THE INFLUNCE OF TEMPERATURE MODE ON KINETICS OF SODIUM METHACRYLATE AND METHACRYLIC ACID AMIDE COPOLYMERIZATION

Abstract

Experimental studies of sodium methacrylate and methacrylamide copolymerization in aqueous solutions with a total monomer content of 34-50% were accomplished. Potassium persulfate was used as the initiator. Three variants of the process operation conditions were investigated: isothermal, quasi-isothermal and adiabatic. The effect of temperature, initial concentration of monomers and initiator on the rate of copolymerization, the extent of monomers conversion, the duration of the process, the reaction mass viscosity were studied under isothermal conditions. The copolymerization takes place at a constant rate at all temperatures in the range of 55-80°C until conversion is less than 70%. This behavior is typical for the polymerization system with initial total concentration of monomers of about 4.4 mol·L-1 and above. It is found that the reaction rate is directly proportional to the initial concentration of the reaction system. Increasing temperature reduces the viscosity of a 1% aqueous solution of the product, thus reducing the average molecular weight of the copolymer. By means of studying the copolymerization under adiabatic conditions the dependences of the monomers conversion degree, the viscosity of a 1% aqueous solution of the product and the reaction mass temperature upon copolymerization time were obtained. In the adiabatic mode the monomers conversion is less than 70%, the viscosity of a 1% solution of the reaction mass is approximately 13·10-6 m2/s, and the temperature rises to ~ 120°C. The product is a polymer gel, water-swellable and soluble in an aqueous alkaline medium. The quasi-isothermal mode of copolymerization with the same duration allows obtaining the degree of conversion of about 94% and a viscosity of the reaction mass of about 400·10-6 m2/s. An important advantage of the copolymer obtained in the quasi-isothermal mode as compared to that obtained in the adiabatic conditions is complete water solubility. Based on experimental results, the recommended conditions for the sodium methacrylate and methacrylamide copolymerization are as follows: the monomers concentration in the reaction mass is 5.55-6.75 mol·L-1; initiator concentration is 2·10-3 - 6·10-3 mol·L-1; copolymerization temperature is 55-65°C.