Title:  Oil-in-water emulsion with improved stability

United States Patent:  6,281,236

Assignee:  Alwyn Company, Inc. (Lake Crystal, MN)

Filed:  July 23, 1999

A skin cream composition containing allantoin and an emulsifier has improved stability coming from the adjustment of the pH to a range of 4.5 to 5.8. The lower pH preserves the stability of the allantoin and the functionality of the emulsifier system is maintained. The emulsifier system can be a nonionic emulsifier or an anionic emulsifier plus beeswax. The acid used to adjust the pH can be an organic acid or an inorganic acid. The composition can further comprise other ingredients such as herbal extracts, chelating agents, preservatives, emollients, solvents, and fragrance.

SUMMARY OF THE INVENTION

An improved composition containing allantoin uses an emulsification system in which the pH is adjusted to from about 4.5 to about 5.8 with the use of a small amount of acid.

The emulsification system can include beeswax and an anionic emulsifier that is substantially hydrophilic and is soluble in water. Alternatively, the emulsification system can include a nonionic emulsifier that is an ethoxylated ether or an ethoxylated ester whose carbon chain length ranges from 8 to 22 carbon atoms.

One embodiment of a composition according to the present invention comprises:

(1) allantoin; and

(2) an emulsifier system including beeswax and an anionic emulsifier that is substantially hydrophilic and is soluble in water, the pH of the emulsion being from about 4.5 to about 5.8 after the addition of acid to bring the pH into the range.

The emulsifier can be selected from the group consisting of ammonium lauryl sulfate, sodium lauryl sulfate, sodium laureth sulfate, sodium oleyl succinate, ammonium lauryl sulfosuccinate, sodium dodecylbenzenesulfonate, ammonium laureth sulfate, and sodium lauryl sarcosinate. In one preferred embodiment, the emulsifier is sodium lauryl sulfate.

The composition can comprise at least one organic acid of from 2 to 22 carbon atoms. The organic acid can be citric acid, ascorbic acid, glycolic acid, lactic acid, benzoic acid, or salicylic acid. Alternatively, the composition can comprise at least one inorganic acid selected from the group consisting of hydrochloric acid, sulfuric acid, and phosphoric acid. The composition can comprise both organic and inorganic acids.

Another embodiment of a composition according to the present invention comprises an oil-in-water emulsion comprising:

(1) allantoin; and

(2) an emulsifier system including at least one nonionic emulsifier that is an ethoxylated ether or an ethoxylated ester whose carbon chain length ranges from 8 to 22 carbon atoms, the pH of the emulsion being from about 4.5 to about 5.8 after the addition of acid to bring the pH into the range.

The composition can further include a number of ingredients. These ingredients can include the following:

(1) an emollient component that is one or more of lanolin oil, cetyl alcohol, stearyl alcohol, cod liver oil, and butylated hydroxytoluene;

(2) herbal extracts, including one or more of St. John's wort extract, witch hazel extract, chamomile extract, and arnica extract;

(3) a preservative component that is one or more of methylparaben and propylparaben; and

(4) a solvent component that is one or more of propylene glycol, glycerol, or butylene glycol, and is preferably propylene glycol.

One preferred composition according to the present invention comprises:

(1) water;

(2) sodium lauryl sulfate;

(3) propylene glycol;

(4) tetrasodium EDTA;

(5) citric acid;

(6) lanolin oil;

(7) cetyl alcohol;

(8) stearyl alcohol;

(9) beeswax;

(10) cod liver oil;

(11) butylated hydroxytoluene;

(12) St. John's wort extract;

(13) witch hazel extract;

(14) chamomile extract;

(15) arnica extract;

(16) methylparaben;

(17) propylparaben;

(18) allantoin; and

(19) fragrance;

where the pH of the composition is from about 4.5 to about 5.8.

