Increasing PVAc emulsion polymerization productivity-an industrial application

Abstract

A major objective in the operation of emulsion polymerization processes is that of faster and safer operation with consistent polymer product quality. The reaction is very fast and highly exothermic. This puts a constraint on the speed of the reaction, due to the limited heat removal capacity of the cooling jacket. The high viscosities of the latexes produced in many industrial processes aggravate the heat-removal problems. A systematic, experimental study in a 50 L pilot reactor is conducted where the monomer feed time is changed from 5.5 h to 2.5 h in various runs. The final samples are characterized for various properties which include appearance of emulsion, %solids, particle size, viscosity, <i>p</i>H, free monomer, film appearance and the application property which in this case is the bending length. The final viscosities are in the range of 300-500 poise. The reactor temperature during these runs could be safely controlled between 76-80°C. With decreasing monomer feed time, the final product shows improved application property and lower viscosity. The samples are withdrawn during the course of polymerization for two runs and analyzed for various properties. These provide fundamental understanding about the polymerization process. In conclusion, 30% reduction in batch time is possible.