Patent ID: 7700669

Claim:
A pyrogenic silica powder modified with groups of the general formula (I) R a SiR 1 b (O—Si≡) c (I) where —Si≡ is a silicon atom of the silica, a is 1, 2 or 3, b is 0, 1 or 2, and c is 1, 2 or 3, and a+b+c=4, and R is a monovalent, optionally mono- or polyunsaturated, optionally branched hydrocarbon radical having 1 to 24 carbon atoms, R 1 is a monovalent, optionally mono- or polyunsaturated, optionally branched hydrocarbon radical having 1 to 20 carbon atoms, it being necessary for at least one of the radicals, R or R 1 , present to have more than 3 carbon atoms per molecule, the silica prepared by silylating with a silane having at least one hydrocarbon group with more than 3 carbon atoms, the silylating taking place in a temperature gradient wherein the temperature reaches a temperature in the range of 120° C. to 350° C. and, wherein in a dispersion comprising the silica and a liquid containing strongly basic groups, the silica permitting a decrease in the shear viscosity η after a storage time of 1 week at room temperature (25° C.) to not more than 50% of the initial viscosity of the dispersion.