Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2000-03-10
2002-02-26
Barts, Samuel (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
Reexamination Certificate
active
06350894
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a table sunscreen composition for topical application to human skin to protect the skin against UV radiation damage. More particularly, the present invention is directed to the use of long chain (C
12
, C
16
and/or C
18
) branched alkyl hydroxybenzoates and/or long chain (C
12
, C
16
) branched chain alkyl benzoates that are surprisingly effective in stabilizing dibenzoylmethane derivatives, particularly 4-(1,1-dimethylethyl)-4′-methoxydibenzoylmethane (PARSOL 1789) such that the PARSOL 1789 is a more effective sunscreen, having a surprisingly increased sunscreen protection factor (SPF) and such that the PARSOL 1789 is more effective over a longer period of time so that the sunscreen composition need not be applied to the skin as frequently.
BACKGROUND OF THE INVENTION AND PRIOR ART
It is well known that ultraviolet light having a wavelength between about 280 nm or 290 nm and 320 nm (UV-B) is harmful to human skin, causing burns that are detrimental to the development of a good sun tan. UV-A radiation, while producing tanning of the skin, also can cause damage, particularly to very lightly colored, sensitive skin, leading to reduction of skin elasticity and wrinkles. Therefore, a sunscreen composition should include both UV-A and UV-B filters to prevent most of the sunlight within the full range of about 280 nm to about 400 nm from damaging human skin.
The UV-B filters that are most widely used commercially in sunscreen compositions are paramethoxycinnamic acid esters, such as 2-ethylhexyl paramethoxycinnamate, commonly referred to as octyl methoxycinnamate or PARSOL MCX, having an ethyl radical extending from the 2 position of the hexyl long chain backbone; and octyl salicylate.
The UV-A filters most commonly used in commercial sunscreen compositions are the dibenzoylmethane derivatives, particularly 4-(1,1-dimethylethyl)-4′-methoxydibenzoylmethane (PARSOL 1789), and 4-isopropyl dibenzoylmethane (EUSOLEX 8020). Other dibenzoylmethane derivatives described as UV-A filters are disclosed in U.S. Pat. Nos. 4,489,057; 4,387,089 and 4,562,067, hereby incorporated by reference. It is also well known that the above described and most commonly used UV-A filters, particularly the dibenzoylmethane derivative, such as PARSOL 1789, suffer in photochemical stability when combined with the above-described most commercially used UV-B filters. Accordingly, when a UV-B filter, such as 2-ethylhexyl paramethoxycinnamate (PARSOL MCX), and/or octyl salicylate, is combined with the dibenzoylmethane derivative UV-A compounds, such as PARSOL 1789, the PARSOL 1789 becomes less photochemically stable necessitating repeated, frequent coatings over the skin for sufficient UV radiation protection.
In accordance with the principles of the present invention, it has been found, quite surprisingly, that by including a C
12
, C
16
, C
18
branched chain hydroxybenzoate of formula (I), preferably C
12
branched chain hydroxybenzoate, and/or a C
12
, C
16
branched chain benzoate of formula (II) into a cosmetic sunscreen formulation containing a UV-A dibenzyolmethane derivative, particularly PARSOL 1789, or EUSOLEX 8020, the dibenzyolmethane derivative is photochemically stabilized so that the dibenzyolmethane derivative-containing sunscreen composition is more effective for filtering out UV-A radiation; the composition filters UV-A radiation for longer periods of time; and, therefore, the sunscreen formulation need not be applied to the skin as frequently while maintaining effective skin protection against UV-A radiation:
wherein
m=5, 7, 9 or mixtures and
n=4, 6, 8 or mixtures;
wherein
m=5, 7 or mixtures and
n=4, 6 or mixtures.
By the addition of the UV-B filter compounds, the cosmetic sunscreen formulation can maintain surprisingly effective skin protection against UV radiation both in the UV-A and UV-B range, with or without common sunscreen additives, such as benzophenone 3, octocrylene, and/or titanium dioxide. The ratio of UV-A to UV-B filter compounds is in the range of about 0.1:1 to about 3:1, preferably about 0.1:1 to about 0.3:1, most preferably about 0.24:1.
