Coperion_hero_devolatilization

Integrated devolatilization solutions

Devolatilization is a common process task in many polymer producing and compounding operations.

Efficient devolatilization of polymers

Depending on the process small (< 0.2 %) to large amounts (ca. 50 %) of volatiles have to be removed from the polymer melt rsp. solution or the solid polymer pellet. Required residual volatile levels depend on type and application of polymer. Volatiles could be monomers, moisture, gases e.g. air or solvents. The type of volatile depends on polymer and way of polimerization.

As a technology leader for processing tasks, Coperion offers comprehensive, tailor-made devolatilization solutions for compounding and extrusion processes. These range from the devolatilization of plastic melts and rubber devolatilization to the production of practically odorless plastics for packing materials or auto interiors. Regardless of whether volatile components are available in small or large batch sizes, with a high or low boiling point – with their years of experience from numerous projects, tests, simulations and scale-ups, our specialists adapt every twin screw extruder optimally to your devolatilization application, from the lab scale extruder to the high-performance compounding plant.

For the processing of low-viscous, thin-bodied melts and for extrusion processes with high gas quantities we integrate our ZS-EG twin screw side degassing into compounding plants. With its large cross section for the devolatilization, it keeps the melt in the process section without product escape even at maximum specific torque of the extruder. Fumes or gases are reliably drawn off through the axially open screw flights. Increases in the throughput rate of up to 30 % with improved product quality are possible.

Coperion Degassing Unit

Extruder devolatilization

ZSK twin screw compounders form an excellent concept for devolatilization whether low or high amounts of volatiles, volatiles with low or high boiling point, have to be removed. This results from more than 50 years of experience on small and large ZSK extruders, low and high output rates. Calculations and trials form the basis for the transfer/scale-up to commercial operations and are backbone of the wealth of practical experience.

Devolatilization of volatile ingredients from polymer melts

Polymer Type Parts before devolatilization Final content; extruder devolatilization
LDPE Ethylene < 3,000 ppm < 1,000 ppm
LLDPE Hexane, Cyclohexane 10-15% < 500 ppm
    3% < 250 ppm
EPDM Hexane, Cyclohexane 10-15% < 1,000 ppm
POE, PP Hexane, Cyclohexane 5-15% < 1,000 ppm
EVA Vinylacetate 5,000 ppm < 50 ppm
PS Styrene 3,000-5,000 ppm < 300 ppm
ABS Acrylonitrile (AN) 20 ppm < 4 ppm
PC Methylenchloride 20% < 50 ppm
PA 6 Caprolactame < 8% < 0.8%
SBR, SBS Hexane, Cyclohexane 15-70% < 1,000 ppm
Acrylic adhesive Acetone 50% < 1,000 ppm
Polyimid Chlorobenzene 70% < 500 ppm
PP various approx. 1,000 ppm < 50 ppm
PMMA MMA 10-40 % < 0.3%
POM H2O 5% < 100 ppm

 

Key benefits of the ZSK extruder in devolatilization processes

  • Several parallel and continuous screw channels inside the process section
  • The proper design of screw pitch and selection of operating conditions allow for partial filling of the screw channels
  • Staged vacuum along the process section ensures balance between volatile amount and gas velocity thus providing safety of venting operation
  • Possibility for adding stripping agents: Using stripping agents such as water, N2 or CO2 further enhances the devolatilization process. Such stripping agents will reduce the partial pressure of the volatile or they will, together with the solvent or monomer form an azeotrope. Typically up to 1 % of such stripping agent is introduced into the closed, pressurized portion of the barrel section. It has to be incorporated under pressure still as a liquid. It will later on turn into steam and create bubbles inside the melt pool to further increase the surface devolatilization.

Typical set-up for devolatilization of SBR or LLDPE

Multiple processing tasks

  • Devolatilization of SBR or LLDPE
  • Devolatilization of polycarbonate
  • Devolatilization of LDPE
  • Stabilizing and devolatilization of polyoxymethylen
    Alloying and blending in one step

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