JPH03200877A - Composite conductive powder and its manufacturing method - Google Patents

Abstract

PURPOSE:To prepare the title powder with an excellent conductivity by depositing a water-insol. compd. on the surface of a carrier from an aq. soln. contg. a water-sol. zinc salt of an org. acid, a water-sol. tri- or tetravalent metal salt, and the carrier, and then baking the deposit. CONSTITUTION:While an aq. soln. (A) contg. a water-sol. zinc salt of an org. acid and a water-sol. tri- and/or tetravalent metal salt is being added to an aq. soln. (B) contg. a particulate carrier dispersed therein, an alkali agent is also added to the soln. B to adjust the pH of the soln. B to 5-9, thereby depositing a water-insol. compd. on the surface of the carrier. The carrier thus treated is separated by filtration, washed, dried, and baked to give the title powder. A pref. water-sol. zinc salt is a zinc salt of a carboxylic acid. Pref. water-sol. metal salts are chlorides, nitrates, sulfates, etc., of Al, Ge, Ga, Sn, In, etc. Examples of the carrier are mica, kaolin, talc, zinc oxide, and a glass flake.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a conductive powder useful as a conductive filler capable of imparting excellent conductivity and antistatic properties to various resins and paints, particularly conductive powder. The present invention relates to a composite conductive powder in which zinc oxide is supported on a carrier and a method for manufacturing the same.

[Conventional technology]

Until now, as an example of manufacturing zinc oxide-coated particles, mica flakes coated with titanium oxide in advance were added to an aqueous zinc chloride solution, ammonium hydroxide was added until the initially formed precipitate was dissolved, and then heated to about 80°C. Japanese Patent Publication No. 43-2564 describes a method in which the ammonia is expelled from the solution by holding it at that temperature for about 2 hours, followed by filtration and drying.
It is described in Publication No. 4. The zinc oxide coated particles produced by this method are used as pigment compositions. Further, US Pat. No. 3,941,578 discloses coating the surface of urea with zinc oxide powder, which is used as a fertilizer.

On the other hand, examples of composite conductive powder include titanium oxide powder supported with tin oxide (Japanese Patent Laid-open Nos. 56-41603, 61-141616 and 63-233016);
Mica supported with tin oxide (Japanese Unexamined Patent Application Publication No. 60-25
No. 3112 and No. 63-28518> and potassium titanate supported with tin, indium, etc.
No. 2-59528) and the like are known. However, products using tin oxide tend to have a dark color, and a light color is desired.

On the other hand, zinc oxide is white and does not cause problems when used with tin oxide, but zinc oxide alone has a high specific gravity of 5.8, so lowering the specific gravity is desired in order to be effective with a smaller amount. . However, a composite conductive powder in which zinc oxide is supported on carrier particles is not yet known.

[Problem to be solved by the invention]

Therefore, the present invention provides zinc oxide supported on carrier particles.
The purpose of the present invention is to provide a composite conductive powder having excellent conductivity. Another object of the present invention is to provide an efficient method for producing the composite conductive powder.

[Means to solve the problem]

The present invention provides that when a coating layer made of zinc oxide in which some of the zinc atoms constituting zinc oxide are replaced with specific metal atoms is formed on the surface of a carrier, a composite conductive powder having excellent conductivity can be obtained; According to the method of precipitating these water-insoluble compounds on the surface of a carrier using a water-soluble organic acid salt of zinc and a salt of a specific metal, a composite conductive powder can be efficiently produced and the above problems can be solved. This was done based on the knowledge of

That is, the present invention provides a composite conductive powder characterized in that a coating layer made of zinc oxide containing trivalent and/or tetravalent metal atoms is formed on the surface of a carrier.

Further, the present invention provides a method for controlling the pH of an aqueous solution containing a water-soluble organic acid zinc, a trivalent and/or tetravalent water-soluble metal salt, and a carrier to a pH of 5 to 5.
9 and precipitate a water-insoluble compound on the surface of a carrier, followed by firing.

The water-soluble organic zinc acids used in the present invention include zinc acetate,
Examples include zinc salts of organic acids, preferably carboxylic acids, such as zinc oxalate, zinc formate, zinc citrate, zinc lactate, and zinc glycolate. When such an organic acid zinc is used, the precipitated water-insoluble compound becomes fine, and the constituent components of the organic acid are volatilized or burned during firing and do not remain in the fired product, which is preferable.

Further, trivalent and/or tetravalent water-soluble metal salts used in the present invention include hydrochlorides, nitrates, sulfates, acetates, cissulates, formates, etc. of aluminum, germanium, gallium, tin, indium, etc. and metals themselves and their oxides. Among these, water-soluble salts such as hydrochloride, nitrate, and sulfate are preferred, and these can be used alone or as a mixture of two or more. In the present invention, the trivalent and/or tetravalent metal atom is 0.0001 to 0.1 mol, preferably 0.0 mol per mol of zinc atom.
It is preferable to contain 0.01 to 0.05 mole. That is, by substituting (doping) some of the zinc atoms constituting zinc oxide with trivalent and/or tetravalent metal atoms in this way, zinc oxide can be rendered conductive.

As the carrier of the composite conductive powder used in the present invention, mica,
Kaolin, talc, illite, plapeisite, diatomaceous earth, xonotlite, zinc oxide, titanium oxide, β-wollastonite, potassium titanate, glass fiber,
Examples include carriers such as glass flakes. Such a carrier preferably has an average particle size of about 0.1 to 100 μm, and particularly preferably bulky particles with low specific gravity. Furthermore, anisotropic shapes such as needle-like and plate-like shapes are preferable.

