, 29.2 g of silver nitrate was dissolved in a liquid obtained by diluting 28 ml of a 24% by weight aqueous ammonia solution with 800 g of water. Water 600 under stirring
To 20 g, 20 g of powder particles were added, and the aqueous ammoniacal silver nitrate solution was further added and sufficiently dispersed. While stirring this mixed solution, a solution prepared by diluting 32.8 ml of 30% formalin with 180 g of water was added dropwise, and the surface of the powder particles was plated with silver. Then
After overwashing, the resultant was dried at 90 ° C. to obtain a conductive filler. The obtained conductive filler had a specific gravity of 3.12, a thickness of the plating film of 400 °, and a specific resistance of 3 × 10 ⁻³ Ω · cm.

Example 2 114 g of the dispersion liquid (I) obtained in Example 1 was kept at 35 ° C. with stirring, 63 g of ethyl alcohol and 51 g of water were added, and the pH was adjusted to 11.5 with ammonia gas.
A mixture of 638 g and 814 g of water and 28% ethyl silicate 32
5 g were gradually added simultaneously over 19 hours. After adding the whole amount,
65 g of an aqueous solution in which 0.7 g of NaOH was dissolved was added, and this was added to 7
The mixture was heated to 0 ° C. and maintained for 2 hours to obtain a heel sol (B).
94.6 g of this heel sol (B) was maintained at 65 ° C. with stirring, 116 g of ethyl alcohol and 95 g of water were added, and the pH was adjusted to 1 with ammonia gas.
While controlling to 1.5, a mixed solution of 307 g of ethyl alcohol and 438 g of water and 207 g of 28% ethyl silicate were gradually added simultaneously over 19 hours. After adding the whole amount,
65 g of an aqueous solution in which 0.7 g of NaOH was dissolved was added, and this was heated to 70 ° C. and kept for 2 hours to obtain a dispersion (II).

1126 g of the obtained dispersion (II) was kept at 65 ° C. with stirring, 155 g of ethyl alcohol and 127 g of water were added to this dispersion (II), and while controlling the pH to 11.5 with ammonia gas, 164 g of ethyl alcohol and 275 g of water were added. And 156 g of 28% ethyl silicate were slowly added simultaneously over 19 hours. After adding the entire amount, an aqueous solution 65 in which 0.7 g of NaOH was dissolved
g was added and heated to 70 ° C. and kept for 2 hours to obtain a heel sol (C).

1324 g of this heel sol (C) was kept at 65 ° C. with stirring, 185 g of ethyl alcohol and 151 g of water were added, and the pH was adjusted with ammonia gas.
While controlling to 11.5, 93 g of ethyl alcohol
Of water and 150 g of water and 82 g of 28% ethyl silicate were gradually added simultaneously over 19 hours. After the entire amount was added, 58 g of an aqueous solution in which 0.6 g of NaOH was dissolved was added, and this was added at 70 ° C
And kept for 2 hours to obtain a dispersion liquid (III). The dispersion (III) was dried at 200 ° C. to obtain powder particles. The powder particles had a particle diameter of 7.9 μm and σ = 0.2 μm.

On the other hand, 38.0 g of copper nitrate was dissolved in a solution obtained by diluting 28 ml of a 24% by weight aqueous ammonia solution with 800 g of water. Water 600 under stirring
To 15 g, 15 g of powder particles were added, and the aqueous ammoniacal copper nitrate solution was further added and sufficiently dispersed. While stirring this mixed solution, a solution obtained by diluting 32.8 ml of 30% formalin with 180 g of water was added dropwise, and the surface of the powder particles was plated with copper. Then
After overwashing, the resultant was dried at 90 ° C. to obtain a conductive filler. The obtained conductive filler had a specific gravity of 2.40, a thickness of the plating film of 400 °, and a specific resistance of 5 × 10 ⁻³ Ω · cm.

Example 3 The powder particles obtained in Example 1 were treated under air atmosphere for 35 days.
Heat treatment was performed at 0 ° C. for 3 hours to obtain black particles. The obtained black particles have a Y value defined by JIS Z 8701 of 7.0.
%Met.

