Sunblock composition suitable for sensitive skin areas

A topical sunblock formulation for shielding skin, particularly sensitive skin areas, such as around the eyes, comprising an emulsion of micronized titanium dioxide and an organic chemical sunscreen agent encapsuled in transparent plastic spheres to give a sunblock formulation free of the negative qualities of excessive whitening due to the former and skin irritation due to the latter.

BACKGROUND OF THE INVENTION 
There has been increasing concern over the upsurge in skin cancer in the 
United States due to excessive exposure to the sun. In particular the 
amount of UVA exposure (320-400 nm of the solar spectrum band) is 
increasing since most sunscreens effectively only block UVB radiation 
(290-320 nm). Users continue to stay in the sun for excessive periods 
without seeing any immediate harmful effects of UVA radiation which are 
more long term in nature. 
As used in the specification, the term UV covers the ultraviolet region 
(290-400 nanometers (nm)) of the solar spectrum. The term infrared (IR) 
covers the range above 760 nm. 
The goal of a successful sunscreen agent must be to protect the user from 
both UVA and UVB radiation with minimal side effects. This has been a 
particularly difficult problem when attempting to protect sensitive areas, 
such as the area around the eyes or lips. While chemical sunscreen 
compositions in the form of creams and lotions are known, they are 
irritating when applied to such sensitive areas. If the user avoids too 
close a contact with such areas, needed protection is not secured. 
In addition to chemical sunscreens, the use of physical sunscreens is known 
in the art. Such sunscreens comprise particles of relatively 
physiolocially inert sunblocks or sunscreens, such as kaolin, talc, zinc 
oxide and titanium dioxide suspended in a cream or lotion. However, such 
physical sunblocks have significant disadvantages. They in general exhibit 
lower effectiveness in absorbing UV radiation as compared to many chemical 
sunblocks. When their concentration is increased to promote greater 
effectiveness, an undesirable white layer appears on the skin which most 
users find objectionable. When using such physical sunscreen compositions 
to protect the eyes, one may assume a "racoon like" appearance clearly in 
conflict with the attractive tanned look sought by the average person. 
Recent modifications of conventional chemical and physical sunscreens are 
disclosed in U.S. Pat. No. 5,223,250 to Mitchell and Mitchnick, the 
relevant portions of which are hereby incorporated by reference in this 
specification. Column 3 of this patent describes the use of "micronized" 
titanium dioxide or "large surface area" particles having smaller particle 
diameters than conventional titanium dioxide. Such micronized titanium 
dioxide particles are smoother and less occlusive and thus provide a more 
cosmetically acceptable formulation. However, they still exhibit a low 
sunblock effectiveness. U.S. Pat. No. 5,223,250 also discloses an 
alternative sunblock formulation wherein a chemical UV additive capable of 
absorbing ultraviolet light radiation is incorporated into commercially 
available small plastic particles (0.01-100 microns) during their 
formation (column 10 line 42 through column 11 line 47). 
SUMMARY OF THE INVENTION 
The present invention provides a new cosmetically acceptable sunblock 
formulation comprising the best qualities of both physical and chemical 
sunblocks. More specifically, it comprises an emulsion comprising in 
combination: 
(1) a minor quantity of micronized titanium dioxide, and 
(2) a minor quantity of an organic chemical sunscreen agent, such as a 
cinnamate, encapsulated in plastic particles (0.01-100 microns in 
diameter). 
The quantity of titanium dioxide is no greater than 4.0 wt % to avoid the 
whitening appearance which occurs at higher concentrations. However, at 
such levels it is not capable of providing sufficient sunblock effect to 
reach SPF 15 level. The supplementary presence of the encapsulated organic 
chemical sunscreen agent provides the added sunscreen capable to reach 
this necessary level without causing irritation to sensitive areas due to 
its encapsulation.

DETAILED DESCRIPTION OF THE INVENTION 
The broad and preferred ranges of key components are as follows, all 
percentages being on a weight percent basis. 
Component A--dispersion of micronized titanium dioxide in water, where the 
former is preferably 35 to 45 wt % of component A. 
