JPH0812332A - Electric conductive powder, its production, electric conductive dispersion liquid and electric conductive coating material - Google Patents

Abstract

PURPOSE:To obtain electric conductive powder having high dispersibility even in a low pH region and in an org. dispersive medium and not causing the problem of deterioration of a coating film component. CONSTITUTION:This electric conductive powder is Al-contg. Sb-doped tin oxide powder. This powder is dispersed in water or an org. dispersive medium to obtain the objective electric conductive dispersion liq. This dispersion liq. is mixed with a resin to obtain the objective electric conductive coating material. Solns. of Sn, Sb and Al compds. are brought into a neutralization reaction and the resultant coprecipitate of hydrates of SnO2, Sb2O3 and Al2O3 is fired to obtain the objective electric conductive powder excellent in dispersibility even at low pH because Al2O3 hating an isoelectric point of about 6 is introduced. Since the surface activity of this electric conductive powder is lower than that of conventional silica, the deterioration of a coating film component can be inhibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antimony-doped tin oxide type conductive powder having excellent conductivity and excellent dispersibility, a method for producing the same, a conductive dispersion and a conductive paint.

[0002]

2. Description of the Related Art Recently, tin oxide powder containing antimony, that is, antimony-doped tin oxide powder has come to be used as a conductive powder. Various improvements have been proposed to improve dispersibility in a dispersion medium (Japanese Patent Laid-Open No. 1-1.
4174, JP-A-3-263705, JP-A-4-6
2713, JP-A-4-77317, and JP-A-4-79.
No. 104).

Conventionally, antimony-doped tin oxide powder has been
Generally, an alkali is added to a solution in which a salt of tin and antimony is dissolved and reacted to precipitate a tin-antimony hydroxide mixture, and unnecessary salts are washed and then collected by filtration, and further 400 ° C or more. It is manufactured by firing at.

Thus, the obtained antimony-doped tin oxide powder is dispersed in various dispersion media to obtain a conductive dispersion liquid, and the conductive dispersion liquid is blended with a resin to form a conductive coating material. By applying to the surface of the material,
An antistatic coating or a conductive coating is formed.

Conventionally, in order to improve the dispersibility of antimony-doped tin oxide powder in an aqueous conductive dispersion, it has been proposed to surface-treat antimony-doped tin oxide powder with silica (JP-A-4-79104). ).

[0006]

In the conventional method described above, silica added for the purpose of improving the dispersibility of the antimony-doped tin oxide powder has an isoelectric point of 2 to 3, and therefore, is neutral or higher. The dispersibility of the antimony-doped tin oxide powder is improved in the pH range of 2 but the dispersibility is deteriorated in the low pH range of pH 4 or lower.

That is, the powder surface potential in water near pH neutral is increased to minus (-) by silica treatment, and particles are repulsed by electrostatic repulsion to improve dispersibility. In particular, silica treatment is effective for enhancing dispersibility in a dispersion medium having a high dielectric constant such as water.

However, the treatment of silica alone results in a pH of 2
Since 3 has the isoelectric point of silica, the dispersibility of the particles is poor in the acidic region and aggregation occurs.

For example, when a conductive dispersion liquid obtained by dispersing antimony-doped tin oxide powder is applied to the surface of a CRT substrate for antistatic purposes and used to prepare a coating material, ethyl silicate and The acid catalyst is added to the zirconium alkoxide. For this reason, the pH in the system finally becomes acidic, but since the isoelectric point is close in the silica treatment as described above, the dispersibility of the antimony-doped tin oxide powder becomes poor.

Further, the silica-treated antimony-doped tin oxide powder has an excessively high surface polarity and is not suitable for dispersion in an organic dispersion medium other than water having a low polarity.

For these reasons, silica treatment does not provide a sufficient effect of improving dispersibility for application to various pH regions or various dispersion media.

Moreover, since the surface of the antimony-doped tin oxide particles treated with silica has high polarity and acidity and the surface is activated, when dispersed in a resin for paint preparation, it gradually increases. However, it may cause decomposition of coating film components.

The present invention solves the above-mentioned problems of the prior art and provides a low p
An object of the present invention is to provide a conductive powder that exhibits high dispersibility even in an H region and an organic dispersion medium, and does not have a problem of deterioration of coating film components, a method for producing the same, a conductive dispersion liquid, and a conductive coating material. .

[0014]

The electroconductive powder according to claim 1 is characterized in that it is made of an antimony-doped tin oxide powder containing aluminum.

The conductive powder according to claim 2 is the conductive powder according to claim 1, in which aluminum is less than 0.1% in terms of Al ₂ O ₃ .
It is characterized by containing 01 to 40% by weight.

