界面聚合制备乙草胺微胶囊及其杂草控制效果和环境残留

【目的】通过界面聚合法制备乙草胺微胶囊(MC),研究乙草胺微胶囊与控制效果和环境残留药量之间的相互关系。【方法】以苯乙烯、甲基丙烯酸丁酯为油溶性单体、与乙草胺混合得到油相,双丙酮丙烯酰胺为水溶性单体,聚氧乙烯山梨醇酐硬脂酸酯为乳化剂,在水包油乳液中通过界面聚合方法制备得到乙草胺微胶囊。通过场发射扫描电镜、动态光散射、红外光谱等手段对乙草胺微胶囊形态结构、粒径分布、表面化学基团等性能和结构进行表征。同时,通过对乙草胺微胶囊释放动力学性能、乙草胺释放后在土壤中的残留动态以及对杂草的防效等的研究,探讨其释放机制、环境行为和防治效果之间的关系。【结果】乙草胺微胶囊呈球状,平均粒径为1.552μm,负载效率为60%,配方中乙草胺的含量为20%。在室内搅拌速度为100 r/min,温度20—45℃下保持pH为7.0时,第5天乙草胺的累积释放率约为50%—70%,在第10天为60%—90%,第30天为80%—100%。在保持温度恒定(25℃),搅拌速度为100 r/min的条件下,在5.0—9.0的pH范围内,乙草胺的累积释放率在第5天为60%—70%,在第10天从70%增至接近80%,在第30天为约80%,在第40天接近100%。乙草胺微胶囊的释放速度随着温度和pH的增加而加快。禾本科杂草和总杂草防治效果在第20天分别为80.2%—95.4%和67.8%—82.1%,第40天为82.2%—92.4%和70.2%—80.9%,第60天为87.0%—97.2%和62.6%—91.3%。在第60天的鲜重防效分别为90.1%—98.0%和70.3%—88.7%。对于常规乙草胺乳油(EC)制剂来说,对禾本科杂草和总杂草防治效力第20天分别为80.4%—90.2%和54.8%—76.1%,第40天为83.0%—91.2%和61.4%—79.8%,第60天分别为81.1%—88.3%和71.2%—84.0%,在第60天的鲜重防效分别为80.3%—83.4%和65.9%—74.0%。在大田试验中,土壤中乙草胺的残留量随时间延长逐渐降低,乙草胺微胶囊的活性成分含量高于乙草胺乳油,这确保乙草胺微胶囊延长了防治时间,增强了防治效果。【结论】微胶囊载药系统可延伸到其他亲脂性农药制备中。与乳油相比,农药微胶囊可以有效提高对杂草的控制效力,减少除草剂的喷用量,减轻因为大量施药对环境造成的压力。

Preparation of Acetochlor Microcapsules by Interfacial Polymerization and the Environmental Behavior and Control Efficacy

【Objective】 The objective of this study is to prepare acetochlor microcapsules by interfacial polymerization and highlight interrelation among these formulations, biological effect and environmental effect. 【Method】 The acetochlor microcapsules were prepared by interfacial polymerization method with styrene, butyl methacrylate, and diacetone acrylamide in the O/W emulsion. The performances of acetochlor microcapsules such as morphological structure, size distribution and chemical group were characterized by FESEM, DLS, IR and so on. Meanwhile, through study on the release performance of acetochlor microcapsules, the acetochlor residues in soil and the control efficacy on weeds, connection among the release mechanism, environmental behavior and control efficacy were investigated. 【Result】The prepared acetochlor microcapsules are spherical, the average particle size is 1.552 μm, the loading efficiency is 60%, and the content of acetochlor in formulation is 20%. Under laboratory conditions, when pH values kept at pH 7.0, the cumulative release rates of acetochlor were about 50% to 70% on the 5th day, 60% to 90% on the 10th day, and 80% to nearly 100% on the 30th day from 20℃ to 45℃. In the pH range of 5.0 to 9.0, the cumulative release rates of acetochlor were from 60% to 70% on the 5th day, from below 70% to nearly 80% on the 10th day, about 80% on the 30th day, and nearly 100% on the 40th day. The release of acetochlor microcapsules (MC) was accelerated with the increase of temperature and pH. The grassy weeds and total weeds control efficacy were 80.2%-95.4%, and 67.8%-82.1% on the 20th day, 82.2%-92.4%, and 70.2%-80.9% on the 40th day, and 87.0%-97.2%, and 62.6%-91.3% on the 60th day; fresh weight control efficacy were 90.1%-98.0% and 70.3%-88.7% on the 60th day. For the conventional acetochlor concentrated emulsion, the grassy weeds and total weeds control efficacy were 80.4%-90.2%, and 54.8%-76.1% on the 20th day, 83.0%-91.2%, and 61.4%-79.8% on the 40th day, and 81.1%-88.3%, and 71.2%-84.0% on the 60th day, respectively, and fresh weight control efficacy were 80.3%-83.4% and 65.9%-74.0% on the 60th day. Under field conditions, the amount of acetochlor in the soil gradually reduced over time, and the active ingredient amount of acetochlor microcapsules was higher than that of acetochlor emulsifiable concentrate (EC), which extended the control time and ensured acetochlor microcapsules a better control efficacy.【Conclusion】This delivery carrier may be extended to other lipophilic pesticide in the future. At the same time, more pesticide active ingredient for microcapsules than that of EC can improve the weeds control efficacy, and reduce the number of spraying and amount of pesticide for EC, and relieve the pressure on the environment.