Dry granulation by roller compaction is a continuous process applied routinely to convert fine, difficult to handle powders into uniform granular products that flow freely and perform efficiently in subsequent manufacturing steps. The advantages of roller compaction include relatively modest capital investment, low running and maintenance costs, and high energy efficiency. Particularly suitable for moisture or heat sensitive materials and those that require ultra-high containment, dry granulation is an important step in the manufacture of pharmaceuticals.
Processing powder blends can present a number of challenges: component powders may be poorly flowing in the process, the blends may be susceptible to segregation, or the formation of agglomerates may affect homogeneity. Granulation is used in a range of industries and applications to combine multiple components of a blend into a more free-flowing, homogeneous intermediate product for downstream processing. It is frequently carried out as a wet process, but the resultant wet mass has to be dried and milled to generate a processable product. This can be time consuming and expensive, and in some cases not possible due to chemical and/or thermal degradation of the active ingredient.

MINI-PACTOR® Roller Compactor FT4 Powder Rheometer®
(Gerteis Maschinen+Processengineering AG, Switzerland) (Freeman Technology Ltd)
Dry granulation has significant benefits in terms of both processing and cost reduction, and can be used with sensitive materials. However, there is little indication of which process parameters produce optimal granulate quality in order to achieve interruption free processing and high-quality products. Most equipment suppliers and product manufacturers therefore rely on historical and ad-hoc trial information to identify suitable parameters.
This application note details the joint study undertaken by Freeman Technology Ltd. and Gerteis Maschinen+Processengineering AG, to investigate how process parameters influenced the properties of the dry granulate of a placebo formulation.
Methods
A placebo formulation consisting of 70% lactose, 29.5% microcrystalline cellulose and 0.5% magnesium stearate was granulated using a Gerteis MINI-PACTOR® roller compactor, on which the Roll Gap, Compaction Force and roller speed can be varied together with the screen/sieve size. The resulting granulates were evaluated using a Freeman Technology FT4 Powder Rheometer® to quantify the dynamic, bulk and shear properties.
The Effect of Compaction Force
Six identical batches of the feedstock were processed in the MINI-PACTOR® at different Compaction Forces:









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