Sunscreen composition

Liquefiable powder compositions are disclosed for the delivery of topical sunscreens. In particular, microporous cellulosic powders, such as cellulose acetates or nitrates, are disclosed as high liquid content vehicles for the delivery of liquid sunscreen preparations dissolved or dispersed in a liquid carrier. The resulting powders permit the application of the sunscreen preparation by simply rubbing or otherwise applying the formulation onto the skin in such a manner that the powder liquefies and appears to vanish. Upon application, the frangible liquid loaded cellulosic powders break up into minute particles that adhere well to the skin and do not pass easily beyond the initial layers of the skin, but do permit the slow release of the sunscreen agent.

BACKGROUND OF THE INVENTION 
The technical field of this invention is the topical application of 
personal care agents and, in Particular, methods and compositions for 
topical application of sunscreens. 
In recent years, the public has become increasingly aware of the harmful 
effects of overexposure to the sun, Particularly the ultraviolet 
components of sunlight. Painful sunburn is a common result of short-term 
overexposure. Additionally, wrinkling and premature aging of the skin, and 
even cancer, can result from chronic overexposure. 
Sunscreens typically operate by absorbing ultraviolet radiation. 
Compositions useful as sunscreens should disperse easily onto the skin, 
closely adhere to the skin, resist penetration through the skin, and 
resist shedding by perspiration or by immersion in fresh or salt water. 
Unfortunately, most sunscreens do not fully satisfy these requirements in 
terms of durability and efficacy. Often, sunscreen compositions are 
quickly shed from the skin or absorbed into the lower layers of the skin 
where their radiation blocking activity is markedly reduced. 
There exists a need for better sunscreen compositions, particularly for 
economical, long-term Protection from the harmful effects of ultraviolet 
radiation. 
SUMMARY OF THE INVENTION 
Liquefiable powder compositions are disclosed for the delivery of topical 
sunscreens. In particular, microporous cellulosic powders, such as 
cellulose acetates or nitrates, are disclosed as high-liquid content 
vehicles for the delivery of sunscreen preparations dissolved or dispersed 
in a liquid carrier. The resulting powders permit the application of the 
sunscreen preparation by simply rubbing, or otherwise applying, the 
composition to the skin in such a manner that the powder liquefies and 
appears to vanish. Upon application, the frangible liquid-loaded, 
cellulosic powders break up into minute particles that adhere well to the 
skin and do not pass easily beyond the initial layers of the skin, but do 
permit the slow release of the sunscreen agent. 
Details of the formation of cellulosic powders can be found in the 
above-referenced parent application, U.S. Ser. No. 358,690, filed May 30, 
1989, now U.S. Pat. No. 5,000,947 and a commonly-owned, copending 
application entitled "Process For Producing Liquid-Loaded Powders", by 
Larry D. Nichols and John F. Cline, filed contemporaneously herewith, both 
of which are incorporated herein by reference. A preferred polymer 
liquid-loadable powder includes microporous cellulose triacetate prepared 
by the method of the above application, Attorney Docket No. MOE-014, 
entitled "Process For Producing Liquid-Loaded Powders". 
In one technique, the liquefiable powders are formed by dissolving a 
cellulosic polymer and a pore-forming liquid in a volatile, polar solvent 
(e.g., a low molecular weight halogenated hydrocarbon, ester or diester) 
and then dispersively evaporating the solution, for example, by spray 
drying. Suitable volatile solvents for cellulosic polymers include 
methylene chloride, acetone, ethyl acetate, ethyl carbonate, methyl 
formate and the like. Methylene chloride is a preferred solvent when the 
cellulosic polymer is cellulose triacetate. Alternatively, other solvents, 
such as formic acid or the like, can be used and the resulting solution 
can be sprayed into a non-solvent such as methanol where the powder 
particles are then recovered by filtration and rinsing. The active agent 
can be incorporated into the solvent or introduced by liquid phase 
substitution after the powder is formed. 
The cellulosic powders useful in the present invention can range from about 
one to about 500 micrometers in average diameter, preferably from about 5 
to about 100 micrometers in average diameter, and typically are roughly 
microspherical in shape. They are further characterized by being 
microporous with interconnecting pores ranging in size from about one to 
about 500 nanometers or greater and are capable of holding liquid payloads 
of active agents. The cellulosic powder can be formed from cellulosic 
polymers chosen from the group of cellulose acetates, cellulose butyrates, 
cellulose nitrates, cellulose propionates, ethyl celluloses and discrete 
or molecular mixtures thereof. One preferred cellulosic powder is a 
polymeric powder of cellulose triacetate, having a (dry) acetyl content 
greater than about 42 percent. The liquid content of the cellulosic 
powders of the present invention can range from about 50 percent to about 
95 percent by weight. 
