Devolatilization Extruder Definition

In a twin-screw extruder (TSE), the mixing/blending of polymers/additives and devolatilization are mass-transfer operations dependent upon shear/energy that is being imparted into the materials being processed by rotating screws. Devolatilization (DV) refers to the removal of unreacted monomer, solvent, water, and other undesirable materials from the process melt stream. Many devices perform the devolatilization process, however, the twin screw extruders are the most used machines.

Single-screw or twin screw extruders, or any number of custom twin screw extruder or commercially available stripping devices such as wiped film evaporators, have been used for devolatilization. The choice is largely driven by the nature of the polymer to be stripped, the concentrations of volatiles, and other processing actions required for the product.
 

Chuangbo Devolatilization Extruder

As a technology manufacturer and supplier for processing tasks, Chuangbo 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, 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 extrusion processes with high gas quantities, Chuangbo integrate our Devolatilization Extruder into compounding plants. With its large cross-section for the devolatilization, it keeps the melt in the process section without product escape even at the 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.

Elements of a Devolatilization Zone

Whether in a single-screw or twin screw extruder, a typical devolatilization zone consists of a portion of a screw that is partially filled, isolated between two sections that are filled with melt. The filled regions are generally created by non-pumping elements—either compounders, blisters, or the die or exit of the extruder itself. 

Upstream And Downstream

The rear or upstream seal is created by neutral or reverses compounding elements, a blister, a cylinder, or other restrictive means in the screw(s) such that air cannot pass from the rear of the extruder into the devolatilization (DV) zone. A neutral or reverse element forces the screw to be full at that seal, and for some turns of the screw upstream of that seal, to generate pressure to pump over the seal. This isolates the vacuum of the DV zone from the feed throat or other zones of the extruder.

The downstream or front seal is established similarly, and often in the case of simple twin-screw operations or a single-screw extruder, the discharge of the extruder through a die serves as this seal. The goal again is to prevent the vacuum from pulling through the downstream screw elements and disrupting the performance of the vent. Depending on the type of extruder, its length, and functional zones, the upstream seal may be fed from the melting zone of the extruder or may come from another mixing, blending, or venting operation. The downstream seal may be the die itself or discharge into another venting or additives-incorporation portion of the machine.

Devolatilization Technology

Advantages of Polymer Devolatilization

Polymerization Devolatilization Extruder Application

Rubber Deep Dewatering Application