Study On Synthesis Of Urethane Reactive Emulsifier And Its Application In Emulsion Polymerization Of Acrylates

Our aim is developing a novel urethane reactive emulsifier (RE) with good properties in this paper.Urethane reactive emulsifier (RE) was synthesized by using maleic anhydride (MA), diethyleneglycol (DEG), toluene 2,4-di-iso-cyanate (TDI), 2-hydrozyedthyl methacrylate (2-HEMA) and anhydrous sodium sulfite as starting materials, and then esterification, prepolymerization and sulfonation. The synthetic conditions and active composition of urethane reactive emulsifier (RE) were explored. The experimental results are as follows: The optimum reaction conditions for esterification are that molar ratio of MA to DEG is 1.03 : 1.00, reaction temperature is within a range of 70 1 C, and reaction time is 6-7 hours; The best sulfonating conditions mainly include that a 10-15% Na2SO3 water solution of which the molar numbers are 1.03 times as much as those of MA, is added to the sulfonating system, reaction temperature is 60 C, and reaction time is 5 hours; its active composition is 32.9% by weight. The critical micelle concentration (CMC) of RE was determined by using conductance and surface tension measurment. At the same time emulsifying power was examined by using different monomers. It was found that the critical micelle concentration of the product is 3.15+10-2mol/L, and RE has excellent emulsifying power.RE contains not only the reactive vinyl bond, but also groups of sulfurous having the role of emulsifier. In order to eliminate the negative influence of conventional emulsifier on properties of emulsion, urethane reactive emulsifier synthesized above was applied to emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA). The morphology of the latex particles, water resistance, adhesion capacity, adhesion strength of the copolymers, and emulsion stability were investigated. Compared with the conventionalemulsion polymerization system in the presence of sodium dodecyl benzene sulfonate (SDBS), the latices prepared by emulsifier-free emulsion polymerization have much more narrow distribution of latex particle sizes (0.2um in diameter), better resistance to electrolytes, pH, freeze-thaw, and better mechanical stability. Not only the tensile strength of the copolymers prepared by this method is obviously increased, but also the water resistance and adhesion capacity are significantly enhanced. On the other hand, the TG results indicate the copolymer has lower thermal stability than conventional copolymer.