JPS61286224A - Production of electroconductive fine powder - Google Patents

Abstract

PURPOSE:To obtain the fine powder having a superior electroconductivity by adding an aqueous hydrochloric acid solution of Sn chloride and Sb chloride and an alkaline aqueous solution into the water in parallel to each other to maintain the pH and by forming the coprecipitate. CONSTITUTION:The aqueous hydrochloric acid solution of Sn chloride and Sb chloride and the aqueous alkaline solution are added into the water in parallel to each other and the pH of the solution is maintained at 2-6. Next, the resultant coprecipitate is filtered, recovered and calcined.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing conductive fine powder that has transparency, and in particular to a method for producing conductive fine powder for use in conductive plastics, electrostatic recording paper, antistatic films, etc. The present invention also relates to a method for producing conductive fine powder useful as a transparency imparting agent and an antistatic agent for chemical fibers and the like.

(Prior art) Carbon black has been known as a conductivity imparting agent for a long time, but this material is black in color, has poor dispersibility in vehicles, and contains carcinogenic substances, making it difficult to use. Currently, it is subject to various restrictions. In contrast, the use of tin oxide powder containing antimony has recently been reported, and methods for producing such powder include, for example, Japanese Patent Publication No. 55-6569, Japanese Patent Application Laid-open No. 71822-1982, and Japanese Patent Application Publication No. 1987-71822. This method has been proposed in, for example, No. 59-182229.

(Problems to be Solved by the Invention) Conventionally proposed methods include, for example, adding an alkaline aqueous solution to a mixed solution of tin chloride, antimony trichloride, and alcohol to dissolve tin hydroxide and antimony hydroxide. A method of forming a coprecipitate, heating the coprecipitate at a temperature of about 80°C, ripening it, and then firing it (Japanese Patent Publication No. 55-6569)
, add a solution of tin chloride and antimony chloride in alcohol, hydrochloric acid, or acetone and an alkali to hot water,
Method for maintaining reaction at H8 or higher (Japanese Unexamined Patent Publication No. 57-71
No. 822), a tin chloride solution is added to an alkaline aqueous solution with a pH of 10 or higher while keeping it at 65°C or higher, the pH is finally adjusted to 5 or lower to obtain a product, and this is calcined to form tin oxide fine powder. Manufacturing method (Japanese Patent Application Laid-Open No. 59-182229
No.) etc. Such conventional methods require heating of the reaction solution, and since the conductivity of the resulting powder is still not satisfactory, improvements are desired.

The present invention particularly relates to an industrial method for producing fine antimony-containing tin oxide powder with excellent conductivity without heating.

(Means for Solving the Problems) The present invention provides a method of adding an aqueous alkali solution to a solution of tin chloride and antimony chloride when neutralizing the solution of tin chloride and antimony chloride with an alkali at room temperature; On the contrary, the method of adding a solution of tin chloride and antimony chloride to an alkaline aqueous solution does not yield fine antimony-containing tin oxide powder with excellent conductivity.
In a neutralization method in which a solution of tin chloride and antimony chloride and an alkaline aqueous solution are added in parallel, a fine powder with extremely high conductivity is surprisingly obtained, especially when the pH is constantly maintained at 2 to 6 during neutralization. This is based on the knowledge that it can be obtained.

That is, the present invention provides a method for producing conductive fine powder consisting of a coprecipitate of tin oxide and antimony oxide by neutralizing a solution of tin chloride and antimony chloride with an alkali,
A hydrochloric acid aqueous solution and an alkali aqueous solution of tin chloride and antimony chloride are added to water to maintain the pH of the neutralization reaction solution at 2 to 6 to produce a coprecipitate of hydrated tin oxide and antimony oxide. This is a method for producing a conductive fine powder, which is characterized in that the coprecipitate is recovered from the reaction solution and calcined.

The conductive fine powder obtained by the method of the present invention contains 5 to 30% by weight of antimony oxide, preferably 15 to 2% by weight, based on 5b2o.
Contains 5% by weight, and the remainder is essentially tin oxide (Sn○2)
It has a composition consisting of: and a particle size of 0.01 to 0.2μ. If the amount of antimony oxide is too small than the above range, it will be difficult to obtain the desired conductivity, and if it is too large, the coloration due to antimony oxide will become strong, which is not preferable.

