Low-shear granulators

Shiromani, PK. and Clair, J., Statistical comparison of high shear vs. low shear granulation using a common formulation, Drug Dev. Ind. Pharm., 26, 357, 2000. 

Wet low-shear granulator subclasses primarily are distinguished by the geometry and design of the shear inducing components shear can be induced by rotating impeller, reciprocal kneading action, or convection screw action. 

Wet granulators can be divided into three main types low-shear granulators, high-shear granulators, and fluidized bed granulators.1-4,6 The third type is the focus of another chapter in this book and will not be discussed in details here. Table 5.1 provides a summary of some of the different granulators that are commonly used in the pharmaceutical industry. 

Low-Shear Granulators. These are the traditional granulators and are of the planetary type (e.g., Hobart, Collette) or the kneading type (Z-blade mixers). Another type of these low-shear granulators consists of a V-blender with an intensifier bar (e.g., Patterson-Kelley). 

There are other ways to make granulated products. Instant products such as instant cacao (a mixture of cacao powder, sugar and milk) can be made by low shear granulation like the Hosokawa Flexomix technology, as shown in Figure 16.9. For example, an instant cacao produced this way dissolves easily and disperses the cacao (very hydrophobic) quickly without lump formation. 

Chirkot, T. Propst, CW. Low shear granulators. In Handbook of Pharmaceutical Granulation Technology, Parikh, D.M., Ed. Marcel Dekker, Inc. New York, 1997. 

Chirkot, T. Scale-up and endpoint issues of pharmaceutical wet granulation in a V-type low shear granulator. Drug Dev. Ind. Pharm. 2002, 28 (7), 871-888. 

A high shear granulator will produce a relatively lower porosity granule than a low shear granulator, milling of the dry powders prior to granulation will produce smaller... 

Wet low-shear granulation—rotating low-shear forces via low-power-per-unit-mass with addition of a liquid. 

Pharmaceutical Granulation Processes, Mechanism, and the Use of Binders 275 Low-Shear Granulation... 

Chirkot T. Proposl C. Low-shear granulation. In Parikh D, Handbook of Pharmaceutical Granulation Technology. Boca Raton, FL Taylor Francis, 2006 230. 

Low-shear granulators—twin shell (Peterson Kelly, PK) with an agitator bar, dough mixer or planetary mixer, ribbon blenders, and fluid bed granulator without the rotogranulator... 

Granulation of highly cohesive materials containing hydrophilic polymers, which is not achievable with low-shear granulation processes... 

Scaling up the process in a low-shear granulator is a daunting task. Scale-up equations are usually proprietary to the mixer manufacturers and little is written about them in the literature. The equations have a sound basis in science but are ameliorated by constants and factors that take into consideration empirical feedback and intuition concerning the machine function. 

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