On the other hand, 19.4 g of copper nitrate was dissolved in a solution obtained by diluting 28 ml of a 24% by weight aqueous ammonia solution with 800 g of water. Water 600 under stirring
To 20 g, 20 g of black particles were added, and the aqueous ammoniacal copper nitrate solution was further added and sufficiently dispersed. While stirring this mixed solution, a solution obtained by diluting 32.8 ml of 30% formalin with 180 g of water was added dropwise, and the surface of the powder particles was plated with copper. Then
After overwashing, the resultant was dried at 90 ° C. to obtain copper plated particles. The thickness of the plating film of the copper plating particles was 200 mm.

Next, 18.0 g of silver nitrate was dissolved in a solution obtained by diluting 28 ml of a 24% aqueous ammonia solution with 800 g of water. The copper-plated particles were added to 600 g of water under stirring, and the aqueous ammoniacal silver nitrate solution was further added and sufficiently dispersed. While stirring this mixed solution, a solution prepared by diluting 32.8 ml of 30% formalin with 180 g of water was added dropwise, and silver plating was performed on the surface of the copper plating particles. Next, the resultant was dried at 90 ° C. after overwashing to obtain a conductive filler.
This conductive filler had a specific gravity of 3.03, a thickness of the silver plating film of 200 °, and a specific resistance of 1 × 10 ⁻³ Ω · cm.

Example 4 487 g of ethyl alcohol, 389 g of water and nickel nitrate hexahydrate
The mixture with 0.02 g was kept at 35 ° C. while stirring, and 71.7 g of ammonia gas was dissolved in this mixture. Add 2 to this mixture
After adding 17.4 g of 8% ethyl silicate, stirring was continued for 2 hours to obtain a cloudy liquid in which seed particles equivalent to 0.5% by weight as SiO ₂ were dispersed. Immediately add NaOH 0.
3.3 g of an aqueous solution in which 03 g was dissolved was added to obtain a heel sol (D) in which seed particles were dispersed in a water-alcohol dispersion.
97 g of the obtained heel sol (D) was maintained at 35 ° C. with stirring, and while controlling the pH at 11.5 with ammonia gas, 455 g of ethyl alcohol and 570 g of 28% ethyl silicate
And a mixed solution of 886 g of water and 0.63 g of nickel nitrate hexahydrate were gradually added simultaneously over 19 hours. After the total amount was added, 103 g of an aqueous solution in which 1 g of NaOH was dissolved was added, and the mixture was heated to 70 ° C. and kept for 2 hours to obtain a dispersion liquid (IV). 114 g of the obtained dispersion liquid (IV) was kept at 35 ° C. with stirring, 63 g of ethyl alcohol and 51 g of water were added, and the pH was adjusted with ammonia gas.
While controlling to 11.5, 638 g of ethyl alcohol
A mixed solution of 325 g of 28% ethyl silicate and a mixed solution of 814 g of water and 0.36 g of nickel nitrate hexahydrate were gradually added simultaneously over 19 hours. After the addition of the entire amount, 65 g of an aqueous solution in which 0.7 g of NaOH was dissolved was added, and this was heated to 70 ° C. and kept for 2 hours to obtain a heel sol (E). 94.6 g of the obtained heel sol (E) was mixed with 307 g of ethyl alcohol and 207 g of 28% ethyl silicate while maintaining a temperature of 65 ° C. with stirring, adding 116 g of ethyl alcohol and 95 g of water, and controlling the pH to 11.5 with ammonia gas. The solution and a mixed solution of 438 g of water and 0.23 g of nickel nitrate hexahydrate were gradually added simultaneously over 19 hours. After the entire amount was added, 65 g of an aqueous solution in which 0.7 g of NaOH was dissolved was added, and the mixture was heated to 70 ° C. and kept for 2 hours to obtain a dispersion (V).

