Preparation And Characterization Of The Metolachlor Melamine Formaldehyde Microcapsule Suspension Formulation

Pesticide capsule suspensions(CS) is a new water-based sustained release dosage forms, the active ingredient encapsulated in the polymerization of monomers, microcapsule wall material formed by crosslinking. CS is to achieve the development of pesticide pesticide injury is minimized, maximized efficacy and environmental-friendly environment of the object. Currently, melamine- formaldehyde resin as wall material with low cost and superior in-situ polymerization researchers much attention, but due to various indicators is difficult to artificially control, so melamine- formaldehyde resin preparation(MF) microcapsules the study is of great significance.In this paper, with metolachlor as a core material to prepare metolachlor capsule suspensions melamine formaldehyde resin as wall material.This article was prepared by in situ polymerization of microencapsulated suspension, the capsule core is metolachlor, wall melamine- formaldehyde resin. Mainly on the type and amount of different types of emulsifiers, the mass ratio of core to wall, a shear rate of emulsification, acidification stage acidic catalyst type, the dropping velocity and the final pH, curing temperature curing stage trial conditions, mixing speed, curing time Preparation experimenting(1) by an average particle diameter of the microcapsules and encapsulation efficiency study found that non-ionic surfactant Tween80 can achieve better emulsifying effect. When Tween80 amount of 5%, the average particle diameter of the microcapsules is about 6.3μm, encapsulation efficiency of more than 80%, the morphology of microcapsules prepared neat, smooth, good dispersion.(2) the core and bladder wall mass ratio of the thickness of the microcapsules, and the release rate of encapsulated microcapsule suspension performance and the like influence. When the core wall ratio of 1∶1.75 when the capsule suspension to achieve a higher encapsulation efficiency.(3) and then by a laser particle size analyzer capsule suspension microcapsule particle size measurement. Microcapsule size and distribution is mainly affected by the combined effects of shear rate and emulsified viscosity when the shear rate increases to a certain extent, the trend to further reduce the average particle diameter of the microcapsules becoming weaker. When emulsification shear rate in 19000 r / min particle size is moderate, good particle size distribution. Also can be used to adjust the viscosity of the method to further reduce the particle size of the microcapsules.(4) in the acidification stage acidic catalyst, acidic catalyst and dropping the end of reaction pH can effectively control the speed of melamine resins and polycondensation reaction degree. Through the structure and size of the microcapsule wall inspection results, when using a 5% citric acid as the acidic catalyst in the acidification stage, about 60 min the pH of the reaction system was adjusted to the end, microcapsules regular shape, high mechanical strength, adhesion phenomenon does not occur.(5) the process conditions that affect the curing stage metolachlor capsule suspensions encapsulation rate, particle size and morphology of the important parameters. Found experimentally that increasing the stirring speed as the cure, the average particle diameter becomes smaller microcapsule, and the appearance becomes good, uniform particle size distribution of the stirring rate at 600 r/min, microcapsules regular morphology; as the curing temperature increased encapsulation efficiency was positively correlated and their strength tends to be moderate, when the temperature is higher than 60 ℃ entrapment rate began to decline. Therefore, it recommended to choose the curing stage at a curing temperature of 60 ℃ to 600 r/min stirring speed curing 90 min to produce a good performance of metolachlor microcapsule suspension.