JPH06183708A - Electric conductive white powder - Google Patents

Abstract

PURPOSE:To provide improved electric conductive white powder whose whiteness is not deteriorated. CONSTITUTION:A white pigment with an electric conductive layer of tin oxide doped with antimony oxide is prepd. and at least one of phosphorus, aluminum and molybdenum is incorporated into the coating layer by 0.1-7wt.% (expressed in terms of oxide).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white conductive pigment powder capable of imparting a highly white conductive function to paper, fibers, plastics, rubbers, coating films and the like.

[0002]

2. Description of the Related Art In recent years, whiteness has been especially required for interior materials of automobile light weight plastic member conductive primers, semiconductor manufacturing clean rooms and computer rooms, hospitals and the like, carpets and the like. Therefore, white conductive powder such as aluminum oxide-doped zinc oxide and titanium dioxide powder, which is a typical white pigment, is formed with a tin oxide film doped with antimony oxide on the surface thereof (JP-A-58). -209002, JP-A-61-28622, JP-A-62-180903, etc.) are known.
However, in any of the conductive powders, when an additive element (Sb or the like) for doping conductivity is doped, the original whiteness of the white pigment is lost, and there is a problem that the whiteness is lowered and the tint is unavoidable. there were.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a conductive powder having high whiteness and suppressed tint.

[0004]

Means for Solving the Problems As a result of intensive studies aimed at achieving the above object, the present inventors have found that antimony oxide-doped tin oxide coating a white pigment contains phosphorus, aluminum and molybdenum as a third element. I found that the problem was solved.

[0005]

According to the present invention, 0.1 to 7 wt% of at least one of phosphorus, aluminum and molybdenum as an oxide is used.
An electrically conductive white pigment powder coated with an electrically conductive layer of antimony oxide-doped tin oxide is provided.

More specifically, when the surface of the white pigment is coated with tin oxide doped with antimony oxide, that is, the white pigment is suspended in an aqueous solution, and a mixed hydrochloric acid aqueous solution of tin antimony chloride and an aqueous alkaline solution are mixed. When the white pigment is coated with tin oxide hydrate containing antimony hydrate by adding at the same time, aluminum compound, phosphorus compound and molybdenum compound are previously dissolved in a mixed hydrochloric acid aqueous solution or an alkaline aqueous solution to form a hydrate. A coating containing these compounds is performed, and this is heated and baked to provide a white conductive powder having a coating of antimony oxide-doped tin oxide containing at least one of aluminum, molybdenum and phosphorus.

The ratio of the coating oxide to the base white pigment in the present invention is 1 to 40% by weight, preferably 5 to
It is 30 wt%. If it is less than 1 wt%, the substrate cannot be completely covered and the required conductivity cannot be obtained. Moreover, even if it exceeds 40 wt%, there is no effect in improving the conductivity, which is uneconomical. The antimony of the coating oxide layer is 0.1 to 20 wt% with respect to the coating amount, and if it is less than 0.1 wt%, a sufficient doping effect is not exhibited and 20 wt%
Even if it exceeds the above, the effect is not seen again, and instead, blue and gray are exhibited, and the whiteness decreases. Aluminum, phosphorus and molybdenum are 0.1 to 7 wt% with respect to the coating amount. 0.1 wt
If it is less than%, the whiteness and tint are not improved, and it is 7 wt.
If it exceeds%, the conductivity will decrease. In the method of the present invention, a water-insoluble hydrate is deposited from the aqueous solution on the surface of the white pigment by the hydrolysis reaction. The solid matter is washed with water, solid-liquid separated and dried from the reaction solution. Subsequently, in order to obtain a predetermined conductivity, firing is performed in an inert or moderately reducing atmosphere.

Examples of the white pigment used include titanium oxide, zinc oxide, alkali titanate, micaceous powder, silica, alumina, zirconia, magnesia, and the like.
It is desirable that the average particle size is adjusted to 0.1 to 5 μm. As a raw material for tin oxide and antimony oxide, there are chlorides, organic compounds (alkoxides) and the like, but chlorides are preferable. Examples of the alkaline aqueous solution used for hydrolysis include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, carbonates and ammonium.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail with reference to Examples.

Example 1 Rutile-type titanium dioxide powder (TOKEM PRODUCTS, trade name TCR) (specific surface area 7 g / m ²
(Average particle size 0.2 μm), Whiteness (L value) 92) 100 g
Was stirred and dispersed in 0.3 l of pure water, and while maintaining this at 90 ° C., an acidic aqueous hydrochloric acid solution containing 34 g of stannic chloride and 5 g of antimony trichloride and sodium hexametaphosphate ((NaP
An aqueous solution of sodium hydroxide (50 g) containing 0.7 g of O ₃ ) ₆ )
0 g / l) and 50 ml were simultaneously added dropwise over 30 minutes to coat with tin oxide containing phosphorus and a hydroxide coprecipitate of antimony oxide. Wash with water, filter and dry (100
C.), and then baked (600.degree. C., 1 hour). The obtained 121 g of white powder (the coating amount containing 1 wt% of phosphorus is 20 wt%) has a whiteness (L value) (Suga Test Instruments Co., Ltd. color computer) 88, and a volume resistance value of 7 Ω · cm (100 k
g / cm ² pressed powder).

[0010]

Example 2 As in Example 1, a white powder was produced using an aqueous sodium hydroxide solution containing 0.3 g of sodium aluminate (NaAlO ₂ ). 120 g of the obtained white powder (a coating amount of 20 wt including aluminum 0.8 wt%
%, The whiteness was 87 and the volume resistance was 2 Ω · cm.

Example 3 As in Example 1, a white powder was produced using an aqueous sodium hydroxide solution containing 0.75 g of sodium molybdate (Na ₂ MoO ₄ .2H ₂ O). The obtained 122 g of white powder (the coating amount including 2.5 wt% of molybdenum is 21 wt%) has a whiteness of 89 and a volume resistance value of 9 Ω · c.
It was m.

[Comparative Example 1] Rutile type titanium dioxide powder (TOKEM PRODUCTS, trade name TCR) (specific surface area 7 g / m ²
(Average particle size 0.2 μm), Whiteness (L value) 92) 100 g
Was stirred and dispersed in 0.3 l of pure water, and while maintaining it at 90 ° C., an acidic aqueous hydrochloric acid solution containing 34 g of stannic chloride and 5 g of antimony trichloride and an aqueous sodium hydroxide solution (500 g /
l) 50 ml and 50 ml are simultaneously added dropwise over 30 minutes,
It was coated with a hydroxide coprecipitate of tin oxide and antimony oxide. After washing with water, filtering and drying (100 ° C), baking (600
(° C., 1 hour). The obtained 120 g of white powder (the coating amount is 20 wt%) has a volume resistance value of 6 Ω · cm (100 k
g / cm ² ) was good, but the whiteness was as low as 78.

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Claims (3)

[Claims] 1. A conductive white pigment powder coated with a conductive layer of antimony oxide-doped tin oxide containing 0.1 to 7 wt% of at least one of phosphorus, aluminum and molybdenum as an oxide. 2. The white pigment is titanium oxide, zinc oxide,
The method for producing a conductive powder according to claim 1, wherein the conductive powder is alumina, silica, zirconia, magnesia, alkali titanate, or mica powder. 3. The conductive powder according to claim 1, wherein the ratio of the coating oxide layer to the white pigment is 1 to 40 wt%.