Abstract: There provides an organosol of silica, wherein alkaline earth metal ions are bonded on surface of colloidal silica particles. The silica sol has a low solid acidity of silica, thus, in case where it is used in a mixture with a resin and the like, it can inhibit change of properties or decomposition, etc. of the resin, compared with silica sols that no alkaline earth metal is bonded to the surface of the particles. Further, the silica sol can be used as hard coat films for forming the surface of resin molded forms such as lenses, bottles, films or plates, or micro-fillers for thin films, resin internal agents, and the like.

Abstract: A process for producing a hydrophobic silica powder, comprises the steps for hydrophobic treatment of: adding to a silica sol in mixed solvent having a silica concentration of 5 to 50 mass % obtained by mixing an aqueous silica sol containing hydrophilic colloidal silica having a specific surface area of 5.5 to 550 m2/g with a hydrophilic organic solvent in a mass ratio of 0.12 to 2.5 based on water in the aqueous silica sol, a disilazane compound of formula (1) (R13Si)2NH ??(1) wherein each R1 is C1-6alkyl group or phenyl group that is selected independently of one another, in an amount of 0.1 to 20 mmol per surface area 100 m2 of the hydrophilic colloidal silica, to obtain a mixture of the silica sol in mixed solvent and the disilazane compound; and heating the mixture at a temperature of 50 to 100° C. for aging it to obtain a slurry dispersion of hydrophobic treated colloidal silica. The process provides a hydrophobic silica powder through a simple hydrophobic treatment step.

Abstract: A process for producing a hydrophobic silica powder, comprises the steps for hydrophobic treatment of: adding to an aqueous silica sol containing hydrophilic colloidal silica having a specific surface area of 5.5 to 550 m2/g, a disilazane compound represented by formula (1) (R13Si)2NH??(1) wherein each R1 is C1-6alkyl group or phenyl group that is selected independently of one another, in an amount of 0.1 to 10 mmol per surface area 100 m2 of the hydrophilic colloidal silica, to obtain a first mixture of the aqueous silica sol and the disilazane compound; and heating the mixture at a temperature of 50 to 100° C. for aging it to obtain a slurry as dispersion of hydrophobic treated colloidal silica. The process provides a hydrophobic silica powder through a simple hydrophobic treatment step.

Abstract: A process for producing an inorganic oxide organosol comprises the steps (A) and (B) of: (A) adding silicon alkoxide having two or more alkoxy groups bonded to a silicon atom or having one or more hydroxy groups bonded to a silicon atom and one or more alkoxy groups bonded to a silicon atom to a hydrophilic inorganic oxide sol containing a hydrophilic solvent having a boiling point (1 atm) of 100° C. or less in an amount of 25 to 100% by weight in a dispersion medium to treat surface of the inorganic oxide particles in the sol; and (B) replacing the dispersion medium of the surface treated inorganic oxide sol obtained in step (A) with a non-alcoholic organic solvent in the presence of a primary alcohol having 3 to 12 carbon atoms. The process gives an inorganic oxide organosol that has a good dispersibility and a low viscosity, is excellent in transparency, and shows a good compatibility with resin solutions.

Abstract: A process of producing a hydrophobic organosilica sol which comprises aging a reaction mixture at 0 to 100.degree. C. in the state that an alkali present in the reaction mixture is removed or is neutralized with an acid in an equivalent amount or more, thereby forming a silylation-treated silica sol having a hydrophobic colloidal silica dispersed therein, the reaction mixture comprising: (a) a hydrophilic colloidal silica having a specific surface area of 5.5 to 550 m.sup.2 /g in SiO.sub.2 concentration of 5 to 55% by weight, (b) a silylating agent of a disiloxane compound and/or monoalkoxysilane compound in a millimolar ratio of 0.03 to 2 in terms of Si atom per 100 m.sup.2 of a surface of the hydrophilic colloidal silica, and (c) a medium, as a residue thereof, comprising a mixed solvent comprising a hydrophobic organic solvent having a solubility of water of 0.1 to 12% by weight and an alcohol having 1 to 3 carbon atoms in a weight ratio of 0.