SUMMARY OF THE INVENTION
In brief, the present invention is directed to sunscreen compositions containing a dibenzoylmethane derivative UV-A filter compound, such as 4-(1,1-dimethylethyl)-4′-methoxydibenzoylmethane (PARSOL 1789), and a stabilizer/solubilizer for the dibenzoylmethane derivative selected from formula (I) and formula (II), and mixtures thereof:
wherein
m=5, 7, 9 or mixtures and
n=4, 6, 8 or mixtures;
wherein
m=5, 7 or mixtures and
n=4, 6 or mixtures.
Surprisingly, it has been found that these long branched chain alkyl hydroxybenzoates and long branched chain (2 position) benzoates having at least C
4
branches at the 2 position are quite effective in stabilizing the dibenzoylmethane derivative UV-B filter compounds making them more effective; effective for longer periods of time; and, therefore, the sunscreen composition need not be reapplied as frequently to maintain effective UW radiation skin protection.
Accordingly, one aspect of the present invention is to provide a stable sunscreen composition that includes a stabilizer/solubilizer compound selected from formula (I), formula (II), or mixtures capable of stabilizing a dimethylbenzoyl derivative UV-A filter, particularly PARSOL 1789:
Another aspect of the present invention is to provide stabilizer compounds for dimethylbenzoyl derivatives, particularly PARSOL 1789, and methods of manufacturing the stabilizer compounds, capable of stabilizing the dimethylbenzoyl derivatives, and capable of increasing the sunscreen protection factor (SPF) achievable for sunscreen compositions containing the dimethylbenzoyl derivatives to a SPF of at least 20, particularly 20-25 SPF.
Another aspect of the present invention is to provide a stable sunscreen composition that has a SPF of at least 20, without a sunscreen composition additive selected from the group consisting of benzophenone 3, octocrylene or other substituted dialkylbenzalmalonates or substituted dialkylmalonates.
Still another aspect of the present invention is to provide an improved, stable sunscreen composition containing 2-butyloctyl benzoate and/or 2-hexyldecyl benzoate, particularly a 40%, 60% by weight mixture, respectively, having a refractive index of at least about 1.40, particularly about 1.45 to about 1.48, that increases the effectiveness of dimethylbenzoyl derivative sunscreen compounds, particularly 4-(1,1-dimethylethyl)-4′-methoxydibenzoylmethane (PARSOL 1789), in SPF and in duration.
Another aspect of the present invention is to provide an improved, stable sunscreen composition containing 2-butyloctyl hydroxybenzoate, having a refractive index of about 1.49, that increases the effectiveness of dimethylbenzoyl derivative sunscreen compounds, particularly 4-(1,1-dimethylethyl)-4′-methoxydibenzoylmethane (PARSOL 1789), in SPF and in duration.
The above and other aspects and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The sunscreen compositions of the present invention include about 1% to about 3% of a dibenzoylmethane derivative UV-A filter compound, such as 4-(1,1-dimethylethyl)-4′-methoxydibenzoylmethane (PARSOL 1789) and about 1% to about 10% by weight of a stabilizer/solubilizer for the dibenzoylmethane derivative, selected from the group consisting of formula (I), formula (II), and mixtures thereof:
wherein
m=5, 7, 9 or mixtures and
n=4, 6, 8 or mixtures;
wherein
m=5, 7 or mixtures and
n=4, 6 or mixtures.
The compounds of formula (I) and formula (II) are formed by typical esterification and transesterification reactions as follows:
Formula (I)
1. Hydroxybenzoate Esterification Reaction
where
m=5, 7, 9 or mixtures and
n=,4, 6, 8 or mixtures
wherein
m=5, 7, 9 or mixtures and
Bonda Craig A.
Hopper Steven P.
Barts Samuel
Marshall Gerstein & Borun
The C.P. Hall Company
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