US 2010/0059704 A1 · FUMED SILICA OF CONTROLLED AGGREGATE SIZE AND PROCESSES FOR MANUFACTURING THE SAME

Abstract

The invention provides fumed silica comprising aggregates that have an aggregate size and a surface area that satisfy particular formulas relating aggregate size to surface area, as well as aggregates that exhibit particular viscosity, power law exponent index, and/or elastic modulus characteristics when dispersed in liquid media. The invention also provides processes of preparing such fumed silica by combining a silica precursor with a stream of combustible gas, combusting the stream, and producing a stream of combusted gas and fumed silica particles, wherein dopants are introduced, the time/temperature profile, or history, of the stream of combusted gas and fumed silica particles is adjusted to allow for post-quench aggregate growth, and/or additional silica precursor is introduced into the stream of combusted gas.

Claims38

Dependent claims

Fumed silica comprising aggregates of primary particles, wherein the fumed silica has an aggregate size D as measured by PCS, in units of nm, and a surface area SA as measured by BET, in units of m2/g, satisfying the formula:

D≧151+(5400/SA)+0.00054(SA−349)2.

A process for producing fumed silica, which process comprises:

(a) providing a stream of a feedstock comprising a silica precursor,
(b) providing a stream of a combustible gas,
(c) forming a stream of combusted gas with fumed silica particles suspended therein in a reactor, wherein the fumed silica particles comprise aggregates of primary particles, and wherein the aggregates are of a first aggregate size, by (c1) mixing the stream of the feedstock with the stream of the combustible gas to form a stream of combustible gas with the silica precursor, and then combusting the stream of combustible gas with the silica precursor to form the stream of combusted gas with fumed silica particles suspended therein, (c2) combusting the stream of combustible gas to form a stream of combusted gas and then mixing the stream of the feedstock with the stream of the combusted gas to form a stream of combusted gas with the silica precursor suspended therein, which then forms fumed silica particles, or (c3) carrying out a combination of the foregoing items (c1) and (c2),
(d) allowing contact among the fumed silica particles having the first aggregate size in the stream of combusted gas and either (d1) contacting the fumed silica particles having the first aggregate size with one or more dopants to modify surfaces thereof, (d2) controlling the temperature-time profile of the fumed silica particles having the first aggregate size to allow post-quench aggregate growth, (d3) introducing additional feedstock into the stream of combusted gas with the fumed silica particles having the first aggregate size suspended therein, or (d4) carrying out a combination of any of the foregoing items (d1), (d2), and (d3), thereby forming a stream of combusted gas with fumed silica particles suspended therein, wherein the fumed silica particles comprise aggregates of a second aggregate size larger than the first aggregate size, and
(e) recovering the fumed silica particles having the second aggregate size from the stream of combusted gas, wherein the recovered fumed silica particles have an aggregate size D as measured by PCS, in units of nm, and a surface area SA as measured by BET, in units of m2/g, satisfying the formula:
D≧151+(5400/SA)+0.00054(SA−349)2.

3 more elements

Dependencies are inferred from the claim text.

Fumed silica of controlled aggregate size and processes for manufacturing the same

Life of this patent

Fumed silica of controlled aggregate size and processes for manufacturing the same

Life of this patent

Abstract

Claims38