Production of silica particles

Details Production of silica particles Production of silica particles

1999-12-14

2002-12-17

Griffin, Steven P. (Department: 1754)

Chemistry of inorganic compounds

Silicon or compound thereof

Oxygen containing

Reexamination Certificate

active

06495114

ABSTRACT:

The present invention relates to a process for producing ultra fine silica particles of sub micron size, i.e. silica particles having an average diameter of less than 1 micron. Such particles are sometimes referred to in the art as “colloidal” silica particles.
Ultra fine sub micron silica particles are known in the art. For example, a fine silica particle material wherein the silica particles are spherical particles having an average diameter between 7 and 40 nanometers and produced by the hydrolysis of a volatile silane compound in an oxygen-hydrogen gas flame is available in commerce under the trade name
AEROSIL
from the company Degussa AG of Frankfurt Am Main, Germany. In addition, the production of fine silica particles is disclosed in “The Chemistry of Silica”, by Ralph Kìsla, 1979, John Wiley & Sons, Inc. That document discloses on page 25 three ways for producing anhydrous amorphous silica particles at high temperature, these being vaporising silicon dioxide in an arc or plasma jet and condensing it in a stream of dry inert gas; oxidising silicon monoxide in the vapour phase with air and condensing the silicon dioxide; and oxidising silicon compounds in the vapour state, such as SiH
4
, SiCl
4
or HSiCl
3
with dry hydrogen or in a hydrocarbon flame.
The present invention aims to provide improved processes for the production of ultra fine sub micron silica particles.
Accordingly, the present invention provides a process for producing ultra fine silica particles, the process comprising directing a plasma jet onto a silicon-containing compound thereby to form silica vapour and condensing the silica vapour on a collection surface.


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Balabanova E G et al: “Model predictions for the characteristics of plasma-produced ultrafine silica powders” High Tempatures -High Pressures, 1997, Pion, UK, vol. 29, No. 6, pp. 711-716, XP000856965 ISSN: 0018-1544′ pp. 711-712, 713, 714, 715, 716 no month.
Chemical Abstracts, vol. 83, No. 22, Dec. 1, 1975 (12-01-1975), Columbus, Ohio, US; abstract No. 183998, Videnov N. B. et al.: “Production of highly dispersed silicon dioxide in a plasma jet” XP002126122 *abstract* & Khim. Ind., vol. 47, No. 6, 1975, pp. 243-245.
Manabu Kato et al.: “Synthesis of coesite from ultra fine particles” Japanese Journal of Applied Physics., vol. 14, No. 2, Feb. 1975 (02-1975), pp. 181-183 pages 181, 182 “2 Starting Materials”.
P. K. Mishra et al.: “Fine Silica Power Preparation by Use of a Transferred Art Thermal Plasma Reactor” Materials Letters, vol. 23, No. 1,2,3, 1995, pp. 153-156, North Holland Publishing Company Amsterdam, NL ISSN: 0167-577X *the whole document*.

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