A Novel Pesticide Formulation, Micro-emulsifiable Granule’s Preparing And The Mechanism Of Its Micro Emulsion Formation And Stability

The feasibility to formulate oil-soluble pesticide technical material (TC) into a novel solid formulation, micro-emulsifiable granule (MEG) was studied. The test pesticides were triazophos, cypermethrin and abamectin to represent oil-soluble pesticide TC, including liquid TC, low melting point TC and high melting point TC, respectively. Triazophos MEG as object of study, the mechanisms of micro emulsion formation and emulsion stability were researched.By testing the solubility, dissolution rate and oil absorption rate, sodium benzoate, lactose, mannitol, magnesium sulfate and water soluble starch were selected as carriers of MEG. And a mixture, C12was obtained by uniform design of experiments with mixtures U11(105). The oil absorption rate of C12was56.2g oil per100g carrier. Specific surface area and pore size parameters test showed the parameters which had significantly influence on carrier’s oil absorption rate were BET surface area, total area in pores, BJH desorption cumulative surface area of pores, BJH desorption cumulative volume of pores and total volume in pores.According to U10(108), triazophos300ME (not containing organic solvent) were prepared in order to screen surface active agent (SAA) used for the preparation of MEG. A mixture SAA of non-ionic surfactants,602#+EL40+JM6140(named SAA-6EJ), was screened out by standard regression coefficient (SRC) of Xi. Triazohpos100MEG which contains10%SAA-6EJ was successfully formulated when using mannitol or MgSO4conjoined citric acid as carrier, and its minimum value of D5o was40.64nm. D50of triazohpos150MEG containing8%SAA-6EJ was75.49nm. A mixture SAA of anionic surfactant and non-ionic surfactant,500#+602#(named SAA-56), was screened out by SRC of Xi and XiXj. Triazophos100MEG containing SAA-56was successfully formulated when the carrier was a mixture of lactose or mannitol or water soluble starch and citric acid. D50of triazohpos150MEG containing8%SAA-6EJ was54.2nm. Triazophos300micro-emulsifiable gel (MGL) was formulated using the mixture SAA of anionic surfactant and non-ionic surfactant, FS7PG+602#(named SAA-F6) or HASS7+602#(named SAA-H6), which screened out by SRC of XiXj And triazophos100MEG could be successfully formulated using SAA-F6, if the carrier was MgSO4or C12. Triazophos100MEG also could be successfully prepared using SAA-H6, when the carrier was the one of lactose, mannitol, water soluble starch, MgSO4, or C12. D50of triazophos150MEG containing10%SAA-H6was63.69nm. They were discovered in experiments. First, in same emulsion, the change of D50negatively correlated with the change of transparency or transmission. Second, although the D50of one emulsion was smaller than another emulsion, its centrifugal stability might not higher than that of another. Third, Nano emulsion could maintain stability after centrifuge5min under relative centrifugal force (RCF)100g, and the critical RCF between nano emulsion and micro emulsion would change along with the change of emulsifier system.According to U8(63), cypermethrin100MEG containing10%SAA were prepared by melt-blending process. The optimum combination of FS7PG,500#and EL60, optimized by Partial Least Squares Regression (PLSR), was used as emulsifier of cypermethrin100MEG, and the value of D50was51.45nm. Two surfactants, FS7PG and EL60, were screened out by SRC. The test results of proportional method were showed cypermethrin100MEG could be successfully formulated using FS7PG and EL60as emulsifiers when the ratio of FS7PG/EL60between1/9and10/0, and the least value of D50was59.91nm when the ratio was9/1. Lambda-cyhalothrin100MEG, bifenthrin100MEG, bifenthrin50MEG and alpha-cypermethrin100MEG could be successfully formulated using the recipes of cypermethrin100MEG.According to L9(34), abamectin20ME were prepared. And the optimum combination (named SAA-TJH) of TSP16, JM6180, and HASS7was obtained when the independent variable was transparency temperature section of ME. When the carrier was the mixture of benzoate, MgSO4and lactose, D50of abamectin20MEG containing10%SAA-TJH was79.54nm. According to U11(114), abamectin20MEG were prepared using benzoate as carrier, and the proportion of602#, NP10-P, AEC903and NP-10was optimized by PLSR. When the optimum combination was used as emulsifier of abamectin20MEG, D50was12.13nm. There were three combinations,602#+NP10P+NP10,602#+NP10and NP10P+NP10, screened out by SRC. Using their optimized proportion, D50of abamectin20MEG (10%SAA) was44.31nm,14.22nm, and14.04nm, respectively. Ivermectin MEG and emamectin benzoate MEG could be successfully formulated using the recipes of abamectin20MEG.The formulation process of MEG was rotary extruding granulation or fluidized granulation. The physical and chemical properties of MEG preparations meet the requirements of application. In the thesis, the test items and corresponding values for product registration quality requirements were proposed, and mechanical stirring method as the test method of emulsified time, one of test items, was established.The bioassay test results of armyworm (Leucania separata) showed that