JPH0832560B2 - Composite conductive powder and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a powder of titanium dioxide and an inorganic tabular substance,
The present invention relates to a novel composite conductive powder which has a coating layer of antimony solid solution tin oxide and is excellent in conductivity and hiding property, and a method for producing the same. In particular, the present invention relates to a conductive powder and a manufacturing method useful in the field for imparting conductivity and hiding property by coating or impregnating paper, rubber, plastic or the like with a conductive paint containing mixed or conductive powder. Is.

2. Description of the Related Art As a conductive powder having a concealing property, a titanium dioxide pigment whose surface is coated with a conductive substance (Japanese Patent Publication No.
60-21553, JP-A-56-114215, JP-A-56-114218)
Is proposed. Also inorganic tabular materials, such as mica,
JP-A-60-50813 and JP-A-60-253112 have been proposed as transparent conductive powders whose surface is coated with a conductive material such as kaolinite.

Problems to be Solved by the Invention In order to impart conductivity to paper or plastic, a conductive material is mixed in the inside of these insulators, or a conductive paint containing these conductive materials is applied to the surface of the insulating support. It is achieved by coating or impregnating the.

Conventionally, conductive materials used for such purposes include carbon-based conductive materials, metal-based conductive materials, metal oxide-based conductive materials, and ion conductive-based conductive materials such as polymer electrolytes and inorganic salts. Among these, carbon-based conductive materials, metal-based conductive materials and metal oxide-based conductive materials have various shapes such as fine powder, granules and long fibers,
Although it has already been put to practical use as a composite material, it is lacking in reinforcing properties for polymers, and even if it has reinforcing properties, it is a coarse fiber and has poor processability, so it can be used as a composite material with polymeric materials. Has a limit.

Further, the one treated with the ion conductive type conductive material has a drawback that it absorbs moisture in the atmosphere and its conductivity is largely influenced by a change in humidity, and its conductivity is small.

A method for producing a conductive powder material by subjecting the surface of an inorganic powder to a conductive treatment is known, and, for example, JP-A-56-11421.
No. 5 to No. 114218, in order to obtain a material used for a conductive layer such as an electrically conductive thermal paper or an electrostatic recording paper, a metal oxide powder such as titanium oxide is dispersed in heated water, and tin chloride is added thereto. By adding an alcohol solution or an alcohol solution of tin chloride and antimony chloride, a coating layer made of tin oxide or tin oxide containing a small amount of antimony is formed on the surface of the metal oxide powder to produce a conductive powder material. The method is described.

However, the conductive powder material obtained by the above method exhibits excellent hiding property when mixed with a conductive paint or the like because of the high hiding property inherent to the titanium dioxide pigment,
Since fine spherical titanium dioxide is used as the core, the dispersibility in the paint is poor, a strong dispersion treatment is required in the paint production, and the contact point of particles in the paint is limited. Because of its poor conductivity, it is necessary to add a relatively high concentration to obtain the desired conductivity.
Problems of cost and binder strength have been pointed out.

On the other hand, as the transparent and electrically conductive powder, there is an electrically conductive powder obtained by coating the surface of an inorganic plate-like substance with an electrically conductive substance. The electrically conductive powder has no hiding property, but it is mixed in a coating film or the like. In this case, the contact between the tabular grains is changed from point contact in the case of spherical grains to surface contact, so that high conductivity is exhibited. From the above points, there is still no satisfactory electroconductive powder having both concealing property and electroconductivity, and therefore improvement thereof is desired.

Solution In order to solve the above problems, the present inventors have prepared a conductive powder that is a composite of a titanium dioxide pigment, which is a base material with excellent hiding property, and an inorganic tabular substance, which is a base material with excellent conductivity. I studied about. As a result, it was found that the titanium dioxide powder and the inorganic flat material were mixed in advance, pulverized and integrated, and then coated with a conductive material to obtain a conductive powder having excellent hiding property and conductivity. It is a thing.

Metallic oxide powder such as titanium dioxide, which has excellent hiding power, is coated with a conductive material, and conductive material is used for non-hiding but highly conductive inorganic plate-like materials. By mixing and using the coated conductive powder, it is possible to use the characteristics of both of them, but as shown in the present invention, the titanium dioxide powder and the inorganic tabular substance are mixed and crushed in advance to form a composite integrated body. After that, by coating and complexing the conductive material, the dispersibility in the paint was remarkably improved, and both the hiding property and the conductivity were superior to the case where the conductive powders prepared separately were mixed and used. It was found that a composite conductive powder can be obtained.

