Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Reexamination Certificate
1999-10-29
2001-11-06
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
C424S060000, C424S078020, C424S078080, C424S400000, C424S401000
Reexamination Certificate
active
06312672
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is directed to sunscreen formulations comprising copolymers of isoprene, butadiene and or styrene which have improved water resistance. More particularly, this invention is directed to sunscreen formulations comprising liquid block copolymers having unsaturation only on the terminal blocks and methods of preparation thereof for use in sunscreen.
U.S. Pat. No. 5,204,090 describes waterproof sunscreens comprising a water insoluble film forming polymer. U.S. Pat. No. 5,653,965 describes film forming polymers for sunscreen spray. U.S. Pat. No. 5,487,886 describes acryl polymers for sunscreen formulations. U.S. Pat. No. 5,145,669 describes water proof sunscreens containing a crosslinked, neutralized terpolymer of maleic anhydride, a C1-C5 alkyl vinyl ether and a C12-C14 alpha-olefin monomer. U.S. Pat. No. 4,663,157 describes a copolymer of ethylene and acrylic acid for use in sunscreen compositions.
Sunscreen products are usually applied prior to activities such as bathing or sports. The product will remain effective after exposure to water and/or perspiration. The use of water insoluble active sunscreen ingredients is usually insufficient to provide adequate water resistance. A thickener also is required in such formulations. However, an effective method of accomplishing water resistance or water proofing of a sunscreen formula is to employ a water-insoluble substantive film forming resin. A Carbomer resin can provide thickening action. Typical materials for waterproofing sunscreen formulations are two resins which are copolymers of vinylpyrrolidone and long chain alkanes, C16 and C20. They are oil-soluble film forming polymers which have been used for some time by the cosmetic industry.
Therefore, it is the object of the present invention to provide new polymers for sunscreen formulations with improved properties.
SUMMARY OF THE INVENTION
Selectively hydrogenated low molecular weight polymers based on isoprene, butadiene and styrene are inherently immiscible in water and soluble in a wide range of organic materials including hydrocarbon and ester fluids. These polymers are useful in the preparation of sunscreen formulations containing complex mixtures of ingredients and lead to enhanced performance of active ingredients.
Sunscreen formulations rely on the presence of UV absorbers (typically organic compounds) in a mixture of organic and aqueous components. Because of the miscibility of many of the formulation components with water, UV protection may be diminished as a result of reintroduction of water following sunscreen application. This reintroduction may occur by any of several means, but two primary routes are by swimming and perspiration.
It is believed that the introduction of a non-aqueous, water-insoluble component to the sunscreen formulation would extend the effectiveness of the UV absorbers by preventing the removal upon the reintroduction of water.
The non-aqueous water-insoluble components of the present invention are polymers and copolymers of isoprene, butadiene and or styrene. Selectively hydrogenated isoprene-butadiene copolymers are preferred. The copolymers of the present invention, while providing no UV protection, have the additional advantage of being non-toxic and non-tacky when applied to skin. A choice of UV absorber may be suggested based on its solubility in the different formulation phases containing the copolymers of the present invention.
Hydrogenation of the copolymers of the present invention, selective or complete, provides oxidative stability. It is believed that the degree of hydrogenation is beneficial in the preparation of polymers with the desired refractive indices.
The invention provides sunscreen formulations which include polymers of conjugated dienes which may be partially, selectively or completely hydrogenated. The improved water resistant properties of the compositions of the invention may be controlled by controlling the size of the polymers.
In one embodiment of the invention, there is provided a sunscreen formulation comprising a copolymer of two different conjugated dienes. In this case, the first conjugated diene includes at least one relatively more substituted conjugated diene having at least five carbon atoms and the formula:
wherein R
1
-R
6
are each hydrogen or a hydrocarbyl group, provided that at least one of R
1
-R
6
is a hydrocarbyl group, and also provided that, after polymerization, the unsaturation of the polymerized conjugated diene of formula (1) has the formula:
wherein R
I
, R
II
, R
III
and R
IV
are each hydrogen or a hydrocarbyl group, provided that either both R
I
and R
II
are hydrocarbyl groups or both R
III
and R
IV
are hydrocarbyl groups.
The second conjugated diene in the sunscreen formulation of this embodiment includes at least one relatively less substituted conjugated diene which is different from the first conjugated diene and has at least four carbon atoms and the formula:
wherein R
7
-R
12
are each hydrogen or a hydrocarbyl group, provided that, after polymerization, the unsaturation of the polymerized conjugated diene of formula (3) has the formula:
wherein R
V
, R
VI
, R
VII
and R
VIII
are each hydrogen or a hydrocarbyl group, provided that one of R
V
or R
VI
is hydrogen, one of R
VII
or R
VIII
is hydrogen, and at least one of R
V
, R
VI
, R
VII
and R
VIII
is a hydrocarbyl group.
Following polymerization, the diene copolymer may be partially, selectively or completely hydrogenated.
In a preferred embodiment, the sunscreen formulation includes a polymer in which the first and second conjugated dienes are polymerized as a block copolymer including at least two alternating blocks:
(I)
x
-(B)
y
or (B)
y
-(I)
x
In this case, the block (I) includes at least one polymerized conjugated diene of formula (1), while the block (B) includes at least one polymerized conjugated diene of formula (3). In addition, x is the number of polymerized monomer units in block (I) and is at least 1, and y is the number of polymerized monomer units in block (B) and is at least 25. It should be understood throughout that x and y are defined relative to blocks in a linear block copolymer or blocks in an arm or segment of a branched or star-branched copolymer in which the arm or segment has substantially linear structure.
Preferably, in the block copolymers of this embodiment, x is from about 1 to about 600, and y is from about 30 to about 4,000, more preferably x is from about I to about 350, and y is from about 30 to about 2,800. While larger values for x and y are generally related to larger molecular weights, polymers which have multiple blocks and star-branched polymers typically will have molecular weights which are not well represented in the values of x and y for each block.
Alternatively, the sunscreen formulation includes the first and second conjugated dienes polymerized as a random copolymer. The sunscreen formulation may also include the first and second conjugated dienes polymerized as a branched or star-branched copolymer.
The copolymers useful according to this embodiment typically have a molecular weight of at least about 2,000. Preferably, the molecular weight of these polymers is from above 3,000 to about 200,000, more preferably from about 5,000 to about 35,000.
In the sunscreen formulations of the invention, the copolymer is preferably selectively hydrogenated. It is preferred that the unsaturation of formula (4) be substantially completely hydrogenated, thereby retaining substantially none of the original unsaturation of this type, while the unsaturation of formula (2) is substantially retained (i.e., the residual unsaturation after hydrogenation).
After the hydrogenation reaction, the iodine Number for the residual unsaturation of formula (2) is generally from about 50% to about 100% of the Iodine Number prior to the hydrogenation reaction. More preferably, after hydrogenation, the Iodine Number for the residual unsaturation of formula (2) is about 100% of the Iodine Number prior to the hydrogenation reaction.
After the hydrogenation reacti
Coolbaugh Thomas S.
Davis Sandra S.
Marlin, II John E.
Matthews Demetreos N.
Shirazi Fahimeh P.
Dodson Shelley A.
Exxon Mobil Chemical Patents Inc.
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