Twin-screw granulation – a systematic analysis of process parameters

Twin-screw granulation has a significant advantage over traditional granulation methods leading to the possibility of continuous manufacturing. Although this technology has drawn attention in recent years, the general understanding of the process is limited. This study gives a brief overview of the most important process parameters and their influence on product quality. Experimental results from a benchtop granulator and an in-line particle size measurement have been analysed. From this basic study conclusions can be drawn how to tailor the particle size distribution in twin-screw granulation. The most crucial parameters are the liquid-to-solid ratio and the filling level of the screws

A novel methodology to study polymodal particle size distributions produced during continuous wet granulation

It is important during powder granulation to obtain particles of a homogeneous size especially in critical situations such as pharmaceutical manufacture. To date, homogeneity of particle size distribution has been defined by the use of the d50 combined with the span of the particle size distribution, which has been found ineffective for polymodal particle size distributions. This work focuses on demonstrating the limitations of the span parameter to quantify homogeneity and proposes a novel improved metric based on the transformation of a typical particle size distribution curve into a homogeneity factor which can vary from 0 to 100%. The potential of this method as a characterisation tool has been demonstrated through its application to the production of granules using two different materials. The workspace of an 11 mm twin screw granulator was defined for two common excipients (?-lactose monohydrate and microcrystalline cellulose). Homogeneity of the obtained granules varied dramatically from 0 to 95 % in the same workspace, allowing identification of critical process parameters (e.g. feed rate, liquid/solid ratio, torque velocities). In addition it defined the operational conditions required to produce the most homogeneous product within the range 5 ?m – 2.2 mm from both materials