After more than 20 years of research, List AG of Arisdorf, Switzerland, has realized its goal of solving the puzzle of direct evaporation for temperature-sensitive polymers.
List's two-step process has moved from concept to pilot scale and now is being scaled to commercial production for several manufacturers.
Direct evaporation, also known as direct devolatization, was recognized as an energy-efficient alternative to the traditional stripping method, according to List. But the process had a major drawback, since it only worked on polymer solutions that were not temperature sensitive.
List claims it has solved that problem. List engineers have discovered how to maximize the mass-transfer driving force for evaporation. During the first step, about 99 percent of the solvent evaporates under atmospheric pressure, or a slight vacuum, and is condensed and recovered. In the second step, any residual volatile concentrations are reduced to a final specification.
List recently demonstrated the new technology to about 60 invited engineers at a Fraunhofer-Gesellschaft pilot plant in Schkopau, Germany. The pilot plant is a joint project between the Fraunhofer Institute for Applied Polymer Research and Fraunhofer Institute for Mechanics of Materials.
List USA Inc. is based in Charlotte, N.C.
During Antec, engineers from List presented two papers about the company's research into kneader reactors:
* Daniel Witte introduced his paper on “Advanced Process Design in High-Volume Kneader Reactors Using Multiple Feed Ports to Avoid Crust Forming, Foaming and Low-Heat Transfer.”
* Boyd Safrit gave a paper on “Kneader Technology for the Direct Devolatization of Temperature-Sensitive Elastomers.”
List also had a booth at the Plastics Encounter show.