JPH0460924B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing hydrated silicic acid having electrical conductivity. Hydrous silicic acid has been used in a wide range of fields, including as a filler for natural rubber and synthetic rubber, an opacifying agent and anti-blocking agent for various synthetic resins, a filler for paper, a compounding agent for paints, a pesticide sprayer, and a viscosity regulator. . 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 has the problem of generating static electricity when heat treated at high temperatures. Therefore, for example, JP-A-56-114215-114218
The publication proposes a white conductive composite powder made by coating a white metal oxide powder such as titanium oxide 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. The present inventors also conducted extensive research in order to develop a simple method for producing hydrated silicic acid having conductivity. As a result, when producing hydrous silicic acid by neutralizing alkali silicate with acid, extremely good conductivity can be achieved by coexisting a soluble tin compound or a soluble antimony compound and a tin compound in the reaction system. The present invention has been based on the discovery that hydrous silicic acid can be obtained which does not generate static electricity at high temperatures. According to the present invention, when an alkali silicate is neutralized with an acid, by allowing a tin compound and an antimony compound to coexist in the reaction system, tin oxide is uniformly contained and precipitated at the same time as the hydrous silicic acid produced, and antimony is added to the silica. It is assumed that they coexist as part of the bond. Therefore, the hydrated silicic acid obtained according to the present invention can stably exhibit desired conductivity because tin oxide and antimony are strongly contained on the surface and inside the hydrated silicic acid. The present invention can be carried out according to the known method of producing hydrated silicic acid by neutralizing an alkali silicate with an acid. That is, the method for producing such hydrous silicic acid is not particularly limited, but in order to obtain fine hydrous silicic acid,
It is preferable to generate an aqueous silicic acid sol solution in advance. However, when a predetermined amount of a tin compound is added to an alkali silicate, gelation occurs during precipitation of silicic acid particles, making stirring difficult, making it impossible to satisfactorily prepare an aqueous silicic acid sol solution. Therefore, in the present invention, after preparing an aqueous silicic acid sol solution by adding an acid to an alkali silicate, by adding a predetermined amount of a tin compound to the aqueous solution, fine hydrated silicic acid having good conductivity is produced. can be manufactured. On the other hand, the present invention obtains fine hydrated silicic acid having better conductivity by preparing a silicic acid sol aqueous solution in the presence of an antimony compound and then producing hydrated silicic acid in the presence of a tin compound. I can do it. Generally, an acid is added to an alkaline silicate solution containing an antimony compound to precipitate some of the silicic acid particles, and then a tin compound (or a tin compound and an alkali silicate) is added, and then an acid is added to adjust the pH. A method that allows silicic acid particles to be completely precipitated is recommended. Alternatively, after preparing a silicic acid sol solution by adding an acid to an alkaline silicate solution, adding an antimony compound and a tin compound, and then adjusting the pH by adding an acid, fine hydrated silicic acid having the desired conductivity can be obtained. You can also get it. However, when an antimony compound and a tin compound are added after silicic acid particles are completely precipitated by adding an acid to an alkaline silicate solution, desired conductivity cannot be imparted to the obtained hydrous silicic acid. 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 for example, halides such as antimony chloride and tin chloride are generally used, and sulfates, oxides, etc. are also used as appropriate. In addition, in order to impart desired conductivity to the hydrated silicic acid of the present invention, an antimony compound is generally added in an amount of 0.5 to 10% relative to SiO ₂ (weight) in an alkaline silicate solution.
(by weight)%.
In other words, if the antimony compound is less than 0.5% (by weight), the desired conductivity cannot be imparted to the obtained hydrated silicic acid, and if it is more than 10% (by weight), gel formation occurs during precipitation of silicic acid particles. It is difficult to obtain good fine silicic acid. On the other hand, the tin compound is SiO ₂ (weight) in an alkaline silicate solution.
Generally, the presence of 15 to 60% (by weight) is sufficient. That is, the tin compound is 15% (by weight) above.
