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.
Claims17
A method for preparing substantially spherical particles consisting essentially of SiO.sub.2 comprising 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.
A method of lowering the porosity of particles consisting essentially of SiO.sub.2 prepared by hydrolytic polycondensation of a tetraalkoxysilane in an aqueous/alcoholic ammoniacal hydrolysis mixture to form a sol of said particles, comprising continuously adding to said sol 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.
A method for preparing substantially spherical particles consisting essentially of SiO.sub.2 comprising 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, an organotrialkoxysilane or a combination thereof, 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.
Dependencies are inferred from the claim text.