To develop a process for manufacturing micro-capsule of cornstarch covered with thin lactose film, experimental work on binder1ess granulation and coating using cornstarch and lactose powder as feeding materials was started. However this work had to be stopped unwillingly because of insufficient mechanical strength of granules in the coating process. Consequently, the relations between the properties (size distribution, mechanical strength) and yield of granules and operational variables were examined by performing binderless granulation experiments for obtaining fundamental findings as a preliminary stage of the development of this new process. The summary of the results is described as follows.
1.Experimental apparatus and conditions : A two dimensional tapered-fluidized bed column (spouted bed type) made of acrylic resin as used for granulation experiments. The thickness and taper angle of the column were 10mm and 15 degrees. The gas inlet was 10mm square. The column wideness was var
iable from 150mm to 500mm. Stainless steel mesh with opening of 44 mu m was used as gas distributor and air was used as fluidizing gas. Alumina particles with narrow cut of 0.3, 0.6 and 1.0 mu m were used as feeding powder. Granulation experiments were conducted at various operational conditions such as charge amount of powder, gas velocity, operation time and column wideness. Granule size was measured by sieving and yield of granules was obtained by weighing the amount of granules discharged from the column after each run.
2.Results : (1) The granules were spherical and their size distribution obeyed log-normal distribution. (2) The granules having a required minimum size could be obtained by utilizing classification phenomena in the freeboard region of the column. (3) When the smooth fluidizing state is ensured, the granules with almost similar physical properties were obtained irrespective of operational variables such as charge amount of powder, gas velocity and bed wideness. (4) For relatively large particLes (1.0 mu m particles), the channeling as an obstruction of granulation is liable to set in. (5) Apparent compressive strength of granules which was almost independent of the operational conditions, decreased with the increase of granule size and increased with the decrease of feed particle size. Less