Patent ID: 7989506

Claim:
A method for dispersing and wetting fumed silica powder, comprising fumed silica particles, in an aqueous medium comprising the steps of: (a) providing a vessel equipped with a cover lid and a radial flow mixer, one or more baffles, means for cooling the vessel, an outlet for removing a final dispersion, and an inlet for the fumed silica powder, wherein the inlet is located on the vessel bottom below the radial flow mixer and radially offset from the axis of the radial flow mixer, wherein the inlet for the fumed silica powder is connected to, or formed from, a flush bottom valve; (b) charging the vessel with an aqueous liquid comprising at least 50 percent by weight water; (c) subjecting the aqueous liquid in the vessel to vacuum and high-shear radial flow mixing; (d) drawing the fumed silica powder into the vessel through the inlet, which inlet is below the surface of the aqueous liquid, while maintaining the temperature of the dispersion below 35° C., wherein the fumed silica powder is added until at least 30% solids are present; (e) maintaining the mixing for a period sufficient to break up non-colloidal aggregates of fumed silica powder; (f) reducing solids concentration in the vessel by at least 5 percent solids; and (g) filtering the dispersion to reduce presence of impurities and agglomerates; wherein the flush bottom valve is a ball valve.