Process For Producing Scaly Silica Particles
A technology of silicon dioxide and manufacturing method, applied in the direction of silicon dioxide, silicon oxide, etc., can solve the problems of decreased strength and decreased compactness of silicon dioxide coating film, etc.
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Embodiment 1
[0122] [Manufacture of silica dispersion]
[0123] Starting materials Silicon hydrogels were prepared as follows using sodium silicate as the alkali metal source. SiO 2 / Na 2 O=3.0 (molar ratio), SiO 2 2000 ml / min of sodium silicate aqueous solution with a concentration of 21.0% by mass and sulfuric acid aqueous solution with a sulfuric acid concentration of 20.0% by mass are introduced from an independent inlet into a container with a release port and mixed instantly, and the pH of the solution released into the air from the release port is 7.5 Adjust the flow ratio of the two solutions under the condition of ~8.0, and continuously release the mixed silica sol solution into the air from the release port. The released solution was in the form of a spherical droplet in the air, drawing a parabola and gelling in the air while staying in the air for about 1 second. A ripening tank covered with water is placed in advance at the place where it falls, and it is allowed to fall i...
Embodiment 2
[0144] In the same manner as in Example 1 above, a silica dispersion was prepared, followed by acid treatment and cleaning.
[0145] [alkali treatment]
[0146] While stirring 389.6 g of the washed silica dispersion with a stirrer, 3.4 g of potassium hydroxide (1 mmol / g-silica) and 810.4 g of water were added. The pH after the addition was 9.4. This state was maintained, and the stirring was continued at room temperature for 19.5 hours. In addition, the average particle diameter of the silica particles after alkali treatment was 7.82 μm.
[0147] [Wet crushing]
[0148] The silica dispersion after the alkali treatment was treated with a wet medium agitation mill ("Ultra Apex Mill UAM-015" manufactured by Kotobuki Kogyo Co., Ltd., container capacity 170 ml, φ0.05 mm zirconia beads 80%) The circulation treatment was carried out under the conditions of disk peripheral velocity 6 m / sec and residence time 60 minutes to crush and disperse the silica particles. The pH of the cru...
Embodiment 3
[0157] [Manufacture of silica dispersion]
[0158] A silicone hydrogel was produced in the same manner as in Example 1 above.
[0159] The above-mentioned silicone hydrogel particles were roughly pulverized with a twin-roll crusher to an average particle diameter of 2.5 mm, and used for subsequent hydrothermal treatment.
[0160] According to the total SiO in the system 2 / Na 2 O molar ratio of 12.0 conditions to the capacity of 17m 3 Add the above-mentioned silicon hydrogel (SiO 2 18 mass %) 7249kg and sodium silicate aqueous solution (SiO 2 29.00% by mass, Na 2 O9.42% by mass, SiO 2 / Na 2 O=3.18 (molar ratio)) 1500kg, add water 1560kg to it, add saturation pressure 17kgf / cm while stirring at 10rpm 2 4682kg of high-pressure steam and heated to 185 ° C, and then 5 hours of hydrothermal treatment. The total silica concentration in the system is SiO 2 It is calculated as 12.5% by mass.
[0161] The synthesized silicon dioxide dispersion is filtered and washed, and t...
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