JPS60133066A - Manufacturing method of nickel-coated mica powder - Google Patents

Abstract

PURPOSE:To obtain titled powder suitable for conductive pigment etc. by suspending mica powder in an aqueous solution of palladium chloride of specific pH value to perform activation treatment through manipulation of the pH value of the system so that the surface of said powder is coated with palladium followed by carrying out a electroless plating. CONSTITUTION:Mica powder is suspended in an aqueous solution of palladium chloride with a pH <=2; alternatively, mica powder is suspended in an aqueous solution of palladium chloride followed by adjusting the pH value of the system to <=2. After that, an activation treatment is carried out spending enough time, while raising the pH of the medium to 4-7, to form uniform coating film of palladium on the surface of said powder. The resulting activated mica powder is subjected to electroless plating using a nickel compound, thus obtaining the objective powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing Ni-coated mica powder suitable for conductive pigments and conductive fillers used in the production of conductive paints, conductive plastics, and the like. In this specification, both the conductive pigment and the conductive filler are collectively referred to as conductivity-imparting powder.

As the conductive powder used as conductive pigment, Ag
Metal powders such as , Cu, AI, and Ni have been known for a long time, but since Ag is expensive and Al and Cu are easily oxidized, Ni is used as the most practical conductive pigment.

As the Ni powder as the conductive pigment, Ni powder made from nickel carbonyl (referred to as carbonyl nickel) is generally used. This is a fine particle with a particle size of a few or less, and moreover, it is spherical. The conductivity of a paint film is caused by the contact between pigment powders, but in this sense spherical particles are not advantageous. The proportion of conductive powder is 60% or more.

Usually, it is necessary to keep the content between 70 and 80%. As a result, the proportion of the resin binder decreases, resulting in poor strength of the coating film and the disadvantage that it is easily peeled off. Furthermore, the fine 11T carbonyl nickel powder has poor dispersibility and requires strong dispersion treatment in the production of coating materials, and the surface smoothness of the coating film is also poor.

Furthermore, Ni powder is black and has little aesthetic effect. Furthermore, since the Ni powder settles during storage of the paint, it is necessary to redisperse it before use; however, the sediments are highly agglomerated and redispersion is not easy.

The reason mentioned below-1- is that the specific gravity of Ni powder is large (8,
9), because it is m-thin and spherical. The conductive pigment is preferably a powder with a small specific gravity and a particle size of 5 to 60#L, and is preferably flake-like or fibrous rather than spherical. As a conductive filler,
Carbon powder and fiber, AI flakes, Ni powder, N
There are i-coated carbon powders, Cu or patterned fibers, etc., but carbon materials lack conductivity, AI lacks oxidation resistance, and Ni-coated carbon fibers are expensive, so they are not used practically. The material used was Ni powder or copper fibers.

However, these fillers have a specific gravity of 8 or more l-, and when mixed with a resin, for example, in order to achieve conductivity with an electromagnetic shielding effect, the filler should be 60% of the total resin composition, preferably 60% of the total resin composition. It must contain at least 70%. For this reason, the specific gravity of the resin containing the conductive filler becomes 2 or more -L, which impairs the light floating properties of the resin.

That is, it is desirable that the conductive filler mixed into the resin has a specific gravity as low as possible. Since conductivity depends on the volume% of the conductive filler (usually around 20% by volume is optimal),
The low specific gravity of the conductive filler has the advantage that the required amount (weight) of the conductive filler to be included is small.

In this sense, it has been known that nickel-coated mica powder is advantageous as the conductive H4 powder.

1. The specific gravity of Kumoha J is about 2.8, and the powder was mixed with Ni.
Even if it is coated with Ni, its specific gravity is smaller than that of Ni. For example, N
Even a material coated with 40% i has a specific gravity of about 3.9, and can exhibit conductivity with a small weight.

2. Mica particles are flaky, and they maintain this shape even when coated with Ni, making it easy for the particles to come into contact with each other in a paint film or plastic, and it is possible to exhibit conductivity with a small amount of overlapping. . In addition, the cloud flj powder has essentially good dispersibility, and the Ni-coated powder also has good dispersibility.
It is easy to make into paint.

3. The price of mica is cheaper than Ni, and the Ni coating Vffi
Even m powder is cheaper than Ni.

Generally, Ni is coated on the powder surface by electroless plating, which usually requires the following steps.

(j) If oil or fat is attached to the powder surface, degrease it.

(2) Pre-treat with stannous chloride solution, etc.

(3) A treatment is performed to deposit 4=J palladium chloride on one surface of the powder (activation).

(4) Apply Ni plating.