The conductive powder according to claim 3 is the conductive powder according to claim 1 or 2.
Conductive powder of 10 to 80 m ² / g
It is characterized by being.

According to a fourth aspect of the present invention, there is provided a method for producing a conductive powder, wherein a co-precipitate of tin oxide, antimony oxide and a hydrate of aluminum oxide is formed by a neutralization reaction from a solution containing a tin compound, an antimony compound and an aluminum compound. Let
It is characterized in that the obtained coprecipitate is fired.

The method for producing a conductive powder according to a fifth aspect is characterized in that, in the method according to the fourth aspect, the liquid pH during the neutralization reaction is 2 or more.

The conductive dispersion according to claim 6 is characterized in that an antimony-doped tin oxide powder containing aluminum is dispersed in water.

A conductive paint according to a seventh aspect is characterized in that the conductive dispersion according to the sixth aspect and a water-soluble resin are mixed.

The conductive dispersion according to claim 8 is characterized in that antimony-doped tin oxide powder containing aluminum is dispersed in an organic dispersion medium.

The conductive paint according to claim 9 is characterized in that the conductive dispersion according to claim 8 is mixed with a resin.

Hereinafter, the present invention will be described in detail.

The conductive powder of the present invention is made of aluminum (A
1) is an antimony-doped tin oxide powder.

In the conductive powder of the present invention, if the Al content is too small, the effect of improving the dispersibility due to the introduction of Al cannot be sufficiently obtained, and if the Al content is too large, the conductivity decreases, so the Al content is reduced. Is aluminum trioxide (alumina: A
It is preferably 0.01 to 40% by weight in terms of (l ₂ O ₃ ).

In the present invention, the composition of the conductive powder is 0.01 to 40% by weight of antimony oxide (Sb ₂ O ₃ ) and A
It is preferable that 0.01 to 40% by weight of 1 ₂ O ₃ and the balance substantially consist of tin oxide (SnO ₂ ).

Further, if the specific surface area of the conductive powder is too large or too small, sufficient dispersibility cannot be obtained, so that 1
It is preferably 0 to 80 m ² / g.

Such conductive powder of the present invention is SnO ₂ , Sb ₂ O ₃ and Al ₂ O by neutralizing by adding an alkali or an acid to a solution containing a tin compound, an antimony compound and an aluminum compound. It can be easily prepared by forming a coprecipitate of each hydrate of ₃ and washing the coprecipitate, and then calcining the coprecipitate at 400 to 900 ° C. for about 0.5 to 5.0 hours. .

As the tin compound, tin chloride (S
_{nCl 4, SnCl 2, SnCl 2} nH 2 O), tin oxychloride _{(SnO · SnCl 2, SnOCl 2} ), stannate, can be used stannates, etc., as the antimony compound, antimony chloride (SbCl _3, SbCl ₅ )
Etc. can be used, and as the aluminum compound,
Aluminum chloride (AlCl ₃ ), aluminate (HAl
O ₂ , H ₃ AlO ₃ ), aluminate (Na ₃ AlO ₃ )
Etc. can be used.

The pH during the neutralization reaction is Sn (OH)
_{4 In} order to improve the production efficiency of the hydrolysis product, it is preferable that the pH is 2 or more, particularly pH 4.0 to 7.0. That is, if the pH is less than 2, hydrolysis of SnCl ₄ or the like is unlikely to occur. The alkali used for this neutralization reaction is
Usual alkalis such as sodium hydroxide and potassium hydroxide can be used, and these are added as an aqueous 0.1-10N alkali solution.

Examples of the acid include hydrochloric acid, sulfuric acid, nitric acid and the like, with hydrochloric acid being particularly preferable, and added as an aqueous solution of 0.1 to 10N.

In the method of the present invention, the method of preparing a solution containing a tin compound, an antimony compound and an aluminum compound and carrying out a neutralization reaction is not particularly limited, and the solution containing the tin compound, the antimony compound and the aluminum compound is treated with an alkali. May be added for neutralization reaction, or one or two of tin compound, antimony compound and aluminum compound, for example, aluminum compound may be added together with alkali for neutralization reaction.

In the electroconductive dispersion of claim 6, the electroconductive powder of the present invention thus obtained is preferably added to water in an amount of 0.1.
It is dispersed at a concentration of about 40% by weight.

The conductive dispersion liquid of claim 8 is obtained by adding the conductive powder of the present invention thus obtained to methanol, ethanol, isopropyl alcohol, butanol, benzene, acetone, ether, toluene, xylene, ethylene glycol, It is preferably dispersed in an organic dispersion medium such as hexane at a concentration of 0.1 to 40% by weight.

