ETHYLENE-VINYL ACETATE SEMIBATCH EMULSION COPOLYMERIZATION - USE OF FACTORIAL-EXPERIMENTS FOR PROCESS OPTIMIZATION

The application of factorial experiments to optimize the ethylene-viny l acetate emulsion polymerization process is described herein. A prior extensive experimental phase identified those variables that are most important for ethylene-vinyl acetate emulsion copolymer production. T he effects of temperature, pressure, added co-solvent, vinyl acetate f eed rate and emulsifier type, and concentration on the rate of polymer ization, cumulative copolymer composition, molecular weight averages, and particle size and number are described in this article. The primar y objectives of this research were to increase the amount of ethylene that could be incorporated into the copolymer at reduced temperatures and pressures (our target was a copolymer with an ethylene content of 30% by weight at 500 psig and 20-degrees-C versus the commonly employe d industrial conditions in excess of 1000 psig), to achieve an improve d process understanding, and to accumulate reliable data for modelling purposes. A copolymer containing 34% by weight of ethylene has been a chieved at a pressure of 500 psig and a temperature of 20-degrees-C. T he confusion present in the literature surrounding emulsifier effects has also been clarified. A discussion of hydrolysis, experimental repr oducibility, and glass transition temperatures is also included. The s equential nature of the experimental process is illustrated throughout these optimizing experiments. (C) 1994 John Wiley & Sons, Inc.