In the method of the present invention, first, a hydrochloric acid aqueous solution and an alkaline aqueous solution of tin chloride and antimony chloride are added to water so as to maintain the pH of the neutralization reaction solution at 2 to 6, thereby forming a hydrate of tin oxide and antimony oxide. to form a coprecipitate. In this case, a hydrochloric acid aqueous solution and an alkali aqueous solution of tin chloride and antimony chloride are mixed so that the pH of the neutralization reaction solution is maintained at an acidic side of 2 to 6, preferably at a pH of 2 to 4, and particularly preferably at a pH of 2 to 3. It is important to neutralize by adding in parallel. If the neutralization method is different from this, for example, adding an alkaline aqueous solution to an aqueous hydrochloric acid solution of tin chloride and antimony chloride, or conversely, adding a hydrochloric acid aqueous solution of tin chloride and antimony chloride to an alkaline aqueous solution, ,
Antimony-containing tin oxide powder having desired conductivity cannot be obtained. Note that the above-mentioned addition in parallel also means adding the hydrochloric acid aqueous solution and the alkaline aqueous solution separately and continuously or intermittently so as to maintain the pH of the neutralization reaction solution within a predetermined range. include. Furthermore, in the method of the present invention, the hydrochloric acid aqueous solution of tin chloride and antimony chloride can be added either by adding the side group acid aqueous solution separately or by adding the tin chloride and antimony chloride in a pre-mixed and dissolved form in the hydrochloric acid. Although it is possible, it is preferable to add a pre-mixed solution in terms of simulation.

The method of the present invention is an industrially advantageous method because the neutralization reaction can be carried out at room temperature without heating, but it may be carried out with heating if necessary, in which case the conductivity can be further improved. I can do it.

When the pH at the time of neutralization is lower than the above range, it becomes difficult to obtain a coprecipitate of tin oxide and antimony oxide hydrate,
Moreover, if it becomes high, although a coprecipitate can be obtained, it becomes difficult to obtain powder with excellent conductivity.

The time required for neutralization varies depending on the amounts of tin chloride and antimony chloride, and is generally between 20 minutes and 20 minutes, although it cannot be generally specified.
4 hours, preferably 30 minutes to 2 hours is sufficient.

The concentrations of tin chloride and antimony chloride in an aqueous hydrochloric acid solution are as follows: antimony oxide in the conductive fine powder is S b20 z
5 to 30% by weight, preferably 15 to 25% by weight
tin oxide, with the remainder consisting essentially of tin oxide.

Examples of the alkali in the aqueous alkali solution used as a neutralizing agent include alkali metal hydroxides, carbonates, and ammonia such as sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

In the method of the present invention, the coprecipitate is then collected by filtration and washing from the reaction solution after the neutralization reaction, but the pH of the reaction solution before collecting the coprecipitate is also the same as the pH at the time of the neutralization reaction. It is important that it is maintained within the range of ~6. Even if the neutralization reaction is carried out so that the pH is maintained at 2 to 6, if the final pH of the reaction solution before collecting the coprecipitate deviates from this range, it is difficult to obtain the desired conductive fine powder.

The recovered coprecipitate is then dried as necessary and then dried for 40 minutes.
After baking at a temperature of 0 to 1,200°C, preferably 500 to 700°C to obtain antimony-containing tin oxide, it is subjected to a conventional pulverization treatment to form a conductive fine powder with a particle size of 0.01 to 0.2μ. . If the firing temperature is too low than the above range, the firing will be insufficient and it will be difficult to obtain the desired conductivity. If the firing temperature is too high, the powder particles will sinter with each other, resulting in particles that remain transparent even after subsequent pulverization. It cannot be made into a powder of the diameter. The firing time is suitably 30 minutes to 5 hours, preferably 1 to 2 hours.

Example 1 Tin chloride<5nCI2- in 1g of water at room temperature (25°C)
・5H20) 232°6g and antimony chloride (S
b+OL) 25,0 g in 3N-hydrochloric acid solution 500c
A solution of tin oxide and a 10% aqueous solution of 7 um hydroxide were added in parallel over a period of 60 minutes to maintain the pH of the system at 2 to 3 to form a coprecipitate of hydrated tin oxide and antimony oxide. was generated. Note that the final pH of the reaction solution after the coprecipitate was formed was 2.5. Next, the coprecipitate was filtered, washed and collected until the specific resistance of the filtrate reached 50 μs. After drying the recovered coprecipitate, it was calcined in an electric furnace at 700°C for 1 hour, and then pulverized with a pulperizer to have an average particle size of 0.
A conductive fine powder of 0.09μ was obtained.

Example 2 The same procedure as in Example 1 was carried out except that the pH at the time of neutralization was maintained at 4 to 5. In this example, the pH after neutralization was 4.6, so hydrochloric acid was added to adjust the final pH to 3.0.

Example 3 The same procedure as in Example 1 was carried out except that 1 ρ of 70° C. heated water was used. Note that the final pH after neutralization was 2.9.

