Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Patent
1995-08-11
1998-02-03
Le, H. Thi
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
427215, 427218, 427219, 428403, 428404, B32B 516
Patent
active
057142602
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to ultrafine rutile type titanium dioxide particles containing iron, a process for producing the same, and a composition containing the same such as UV shielding cosmetics, pharmaceutical compositions, and UV shielding paints.
BACKGROUND OF THE INVENTION
Ultrafine titanium dioxide particles having a primary particle size of about 0.1 .mu.m or less are transparent to visible lights, i.e., capable of transmitting rays of visible light when incorporated in resin films or shapes, and on the other hand, they can shield ultraviolet rays to protect materials which change a color or denature through exposure to ultraviolet radiation. In this way it has been well known that the ultrafine titanium dioxide particles exhibit different properties than those of pigmentary titanium dioxide particles having a primary particle size of 0.15 to 0.5 .mu.m. For this reason, recently specific attention has been focussed on utilization of the ultrafine titanium dioxide particles as UV shielding cosmetics for preventing sunburn due to UV light. However, the ultrafine titanium dioxide particles which have heretofore been commercially available have so high coagulation force that they are difficult to perfectly disperse at a primary particle level in both water and an oily solvent. For example, when UV shielding cosmetics containing such ultrafine titanium dioxide particles are applied to skin, intensely bluish colored light scatter occurs to impart a bluish tint to the cosmetics, which is a drawback showing the skin unhealthy. Moreover, conventional fine titanium dioxide particles can sufficiently shield ultraviolet rays of wavelengths in the range B (wavelengths in the range from 320 to 290 nm), but are insufficient in shielding ultraviolet rays of wavelengths in the range A (wavelengths in the range from 380 to 320 nm). More recently, there has been a concern about skin disorder owing to ultraviolet rays in the range A and to cope with this problem it is practical to use additionally organic ultraviolet absorbents.
There has been proposed a cosmetic composition comprising fine titanium dioxide particles and fine iron oxide particles which is excellent in UV shielding effect and does not exhibit a bluish tint as, for example, disclosed in JP-A 62-67014. However, a simple mixture of titanium dioxide particles and iron oxide particles may cause a problem of color separation in the cosmetics due to a difference in dispersibility and of insufficient effectiveness in shielding ultraviolet rays in the range A. Recently there have been proposed several methods of forming a unitary pigment comprising titanium dioxide and iron oxide to prevent the aforementioned color separation. For example, there have been proposed (1) a method comprising treating titanium dioxide particles having an average particle size of 0.01 to 1 .mu.m with hydrous iron oxides and then drying and/or firing the treated particles as disclosed in JP-B 4-5001, (2) a method comprising treating titanium dioxide particles having a maximum particle size of 0.1 .mu.m with an iron salt of basic higher fatty acid as disclosed in JP-A 61-264063, and (3) a method comprising treating titanium dioxide particles having a maximum particle size of 0.1 .mu.m or less with an oxide or hydroxide of aluminum, silicon, or iron as disclosed in JP-A 2-204326. However, all these methods employ procedures of using fine titanium dioxide particles, depositing iron hydroxide or oxide on the surfaces of the particles, and drying or firing the treated particles. These methods lead to insufficient reduction in the so-called bluish coloration as well as insufficient shielding effect to ultraviolet radiation in the range A. There has also been proposed a composite titanium dioxide-iron oxide in a ratio of 0.05 to 50 expressed as Fe.sub.2 O.sub.3 /TiO.sub.2 by weight as disclosed in JP-A 2-178219. Although this is for the purpose of improving the titania sol for the insufficient ability of shielding ultraviolet light rays in the range A, it suffers from limitations on
REFERENCES:
patent: 5165995 (1992-11-01), Losoi
patent: 5468289 (1995-11-01), Herget et al.
Patent Abstracts of Japan, vol. 008, No. 212 (C-244), 27 Sep. 1984.
European Official Action dated May 12, 1997, issued in a counterpart foreign application.
Futamata Hideo
Hattori Masakazu
Okuda Haruo
Sakai Akihito
Ishihara Sangyo Kaisha Ltd.
Le H. Thi
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