JPH0455968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing conductive hydrated silicic acid, and particularly to a simple method for producing white conductive hydrated silicic acid that does not discolor at high temperatures. (Prior art) Hydrous silicic acid is used as a filler for natural rubber and synthetic rubber, as an opacifying agent and anti-blocking agent for various synthetic resins, and as a filler for natural rubber and synthetic rubber.
It is used in a wide range of fields, including paper fillers, paint compounding agents, pesticide adsorption carriers, and viscosity modifiers. In recent years, there has been a demand for hydrated silicic acid having electrical conductivity, particularly in order to impart electrical conductivity to rubber, synthetic resins, paints, paper, etc. as mentioned above. However, hydrated silicic acid is generally an electrical insulator and does not have electrical conductivity. Therefore, for example, JP-A-56-114215~
No. 114218 proposes a white conductive composite powder in which a white metal oxide powder such as titanium oxide is coated with tin oxide or antimony and tin oxide, and a method for producing the same. That is, these manufacturing methods involve adding tin chloride or an alcoholic solution of antimony chloride and tin chloride to a suspension of white metal oxide powder. On the other hand, in order to obtain hydrated silicic acid having good and stable conductivity, the present inventors added a tin compound or a tin compound to the reaction system when producing hydrated silicic acid by neutralizing alkali silicate with acid. He proposed a method of coexisting a compound and an antimony compound (Japanese Patent Application No. 1983-63756). (Problems to be solved by the invention) The present inventors further conducted intensive research on a method for producing silicic acid having electrical conductivity. (Structure of the Invention) As a result, it was discovered that by adding and reacting a tin compound to an alkaline silicate solution containing an antimony compound, hydrated silicic acid that has extremely good conductivity and does not discolor at high temperatures can be obtained. Therefore, the present invention has been provided. According to the present invention, it is presumed that by pre-existing an antimony compound in the alkaline silicate solution, the antimony becomes part of the silica bond and generates the silicate sol solution. In particular, by heating an alkaline silicate solution containing an antimony compound to 60 to 90°C, the production of the silicate sol solution is promoted.
Next, by adding a tin compound to this silicic acid sol solution, it is thought that tin oxide is uniformly contained and precipitated at the same time as the hydrous silicic acid produced. Therefore, the hydrated silicic acid obtained by the present invention can stably exhibit desired conductivity because tin oxide and antimony are uniformly and strongly contained on the surface and inside of the hydrated silicic acid. Does not exhibit coloration even at high temperatures. In the present invention, after producing a silicic acid sol solution containing an antimony compound, it is preferable to add a tin compound to the silicic acid sol solution to produce hydrous silicic acid. It can be easily prepared by generally heating an alkaline silicate solution to 60 to 90°C. In addition, compared to the method of the above-mentioned Japanese Patent Application No. 58-63756, in which an acid is added to an alkaline silicate solution to prepare a silicate sol solution, an antimony compound and a tin compound are added to the silicate sol solution. This method makes it possible to obtain hydrated silicic acid with better conductivity. In the present invention, it is generally preferable to use the antimony compound and the tin compound dissolved in a solvent such as water or alcohol in order to stably and uniformly impart the desired conductivity to the obtained hydrated silicic acid. Therefore, the antimony compound and tin compound need only be soluble in the solvent and exhibit acidity in the solution. For example, halides such as antimony chloride and tin chloride are generally used, and in addition, sulfates, oxides, etc. may also be used as appropriate. In addition, in order to impart desired conductivity to the hydrated silicic acid of the present invention,
Antimony compounds in alkaline silicate solution
It is generally preferred to be present in a proportion of 0.5 to 12% (by weight) relative to SiO ₂ (by weight). That is, if the amount of the antimony compound is less than 0.5% (by weight), the amount of antimony present as a part of the silica bonds in the obtained hydrated silicic acid will be small, and the desired conductivity will not be sufficiently imparted. (wt)%, no further improvement in conductivity is observed. On the other hand, tin compounds are treated with alkaline silicate solution.
The presence of 40-100% (by weight) based on SiO ₂ (by weight) is generally sufficient. That is, the tin compound is
If it is less than 40% (by weight), the desired conductivity cannot be sufficiently imparted to the obtained hydrated silicic acid, and
If the amount is more than 100% (by weight), the final pH during the reaction will be 7.
No further improvement in imparting conductivity was observed. Examples of the alkali silicate of the present invention include sodium silicate, potassium silicate, lithium silicate, and ammonium silicate, which are generally used as an aqueous solution, and in particular, an aqueous solution of sodium silicate (soda) is used industrially. Sodium silicate is
The molar ratio of SiO ₂ and Na ₂ O (SiO ₂ /Na ₂ O) is 1.5 to 3.1
It is preferable that the SiO ₂ concentration is 2 to 10 g/100 ml. If SiO ₂ /Na ₂ O is less than 1.5 or the SiO ₂ concentration is less than 2, it is not only uneconomical but also difficult to produce a silicic acid sol in the subsequent reaction. On the other hand, SiO ₂ /Na ₂ O is 3.1 or more.
