Milling. Both formulations were milled using the 1.0-kg bags of ribbon collected during the roller-compaction process. Because individual
bags of ribbon were used and the bypass level was well controlled, it can be assumed that any difference in the postmilling
fines level was generated by the milling process and not a result of segregation during handling of the ribbon. Also, because
the ribbon sample bags were numbered during roller compaction, the results of each milling trial can be directly compared
with ribbon solid fraction, tensile strength, and thickness values. One milling for each formulation was performed using each
of the mill types.
One major difference between the conventional mill types and the Gran-U-Lizer was the number of passes necessary to achieve
the desired particle-size distribution. The conventional mill type required only one pass to achieve the desired reduction
in particle size. The Gran-U-Lizer required several passes using different roller styles, roller speeds, and roller gaps.
According to MPE, multiple passes produce a gradual reduction in particle size and thus a low level of fines.
Granule physical property data. Particle-size distribution. Tables IV and V show the results of laser-diffraction particle-size analysis using a disperser (HELOS/RODOS, Sympatec, Clausthal-Zellerfeld,
Germany). The particle-size distributions show that the Gran-U-Lizer produced the largest particle size of all the mills tested.
However, all the milled formulations had similar distributions, as demonstrated in Figures 5 and 6. In addition, the distributions
for both formulations were broad, regardless of the mill type used.
Flowability. The MCC–DCP formulation exhibits excellent flowability across all mill types, while the MCC–lactose formulation exhibits
lower (good) flowability, with the exception of the Gran-U-Lizer, which demonstrated excellent flow based on a flow function
coefficient value of 10.1 (4). However, the larger particle size of the Gran-U-Lizer granulations did not substantially improve
the flowability of either formulation.
Thomas A. Vendola is a scientist in solids development, and Bruno C. Hancock is a research fellow in material sciences at Pfizer, Eastern Point Rd., Groton, CT 06340, tel. 860.441.4430, fax 860.441.3972.
Articles by Thomas A. Vendola