Study On The Preparation And The Release Mechanism Of Acetochlor Microcapsules Produced By Interfacial Polymerization Method

Acetochlor is among the most widely used herbicides in the dryland. Conventional formulations have poor efficiency due to short durations. In field applications, the spray frequency and the dose of the herbicide were increased heavily to prolong the duration, which in turn casued phytotoxicity and serious pollution to the environment. Under this conditions, the prepration of the acetochlor microcapsules was studied in order to achieve longer duration were prepared by interfacial polymerization method. Factors of processing affecting microcapsules formulations, characterization and the release mechanism were investigated, and the weeds-controlled efficiency of acetochlor microcapsules was studied, as well. Results are summarized as follows:1. The optimum conditions to prepare acetochlor microcapsulesAcetochlor microcapsules were prepared by interfacial polymerization method with styrene, butyl methacrylate, and diacetone acrylamide as the wall materials and acetochlor as the core. The preparation conditions were studied by single factor and orthogonal experiment method. Optimum preparation conditions were as follows:a ratio of core to wall was3:1, the emulsifier was a T-60with the amount of2.5%(m/m), the reaction temperature was75℃Cand the stirring speed was500r/min.2. Establishment of acetochlor-detecting methodAcetochlor was detected by UV spectrophotometer and HPLC. The conditions were as follows: a mobile phase was composed of methanol:water was89:11(v/v), the detective wavelength was214nm, the column temperate was30℃, the flow rate was0.6mL/min and the injection volume was20uL. The retention time of acetochlor was7.010min.3. Acetochlor microcapsules were characterized as qualifiedThe properties of acetochlor microcapsules were characterized using Biological microscope, Scanning electron microscopy and Laser particle size analyzer. Acetochlor microcapsules were spherical with quality as follows:a average particle size of1.552μm, a encapsulation efficiency of 93.25%, a loading efficiency of64.29%, a suspension rate of97.64%and a content of acetochlor of19.43%. Meanwhile, good dispersion and storage stablity under hot/cold conditions were also confirmed. All quality parameters lists above well match the standard of pesticide microcapsule.4. Release mechanism of acetochlor microcapsulesUnder laboratory conditions, the release kinetics of acetochlor microcapsules was investigated by dialysis bag method. The releasing speed of acetochlor was accelerated with the temperature increase. The maximum speed was achieved at temperatures ranging from53.1-55.4℃. Additionally, the releasing pattern complyed with Fickian diffusion model. The releasing speed was consistency with the pH value, the releasing speed was higher under neutral and alkaline conditions than under acidic conditions, and the releasing pattern complyed with Fickian diffusion model.Under the field condition, soil residues of acetochlor gradually reduced. Generally, soil residues amount of active ingredient of acetochlor microcapsules were higher than that of acetochlor emulsifiable concentrate. After20-60days, the amount of active ingredient of acetochlor microcapsules was1.24-2.83times more than that of acetochlor emulsifiable concentrate. Meanwhile, the half-life period of acetochlor microcapsules,41.5-70.3d, was much more (2.50-4.23times) than acetochlor emulsifiable concentrate,16.6-18.9d.5. Acetochlor microcapsules showed a better performance on weeds controlAcetochlor microcapsules had a better sustained-release performance than acetochlor emulsifiable concentrate in both potted and field experiments. In the potted experiment, when acetochlor microcapsules were applied at a dose of600g.ai/hm2, the height inhibition rate of Echinochloa crusgalli (L.) Beauv. was significantly higher than that of acetochlor emulsifiable concentrate at the same dose after21d. In the field, after40-60days, the weeds control efficacy of acetochlor microcapsules was statistically higher than that of acetochlor emulsifiable concentrate, at the dose600-750g.ai/hm2.