An interfacial tension is formed at the interface between two phases. It attempts to form a small as possible interface surface as possible and thus prevents the existence of dispersion. Dispersion results in a compensation in the area between the phase boundaries of the substances to be mixed, which is achieved by the enlargement of the boundary surfaces of the individual phases. Consequently, the dispersion is an intensive, instantaneous comminution of the liquid droplets and solid particles to as equal as possible sizes. The use of emulsifiers and stabilisers results in a long-term stability of the dispersions.
In industry, the process of dispersion is generally used for the production of Emulsions or Suspensions. Both mixtures are a continuous liquid phase. Whilst, in the case of an Emulsion the disperse phase is also liquid, solid particles are dispersed in a liquid in the case of a Suspension.
Typical areas of application are, for example, the production of:
Dispersion should always be as simple and efficient as possible, whereas the quality of the end product should never be neglected. No-one wants to acquire, for example, a cosmetic product which, after some time, separates out again into the individual phases. When carrying out the process, the parameters raw materials, temperature, pressure and shear sensitivity etc. must be precisely coordinated to create optimum production conditions for dispersion. It is also possible to disperse in batch operation, as well as “In-Line” in continuous operation. Furthermore, it is possible to employ the so-called “Hot-Cold" process during dispersion. In this process, the aqueous phase is dispersed into the (hot) oil phase at a lower temperature, in order to achieve a reduction in temperature during the dispersion. Subsequent cooling phases can be significantly reduced, depending on the product. Appropriate technical design of the disperser and the corresponding drive in advance are of equally paramount importance as the supply of the phases.
Similar procedures to dispersion are Homogenisation and Emulsification.