A new compounding process polymerizes liquid monomer without solvent in a single-shaft, plug-flow “Kneader Reactor,” then transfers the viscous polymer to a twin-shaft “Kneader Finisher,” where secondary polymers, additives, and fillers may be added before the compound is pelletized. The process was developed over four years (U.S. Pat. Applic. 20060155087) by List AG in Switzerland, whose U.S. office is in Charlotte, N.C. List has built two pre-commercial units. One potential application polymerizes methyl methacrylate monomer into PMMA with 97% efficiency in the first stage. This polymer is transferred by screw directly into the twin-shaft “finishing” vessel, where residual monomer is removed and fillers and additives may be added. This solvent-free process replaces conventional polymerization using solvent diluent to control reaction temperature. List’s high-torque reaction vessel controls reaction temperature by evaporative cooling of unreacted monomer from the large exposed surface area as polymer is turned between the rotating single shaft and “passive hooks” or stators on the vessel walls. Final compounding in the twin-shaft vessel does not add shear energy. The first full-scale commercial system is being built to produce 11 million lb/yr of an undisclosed compound. List expects production cost will be only half that of a standard solvent-based reaction followed by twin-screw compounding. The process won an SPE environmental award and will be presented at NPE 2009 in Chicago and the accompanying SPE ANTEC conference in June. (704) 423-5478 • www.list.us
LIST USA Inc
1629 Cross Beam Dr Charlotte, NC 28217
Phone (704) 423-5478 Fax (704) 423-0210
Editor PickOptimize Feeding to Make More Money in Twin-Screw Compounding
Follow these practical examples to improve the feeding efficiency and productivity of your process.