Sun screen formulations

Details Sun screen formulations Sun screen formulations

2000-12-20

2003-02-18

Dodson, Shelley A. (Department: 1616)

Drug, bio-affecting and body treating compositions

Topical sun or radiation screening, or tanning preparations

C424S060000, C424S400000, C424S401000, C514S241000

Reexamination Certificate

active

06521217

ABSTRACT:

The present invention relates to new formulations and, in particular, to new UV-protection formulations which comprise a micronised UV absorber, wherein the micronised UV absorber is present in the oil phase of the formulation.
It has long been known that prolonged exposure to UV radiation which reaches the surface of the earth can lead to the formation of erythemas or light dermatoses, as well as to an increased incidence of skin cancers, or accelerated skin ageing.
Various sunscreen formulations have been proposed which include a material which is intended to counteract UV radiation, thereby inhibiting the said undesired effects on the skin.
A great number of compounds has been proposed for use as UV protectants in sunscreen formulations, especially soluble organic UV absorbers and insoluble micronised inorganic compounds, in particular zinc oxide and titanium dioxide.
With respect to the use in sunscreen formulations of soluble organic UV absorbers, they have the disadvantages that their effectiveness as UV protectants in terms of SPF (Sun Protection Factor) in a sunscreen formulation is often too low for commercial purposes; as a result of their solubility, they exhibit relatively high allergenic potential; and that as a result of intrinsic photochemical lability, the duration of the protective effect is often too low.
The high specific weight of insoluble inorganic compounds, such as titanium dioxide leads to a reduced stability of formulations containing them. Moreover, such inorganic compounds have been claimed to generate toxic radicals under the influence of light and water (“Redox Mechanisms in Heterogeneous Photocatalysis”, Serpone et al, Electrochemistry in Colloids and Dispersions, Editors Mackay and Texter, VCH Publishers Inc., NewYork 1992).
In GB-A-2303549, there is described a method of producing micronised, insoluble organic UV absorbers, as well as a sunscreen composition comprising a) 0.1 to 15%, preferably 0.5 to 10% by weight, based on the total composition of a micronised formulation of an insoluble organic UV absorber, produced according to the said method; and optionally b) a cosmetically acceptable carrier.
Micronised, insoluble organic UV absorbers so obtained, when used in sunscreen formulations, provide excellent UV protection and have at least as high an SPF rating as corresponding sunscreen formulations containing a known inorganic UV absorber. Unlike the latter UV absorbers, micronised, insoluble organic UV absorbers show no tendency, under the influence of light, to generate radicals which could damage or sensitise human skin.
In a further development of the concept disclosed in GB-A-2303549, it has now been found that, micronised, insoluble organic UV absorbers which are present in the oil phase of the sun screen formulation surprisingly show a significant improvement in sun protection.
Accordingly, the present invention provides, as a first aspect, a sun screen formulation, which is especially suitable for use in pharmaceutical or cosmetic applications, comprising
(a) a micronised organic UV absorber; and
(b) a cosmetically acceptable carrier,
wherein the micronised organic UV absorber is present in the oil phase of the formulation.
The micronised organic UV absorber, component (a), is preferably produced by the method described in GB-A-2303549, namely by a process which comprises grinding an organic UV absorber, in coarse particle form, in a grinding apparatus, in the presence of 1 to 50%, preferably 5 to 40% by weight, based on the micronised organic UV absorber, of an alkyl polyglucoside having the formula C
n
H
2n+1
O(C
6
H
10
O
5
)
x
H, in which n is an integer ranging from 8 to 16 and x is the mean polymerisation level of the glucoside moiety (C
6
H
10
O
5
) and ranges from 1.4 to 1.6, or an ester thereof.