Component B--dispersion of encapsulated organic sunscreen, such as octyl 
methoxycinnamate, in water along with other ingredients to serve as the 
emulsifying agent and the composition of the encapsulating agent. The 
organic sunscreen agent comprises 20 to 30, preferably 21.5 to 25 wt % of 
component B. 
TABLE I 
______________________________________ 
Relative Quantity in Final Composition, wt % 
Broad Range 
Preferred Range 
______________________________________ 
Component A 1.6-13.3 1.6-11.6 
Component B 4.5-34 13.6-18.0. 
______________________________________ 
TABLE II 
______________________________________ 
Active Ingredients 
Relative concentrations of titanium dioxide and organic 
sunscreen (octyl methoxycinnamate) in the final product 
formulation are as follows: 
Broad Range 
Preferred Range 
______________________________________ 
Titanium dioxide 
0.5-4.0 wt % 
0.5-3.5 wt % 
Size, microns 0.03-0.08 0.03-0.05 
Organic sunscreen agent 
1.0-7.5 wt % 
3.0-4.0 wt % 
______________________________________ 
The micronized titanium dioxide have significantly smaller diameters than 
conventional particles (diameters above 0.1 microns). It is typically 
added in the form of a dispersion of titanium dioxide in water having the 
compositions described above. 
The micronized titanium dioxide provides UVA and infrared protection by 
absorption and scattering. However, its concentration in the final 
formulation must not exceed 4 wt % in order to avoid the undesirable 
whitening effect. 
The encapsulated organic chemical sunscreen component is made by the 
process described in U.S. Pat. No. 5,223,250 which is hereby incorporated 
by reference (particularly columns 10 and 11). The sunscreen is 
incorporated into plastic particles during their formation. Suitable 
plastics include acrylics (methyl methacrylate), styrene polymers and 
copolymers with acrylics; styrene acrylonitrile polymers, 
polyvinylpyrrolidone (PVP), polycarbonates, methylpentene polymers, 
terpolymers of acrylonitrile, butadiene, styrene and allyl diglycol 
carbonate, etc. Particularly preferred are polyvinylpyrrolidone (PVP). 
Any of the sunscreen chemical agents approved by the U.S. Government can be 
used in the present formulations. Typical examples of the latter are: 
(1) Para-aminobenzoic acid (PABA); 
(2) PABA esters, such as glyceryl PABA, amyldimethyl PABA and octyldimethyl 
PABA; 
(3) Cinnamates, such as octyl methoxycinnamate, and cinoxate. 
(4) Benzophenones, such as oxybenzone and sulisobenzone. 
(5) Salicylates, such as octyl salicylate. 
(6) Anthranilates, such as methyl anthranilate. 
As will be further described as follows, the present invention initially 
proposes two phases--a water phase and an oil phase. The water phase will 
contain most or all of the water soluble ingredients, including the 
micronized titanium dioxide and organic chemical sunscreen agent, and the 
oil phase the oil soluble components of the present formulation, such as 
emollients, antioxidants, preservatives. The two phases are mixed at 
temperatures of 60.degree.-90.degree. C., preferably 80.degree.-85.degree. 
C. in the presence of a suitable emulsifying agent to give a stable 
suspension of the two liquid phases which normally do not dissolve in each 
other. Other physical sunscreens, such as zinc oxide, are difficult to 
formulate and can lead to emulsion instability. 
Suitable emulsifying agents for the practice of the present invention are: 
(1) Quaternary ammonium compounds, such as Quaternium 22, and stearakonium 
chloride; 
(2) Polyhydric alcohol esters and ethers, such as cetyl alcohol, isopropyl 
lanolate, and polyglycerol oleates and stearates; 
(3) Sorbitan oleates and laurates; 
(4) Acrylates, such as C.sub.10-30 alkyl acrylate polymers (sold under the 
Carbopol trademark); 
(5) Polyglycerol pentastearate alone or in combination with sodium stearoyl 
lactylate (NIKKOMULESE). 
As an alternative to first completely forming a water phase with all 
ingredients and an oil phase with all its ingredients it may be desirable 
to form the emulsion and then add some components to it with a further 
mixing and/or heating step. 
