Use of Colloidal Silica as a Separating Agent in Film Forming Processes Performed with Aqueous Dispersion of Acrylic Resins

Aqueous dispersion of polymers are going to take the place of the corresponding organic solution in the film forming process of tablets, pellets and granules, because of some definite advantages. Among the additives used in formulation techniques, talc, that is normally utilized as an antiadherent and polishing agent, presents some problems connected with its tendency to form sedimentation. For this reason, during the film coating operation, the dispersion must be always kept under constant and proper agitation, however, the danger of blocking the piping and the spraying system of the equipment employed cannot be completely avoided. On the bases of these observations, the aim of this research work is to evaluate the possibility of substituting talc with colloidal silica as separating agent in aqueous dispersion of film acrylic resins, normally used in the preparation of prolonged release systems. Results concerning fluid bed coating processes of pellets prepared by extrusion-spheronization technique have been reported, with particular attention to usable concentration of colloidal silica and to possible influence of these on the drug release characteristics of the systems obtained.