毒死蜱微囊悬浮剂的制备及微囊化条件的优化

以脲醛树脂为壁材,采用原位聚合法制备了20％毒死蜱微囊悬浮剂,探讨了影响微囊粒径大小及分布的因素,优化了微囊化条件,并就其与毒死蜱乳油对韭菜迟眼蕈蚊Bradysia odoriphaga幼虫的毒力进行了对比。结果表明,选用苯乙烯-马来酸酐共聚乳液(SMA)为分散剂(质量分数为总体系的2.5％),乳化条件为1 500 r/min搅拌30 min,60 min内调节体系pH值至2.5,反应后期升温至45℃,在此条件下制备的毒死蜱微胶囊外形较好,平均粒径为8.9 μm,分散系数为0.182 6,包封率高达99.54％。毒力测定结果表明,乳油和微胶囊对韭菜迟眼蕈蚊幼虫的初始LC50值分别为2.05和 3.02 μg/mL;而在自然环境中放置32 d后,乳油对该虫的毒力下降较快,LC50值为100.23 μg/mL,而微囊悬浮剂毒力仍保持较高水平,LC50值为15.63 μg/mL。表明毒死蜱微囊悬浮剂兼具速效性高和持效期长的优点。

Preparation of Chlorpyrifos Aqueous Capsule Suspension and Optimization of Encapsulation Conditions

UF-resin was used to encapsulate chlorpyrifos by in-situ polymerization. The effect factors on particle size and distribution of capsule were also investigated. The optimal conditions were as follows:The dosage of dispersant styrene-maleic anhydride(SMA)emulsion was 2.5％ of total system,emulsified for 30 minutes by stirring at the rotating speed of 1 500 r/min,adjusted to pH 2.5 in 60 minutes,the temperature of condensation reaction was controlled at 45℃. The mean diameter of microcapsule suspension was 8.9 μm,and the coefficient of its variance were 0.182 6,which formed satisfied particles size and distribution under the optimum conditions. Its encapsulation efficiencies were 99.54％. Compared with chlorpyrifos EC,the chlorpyrifos CS showed excellent initial efficacy and long residual activity. The original LC50 of chlorpyrifos EC and CS were 2.05 μg/mL and 3.02 μg/mL respectively against 3rd-instar larvae of Bradysia odoriphaga,and their residual LC50 (32 d) under natural conditions were 100.23 μg/mL and 15.63 μg/mL,respectively.