If the amount is less than 60% (by weight), the desired conductivity cannot be sufficiently imparted to the resulting hydrated silicic acid, and even if the amount is more than 60% (by weight), no further improvement in the conductivity is observed. The alkali silicate used in the present invention includes, for example, sodium silicate, potassium silicate, lithium silicate, ammonium silicate, etc., and these are generally used as an aqueous solution, and in particular, an aqueous solution of sodium silicate (soda) is used industrially. The acid may be one or more selected from mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, acidic gases such as carbon dioxide gas and sulfur dioxide gas, and organic acids such as acetic acid and formic acid. Mixtures can be used. The reaction of adding an acid to the alkali silicate solution to produce a silicate sol is greatly influenced by the concentration of the alkali silicate charged, the rate of acid addition, the degree of neutralization, temperature, stirring, etc. That is, if the concentration of the alkali silicate charged is high, rapid flocculation tends to occur and it becomes difficult to control a stable sol, so it is generally preferable to maintain the SiO ₂ content at 6 g/100 ml or less. If the concentration of the alkali silicate charged is too low, it is not only uneconomical but also makes it difficult to obtain a particle size distribution of the silicic acid obtained in the subsequent reaction, so it is preferable to maintain the concentration as SiO ₂ at 2 g/100 ml or more. Furthermore, if the acid addition rate is fast, flocs are likely to be generated rapidly, so it is desirable to add the acid continuously or intermittently over a period of at least 5 minutes. The degree of neutralization is slightly alkaline, and in the case of sodium silicate, Na ₂ O
A concentration of 0.01N or more and 0.3N or less is required. That is, in the case of an acidic side where the degree of neutralization is equal to or higher than the equivalence point, rapid flocculation occurs, so it is preferable to keep the degree of neutralization on an alkaline side. Temperature is generally 70~
The temperature is preferably 100°C, and if the temperature is lower than 70°C, the viscosity of the reaction liquid increases, 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 also a preferred embodiment to control the reaction within a range in which no flocs are produced by adding a small amount of a neutral salt such as Na ₂ SO ₄ or NaCl to the reaction system. In addition, as necessary,
For example, additives such as surfactants, organic silicon compounds, and phosphorus compounds can also be used. Next, by adding an acid or an alkali silicate and an acid to the silicic acid sol solution described above, silicic acid is precipitated and stabilized by growing secondary particles of silicic acid gel. Furthermore, if necessary, it is desirable to adjust the final pH to 8 or less, preferably 4 to 7, by adding an acid, from the viewpoint of the physical properties of the resulting hydrated silicic acid or 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, dried, and crushed and classified as necessary to obtain the desired fine hydrated silicic acid. I can do it. In the present invention, fine hydrated silicic acid having good conductivity can be obtained by allowing a tin compound or an antimony compound and a tin compound to be present in the reaction system in the above-described method for producing hydrated silicic acid. The conductive hydrated silicic acid of the present invention thus obtained can be used, for example, in electrically conductive thermal paper, electrostatic recording paper, electrostatic paint,
It is extremely useful as a filler for antistatic plastics and rubber materials. Examples will be given below, but the present invention is not particularly limited thereto. In addition, the measurement method in Examples and Comparative Examples is shown. (1) Specific resistance (Ω・cm) Measured with a Bridge circuit (manufactured by Yokogawa Electric) (2) Static electricity (KV) 10g of sample was placed in a magnetic dish and placed in an electric furnace at 500℃ for 30 minutes, then the metal Stir gently with a spoon and measure the static electricity generated at this time using Statylon M (manufactured by Shishido Shokai) Example 1 703 ml of a sodium silicate solution with a SiO ₂ concentration of 25.5% and a Na ₂ O concentration of 8.57%, 2297 ml of water, and 60 ml of ethanol.
Dissolve 6.2g of antimony chloride in ml and make a volume of 5.
