JPH05294631A - Production of electrically-conductive powder coated with tin oxide doped with antimony oxide - Google Patents

Abstract

PURPOSE:To provide a whitish superconducting powder showing white or a color, having electrically conductive function. CONSTITUTION:In coating the surface of inorganic powder with tin oxide doped with antimony oxide, an aqueous solution of hydrochloric acid of tin chloride and an alkali aqueous solution are simultaneously added to an aqueous solution suspending the inorganic powder, the inorganic powder is coated with tin hydrate precipitated by hydrolysis, successively a mixed aqueous solution of hydrochloric acid of tin chloride and antimony chloride and the alkali aqueous solution are simultaneously added to the solution to give a tin hydrate containing antimony hydrate coprecipitated on the inorganic powder coated with the tin hydrate. The tin hydrate is heated and burnt and an oxide tin layer doped with antimony oxide is formed to produce electrically conductive powder. Consequently, powder obtained by this method is observed to have much more improved effects on electrical conductivity than powder coated with the same amount by the conventional method and a raw material supply source is widened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white conductive powder capable of imparting a white or colored conductive function to paper, fibers, blastics, rubber, coating films and the like.

[0002]

2. Description of the Related Art In recent years, antistatic or conductive plastics such as electrophotographic equipment, semiconductor manufacturing and computer room building materials, recording paper, automobile weight reduction plastics members, paints, etc. have become white or colored. However, powders having a tin oxide-based conductive coating layer have been used in place of carbon black and metal-based powders.

Generally, for the above-mentioned use, a white conductive powder having a tin oxide film doped with antimony oxide formed on the surface of titanium dioxide powder, which is a typical white pigment, is disclosed in Japanese Patent Application Laid-Open No. 58-209002. Kosho 60-21
553, JP-A-61-286221, JP-A-62-180903, and JP-A-2-149415 are known, and these coating methods are based on titanium dioxide (TiO ₂ ) powder as a base material in an aqueous solution. In this method, a mixed solution of tin chloride and antimony chloride and an alkaline solution are simultaneously added to hydrolyze antimony and tin to coprecipitate on the surface of the substrate.

[0004]

However, in the above-mentioned conventional manufacturing method, there is a marked difference in the conductivity of the powder produced depending on the properties of the TiO ₂ powder used as the base material.
When O ₂ is of anatase type, and even of rutile type, when the content of alkali metal is large, the conductivity is low, and there is a problem that the supply source of the raw material base material powder is limited.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for producing a conductive inorganic powder which is stable and has excellent characteristics.

[0006]

In order to achieve the above object, the inventors of the present invention have conducted extensive studies, and as a result, antimony oxide to be doped to improve conductivity is anatase-type TiO 2.
It was found that it was consumed by reacting preferentially with ₂ and was not sufficiently doped, and this was avoided to complete the present invention.

[0007]

DISCLOSURE OF THE INVENTION That is, the gist of the present invention is that when a surface of an inorganic powder is coated with tin oxide doped with antimony oxide, first, an aqueous hydrochloric acid solution of tin chloride and an alkali are added to an aqueous solution in which the inorganic powder is suspended. An aqueous solution and an inorganic powder suspension aqueous solution are simultaneously added, and tin hydrate is precipitated by hydrolysis to coat the solution, and then a mixed hydrochloric acid aqueous solution of tin antimony chloride and an alkaline aqueous solution are simultaneously added to this solution. Then, the above-mentioned tin hydrate-coated inorganic powder is further coated with a tin hydrate containing a co-precipitated antimony hydrate, and the thus-obtained coated powder is heated and fired to produce antimony oxide. A method for producing a conductive powder having a doped tin oxide coating.

[0008]

The structure and operation of the present invention will be described. In the present invention, in an aqueous solution in which an inorganic powder is suspended as in the prior art, a hydrochloric acid aqueous solution of tin chloride and antimony chloride and an alkaline aqueous solution are simultaneously added, without causing a hydrolysis coprecipitation reaction of antimony and tin, First, it is characterized in that a tin hydrate film is formed on the surface of the inorganic powder.

