Solid protector against UV, process for its preparation and use

Details Solid protector against UV, process for its preparation and use Solid protector against UV, process for its preparation and use

1996-05-08

1998-09-22

Dodson, Shelley A.

Drug, bio-affecting and body treating compositions

Topical sun or radiation screening, or tanning preparations

423610, 424400, 424401, 428402, 514772, A61K 742, A61K 4700, C01G 23047

Patent

active

058110828

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a solid protector against UV light, comprising a pigment made up of metal oxide particles reducing the penetration of UV light and having an average primary particle diameter smaller than 0.150 .mu.m. Such solid protectors against UV light are used in the cosmetics industry. The invention also relates to the preparation and use of such a solid protector against UV light.
The penetration of harmful ultraviolet radiation into the skin or other material is prevented according to state-of-the-art technology by using both organic and inorganic protectors against UV radiation. Inorganic UV-protectors include many very fine-grained metal oxides. Corresponding metal oxides are in general also available in pigment grades, in which case they reflect or absorb mainly within the wavelength of visible light. Metal oxides protecting from UV radiation deviate from these pigments in that they are transparent to the wavelength of visible light but, instead, reflect or absorb ultraviolet light. They are called UV-pigments. The diameter of the primary particles of UV-pigments is clearly smaller than that of corresponding pigment particles (for example, 0.1-fold), and the interface of their primary particles is considerably larger (for example 100-fold). UV-pigments are often also called "microcrystalline" pigments of "micropigments".
Known inorganic UV-pigments include fine-grained titanium dioxides. The diameter of their primary particles is in the order of 0.020 .mu.m (0.010-0.100 .mu.m), whereas the crystal size of pigment-grade titanium dioxide is in the order of 0.200 .mu.m (0.160-0.250 .mu.m). UV titanium dioxide can be prepared, for example, by the method of publication EP-A-0 444 798 (Kemira Oy), by methods referred to therein, or by other methods. UV titanium dioxide is available in anatase or rutile form or in amorphous form, and its particle shape is round, oblong or needle-like. UV titanium dioxide is available both coated and uncoated, the coatings being either hydrophilic or hydrophobic.
Zinc oxide as a UV-pigment is known from the publication GB 21 84 356 (Kao Corporation). Other known UV-pigments include oxides of cerium, zirconium and iron, having particle sizes below 0.150 .mu.m and absorbing UV light. There are also known photochromatic UV-pigments in which the ability to protect against light-increases under the effect of UV radiation (EP 526712, Kao Corporation).
Though UV-pigments, when dry, are at least partly agglomerated, their particle size is, nevertheless, so small that the products are highly dust-producing, from which there follow many drawbacks. The working of such a very fine-grained UV-pigment into a well dispersed suspension is often difficult.
The dust problem has been solved in patent publication GB 22 06 339 (Tioxide Group PLC) with respect to UV titanium dioxide by grinding it in an oil phase with the help of an organic dispersing agent in a bead mill. A corresponding method for UV-zinc oxide is known from patent publication EP-A 1-535 972 (Tioxide Specialties Ltd.).
However, the products thus obtained still have deficiencies, of which we mention limited storage stability, need for dispensing devices and for transportation and storage containers, need to mix the stored product or product container, such as a barrel, before dispensing, as well as difficulty of cleaning the said equipment and need to treat the waste slurry produced in their washing. In general it is also necessary to add preservatives to suspension-form UV-pigment dispersions in order to combat microbial growth, even if it would be desirable to have the product keep entirely without preservatives, or at least with substantially smaller preservative doses.
Solid or semi-solid color pellets intended for cosmetics products are known from patent publication PCT 93/00065 (Boots). This invention makes it possible to select a lipstick color from a large number of lipstick color shade alternatives by mixing equal-sized color pellets with an oil mixture, in a numerical quantity ratio indicated by a certain

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