Synthesis Of Low-molecular Weight Polyacrylate Sodium

Low-molecular-weight sodium polyacrylate(PAAS) which is a water-Solublepolyelectrolyte is widely used in many industries. The Sodium polyacrylate withmolecular weight between2000and3000has a good scale inhibiting effect,commonly used as inhibitors and corrosion inhibitor in the treatment process forindustrial water recycling. With the current sodium polyacrylate growing demand, it isof great significance to study the synthetic method of sodium polyacrylate and itsperformance．The low molecular weight sodium polyacrylate was synthesized by singleperoxide initiation system, and using iso-propyl alcohol as chain transfer agent. Theinfluences of factors，such as the type and amount of chain transfer agent, theconcentrations of monomer，initiator and chain transfer agent，the temperature andtime of polymerization，on the molecular weight of polymer were discussed. Theresults showed that low molecular weight of sodium polyacrylate（about2000-3000）can be polymerized at70℃for3.0h，with the monomer concentration of40%, theinitiator concentration of3.0%, the chain transfer agent concentration of200%. Underabove conditions, the molecular weight of product was about2700and the monomerconversion rate was aboue97.2%.The low molecular weight sodium polyacrylate was synthesized by(NH4)2S2O8-NaHSO3initiation system, and using NaHSO3also as chain transfer agent.The influences of factors，such as the concentrations of monomer，initiator and chaintransfer agent，the temperature and time of polymerization，on the molecular weight ofpolymer were discussed. The results showed that low molecular weight of sodiumpolyacrylate（about2000-3000）can be polymerized at60℃for2.0h，with themonomer concentration of25%, the initiator concentration of0.6%, the chain transferagent concentration of2.0%. Under above conditions, the molecular weight ofproduct was about2400and the monomer conversion rate was aboue98.5%. The low molecular weight sodium polyacrylate was synthesized by assistance ofphoto-initiation. The influences of factors，such as the concentrations of monomer，initiator and chain transfer agent，the temperature and time of polymerization，on themolecular weight of polymer were discussed. The results showed that low molecularweight of sodium polyacrylate（about2000-3000）can be polymerized at30℃，withthe monomer concentration of20%, the initiator concentration of0.05%, the chaintransfer agent concentration of2.0%, the distance of15cm. Under above conditions,the molecular weight of product was about2400and the monomer conversion ratewas aboue99.4%.The scale inhibiting effect to calcium carbonate scale and the influence ofvarious factors was studied. The results show that sodium polyacrylate has a goodscale inhibiting effect when the molecular weight is between2400and2800.Increasing the amount of sodium polyacrylate solution can effectively increase thescale rate; increasing pH value which is conducive to product the calcium carbonatescale, the scale rate decline; the influence of temperature on the scale rate issignificant. When the temperature is low, the scale rate is better. When thetemperature to raise, the scale rate decline rapidly. With the increase of theconcentration of bicarbonate ions, the scale rate decreased gradually, because it isconducive to the formation of calcium carbonate.