The reason why the conductivity of the powder obtained as described above differs from that of the conventional one is not clear, but antimony oxide, which is a doping component, reacts with anatase-type TiO ₂ in some way. It is estimated that this is because it is consumed with. For example, in the film formation in the conventional simultaneous hydrolysis film formation method, the formation of antimony oxide first occurs and is consumed by the reaction for promoting the rutile conversion of the anatase-type TiO ₂ surface, and the doping of antimony oxide performed in the subsequent formation of the tin oxide film is performed. It is possible that the following mechanism is followed.

[0010] Similar considerations alkali titanate fiber (formula _{aM 2 O · TiO 2 · bH} 2 O ( where M is Li, N
a, K, etc.), flat micaceous powder (general formula X _0.5-1.0 Y _2-3 Z ₄ O ₁₀ (OH, F) ₂ (where X is N
a, K, Ca, Ba, Rb, Sr, etc., Y is Mg, Fe,
Ni, Mn, Al, Li, etc., Z is Si, Ge, Al, F
e, B, etc.) and the novel synthetic fluoromica (general formula αMF · β (aMgO · γ) described in JP-A-2-149415.
SiO ₂ )) also occurs, and the antimony oxide that is the doping agent reacts with the alkali component, and is easily consumed for the production of alkali antimonate, so that the conductive performance deteriorates.

According to the present invention, by preventing the above-mentioned consumption of antimony oxide, the anatase type TiO ₂
It is now possible to obtain a product that does not reduce the conductivity even if powder is used as the base material.

The ratio of the coating oxide layer to the base inorganic powder in the present invention is 1 to 30 wt%, preferably 5
~ 25 wt%. If it is less than 1 wt%, the inorganic powder cannot be completely covered, and the required conductivity cannot be obtained. Further, if it exceeds 30 wt%, there is no effect in improving the conductivity, which is uneconomical. The antimony in the antimony oxide-doped tin oxide film is 0.1 to 20 wt% and the balance is substantially tin oxide. Antimony in the film is 0.1
If it is less than 20%, a sufficient doping effect is not exhibited and 20%
When it exceeds, the whiteness tends to be reduced due to grayish or blue color, the utility value as a white conductive material is lowered, and it is expensive and disadvantageous in use.

By the hydrolysis reaction, a water-insoluble hydrate is deposited from the aqueous solution on the surface of the inorganic powder. The solid matter is separated from the reaction solution by filtration, decantation, centrifugation or the like, washed with water and dried. Subsequently, it is carried out in a predetermined conductivity and stability, but it may be carried out in an inert or moderately reducing atmosphere in order to enhance the conductivity. Examples of the inorganic powder to be used include titanium oxide which is a general white pigment, alkali titanate, mica powder, silica, alumina, zinc white, zirconia, magnesia, and the like.
It is desirable that the average particle size is adjusted to 0.15 to 5.0 μ. In particular, excellent results are obtained with anatase-type titanium oxide, alkali titanate and mica powder. As the alkaline aqueous solution used for hydrolysis, sodium hydroxide,
Examples thereof include alkali metal hydroxides such as potassium hydroxide, sodium carbonate and potassium carbonate, carbonates and ammonia.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The constitution and effects of the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

Example 1 Anatase type titanium dioxide powder (Co., Ltd.)
Tochem Products, trade name TCA555) (average particle size 0.2 μm, whiteness 92, specific surface area 8.5 m ² / g) 1
After stirring and dispersing 00 g in 0.3 liter of pure water and maintaining it at 90 ° C., an acidic aqueous hydrochloric acid solution containing 3.5 g of stannic chloride was added, and then an aqueous NaOH solution (75 g / liter) was added at a pH of 2 to 2.
4 was gradually added dropwise over 10 minutes so as to be hydrolyzed to form a tin hydrate film on the powder.

Next, the above solution was maintained at 90 ° C., and an acidic aqueous hydrochloric acid solution containing 14 g of stannic chloride and 5 g of antimony (III) chloride and an aqueous NaOH solution (75 g / liter) were added to adjust the pH to 2 to 4. Then, the hydrated coprecipitate of tin and antimony was coated on the powder having a coating film of tin hydrate so as to be simultaneously added dropwise over 30 minutes. The powder obtained was filtered, washed with water, dried (100 ° C.), and then calcined at 550 ° C. for 1 hour. As a result, with a yield of 110 g (coating amount 10% by weight),
A conductive white powder having a volume resistivity of 5 Ω · cm (under a pressure of 100 kg / cm ² ) and a whiteness of 82 was obtained.

