Process of producing hydrophobic organosilica sol

A process of producing a hydrophobic organosilica sol which comprises the steps of:

• (A) 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 equivalent amount or more of an acid, to form a silylation-treated silica sol having a hydrophobic colloidal silica dispersed therein, said reaction mixture comprising:
• 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,
• a silylating agent represented by the following formulae (I) and/or (II) in a millimolar ratio of 0.05 to 2 in terms of Si atom per 100 m.sup.2 of a surface area of the hydrophilic colloidal silica, ##STR7## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 each independently represent one substituent selected from the group consisting of alkyl groups having 1 to 20 carbon atoms and phenyl groups, which may optionally be substituted;
• ##STR8## wherein R.sup.7, R.sup.8 and R.sup.9 each independently represent one substituent selected from the group consisting of alkyl groups having 1 to 20 carbon atoms and phenyl groups, which may be optionally substituted, and Q represents one substituent selected from the group consisting of alkyl groups having 1 to 3 carbon atoms, which may be substituted, and
• a medium 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 0.05 to 20 to the hydrophobic organic solvent, and water in an amount of 15% by weight or less based on the weight of the medium, and
• (B) distilling the silylation-treated silica sol produced in step (A) above to produce the hydrophobic organosilica sol wherein a medium of the silylation-treated silica sol is substituted with the hydrophobic organic solvent.

A process of producing a hydrophobic organosilica sol which comprises the steps of:

• (A) aging a first 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 equivalent amount or more of an acid, to produce a silylation-pretreated silica sol having a hydrophobic colloidal silica dispersed therein, said reaction mixture comprising:
• 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,
• a silylating agent represented by the following formulae (I) and/or (II) in a millimolar ratio of 0.03 to 1.5 in terms of Si atom per 100 m.sup.2 of a surface area of the hydrophilic colloidal silica, ##STR9## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 each independently represent one substituent selected from the group consisting of alkyl groups having 1 to 20 carbon atoms and phenyl groups, which may optionally be substituted, ##STR10## wherein R.sup.7, R.sup.8, and R.sup.9 each independently represent one substituent selected from the group consisting of alkyl groups having 1 to 20 carbon atoms and phenyl groups, which may be optionally substituted, and Q represents one substituent selected from the group consisting of alkyl groups having 1 to 3 carbon atoms, which may be substituted, and
• 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 0.05 to 20 to the hydrophobic organic solvent, and water in an amount of 15% by weight or less based on the weight of the medium,
• (B) distilling the silylation-pretreated silica sol produced in step (A) above to produce an alcohol-containing hydrophobic organosilica sol wherein a medium of the silylation-pretreated silica sol is substituted with the hydrophobic organic solvent until the alcohol having 1 to 3 carbon atoms is a weight ratio of 0.05 to 5 to the hydrophobic organic solvent having a solubility of water of 0.1 to 12% weight,
• (C) aging a second reaction mixture at 0 to 100.degree. C. to produce a silylation-treated silica-sol having the hydrophobic colloidal silica dispersed therein, said reaction mixture comprising:
• the alcohol-containing hydrophobic organosilica sol produced in step (B),
• the silylating agent represented by the above formulae (I) and/or (II) in the total addition amount in step (A) and step (C) of a millimolar ratio of 0.05 to 2 in terms of Si atom per 100 m.sup.2 of a surface area of a hydrophilic colloidal silica which is a raw material of the hydrophobic colloidal silica in the alcohol-containing hydrophobic organosilica sol, and
• a medium, as a residue thereof, comprising a mixed solvent comprising a hydrophobic organic solvent having a solubility in water of 0.1 to 12% by weight and an alcohol having 1 to 3 carbon atoms in a weight ratio of 0.05 to 20 to the hydrophobic organic solvent, and water in an amount of 15% by weight or less based on the weight of the medium,
• (D) distilling the silylation-treated silica sol produced in step (C) above to produce the hydrophobic organosilica sol wherein a medium of the silylation-treated silica sol is substituted with the hydrophobic organic solvent.