Example 4 The same procedure as in Example 1 was carried out except that 1 g of heated water at 70° C. was used and the pH during neutralization was maintained at 4 to 5. In addition, in this example, the pH after neutralization was 5.0, so hydrochloric acid was added and the final pH was adjusted to 3.0! :It was adjusted.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the pH at the time of neutralization was maintained at 6 to 9. In this comparative example, the final pH after neutralization was adjusted to 7.0.

Comparative Example 2 The same procedure as in Comparative Example 1 was carried out except that the final pH was adjusted to 3.0.

Comparative Example 3 The same procedure as in Example 3 was carried out except that the pH at the time of neutralization was maintained at 6 to 9. In this comparative example, the final pH after neutralization was set to 7. OI: Adjusted.

Comparative Example 4 The same procedure as in Comparative Example 3 was carried out except that the final pH was adjusted to 3.0.

Comparative Example 5 The same procedure as in Example 1 was carried out except that the final pH was adjusted to 9.0.

Comparative Example 6 In water IQ at room temperature (25°C), tin chloride (SnCL*
5H20) and 232.6 g of antimony chloride (SbC
A solution of 25.0 g of ρ, ) dissolved in 500 cc of 3N hydrochloric acid solution was added over 30 minutes. Thereafter, a 10% aqueous sodium hydroxide solution was added over 40 minutes while stirring so that the final pH of the suspension was 3.0, and then filtered, washed, and dried in the same manner as in Example 1. processed.

Comparative Example 7 Comparative Example 6 was treated in the same manner as in Comparative Example 6, except that an aqueous sodium hydroxide solution was added so that the pH at the end of neutralization was 7.0.

Comparative Example 8 Comparative Example 6 was treated in the same manner as in Comparative Example 6 except that 1 g of 70° C. heated water was used.

Comparative Example 9 Comparative Example 6 was treated in the same manner as in Comparative Example 6, except that heated water IQ at 70° C. was used and an aqueous sodium hydroxide solution was added so that the pH at the end of neutralization was 7.0.

Test Example 1 The powder resistance (Ωc+n) of the antimony-containing tin oxide fine powders obtained in the Examples and Comparative Examples was measured by the following method, and the results shown in Table 1 were obtained.

(Evaluation of Powder Resistance) The sample powder was molded at a pressure of 100 Kg/am2 to form a cylindrical compact (diameter 18 mm, thickness 3 mm), and its DC resistance was measured.

Note that the average particle size was measured by electron microphotography, but the fine powders of Comparative Examples 6 to 9 were extremely irregular, making it difficult to measure the average particle size.

Table 1 Example 1 Parallel addition 25 2-3 2.5 1,
7 0.092〃〃4~53.02,0 0.1 3〃F0 2~3
2.9 1.0 0. Q54〃〃4
~53.01,4 0.06 Comparative Example 1 Parallel addition 25 6-9 F,0 1.2
X104 0,1'l // // // 3
,08,5 0.13 1/70 II 7.
010.9 0.094 II II II
3.06.0 0.085 II 25 2-39
．． 04.3X1020.096 bulk addition 1/
-3,017,50,1~2f II
II -7,0
2,7X10' 0.1~1.58 1/70
- 3.015.80.08-19 II II
-7,04,2
:28%) and then coated on a plastic film (trade name: 7 JITATSUKU, manufactured by Fuji Photo Film Co., Ltd.). The dry film thickness of the coating film was 2μ.

The transmittance of this coating film at a wavelength of 550 nm was measured using a self-recording spectrophotometer UV-240 (manufactured by Takasu Seisakusho), and the result was a good value of 88.9%. Further, the surface resistance of this coating film was measured using a digital ohmmeter model R-506 (manufactured by Kawaguchi Electric Co., Ltd.) and found to be 1.0×10 SΩ/mouth.

A similar test was conducted on the antimony-containing tin oxide fine powder obtained in Example 1, and similar results were obtained.

(Effects of the Invention) As is clear from the results of Test Examples 1 and 2, it can be seen that the method of the present invention provides excellent conductive fine powder even at room temperature.

Claims (1)

[Claims] In a method for producing conductive fine powder consisting of a coprecipitate of tin oxide and antimony oxide by neutralizing a solution of tin chloride and antimony chloride with an alkali, a hydrochloric acid aqueous solution and an alkali aqueous solution of tin chloride and antimony chloride are added to water. The pH of the neutralization reaction solution is maintained at 2 to 6 to form a coprecipitate of hydrated tin oxide and antimony oxide, and then the coprecipitate is collected from the reaction solution and calcined. A method for producing conductive fine powder, characterized by: