Polyamide compositions for personal care

A method which comprises formulating an ethanol-based personal care product to contain a hydrophobic polyamide, said polyamide comprising:

• (a) a reaction product of a dimerized fatty acid, at least one C2-C4 carboxylic acid, and a polyamine component comprising ethylenediamine and 1 to 30 eq. % of one or more di- or triamines;
• or
• (b) a reaction product of a dimerized fatty acid, at least 50 wt. % of a C16-C22 unsaturated carboxylic acid, and at least one C2-C6 diamine;
• wherein the polyamide is used in an amount effective to boost the SPF of the product by at least 50% compared with that of a similar product formulated in the absence of the polyamide.

An oil-in-water emulsion comprising:

• (a) a continuous phase comprising 30 to 90 wt. %, based on the amount of emulsion, of water;
• and
• (b) a discontinuous phase comprising at least one oil component and a hydrophobic polyamide, wherein the polyamide comprises:
• (i) a reaction product of a dimerized fatty acid, at least one C2-C4 carboxylic acid, and a polyamine component comprising ethylenediamine and 1 to 30 eq. % of one or more di- or triamines;
• or
• (ii) a reaction product of a dimerized fatty acid, at least 50 wt. % of a C16-C22 unsaturated carboxylic acid, and at least one C2-C6 diamine.

A water-in-oil emulsion comprising:

• (a) a discontinuous phase comprising water;
• and
• (b) a continuous phase comprising at least one oil component and a hydrophobic polyamide, wherein the polyamide comprises:
• (i) a reaction product of a dimerized fatty acid, at least one C2-C4 carboxylic acid, and a polyamine component comprising ethylenediamine and 1 to 30 eq. % of one or more di- or triamines;
• or
• (ii) a reaction product of a dimerized fatty acid, at least 50 wt. % of a C16-C22 unsaturated carboxylic acid, and at least one C2-C6 diamine.

A method of comparing the skin-tightening features of two or more formulations containing film-forming polymers, the method comprising:

• (a) mounting a skin substitute on an apparatus which comprises:
• (i) a force-measuring machine equipped with a load cell, the load cell being attached to one end of the skin substitute;
• (ii) a stabilizing means for holding the other end of the skin substitute;
• and
• (iii) a horizontal temperature-controlled testing region established between the load cell and the stabilizing means;
• (b) applying a test formulation comprising a film-forming polymer to the skin substitute in the testing region;
• (c) allowing the formulation to equilibrate and form a film at a desired testing temperature;
• (d) measuring the load cell output as a function of time to evaluate the amount of contractile force on the skin substitute from the film;
• and
• (e) comparing the results of using the test formulation with those of a control formulation.