US Patent 8202502 Method of preparing hydrophobic silica

The invention provides hydrophobic surface-treated silica particles having (1) a ratio T2:T3 of about 0.4 or more, wherein T2 is the intensity of a peak having a chemical shift in the CP/MAS 29Si NMR spectrum centered within the range of −56 ppm to −59 ppm, and wherein T3 is the intensity of a peak having a chemical shift in the CP/MAS 29Si NMR spectrum centered within the range of −65 ppm to −69 ppm, and (2) a ratio (T2+T3)/(T2+T3+M) of greater than about 0.05, wherein M is the intensity of a peak having a chemical shift in the CP/MAS 29Si NMR spectrum centered within the range of +7 ppm to +18 ppm. The invention also provides a method of preparing hydrophobic surface-treated silica particles.