[0016]

Example 2 Potassium titanate fiber (Kubota Corp., trade name TXAX-C) (fiber length 15 μm, diameter 0.3 μm) 1
While stirring and dispersing 00 g in pure water 0.3 liter and maintaining at 95 ° C., an acidic hydrochloric acid aqueous solution containing 7 g of stannic chloride was added and mixed, and an aqueous NaOH solution (75 g / liter) was added over 20 minutes. Next, while maintaining the solution at 95 ° C., a hydrochloric acid acidic aqueous solution containing 27 g of stannic chloride and 5 g of antimony (III) chloride and a NaOH aqueous solution (75 g / liter) were adjusted to pH 2-4. The hydrated coprecipitate of tin and antimony was coated on the fibers having the tin hydrate coating by dropping simultaneously for 30 minutes. The fibers were filtered, washed with water, dried (100 ° C.), and then calcined at 550 ° C. for 1 hour. As a result, a conductive white fiber having a volume resistivity of 8 Ω · cm and a whiteness of 79 was obtained with a yield of 119 g (coating amount: 19% by weight).

[0017]

Example 3 Fluorine mica powder (Corp Chemical Co., Ltd.)
Co., Ltd., trade name MK-100) (average particle size 2 μm, specific surface area 3.7 m ² / g, whiteness 95) was coated in the same manner as in Example 1. As a result, with a yield of 111 g (coating amount 10% by weight), the volume resistivity was 7 Ω · cm,
A conductive white mica having a whiteness of 83 was obtained.

[0018]

Comparative Example 100 g of the anatase-type titanium oxide powder used in Example 1 was stirred and dispersed in 0.3 liter of pure water,
The temperature was maintained at 90 ° C., and an acidic aqueous hydrochloric acid solution containing 17 g of stannic chloride and 2.5 g of antimony (III) chloride and an aqueous NaOH solution (75 g / liter) were simultaneously added dropwise over 40 minutes so that the pH became 2 to 4. I did.

The powder obtained is filtered, washed with water and dried (100
C.) and calcined at 550.degree. C. for 1 hour. As a result 10
Yield of 9 g (10 wt% coating amount), volume resistivity 3
It was a conductive white powder having 70 Ω · cm and whiteness of 76.
The results are summarized in Table 1.

[0020]

[Table 1] No. Base powder Whiteness Volume resistivity (Ω · cm) Example 1 Anatase type titanium dioxide 82 5 〃 2 Potassium titanate fiber 79 8 〃 3 Fluorine mica 83 7 Comparative example Anatase type titanium dioxide 76 370

[0021]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, a remarkable conductivity improving effect is recognized as compared with the powder coated with the same amount by the conventional method, and particularly, anatase type titanium oxide, The effect on alkali titanate fiber and micaceous powder is remarkable, and the raw material source is expanded, which is extremely useful industrially.

Claims (4)

[Claims] 1. When coating the surface of an inorganic powder with tin oxide doped with antimony oxide, first, a hydrochloric acid aqueous solution of tin chloride and an alkaline aqueous solution are added to the aqueous solution in which the inorganic powder is suspended. Simultaneously added, the tin hydrate was deposited by hydrolysis to coat it, and then a mixed hydrochloric acid aqueous solution of tin antimony chloride and an alkaline aqueous solution were simultaneously added to this solution to coat the tin hydrate. Production of a conductive powder having an antimony oxide-doped tin oxide coating, which comprises coating an inorganic powder with tin hydrate containing co-precipitated antimony hydrate, and heating the coated powder thus obtained Method. 2. The method for producing a conductive powder according to claim 1, wherein the inorganic powder is titanium oxide, alkali titanate, mica powder, silica, alumina, zinc white, zirconia or magnesia. 3. The method for producing a conductive powder according to claim 1, wherein the titanium oxide is anatase type. 4. The method for producing a conductive powder according to claim 1, wherein the ratio of the coating oxide layer to the inorganic powder is 1 to 30 wt%.