Studies On A Novel Pesticide Water Dispersible Granules

The environment and human beings were polluted seriously by benzene and high dust in traditional pesticide formulation such as Emulsifiable Concentrate(EC),Wettable Powders(WP) and Powders. It is so necessary to research and develop a novel pesticide formulation which is benzene and dust free, as well as safe. Modern pesticide formulation, such as Suspensions, Microcapsules, Microemulsions, Tablets were limited by stabilities, cost, content and processing factors. Water Dispersible Granules has been much more successful in recent years. Melting granulation was a novel technique. Its advantage was non-solvents, non-dust, non-drying step, thus the process was less energy, less time and low cost. This paper prepared a Novel Water Dispersible Granules ——Avermectin Water Dispersible Soft Granule (WDSG) and Diflubenzuron WDSG containing poloxamer188 as a binder by melt granulation. Until now, WDSG was studied in the medical field, but it didn't appear in the pesticide field. The main results as follows: 1. A water dispersible soft granules (WDSG) in the pesticide was prepared. WDSG was prepared by melting granulation in which avermectin and diflubenzuron were as two poorly soluble water model pesticides, urea as a fill, poloxamer188 as a new melting binder and sodium lauryl sulfate as a wetting agent. Under laboratory conditions, the final formulations were found and parameters on the process were researched. Impeller speed was 150～200 r·min-1, mixing time 1.5 min, temperature 80℃.Granules Screening analysis and HPLC indicated that granules size and content were uniform distributed in each fraction. The art process and quality standard were set up. Formulations toxicity was evaluated by the dipping leaves and topical application methods, EC and WP as controlled formulation, Mythimna separata Walker and Plutella xylostella L. as tested insects. The results on the LC50 showed the toxicity of WDSG was higher than or equal to the WP. WDSG dispersed in the water rapidly. Its appearance similar to paraffin and texture is soft, so we called it a novel water dispersible granules. 2. It is necessary to studied the structure, reaction mechanism between model pesticide and adjuvant on WDSG. The microstructure and characterization for pesticides WDSG were researched. Scanning Electron Microscopy (SEM) images revealed that granule was an aggregate that was coarse surface, non-crystal. X-ray powder diffraction (XRD) curve certified pesticide crystal form was not changed. Differential Scanning Calorimetry (DSC) showed that structure of WDSG was between the physical mixture and solid dispersion. Infrared (IR) analysis suggested that reaction happened among three adjuvant and pesticides or adjuvant each other caused by hydrogen bond etc. Above all, the water dispersible soft granule was a melting complex granule that was neither solid dispersion nor simple physical mixture, but similar to solid dispersion. The structure of WDSG indicated that every component was both reaction and lonely each other. This property was advantageous to coating poorly soluble water pesticides. WDSG was diluted with water and suspension obtained, coating particle appeared. Results of suspensibility index showed coating granules can prevent aggregation among particles and increase stability of suspensions. WP and water dispersible granules haven't the properties. WDSG was sprayed on the plants ,weed and insects, the adjuvant system increase pesticides bioactivity certified by bioassay results in this paper. 3. Avermectin particle was coated in the water suspension in the transmission electronic microscopy (TEM). The form reason of coating structure was studied. According to images from TEM, two new hypotheses on coat structure were advanced. The first one was hydrophilic frame structure. Lots of urea were connected and formed hydrophilic frame around the avermectin particle. Poloxamer 188 coated the particle and filled in the frame. Sodium lauryl sulfate was packed between urea and poloxamer 188 and it can stabilize the frame. The second one was petal structure made of many petals around the particle. Each petal was a micro unit that was a polymer in poloxamer 188, urea, sodium lauryl sulfate. Polymer were connected each other by the chemical bond such as hydrogen bond. Two coat structure figures were drawed up. On the basis of this paper, a patent titled "A preparation of a water dispersible soft granules in the pesticide"in P.R.China is being under processing. Application No. is 200410073362.X.