抄録
Concerning the new microencapsulation method based on surface neutralization of enteric polymers, the effect of polymer species on microcapsule (MC) properties was studied. First, the encapsulation of crystal aspirin was performed at 40°C using nine kinds of enteric polymer. It was known that cellulose derivative polymers such as hydroxypropyl methylcellulose acetate succinate (HPMCAS-L, -H), cellulose acetate phthalate (CAP), hydroxypropyl methylcellulose phthalate (HP-55) and carboxymethylethylcellulose (CMEC) produce effective membrane, while synthetic acrylate polymers such as methacrylic acid-methacrylic acid methylester (Eudragit L, S) and methylacrylate-methacrylic acid copolymer (MPM-05) do not.Then, microencapsulation was performed changing the preparation temperature from 10 to 60°C for HPMCAS-H, -L, CAP, CMEC and Eudragit S. The polymer content in MCs generally increased by raising the temperature with the exception of HPMCAS-H. In HPMCAS-H, the polymer content was at a miximum around 40°C. The amount of consumed core aspirin generally increased with the increase of the preparation temperature. As a rule, the amount was the least in polymers which need the least alkali for their dissolution into water. The dissolution depresison of aspirin into the JP XI 1st fluid showed various tendencies due to the polymer species. Eudragit S hardly depressed at any preparation temperature. CMEC and HPMCAS-H depressed maximally around 30-50°C. CAP depressed the most with the increase of the temperature.In order to elucidate these phenomena, phase separation behaviors were observed for the five polymers at various pHs and temperatures. As a resulets, the state of the polymer phase around pH 2.0-2.5 concerned well with the properties of the MCs.
