An Investigation into the Formation of Wax Emulsions

Abstract

Wax emulsions have been part of every day life for many years. They find use in a wide variety of products such as furniture and floor polishes,aerosol sprays, cosmetic: products, and are used to coat various articles from paper to fruit. Occasionally, substandard batches are produced and the reasons for the defects are not always known. Procedures for the recovery of such batches are far from perfect and, because the raw materials have a relatively high value, considerable loss to a manufacturer can result. A review of the literature over approximately sixty years indicated that little specific information had been published about wax emulsions, and that established emulsion manufacturing techniques were virtually unchanged over the same period. Therefore the following objectives were formulated:- A. The Investigation of a satisfactory means for assessing product quality. B. The Definition and ranking of the system variables. C. The Investigation into the 'mechanism' of wax emulsification. D. The Application of the study findings to existing commercial methods for wax emulsion manufacture, including the reworking of unsatisfactory batches. The study produced the following conclusions:- A. The most important criteria of wax emulsion quality are those of appearance and stability. Appearance is viewed subjectively by the creaming, translucency and the viscosity of the product, and is best assessed either by gravimetric determination of the percentage of disperse phase above 10 microns or by microscopic examination. Stability is a parameter of product shelf-life and new freeze-thaw and titration techniques have been developed which give rapid and reliable results. B. Although fourteen variables have been identified and investigated in the wax emulsification process, only three are determined as important.These are:- a. Level and type of emulsifier(s). b. Degree of wax saponification if required as part of the emulsifier system. c. Extent and type of agitation provided during emulsification. C. Wax emulsification, using the most common method of surface addition at atmospheric pressure, proceeds via the formation of wax filaments which, after being drawn below the water surface, are converted to droplets by shear forces. These forces are applied by velocity differentials between wax and water, in turn induced by agitation.Wax emulsification differs from conventional liquid/liquid processes because a phase change is usually involved. Droplet formation must occur prior to this change or a substandard emulsion results. D. Some basic manufacturing rules are proposed to reduce the proportion of substandard batches. When these do occur however, those containing waxes that may be liquified below the normal boiling point of water, may be reworked by reheating and mechanical homogenisation. Unsatisfactory products containing waxes of higher melting ranges can only be reworked using the technique of pressure emulsification. Further improvements to manufacturing methods should be possible. Continuous processing and pressure emulsification are concluded to be areas where future research might prove most rewarding in finding more economical and efficient ways of producing wax emulsions.