Effect of operating conditions on dry particle coating in a high shear mixer

An investigation into the effects of the operating conditions on a dry particle coating process has been performed with mixtures of sugar grains (Suglet®) and magnesium stearate (MgSt) as the host and invited particles, respectively. Dry coating has been carried out in a high shear mixer (Cyclomix®) at different processing times t, rotational speeds ω, and filling ratios J, of the mixer. In order to determine the effect of the operating conditions on the properties of the products, the changes in flowability and wettability of the mixtures as a function of ω, J and the operating time t have been analyzed.The flowability is found to be improved by longer processing times. Higher speeds of rotations can improve the flowability more rapidly. However, the flowability does not seem to be sensitive to the filling ratio and it may be concluded that operating with higher filling ratios gives higher production. A method is proposed to measure the mass fraction of invited particles on the surfaces of the host particles. This fraction is linked to the product properties as the flowability and wettability. This result can be predicted by a model using a coating rate constant kc which can be used to optimize dry coating processes to give desired properties of coated particles. This coating rate constant can define and represent the efficiency of the dry coating.

Investigation on the effects of the operating conditions on dry coating process has been done. The conversion ration measured by sieving and the properties of coated particles, the wettability and the flowability show a linear relation. The efficiency of the dry coating can be estimated by exploiting a simple and easy sieving.Figure optionsDownload as PowerPoint slideHighlights
► Some effects of operating conditions on dry coating have been studied.
► The properties of particles changed with the operating time and the rotation speed.
► A conversion ratio for dry coating has been defined and measured.
► Relations between composition and properties of powder mixtures were established.
► The dry coating efficiency could be estimated by using those relations.