Preparation Of Pirimiphos-methy CS By Complex Coacervation

Pesticide microcapsule is a sort of international environmental pesticide formulations with the broad development prospects. Therefore, this dissertation introduces the pirimiphos-methy CS prepared with the method of complex coacervation and discusses varieties of factors which impact pirimiphos-methy CS in the whole of production. In addition, in terms of function, it compares the difference among three preparation methods. The main research results are following:1. Preparation of pirimiphos-methy CS by complex coacervationPirimiphos-methy CS was prepared with gelatin and arabic gum by complex coacervation. And then, the effects of reaction conditions on the average particle size and encapsulation efficiency of microcapsules were investigated, the optimal conditions were as follows:emulsification time was6min, the ratio of core to shell was5:1, the mixing speed was600r/min, complex coacervation pH was4.1, reaction temperature50℃, reaction time60min, curing agent was3ml and curing time was90min. The result finally suggested that encapsulation efficiency of microcapsules was higher than90%and the average particle size was lower than5pm under this optimized condition.Though identifying the dispersant wetting agent and thichkening agent under the optimally confirmed condition, we determined the best addition agents formula:TERWET1004(wetting agent) was1.5%, TERSPERSE2700(dispersant agent) was3%, Aluminum Magnesium Silicate (thickening agent) and Adhesive Xanthan XG (thickening agent) were0.2%and1.0%respectively, Ethylene Glycol (freeze proof agent) was5%, Antifoaming Agents accounted for0.1%and double distilled water accounted for100%. This result showed that encapsulation efficiency of microcapsules prepared under above conditions was still approximately90%after the thermal and cold storage test, the suspension percentage of agents was also more than90%, hence it indicated that the agent owned so favourable physical and chemical features that helpful to store.2. Morphologic observation, bioactivity, release property and cost comparison of the three sorts of microcapsules (1) The results of morphologic observation of microcapsules suggested that microcapsule with wall material of gelatin and arabic gum prepared by complex coacervation had a uniform distribution in aspect of particle size and well-regulated globular shape as same as UF-resin microcapsules prepared with In-situ polymerization, but polyurea microcapsule prepared with Interfacial Polymerization had a comprehensive particle size and irregular shape. However, all the microcapsules prepared by three methods had qualified suspension concentrate performance.(2) The results of testing bioactivity showed that pesticide effect of capsule suspension was not better than EC in24hours but the difference between them was not remarkable, which were used by tribolium castaneum as model insect to test this experiment. Besides, the toxicant value of Microcapsule SC prepared with the three different methods did not have an obvious decline with the extension of time. The LC5o value of microcapsule SC with the wall materials of gelatin and arabic gum rose from26.36mg/L to43.38mg/L till28days, and the LC50value of polyurea CS went up from28.51mg/L to53.34mg/L, but the LC50value of missible oil just ascended from21.42mg/L to107.59mg/L, which indicated that there were better slow-releasing potential among the three CS prepared by the three different methods than missible oil. It contributed to the better comprehensive prevention and control effect with less of dose.(3) The results of testing slow-releasing potential of microcapsule manifested that gelatin and arabic gum microcapsules prepared with Complex Coacervation with little partical size and uniform distribution were as same as UF-resin microcapsules prepared by using the method of in-situ polymerization, which were steady, less fluctuant and time during the release process. But polyurea microcapsules prepared with interfacial polymerization owned the large partical size, non-uniform distribution and uneven wall thickness, it lead to the unstable release speed, larger fluctuation and slightly long release time.(4) The results of comparing the costs of three microcapsules indicated that the cost variance was not notable.