Light screening compositions

Abstract: Photostable, cosmetic light-screening composition, comprising, in a cosmetically acceptable vehicle containing at least one fatty phase, about 0,1 to about 5 %, in particular about 1 to about 3 % by weight, of a dibenzoylmethane type UV-A screening agent and at least about 0,5 %, in particular about 0,5 to about 4,5 % by weight, of a α-cyano-β,β-diphenylacrylate stabiliser, the mole ratio of the acrylate to the dibenzoylmethane derivative being less than 0.8, if the amount of the dibenzoylmethane is 1% or more, and, optionally, at least one conventional UV-B filter.

Description: The invention relates to photostable, cosmetic light-screening compositions for the protection of the human epidermis and the hairs against the ultraviolet rays of wavelengths between 320 and 400 nm, and between 290 and 400 nm respectively. In particular, it relates to such compositions which comprise, in a cosmetically acceptable vehicle containing at least one fatty phase, 0,1 to 5 %, in particular 1 to 3 % by weight, of a dibenzoylmethane type UV-A screening agent, and at least 0,5 %, in particular 0,5 to 4,5 % by weight, of a α-cyano-β,β-diphenylacrylate (I) type stabiliser, the mole ratio of the acrylate to the dibenzoylmethane derivative being less than 0.8, if the amount of the dibenzoylmethane is 1% or more, and optionally, at least one UV-B filter. Though the compounds I are themselves effective in absorbing the UV radiation, primarily in the erythemic region (290 - 320nm), their present function is to photostabilise the above captioned UV-A-filters. As far as the UV-A light screen agent of the novel combinations is concerned, the preferred compound is 4-tert. butyl-4'-methoxydibenzoylmethane, as disclosed, e.g. in USP 4 387 089 or CH-Patent 642 536. Other suitable compounds of this particular type are: 2-methyldibenzoylmethane, 4-methyl-dibenzoyl-methane, 4-isopropyldibenzoylmethane, 4-tert-butyldibenzoyl-methane, 2,4-dimethyldibenzoylmethane, 2,5-dimethyldibenzoylmethane, 4,4'-diisopropyldibenzoylmethane, 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. Examples of suitable compounds I are 2-ethylhexyl-2-cyano-3,3-diphenylacrylate and 2-ethyl-2-cyano-3,3-diphenylacrylate. The function of the formula I compound is, as pointed out above, to photostabilize the involved UV-A screening agents, i.e. to guarantee a constant protection during prolonged exposure to the UV light. This way, if a repeated application of the cosmetic formulation at various intervals is required, these intervals can be extended. The present invention relates thus also to a process for stabilising dibenzoylmethane UV-A screening agents with respect to the UV radiation of wavelengths between 320 and 400 nm, characterised in that 0,5 to 4,5 % by weight of the stabiliser is added to 0,1 to 5 % by weight of the dibenzoylmethane UV-A screening agent. The desired stabilisation of the material of UV-A filters is easily established by strictly parallel experiments with the respective UV-A filters and the compounds I using an appropriately equipped Xenon lamp as a solar simulator. Irradiated are standard preparations of the investigated products, e.g. solutions in, preferably, higher boiling cosmetic solvents, e.g. deltyl (isopropyl myristate), the resulting sunscreen being spread on glass plates. After the irradiation, the plates are immersed into a suitable solvent (e.g. ethanol) and the UV spectrum is recorded. The stabilising effect is directly correlated to the difference in absorbance at λ max. before and after the irradiation. Usually, a combination of UV-A filter and stabiliser as exemplified below is used for the assessment. Both components of the present combination of the light-screening agents are lipophilic. The