Phase stable multiple emulsion compositions

Details Phase stable multiple emulsion compositions Phase stable multiple emulsion compositions

1999-10-22

2001-05-22

Page, Thurman K. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Cosmetic, antiperspirant, dentifrice

C424S070100, C424S070110, C424S070120, C424S070130, C424S070140, C424S070190, C424S070210, C424S070220, C424S070230

Reexamination Certificate

active

06235298

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to liquid surfactant composition, e.g., liquid shower gels or liquid shampoos, comprising multiple emulsions. In particular, this invention relates to such compositions which may comprise high levels of surfactants: microscopically these compositions maintain multiple emulsion droplet integrity while macroscopically there is little or no phase separation.
BACKGROUND OF THE INVENTION
Multiple emulsion systems (broadly defined as systems in which water/oil and oil/water emulsion co-exist) are very valuable because these permit incorporation and enhanced delivery of benefit agents. Thus, these multiple emulsions have been used for many years, for example, in cosmetic and pharmaceutical areas to deliver cosmetic or pharmacological benefit agents (see for Example, U.S. Pat. No. 5,306,498 to Vesperini; or U.S. Pat. No. 5,567,426 to Nadaud et al.). The level of high HLB (>10) cleansing surfactant in almost all the cosmetic and pharmaceutical art referred to above is below 5% by wt. of the compositions. If the high HLB surfactant concentration in the above referred to art were significantly increased, the multiple emulsion droplets would become less and less stable, leading to phase separation. In U.S. Pat. Nos. 5,656,280 and 5,589,177 to Herb et al, the multiple emulsion droplets are stabilized in high levels of conditioning surfactants which form lamellar liquid crystals.
In applicants' copending application entitled “Stable Multiple Emulsion Composition” and filed on same date as the subject application, applicants found multiple emulsion systems which employed surfactant systems which were in an isotropic phase which at the same time did not rapidly destabilize the multiple emulsion droplets. It is particularly advantageous to use surfactant systems which are isotropic because these systems provide improved foam/lather and because they can be formed using a much wider range of surfactant.
While the final compositions of that invention are microscopically stable in that the multiple emulsion droplets maintain their integrity, they phase separate over time. In the subject invention, the compositions do not phase separate due to specific selection of an external surfactant system in combination with a stabilizing natural gum polymer which forms a gelled external aqueous phase with a relatively high concentration of surfactant. Compositions which employ similar technology (i.e. gelled external aqueous phase) are described in U.S. Pat. No. 5,306,498 to Vesperini, U.S. Pat. No. 4,083,798 to Versteeg, U.S. Pat. No. 5,332,595 to Gaonkar, U.S. Pat. Nos. 5,576,064 and 5,656,263 both to Fructus, and U.S. Pat. No. 5,567,426 to Nadaud. In all of these aforementioned compositions, however, the level of high HLB external surfactant was in one case only 5% and in most cases zero.
It is the object of this invention to provide a gelled isotropic external surfactant phase which contains high levels of surfactant where the integrity of the multiple emulsion droplet is maintained and the composition does not phase separate.
BRIEF SUMMARY OF THE INVENTION
Unexpectedly, applicants have now found that through specific selection of an external surfactant system in combination with a stabilizing natural gum polymer which forms a gelled external aqueous phase with a relatively high concentration of surfactant, a multiple emulsion system is formed which allows delivery of desirable benefit agent(s) while simultaneously maintaining both the integrity of the multiple emulsion droplets and physical stability of the composition (i.e. the bottom clear layer formed due to phase separation should be less than 20 volume percent of the total volume of the sample for a period of at least 45 days at room temperature.)
Specifically, the invention relates to the selection of natural gum polymers and surfactant(s) or combinations of surfactants which form a gelled external phase for the multiple emulsions described above.
More specifically, the invention comprises a water-in-oil-in-water (W
1
-O-W
2
) multiple emulsion wherein the water-in-oil (W
1
/O) emulsion itself comprises an internal aqueous phase (W
1
) which contains a solute and optional surfactant; an oil phase O (an oil combined with a low HLB emulsifier, e.g., emulsifier with HLB less than 10) surrounding the internal aqueous phase; and a topically active compound which may be in either the aqueous W
1
or in O. The W
1
O phase is surrounded by an external aqueous isotropic phase (W
2
) containing a high level of cleansing surfactant, optional topically active compound (which may be same or different as first optional topically active compound), optional solute (It should be understood that some solute will almost always be present in the surfactant or will be formed when adjusting pH) and a stabilizing natural gum polymer. It is a criticality of the invention that the natural gum stabilizer and the selected surfactant(s) form a gel. As in the copending application, another criticality is that the surfactant phase W
2
must not contain an anionic surfactant with an amido group. Furthermore, the W
2
surfactant phase must be isotropic. The isotropic phase in turn is formed by selection of a specific surfactant system which must not contain an anionic surfactant with an amido group.
The oil in the O phase (e.g., light mineral oil, hexadecane, octyl palmitate) should preferably not comprise (1) more than 50% unsaturated compounds; or (2) should not be a volatile silicone (e.g., a silicone having viscosity of 10 centistokes or less).
As noted above, the invention can be distinguished from prior art U.S. Pat. No. No. 5,306,498 (Vesperini) U.S. Pat. No. 4,083,798 (Versteeg) U.S. Pat. No. 5,332,595 (Gaonkar), 5,576,064 and U.S. Pat. No. 5,656,263 (Fructus), and U.S. Pat. No. 5,567,426 (Nadaud) because our invention uses surfactant levels of 10.5% or greater whereas the aforementioned compositions use levels of only 0-5% external surfactant.
In particular, the invention comprises a W
1
-O-W
2
multiple emulsion composition comprising:
(1) about 1% to 99% by wt. of the composition, preferably 2% to 90% by wt., more preferably 5% to 80%, more preferably 5 to 50% of a W
1
/O emulsion comprising;
(a) about 1% to 99% of said emulsion of an internal aqueous phase comprising (i) water; (ii) 0.01 to 30% solute; and (iii) 0 to 30% surfactant;
(b) about 0.5% to about 99%, preferably 1 to 80% of the emulsion of an oil phase surrounding said internal aqueous phase comprising a non-volatile silicone compound, a volatile hydrocarbon compound, a non-volatile hydrocarbon compound or a mixture thereof;
(c) about 0.1 to 20%, preferably 1 to 15%, more preferably 1.5 to 15% of a low HLB emulsifier (e.g., having HLB under 10); and
(d) a topically effective amount (e.g., 0.01 to 40%, preferably 0.05 to 15% by wt.) of a first topically active compound which may be found in either aqueous phase (a) and/or oil phase (b); and
(2) about 1 to 99% by wt., preferably 20 to 95% by wt. of an external isotropic aqueous phase W
2
comprising non-amido anionic and/or other surfactants. The composition contains all non-amido anionic or all amphoteric surfactant, or combinations of the two. The surfactant typically will comprise 2-80% of the aqueous phase and 0.01 to 10% stabilizing natural gum polymer. The composition optionally contains a second topically effective compound, typically 0-40% by wt. of the external phase to perform a function identical to, similar to or different from the first topically active compound and solute. It is preferred that in systems where the external surfactant W2 is comprised entirely of or contains a majority of anionic surfactant, that a nonionic gum polymer is used. Conversely, in systems where the external surfactant W2 is comprised entirely of or contains a majority of amphoteric surfactant, it is preferred that an anionic gum polymer is used.
The W
1
-O-W
2
multiple emulsion compositions are physically stable (e.g., typically they will not phase separate at room temperature for at least 45 days and exhib

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