Patent ID: 8344033

Claim:
A process for the preparation of a product emulsion comprising an oil phase (A) and an aqueous phase (B) comprising preparing a highly concentrated finely divided dispersion of pyrogenic silica in a portion of a liquid which forms a homogeneous phase in the emulsion in a first step to form a highly viscous dispersion; in a second step, adding the total amount of a disperse phase to the highly concentrated finely divided dispersion of pyrogenic silica prepared in the first step, the volume of dispersion used being such that the total amount of pyrogenic silica required in the product emulsion is present; and metering in the remaining portion of the homogeneous phase in a third step, wherein pyrogenic silica is present at an oil-water interface of the oil phase (A) and the aqueous phase (B), the pyrogenic silica being partly silylated such that the content of non-silylated surface silanol groups on the silica surface is from not more than 95% to not less than 5% of the silanol groups of the starting silica, or from 1.7 to 0.1 SiOH groups per nm 2 of silica surface, the dispersion fraction of the surface energy gamma-s-D being from 30 to 80 mJ/m 2 and the specific BET surface area being from 30 to 500 m 2 /g, and wherein the emulsions have a mean particle size of the dispersed phase of from 0.5 μm to 500 μm and a relative viscosity η r in the range of from 1 to 10 6 , the relative viscosity being defined as the quotient η/η 0 where η is the measured viscosity of the emulsion at 25° C. and a shear rate D=10 s −1 , and η 0 is the viscosity of the pure homogeneous phase, and wherein the relative viscosity of the emulsion obeys the formula η rel =(1 −Φ/ 0.74) −([η]·0.74) , Φ being the volume of the dispersed phase and [η] being a form factor from 2.5 to 10.