Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Patent
1999-07-06
2000-10-17
Dodson, Shelley A.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
106425, 106426, 106429, 423622, 424 59, 424489, 424642, A61K 700, A61K 742, A61K 914, C04B 1400, C01G 902
Patent
active
061327433
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a zinc oxide powder having an excellent feel, sebum resistance and protection against ultraviolet rays in which a photocatalytic activity is suppressed by coating powdery zinc oxide with silicon oxide. The invention also relates to a cosmetic compounded preparation thereof.
More specifically, the present invention relates to a zinc oxide powder having an excellent feel, sebum resistance and protection against ultraviolet rays in which a photocatalytic activity is suppressed through the formation of silicon oxide on the surface of powdery zinc oxide by surface-coating the powdery zinc oxide with at least one silicone compound such as an organo polysiloxane and a silicone resin, and firing the resulting powder at a high temperature. The invention also relates to a cosmetic compounded preparation thereof.
BACKGROUND ART
Zinc oxide powder has been formerly frequently used in cosmetic preparations, etc. as an extender pigment or for cutting light in the UV-A region. However, since the zinc oxide powder absorbs the ultraviolet light by cleaving zinc-oxide bonds, it has a problem in that the amount of radicals generated is large among powders used in the cosmetics. For this reason, it is troublesome in compounding zinc oxide powder that the compounding amount of the zinc oxide powder and other compounded ingredients coexistent with the powder must be severely selected due to the photocatalytic activity of the zinc oxide powder. In order to suppress the photocatalytic activity of the zinc oxide powder, its surface needs to be coated with a material having a low activity, and particularly is preferably coated with an inorganic oxide. For example, there are conventional inorganic oxide-coating methods as follows. 1 As proposed in JP-A-3 183,620, etc., silicon oxide or the like is precipitated and coated upon the surface of the zinc oxide fine powder by controlling the pH in a wet state so that the solid acidic catalytic activity of the zinc oxide fine powder maybe suppressed and the coefficient of dynamic friction may be reduced. 2 As proposed in JP-A 63- 139,015, particularly in order to reduce the aggregation of a powder, a vapor of a cyclic silicone compound, or that of a straight-chain silicone compound having a low molecular weight is brought into contact with active sites of the powder, the silicone compound is polymerized by the active sites of the powder, and then the resulting polymer is fired. 3 As proposed in JP-A 8-59,238, in order to suppress the photocatalytic activity of the zinc oxide powder and improve its dispersibility, the surface of the zinc oxide powder is treated with an aluminum chelate compound and a silane compound, and the thus treated zinc oxide is coated with aluminum oxide and silicon oxide after being fired at 500.degree. C. 4 As proposed in JP-A 6-80,421, in order to obtain scaly zinc oxide flake powder having an excellent ultraviolet light shielding effect and mechanical strength, the scaly zinc oxide is precipitated in a wet state under coexistence with aluminum sulfate or the like, and then the resulting precipitant is fired at 850 to about 1,000.degree. C.
In the above methods 1 and 4, zinc oxide is dissolved in a weak acid or a weak alkali because zinc oxide is an amphoteric substance, so that zinc ions are re-precipitated upon the surface of the powder during the controlling of the pH even after a treatment. Consequently, there are problems in that the photocatalytic activity cannot be sufficiently suppressed or the powder is strongly aggregated. On the other hand, according to the above method 2, the silicon compound must be once fed, in the form of a vapor, to the powder, so that the method is troublesome and time-consuming, the amount of the treating silicone compound depends upon the catalytic activity of the powder to disable the free control of the treating amount, and the feel of the resultant powder becomes harder. According to the above method 3, since the amount of the metal is small for the large molecular weight of
REFERENCES:
patent: 5366660 (1994-11-01), Tapley
patent: 5536492 (1996-07-01), Mitchnick et al.
Kuroda Akihiro
Shimomura Masataka
Waki Yoshinori
Daito Kasei Kogyo Co., Ltd.
Dodson Shelley A.
Kanebo Ltd.
Lamm Marina
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