Ultraviolet-shielding agent, method for the preparation thereof and cosmetic composition compounded therewith
AssigneeNippon Inorganic Colour & Chemical Co., Ltd.
InventorsMasao Suzuki, Sakae Yoshida, Shigenobu Okamiya
Life of this patent
Estimating the term…
Abstract
Disclosed is a novel ultraviolet-shielding agent in a powder form consisting of particles of an inorganic material having a specified refractive index and a flaky particle configuration, such as mica, talc, sericite and the like, compositely coated with a water-insoluble cerium compound and amorphous silica each in a specified coating amount. A method for the preparation of such an ultraviolet-shielding agent is disclosed. By virtue of the excellent ultraviolet-shielding effect along with good translucency as well as stability and safety against human skin, it is useful as an ultraviolet-shielding ingredient in cosmetic compositions.
Claims7
A method for the preparation of an inorganic ultraviolet-shielding agent in a powdery form which comprises the steps of:
- (A) dispersing particles of an inorganic material having a refractive index in the range from 1.45 to 1.65 and a flaky particle configuration selected from the group consisting of mica, talc and sericite in an aqueous medium to prepare an aqueous dispersion;
- (B) adding, to the aqueous dispersion prepared in step (A) above, an aqueous solution of a water-soluble cerium compound;
- (C) adding a precipitant of the cerium compound to the aqueous dispersion of the inorganic particles containing the water-soluble cerium compound so as to deposit a water-insoluble cerium compound selected from the group consisting of cerium oxide, cerium hydroxide, cerium phosphate, cerium polyphosphate, cerium carbonate and cerium oxalate on the surface of the particles;
- (D) adding, to the aqueous dispersion of the inorganic particles having the water-insoluble cerium compound deposited on the surface thereof prepared in step (C), an aqueous solution of a water-soluble or water-dispersible silicate compound;
- (E) adjusting the pH of the aqueous dispersion to 9 to 11 so as to deposit amorphous silica on the surface of the particles to form a composite coating layer consisting of the water-insoluble cerium compound and the amorphous silica;
- (F) separating the particles from the aqueous medium of the dispersion followed by drying;
- and
- (G) calcining the dried particles at a temperature in the range from 200.degree. to 1000.degree. C.
Dependencies are inferred from the claim text.