Preparation For Acetochlor Microcapsule And Property Characterization

Microcapsules have many advantages such as prolong controlling effect, improving using efficiency, abating toxicity and harmfulness, reducing environment pollution, and so on. In recent years, more and more attention is paid to it. Acetochlor Microcapsule with a urea-formaldehyde resin wall were prepared by an in-situ condensation polymerization reaction in aqueous medium, and release rule was study by chromatogram analysis and bioassay.1. The Screening of additives: Microcapsules are prepared using polyelectrolyte macromolecules SMA as emulsifier witch content is 3%. Microcapsules had a good surface morphology. Based on encapsulation, microcapsule suspension is prepared by adding a suspension agent. The quality specifications, including suspension rate and encapsulation rate, were measured after Acetochlor 30% CS was prepared by an in-situ polymerization reaction in aqueous medium. In additional, the suspension rate was above 85%. The changes of the content and suspension rate were determined too. After hot and cold storage, Microcapsule encapsulation rate is still above 95%, the suspension rate was above 80%, water separating proportion is less than 2%.It was showed that the product had good stability.2. For the screening the preparation system such as prepolymer conditions, solvent, acid catalyst, core/wall material ratio of microcapsules, the optimal conditions were as follows: xylene content was 3% as solvent, dilute hydrochloric acid as catalyst, and the dosage of wall material was 3%.Under these conditions, microcapsules could be prepared with good surface morphology with the mean particle size of 5~10μm. Encapsulation ratio was above 95%. The study of mean particle size, distribution and encapsulation ratio showed that the microcapsules particle size and the size distribution decreased with the dosage of emulsifier increasing, then decreased with the dosage of emulsifier continue to increase. The mean particle size of microcapsules decreased with the appropriate extension of acidification time. Microcapsules with high encapsulation were prepared by souring 90 min, curing 90min at 60℃.3. Emulsification and charge effects were studied by the system of surface tension and Zeta potential. In different emulsifier system, the surface tension was the lower; the emulsifying ability of the emulsifier is stronger, and the droplet size is smaller. Microcapsules with UF-resin via in-situ polymerization with polymer electrolyte SMA as emulsifier could form double electric layer, and can effectively make the wall material get condensation reaction on the droplet surface, inhibiting the side reaction in the aqueous phase occurs. In the process of preparing microcapsules, zeta potential after emulsification is much larger than the one after encapsulation. It was showed that emulsifier was encapsulated in microcapsules. SMA with different molecular weight had a greater impact on encapsulation. It can be obtained high encapsulation efficiencies by using SMA molecular weight is 5000.4. Experiments were conducted to evaluate the efficacy of acetochlor microcapsules suspension to barnyardgrass and the safety analysis to maize and soybean was also proceeded. The results showed that the initial efficacy of acetochlor microcapsules suspension to barnyardgrass was inferior to acetochlor emulsifiable concentrate. After 30 days, the herbicidal activity of acetochlor microcapsules suspension reduced slowly with longer effective duration. The results of safety analysis to maize and soybean showed that the acetochlor microcapsules suspension was safer than that of acetochlor emulsifiable concentrate. The present data support the conclusion that acetochlor microcapsules suspension has excellent sustained release character, and decreases the phytotoxicity effectively.