Sunscreen compositions

A sunscreen composition comprising a water-in-oil emulsion which comprises an aqueous phase and an oil phase, the oil phase comprising an organic sunscreen agent and polyethylene, the oil phase having suspended therein microfine zinc oxide having a particle size in the range of from about 0.01 to about 0.25 microns, the amount of sunscreen agent being in the range of from about 1% to about 12%, the amount of polyethylene being in the range of from about 0.2% to about 5% and the amount of zinc oxide being in the range of from about 1% to about 10%, the percentages being by weight based on the weight of the water-in-oil emulsion.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to novel sunscreen compositions. 
2. Description of the Prior Art 
Sunscreen compositions are commonly used during outdoor work or leisure 
pursuits for protection of exposed skin against painful sunburn. Many 
effective sunscreen preparations are sold commercially or are described in 
the cosmetic or pharmaceutical literature. In general, sunscreen 
preparations are formulated in the form of a cream, lotion or oil 
containing as the active agent an ultraviolet radiation-absorbing chemical 
compound. The active agent acts to block the passage of erythematogenic 
radiation, thereby preventing its penetration into the skin. 
The ideal sunscreen formulation should be nontoxic and non-irritating to 
skin tissue and be capable of convenient application to the skin in a 
uniform and continuous film. The product should be sufficiently stable 
chemically and physically so as to provide an acceptable shelf life upon 
storage. It is particularly desirable that the preparation should retain 
its protective effect over a prolonged period after application. Thus, the 
active agent when present on the skin must be resistant to chemical- or 
photo-degradation, to absorption through the skin and to removal by 
perspiration, skin oil or water. For aesthetic reasons, the product should 
be substantially odorless (or be capable of being scented) and be 
non-staining to the skin or clothing. 
Many agents have been found to be effective sunscreen agents. Among the 
effective sunscreen agents heretofore employed are certain cinnamate 
esters, in particular, octyl methoxycinnamate. See, for example, U.S. Pat. 
Nos. 4,917,882; 5,093,109; 4,671,955 and 4,683,134. 
Finely divided zinc oxide (ZnO) has also been employed as a sunscreen 
agent. See U.S. Patent 5,032,390 and PCT International Publication WO 
92/13517. It has been suggested to combine ZnO and cinnamate esters in 
sunscreen compositions. See U.S. Pat. Nos. 4,917,882; 4,671,955 and 
4,683,134. 
U.S. Pat. No. 4,264,581 describes a sunscreen composition containing the 
sunscreen agents octyl dimethyl p-aminobenzoic acid ester and oxybenzone 
in combination with a small amount of polyethylene. The specific function 
of the polyethylene in the composition is not disclosed. 
It is an object of the present invention to provide a novel sunscreen 
composition. 
SUMMARY OF THE INVENTION 
The above and other objects are realized by the present invention, one 
embodiment of which relates to a sunscreen composition comprising a 
water-in-oil emulsion which comprises an aqueous phase and an oil phase, 
the oil phase comprising an organic UV-absorbing sunscreen agent such as, 
e.g., octyl methoxycinnamate, octyl dimethyl para-aminobenzoic acid, 
octocrylene (2-ethylhexyl-2-cyano-3,3-diphenylacrylate) and mixtures 
thereof, and polyethylene, the oil phase having suspended therein 
microfine zinc oxide having a particle size in the range of from about 
0.01 to about 0.25 microns, the amount of octyl methoxycinnamate being in 
the range of from about 1% to about 12%, the amount of polyethylene being 
in the range of from about 0.2% to about 5% and the amount of zinc oxide 
being in the range of from about 1% to about 10%, the percentages being by 
weight based on the weight of the water-in-oil emulsion.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention is predicated on the discovery that the addition of 
polyethylene in specific critical amounts to a water-in-oil emulsion 
containing the sunscreen agents ZnO having a specific particle size and 
the above sunscreen agents synergistically enhances the sun protection 
factor of the combined sunscreen agents. 