1126 g of the obtained dispersion liquid (V) was kept at 65 ° C. with stirring, and while adding 155 g of ethyl alcohol and 127 g of water and controlling the pH to 11.5 with ammonia gas, mixing 164 g of ethyl alcohol with 156 g of 28% ethyl silicate. Liquid and water
A mixture of 275 g and nickel nitrate hexahydrate 0.17 g was simultaneously added to 19
Added slowly over time. After adding the whole amount, NaOH0.
65 g of an aqueous solution in which 7 g was dissolved was added, and this was heated to 70 ° C. and kept for 2 hours to obtain a heel sol (F). 1324 g of the obtained heel sol (F) was kept at 65 ° C. with stirring, 185 g of ethyl alcohol and 151 g of water were added, and the pH was adjusted to 11.5 with ammonia gas.
While controlling the amount of ethyl alcohol 93g and 28%
A mixed solution of 82 g of ethyl silicate and a mixed solution of 150 g of water and 0.09 g of nickel nitrate hexahydrate were gradually added simultaneously over 19 hours. After addition of the entire amount, 58 g of an aqueous solution in which 0.6 g of NaOH was dissolved was added, and the mixture was heated to 70 ° C. and kept for 2 hours to obtain a dispersion liquid (VI). The dispersion (VI) was dried at 200 ° C. to obtain powder particles. These powder particles have a particle size of 8.
At 0 μm, σ = 0.2 μm.

On the other hand, 41.7 g of nickel nitrate hexahydrate was dissolved in a solution obtained by diluting 28 ml of a 24% by weight aqueous ammonia solution with 800 g of water. 20 g of powder particles were added to 600 g of water under stirring, and the aqueous ammoniacal nickel nitrate solution was further added and sufficiently dispersed. While stirring this mixture, 32.8 ml of 30% formalin
Was diluted with 180 g of water, and the surface of the powder particles was plated with nickel. Next, the resultant was overwashed and dried at 90 ° C. to obtain nickel-plated particles. The thickness of the plating film of the nickel plating particles was 200 mm.

Next, potassium potassium cyanide (48.0 g) was dissolved in a liquid obtained by diluting 28 ml of a 24% by weight aqueous ammonia solution with 800 g of water. The nickel-plated particles were added to 600 g of water under stirring, and the aqueous ammoniacal potassium potassium cyanide solution was further added and sufficiently dispersed. While stirring this mixed solution, a solution prepared by diluting 32.8 ml of 30% formalin with 180 g of water was added dropwise, and the surface of the nickel-plated particles was plated with gold. Next, the resultant was dried at 90 ° C. after overwashing to obtain a conductive filler. This conductive filler has a specific gravity of 4.43 and a gold plating film thickness of 2000 mm.
And the specific resistance was 2 × 10 ⁻³ Ω · cm.

Example 5 118 g of nickel nitrate hexahydrate was dissolved in a solution obtained by diluting 280 ml of a 24% aqueous ammonia solution with 680 g of water. While stirring this liquid, 150 g of the powder particles obtained in Example 2 were gradually added, and the mixture was kept for 5 hours. This liquid was separated by a centrifuge, and the obtained precipitate was dried at 200 ° C. to obtain powder particles (particle diameter 8.0 μm, σ = 0.2 μm) under the same plating conditions as in Example 4. A conductive filler was produced. The obtained conductive filler has a specific gravity of 4.60 and a nickel plating film thickness of 20.
0Å, gold plating thickness 2000Å, specific resistance 1 × 1
It was 0 ^-3 Ω · cm.

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Claims (2)

(57) [Claims] 1. An aqueous-alcohol-based dispersion in which metal oxide particles or metal hydroxide particles are dispersed as seed particles, while keeping the dispersion alkaline, adding a metal alkoxide and hydrolyzing the dispersion. A method for producing a conductive filler, comprising: attaching a hydrolysis product of a metal alkoxide to particles to grow the seed particles; and forming a metal plating layer on the surface of the obtained particles. 2. The method according to claim 1, wherein the particles obtained by growing the seed particles are heat-treated at a temperature of 250 ° C. or higher to blacken, and a metal plating layer is formed on the surface of the obtained black particles. 2. The method for producing a conductive filler according to claim 1.