United States Patent:   6,117,915

Assignee:  Croda, Inc. (Parsippany, NJ)

Filed:  December 29, 1997

An oil-in-water emulsifier composition including between about 10 percent and about 70 percent by weight of a blend of mono- and diester phosphates of alkoxylated fatty alcohols containing between about 12 and 22 carbon atoms and alkoxylated with between about 1 and about 50 moles of an alkylene oxide selected from the group consisting of ethylene oxide, propylene oxide and mixtures thereof, wherein the mono- and diester ratio is between about 10:90 and about 90:10; and between about 90 percent and about 30 percent by weight of a blend of mono- and di-ester phosphates of fatty alcohols containing between 12 and 22 carbon atoms, wherein the mono- and diester ratio is between about 10:90 and about 90:10. Emulsifying waxes, oil-in-water emulsions and microemulsions, and topical compositions formulated therefrom are also disclosed.

SUMMARY OF THE INVENTION

It has now been discovered that blends of alkoxylated fatty alcohol mono- and diester phosphates with non-alkoxylated fatty alcohol mono- and diester phosphates produce oil-in-water emulsions and microemulsions possessing desirable emulsion stability. Therefore, in accordance with one embodiment of the present invention, there is provided an oil-in-water emulsifier composition consisting essentially of:

between about 10 percent and about 90 percent by weight of a blend of mono- and diester phosphates of alkoxylated fatty alcohols containing between about 12 and 22 carbon atoms and alkoxylated with between about 1 and about 50 moles of an alkylene oxide selected from the group consisting of ethylene oxide, propylene oxide and mixtures thereof, wherein the mono- and diester ratio is between about 10:90 and about 90:10; and

between about 90 percent and about 10 percent by weight of a blend of mono- and diester phosphates of fatty alcohols containing between 12 and 22 carbon atoms, wherein the mono- and diester ratio is between about 10:90 and about 90:10;

provided that the total amount of alkoxylation is within a range effective to provide both emulsion stability and oil deposition on keratin-containing substrates.

The emulsifier compositions of the present invention are preferably based on fatty alcohols containing between 14 and 20 carbon atoms, and more preferably are based on a blend of 16 and 18 carbon atom fatty alcohols. The emulsifier compositions of the present invention are preferably based on a ratio of alkoxylated fatty alcohol phosphate esters and non-alkoxylated fatty alcohol phosphate esters between about 20:80 and about 80:20, and more preferably between about 30:70 and about 70:30. The ratio of mono-esters to di-esters for both the alkoxylated and non-alkoxylated fatty alcohol phosphate esters is preferably between about 20:80 and 80:20 and more preferably between about 30:70 and about 70:30.

Emulsifier compositions of the present invention are suitable for formulation in emulsifying waxes based on fatty alcohols containing from 12 to 22 carbon atoms, which serve as thickening agents for the emulsion or microemulsion and provide a convenient form in which both the fatty alcohol thickener and the emulsifier can be incorporated into the emulsion or microemulsion. Therefore, in accordance with another embodiment of the present invention, there is provided an emulsifying wax composition containing from about 5 percent to about 90 percent by weight of the emulsifier composition of the present invention blended with a fatty alcohol containing between 12 and 22 carbon atoms. The emulsifying wax compositions of the present invention are preferably based on fatty alcohols containing 14 to 20 carbon atoms, and more preferably are based on a blend of 16 and 18 carbon atom fatty alcohols. Preferred emulsifying wax compositions of the present invention contain up to about 15 percent by weight of the emulsifier compositions of the present invention.

The emulsifier compositions of the present invention, unlike fatty non-alkoxy ester phosphates, provide oil-in-water emulsions and microemulsions possessing emulsion stabilities that have long been desired by cosmetic chemists for use in personal care products. For purposes of the present invention, a stable emulsion is defined as one that does not phase-separate, as that term is understood by those of ordinary skill in the art, after storage for one month at 40^oC. The oil-in-water emulsions and microemulsions prepared from the emulsifier compositions of the present invention, unlike the stable emulsions produced with fatty alkoxy ester phosphates, have the oil deposition properties of the unstable emulsions prepared using fatty non-alkoxy ester phosphates.

Oil deposition is a desirable property for emulsions and microemulsions to be used in products such as hair straighteners or relaxers. In particular, an improvement in oil deposition reduces the hair damage and irritation associated with such products. In hair relaxers and straighteners, the deposition of oil protects the hair shaft from excessive penetration of hydroxide ion into the hair shaft, which is the cause of hair damage. Oil release by the emulsion onto the hair shaft acts as a protective barrier. Afro-American hair that has been straightened or relaxed with emulsions or microemulsions prepared from the emulsifier compositions of the present invention shows significantly less cuticle damage compared to hair straightening or relaxing emulsions and microemulsions based on other emulsifiers. This reduction in cuticle damage is the result of the controlled oil release and deposition from the emulsion.

The oil deposition properties of the emulsifier compositions of the present invention are also useful in the preparation of other topical emulsion and microemulsion products for keratin-containing substrates, such as sunscreens, wherein the emulsier compositions of the present invention enhance the Sun Protection Factor (SPF) of the sunscreens while greatly improving substantivity, i.e., "wash off" resistance.

Therefore, in accordance with further embodiments of the present invention, there is provided an oil-in-water emulsion containing from about 2 to about 80 percent by weight of an oil phase, from about 10 to about 98 percent by weight of a water phase and the emulsifier composition of the present invention in an amount between about 10 and about 40 percent by weight relative to the oil phase. There is also provided an oil-in-water microemulsion containing from about 5 to about 80 percent by weight of an oil phase, from about 20 to about 95 percent by weight of a water phase and the emulsifier composition of the present invention in an amount between about 100 percent and about 300 percent by weight relative to the oil phase.

The emulsions and microemulsions of the present invention enable cosmetic formulation chemists to produce products with a combination of emulsion stability and oil release heretofore unknown in the art.

Claim 1 of 21 Claims

1. An oil-in-water emulsifier composition comprising:

between about 10 percent and about 70 percent by weight of a blend of mono- and diester phosphates of alkoxylated fatty alcohols containing between about 12 and 22 carbon atoms and alkoxylated with between about 1 and about 50 moles of an alkylene oxide consisting of ethylene oxide, wherein the mono- and di-ester ratio is between about 10:90 and about 90:10; and

between about 90 percent and about 30 percent by weight of a blend of mono- and diester phosphates of non-alkoxylated fatty alcohols containing between about 12 and 22 carbon atoms, wherein the mono- and diester ratio is between about 10:90 and about 90:10.

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