Preparation And Characterization Of Melamine Formaldehyde Resin 2,4-D Isooctyl Ester Capsule Suspension

The safety of pesticides has been put forward higher requirements,with the improvement of awareness on food safety and the environmental protection.Water-based environment-friendly pesticide formulations have become the trend of pesticide formulations on nowadays.Pesticide microencapsulation technology is an important application technology with high technical requirements in pesticide formulations processing.Due to the comparison of other pesticide formulations,microencapsulated pesticide formulations have the advantages of environment-friendly,long sustainable release time,high effective and low toxicity.In recent years,the pesticide formulations are being paid more and more attention by researchers and enterprises of pesticide formulations.2,4-D isooctyl ester is a Phenoxy carboxylic acid compounds.It is an improved type of 2,4-D butyl ester for the selective herbicide used in the control of broadleaf weeds.With the use of 2,4-D butyl ester has been forbidden by the Ministry of Agriculture of the People's Republic of China in 2016 because of its drift risk and serious injury.2,4-D isooctyl ester is likely to become an alternative to 2,4-D butyl ester.However,2,4-D isooctyl ester meet some problems such as single formulations,short pesticides lasting validity period and high drift risk in the real applications.The microencapsulation of the 2,4-D isooctyl ester can overcome these problems at a large extent,allowing it to escape from the fate of the 2,4-D butyl ester being disabled.In this study,melamine-formaldehyde resin with excellent properties is used as microcapsule shell and 2,4-D isooctyl ester microcapsules are prepared by in-situ polymerization.The factors effected by different kinds of emulsifier and the dosage,emulsifying shear rate,curing reaction time,the ratio of wall material to core material on the preparation of 2,4-D isooctyl ester microcapsules are discussed.The 2,4-D isooctyl ester melamine resin microcapsules were characterized by Fourier transform infrared spectroscopy,laser particle size analyzer,ultraviolet spectrophotometer and electron scanning microscope.Finally,the capsule suspension was prepared by adding the corresponding additives in the microcapsule slurry prepared under the optimum process conditions.The results showed that the emulsifier had the best effect on the emulsification of 2,4-D isooctyl ester with Tween80 dosage of 4% and the oil-in-water emulsion had the best stability.The shear emulsification rate was 22000 rpm and the molar ratio of melamine to formaldehyde was 1: 3,the mass ratio of wall material to core material is 1: 2,the reaction temperature is 60 ?,the pH is slowly adjusted to 5 in 30 min,and the reaction time is 2h.Under this condition,the microcapsules were not adhered,the surface was smooth,the size of the particles was uniform and the average particle size was 3.5?m.The average encapsulation efficiency was 91.24%.Through the laboratory simulation release experiment,the release time can last 30 days.The cumulative release curve in line with Peppas mathematical model,the release mechanism for the diffusion-erosion release mechanism.Microcapsules are prepared by adding a certain percentage of adjuvant and thickener.The main performance indexes such as heat storage and cold storage are tested,which have good physical and chemical stability.The 2,4-D isooctyl ester encapsulated by melamine formaldehyde resin has the sustained-release properties.