A more preferred composition according to the present invention comprises:

(1) from about 50% to about 90% of water;

(2) from about 0.5% to about 2.5% of 30% sodium lauryl sulfate;

(3) from about 2.0% to about 9.0% of propylene glycol;

(4) from about 0.05% to about 0.50% of tetrasodium EDTA;

(5) from about 0.05% to about 0.5% of citric acid;

(6) from about 5% to about 15% of lanolin oil;

(7) from about 3% to about 10% of cetyl alcohol;

(8) from about 1% to about 5% of stearyl alcohol;

(9) from about 0.5% to about 2.5% of beeswax;

(10) from about 1.0% to about 7.0% of cod liver oil;

(11) from about 0.1% to about 1.0% of butylated hydroxytoluene;

(12) from about 0.05% to about 0.50% of St. John's wort extract;

(13) from about 0.05% to about 0.50% of witch hazel extract;

(14) from about 0.05% to about 0.5% of chamomile extract;

(15) from about 0.05% to about 0.5% of arnica extract;

(16) from about 0.1% to about 0.5% of methylparaben;

(17) from about 0.1% to about 0.5% of propylparaben;

(18) from about 0.50% to about 2% of allantoin; and

(19) from about 0.05% to about 0.50% of fragrance;

the pH of the composition being from about 4.5 to about 5.8.

A still more preferred composition according to the present invention comprises:

(1) from about 55% to about 75% of water;

(2) from about 1.0% to about 2.5% of 30% sodium lauryl sulfate;

(3) from about 3.0% to about 6.0% of propylene glycol;

(4) from about 0.1% to about 0.3% of tetrasodium EDTA;

(5) from about 0.08% to about 0.35% of citric acid;

(6) from about 8.0% to about 12.0% of lanolin oil;

(7) from about 3.5% to about 7.5% of cetyl alcohol;

(8) from about 1.0% to about 3.0% of stearyl alcohol;

(9) from about 1.0% to about 2.5% of beeswax;

(10) from about 1.0% to about 4.0% of cod liver oil;

(11) from about 0.2% to about 0.8% of butylated hydroxytoluene;

(12) from about 0.05% to about 0.15% of St. John's wort extract;

(13) from about 0.05% to about 0.15% of witch hazel extract;

(14) from about 0.05% to about 0.15% of chamomile extract;

(15) from about 0.05% to about 0.15% of arnica extract;

(16) from about 0.15% to about 0.40% of methylparaben;

(17) from about 0.10% to about 0.30% of propylparaben;

(18) from about 0.50% to about 2.0% of allantoin; and

(19) from about 0.1% to about 0.3% of fragrance;

the composition having a pH of from about 4.5 to about 5.8.

A still more preferred composition according to the present invention comprises:

(1) about 68.68% of water;

(2) about 1.9% of 30% sodium lauryl sulfate;

(3) about 5.3% of propylene glycol;

(4) about 0.15% of tetrasodium EDTA;

(5) about 0.12% of citric acid;

(6) about 10.6% of lanolin oil;

(7) about 4.2% of cetyl alcohol;

(8) about 2.0% of stearyl alcohol;

(9) about 1.90% of beeswax;

(10) about 2.0% of cod liver oil;

(11) about 0.5% of butylated hydroxytoluene;

(12) about 0.1% of St. John's wort extract;

(13) about 0.1% of witch hazel extract;

(14) about 0.1% of chamomile extract;

(15) about 0.1% of arnica extract;

(16) about 0.3% of methylparaben;

(17) about 0.25% of propylparaben;

(18) about 1.50% of allantoin; and

(19) about 0.20% of fragrance;

the composition having a pH of from about 4.5 to about 5.8.

Claim 1 of 48 Claims

I claim:

1. A composition consisting essentially of an oil-in-water emulsion comprising:

(a) allantoin; and

(b) an emulsifier system including beeswax and an anionic emulsifier that is hydrophilic and is soluble in water; and

(c) an acid to adjust the pH of the emulsion to a value from about 4.5 to about 5.8, the allantoin being stable in the emulsion for at least 90 days at 40^oC.

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