Systematic evaluations regarding interparticular mass transfer in spheronization

Koester, Martin; Willemsen, Emilie; Krueger, Cornelia; Thommes, Markus

doi:10.1016/j.ijpharm.2012.04.045

Cited by 14 publications

(11 citation statements)

References 10 publications

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“…[19,20] Based on these results, the small-scale process was suitable for moisture screening because all effects described in large scale were found. The absolute values for AR, equivalent diameter and WC deviated with respect to the previous investigation [33] because a different spheronizer with a different geometry was used.…”

Section: Wet Extrusion-spheronizationcontrasting

confidence: 72%

“…This is a cost-consuming process because large quantities of material are usually required. This process should be downsized using the small-scale extruder, and small-scale spheronizer as well (Caleva 120), in a batch size of 20 g. The tested formulations were already described by [33] using a larger scale of 300-g batch size.…”

Section: Wet Extrusion-spheronizationmentioning

confidence: 99%

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Small-scale twin-screw extrusion – evaluation of continuous split feeding

Muehlenfeld

Thommes

2014

Journal of Pharmacy and Pharmacology

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Section: Wet Extrusion-spheronizationcontrasting

confidence: 72%

Section: Wet Extrusion-spheronizationmentioning

confidence: 99%

Small-scale twin-screw extrusion – evaluation of continuous split feeding

Muehlenfeld

Thommes

2014

Journal of Pharmacy and Pharmacology

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“…Baert et al [6] reported that twisting of the extrudates played an important part in their breakage and subsequent rounding. Liew et al [7] stated that fines generated at the point of extrudate breakage and by attrition during collisions played an important role in rounding, which was supported by the experimental studies of Koester et al [8]. The tendency to generate fines, which favours the Liew et al mechanism over that of Rowe, was shown by Bryan et al [9] to be related to the processing history of the paste.…”

Section: Introductionmentioning

confidence: 90%

Experimental validation of a dimensional analysis of spheronisation of cylindrical extrudates

et al. 2016

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Extrusion-spheronisation (E-S) is a widely used technique for the manufacture of pellets with high sphericity and narrow size distribution. A dimensionless framework for describing the evolution of pellet shape with spheronisation time is presented.The experiments employed a 45 wt% microcrystalline cellulose (MCC)/water-based paste, with up to 15 wt% calcium carbonate added to represent a 'hard' active pharmaceutical ingredient (API). The bulk yield strength of the paste was measured and found to increase with increasing carbonate content, which in turn led to higher extrusion pressures, longer spheronisation times and less spherical pellets for a given set of operating parameters. The pellet aspect ratio was found to increase in a linear manner with the logarithm of spheronisation time, progressing towards an asymptotic final value. This behaviour is compared with two simple models.The dimensional analysis of the pellet rounding stage identified the paste density and bulk yield strength as scaling quantities. The model borne from the dimensional analysis was validated and was found to be applicable to a second material (MCC/lactose/water).High speed imaging was also used to examine the collision behaviour of pellets during the breakage and rounding stages in spheronisation. The results confirmed that the rounding phase was the rate-determining step. The velocities of a number of tracked pellets were also quantified, and were consistently lower than the tip speed of the rotating friction plate. Bulk yield strength velocity factor, Equation (16) Pa (s m -1 ) m  Wall shear stress velocity factor, Equation (16) Pa (s m -1 ) n  p Friction coefficient, pellet-pellet - s Friction coefficient, pellet-spheroniser surface - Density kg m -3  Y0 Bulk yield strength at zero extrudate velocity, Equation (16) Pa  Y Bulk yield strength Pa  w  Wall shear stress Pa  0 Wall shear stress at zero extrudate velocity, Equation (16) Pa  Spheroniser rotational speed s -1 Acronymns API Active pharmaceutical ingredient E-S Extrusion-spheronisation MCC Microcrystalline cellulose PEEK Polyether ether ketone PIV Particle image velocimetry

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“…Spheronisation mechanisms according to (a) Rowe [14]; (b) Baert et al [1]; (c) combined deformation and agglomeration mechanism [9,12]. basis: d CE,10 = 11.3 μm; Sauter mean 30.0 μm; d CE,90 = 51.6 μm, measured using Malvern Morphologi G3 device).…”

Section: Extrudate Preparationmentioning

confidence: 99%

“…The collisions can also cause attrition, generating fines, which can attach to larger pellets (termed 'mass transfer' by [9]). Developing formulations for E-S is complicated, as the paste material must also be malleable enough to be extruded and for the pellets to be rounded.…”

Section: Introductionmentioning

confidence: 99%

Stages in spheronisation: Evolution of pellet size and shape during spheronisation of microcrystalline cellulose-based paste extrudates

et al. 2015

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The stages of extrudate breakup and rounding to form spheroidal pellets were investigated for MCC/water pastes and some MCC/water/calcium carbonate pastes using the interrupted technique reported by Lau et al. (2014). A new quantitative parameter, named 'dumb-bellity', was developed to monitor the formation and disappearance of 'dumb-bell' shaped pellets in the early stages of the rounding process. Tests using mixtures of coloured extrudates confirmed that attachment of small fragments ('fines') to the waist of pellets was not responsible for the transition from dumb-bell to more spheroidal shapes. The results confirmed the findings of Lau et al., that rounding was the rate-limiting step. Extrudates prepared with up to 20 wt.% calcium carbonate, (the carbonate representing a hard, active pharmaceutical ingredient), were subject to the same spheronisation mechanism. The time to spheronise the carbonate-containing pastes was longer, which could be related to the increased deformation resistance of these materials.

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Systematic evaluations regarding interparticular mass transfer in spheronization

Cited by 14 publications

References 10 publications

Small-scale twin-screw extrusion – evaluation of continuous split feeding

Small-scale twin-screw extrusion – evaluation of continuous split feeding

Experimental validation of a dimensional analysis of spheronisation of cylindrical extrudates

Stages in spheronisation: Evolution of pellet size and shape during spheronisation of microcrystalline cellulose-based paste extrudates

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