Patent ID: 7582724
Filing Date: 2009-09-01
Classification: C08F

Abstract:
1. In a process for the preparation of copolymers containing vinyl acetate, ethylene, and optionally ethylenically unsaturated monomers other than vinyl acetate and ethylene in a polymerization reaction by aqueous, free radical polymerization at a pressure of from 5 to 100 bar absolute by the emulsion or suspension polymerization method, the improvement comprising reducing the pressure after the end of the polymerization to a pressure of from 0.1 to 5 bar absolute and recovering unconverted monomers by multistage fractional low-temperature condensation from a residual gas contained in the reactor, wherein water vapor is condensed from the residual gas in a first condensation stage at a temperature of from 1 to 5° C., vinyl acetate is condensed from gas leaving the first condensation stage at a temperature of from −90 to −60° C. in a second condensation stage, and ethylene is condensed from gas leaving the second condensation stage at a temperature of from −140 to −100° C. in a third condensation stage.