Emulsification

An emulsion is understood to be the fine (homogenous) mixture of two immiscible liquids (phases), such as in the case of Creams which have been stably bound together by the process of emulsification. The aim of emulsification is to divide the discontinuous phase into fine droplets, which results in an increase in the boundary interface between the two source liquids. This is also a basic task of Agitation in general. As a rule, emulsions are turbid and milky. They are usually maintained for a certain period of time, whereby the temperature and Ph-range play an important role. Emulsions are generally kept stable by emulsifiers, which prevent coagulation of the once-formed droplets.

By emulsifying – dividing the droplets – the buoyancy of the individual droplets is reduced and the “creaming” slowed down. In addition, further additives can be mixed in, which increase the viscosity of the continuous phase and thereby reduce the rate of ascent, which changes the surface charge of the droplets and thus the droplets repel each other or act in a different manner to surface-active substances. Similar processes to emulsification are those of   Homogenisation and Dispersion

The latest innovation is our Dosing Station for weighing and dosing liquid raw materials, which represents a considerable rationalisation of the process.

Consulting and the sale of used homogenising mixers and process plants for the process, such as emulsification, is a further focal point in our service spectrum.

In the case of emulsification, it is above all the boundary interface tension on the oil-water phase boundary that must be overcome. This occurs on the one hand by the input of energy, which triggers shearing forces that reduce the size of the droplets and thus enlarge the boundary interface between the substances. On the other hand, tensides are used that have a lipophilic and a hydrophilic part and can thus mediate between the two phases.

Despite the mediation of the tensides emulsions are unstable systems, as the fine droplets produced during emulsification merge into larger drops over time. The formation of larger drops reduces the size of the boundary interface and the emulsion breaks down. Butter, for example, is formed when cream, a milk fat-in-water emulsion, breaks down.

Applications

A classic application is the production of cosmetic emulsions for strengthening the protective acid mantle and the permeation barrier of the human skin. Other typical  applications of emulsification are the preparation of

• Creams
• Cosmetic sunscreen products
• Lotions

Details

The production of stable and effective emulsions presents mixing technology with series of challenges, as not only the process parameters, such as temperature, pressure, etc. are of great importance, but also the technology employed in the field of the homogeniser. From the general geometry, the speed-dependent number of shear rates, the gap dimensions of the rotor-stator toothing and the design of feeds for other raw materials up to the housing and drive design, diverse details can cause considerable differences in quality and production speed, or decide the general feasibility of the process. Another important feature is the cleanability of the homogeniser, without dead space, in order to ensure compliance with current hygiene standards during emulsification.

If abrasive raw materials are used, such as in the case of Toothpaste, hardening of the rotor-stator teeth is also recommended, in order to increase the service life. Another large cost factor can be maintenance. Besides the rotor-stator toothing, the seal is also a particularly stressed part of the homogeniser. The seal is usually designed as a double mechanical seal. Depending on the product, the seals must be selected accordingly. We will be glad to advise you on the subject of emulsification.