Patent ID: 6051672
Filing Date: 2000-04-18
Classification: B82Y,C01B,C01P,C09C

Abstract:
A method for making a hydrophobic non-aggregated colloidal silica comprising reacting an aqueous suspension of a hydrophilic non-aggregated colloidal silica having an average particle diameter greater than about 4 nm with a silicon compound selected from the group consisting of organosilanes described by formulaR.sup.1.sub.a H.sub.b SiX.sub.4-a-band organosiloxanes described by formulaR.sup.1.sub.n SiO.sub.(4-n).sub./2,where each R.sup.1 is independently selected from the group consisting of hydrocarbon radicals comprising 1 to about 12 carbon atoms and organofunctional hydrocarbon radicals comprising 1 to about 12 carbon atoms, each X is independently selected from the group consisting of halogen and alkoxy radicals comprising 1 to about 12 carbon atoms, a=0, 1, 2, or 3, b=0 or 1, a+b=1, 2, or 3 with the proviso that when b=1 then a+b=2 or 3, and n is an integer from 2 to 3 inclusive at a pH less than about pH 4 in the presence of a sufficient quantity of a water-miscible organic solvent to facilitate contact of the hydrophilic non-aggregated colloidal silica with the silicon compound at a temperature within a range of about 20.degree. C. to 250.degree. C. for a time period sufficient to form a hydrophobic non-aggregated colloidal silica.