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Pyrogenically produced silicon dioxide powder and dispersion thereof
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A technology of silica and dispersion, used in silica, silica, inorganic chemistry, etc.
Active Publication Date: 2011-06-15
EVONIK OPERATIONS GMBH
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It has been found that for silica powders prepared by the prior art, even if they are produced by the same type of reaction and have the same or similar general characterization parameters (such as BET surface area), it takes a long time to introduce them into a liquid medium. long time
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Embodiment 1
[0068] Example 1 Preparation of silica powder
[0069] 95 kg / h of silicon tetrachloride and 5 kg / h of silicon trichloride (TCS) are evaporated and transferred to the mixing chamber of the burner with nitrogen. At the same time, the 34Nm 3 / h (1.5kmol / h) of hydrogen and 70Nm 3 / h (3.1 kmol / h) of primary air was introduced into the mixing chamber. The temperature of the mixture was 90°C. It is ignited and burns into the reaction chamber as a flame. In addition, the 24Nm 3 / h (1.1 kmol / h) Secondary air surrounding the flame was introduced into the reaction chamber.
[0070] By using a partial vacuum, the reaction gases and the silica formed are drawn into a cooling system, where they are cooled to between 100-160°C. Solids are separated from the off-gas using filters or cyclones before steaming at 555°C.
Embodiment 2-11
[0071] Example 2-11 proceed in the same way
[0072] Table 2 gives the feed materials and their amounts in Examples 1-11.
[0073] Table 3 shows the calculated values of reaction enthalpy, heat capacity and adiabatic flame temperature.
[0074] Table 4 shows the comparison between the prepared silica and two commercially available fumed silica powders ( Examples 12 and 13 ) analysis data.
[0075] Examples 1-5 produced powders according to the invention.
[0076] Examples 6-10 are comparative examples.
[0077] In Example 2, three silicon components were used.
[0078] High and low proportions of the first silicon component, silicon tetrachloride, were used in Examples 3 and 4, respectively.
[0079] In Example 5 a high ratio of secondary air to primary air is established within the claimed range.
[0080] In Examples 6 and 7, a setpoint was chosen that resulted in the adiabatic flame temperature being outside the desired range.
[0093] 36kg of demineralized water is placed in a 601 stainless steel batching container. 6.4 kg of the silica powder obtained from Example 1 was introduced into it under shear using the suction tube of Ystral Conti-TDS 3, and then sheared at 3000 rpm for 15 min after completion of the introduction step.
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Abstract
The invention relates to a pyrogenically produced silicon dioxide powder in the form of aggregates of primary particles having a BET surface area of 90+-15 m<2> / g, wherein the aggregates display an average surface area of 10000 to 20000 nm<2>, an average equivalent circle diameter (ECD) of 90 to 130 nm and an average circumference of 1000 to 1400 nm. The silicon dioxide powder is produced by a pyrogenic process in which silicontetrachloride and a second silicon component (comprising H3SiCl, H2SiCl2, HSiCl3, CH3SiCl3, (CH3)2SiCl2, (CH3)3SiCl and / or (n-C3H7)SiCl3) are mixed with primary air and a combustion gas and burnt into a reaction chamber, secondary air also being introduced into the reaction chamber, and the feed materials being chosen such that an adiabatic flame temperature of 1810 to 1890 DEG C is obtained. The invention also relates to dispersion containing the pyrogenically produced silicon dioxidepowder.
Description
technical field [0001] The invention relates to a silicon dioxide powder prepared by pyrolysis, a preparation method and application thereof. The invention also relates to dispersions comprising said pyrogenically produced silica powder. Background technique [0002] The flamehydrolysis process for the preparation of silica has long been known and has been used for large-scale industrial production. In this process, vaporized or gaseous hydrolyzable silicon halides are mixed with a flame formed by burning a hydrogen-containing fuel and an oxygen-containing gas to produce water. The combustion flame provides water for the hydrolysis of silicon halides and sufficient heat for the hydrolysis reaction. The silica powder entrained in the resulting reaction gas is subjected to conventional cooling and solid separation. Silicontetrachloride is usually used. However, it is also known to use dichlorosilanes, trichlorosilanes. Also occurs if carbon-containing feed materials are...
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