Compositions made in accordance with the present invention permit the 
delivery of effective concentrations of active sunscreen ingredients 
without many of the problems normally associated with liquids and oils. By 
assisting in the distribution of sunscreen agents uniformly over the skin 
and retarding the penetration of the sunscreen agents into the lower 
layers of the skin, the compositions of the invention enhance efficacy, 
improve economy and reduce the risk of adverse reactions. 
Sunscreens which can be used in the practice of the invention include 
oxybenzone, amyl-p-dimethylaminobenzoate, homomethyl salicylate, octyl 
salicylate, mono-p-aminobenzoate, octyl-methoxycinnamate, 2-ethoxy 
ethyl-p-methoxycinnamate as well as derivatives and mixtures thereof. Such 
sunscreens can be formulated as solutions or dispersions in oils, such as 
mineral oil or silicone oil, or in emollients, such as isopropyl 
myristates or palmitates, with or without additional volatile solvents, 
such as ethanol, isopropyl alcohol or other alcohols. 
In one embodiment, the sunscreen agent can be incorporated into frangible, 
cellulosic microbeads or other powder forms and then formulated into a 
cream or emulsion type vehicle by mixture with a liquid base. 
Alternatively, the compositions can be formulated as loose powders, 
compacted into cakes, or blended with binders, and shaped into bars or 
application sticks. 
Suitable liquid bases for cream or lotion type embodiments include water, 
oils and moisturizing agents, such as glycerin or aloe vera gels. 
Additional ingredients can include stearic acid, silicone liquids, 
triethanolamine, petrolatum, cetyl alcohol, carbomers, and the like. 
In the compacted cake embodiments, the liquid loaded powders can be 
compacted to packing densities ranging from about 55 percent to about 75 
percent, more preferably from about 60 percent to about 70 percent of the 
void-free density of the combined materials to yield cakes that are dry 
and firm and yet readily permit transfer of the formulation to the skin by 
finger or brush. 
Such compacted cakes can be obtained by applying a pressure ranging from 
about 50 to about 80 PSI to a cellulosic powder which has been 
appropriately loaded with a liquid payload of the active agent. In the 
absence of other additives, the resulting shaped articles have a compacted 
density ranging from about 0.55 to about 0.75 gm/cc. 
Sticks or bars incorporating liquefiable powders with active agent payloads 
can be made by a variety of techniques. For example, sticks can be 
formulated by compounding a liquefiable powder with fatty alcohols, fatty 
acids, and/or salts of fatty acid anions with metallic or alkanolamine 
cations to produce a stick having a soap as the binding agent. 
Alternatively, stick compositions can be formed by compounding a 
liquefiable powder with soft, water-soluble polymers, such as polyethylene 
glycols or polypropylene glycols, to produce a stick having a soluble wax 
as the binding agent. Sticks can also be made up by compounding a 
liquefiable powder with silicones or with blends of liquids and solids, 
such as salts and/or propylene glycols, to produce sticks having a thick 
or partially-solidified slurry as the binding agent. In yet another 
approach, sticks can be formed by compounding a liquefiable powder with a 
fusible wax, including fatty esters, silicone waxes, polyglycol waxes and 
aliphatic waxes, and then applying heat and pressure to produce sticks 
having a wax as the binding agent. 
The above binding agents can be introduced directly, or as payload in a 
second portion of liquefiable powder to be blended with that carrying the 
active ingredient. Other methods of stick production will readily occur to 
those skilled in the art. 
Regardless of the embodiment, various additives can be mixed with the 
liquid-loaded Particles (or liquid base) including, for example, talc, 
cornstarch, waxes, silicones, analgesics, cosmetics, fragrances, 
lubricants, emollients, moisturizers, medications and other personal care 
agents, colorants, pearlescent agents, and mixtures of such additives. 
