Optimization of synthetic conditions of styrene acrylic emulsion

Styrene acrylic emulsion used in water-borne paints was prepared by emulsion polymerization with styrene,acrylics acid,butyl acrylate and methyl methacrylate as the monomers.The reaction conditions such as reaction temperature,initiator dosage,emulsifier dosage,and functional monomer acrylic acid dosage on the performance of as-synthesized styrene acrylic emulsion were systematically studied.Moreover,the effect of acrylic acid monomer on the ability of as-synthesized styrene acrylic emulsion to resist acid attack and alkaline attack was explored,and the optimized reaction condition was established.Results indicate that with the increase of reaction temperature,the conversion rate of the mixed monomers increases rapidly and reaches the maximum of 97.1% at 78 ℃,then it remains nearly unchanged with further increase of reaction temperature.In the meantime,the conversion rate of the mixed monomers tends to rise initially but decline later with increasing dosage of potassium persulfate initiator.Particularly,the conversion rate reaches the maximum when the amount of potassium persulfate is 0.010of the total mass of the mixed monomers,and in this case the mixed monomers are completely converted.Besides,with the increase of emulsifier dosage(mass ratio of emulsifier to monomer),the appearance,stability against Ca2+,and gel performance of as-synthesized styrene acrylic emulsion tend to be improved to some extents,but its water absorptionincreases therewith.In terms of the optimized reaction condition,the reaction temperature is suggested as 78℃,the composition of the mixed monomers is suggested as 15g styrene,2g acrylic acid,18g butyl acrylate,and 8g methyl methacrylate,and the percentages of the initiator and emulsifier in relation to the mixed monomers are suggested as 0.010and 0.035.Target styrene acrylic emulsion obtained under the optimized reaction condition exhibits good stability in acidic mediums.