Hydroxypropyl methylcellulose phthalate

Morishita etal. (1973) encapsulated kitasamycin tartrate by emulsification and evaporation of 10% w/v solution of hydroxypropyl methylcellulose phthalate in a solution of acetone and methanol which was emulsified in paraffin oil at 5°C. The antibiotic, with a particle size of 200-500 fim, was then added with stirring and the emulsion was slowly heated to 30°C to give, after 3-4 h of evaporation, microcapsules with an enteric coat and a size of 300-700 ^m.

Encina etal. (1992) prepared a three-component phase diagram for the system hydroxypropyl methylcellulose phthalate, light mineral oil and acetone to show the region at which phase separation and microcapsules could be formed. The addition of small quantities of the surfactant sorbitan monooleate or sorbitan trioleate increased but sorbitan monolaurate decreased the region of the phase diagram where microcapsules were formed. Increasing the concentration of the surfactant did not affect the particle size appreciably, but an increase of polymer concentration increased the size of the microcapsules at all levels of surfactant concentration.

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