Plasticizer uptake by aqueous colloidal polymer dispersions used for the coating of solid dosage forms

The extent and rate of distribution of water-soluble (triethyl citrate, triacetin) and water-insoluble plasticizers (acetyltriethyl citrate, acetyltributyl citrate, tributyl citrate, diethyl phthalate, dibutyl phthalate) between aqueous and polymer phases in colloidal polymer dispersions were characterized by association coefficients and rate constants. A separation scheme and a high performance liquid chromatography (HPLC)-analysis were used to quantify the amount of plasticizer dissolved/emulsified in the aqueous phase and in the colloidal polymer particles as a function of plasticization (mixing) time. The rate of plasticizer uptake was a function of formulation factors such as the type and concentration of the plasticizer, and the type and solids content of the polymer dispersion. The plasticization time had a minimal effect on the rate of uptake of water-soluble plasticizers, while it had a strong effect on the uptake of water-insoluble plasticizers. The rate of the uptake depended on the water solubility of the plasticizer while the association coefficient reflected the polymer-plasticizer interaction. The rate at which plasticizers were taken up by the polymer was correlated to the film formation of the plasticized dispersions. (C) 1997 Elsevier Science B.V.