ENCAPSULATION BY INTERFACIAL POLYCONDENSATION .3. MICROENCAPSULATION, THE INFLUENCE OF PROCESS CONDITIONS ON WALL PERMEABILITY

Microcapsules are produced by immersing uniform sized droplets of an organic phase into an aqueous solution. The process of polycondensation of terephthaloyldichloride (TDC), dissolved in the organic phase, and diethylenetriamine (DETA) in combination with ethylenediamine (EDA) or hexamethylenediamine (HMDA), dissolved in the aqueous phase, was studied. This process produced the capsule wall at the interface; the capsule diameter varied between 0.5 and 1 mm. The influence of the concentration ratio of TDC and DETA, the addition of EDA or HMDA, their concentration relative to the DETA concentration in the aqueous phase and the kind of the organic phase on the diffusion coefficient of DETA through the polymer produced was measured. The decrease of the TDC concentration in the capsules and the growth of the capsule wall could be described by the same relationship as derived from macrocapsules. Also the influence of the TDC/DETA concentration ratio was in agreement with the results obtained for macrocapsules. Addition of diamine to the aqueous phase reduces the permeability of the capsule wall; an increase of the ratio of the diamine and the triamine concentration also reduces the permeability.