Dryerless PET extrusion with viscosity control

Constant Viscosity – Optimum End Product Quality

On a MRS extrusion line, the melt viscosity can be measured in real time with the Online Viscometer, VIS. Using a precision spinning pump, a small polymer flow is pumped in bypass through a precision capillary. Both the melt temperature and the melt pressure are measured (at two points) and using internal calculation software, the system works out the representative shear rate and viscosity.

When processing recycled PET with a varying residual moisture level and input quality, based on this melt viscosity measurement, it is possible to maintain the melt viscosity within a narrow tolerance band by changing the vacuum at the devolatilising section of the MRS extruder. With a control loop from the online viscometer VIS to the vacuum pump(s), the melt viscosity and therefore the IV of the end product can be maintained at the required level. While other manufacturers also offer online viscosity measurements Gneuss' MRS extrusion technology is the only technology to measure and actively control the end product IV.

MRS – the dryerless alternative

Thanks to the features described above, the MRS Extrusion Technology is particularly suited to the manufacture of thermoforming sheet, strapping, nonwovens and other fibers. With its extremely efficient devolatilisation performance thanks to the huge surface area renewal rate in the multi rotation section, it is possible to process recycled material to a final product without compromising quality. In combination with the Online Viscometer VIS, the Gneuss MRS offers the unique feature to not only monitor, but also control the IV of the manufactured end products. This technology has successfully been in operation for several years now, with several dozen lines running worldwide in sheet, strapping and fiber applications.