Thus, it is expected that the contribution of individual sunscreen agents 
to the overall sun protection factor (SPF) of a composition containing the 
agents is additive. Unexpectedly, however, it has been found that the 
presence of polyethylene in sunscreen compositions containing ZnO and the 
above sunscreen agents synergistically increases the SPF of the 
composition to a value far greater than the sum of the SPF's of the 
individual sunscreen agents. 
It is preferred that the sunscreen composition be formulated in 
water-in-oil emulsion form, and most preferably in the form of a cream or 
lotion. 
The ZnO, sunscreen agent and polyethylene are preferably dissolved or 
suspended in an oil phase and the aqueous phase added thereto under strong 
homogenization to produce the water-in-oil emulsion. The weight ratio of 
the aqueous phase to the oil phase in the emulsion compositions of the 
invention is preferably in the range of from about 2:1 to about 1:4. 
The amount of sunscreen agent may vary from about 1% to about 12%, and most 
preferably from about 4% to about 10%. 
The amount of polyethylene incorporated into the water-in-oil emulsion 
composition of the invention should be in the range of from about 0.2% to 
about 5%, and most preferably from about 0.5% to about 3%. 
Suitable ingredients for forming the oil phase include: 
Light liquid paraffin (emollient) 
Liquid paraffin (emollient) 
C12-15 alkyl benzoate (emollient) 
Fatty acid esters, e.g., isopropyl palmitate, cetearyl octanoate 
(emollient) 
Triglycerides (emollient) 
Lecithin (dispersant for ZnO) 
Glyceryl sorbitan oleostearate (emulsifier) 
PEG-7 hydrogenated castor oil (emulsifier) 
Silicone oil (provides water resistance) 
PVP hexadecene copolymer (provides water resistance) 
Polyethylene (aids film formation) 
Solulan PB20 (dispersant for ZnO) 
Cyclomethicone (skin feel) 
It will be understood by those skilled in the art that any inert 
cosmetically acceptable oil which is capable of suspending particulate ZnO 
and dissolving the sunscreen agent and when hot of dissolving the 
polyethylene may be utilized in the compositions of the invention. 
It will also be understood that any conventional adjuvant, including 
emulsifying agent, stabilizer, preservative, etc., conventionally employed 
in water-in-oil sunscreen compositions may be added to either or both of 
the phases of the composition of the invention. 
Exemplary of suitable adjuvants are: 
Light liquid paraffin (emollient) 
Liquid paraffin (emollient) 
C12-15 alkyl benzoate (emollient) 
Fatty acid esters, e.g., isopropyl palmitate, cetearyl octanoate 
(emollient) 
Triglycerides (emollient) 
Lecithin (dispersant for ZnO) 
Glyceryl sorbitan oleostearate (emulsifier) 
PEG-7 hydrogenated castor oil (emulsifier) 
Silicone oil (provides water resistance) 
PVP hexadecene copolymer (provides water resistance) 
Polyethylene (aids film formation) 
Solulan PB20 (dispersant for ZnO) 
Imidazolidinyl urea (preservative) 
Phenonip (preservative) 
Parabens (preservative) 
BHT (anti-oxidant) 
Propylene glycol (moisturizer) 
Magnesium sulfate (emulsion stabilizer) 
Cyclomethicone (skin feel) 
The invention is illustrated by the following non-limiting examples. 
EXAMPLE 1 
The ingredients in the compositions listed in Table I were formulated as 
follows: 
A zinc oxide premix was prepared by blending ZnO having a particle size of 
0.1 .mu.m, light liquid paraffin, PVP/hexadecene copolymer, PPG-20 lanolin 
alcohol ether, lecithin and cetearyl octanoate, followed by passing the 
blend through a triple roll mill. 