If the SiO ₂ concentration is 10 g/100 ml or more, rapid flocculation is likely to occur, making it difficult to produce and control a stable sol. reaction to produce a silicic acid sol solution, and then
The reaction of adding a tin compound to the silicic acid sol solution to produce hydrous silicic acid is greatly influenced by the silicic acid sol production temperature, stirring, and the degree of neutralization when adding the tin compound to the silicic acid sol solution. That is, the silicic acid sol production temperature is generally preferably 60 to 100°C, and if it is lower than 60°C, the viscosity of the reaction liquid becomes high, which affects the specific surface area of the obtained hydrous silicic acid, so it may be adjusted as appropriate. It is desirable that the stirring be sufficiently effective so that the reaction does not occur locally. It is desirable to adjust the degree of neutralization to a final pH of 7 to 10 by adding a tin compound to the silicic acid sol solution, from the viewpoint of the physical properties of the resulting hydrated silicic acid and from the viewpoint of corrosion in the production equipment. The silicic acid slurry after the final reaction is filtered and washed with water in a conventional manner to remove by-product salts, and then dried, pulverized, and classified. Furthermore, if necessary, add 500 to 700% of this hydrated silicic acid.
By firing at a temperature of 1 to 2 hours, hydrous silicic acid having desired conductivity can be obtained. As the firing method, any known method may be used without particular limitation, but an electric furnace or a method of instantaneous contact with flame is preferred. (Effects of the Invention) The thus obtained hydrated silicic acid of the present invention has good conductivity and does not discolor at high temperatures, so it can be used as a filler for, for example, electrical thermal paper, electrostatic recording paper, electrostatic paint, antistatic plastic, rubber material, etc. It is extremely useful as a material. (Example) Examples will be given below, but the present invention is not particularly limited thereto. In addition, the measurement method in Examples is shown below. (1) Specific resistance (Ω・cm) Measured with a Bridge circuit (manufactured by Yokogawa Electric) (2) Whiteness Kett photoelectric whiteness meter (Kett Science Institute) Example 1 SiO ₂ concentration 44.41% and Na ₂ O concentration 21.65 % sodium silicate solution 540ml, water 2460ml and ethanol
A solution containing 14.0 g of antimony chloride dissolved in 100 ml was charged into an internally heated reaction tank with a volume of 5, and the temperature of the solution was adjusted to 40°C.
And so. Next, raise the temperature of this liquid to 90℃, and in this state add 600ml of water.
A solution in which 234 g of tin chloride (SnCl ₄ .xH ₂ O) was dissolved was added over 90 minutes to adjust the pH of the solution to 7.70. The obtained slurry solution was filtered and washed with water to form a cake (water content: 88%
%) was dried at 110°C to obtain hydrous silicic acid. The powder was then crushed and fired in an electric furnace at 650°C for 60 minutes to measure specific resistance and whiteness. The measured values are shown in Table 1. Example 2 In Example 1, 270 ml of sodium silicate solution, water
2730 ml, antimony chloride 7 g, and tin chloride 117 g, but were produced in the same manner. The results are shown in Table 1. Example 3 A product was produced in the same manner as in Example 1 except that the amount of antimony chloride was changed to 28.1 g. The results are shown in Table 1. Example 4 A product was produced in the same manner as in Example 1 except that antimony chloride was changed to 11.2 g and tin chloride was changed to 187 g. The results are shown in Table 1. Example 5 890 ml of a sodium silicate solution with a SiO ₂ concentration of 26.96% and a Na ₂ O concentration of 9.30 and 1110 ml of water were charged into an internally heated reaction tank with a volume of 5, and the liquid temperature was set at 40°C. Next, a solution of 14.4 g of antimony chloride dissolved in 80 ml of ethanol was added over 1 minute. This solution was heated to 60℃ and water
A solution of 117 g of tin chloride dissolved in 2000 ml was added over 90 minutes to adjust the pH to 9.63. The temperature was raised to 90°C again and stirred in this state for 20 minutes. The following products were manufactured in the same manner as in Example 1. The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1. A method for producing hydrated silicic acid having electrical conductivity, which comprises adding a tin compound to an alkaline silicate solution containing an antimony compound. 2. The manufacturing method according to claim 1, wherein the antimony compound is antimony chloride. 3 Add an alkaline silicate solution containing an antimony compound to
After preparing the silicate sol solution by raising the temperature to 60-90℃,
The manufacturing method according to claim 1, wherein a tin compound is added. 4. The manufacturing method according to claim 1, wherein the alkali silicate is sodium silicate. 5 SiO ₂ concentration of sodium silicate is 2 to 10 g/100
The molar ratio of SiO ₂ and Na ₂ O (SiO ₂ /Na ₂ O) in ml is 1.5
~3.1 The manufacturing method according to claim 4. 6 Claim 1 in which the tin compound is tin chloride
Manufacturing method described in section. 7. The manufacturing method according to claim 1, wherein 0.5 to 12% by weight of an antimony compound and 40 to 100% by weight of a tin compound are added to SiO ₂ of the alkaline silicate solution. 8. The manufacturing method according to claim 1, wherein the produced hydrous silicic acid is calcined at 500 to 900°C.