Oil-in-water type emulsion and method for producing oil-in-water type emulsion

A method for producing an oil-in-water emulsion, comprising the steps of:

• a) preparing a fumed silica at a secondary aggregate level by mixing a hydrophobic-rich silica raw material in which surface silanol groups have been subjected to a hydrophobic treatment with a hydrophilic-rich silica raw material in which surface silanol groups remain, to form a composite mixture;
• b) producing an aqueous dispersion by adding the composite mixture obtained from step a) to water and shearing at a shearing speed which allows rearrangement of hydrophilic and hydrophobic lower order aggregates, the resulting aqueous dispersion containing fumed silica particles in which the lower order aggregates are aggregated with each other to form higher order aggregates aggregated by non-chemical bonds, thereby forming a network-like surrounding structure including a space inside the network-like surrounding structure;
• and
• c) forming an emulsion by adding an oil to the aqueous dispersion produced in step b),
• the oil-in-water type emulsion including a composite particle in which the oil is included inside the network-like surrounding structure formed by the fumed silica particles at a secondary aggregate level.