Method of expressing and evaluating the grinding proceedings of fine particles ground with continuous annular-stirred bead mill

We propose indices of sharpness, Ss(*) and representative diameter, Ds(*), for evaluation of grinding proceeding, both of which are defined through an integrated area along cumulative frequency curves undersize of a particle diameter distribution. We investigate dynamic changes of particle diameter distribution with these indices. It was found that these indices, Ss* and Ds* can express more accurately the subtle characteristics of the grinding process, which can not be described sufficiently with the grinding indices, Ss and Ds, defined through the Rosin-Rammler approximation. Subsequently, we evaluate the grinding proceedings for various kinds of rotor types and grinding media for the continuously stirred bead mill, with Ss(*) and Ds(*). It was found from the evaluation that the continuous annular-stirred mill, on the Spike mill, can even grind talc particles, but the cumulative diameter distribution becomes broader. Ss(*) and Ds* can express more accurately that the Spike mil, with the narrower clearance between rotor and mill vessel wall, using smaller zirconia beads can grind calcium carbonate particles most satisfactorily.