An oil phase was prepared by heating polyethylene in isopropyl palmitate at 
120.degree. C. until dissolved, followed by adding the remainder of the 
oil phase ingredients, e.g., light liquid paraffin, C12-15 alkyl benzoate, 
isopropyl palmitate, phenyl trimethicone, glyceryl sorbitan oleostearate 
and PEG-7 hydrogenated castor oil, including the octyl methoxycinnamate 
and the zinc oxide premix which were preheated to 80.degree. C. Strong 
shear was applied to the mix in a homogenizer until the oil phase was 
uniform. 
The aqueous phase was prepared by adding the water-soluble components, 
e.g., propylene glycol and magnesium sulfate, to water with mixing at 
80.degree. C. 
The aqueous phase is then added to the oil phase with strong homogenization 
until a uniform water-in-oil emulsion is obtained which is then cooled to 
about 40.degree.-45.degree. C. Cyclomethicone and preservatives (and 
fragrances, if needed) are then added and the emulsion further cooled to 
room temperature. 
TABLE I 
__________________________________________________________________________ 
FORMULATIONS 
Ingredients I II III IV V VI VII 
__________________________________________________________________________ 
Proplyene Glycol 2.0 2.0 2.0 2.0 2.0 2.0 2.0 
Magnesium Sutfate 0.5 0.5 0.5 0.5 0.5 0.5 0.5 
Germall 115 (imidazolidinyl urea) 
0.2 0.2 0.2 0.2 0.2 0.2 0.2 
Methylparaben 0.15 
0.15 
0.15 
0.15 
0.15 
0.15 
0.15 
Water 50.37 
50.37 
50.37 
50.37 
50.60 
50.60 
54.35 
Arlacel 481 (glyceryl sorbitan oleostearate) 
1.5 1.5 1.5 1.5 1.5 1.5 1.5 
Arlacel 989 (PEG-7 hydrogemted castor oil) 
6.0 6.0 6.0 6.0 6.0 6.0 6.0 
Light Liquid Paraffin 
5.0 5.0 5.0 5.0 5.0 5.0 5.0 
Silicone 556 (phenyl trimethicone) 
2.0 2.0 2.0 2.0 2.0 2.0 2.0 
ZnO Paste * 7.23 
7.23 
7.23 
7.23 
-- -- -- 
Finsolv TN (C12-15 alkyl benzoate) 
1.0 1.0 1.0 1.0 1.0 1.0 1.0 
Propylparaben 0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
0.05 
Parsol MCX (octyl methoxycinnamate) 
-- -- 5.0 5.0 5.0 5.0 -- 
(Polyethylene 617 (polyethylene) 
-- 2.0 -- 2.0 2.0 -- 1.25 
Isopropyl Palmitate 21.0 
19.0 
16.0 
14.0 
21.0 
23.0 
23.0 
Silicone 344 (cyclomethicone) 
3.0 3.0 3.0 3.0 3.0 3.0 3.0 
TOTAL 100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
Sun Protection Factor (SPF) 
4.7 4.6 17.6 
31.7 
9.7 5.9 1.3 
* Zinc Oxide (ZnO) Paste 
Finex Zinc oxide 5.0 
Light Liquid Paraffin 
1.5 
Antaron V216 (PVP/hexadecene 
0.06 
copolymer) 
Solulan P820 (PPG-20 lanolin alcohol ether) 
0.175 
Lecithin 0.12 
PCL Liquid (cetearyl octanoate) 
0.375 
7.23 
__________________________________________________________________________ 
The sun protection factor (SPF) for each formulation was determined by the 
method described in the Australian Standard AS 2604-1986, "Sunscreen 
Products --Evaluation and Classification" (Standards Association of 
Australia, 1986). 
The SPF's of the various formulations are set forth in Table II for 
comparison purposes. 