To produce the composite conductive powder of the present invention, an aqueous solution in which carrier particles are dispersed is prepared, and then a water-soluble organic acid zinc and a trivalent and/or tetravalent water-soluble metal salt are dissolved in the aqueous solution. While adding , an alkaline agent is added to adjust the pH of the liquid to 5 to 9, preferably 6 to 8, and the water-insoluble compound is precipitated on the surface of the carrier. Here, any alkali agent can be used, but for example, alkaline ammonium containing aluminum ions, ammonium carbonate, ammonium bicarbonate, etc. are volatilized or burned during baking, and alkali ions are released into the baked product. Preferably, it does not remain. Incidentally, the alkaline agent can also be used in the form of an aqueous solution.

The concentration of the carrier particles in the aqueous solution is preferably 10 to 300 g/L, preferably 20 to 200 g/f, and the zinc oxide/carrier ratio (weight ratio) is 5/100.
~200/100, preferably 10/100~100/
It is better to set it to 100.

In the present invention, a water-insoluble compound (estimated to be a hydrate of a mixture of zinc oxide and trivalent and/or tetravalent metal oxide) is formed on the surface of the carrier by the above method. A composite conductive powder is produced by filtering the powder using a conventional method, washing with water, drying, and firing.

Here, the firing conditions are non-oxidizing gas (nitrogen, argon,
- 500 to 1300°C, preferably 500 to 900°C in nitrogen or argon containing carbon oxide or hydrogen
Alternatively, it is preferable to carry out the reaction in the presence of solid carbon as described in JP-A-54-161598.

By the above method, the average particle size is 0.1 to 100 μm and the volume resistivity is 106 Ωcm or less, preferably 1040 cm.
The following composite conductive powder is obtained. Such a volume resistivity value can be calculated by, for example, placing 0.5 g of a sample in a resin cylinder with an inner diameter of 10 mm, applying a pressure of 100 kg/c++f, measuring the resistance with a tester, and using the following formula.
I can do that.

Volume resistivity value (Ωcm) = Thickness of sample (cm) In addition to the composite conductive powder of the present invention, alcohol amine,
The dispersibility in resins and paints can be improved by treating with organic substances such as polysiloxane, titanate coupling agents, and silane coupling agents.

〔Effect of the invention〕

According to the present invention, the shape and color can be controlled by selecting the coating amount and carrier, and the composite conductive powder can be colored, and can effectively impart conductivity and antistatic properties to resins or paints with a small amount. can be provided. In other words, since the zinc oxide coating is white, if a substance with high whiteness is used as a carrier, it is possible to support particularly white conductive powder. Further, by selecting the shape and specific gravity of the carrier, it is possible to provide an effective conductive powder in a small amount.

Furthermore, according to the method of the present invention, composite conductive powder can be produced extremely efficiently.

Next, the present invention will be explained with reference to Examples.

〔Example〕

Example 1 30 g of muscovite having an average particle size of 27 μm was stirred and dispersed in 400 g of ice. Separately prepared zinc acetate dihydrate 2
7. Og and aluminum nitrate nonahydrate 0.0, containing 92 g. I N FII4 acid solution 100mL! :109
An aqueous ammonium 6 carbonate solution was stirred and added to the above muscovite dispersion solution over a period of 60 minutes while maintaining the pH of the reaction solution at 7.

Next, the muscovite with a water-insoluble compound formed on its surface is filtered, washed, dried at 105°C for 15 hours, and then fired at 800°C for 1 hour in the presence of solid carbon to obtain a composite conductive powder. Obtained. The volume resistivity value of this powder is 1.0X102Ω
It was cm.

Example 2 10 g of muscovite having an average particle size of 4 μm was stirred and dispersed in 300 g of water. Separately prepared zinc acetate 2 water kn
27. 100 rnI of an aqueous solution containing 0.92 g of Og and aluminum nitrate nonahydrate! and 10% ammonium water were added to the above muscovite dispersion solution over 60 minutes with stirring while maintaining the pH of the reaction solution at 8.

Next, the muscovite with a water-insoluble compound formed on its surface is filtered, washed, dried at 105°C for 15 hours, and then baked at 800°C for 1 hour in a nitrogen atmosphere containing hydrogen to form a composite conductive powder. I got it. The volume resistivity value of this powder is 2.6X1
It was 0' Ωcm.

Example 3 Glass fiber pulverized product with a fiber diameter of 13 μm (average fiber length of 35 μm)
m) 10 g was stirred into 400 g of water for several minutes. Separately prepared, 0.00 g containing zinc acetate dihydrate 27.0g and aluminum nitrate nonahydrate 0.92 g. IN nitric acid solution 10
0m1! and 10% ammonium water were added to the above-mentioned glass fiber pulverized product dispersion solution over a period of 45 minutes with stirring while maintaining the pH of the reaction solution at 7.

Next, the glass fiber pulverized product with a water-insoluble compound formed on its surface was filtered, washed, dried at 105°C for 15 hours, and then fired at 700°C for 3 hours in a nitrogen atmosphere containing carbon oxide. A composite conductive powder was obtained. The volume resistivity value of this powder was 2.7×10′Ωcm.

Claims (2)

[Claims] (1) A composite conductive powder characterized in that a coating layer made of zinc oxide containing trivalent and/or tetravalent metal atoms is formed on the surface of a carrier. (2) After adjusting the pH of the aqueous solution containing a water-soluble organic acid zinc, a trivalent and/or tetravalent water-soluble metal salt, and a carrier to 5 to 9 to precipitate a water-insoluble compound on the surface of the carrier, A method for producing a composite conductive powder, the method comprising firing the composite conductive powder.