Such a combined effect is that substances having different particle diameters and particle morphologies are more uniformly mixed by previously mixing and pulverizing, and the inorganic tabular powder and the titanium dioxide powder are uniformly mixed with each other. The coating is applied to form an integrated composite conductive material. This is presumed to be the reason why more excellent concealing property, conductivity and dispersibility are obtained as compared with the case where the conductive powders having different particle diameters and particle forms are mixed and used. As the conductive powder material, it is preferable that the material has good dispersibility and the shape is flake rather than spherical. The reason for this is clear that the conductivity is caused by the contact between the conductive pigment powders, and the spherical particles are the point contact, while the flakes are the surface contact, which is very preferable for the conductivity. Will be things.

The present invention utilizes the excellent concealing property of titanium dioxide and the surface contact property of an inorganic tabular substance such as scaly mica, and this idea is novel until now. The titanium dioxide used in the present invention is preferably in the pigment class from the viewpoint of hiding property. Titanium dioxide may be either anatase type or rutile type. In addition to mica, illite, brabaysite,
Examples include kaolinite and glass flakes.

In the method for producing a conductive powder of the present invention, first, titanium dioxide and scaly mica are mixed at a titanium dioxide content of 10 to 90% by weight, preferably 20 to 80% by weight, and a solid content concentration of 200
Make an aqueous suspension of ~ 1000 g / l, preferably 300-600 g / l.
Next, this water suspension is wet-milled to a concentration of 10 to 500 g / l, preferably 50 to 200 g / l. In the case of dry pulverization, make an aqueous suspension after pulverization.

For the conductive coating, the aqueous suspension is heated to 50 to 100 ° C., preferably 70 to 90 ° C., and an aqueous hydrochloric acid solution containing tin chloride and antimony chloride is added dropwise to form the conductive coating. The amounts of tin chloride and antimony chloride to be dropped vary depending on the desired conductivity, but usually 0.1 to 25% by weight of antimony and the balance is 5 to 60% by weight in total of the coating layer which is substantially tin oxide. Is a range containing. If the amount is too small, the desired conductivity cannot be obtained, and if it is too large, the effect of improving the conductivity is small and it is not economical. The dropping rate varies depending on the treatment amounts of tin chloride and antimony chloride, but is usually 30 minutes to 4 hours, preferably 1 to 2 hours, and the dropping is slow. If it is too short, the coating becomes non-uniform and desired conductivity cannot be obtained, and if it is too long, productivity is lowered, which is not preferable.

The product coated with the hydrate of tin oxide and antimony oxide is then filtered, washed and recovered from the suspension after completion of the reaction, dried and dried. Then 300-800 ℃, preferably 500-6
After firing at a temperature of 00 ° C. to convert the hydrate of the coating layer into an oxide, the powder is pulverized to give a conductive powder. The firing time is 30 minutes to 4 hours, preferably 1 to 2 hours. If the firing conditions deviate too much from the above range, the desired conductivity cannot be obtained.

As described above, according to the present invention, the conductive powders produced separately from the concealing substrate and the substrate having excellent conductivity are not mixed, but sufficiently mixed and pulverized before the conductive coating treatment. By performing the treatment, a composite conductive powder having excellent hiding property and conductivity as compared with simple mixing can be obtained.

As an example, the electroconductive powder material of the present invention has a specific resistance of 10 ohm · cm / 1K ohm · cm, and a coating film obtained by applying a coating composition in which this is dispersed in a binder to an insulating transparent film, It has a surface resistance of 10 ⁵ to 10 ⁹ ohms and a concealing property with a light transmittance of 33% or less (the transmittance of transparent conductive powder is 90% or more) and it is extremely resistant to changes in humidity. It was stable. In addition, since the conductive layer is formed by laminating in the coating film due to the high aspect ratio of scaly mica, it is sufficient to form the conductive layer to a thickness sufficient to obtain the desired conductivity, and the coating layer can be arbitrarily selected. It is economical because you can.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 3750 g of rutile titanium dioxide and 1250 g of scaly mica powder having an average diameter of 14 μm and an aspect ratio of 58 were purified water of 1700 m.
It was dispersed in 1 by stirring. After wet pulverizing this water suspension, 100
Dilute to a concentration of g / l and heat to 80 ° C. Next, in a separately prepared 2000 ml of 4N HCl aqueous solution, 1729.8 g as SnCl ₄
234.3 g of SnCl ₄ .xH ₂ O and SbCl ₃ were added dropwise over 1 hour. The product is filtered, washed and dried to 500
The composite conductive powder was obtained by baking at 2 ° C. for 2 hours.