The liquid temperature was set at 40°C. Next, 130 ml of 22% sulfuric acid was added, the temperature was raised to 95°C, and the mixture was stirred for 5 minutes. A solution of 72 g of tin chloride (SnCl ₄ ) dissolved in 600 ml of water was then added over 90 minutes. % sulfuric acid was added to adjust the pH of the solution to 3.5. The obtained slurry solution was filtered and washed with water, and the cake (water content: 83%) was dried at 110°C and pulverized to obtain the hydrated silicic acid of the present invention. Measured values for the hydrated silicic acid are shown in Table 1. Example 2 In Example 1, after adding tin chloride, the pH of the solution
It was manufactured in the same manner except that the value was adjusted to 7.2. The results are shown in Table 1. Example 3 318 ml of sodium silicate and water as in Example 1
1854ml was charged into a reaction tank and the temperature was raised to 95°C. Next, add 6.2 g of antimony chloride (SbCl ₃ ) to 60 ml of ethanol.
After adding the dissolved liquid and adding 147 ml of 22% sulfuric acid over 28 minutes, add tin chloride to 232 ml of sodium silicate and 600 ml of water.
A solution containing 72 g of each solution was added over 90 minutes. Thereafter, the pH of the reaction solution was adjusted to 3.8 with 22% sulfuric acid. The obtained slurry solution was subjected to the same operation as in Example 1 to obtain a dry product of hydrous silicic acid. Measured values for the hydrated silicic acid are shown in Table 1. Example 4 654 ml of sodium silicate solution with SiO ₂ concentration 27.52% and Na ₂ O concentration 9.32%, water 679 ml and Na ₂ O concentration 1.8
% Na ₂ SO ₄ solution was charged into an externally heated reaction tank with an internal volume of 5, and the temperature of the solution was set at 40°C. then 22%
After adding 131 ml of sulfuric acid and stirring for 5 minutes while raising the temperature to 95°C, 72 g of tin chloride (SnCl ₄ ) was added to 600 ml of water.
After adding the solution in 90 minutes, an additional 22%
The pH of the solution was adjusted to 7.2 by adding sulfuric acid. The following products were manufactured in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 1 682 ml of sodium silicate solution with SiO ₂ concentration of 26.4% and Na ₂ O concentration of 9.3%, 1935 ml of Glauber's salt (Na ₂ O = 1.55%)
and 383 ml of water were charged into a reaction tank in the same manner as in Example 1, and the temperature was set at 40°C. Next, after adding 22% sulfuric acid, 95℃
After stirring in this state for 5 minutes, 274 ml of 22% sulfuric acid was added over 90 minutes. Thereafter, a solution of tin chloride and antimony chloride having the same concentration as used in Example 1 was added simultaneously over 60 minutes. Thus, according to Example 1, a dried product of hydrated silicic acid was obtained. Measured values for the hydrated silicic acid are shown in Table 1. Comparative Example 2 Tokusil P (manufactured by Tokuyama Soda KK) is shown as a commercially available hydrous silicic acid.

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Claims (1)

[Scope of Claims] 1. A method for producing hydrated silicic acid having electrical conductivity, characterized in that a tin compound is present in the reaction system when producing hydrated silicic acid by neutralizing an alkali silicate with an acid. 2 Claim 1 in which the tin compound is tin chloride
Manufacturing method described in section. 3. The manufacturing method according to claim 1, wherein a tin compound is added after preparing the silicic acid sol solution. 4. A method for producing hydrated silicic acid having electrical conductivity, which comprises making an antimony compound and a tin compound exist in the reaction system when producing hydrated silicic acid by neutralizing an alkali silicate with an acid. 5 After preparing a silicate sol solution by adding an acid to an alkaline silicate solution containing an antimony compound,
The manufacturing method according to claim 4, wherein a tin compound is added. 6. The manufacturing method according to claim 4, wherein the antimony compound is antimony chloride.