초록

Stable hydroquinone compositions that are useful for skin care and can have a shelf life of up to three years are prepared in a tank made from a material that does not release metallic ions into the composition.

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1. A method comprising: (a) passivating a stainless steel tank to chelate metallic ions therein, thereby preparing a passivated tank; and then(b) preparing an emulsion containing hydroquinone, a preservative, a chelating agent, an emulsifier, a humectant, a pH adjuster, an antioxidant, an emollient,

1. A method comprising: (a) passivating a stainless steel tank to chelate metallic ions therein, thereby preparing a passivated tank; and then(b) preparing an emulsion containing hydroquinone, a preservative, a chelating agent, an emulsifier, a humectant, a pH adjuster, an antioxidant, an emollient, and a reducing agent in the passivated tank of step (a),wherein the discoloration of the emulsion is slowed compared to the discoloration of the same emulsion that has not been prepared in the passivated tank. 2. The method of claim 1, wherein passivating the stainless steel tank comprises contacting the stainless steel tank with a chelating acid. 3. The method of claim 2, wherein the chelating acid is citric acid. 4. The method of claim 1, wherein the preservative is a member selected from the group consisting of benzoic acid, benzyl alcohol, butylparaben, diazolidinyl urea, 2,3-Imidazolidinedione, isopropylparaben, isobutylparaben, methylparaben, propylparaben, sodium butylparaben, sorbic acid, and combinations thereof. 5. The method of claim 1, wherein the chelating agent is a member selected from the group consisting of citric acid, edetate disodium, ethylenediaminetetraacetic acid, etidronic acid sodium dihydroxyethylglycinate, nitrilotriacetic acid, and combinations thereof. 6. The method of claim 1, wherein the emulsifier is a member selected from the group consisting of cetearyl alcohol, ethoxylated fatty alcohols,PEG-1000 monocetyl ether, alkyl trimethyl ammonium bromide, polyol ester glycerol monostearate, potassium stearate, sodium lauryl sulfate, sodium cetearyl sulfate, saponins, and combinations thereof. 7. The method of claim 1, wherein the humectant is a member selected from the group consisting of glycerin, diglycerin, triglycerin, polyglycerin, polypropylene glycol, polyethylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, ethylene glycol monoalkyl ether, diethylene glycol monoalkyl ether, glucose, maltose, sucrose, lactose, xylitose, xylitol, sorbitol, mannitol, maltitol, panthenol, pentaerythritol, hyaluronic acid, and combinations thereof. 8. The method of claim 1, wherein the pH adjuster is a member selected from the group consisting of citric acid, phosphoric acid, lactic acid, glycolic acid, and combinations thereof. 9. The method of claim 1, wherein the antioxidant is a member selected from the group consisting of ascorbyl palmitate, 2,6 ditertiarybutyl-4-methyl phenol, butylated hydroxyanisole, tocopherol, tocopheryl acetate, propyl gallate, and combinations thereof. 10. The method of claim 1, wherein the emollient is a member selected from the group consisting of cetyl alcohol, stearyl alcohol, liquid hydrocarbon oil, liquid natural oil, liquid fatty alcohol, liquid fatty acid, liquid fatty acid ester, liquid silicone oil, paste wax, and combinations thereof. 11. The method of claim 10, wherein the liquid hydrocarbon oil is a member selected from the group consisting of squalane, liquid mineral oil, liquid polybutene, and combinations thereof. 12. The method of claim 10, wherein the liquid natural oil is a member selected from the group consisting of almond oil, olive oil, sesame oil, safflower oil, avocado oil, cottonseed oil, jojoba oil, castor oil, soybean oil, palm kernel oil, coconut oil, hydrogenated vegetable oil, mink oil, egg yolk oil, and combinations thereof. 13. The method of claim 10, wherein the liquid fatty alcohol is a member selected from the group consisting of isostearyl alcohol, lanolin alcohol, oleyl alcohol, hexadecyl alcohol, octyldodecanol alcohol, linoleyl alcohol, linolenyl alcohol, lauryl alcohol, arachidyl alcohol, and combinations thereof. 14. The method of claim 10, wherein the liquid fatty acid is a member selected from the group consisting of caprylic acid, isostearic acid, linoleic acid, ricinoleic acid, oleic acid, and combinations thereof. 15. The method of claim 10, wherein the liquid fatty acid ester is a member selected from the group consisting of cetyl octanoate, glyceryl trioctanoate, isopropyl linoleate, isopropyl myristate, isopropyl oleate, ethyllaurate, ethyl linoleate, octyl dodecyl myristate, octyl palmitate, octyl isopelargonate, octyl dodecyllactate, isotridecyl isononanoate, oleyl oleate, isostearyl myristate, neopentyl glycol dioctanoate, and di(capryl/capric acid) propylene glycol, and combinations thereof. 16. The method of claim 1, wherein the reducing agent is a member selected from the group consisting of ascorbic acid, propyl gallate, sodium metabisulfite, and combination thereof. 17. The method of claim 1, wherein the emulsion comprises a viscosity of from about 1,000 to about 50,000 centipoise. 18. The method of claim 1, further comprising adding a sunscreen. 19. The method of claim 1, wherein the emulsion is a lotion. 20. The method of claim 1, wherein the emulsion maintains an acceptable color for three years. 21. The method of claim 20, wherein the acceptable color is a color lighter than brown. 22. A method for preparing a topical hydroquinone composition, the method comprising: preparing an emulsion containing hydroquinone, a preservative, a chelating agent, an emulsifier, a humectant, a pH adjuster, an antioxidant, an emollient and a reducing agent in a passivated stainless steel tank, wherein the stainless steel tank is passivated prior to preparing the emulsion in the stainless steel tank;wherein the discoloration of the emulsion is slowed compared to the discoloration of the same emulsion that has been prepared in a non-passivated tank.