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 corr esponding organic solution in the film forming process of tablets, pel lets and granules, because of some definite advantages. Among the addi tives used in formulation techniques, talc, that is normally utilized as an antiadherent and polishing agent, presents some problems connect ed with its tendency to form sedimentation. For this reason, during th e film coating operation, the dispersion must be always kept under con stant and proper agitation, however, the danger of blocking the piping and the spraying system of the equipment employed cannot be completel y avoided. On the bases of these observations, the aim of this researc h work is to evaluate the possibility of substituting talc with colloi dal silica as separating agent in aqueous dispersion of film acrylic r esins, 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.