The invention will next be described in connection with certain exemplary 
methods and compositions. However, it should be clear that various 
additions, subtractions and changes can be made by those skilled in the 
art without departing from the spirit or scope of the invention. For 
example, various additives can be mixed together with the sunscreen loaded 
powder particles of the invention, including, for example, talc, 
cornstarch, waxes, silicones, cosmetics, fragrances, lubricants, 
emollients, moisturizers, medications and other personal care agents, as 
well as colorants, pearlescent agents, and mixtures of such additives. 
In some applications, it may also be preferable to include a quantity of a 
dry cellulosic Powder (e.g., less than 50 percent of the total cellulosic 
components) to provide additional structural integrity to the composition. 
The term "dry cellulosic powder" is used herein to describe powders whose 
internal pores are liquid-free or have a liquid content of less than 50 
percent.

DETAILED DESCRIPTION 
The examples below illustrate the preparation of liquefiable sunscreen 
loaded powders. 
EXAMPLE 1 
A liquefiable powder was prepared by spray evaporative drying. A liquid 
porogen solution was prepared from 8.15 parts by weight of Parsol MCX 
(octyl methoxycinnamate, Givaudan Corporation, Clifton, N.J.), 5.45 parts 
of Sunarome WMD (octyl salicylate, Felton International, Inc., Brooklyn, 
N.Y.) and 8.5 parts of Dow Corning 55E silicone fluid. 34.79 parts of CTA 
and 400 parts of said porogen were then dissolved in 3478.21 parts of 
methylene chloride by moderate stirring for 4 hours. This solution was 
sprayed at 1000 PSI from a 0.0135" nozzle downward into a tower 100 cm in 
diameter and 300 cm tall through which 1250 liters per minute of 
solvent-free air was passing from top to bottom. 
The resulting evaporatively-formed, liquid-containing cellulose triacetate 
powder was collected on a fabric filter spanning the bottom of the tower, 
and the solvent-laden air was passed through carbon beds to collect 
solvent vapors. 
The product was transferred from the filter into a steel tray and left 
exposed as a 1 cm layer in a ventilated hood for 15 minutes to remove 
residual solvent. Analysis showed 12.7 percent sunscreen formulation, 79.3 
percent silicone fluid, and 8.0 percent cellulose triacetate, with less 
than ppm of methylene chloride. 
EXAMPLE 2 
35 gr of CTA was dissolved in 465.2 gr methylene chloride. A mixture of 
32.6 gr Parsol MCX, 21.8 gr Sunarome WMO, and 340.0 gr phenyltrimethicone 
(an occlusive-type moisturizing agent which prevents moisture from leaving 
the skin surface) were dissolved in 3016 gr methylene chloride, and then 
the two solutions were mixed. The resulting lacquer was sprayed at 1175 
psi from a 0.0135 inch diameter, single fluid pressure/pneumatic nozzle 
downwardly into a tower through which 55 cfm air was passing from top to 
bottom. Nozzle diameter was 0.0135 inch. The temperature at the top of the 
tower measured 30.5.degree. C. and the base at 17.3.degree. C., with a 
relative humidity of about 40 to 60 percent or less. Mean particle size 
was 38.1 microns with 90% less than 78.9 microns. 
EXAMPLE 3 
200 gr of commercial suntan oil (sun protection Factor 6) was blended with 
2877 gr of methylene chloride and 35 gr of CTA dissolved in a further 465 
gr of methylene chloride. The resulting lacquers were mixed and spray 
dried under the conditions described in Example 2. The resulting powder 
was dermatologically tested for efficacy against 100 gr of the commercial 
blend alone and was found to be equally effective when 117.8 mg of product 
(100 mg active) was applied to the skin. The powder form blended into the 
skin very easily, had none of the disadvantages associated with sun oil, 
and remained on the skin for a considerable period of time. 
EXAMPLE 4 
201.1 gr of commercial suntan oil (sun protection factor 4) and 2877 gr of 
methylene chloride were mixed--35 gr of CTA was dissolved in a further 465 
gr of methylene chloride. Both solutions were mixed, and the resultant 
lacquer spray dried under the conditions described in Example 2. 
Efficacy tests on 100 mg of the commercial oil and 117.6 mg of powder (100 
mg active) gave readings of true SPF values at 3.7 and 4.1, respectively. 
It will be understood that the above description describes only several 
embodiments of the present invention and that other embodiments are within 
the spirit and scope of the present invention. Hence, the above 
description is provided by way of illustration and not by way of 
limitation. The invention is further defined as set forth in the claims.