| In this paper, the properties, preparation method, application and development prospects were summarized, and the polymerization mechanisms were also discussed. On the basis, some research tasks were done as follows.(1) The effect of such factors as dosage of emulsifier, pre-emulsification tempreture,stirrer rotate speed on pre-emulsified liquid stability were discussed systematically. By single factor experiment, more optimum conditions was determined: dosage of emulsifier M-2 was 2.5%, monomer addition time was 30min, stirrer rotate speed was 500rmp, pre-emulsification tempreture was 40℃.(2) Using dibutyl itaconate(DBI), ethyl acrylate(EA), methyl methacrylate(MMA) and acrylic acid(AA) as raw monomer materials, and reactive emulsifiers M-1, M-2 as complex emulsifier system and potassium peroxy-sulfate(KPS) as initiator system, EA/MMA/AA/DBI quadripolymer emulsion of pharmaceutical coating acrylate with solid content of 33.82 percent was prepared by pre-emulsified seeded emulsion polymerization. Effects of reaction factors on monomer conversion and mean diameter were studied systematically, and gel ratio, stability of emulsion system and water absorption ratio of copolymer film were also studied. The copolymer was tested and characterized by particle size distribution, infra-red spectrum(IR), Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC) and Transmission Electron Microscope(TEM). DSC thermogram of copolymer showed that glass temperature(Tg) was 6.27℃. Results of GPC showed that weight-average molecular weight (M w) was equal to 7.8428×105, number-average molecular weight (M n) was 3.3373×105, and poly dispersion was 2.35. Particle morphology of the coating system was examined by TEM. Spherical particles were observed and the mean particle size was about equal to 100 nm. By orthogonal test method, the most optimum reaction conditions were as follows: emulsifier dosage was 5.0%, initiator dosage was 0.5%, AA content was 1.0%, DBI content was 0.5%. The synthetic latex had narrow size distribution and excellent properties. Results showed that water absorption ratio was reduced evidently after adding little DBI. (3) Methods of vacuum distillation-stripping and microwave irradiation post-polymersion-stripping were used separatedly to remove the residual monomer of the copolymer emulsion. Results showed that time needed was too long, energy cost was greatly and procuct quality was reduced through vacuum distillation-stripping; monomer conversion was increased and residual monomer was decreased sharply in only 6 minutes, product was little damaged by microwave irradiation post-polymersion-stripping, and its efficiency was very high.(4) Using EA/MMA/AA/DBI copolymer emulsion prepared to coat metformin hydrochloride into sustained-controlled release preparation, application property of the system was researched. Effect of coating solution concentration, thickness of coating film(weight increased of the troche), distance between spray gun and troche bed, dosage of coating solution sprayed (squirm pump rotate speed) on the drug release were studied by single factor experiment. The optimum variables in the coating process were as follows: coating solution concentration was 20% (viscidity<0.5Pa·s), thickness of coating film(weight increased of the troche) was 3.0%,distance between spray gun and troche bed was 25cm,dosage of coating solution sprayed (squirm pump rotate speed) was 0.8 rpm,post-disposal temperature was room temperature and post-disposal time was 1h.
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