Gibbsite powder was ground in air by a double rotating cylinders mill under three different conditions in order to investigate the effect of grinding condition on the characteristics of ground products. Case-1 in which two cylinders are rotated in reverse directions gave higher impact energy of balls than the other cases (Case-2: batch operation and Case-3: continuous operation) in which only the inner cylinder is rotated to attain the same amorphization of the material. The powders produced in Cases-2 and 3 had a larger specific surface area than that by Case-1. Heat generation rate during the dissolution in water of the powder produced by Cases-2 and 3 was much faster than that by Case-1. The reactivity of powder produced by Cases-2 and 3 was higher than that by Case-1.

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Determination of refractive index of particles is one of the most important and difficult problems in the measurement of particle size distribution with laser diffraction and scattering methods. In this study, we proposed a new method to determine both particle size distribution and the refractive index of particles. The method was applied to several sample powders (polystyrene latex, glass beads, etc.) and the usefulness of this method was confirmed.

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This is a fundamental research on the quantitative evaluation of wet kneaded mass prepared by a paddle type kneader together with the analysis of kneading and the following extrusion granulation processes. A compaction tester of wet kneaded mass has been newly developed and the compression properties of mass are characterized by pressure transmission between the upper and lower punches of the tester. Dispersion condition of a binder liquid among the wet kneaded mass prepared under various kneading times is investigated. Extrusion pressure through a single hole on the lower punch is also measured. The pressure transmission is found to have a linear relationship between the dispersion of binder liquid and the extrusion pressure. This result leads to the conclusion that the proposed method provides the generalized measuring means of the wet kneaded mass. An extrusion granulation by a dome-type extruder is conducted using the wet kneaded mass and physical properties of the extruded pellets, such as friability, specific surface area and disintegration time, are investigated. Good linearity can be found between the pressure transmission and the physical properties of the pellets. As the results of these findings, the kneading condition, i. e., the dispersion of binder liquid among the wet kneaded mass can be understood and the physical properties of pellets prepared by the extrusion granulation can be predicted by the pressure transmission measured by our newly developed compression tester.

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