Studies On The Preparation Of 20% Chlorpyrifos CS And Its Analytic Methods

Compaerd with other pestlcide formulations, capsule suspensions(CS) have many advantages such as long effective duration, high utilization rate, effective components stability, low toxicity, safe to user and environment,etc. Chlorpyrifos is a lower toxicity, organicphosphorus insecticide which has replaced the traditional high toxicity insecticide such as methamidophos and has been widely applied for controlling agricultural and sanitary pests. However, chlorpyrifos is normally processed in formulation emulsifiable concentrate(EC), which consumed a lot of organic solvent, and resulted in environment pollution and resource waste. While chlorpyrifos could be processed in microcapsules formulation(e.g. capsule suspensions(CS) it can avoid all the problems above.This paper studied the preparation conditions of 20% chlorpyrifos capsule suspensions using urea-formaldehyde resin as wall material via in-situ polymerization method, and established a analytic method of chlorpyrifos capsule suspensions products. We successfully prepared 20% chlorpyrifos capsule suspensions by optimizing preparation conditions and using proper processing adjuvant. The main results were as follows:1. A variety of solvents were used as core solvents in the preparation of chlorpyrifos capsule suspensions.Xylene was chosen as final core solvent by comparing the solubility of chlorpyrifos in different solvents, the stability and the shape of the prepared microcapsules.2. Different dosage of urea-formaldehyde resin as wall materials to prepare chlorpyrifos microcapsules suspension were tested. By comparing the mean diameter distribution, encapsulation efficiency of the microcapsules and the releasing rate of chlorpyrifos from the prepared microcapsules, 12% UF-resin was confirmed as best dosage in the preparation. The mean diameter, coefficient of variance and the entrapment efficiency of the prepared microcapsules was uniform, the microcapsules also had a good releasing properties.3. By comparing the mean diameter and coefficient of variance of prepared microcapsules, emulsifier A was chosen as the best emulsifier .The result show that 2% emulsifier A was suitable.4. We investigated the influence of different emulsification time and emulsification stirring speed to the mean diameter, coefficient of variance and releasing rate of prepared microcapsules. It indicated that 15 minutes emulsification time and emulsification stirring speed at 1500 r /min were proper.5. The study showed that when we adjusted the pH of the reaction system to2.0 and kept it in 60 minutes, the mean diameter, coefficient of variance and the encapsulation efficiency of the prepared microcapsules was satisfied.6. We studied the solidifying time and solidifying temperature on encapsulation efficiency of the prepared microcapsules, it could get high encapsulation efficiency when solidifying temperature was at 50℃for 1.5h.7. By comparing the mean diameter, dispersity and suspension rate of the prepared formulation, the optimizing formula was dispersant T1 as chosen dispersant (the dosage was 1%), wetting-dispersing agent R2 as chosen wetting-dispersing agents (the dosage was 3%).8. By checking the stability, pourability and dispersity of the prepared formulation, we chose the thickening agent we chose were thickening agent K1 and K2, the dosage of K1 and K2 were 0.15% respectively.9. By checking the appearance, flowability and suspension rate of the prepared formulation after freezing storage test, we chose ethylene glycol as antifreezing agent (the dosage was 5%).10. We set up the quality evaluation method of the prepared 20% chlorpyrifos capsule suspensions in this paper. The results showed that all the tested quality index of the prepared product (the mean diameter ,coefficient of variance of microcapsules, entrapment efficiency, releasing rate, suspension rate, pourability, bubble volume, dispersity, heat storage stability, low temperature storage stability and centrifugal stability of the prepared formulation) were satisfied.