Inverse Suspension Polymerization Of High Molecular Weight Polyacrylate Sodium

Polyacrylate sodium with high molecular weight is widely used as one kind of important anionic flocculation in industry. For inverse suspension polymerization, water soluble monomer is dispersed in oil continuous phase and initiated in aqueous phase. The difficulties of heat transfer and agitation for high viscosity can be overcome by inverse suspension polymerization. It is the newest method to synthesis high molecular weight polyacrylate in particles or powder.Process stability and nucleation mechanism were investigated in inverse suspension polymerization. The effects of ammonium persulfate / aliphatic amine initiators on the kinetics of polymerization and molecular weight of polymer were studied. Transparent particles, with diameter of 50-200u m and molecular weight of 500* 104, was achieved in pilot-scale chemical reaction.Results showed that it can get a good stability at 80% neutralization degree of acrylic acid, 0.15% Span 60 as dispersant and agitation rate of 250r/min, and the reaction temperature maintains 1h at 40癈, 1h at 50癈 and 30min at 60癈, and then rise to co-boiling temperature. After 70% water of solution was evaporated, the reaction reached the end. Investigation showed that inverse suspension polymerization of acrylate is the same as micro-aqueous polymerization, and its nucleation mechanism is similar to that of normal suspension polymerization.Three initiators, ammonium persulfate / DMA, ammonium persulfate / urea / ammonia liquor, ammonium persulfate / triethanol amine were applied to the polymerization at 50癈, 55 癈 and 60癈, and the influence of ratio oxidant / reductant on reaction rate and molecular weight of polymer were studied. It is found that at APS/DMA=0.8%/0.5% and 60"C, we got the highest molecular weight of polymer, 280* 104. Reaction rate can be changed by salts, which can effect the electrostatic field and ionic strength.Application of cyclic voltammetry to detect the oxidizing potential of aliphatic amine is proposed and it can be used to the presumption of ammonium persulfate / aliphatic amine initiators' activity. Results indicated that the sequence of oxidizing potential is accord with appearance activation energy.There is a conflict when to synthesis high molecular weight polyacrylate sodium, the higher of the molecular weight, the more of the gel concentration. Chain transfer agent can be used to reduce the gel concentration. Polyacrylate with molecular weight 1.417*107 wasit k '? m -I: '"r- ft. ife A illachieved at 0.2% ammonium persulfate and 0.17% sodium chloride.High molecular weight polyacrylate sodium was obtained in 1000L pilot-plant.