Preparation of acrylic/acrylate copolymeric surfactants by emulsion polymerization used in pesticide oil-in-water emulsions

摘要

In this work, acrylic/acrylate copolymeric surfactants, which can be used in the preparation of pesticide oil-in-water emulsions (EW), were synthesized by emulsion polymerization, using potassium persulfate (K_2S _2O_8) as an initiator, dodecyl mercaptan (DDM) as a chain transfer agent at the temperature range of 82-85°C. When the weight ratio of monomers was m(butyl acrylate): m(methyl methacrylate): m(acrylic acid) = 4: 4: 1.6 and the dosage of DDM was 2% (percentage of monomer mass), the prepared acrylic/acrylate copolymeric surfactants had a number-average molecular weight of 2.5 × 10~4 and exhibited good stability for pesticide EW. The carboxylic group distribution studies show that only the surface carboxylic groups make dispersed pesticide oil droplets more stable. The acrylic/acrylate copolymeric surfactants prepared by shot-monomer had the most surface carboxylic group distribution (46.6%). To obtain greater surface carboxylic group distribution, maleic anhydride (MA) was used to modify the polymer system. Adding 2% MA (percentage of monomer mass) to the polymerization system, the surface carboxylic groups were increased 12% over unmodified acrylic/acrylate copolymeric surfactants. Compared with traditional pesticide EW, the avermectin EW prepared with acrylic/acrylate polymeric surfactant had much better stability. Meanwhile, its pesticide effect was similar to that of a control (1.8% abamectin emulsifiable solution).