Use of High-Pressure Homogenization in Wax Emulsion

A wax emulsion is the stable mixture of one or more waxes in water, achieved through high-pressure homogenization. Wax and water don’t usually mix, but they can be brought together with the use of surfactants. As beeswax is solid at room temperature, an emulsion of wax should definitely be called a wax dispersion. However, since the preparation takes place above the melting point of the wax, the actual process is referred to as emulsification, hence the name wax emulsion. In practice, wax dispersion is used for solvent-based systems.

Wax emulsions are widely used in various technical applications, such as printing inks and polishes, leather and textile products, paper, wood, metal, polishes, fiberglass sizing, and glass bottle protection. The most important properties that can be enhanced by the addition of beeswax emulsions are mattifying and shine, hydrophobicity, soft touch, wear and friction resistance, release, and protection against corrosion.

Emulsions based on natural waxes are used for coating fruits and confectionery and for crop protection. Synthetic wax-based emulsions are typically used in food packaging.

Generally, the wax is melted with water at a high temperature. The water is heated to a temperature depending on the melting point of the wax. The melted wax is slowly added to the water phase with good agitation. The agitation should be sufficient to distribute the melted wax efficiently, but vortexing should be minimized to prevent the entrainment of large amounts of air.

Once a good premix has been produced, the hot wax/water mixture is homogenized. The pressure limit is around 200-350 bar, depending on the desired particle size range.

Following the effects of homogenization, the emulsion is rapidly cooled to “set” the wax particles. After the homogenization process, the wax emulsion is rapidly cooled. For good stability and mechanical properties, it is desired that the wax particles be below 2 or 3 micrometers.