Synthesis Of Polyacrylamide In Unsteady System

Since the 20th century,polyacrylamide was used as an industrial product in wide range of industrial applications.At present,the main countries,which had this product,were China,America,Europe and Japan.In these countries,polyacrylamide was widely used in water treatment and paper-making industry.But in China,polyacrylamide was mainly used in mining,oil recovery and paper making.The main methods of polyacrylamide production are aqueous solution polymerization,suspension polymerization,inverse suspension polymerization.There are many shortcomings.For example,water solution polymerization was difficult in heat dissipation.Besides,the ployacrylamide is easily cross-linked.Furthermore,suspension polymerization and inverse suspension polymerization were difficult to operate and the solids content were lower.Therefore,this paper has studied a new polymerization method of water-in-oil system which was called unsteady-state system polymerization method.The unsteady system relied on the mechanical stirring to achieve the water-in-oil environment which allowed the monomer aqueous solution to form a uniform droplet in the polydimethylsiloxane.Then,the monomer solution formed the droplet as the polymerization unit.The radical polymerization reaction took place and produced granular polyacrylamide.There was not any surfactant or emulsifiers in this system.For this reason,the water-in-oil system was unsteady,and the polymer particles could precipitate to the bottom of flask when stopping the stirring.In this way,the separation operation was simplified.Besides,the heat dissipation problem was resolved.It could also greatly increase the solids content of the polymer.In this paper,the effects of different oil phases,mixing speeds,and oil-water volume ratios were explored firstly.Through the study of synthetic polymers,it was finally concluded that polydimethylsiloxane was chosen as the oil phase in the unsteady system.The best volume ratio of oil/water is at least 2:1,and the stirring speed is faster than 300r/min.Only in this way,can the system achieved the excellent effect.In unsteady system,the acrylamide monomers were homopolymerized by using redox and azo initiators respectively.Many polymer conditions were studied such as polymerization temperature,initiator dosage,mass concentration of monomer solution and pH value of system.The best condition was determined:for the redox initiator,the optimum polymerization temperature was 50℃,and the initiator amount was 0.05%.The conversion rate could reach 94%and the molecular weight exceeded 3 million.But the optimum temperature with the azo initiator was 60℃while the dosage is 0.02%.In this condition,the conversion rate of arylamide was up to 99%and the molecular weight was close to 6 million.By the way,the great monomer mass concentration is 40%and the alkaline environment was beneficial to radical polymerization.Besides,the solubility of polyacrylamide was great than other emthods.The results of FT-IR and ~1H-NMR showed that the acrylamide double carbon bond was broken,and the free radical polymerization proceeded smoothly in the unsteady-state system.The copolymerization reaction was studied in unsteady system.The DMC was used as the cationic monomer,copolymerized with acrylamide by the azo initiator of V-50.The effects of any conditions,such as the copolymerization temperature and the monomer ratio,were studied on the molecular weight,the conversion,the cationicity,and the charge density of the product.Then,it was compared with with the polyacrylamide of aqueous solution polymerization.It was shown that the excellent quality retio of DMC/AM is 9:21 in unsteady system,and the conversion rate was about 98%,the molecular weight was 7.8 million.The chargeability was measured in this condition.The cationic degree of CPAM was 19.21%and the charge density was 51×10~5μeq.It was shown in pH experiments that the copolymerization reaction was the same as the homopolymerization reaction,and the alkaline environment was beneficial to free radical polymerization.At the same time,it was found that polymer particles which synthesized in unsteady system had high solid content and high conversion,but slightly lower cationicity than aqueous solution polymerization.characterizationIt were showed in FT-IR and ~1H-NMR that the copolymerization of the two monomers occurred in unsteady system,and the cationic group was attached to the long chain of the molecule.The drying efficiency,dissolution rate and particle size of the polyacrylamide particles prepared in the unsteady system were studied.It was compared with other synthetic methods of water-in-oil systems.Then,the polymer was tested for flocculation.It was showed that the average particle size of polyacrylamide which synthesized in this system was about 3 mm;while the average particle size of the cationic polyacrylamide particles was about 1.9 mm.Compared with other method,the polyacrylamide had a slightly larger particle size,but the solid content of the product was greatly increased.The polyacrylamide particles had a faster drying effectiveness.The polyacrylamide which synthesized in unsteady system had excellent water solubility,especially cationic polyacrylamide.CPAM was quickly swelled in water and dissolved within 2 hours.Finally,through the flocculation test of polyacrylamide,the results showed the particles could be adsorbed in the kaolin suspended particles.So,it could be proved that the polyacrylamide synthesized in unsteady system was so excellent that could be used for flocculation work.