In electroless plating of mica powder, the present inventors have discovered that (3
) by strictly selecting the activation conditions for (2
It has been found that the step ) can be omitted, a uniform Ni coating can be applied, and a Ni-coated cloud paste powder with excellent gloss can be obtained.

That is, according to the present invention, when coating mica powder with nickel by electroless plating, the mica powder is suspended in an aqueous palladium chloride solution having a pH of 2 or higher, or the mica powder is suspended in an aqueous palladium chloride solution and then the mica powder is suspended in an aqueous palladium chloride solution. The activation treatment thus obtained is carried out by adjusting the pH to below 2 and then increasing the pH of the treatment medium to 4-7 over time so that a uniform coating of palladium occurs. A method of manufacturing a nickel-coated mica powder is provided that comprises electroless plating a mica powder.

The mica powder used in the method of the present invention has a major axis of 5 to 5 OOJ.
I like L's.

Cloud powder usually has less dirt on its surface and can be used as is without degreasing. This was suspended in a predetermined amount of water, and palladium chloride was set as Pd to 0.05 to 0.2
Concentration of 0g/liter, preferably 0.06-0.10g/i
Activation is achieved by slowly adding water to bring the pH to between 4 and 7 after p)( is below 2).
The plating becomes uniform.

Palladium +4 oxide is usually dissolved in water or an aqueous hydrochloric acid solution, and when an aqueous hydrochloric acid solution is used, the pH can be adjusted to 2 or less by adding it to the mica suspension. If the pH is 2 or more, add salt tolerance to make it 2 or less. In this state, palladium chloride is considered to exist as a solution. Next, water is added to this solution to bring the pH to 4 or higher. As water is added, the volume of the solution increases and the pH increases.
When H becomes 4 or more, palladium chloride begins to hydrolyze,
Palladium begins to precipitate on the mica surface.

In this case, if the time required to raise the pH from more than 2 to more than 4 is too short, uneven precipitation will occur, so it is usually necessary to raise the pH to 4 or more for 20 minutes or more.
It is important to do this for up to one hour. Other Methods for Raising the pH 1 For example, when adding an alkali, the precipitation of palladium is uneven, and the subsequent Ni plating does not occur uniformly, resulting in a coated powder with poor gloss.

If the Ni-coated needle is 10% of the weight of the coated powder, it can cover the entire surface of the powder and achieve conductivity close to that of a Ni-width body. On the other hand, even if it exceeds 50%, there is no profit commensurate with it.

The present invention will be specifically explained below using Examples.

Example 270 g of mica powder with a specific surface area of about 3 m2/g was dispersed in 3 m2 of water, and 90 OCC of palladium chloride aqueous solution (P
(containing 0.3 g/liter) was added as d. Add water over 10 minutes to 1 hour while stirring well until the final pH is 3.
The total length of the entire capital was approximately 30 to 60 sentences, so that it would be 8. The dispersed mica powder was filtered and dried.

Cloud 9j powder 24 subjected to palladium activation treatment as described below.
Suspend 0 g in 1 liter of water and add nickel sulfate (N, i S
One portion of an aqueous solution in which 590 g of 04 ・6H,,O) was dissolved was added, heated, and kept at 70°C. Here, a solution of 390 g of hydrazine sulfate ((NH2) 2 H2, S 04 ) dissolved in 620 cc4 of a 29% NH0OH aqueous solution was added, stirred for 30 minutes to precipitate 3f9 Ni, and then left, washed, and dried. Ni-coated mica powder was obtained. Approximately 35% of the affected companies were.

This powder was made into a paint using an acrylic paint base (No. 2026, manufactured by Kansai Paint Co., Ltd.) and applied to a thickness of 50 l, and the surface gloss and surface resistance of the paint film were examined.

The conditions and results of treatment with palladium chloride aqueous solution are summarized in the following table.

Implementation No., crossroad pH water addition time coating 119 state l 3
30 White ■ 2 4 3O Glossy 10 3 4 10 Black 70 4 5 10 Black, non-glossy 5O 5520 Glossy 10 6 5 60 Glossy lO 75120 Glossy 10 8 7 30 Glossy 10 9 8 30 Black, Non-glossy 100

Claims (1)

[Claims] ! , When coating mica powder with Nilakel by electrolytic plating, the mica powder is suspended in a palladium chloride aqueous solution with a pH of 2 or less, or the mica powder is suspended in a palladium chloride aqueous solution and then the pH is adjusted to 2 or less, After that, activation treatment is carried out by raising the pH of the treatment medium to 4 to 7 over time so that a uniform coating of palladium occurs,
A method for producing nickel-coated mica powder, which comprises electroless plating the activated 'It iU powder thus obtained.