Preparation Of 50% Thiamethoxam Flowable Concentrates For Seed Coating And The Study On Its Stability

With more awareness of environment and safer quality of agricultural products, the development trend of pesticide formulations is water-based, slow-released, high content and multifunction. The technology of seed treatment is paied more attention by people. High flowable concentrates for seed coating is undoubtedly considered to conform contemporary claim of agricultural development, because it is water-based, saving and easy of access.In order to obtain high thiamethoxam flowable concentrates for seed coating and promote the study on the stability, thiamethoxam was selected by studying object. Thiamethoxam was slightly soluble in water. Wetting agents, dispersing agents, film-forming agents, thickening agents and other agents were choosed and optimized by wet milling method and recurrent selection method. And then 50% thiamethoxam flowable concentrates for seed coating was prepared by the wet milling method. Further, choosed dispersing agent was selected by studying object. The adsorption isotherms of dispersing agnet on thiamethoxam, the effect of of dispersing agent on zeta potential of thiamethoxam and the effect of dispersing agent on bound water of thiamethoxam were measured. Then the stabilizing mechanism of 50% thiamethoxam flowable concentrates for seed coating was discussed. The main findings is as follows:1. The 50% thiamethoxam flowable concentrates for seed coating was obtained. The 50% thiamethoxam flowable concentrates for seed coating which contains the following fomula: thiamethoxam 50% as active ingredient; FD 3%, and BC-10 1% as wetting agent; DS-4 5% as dispersing agent; veegum 1% and xanthan gum 0.05% as thickening agent; BF 308 2.5% as film-forming agent;urea 2% as antifreezing agent;rhodamine 0.5% and cason 1% was prepared.2. 50% thiamethoxam flowable concentrates for seed coating was tested. Then the results showed that it was qualified.The active ingredient content was equal or greater than 50%. The Ph was 6.5. The viscosity was 412 m Pa·s. The grain size was 1.33μm. The forming time was less than 15 min. The dispersity was 8 level. The failure rate was 0.52%. The decomposition rate in heat store was 1.06%.3. In the laboratory, the effect on the germination potential and the germination rate of seeds were determined. The result showed that its effect on the germination potential and germination rate of cotton was discrepant with that of the blank control.The effective dose was used 150 g insecticide in 1 g seed. The further field experiment revealed that when effective dose was 3000 g/100 kg, the 50% thiamethoxam flowable concentrates for seed coating had an excellent control effect on cotton aphids in the 4- and 5- leaf stage of cotton, and the control effect was 83.94% and 53.94%, respectively. These results demonstrated applying the concentrates in the field was feasible.4. Zeta potential, sorption isotherm, amount of bound water, the rate of ostwald ripening, viscosity and orthers were measured. And then stable mechanism of suspension system was revealed. Using DS-4 in flowable concentrates for seed coating could obviously increase zeta potential of thiamethoxam. And electrostatic repulsion could prevent particle deposition. The result showed that DS-4 that had excellent adsorption isotherms, a antiabrasion layer was formed to prevent crystal growth. Dispersing agent in flowable concentrates for seed coating promoted the formation of hydrated layer. The hydrated layer was mechanical. Grain’s polymerism was prevented. Then friction and viscosity were reduced.