Monsanto Company

Gerd R Baur

Donald Joseph Stookey

Edwin W Folk

Charles Nelson Carpenter

Arthur A Armstrong

Robert L Voges

The method of recovering unreacted mono-olefinic monomers from an acrylonitrile polymerization slurry containing 30 to 50 weight percent of polymer solids and 70 to 50 weight percent of unreacted monomers wherein the slurry is first diluted with a solvent for the polymer and then fed in series through first and second treatment zones, with each of the treatment zones having a first stage for mixing the slurry with a solvent in vapor form to vaporize some of the unreacted monomers from the slurry and form a polymer solution and a second stage for separating monomer vapors from the liquid polymer solution. Fresh solvent, in vapor form and at an elevated temperature is supplied to the mixing stage of the second treatment zone and the vaporized solvent and unreacted monomers from the separation stage of the second treatment zone are fed to the mixing stage of the first treatment zone. The preferred ratio of solvent to slurry being fed to the mixing stages is 0.8 to 1.2. The polymer solution leaving the separation stage of the second treatment zone has a very low content of unreacted monomers.

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Decatur, AL, United States of America

Gerd R Baur