Title:  Phase stable multiple emulsion compositions

United States Patent:  6,235,298

Assignee:  Unilever Home & Personal Care USA (Greenwich, CT)

Filed:  October 22, 1999

W₁ -O-W₂ emulsions are disclosed in which the W₁ /O emulsion comprises an internal aqueous phase containing optional benefit agent and an oil phase surrounding it, and, around this is found an external isotropic aqueous phase comprising surfactant system and specific thickeners. Selection of surfactant system and thickener is critical to the multiple emulsion composition not phase separating.

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 (W₁ -O-W₂) multiple emulsion wherein the water-in-oil (W₁ /O) emulsion itself comprises an internal aqueous phase (W₁) 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 W₁ or in O. The W₁ O phase is surrounded by an external aqueous isotropic phase (W₂) 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 W₂ must not contain an anionic surfactant with an amido group. Furthermore, the W₂ 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 W₁ -O-W₂ 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 W₁ /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 W₂ 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 W₁ -O-W₂ multiple emulsion compositions are physically stable (e.g., typically they will not phase separate at room temperature for at least 45 days and exhibit exceptional esthetic and functional properties. The W₁ -O-W₂ multiple emulsion compositions are liquids or creams, and are capable of effectively delivering one or more topically active compounds to the skin or hair from a single composition.

Claim 1 of 30 Claims

What is claimed is:

1. A W₁ -O-W₂ multiple emulsion comprising:

(1) about 1% to 99% by wt. of the composition of a W₁ /O emulsion comprising;

(a) about 1% to 99% of said emulsion of an internal aqueous phase comprising (i) water; (ii) 0.01 to 30% by wt. emulsion solute; and (iii) optional surfactant;

(b) about 0.5% to about 99% of the emulsion of an oil phase surrounding said internal aqueous phase wherein said oil is selected from the group consisting of volatile hydrocarbon, nonvolatile hydrocarbons, nonvolatile silicones and mixtures thereof;

(c) about 0.1 to about 20% by wt. emulsion of a surfactant emulsifier selected from the group consisting of a silicon-free surfactant or surfactant blend having an HLB value of about 10 or less, an oil soluble silicon based surfactant, an oil-soluble polymeric surfactant and mixture thereof; and

(d) a topically effective amount (0.01-40%) of a first topically active compound, which may be found in either the aqueous phase (a), oil phase (b) or both; and

(2) about 1 to 99% by wt. of an external isotropic aqueous phase W₂ comprising:

(a) 2 to 80% by wt. aqueous phase of a surfactant phase which comprises a non-amido anionic, or a mixture of anionic and amphoteric in which 60% by weight or greater is the anionic surfactant;

(b) 0 to 60% by wt. of external phase of a second topically active compound;

(c) optional solute; and

(d) 0.01 to 10% of a nonionic natural gum stabilizer wherein the multiple emulsion droplets maintain their integrity and the multiple emulsion composition does not phase separate.

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