cosmetic formulations contain thus at least one fatty phase, and the formulations can consequently present themselves in the form of emulsions, lotions or gels. Suitably the cosmetic screening composition takes the form of an oil, a lotion, a gel, a solid stick, an emulsion, e.g. cream, milk or of a vesicular dispersion of ionic or nonionic amphiphilic lipids, an aerosol, a spray, a foam, a powder, a shampoo, a hair conditioner or lacquer or a make-up, etc. The usual solvents known to the skilled practitioner can be used for the preparation of these forms, e.g. oils, waxes, alcohols, polyols, etc. The preferred agents are fatty acids, esters, fatty alcohols, but also ethanol, isopropanol, propylene glycol, glycerine, etc. The cosmetic formulations may contain further adjuvants, e.g. further solvents, thickeners, emollients, emulsifiers, humectants, tensides, preservatives, antifoams, fragrances, oils, waxes, lower polyols and monohydric alcohols, propellants, silicones, colourings and pigments, etc. It may be also added further monomeric or polymeric UV filters (e.g. polysiloxanes as disclosed in EP 538431, polyacrylates, etc.). These are conveniently selected from the list according to the desired chemical and physical properties of the formulation, e.g. according to the desired degree of protection, to wavelength, ε max, solubility, stability, safety, see e.g. SÖFW Journal 122 , 8 (1996) 543 seq., Cosmetics & Toiletries 107 (1982) 45 seq. In case of protection of the hairs, the suitable formulations are shampoos, conditioners, lotions, gels, emulsions, dispersions, lacquers, etc. The preparation of all these formulations is well known to the skilled artisan in this field. As still further suitable UV-B filters, microfine pigments, such as the usual micropigments of metal oxides may be used. Particularly in case of emulsions, such UV filters may, naturally, also be water-soluble derivatives. Suitable amounts of the UV-B filter are 1 - 12 %. The most important advantage stems from the low dosage of the stabiliser, which dosage can be considerably smaller than the dosages of the UV-A filter used. The practical user is thus completely free in the choice regarding the material used for the filtration of the UV-B rays. In this respect, the novel stabilisation is superior to the particular way of stabilisation as disclosed in EP 514 491 B1, and this for the following reason: According to this known process, a ratio of compound I to dibenzoylmethane being not less than 0.8 in compulsory, which ratio narrows the possibilities in the means of achieving the absorption of the UV light over the total range, resulting in the so-called total block. Convenient couples of dibenzoyl methane derivatives and acrylates are as follow: dibenzoyl methane compound I 1 0,5 1 0,9 1,5 1 2 1 2 1,5 2,5 1,5 2,5 2 3 2 3 2,5 Examples O/W SUNSCREEN LOTION 1 % W/W A) Glyceryl mono myristate 4.0 Cetyl alcohol 1.0 Coco-caprylate/caprate (Mixture of esters of coconut alcohol and n-octanoic acid and n-decanoic acid) (sold under trade name CETIOL® LC by HENKEL) Butyl methoxy dibenzoylmethane 1.0 (1-[4-(1,1-dimethylethyl)phenyl]-3-(4-methoxyphenyl)-1,3-propandione) (sold under the trade name PARSOL® 1789 by GIVAUDAN-ROURE S.A.) 10.0 Octocrylene (2-Ethylhexyl-2-cyano-3,3-diphenylacrylate, sold under the trade name UVINUL® N-539 by BASF) 0.9 Mixture of parabens in phenoxy ethanol 0.6 Potassium cetyl phosphate (potassium salt of hexadecyl phosphate) (sold under the trade name AMPHISOL® K by GIVAUDAN-ROURE S.A.) 2.0 EDTA Na2 0.1 B) Deionized water 64.95 Carbomer (1% dispersion in water, homopolymer of acrylic acid crosslinked with an allyl ether of sucrose) (sold under the trade name CARBOPOL®980 by B.F. GOODRICH) 10.0 Propylene glycol 5.0 C) Potassium hydroxyde, 