Phase Behavior Of Ammonium Sulfate-Cationic Polyacrylamide-Water And Its Application In Aqueous Two-phase Polymerization Stability

Polyacrylamide (PAM) is the general designation of homopolymer and copolymer of acrylamide and its derivant. PAM is a linear water soluble polymer, which is widely used in water treatment, paper making, petroleum and other industry. Aqueous two-phase polymerization is a new mode of polymerization, in which the water-soluble monomers and another water-soluble compound are dissolved to form a homogeneous aqueous solution, then polymerize to form a heterogeneous polymer dispersion aqueous solution. The system has a relatively low viscosity and it does not have the pollution of organic solvent. In a word, it has a broad application. In essence, the purpose of aqueous two-phase polymerization of PAM is to solve the problems encountered in solution polymerization of PAM, including high viscosity, poor heat dissipation ability, product with bad soluble property.In aqueous two-phase polymerization of acrylamide, if the monomer amount was raised to high, the process viscosity would increase to high level. In situation not that bad caking will be found in products and in more serious situation the system will solidify in whole. To conquer this problem, phase separation experiments were carried out. The quantity of ammonium sulphate(AS) for phase separation was used as standard to evaluate the effects of different factors on phase separation and the purpose was to find effective methods to improve phase separation situation in polymerization process. The effects of additives, monomer, temperature, mixing, stabilizer, PAM concentration were studied. The existence of abundance monomer is the most important factor on phase separation.By measuring AS amount for phase separation, only the critical condition of phase separation can be found. If the change of polymer in continuous phase around phase separation is the target, the measuring of viscosity is necessary. Experiment results show that viscosity change from one phase to two phases or reverse is a step. System viscosity after phase separation was always low, wouldn't exceed 5mPa·s. The raising of system viscosity after phase separation in polymerization is not out of the change of distribution of CAPM between the two phases with conversion, but out of phase separation dynamics limitation and formation of cross-linked polymer which can't be salted out.Phase separation dynamics of AS-CPAM-H₂O and PEG-CPAM-H₂O system were also studied. Phase separation dynamics of AS-CPAM-H₂O is mainly controlled by polarity difference between polymer solution and salt solution. The effect of polarity on phase separation thermodynamics and dynamics are similar. When salt concentration is low or some matter unfavorable of phase separation exists, acrylamide for example, phase separation needs several hundred seconds.Considering the importance of monomer concentration on phase separation and phase separation speed, monomer adding mode in polymerization process was changed to ameliorate polymerization process. Adding monomer in batches or drop by drop would improve polymerization process stability obviously. Besides, reducing initiator amount, prolonging polymerization time, adding of some effective additives and reducing temperature were also used to ameliorate polymerization process stability.