Basic scientific research has shown that the mechanical power that is transferred into the millbase is closely related to the dispersion result. The mechanical power determines the energy that is transmitted by the agitator via the grinding beads to the product. The power P is calculated from the speed n of the agitator and the torque M generated on the agitator according to the following equation:
P = 2 π n M
P = power [Nm/s=J/s=W]
π = 3.141...
n = speed [1/s]
M = torque [Nm]
The higher the realised mechanical power input the higher is the energy, brought into the container. It does not matter whether the power input which leads to the existing energy density, is applied with a high‒speed and low torque or vice versa. To get all agglomerates at least one time in a zone of highest energy density, which means that if the dispersion condition with longer dispersion time does not change at a given bead filling charge and sufficient long dispersion time, the dispersion result depends only on the amount of the mechanical power. The torque therefore depends directly on the flow characteristics of the millbase. If the viscosity changes during dispersion at constant speed, the power input changes automatically.
If the viscosity decreases during dispersion, the mechanical power drops, and if it increases, the mechanical power rises. If the formulation is operated under a stronger cooling, the mechanical power input is higher due to the higher viscosity of the mill base. With a lower cooling the power input is correspondingly lower. This for example, is the reason why dispersion results may literally depend on the season, because in winter, the cooling water may be much colder than in summer!
The DISPERMAT® SL solves this problem by enabling the mechanical power input for dispersion to be pre‒set. During dispersion the torque of the rotor is continuously measured and the speed controlled, so that the product of n and M leads to precisely the pre‒set mechanical power. Apart from the agitator geometry and the viscosity of the millbase, the torque transmitted by the shaft onto the millbase also depends on the type, quantity and size of the grinding beads. High bead filling volumes increase the torque on the agitator shaft and also increase the probability that agglomerates come into a spatial dispersion situation.