10% solution 0.45 100.00 % W/W A) Glyceryl mono myristate 4.0 Cetyl alcohol 1.0 Coco-caprylate/caprate 10.0 Butyl methoxy dibenzoylmethane 2.0 Octocrylene 1.5 Mixture of parabens in phenoxy ethanol 0.6 Potassium cetyl phosphate (potassium salt of hexadecyl phosphate) 2.0 EDTA Na2 0.1 B) Deionized water 63.35 Carbomer (1% dispersion in water, homopolymer of acrylic acid crosslinked with an allyl ether of sucrose) 10.0 Propylene glycol 5.0 C) Potassium hydroxyde, 10% solution 0.45 100.00 % W/W A) Glyceryl mono myristate 4.0 Cetyl alcohol 1.0 Coco-caprylate/caprate 10.0 Butyl methoxy dibenzoylmethane 3.0 Octocrylene 2.5 Mixture of parabens in phenoxy ethanol 0.6 Potassium cetyl phosphate (potassium salt of hexadecyl phosphate) 2.0 EDTA Na2 0.1 B) Deionized water 61.35 Carbomer (1% dispersion in water, homopolymer of acrylic acid crosslinked with an allyl ether of sucrose) 10.0 Propylene glycol 5.0 C) Potassium hydroxyde, 10% solution 0.45 100.00

Claims: Photostable, cosmetic light-screening composition, comprising, in a cosmetically acceptable vehicle containing at least one fatty phase, 0,1 to 5 %, in particular 1 to 3 % by weight, of a dibenzoylmethane type UV-A screening agent and at least 0,5 %, in particular 0,5 to 4,5 % by weight, of a α-cyano-β,β-diphenyl-acrylate stabiliser, the mole ratio of the acrylate to the dibenzoylmethane derivative being less than 0.8, if the amount of the dibenzoylmethane is 1% or more, and, optionally, at least one conventional UV-B filter. A composition according to Claim 1,wherein the stabilizer is 2-ethylhexyl-2-cyano-3,3-diphenyl-acrylate (preferred) or ethyl-2-cyano-3,3-diphenyl-acrylate. Composition according to claim 1 or 2, characterised in that the dibenzoylmethane derivative is selected from the following compounds: 2-methyldibenzoylmethane, 4-methyl-dibenzoyl-methane, 4-isopropyldibenzoylmethane, 4-tert-butyldibenzoyl-methane, 2,4-dimethyldibenzoylmethane, 2,5-dimethyldibenzoylmethane, 4,4'-diisopropyldibenzoylmethane, 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. Composition according to anyone of the preceding claims, characterised in that the dibenzoylmethane derivative is 4-tert-butyl-4'-methoxydibenzoylmethane. Composition according to anyone of the preceding claims, characterised in that it takes the form of an oil, a lotion, a gel, a solid stick, an emulsion e.g. cream, milk or of a vesicular dispersion of ionic or nonionic amphiphilic lipids, an aerosol, a spray, a foam, a powder, a shampoo, a hair conditioner or lacquer or a make-up. Composition according to anyone of the preceding claims, characterised in that it contains, in addition, cosmetic adjuvants selected from solvents, thickeners, emollients, emulsifiers, humectants, tensides, preservatives, antifoams, fragrances, oils, waxes, lower polyols and monohydric alcohols, propellants, silicones, colourings and pigments. A composition according to any one of the preceding claims, wherein the UV-A-filter is present in amounts of 0.1 - 5 %, the stabiliser is present in amounts of 0.5 to 4.5 %, and the UV-B-filter is present in amounts of 1 - 12 %. Process for stabilising dibenzoylmethane UV-A screening agents with respect to UV radiation of wavelengths between 320 and 400 nm, characterised in that 0,5 to ,5 % by weight of the acrylate stabiliser defined in Claim 1 is added to 0,1 to 5 % by weight of the dibenzoylmethane UV-A light-screening agent, the mole ratio of the acrylate to the dibenzoylmethane derivative being less than 0.8, if the amount of the dibenzoylmethane is 1% or more.

Inventors: GONZENBACH HANS ULRICH, PITTET GILBERT, GONZENBACH, HANS ULRICH, PITTET, GILBERT
Applicants: HOFFMANN LA ROCHE, F. HOFFMANN-LA ROCHE AG
Application year: 1996
Main classification: A61K7
IPC codes: A61K8, A61Q17