Hielscher Ultrasonics: Production of fine Emulsions by Ultrasonication
A wide range of intermediate and consumer products, such as cosmetics, skin lotions and pharmaceutical ointments, based wholly or in part of emulsions. Hielscher manufactures innovative and powerful ultrasonic liquid processors for the efficient emulsifying of small and large volumes.
An emulsion is a dispersion of two non-miscable liquids without a visible demixing. To obtain an emulsion, the two liquids have to get mixed together so finely that the droplets of one liquid are well distributed in the other liquid. The most common emulsions are beased upon water and oil. In the pharmaceutical and cosmetical sectors fine and stable emulsions, especially for the manufacture of creams, lotions and ointments as well as for facial cleansing gels, shower gels and foam baths, are very important. Since water and oil are basic essentials in the production of skin-care creams, lotions and ointments, the emulsification is an necessary application.
Ultrasound is an innovative technology for the fine dispersion and emulsification of liquids. Highly intense ultrasound supplies the power needed to disperse a liquid phase (dispersed phase) in small droplets in a second phase (continuous phase). In the dispersing zone, imploding cavitation bubbles cause intensive shock waves in the surrounding liquid and result in the formation of liquid jets of high liquid velocity. These liquid jets reduce the size of the single droplets in the sonicated liquid and stir them. In order to stabilize the newly formed droplets of the disperse phase against coalescence, emulsifiers (surface active substances, surfactants) and stabilizers are added to the emulsion. As coalescence of the droplets after disruption influences the final droplet size distribution, efficiently stabilizing emulsifiers are used to maintain the final droplet size distribution at a level that is equal to the distribution immediately after the droplet disruption in the ultrasonic dispersing zone. Stabilizers actually lead to improved droplet disruption at constant energy density.
Studies at oil in water (water phase) and water in oil (oil phase) emulsions have shown the correlation between the energy density and droplet size (e.g. Sauter diameter). There is a clear tendency for smaller droplet size at increasing energy density. At appropriate energy density levels, ultrasound can well achieve a mean droplet sizes below 1 micron (microemulsion).
This fine emulsion and the increased addition of emulsifiers, which is necessary for stabilization of microemulsions, lead to a better and faster penetration of active care ingredients into the skin. Hielscher Ultrasonics provides ultrasonic devices for the emulsification of volumes in every scale. The product range includes ultrasonic lab devices (50, 100, 200, 400 watt units), as well as for industrial production (500 watts to 16kW processors). Hielscher lab ultrasonic devices are not only used for research and development purposes, but also manufacturers who want to sonicate only small volumes, estimate the effective emulsification of the ultrasonic processors. So, Hielscher lab devices are used i.e. in pharmacies for mixing and emulsifying custom-made creams and ointments in small quantities.
Hielscher Ultrasonics GmbH
Tel.: +49 3328 437 420
Fax: +49 3328 437 444
Hielscher USA, Inc.
19 Forest Rd.
Ringwood, NJ 07456,
Phone: +1 973 616 9136
Fax: +1 973 616 9131