The grinding apparatus used to produce the micronised organic UV absorber may be, e.g., a jet, ball, vibration or hammer mill, preferably a high speed stirring mill or impact mill, especially a rotating ball mill, vibrating mill, tube mill or rod mill.
The alkyl polyglucoside may consist of a C
1
-C
12
ester of the compound of formula C
n
H
2n+1
O(C
6
H
10
O
5
)
x
H, namely an ester formed by reacting a C
1
-C
12
acid, such formic, acetic, propionic, butyric, sulfosuccinic, citric or tartaric acid, with one or more free OH groups on the glucoside moiety (C
6
H
10
O
5
).
The micronised organic UV absorber may be incorporated into the oil phase with different methods.
In a preferred incorporation method the micronised organic UV absorber may be incorporated as powder. For this purpose the micronised organic UV absorber may be subjected to known powdering processes like solvent precipitation, vacuum spraying from solvents etc. These powders have a particle size of 0, 1 nm to 2 &mgr;m. In order to prevent agglomeration processes the micronised organic UV absorber may be coated before powdering with a surface active agent like nonionic, anionic, cationic or amphoteric surfactants like phospholipids or known polymers, for example PVP, acrylates etc.
As example, a water-soluble surfactant or emulsifier is added to the aqueous suspension of the micronised organic UV absorber. The mixture is then spray-dried. During the spray-drying process the surfactant or emulsifier sheathes the micro-particles in form of a thin film and inhibits aggregation or facilitates the re-dispersion to the desired particle size in the oil phase.
In another preferred method the micronised organic UV absorber may be transferred to the oil phase during the preparation of the sun screen formulation: when mixing the micronised organic UV absorber which was produced by aqueous grinding with the oil phase of the sun screen formulation the water will be removed by known methods like vacuum removal. By this measure the micronised organic UV absorber will be transferred to the oil phase of the formulation.
Furthermore, it was observed that the micronised organic UV absorber which is present in the aqueous phase of the sun screen composition will migrate into the oil phase after a couple of days or weeks.
Therefore, another aspect the present invention refers to a method of preparation of the sunscreen composition by micronising the organic UV absorber in the first step as aqueous suspension, mixing the micronised organic UV absorber with the oil phase of the sunscreen composition in a second step and storing the formulation for at least three weeks in a final step.
Suitable organic UV absorber may be, e.g., a triazine, a benzotriazole, a vinyl group-containing amide, a cinnamic acid amide or a sulfonated benzimidazole UV absorber.
A preferred class of triazine compounds is that having the formula
in which
R
1
, R
2
and R
3
, independently, are H; OH; C
1
-C
3
alkoxy; NH
2
; NH—R
4
; N(R
4
)
2
; OR
4
, wherein R
4
is C
1
-C
3
alkyl; phenyl; phenoxy; anilino; pyrrolo, in which the respective phenyl, phenoxy or anilino, or pyrrolo moieties are not substituted or substituted by one, two or three substitutents selected from OH, carboxy, CO—NH
2
, C
1
-C
3
alkyl, C
1
-C
3
alkoxy, a methylidenecamphor group, a group —(CH═CH)
m
C(═O)—OR
4
, a group
 or the corresponding alkali metal, ammonium, mono-, di- or tri-C
1
-C
4
alkylammonium, mono-, di- or tri-C
2
-C
4
alkanolammonium salts, or the C
1
-C
3
alkyl esters thereof, a radical of formula (1a)
R
5
is hydroxy; C
1
-C
5
alkyl that is unsubstituted or substituted by one or more OH groups; C
1
-C
5
alkoxy; amino; mono- or di-C
1
-C
5
alkylamino; M; a radical of formula
R′, R″ and R′″ are each independently of the others C
1
-C
14
alkyl that is unsubstituted or substituted by one or more OH groups;
R
6
is hydrogen; M; C
1
-C
5
alkyl; or a radical of the formula —(CH
2
)
m
2
—O—T
1
;
M is a metal cation;
T
1
is hydrogen; or C
1
-C
8
alkyl;
m is 0 or 1;
m
1
is from 1 to 5;
m
2
is from 1 to 4;
m
3
is from 2 to 14.
Preferred compounds of formula (1) are those having the formula
in which
R
7
and R
8
, independently of one another, are C
1
-C
18
alkyl; C
2
-C
18
alkenyl; a radi

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