Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Reexamination Certificate
2001-01-30
2003-03-11
Dees, Jose′ G. (Department: 1616)
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
C424S060000, C424S401000, C516S053000, C516S077000, C516S922000, C516S923000, C516S924000
Reexamination Certificate
active
06531117
ABSTRACT:
The invention relates to aqueous dispersions of sparingly water-soluble or water-insoluble organic UV filter substances, to the preparation and further processing thereof to give dry powders, and to the use thereof as photostable light protection agents.
The quality and life of many organic materials, for example plastics and coating materials, but also pharmaceutical and cosmetic preparations, can be adversely affected by the action of light, in particular by UV rays. These losses in quality frequently become evident in the case of plastics and coating materials from yellowing, discoloration, cracking or embrittlement of the material. In the case of pharmaceutical and cosmetic preparations, the effect of UV rays can lead to the degradation of the active ingredients present in the formulations.
The harmful effect of the ultraviolet part of solar radiation on the skin or hair, which in the widest sense are also an organic material, is likewise a problem which is increasing in importance. While rays having a wavelength of less than 290 nm (the uvC region) are absorbed by the ozone layer in the earth's atmosphere, rays in the range between 290 nm and 320 nm, the UVB region, cause an erythema, simple sunburn or even burns of varying severity on the skin.
A maximum for the erythema activity of sunlight is given as the relatively narrow range around 308 nm.
Numerous compounds are known for protecting against UVB radiation; these are, inter alia, derivatives of 3-benzylidenecamphor, 4-aminobenzoic acid, cinnamic acid, salicylic acid, benzophenone and 2-phenylbenzimidazole.
It is also important to have available filter substances for the range between about 320 nm and about 400 nm, the UVA region, since its rays can cause reactions in cases of light-sensitive skin. It has been proven that UVA radiation leads to damage of the elastic and collagenous fibers of the connective tissue, leading to premature aging of the skin, and that it is to be regarded as a cause of numerous phototoxic and photoallergic reactions. The harmful effect of UVB radiation can be intensified by UVA radiation.
To protect against UVA rays, derivatives of dibenzoylmethane are used, the photostability of which, however, is inadequate (Int. J. Cosm. Science 10, 53 (1988)).
However, UV radiation can also lead to photochemical reactions, in which case the photochemical reaction products then intervene in the skin's metabolism.
Such photochemical reaction products are mainly free-radical compounds, for example hydroxyl radicals. Undefined free-radical photo products formed in the skin itself can also trigger uncontrolled secondary reactions as a result of their high reactivity. However, singlet oxygen, a non-radical excited state of the oxygen molecule, can also arise during UV irradiation, as can short-lived epoxides and many others. Singlet oxygen, for example, differs from normal triplet oxygen (free-radical ground state) by virtue of its increased reactivity. However, activated, reactive (free-radical) triplet states of the oxygen molecule also exist.
Furthermore, UV radiation is a form of ionizing radiation. There is therefore the risk that ionic species will also form during UV exposure, which then for their part are able to intervene oxidatively in the biochemical processes.
One applications-relevant disadvantage of many UV filters is their poor solubility in water and/or in lipids, as a result of which their use, for example in cosmetic formulations, is often restricted.
A further disadvantage associated with the application of some light protection agents is the appearance of skin irritations and allergies resulting from too high a skin permeability.
GB-A-2 303 549 describes a grinding process for the preparation of micronized insoluble organic UV absorbers in the presence of alkyl polyglycosides. The resulting micronizates can be incorporated into cosmetic light protection preparations.
GB-A-2 286 774 likewise describes a grinding process for the micronization of insoluble organic UV absorbers.
It is an object of the present invention to provide UV light protection agent formulations which bring about effective protection for organic material, in particular for human skin and/or human hair, against UV rays, and which can be readily incorporated into aqueous and into lipophilic systems.
We have found that this object is achieved by aqueous dispersions of sparingly water-soluble or water-insoluble organic UV filter substances which comprise at least one sparingly water-soluble or water-insoluble organic UV filter substance as colloidally disperse phase in amorphous or partially amorphous form.
For the purposes of the present invention, the term “aqueous dispersions” means aqueous suspensions and emulsions. Preferred aqueous suspensions which may be mentioned are those in which the dispersed phase comprises at least one sparingly water-soluble or water-insoluble organic UV filter substance as nanoparticulate particles. Moreover, at the forefront of the invention are also the dry powders or emulsions prepared from the above aqueous suspensions, preferably double emulsions, in particular o/w/o emulsions.
In this connection, the term “sparingly water-soluble organic UV filter substances” means those compounds whose water solubility is <5% by weight, preferably <1% by weight, particularly preferably <0.5% by weight, very particularly preferably <0.1% by weight.
The novel light protection agent formulations are notable for the fact that they comprise at least one sparingly water-soluble or water-insoluble organic UV filter substance whose amorphous proportion is in the range greater than 10%, preferably greater than 30%, particularly preferably in the range from 50 to 100%, very particularly preferably in the range from 75 to 99%. The degree of crystallinity of the UV filter substances can be determined here, for example, by X-ray diffraction measurements.
The content of at least one sparingly water-soluble or water-insoluble organic UV filter substance in the light protection agent formulations according to the invention is in the range from 0.1 to 70% by weight, preferably in the range from 2 to 40% by weight, particularly preferably in the range from 3 to 30% by weight, very particularly preferably in the range from 5 to 25% by weight, based on the dry mass of the formulations.
The mean particle size of the nanoparticulate particles in the aqueous dispersion is, depending on the type of formulation method, in the range below 10 &mgr;m, preferably in the range below 5 &mgr;m, particularly preferably in the range from 0.01 to 2 &mgr;m, very particularly preferably in the range from 0.05 to 1 &mgr;m.
A preferred form of the aqueous dispersions according to the invention is notable for the fact that the particles of the colloidally disperse phase have a core/shell structure, where the core comprises at least one sparingly water-soluble or water-insoluble organic UV filter substance. The shell surrounding the core essentially comprises at least one protective colloid, preferably a relatively high molecular weight compound.
The purpose of this polymer shell is to stabilize the particles in their colloidal state from heterogeneous particle growth (aggregation, flocculation etc.).
One or more polymers can be used for this purpose. The molar masses of the polymers used are in the range from 1000 to 10,000,000 g/mol, preferably in the range from 1000 to 1,000,000 g/mol. In principle, suitable polymers are all those suitable for the pharmaceuticals and cosmetics application sector.
According to the invention, suitable polymeric stabilizers for the coating matrix of the shell are advantageously water-soluble or water-swellable protective colloids such as, for example, cow, pig or fish gelatins, in particular acid- or base-degraded gelatins having Bloom numbers in the range from 0 to 250, very particularly preferably gelatins A 100, A 200, B 100 and B 200, and low molecular weight enzymatically degraded gelatin types having the Bloom number 0 and molecular weights from 15,000 to 25,000 D, such as, for ex
Auweter Helmut
Dausch Wilma M.
Heger Robert
Wünsch Thomas
Zwissler Georg Konrad
BASF - Aktiengesellschaft
Dees Jose′ G.
Keil & Weinkauf
Lamm Marina
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