Dry granulation of organic powders—dependence of pressure 2D-distribution on different process parameters

Abstract

Nowadays dry granulation of powders has become a very important research topic because it is the most economic way of granulation, making the particle handling easier, and avoiding the loss of material during particle processing, or particle transfers. This kind of process has been deeply studied but a better knowledge appears necessary to control the great number of parameters of the process. This is particularly important in cases where the nature of the powder may lead to very complex phenomena during compaction.In order to try and optimise dry granulation process for organic compounds, a roll press has been designed with a series of instruments enabling to control the compaction process. The apparatus consists of three parts: a vertical container with rotating steel blades avoiding arches into which the powder is poured, a feeder transferring the powder towards the rolls; the feeder is equipped with an horizontal helical screw in a cylindrical draft tube (10 mm in internal diameter, 500 mm long) and in the end of the feeder, a junction allows the change from the cylindrical symmetry of the feeder to the prismatic symmetry existing in the roll gap. The roll press (0-500 kN, load per unit length 0-10 4 kN m −1 ) has been developed to record different major classical parameters: the roll speed, the roll gap, the press strength, the rotation angle, and the feeding rate (between 0 and 20 g s −1 ). In comparison with different kinds of roll press described in the literature, in this work an original instrumentation system has been developed to catch specific data. The 3D-pressure distribution profiles at the interface between powder and the roll wall and the drive torque applied to the rolls were measured. A large-sized smooth steel-made roll (240 mm diameter, 50 mm width) has been chosen to compare the results to the industrial scale.The results obtained with an organic compound exhibited the dependence-sometimes unexpected-of the rotation angle, the feeding and the rotation speed on the pressure distribution, the roll width, and the drive torque.

Evaluation of Three Approaches for Real-Time Monitoring of Roller Compaction with Near-Infrared Spectroscopy

“…The average density of the produced ribbons is inversely proportional to the roll gap. The relation between density and roll gap is attributed to the fact that the powder is compressed at a much higher compaction pressure when the roll gap is reduced; therefore, more significant densification takes place (5). Roller compactors may be implemented with roll gap control to minimize the density distribution along the ribbon.…”

Mathematical Tools for the Quantitative Definition of a Design Space

“…As shown in Fig. 1, granulation can be accomplished using either wet (e.g., continuous fluid bed, high shear agglomeration, twin screw extrusion) [29,38] or dry (e.g., roller compaction) [28,39,40] methods depending on the API and excipient physical and chemical properties. The selection of a formulation and manufacturing method for a specific product will depend in part on API characteristics, as well as on commercial considerations like projected demand for a product.…”

Modeling of Particulate Processes for the Continuous Manufacture of Solid-Based Pharmaceutical Dosage Forms

“…Bindhumadhavan et al [62] have studied the influence of roll speed and roll gap on pressure profiles during roller compaction. The influence of rotation angle, feed rate and roll speed on pressure distribution and drive torque applied to the rolls has been experimentally evaluated by Lecompte et al [58]. In addition to varying the angle at which powders are fed to the rolls Miguélez-Morán et al [64] have examined the relationship between lubrication and ribbon density, which is an important performance indicator for roller compaction processes.…”

“…The material properties such as the effective angle of internal friction, angle of wall friction, compressibility and preconsolidation relative density must be determined experimentally [61]. The use of instrumented roller compaction equipment to empirically obtain pressure profiles and torque information has been demonstrated by several authors [58,62]. This information can be used to empirically determine friction coefficients and angles as well as roll force.…”

“…Powders that have low bulk density, small particle size (e.g., micronized materials) or are very cohesive may not perform well in roller compaction [56]. Powders with good flowability and compressibility tend to be better candidates for roller compaction [57,58]. The development of a robust granulation process can be more challenging via dry granulation than wet granulation, but dry granulation offers advantages including the elimination of the granule drying step, shorter processing time and lower capital investment and utility costs.…”