In addition to the key ingredients--encapsulated chemical organic sunscreen 
agent, micronized titanium dioxide, emulsifying agent and water, the 
following components typically found in sunblock formulations may be 
present. 
Sequestering agents, such as trisodium EDTA (ethylene diamine tetraacetic 
acid) and trisodium phosphate. 
Preservatives, such as ethyl, methyl, butyl, propyl paraben, 
phenoxyethanol, and diazolidinyl urea. 
Humectants, such as 1,3 butylene glycol, and propylene glycol. 
Soothing agents, such as extracts of chamomile, eurphasia, and witch hazel. 
Anti-irritants, such as alpha bisabolol, and allantoin. 
Firming agents, such as actiphyte of witch hazel, heather or butcher's 
broom, hydrolyzed elastin, or collagen amino acids. 
Emollients, such as squalene, polydecene, or stearyl alcohol. 
These are normally added to the oil phase. 
In general, each class of the above was less than 5 wt %, preferably less 
than 3 wt % of the overall final composition. Preservative agents are 
normally less than 1 wt % of the composition. 
GENERAL PROCESS 
The oil dispersible ingredients are combined in a suitable vessel and 
heated to 80.degree.-85.degree. C. while mixing with a Lightnin mixer, 
sidesweep mixer or other suitable mixer of low to medium shear. The oil 
dispersible ingredients may, for example, consist of polydecene, jojoba 
esters, squalene, vitamin E acetate, dimethicone ethylparaben and 
triethanolamene. 
The water phase ingredients are combined in a separate vessel. For example, 
first the acrylates/C.sub.10-30 alkyl acrylate crosspolymer and xanthan 
gum (which are the gellants) are sprinkled slowly into the water with 
Lightnin mixing or other source of medium speed mixing while heating to a 
temperature of 80.degree.-85.degree. C. When the gellants are completely 
dispersed in the water, the other water dispersible ingredients are added 
with mixing. The other water dispersible ingredients may consist of the 
botanical extracts, sequestering agents and the active agents, namely, (1) 
the dispersion of encapsulated organic sunscreen agent, such as octyl 
methoxycinnamate, and (2) the dispersion of micronized titanium dioxide. 
The oil phase at temperatures of 80.degree.-85.degree. C. is added to the 
water phase at temperatures of 80.degree.-85.degree. C. with higher shear 
mixing using a homogenizer, colloid mill, turbomixer or other suitable 
high shear mixer. 
The combined water and oil phases are mixed for about 20-30 minutes until 
emulsification is complete and then cooled to room temperature. 
SPECIFIC EMBODIMENT 
The following table illustrates a suitable dispersion of both micronized 
titanium dioxide in water (Component A) and encapsulated organic sunscreen 
agent, such as octyl methoxy cinnamate (Component B) used to prepare an 
emulsion ultimately containing about 3 wt % titanium dioxide and 3 wt % 
octyl methoxycinnamate. This emulsion also contains minor quantities of 
each the optional components described earlier--sequestering agents, 
preservatives, humectants, soothing agents, anti-irritants, emollients, 
and firming agents. Heat sequences occurred at 80.degree.-85.degree. C. 
while mixing in several steps until the requisite emulsification was 
complete. 
TABLE III 
______________________________________ 
Weight Per Cent 
(wt % in Final Product) 
in Dispersion 
______________________________________ 
Component A 
Titanium Dioxide 29 
Water 71 
Component B 
Octyl Methoxycinnamate 
21.5 
Water 53 
Balance of Dispersion 
25.5 
C.sub.18-38 Hydroxy Stearyl Stearate 
Dimethicone Copolyol Beeswax 
PEG 100 Stearate 
PEG Carnauba 
Sorbitan Tristearate 
PVP/Eicosene Copolymer. 
______________________________________ 
The sunblock formulation prepared as above had an SPF level of 15-18. It 
was non-irritating sunscreen to sensitive areas, such as the skin areas 
surrounding the eyes and did not impart a white appearance as is typical 
with titanium dioxide. 
As an emulsion, the present formulation also serves to moisturize the skin, 
diminish fine lines and wrinkles and firms the skin in the eye area. 
Having described the present invention, that which is sought to be 
protected is set forth in the following claims.