Spherical SIO.sub.2 particles
AssigneeMerck Patent GmbH
InventorsKlaus Unger, Herbert Giesche, Joachim Kinkel
Life of this patent
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Abstract
Highly monodispersed nonporous spherical SiO.sub.2 particles are prepared having mean particle diameters between 0.05 and 10 .mu.m with a standard deviation of not more than 5% and a method for the preparation of such particles. The particles can be produced by a two step process wherein first a sol of primary particles is prepared by hydrolytic polycondensation of tetraalkoxysilanes in an aqueous/alcoholic ammoniacal medium. The SiO.sub.2 particles are then converted to the desired particle size by a continuous measured addition of tetraalkoxysilane or organotrialkoxysilane controlled by the extent of the reaction. The SiO.sub.2 particles produced by this process are particularly useful as sorption material in chromatography.
Claims4
Substantially spherical SiO.sub.2 particles having a mean particle diameter of between 0.05 and 10 .mu.m with a standard deviation of not more than 5%, said particles being substantially nonporous, and said particles having a BET surface area of 1.1-64 m.sup.2 /g.
Substantially spherical SiO.sub.2 particles having a mean particle diameter of between 0.05 and 10 .mu.m, with a standard deviation of not more than 5%, said particles being substantially nonporous and having a BET surface area of 1.1-64 m.sup.2 /g, wherein said particles are prepared by the process of continuously adding to a sol of primary particles formed by hydrolytic polycondensation of a tetraalkoxysilane in an aqueous/alcoholic ammoniacal hydrolysis mixture, an amount of a tetraalkoxysilane sufficient to lower the porosity of the particles in the sol, said continuous addition being effected at a rate whereby substantially no additional particles are formed and wherein the amount of silane added to the sol is controlled to directly control a resulting increase in particle size.
Dependencies are inferred from the claim text.