Self-emulsifying fat for pharmaceutical and cosmetic use, preparation and use thereof.

The present invention relates to a non-ionic self-­emulsifying fat, consisting of a mixture of partly esteri­fied and ethoxylated C₆- C₁₈ fatty acids and C₆-C₂₀ fatty alcohols or polyalcohols, to a process for the preparation thereof and to the use as a carrier and/or excipient in cosmetic and pharmaceutical formulations.

Non-ionic emulsifying fats are used in pharmaceuti­cal and cosmetic technique as bases for oil/water emul­sions such as creams, milks, etc. Up to now no emulsifying agents were available which fulfill at the same time the essential requirements for the intended use such as no toxicity, very good topical tolerability, long-term stabi­lity of the obtained emulsions within a wide temperature and pH range, compatibility with both acid and basic acti­ve ingredients .

The present invention allows to achieve the above cited characteristics and advantages, providing a non-­ionic self-emulsifying fat prepared according to a precise operative sequence and consisting of - C₆ -C₂₀ fatty alcohols; - ethoxylated fatty alcohols of formula R₁O(CH₂ CH₂O)_nH, wherein R₁ is an alkyl residue of a C₆-C₂₀ fatty alcohol and n is an integer from 1 to 5; - ethoxylated fatty acids of formula R-COO(CH₂CH₂O)_nH, wherein R is an alkyl residue of a C₆6-C₁₈ fatty acid and n is an integer from 1 to 5; - fatty acids monoglycerides; - optionally a polyalcohol such as glycerol.

Examples of ethoxylated and non-ethoxylated fatty alcohols, which may be comprised in the composition of the fat according to the invention, comprise hexanol, octanol, decanol, dodecanol, isotridecyl alcohol, tetradecanol, hexadecanol, octadecanol, oleyl alcohol, eicosanol.

Examples of fatty acids comprise caproic, caprylic, caprynic, lauric, myristic, palmitic, stearic, isostearic, oleic acids.

In case of ethoxylated alcohols or acids, n in the above formulae is preferably 2.

Optionally ethoxylated stearic and oleic monoglyce­rides are preferably used as monoglycerides.

C₆-C₂₀ fatty alcohols are present in amounts of 35-50%, ethoxylated alcohols in 5 to 15%, ethoxylated fatty acids in 15 to 25% and monoglycerides in 5 to 15%.

Fatty alcohols and acids used in the formulation of the emulsifier according to the invention show a distribu­tion of the various molecular species which is characteri­stic of the commercial source from which they derive. For example, in case of fatty alcohols, C₆-C₁₂ alcohols are typically present in percentages ranging from 3 to 7%, C₁₄ alcohol from 0 to 2%, C₁₆ alcohol from 8 to 12%, C₁₈ and C₂₀ alcohols from 10 to 14%. Moreover, lesser amount of C₂₂ and C₂₄ homologues may be present.

The process for the preparation consists of two separate steps: in a first step, ethoxylated alcohols are dissolved with a part of the homologues under slow stir­ring and in inert atmosphere, at a temperature from 40 to 60°C. When dissolution is complete, water is removed off by distillation under vacuum.

Separately, monoglycerides are added to the fatty acids maintained at the melt state, under vacuum, at a temperature ranging from 40 to 60°C.

After removal of water by distillation under vacuum, the remaining fatty alcohols are added and the two phases are mixed under fast stirring at a temperature from 50 to 60°C.

The following example illustrates the process of the invention in more detail.

EXAMPLE

<ul id="ul0001" list-style="none"><li>a) A portion of the ethoxylated alcohols (C₁₂-C₁₄ alcohols 4 OE) was dissolved in a stainless steel reactor with a portion of the homologues fatty alcohols; dissolu­tion occurred under slow stirring in a nitrogen atmosphere at a temperature from 40 to 60°C. When the optimum temperature was attained, vacuum was applied to the reactor and water was distilled off, until no dropping was observed. The obtained mixture was transferred into a heated and thermostatized vessel, at a temperature from 50 to 60°C.</li><li>b) An exactly weighed amount of 5 OE coconut fatty acids was placed into a reactor and melted under vacuum at a temperature from 40 to 60°C; then glyceryl monooleate and monostearate 15 OE were added. When the optimum temperature was reached, water was distilled under vacuum until no dropping was observed. Vacuum was interrupted with nitrogen and the remaining fatty alcohols were slowly added. After dissolution, the second phase was added to the first one under quick stir­ ring at a temperature ranging from 50 to 60°C. After 30-50 minutes the mixture was quickly cooled, under slow stir­ring, to a temperature of 18-22°C.</li></ul>

A thick creamy past, having a slight characteristic odour, was obtained.

Characteristics of the product

Aspect: white pasty mass. Color: varying from white to cream white. Odour: slight and characteristic. Solubility: soluble in oils. Acidity index: Max 2. Jodine index: Max 20. Peroxide index: Max 5. Saponification index: 80-110. Moisture: lower than 1%. HLB (ATLAS system): 12.1.

Toxicological data

<u style="single">Acute toxicity</u>: evaluated on Swiss albino mice weighing 25-30 g, by intraperitoneal route. LD₅₀: higher than 8 g/kg. <u style="single">Chronic toxicity</u>: no toxicity.

The product caused no sensitization on epidermis and derma, after prolonged treatment on rabbit epilated cutis, neither on human cutis of healthy volunteers.

The Draize test, carried out on New Zealand rabbits at a 10% concentration, evidenced a slightly irritative action on the conjunctiva.

The emulsifier of the invention is used in the preparation of o/w emulsions, both creams and milks, in a percentage which varies from 8 to 10%; if necessary, said percentage may be increased up to 20%, obtaining the emul­sion without further addition of the oily phase.

In view of its chemical nature, the fat according to the invention may conglobate active ingredients having both acid and basic characteristics, keeping stability during the time unchanged.