Synthetic Method Of Low Molecular Weight Sodium Polyacrylate

Low molecular weight sodium poly(acrylic) acid (PAANa) is one of the most important water-solubility polyelectrolyte, which has been widely used in many application. As new applications finding in recent years, more and more attention has been paid in science and industry fields. But it need is high cost in prepartion process using the traditional method, so it is significant to study the synthetic method and low cost produce technology for low molecular weight PAANa.The low molecular weight sodium polyacrylate was synthesized in dynamic aqueous solution in this paper. The different parameters of reaction conditions, such as monomer concentration, initiator, chain transfer concentration and polymerization temperature, would effect many properties including the solubility, the viscosity and the molecular weight of polymers obtained. The experiment results showed a series of low molecular weight sodium polyacrylate can be synthesized under the conditions below: monomer concentration 50%, initiator concentration 4% (based on the weight percentage of monomer), chain transfer concentration 200-300% (based on the weight percentage of monomer ), polymerization temperature 80-90℃ and reaction time 6h.A new synthetic method (static method) is presented in this paper. Explosive polymerization can be prevented efficiently by controlling the reaction conditions appropriately by studying the heat relaxing property, and a series of narrow distribution of molecular weight, high monomer conversion, low molecular weight water-soluble sodium polyacrylate were synthesized. The produce cost lower than that synthesized with dynamic method obviously. It was shown in the experimental result that low molecular weight of sodium polyacrylate was synthesized under the best reaction condition: monomer concentration30%, initiator concentration 4% (based on the weight percentage of monomer), chain transfer concentration 4% (based on the weight percentage of monomer), polymerization temperature 60℃ and reaction time 3h.In the comparison of the dynamic method with the static method, this new synthtic method has some advantages: shorter reaction time, simple operation, fewer amount of molecular weight regulator , lower energy loss and cost.The rheological property and chelate ability to Ca2+ of the polymerization product were also studied in this paper. It was found that the viscosity was sharply affected by temperature and shearing time. The solution has the characteristic of rheological property and shearing-thin fluid. The low molecular weight PAANa synthesized by the static method owns excellent chelate ability to Ca2+, the biggest chelate ability is 479mgCaCC>3/g. It fit for the properity enquires to sodium polyacrylate in many fields.