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Gran-U-Lizer. The Gran-U-Lizer is a nonattrition size-reduction mill. It uses roller-mill technology that contols particle-size reduction
through roll-surface texture (i.e., roll type), roll speed, and roll gap. According to MPE, the Gran-U-Lizer operates through
the use of shear, in contrast to impact used by conventional size-reduction equipment. The Gran-U-Lizer achieves a narrower
particle-size distribution with fewer fines by eliminating the attrition inherent in other milling designs. The laboratory
model Gran-U-Lizer requires several passes through the rolls using various roll types, roll speeds, and roll gaps to achieve
the desired particle-size distribution. All milling trials using the Gran-U-Lizer roller mill were conducted at MPE's Chicago
site.
Two IR, dry-granulation placebo formulations (see Tables I and II) were selected to evaluate mill performance. Roller-compaction
conditions were established using the Gerteis Mini-Pactor roller compactor to produce ribbon at a target solid fraction of
0.7 at an approximate thickness of 2.5 mm. Ribbon was manufactured from both formulations and characterized for solid fraction,
tensile strength, and thickness. Roller-compaction bypass was measured to establish the fines level within the compacted ribbon
before milling.
Ribbon characterization
Figure 1: Measurements of ribbon dimensions. (AUTHORS)
Solid fraction. Ribbon samples were prepared by cutting the compacted ribbon into rectangular shapes of approximately 10 x 22 mm using a
jeweler's table saw. Figure 1 demonstrates how the ribbon sample was prepared. The cut ribbon sample was measured using calipers
to determine the envelope density.
The solid fraction of each ribbon sample was determined according to a relationship that can be expressed by the following
equation:
in which w is the ribbon width, l is the ribbon length, t is the ribbon thickness, m is the ribbon mass, Vs is the volume of the roller serrations, and ρt is the true density of the material.
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