The conductive paint according to claim 7 is obtained by mixing the water-based conductive dispersion according to claim 6 with a water-soluble resin, and examples of the water-soluble resin include gelatin, polyvinyl alcohol, water-soluble acrylic resin and the like. Can be used, and the content in the paint is preferably 0.1 to 70% by weight, and the conductive powder content is preferably 0.1 to 70% by weight. In this conductive coating, if necessary, a zirconium compound or the like for improving the coating film refractive index may be mixed in an amount of 0.1 to 20% by weight.

The conductive paint according to claim 9 is a mixture of the organic conductive dispersion according to claim 8 with a resin, and the resin includes phenol resin, alkyd resin, styrene butadiene resin, polyurethane resin, Silicon resin, titanium resin, fluororesin, epoxy resin, vinyl chloride, acrylic resin, ethyl silicate, silicone and the like can be used, and the content in the paint is 0.1 to 70% by weight.
The conductive powder content is preferably 0.1 to 70% by weight. In this conductive coating, if necessary, a zirconium compound or the like for improving the coating film refractive index may be mixed in an amount of 0.1 to 20% by weight.

[0037]

Function: Alumina (Al ₂
O ₃ ) has an isoelectric point of about 6, and therefore, by introducing aluminum into antimony-doped tin oxide, a low p
It is possible to obtain a conductive powder having excellent dispersibility even in an H region or an organic dispersion medium other than water. Moreover, the introduction of aluminum does not excessively increase the activity of the surface of the antimony-doped tin oxide particles, so that there is no problem of deterioration of coating film components when it is made into a paint.

According to the conductive powder of the second aspect, a conductive powder having good conductivity and dispersibility is provided.

According to the conductive powder of claim 3, a conductive powder having a better dispersibility can be provided.

According to the method of claim 4, such a conductive powder of the present invention can be produced easily and efficiently.

According to the method of claim 5, the yield is stable. At a pH lower than this, the efficiency of SnO ₂ precipitation by hydrolysis decreases.

According to the sixth aspect, an aqueous conductive dispersion liquid in which the conductive powder is uniformly dispersed is provided.

According to claim 8, there is provided an organic electroconductive dispersion liquid in which electroconductive powder is uniformly dispersed.

According to claims 9 and 10, there is provided a conductive paint capable of forming a high-performance conductive coating film by using such a conductive dispersion liquid.

[0045]

EXAMPLES The present invention will be described in more detail below with reference to Examples, Comparative Examples and Test Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

Example 1 3 wt.% Of a 60 wt% tin chloride aqueous solution was added to 5 liters of water at 80.degree.
A mixed solution of 90 g and 36 g of a 60 wt% antimony chloride aqueous solution and a 3N aqueous sodium hydroxide solution in which 1.5 g / l of aluminate as aluminum trioxide (Al ₂ O ₃ ) was dissolved had a pH of 6 to 6 in the reaction system. Co-precipitation of hydrates of tin oxide, antimony oxide and aluminum oxide was produced by simultaneous addition over 60 minutes to maintain 7. Next, hydrochloric acid was added to adjust the pH of the reaction system to 3, then filtered, and washed until the electric conductivity of the filtrate became 50 μS or less. After drying the cake obtained, 55 in an electric furnace
It was baked at 0 ° C. for 3 hours and pulverized with a mill to obtain a conductive fine powder.

Example 2 In Example 1, sodium aluminate was replaced with Al ₂ O ₃
Conductive fine powder was obtained in the same manner except that 0.5 g / l of a 3N aqueous sodium hydroxide solution was used.

Example 3 In Example 1, sodium aluminate was replaced with Al ₂ O ₃
Conductive fine powder was obtained in the same manner except that 3 g of a 3N sodium hydroxide aqueous solution having a concentration of 10 g / l was used.

Example 4 A conductive fine powder was obtained in the same manner as in Example 1 except that the temperature of water during the reaction was 50 ° C. and the liquid pH was maintained at 2 to 4.

Example 5 60 wt% tin chloride aqueous solution 3 was added to 5 liters of water at 80 ° C.
A mixture of 90 g and a 60 wt% antimony chloride aqueous solution 36 g and an aqueous solution in which 1.0 g / l aluminum chloride as Al ₂ O ₃ was dissolved, and a 3N sodium hydroxide aqueous solution were used to maintain the pH of the reaction system at 6 to 7. Was added simultaneously for 60 minutes to form a co-precipitate of a hydrate of tin oxide, antimony oxide and aluminum oxide.
Next, hydrochloric acid was added to adjust the pH of the reaction system to 3, then filtered, and washed until the electric conductivity of the filtrate became 50 μS or less. After drying the obtained cake, it was baked at 550 ° C. for 3 hours in an electric furnace and pulverized with a mill to obtain conductive fine powder.