the bioactivity of triazophos150MEG was higher than that of triazophos100MEG, triazophos150ME and triazophos150EC, and there were no significant differences of bioactivity among later3preparations. There were no significant differences of bioactivity among cypermethrin100MEG, cypermethrin100ME, cypermethrin100EC, but they were significantly better than of cypermethrin100EG. If abamectin was formulated as MEG or micro-emulsifiable powder, its bioactivity was no significant difference with that of ME, but significantly better than that of EC. And it was found that the formulation would not affect the biological sensitivity level of target organism to pesticide active ingredient by comparing the slopes of toxicity regression equations.Triazophos MEG was selected as the research object. The effect of water hardness, tap water, water temperature and carrier on the micro emulsion formation after MEG diluted using dynamic light scattering technique and static light scattering technique, and the formation mechanism was preliminary analyzed. If water hardness was less than or equal to1368mg/L, the formation of micro emulsion would not be affected when MEG’s emulsifier was SAA-56or SAA-6EJ, and the rise of water hardness could make former’s droplet diameter decreased slowly, the latter could form micro emulsion with smaller droplet diameter if water hardness was not greater than684mg/L. Water hardness could promote the formation of micro emulsion if emulsifier was SAA-H6, and droplet diameter decreased rapidly following the rise of water hardness. The effect of tap water on micro emulsion formation was to promote forming a micro emulsion with smaller droplet size, or promote the formation of micro emulsion, or prevent the formation of micro emulsion, when the emulsifier was SAA-6EJ, SAA-H6and SAA-56, respectively. If the water temperature was too high, the micro emulsion formation might be prevented. When MEG’s emulsifier was SAA-H6or SAA-56, the formation of micro emulsion would be prevented if the water temperature was not lower than40℃and50℃, respectively. When the emulsifier of MEG was nonionic mixture surfactants, SAA-6EJ, the carrier’s dissolution process could prevent the formation of micro emulsion if the MEG’s carrier was lactose, mannitol, water soluble starch, benzoate and MgSO4, respectively; but the dissolution process of citric acid could promote the formation of micro emulsion, and it could form a micro-emulsion with more smaller droplet size following the rise of citric acid dosage. When MEG’s emulsifier was a mixture of anionic and nonionic surfactants, like SAA-56and SAA-H6, the dissolution process of lactose, mannitol, water soluble starch and MgSO4would not prevent the formation of micro emulsion, but the dissolution process of benzoate could prevent the micro emulsion formation. The technique, near-infrared multiple light scattering, was introduced to study mechanism of MEG’s emulsion stability. Within70min, the migration velocity of droplet was zero, and D50might unchanged, or increased or decreased following time, and the carrier was the major factor contributing to this change. D50would gradually increase as time goes by if the carrier was carbohydrates. But if the carrier was inorganic salts, D50would gradually decrease as time goes by. Compared with MEG that no contain citric acid, if the initial droplet size increased because citric acid as one of carriers, the rising rate of D50would be increased by citric acid; but if the initial droplet size decreased because citric acid as one of carriers, the change rate of D50, including rising rate and decreasing rate, would be reduced by citric acid. Moreover, the Zeta potential had no obviously affect to the change of D50.The research results show that pesticide TC, including liquid TC and low melting point TC, can be formulated as micro-emlsifiable granule with no organic solvent; and high melting point TC also can be formulated into micro-emulsifiable granule by adding suitable organic solvent. The fact that transparent or translucent emulsion remains steady after5min centrifugation at RCF100g can be regard as a necessity for determining that the emulsion is a microemulsion. In spite of that the stability is not adequate to ensure the emulsion is microemulsion. Standard regression coefficient can be used as a very effective filter of pesticide formulation recipe screen. Ca2+, Mg2+and ions in tap water can affect the interfacial tension before the droplet formation and after interfacial rebalance, and finally make effects on the formation of micro emulsion and droplet size. The chain length difference of alkyl and ethoxy group between different surfactants can cause the different temperature range that MEG’s dilution can form micro emulsion. The endothermic and exothermic processes of carrier’s dissolution can prevent or promote the formation of micro emulsion. The electrostatic repulsion is not emulsion stability mechanism of micro-emulsifiable granule. And the bioactivity of micro-emulsifiable granule will not lower than that of microemulsion. Micro-emulsifiable granule is a high effective and environment friendly pesticide formulation, and good application prospect.