Example 2 Concentration of 2500 g of rutile titanium dioxide and 2500 g of scaly mica
The same treatment as in Example 1 was carried out except that it was used as a 300 g / l water suspension.

Example 3 Concentration of 1250 g of rutile titanium dioxide and 3750 g of scaly mica
The same treatment as in Example 1 was carried out except that it was used as a 300 g / l water suspension.

Comparative Example 1 The same treatment as in Example 1 was carried out except that 5000 g of rutile titanium dioxide was used as an aqueous suspension having a concentration of 300 g / l.

Comparative Example 2 The same treatment as in Example 1 was carried out except that 5000 g of scaly mica was used as an aqueous suspension having a concentration of 300 g / l.

Comparative Example 3 The conductive powders of Comparative Example 1 and Comparative Example 2 were mixed at a weight ratio of 75:25 to obtain a conductive powder.

Comparative Example 4 The conductive powders of Comparative Example 1 and Comparative Example 2 were mixed at a weight ratio of 50:50 to obtain a conductive powder.

Comparative Example 5 The conductive powders of Comparative Example 1 and Comparative Example 2 were mixed at a weight ratio of 25:75 to obtain a conductive powder.

The performances of the conductive powder materials of the above Examples and Comparative Examples were tested, and the results shown in Table 1 were obtained.

1 and 2 are graphs of the results of Table 1.

 The evaluation in Table 1 was performed as follows.

1.Powder resistance (Ω · cm): 1g of sample powder is sampled and 300kg / cm
^A columnar green compact (23 mm in diameter) was formed by applying a pressure of ² , and its resistance was measured with an electrometer (manufactured by Takeda Riken).

2. Surface resistance (Ω / □): After mixing sample powder with vinyl acetate-vinyl chloride copolymer (trade name: VAGH, UCC) to make a coating (P / B = 1.5), use a 1.5 mm applicator , PET film was uniformly applied, and the surface resistance of the coating film was measured with an electrometer (manufactured by Takeda Riken).

3. Light transmittance (%): The same coated film as in 2. was measured with a direct-reading Hayes computer (manufactured by Suga Test Instruments).

4. Hiding power (%): The paint prepared in the same way as in 2. was applied uniformly on a hiding power measurement paper having white and black with a 1.5 mil film applicator, and displayed in the ratio of brightness of white and black. .

[Brief description of drawings]

FIG. 1 is a graph of surface resistance of products of Examples and Comparative Examples, and FIG. 2 is a graph of hiding power thereof.

Claims (2)

[Claims] 1. Titanium dioxide and an inorganic tabular substance are mixed and pulverized, and a coating layer containing 0.1 to 25% by weight of antimony and the rest substantially consisting of tin oxide is provided on the surface of the particles in a total proportion of 5 to 5. A composite conductive powder having a concealing property, which is contained by 60% by weight. 2. Titanium dioxide and an inorganic flat material are mixed so that titanium dioxide has a ratio of 10 to 90% by weight, and the mixture is pulverized by a dry method or a wet method to obtain an aqueous suspension. Of tin chloride and antimony chloride dissolved in a solution containing hydrochloric acid sufficient to prevent hydrolysis of 10-700 g / l tin chloride and 0.5-180 g / l antimony chloride heated to a temperature of 50 ° C or higher. By adding the mixed solution, the coating layer containing 0.1 to 25% by weight of antimony and the balance substantially consisting of tin oxide was coated in a total proportion of 5 to 60% by weight, and the coated product was filtered and recovered. A method for producing a composite conductive powder having a concealing property, which comprises a step of firing.