Comparative Example 1 A conductive fine powder was obtained in the same manner as in Example 1, except that sodium aluminate was not added.

Comparative Example 2 A conductive fine powder was obtained in the same manner as in Example 4, except that sodium aluminate was not added.

Comparative Example 3 A conductive fine powder was obtained in the same manner as in Example 5, except that aluminum chloride was not added.

Comparative Example 4 In Example 1, except that a sodium hydroxide aqueous solution in which 1.5 g / l of sodium silicate as SiO ₂ was dissolved was added in place of the sodium hydroxide aqueous solution in which sodium aluminate was dissolved. In the same manner, conductive fine powder was obtained.

Test Example 1 The powder resistance, specific surface area and dispersibility of the conductive fine powders obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were examined by the following method, and the results are shown in Table 1.

The Al ₂ O ₃ content of each conductive fine powder is as shown in Table 1.

Powder Resistance A conductive fine powder was molded into a columnar shape at a pressure of 100 kg / cm ² , and the DC resistance of the molded body was measured, and the specific resistance of the powder was determined by the following formula.

[0058]

[Equation 1]

Specific surface area: 0.1 to 0.5 g of conductive fine powder was sampled,
Degas in nitrogen gas for 0 minutes. Then, a specific surface area measuring device (quick specific surface area measuring device SA-1000 manufactured by Shibata Chemical Co., Ltd.
Type) and the specific surface area was measured by the BET method with nitrogen.

Dispersibility To 1 part by weight of a 17% by weight aqueous conductive slurry of conductive fine powder, 5 parts by weight of ethanol, 4 parts by weight of ethyl silicate (28% by weight), and 1 part by weight of water were sequentially mixed, A test solution was prepared by adding nitric acid so that the pH of this mixed solution became 2.

This prepared solution was put in a graduated cylinder of 100 cc and allowed to stand for a whole day and night, and the degree of sedimentation was examined.

[0062]

[Table 1]

As is clear from Table 1, the electroconductive powder of the present invention is excellent in electroconductivity and is also excellent in dispersion stability in the low pH range. In particular, when it is used in a paint prepared by mixing ethyl silicate, its dispersion stability is effectively exhibited.

[0064]

As described in detail above, the conductive powder of the present invention exhibits excellent dispersibility even in a low pH range and in an organic dispersion medium, and further, deterioration of coating film components when formed into a paint. A high-performance conductive powder that does not have the above problem is provided.

According to the conductive powder of claim 2, a conductive powder having good conductivity and dispersibility is provided.

According to the conductive powder of claim 3, a conductive powder having a better dispersibility is provided.

According to the method of claim 4, such a conductive powder of the present invention can be easily and efficiently manufactured.

According to the method of claim 5, the production efficiency is increased and the yield is stabilized.

According to claim 6, there is provided an aqueous conductive dispersion liquid in which conductive powder is uniformly dispersed.

According to claim 8, there is provided an organic electroconductive dispersion liquid in which electroconductive powder is uniformly dispersed.

According to claims 9 and 10, there is provided a conductive paint capable of forming a high-performance conductive coating film by using such a conductive dispersion liquid.

Claims (9)

[Claims] 1. A conductive powder comprising an antimony-doped tin oxide powder containing aluminum. 2. The conductive powder according to claim 1, which contains aluminum in an amount of 0.01 to 40% by weight in terms of Al ₂ O ₃ . 3. The conductive powder according to claim 1 or 2,
A conductive powder having a specific surface area of 10 to 80 m ² / g. 4. A coprecipitate of a hydrate of tin oxide, antimony oxide and aluminum oxide is produced by a neutralization reaction from a solution containing a tin compound, an antimony compound and an aluminum compound, and the coprecipitate obtained is calcined. A method for producing a conductive powder, comprising: 5. The method for producing a conductive powder according to claim 4, wherein the pH of the liquid during the neutralization reaction is 2 or more. 6. A conductive dispersion liquid obtained by dispersing antimony-doped tin oxide powder containing aluminum in water. 7. A conductive coating material obtained by mixing the conductive dispersion liquid according to claim 6 and a water-soluble resin. 8. A conductive dispersion liquid comprising an antimony-doped tin oxide powder containing aluminum dispersed in an organic dispersion medium. 9. A conductive coating material obtained by mixing the conductive dispersion liquid according to claim 8 and a resin.