Porous Silica-Based Particles Having Smooth Surface, Method for Production Thereof and Cosmetic Comprising Such Particles
AssigneeJGC Catalysts and Chemicals Ltd.
InventorsNaoyuki Enomoto, Yasutaka Miyoshi, Tsuneo Kawashima, Takumi Miyazaki
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Abstract
Disclosed are porous silica-based particles having high surface smoothness, a method for producing the porous silica-based particles, and a cosmetic comprising the porous silica-based particles. The porous silica-based particles have an average particle diameter of 0.5 to 30 μm and have a surface smoothness of a level to such an extent that, when the entire surface of the particle is observed from a photograph thereof taken by a scanning electron microscope (SEM) with a magnifying power of 10,000, a foreign matter attached to the surface thereof can be hardly seen.
Claims17
Porous silica-based particles having an average particle diameter of 0.5 to 30 μm and having a surface smoothness of a level to such an extent that, when the entire surface of the particle is observed from a photograph thereof taken by a scanning electron microscope (SEM) with a magnifying power of 10,000, a foreign matter attached to the surface thereof can be hardly seen.
A method for producing porous silica-based particles having an average particle diameter of 0.5 to 30 μm and having a surface smoothness of a level to such an extent that, when the entire surface of the particle is observed from a photograph thereof taken by a scanning electron microscope (SEM) with a magnifying power of 10,000, a foreign matter attached to the surface thereof can be hardly seen, which comprises the steps of:
- (a) spray-drying a dispersion of fine silica-based particles, or a mixture of the above dispersion of the fine silica-based particles and an aqueous solution of silicic acid with use of a spray dryer, to obtain a dried powder of porous silica-based particles having diameters ranging primarily from 0.1 to 50 μm;
- (b) putting the dried powder of the porous silica-based particles obtained in the step (a) into water and then stirring a slurry of the mixture under pH conditions on which the zeta potential of the porous silica-based particles contained in the water comes to in a range of −15 to −70 mV, to obtain a dispersion of porous silica-based particles with a foreign matter attached to the surface thereof having been removed therefrom;
- (c) subjecting the dispersion obtained in the step (b) to a wet classification device at which a supernatant containing at least porous silica-based particles having diameters of less than 0.5 μm is separated and removed, to obtain a dispersion containing porous silica-based particles having diameters ranging primarily from 0.5 to 50 μM;
- (d) subjecting the dispersion obtained in the step (c) to a wet classification device at which a sediment or precipitates containing at least porous silica-based particles having diameters of more than 30 μm is separated and removed, to obtain a dispersion containing porous silica-based particles having diameters ranging primarily from 0.5 to 30 μm;
- (e) filtering the dispersion obtained in the step (d) to separate solid materials contained therein, to obtain a cake-like substance of porous silica-based particles;
- and
- (f) drying the cake-like substance obtained in the step (e) and then crushing or breaking up a group of thus obtained particles, to obtain a dried powder of porous silica-based particles having an average particle diameter of 0.5 to 30 μm.
Dependencies are inferred from the claim text.