Wax , Anionic Emulsifying

Category

Emulsifier; Thickener

Grade

Pharmceutical Excipients

UNII

NA

Chemical Name

Anionic emulsifying wax

CAS Number

8014-38-8

Stability and Storage Conditions

Solid anionic emulsified wax is chemically stable and should be stored in a closed container in a cool and dry place.

Source and Preparation

Anionic emulsified wax is prepared by melting cetyl alcohol and heating it to 95℃, then adding purified water and sodium dodecyl sulfate or other suitable anionic surfactants. Heat the mixture to 115℃ and maintain this temperature. Stir vigorously until the mixture stops bubbling and cools quickly.

Applications

Anionic emulsifying wax is mainly used as emulsifier in cosmetics and topical pharmaceutical preparations. This product is added to a fat or paraffin matrix to promote the formation of an oil-in-water (o/w) emulsion without greasy feeling. At a concentration of about 2%, the emulsion can still flow. Thicker emulsions, such as the water-based cream listed in the British Pharmacopeia, can contain up to 10% anionic emulsifying wax. The cream should be properly treated with corrosion protection, usually by autoclaving. Better quality emulsions add some alkaline substances to the water phase, but be careful not to excess. Anionic emulsifying waxes (3.to 30%) can also be mixed with Vaseline or liquid paraffin to prepare anhydrous ointment substrates, such as those included in the British Pharmacopoeia. A preparation of white vaseline with 80% anionic emulsified wax has been used as a soap replacement for eczema. In addition, anionic emulsified wax (10%) was added to the cocoa butter to prepare a suppository matrix with a melting point of 34℃.

Incompatibilities

The main incompatibility substances with anionic emulsified wax are sodium alkyl sulfate, cationic compounds (quaternary ammonium compounds, acridinflavin, ephedrine hydrochloride, antihistamines and other nitrogen compounds), polyvalent metal salts (aluminum, zinc, tin and lead) and thioglycolate. Anionic emulsified wax is compatible with most acids at pH above 2.5, as well as with alkalis and hard water. Anion emulsion wax should not be heated in iron containers, but stainless steel containers can be used.