Photostabilization of dibenzoylmethane derivatives

Food or edible material: processes – compositions – and products – Fermentation processes – Material is mammal or fowl derived

Reexamination Certificate

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C424S060000, C424S400000, C424S401000, C514S241000

Reexamination Certificate

active

06803063

ABSTRACT:

The invention relates to the use of 2,4-bis[[4-(2-ethylhexyloxy)-2-hydroxy]phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine for improving the photstability of dibenzoylmethane for improving the photostability of dibenzoylmethane derivatives and to corresponding cosmetic compositions for protecting against UV radiation and to the production of such compositions.
There is a growing need for good topical sun protection preparations in order to prevent the damaging effects of UV light on human skin, for example sunburn, photo-allergic reactions, premature ageing of the skin and skin cancer. Most sun protection preparations now provide good protection against ultraviolet radiation in the wavelength range from 290 to 320 nm (UV-B range). Because numerous studies in recent years have shown that ultraviolet radiation in the wavelength range from 320 to 400 nm (UV-A range) makes a significant contribution to the skin damage caused by sunlight, there is also an increasing requirement for adequate protection against UVA radiation. In addition, the availability of sun protection preparations having a high sun protection factor (hereinafter also referred to as SPF) has led to concerns that users are able to stay in the sun for longer and, as a result, are exposed to an increased amount of UVA radiation.
A UV filter should, ideally, convert absorbed UV radiation quickly and efficiently into harmless thermal energy without, in the process, the UV filter and its protective action being degraded or the function and reliability of the sun protection preparation being impaired. Although there is a large selection of suitable UVB filters, good UVA absorbers are rare because they are mostly of low activity or of inadequate photostability. In particular, dibenzoylmethane derivatives, for example 4-tert-butyl-4′-methoxydibenzoylmethane, the most common UVA filter, which is obtainable commercially, for example, under the designation Parsol 1789 (Givaudan, Switzerland), are degraded relatively quickly under the action of sunlight and, as a result, lose their protective action (R. M. Sayre et al., Allured's Cosmetics & Toiletries, 114 (5): 85-91, 1999). In addition, it is known that the otherwise photostable cinnamic acid esters, which are active as UVB filters, such as 4-methoxycinnamic acid 2-ethylhexyl ester (usually designated octyl methoxycinnamate), which is frequently used in combination with dibenzoylmethanes and which is available, for example, under the tradename Parsol MCX (LaRoche, Switzerland), may, after photoreaction of the dibenzoylmethane derivative, form cycloaddition products with the latter and consequently become destabilised.
For improving the photostability of dibenzoylmethane derivatives, EP-A-0 815 834 has proposed certain amides such as, especially, N,N-diethyl-methylbenzamide and N-butyl-N-acetyl-3-aminopropionic acid ethyl ester. For the same purpose, EP-A-0 970 961 discloses the addition of certain silicon compounds having a benzylidene camphor function. Furthermore, a first photostable UVA filter has been disclosed, namely the terephthalylidene dicamphor sulfonic acid obtainable under the designation Mexoryl SX (Chimex, France), which is water-soluble and has a strong absorption maximum at 345 nm.
DE-A-197 56 921 has also proposed the use of synthetic beeswax for increasing the UV-A-protective performance of cosmetic or dermatological formulations comprising at least one conventional UV-A filter substance and/or a broad-spectrum filter substance, there also being mentioned without any data, inter alia, an O/W lotion comprising 2,4-bis-[[4-(2-ethylhexyloxy)-2-hydroxy]phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine and 4-tert-butyl-4′-methoxy-dibenzoylmethane in addition to 12 further components.
It has now been found, surprisingly, that the broad-spectrum filter 2,4-bis-[[4-(2-ethylhexyloxy)-2-hydroxy]phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine, which has recently come on the market under the designation Tinosorb S (Ciba Speciality Chemicals, Switzerland), is suitable for substantially improving the photostability of dibenzoylmethane derivatives such as 4-tert-butyl-4′-methoxydibenzoylmethane, and that, by that means, destabilisation of cinnamic acid esters such as 4-methoxycinnamic acid 2-ethylhexyl ester can very largely be avoided. In addition, 2,4-bis[[4-(2-ethylhexyloxy)-2-hydroxy]phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine supplements the spectral range of the dibenzoylmethanes and as a result additionally contributes to the protective action of products comprising such compounds.
The invention accordingly relates to the use of 2,4-bis[[4-(2-ethylhexyloxy)-2-hydroxy]-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine for improving the photostability of dibenzoylmethane derivatives. The invention relates especially to the use of 2,4-bis[[4-(2-ethylhexyloxy)2-hydroxy]phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine in or for the production of a cosmetic composition comprising a dibenzoylmethane derivative, for the purpose of improving the photostability of the dibenzoylmethane derivative. The stabilisation can in principle be achieved by bringing an effective amount of 2,4-bis[[4-(2-ethylhexyloxy)-2-hydroxy]phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine into contact with the dibenzoylmethane derivative or by incorporating them into the composition.
The invention relates also to cosmetic compositions (especially so-called sun protection preparations or light protection preparations) for topical use for protection against UV radiation, especially sunlight, comprising a cosmetically acceptable carrier, at least one dibenzoylmethane derivative, at least one cinnamic acid ester and an effective amount of 2,4-bis[[4-(2-ethylhexyloxy)-2-hydroxy]phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine. In accordance with the invention, such compositions may be produced by incorporating the dibenzoylmethane derivative, the cinnamic acid ester and 2,4-bis[[4-(2-ethylhexyloxy)-2-hydroxy]phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine into the cosmetically acceptable carrier.
2,4-Bis[[4-(2-ethylhexyloxy)-2-hydroxy]phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine, which according to INCI nomenclature is designated Bis Ethylhexyloxyphenol Methoxyphenyl Triazine or, in the context of the present invention, is also abbreviated to EHPT, is, as mentioned, a known broad-spectrum filter, which is commercially available under the name Tinosorb S (Ciba Speciality Chemicals, Switzerland). The cosmetic compositions obtainable in accordance with the invention may contain typically about from 0.1 to 15% by weight, preferably about from 0.5 to 10% by weight, 2,4-bis[[4-(2-ethylhexyloxy)-2-hydroxy]phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine.
In accordance with the invention, any dibenzoylmethane derivative that is active as a UV filter is, in principle, suitable as the dibenzoylmethane derivative, especially alkyl- and/or alkoxy-substituted dibenzoylmethanes, such as 2-methyldibenzoylmethane, 4-methyldibenzoylmethane, 4-isopropyldibenzoylmethane, 4-tert-butyldibenzoylmethane, 2,4-dimethyldibenzoylmethane, 2,5-dimethyldibenzoylmethane, 4,4′-diisopropyldibenzoyl-methane, 4,4′-dimethoxydibenzoylmethane, 4-tert-butyl-4′-methoxydibenzoylmethane, 2-methyl-5-isopropyl-4′-methoxydibenzoylmethane, 2-methyl-5-tert-butyl-4′-methoxydibenzoylmethane, 2,4-dimethyl-4′-methoxydibenzoylmethane and 2,6-dimethyl-4-tert-butyl-4′-methoxydibenzoylmethane. Dibenzoylmethane derivatives that are preferably used are 4-isopropyldibenzoylmethane, which is available under the name Eusolex 8020 (Merck, Germany) and, especially, 4-tert-butyl-4′-methoxydibenzoylmethane, which is available, for example, under the name Parsol 1789 (Givaudan, Switzerland). Typically, the cosmetic compositions obtainable in accordance with the invention may contain about from 0.1 to 10% by weight dibenzoylmethane deriv

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