The Research Of Double-layered Microencapsule Preparation Of 20% Fosthiazate

Fosthiazate is one of the nonfumigation nematicides which was widely used at home and abroad, because of its high control effects.Due to the strong photolysis and hydrolysis,the fosthiazate garanules are easily degradated in soil, in order to achieve ideal control effect, people tend to increase the dosage of fosthiazate so meanwhile bring the risk of residues to environment and adr to crop.Microcapsule formulation can control the release of active ingredients, thus reducing the direct contact between the active ingredient and the target surface and environmental degradation factors,control effective component decomposition and volatilization, reduce frequency of drug using, prolong the lasting period, lower pesticide toxicity, prevent slips and reduce environmental pollution and so on.so fosthiazate can be prepared to microcapsules to ease the currently existed problems.The paper has successfully prepared a kind of doule-layered microcapsule containing fosthiazate through interfacial polymerization and in situ polymerization. Firstly,the stability of fosthiazate in EW of different p H were studied,secondly optimize the preparation conditions of microcapsulation,and the properties such as particle size and distribution, the coating rate, release dynamics, thermal performance,storage stability, were characterized,thereby can provide theoretical guidance and application promotion to fosthizate or other pesticides’ microcapsulation. Specific content is as follows:1. By researching the thermal storage stability of fosthiazate in EW of different p H,results got that p H=4.5 was selected the optimal p H and add 0.2% epoxidized soybean oil that help to improve the stability of fosthiazate. 2. By comparing the thermal stability of fosthiazate in different solvent,finally confirm that using 150# solvent oil as core solvent. 3. Through the comparision of particle size,distribution and coating rate of different microcapsules,results illustrate that when the inner core/shell is 10:1 and usage of out layer shell of melamine-resin is 10%, the prepared microcapsules have a optimal particle and the coating rate is high to 88.7%. 4. By comparing the emulsify effect and emulsifying stability of different emusipiers,selected D-800 as the emulsifier,and the dosage is 1.4%,by comparing the particle size,distribution conform the optimal emulsion shearing rate is 6000 rpm, emulsion shearing time is 0.5 min. 5. Influence of react temperature on the formation of inner-layer microcapsule was investigated,result comes out that at the temperature of 55℃,there is a optimal reaction time of 4 h and reacted completely.and through the observation of dispersion,selected 4894 as the best dispersant. 6. With the help of biological microscope, electron microscope, laser particle size analyzer, FT-IR Spectromete,high performance liquid chromatography（HPLC） instrument and so on,the paper established a series of quality evaluation system about the prepared double-layered microcapsules.Results illustrates that the optimal D50 of double-layered microcapsules of fosthiazate is 5.98 μm,and ranging from 0.12 μm to 15.32 μm,and have a centralized distribution.and the double-layered microcapsules have higher hardness,density and thermal stability than single-layered microcapsules.The release profile of fosthiazate from microcapsules satisfied with empirical equation C = kt ⁿ + C₀,and have a good slow-release property. Degradation test in soil show that the microcapsule of fosthiazate has a better stability than that was not microcapsulation. And the storage stability test shows the stability of the microcapsule of fosthiazate is significantly higher than the same concentration of EW. 7. Compared with fosthiazate granule,the paper measured the control effect of fosthiazate to the cowpea root knot nematode, results showed that when the dosage is 2kg/667㎡,the control effect remained above 90%,and have a higher control effect and longer persistence than fosthiazate granules.