TABLE II 
______________________________________ 
% Octyl 
Methoxy- % Poly- % 
Formulation cinnamate ethylene ZnO SPF 
______________________________________ 
I -- -- 5 4.7 
II -- 2 5 4.6 
III 5 -- 5 17.6 
IV 5 2 5 31.7 
V 5 2 -- 9.7 
VI 5 -- -- 5.9 
VII -- 1.25 -- 1.3 
______________________________________ 
The synergistic effect of the polyethylene on the SPF of the octyl 
methoxycinnamate and ZnO components of the composition is apparent from 
the data set forth in Table II. It would be expected that the SPF of 
Formulation IV (containing 2% polyethylene, 5% ZnO and 5% octyl 
methoxycinnamate) would be the sum of the SPF's of Formulation V 
(containing 2% polyethylene and 5% octyl methoxycinnamate) and Formulation 
II (containing 2% polyethylene and 5% ZnO), i.e., 4.6+9.7=14.3. However, 
the actual measured SPF of Formulation IV is 31.7; more than twice the 
expected value. It should be further noted that the SPF value for 
polyethylene alone is only 1.3, thereby evidencing that it has little, if 
any, intrinsic sun protection properties, but that it does contribute 
synergistically to compositions containing organic sunscreen agents and 
ZnO of the requisite particle size. 
EXAMPLE 2 
The procedure of Example 1 was repeated to prepare formulations containing 
the ingredients set forth in Table III below. 
TABEL III 
______________________________________ 
% Octyl % Microfine 
Formu- Methoxy- % Poly- Zinc Oxide 
lation cinnamate ethylene Z-Cote.sup.a 
Microsol Z.sup.b 
SPF 
______________________________________ 
A -- 2.0 5.0 -- 3.7 
B 5.0 2.0 5.0 -- 33.1 
C -- -- 5.0 -- 3.8 
D -- 2.0 -- 5.0 3.0 
E 5.0 2.0 -- 5.0 34.3 
F -- -- -- 5.0 3.7 
______________________________________ 
.sup.a SunSmart, Inc., New York 
.sup.b Micronisers Pty. Ltd., Australia 
Similarly to the results set forth in Table II, the synergistic effect of 
the polyethylene on the SPF of the octyl methoxycinnamate and ZnO 
components of the compositions is apparent from the data set forth in 
Table III. The SPF values for Formulations B (33.1) and E (34.3) are much 
more than the expected values. 
EXAMPLE 3 
The procedure of Example 1 was repeated to prepare the formulations set 
forth in Table IV below. 
TABLE IV 
______________________________________ 
% Octyl % 
Formu- % Poly- % Methoxy- 
% Padi- 
Octo- 
lation ethylene Zno cinnamate 
mate O.sup.a 
crylene 
SPF 
______________________________________ 
1 2 -- -- 5.0 -- 12.7 
2 2 5.0 -- 5.0 -- 27.0 
3 2 -- -- -- 5.0 7.9 
4 2 5.0 -- -- 5.0 16.2 
5 2 -- 5.0 -- -- 9.6 
6 2 5.0 5.0 -- -- 31.7 
______________________________________ 
.sup.a Octyl dimethyl PABA 
Again the SPF values for Formulations 2, 4 and 6 are significantly higher 
than expected. 
EXAMPLE 4 
The procedure of Example 1 was repeated to prepare the formulations 
containing the ingredients set forth in Table V below. 
TABLE V 
______________________________________ 
% Microfine 
% Microfine % Poly- 
Zinc Oxide Titanium Dioxide 
ethylene SPF 
______________________________________ 
5 -- -- 4.7 
5 2 -- 4.6 
-- 5 -- 10.0 
-- 5 2 23.0 
5 5 2 26.0 
5 5 -- 21.0 
______________________________________ 
As apparent from the results set forth in Table V, there is no synergy in 
the system containing microfine titanium dioxide and zinc oxide and 
polyethylene. 
It will be understood by those skilled in the art that the water-in-oil 
emulsion compositions of the invention may be formulated in cream, lotion, 
ointment or other form. 
Creams may be prepared, e.g., by employing different proportions of Arlacel 
481 and Arlacel 989 in the example. Thus, if Arlacel 481 (5%) and Arlacel 
989 (2%) are employed in Example 1, the resultant products are creams. 
The products produced by the method of Example 1 are lotions.