Effect of Process Variables on the Properties and Binder Distribution of Granules Prepared in a Fluidized Bed.

Abstract

A lactose-cornstarch model system with hydroxypropyl methylcellulose 2910 (HPMC 3cP) as a binder was used to evaluate the effects of several process variables (moisture level, spray feed rate and drying air flow rate) on the particle size distribution of granules prepared in a fluidized bed using a dry mixing method of binder addition. Moisture levels were controlled via an infrared moisture sensor. The distribtuion of binder in different sized fractions of granules was also determined by measuring the contents of the methoxyl group. Moisture level was the most important factor for granule growth, and higher moisture levels increased the granule size. The time for which a given moisture level was maintained and the fluidizing air flow rate had little effect on granule size, size distribution, binder distribution or apparent density. This implies that mixing is efficient during fluidized bed granulation by the dry mixing method and that binder behavior is mainly determined by the moisture level of the wet mass. It was concluded that if a fixed moisture level is maintained during fluidized bed granulation with the dry mixing method of binder addition, variation of the other operational conditions should have little effect on the consistency of the product.