Post-extrusion operation of polymerization reaction is another important application area for twin screw extruder, whose advantages are obvious.
According to different techniques, we usually need to separate, remove and recycle the water, solvent, monomer, oligomer, by-product residue and unstable end group from undried powder, colloid solution and other solutions, and melt material after the reaction. Sometimes, we need to add various kinds of additive for refining and homogenization. All these steps belong to the post-treatment operation of the polymerization.
Negative factors, including high viscosity, phase transformation and the material sticking to the inner wall, make it unsuitable for traditional and normal equipment to handle polymers. However, the specially designed twin screw extruder is just perfect for this job:
1) devolatilization performance is consistent and great;
2) production process is simplified,
3) cost and energy consumption are lowered;
4) operation environment and product quality are improved,
5) the extrusion and pelletizing processes are mostly completed with no human operations—granules are directly available at the end of the process.
According to the operation that is adopted, post-treatment can be divided into two types, namely solvent evaporation and extrusion dewatering. The former can handle the material systems with water content of as high as 70-80%, while the latter is typically used for materials with water content of 30-60%. When using the extrusion dewatering method, power consumption could be lowered remarkably because the dewatering process is performed at liquid phase.
Applications: 70% carbon tetrachloride removal from chlorinated polypropylene; removal of the monomer in PMMA; 50% removal of cyclohexane ink resin; epoxy propane removal in CO2 based copolymers; PC copolymer devolatilization, PS copolymer devolatilization; dewatering of undried ABS powder; dewatering of chlorosulfonated polyethylene; crushing dewatering of various kinds of resin; stabilization of the fluoroplastics and POM with removed end groups.
1.reactor 2.metering pump 3.condensator 4.twin screw extruder with multi-stage degassing 5.twin-screw extruder 6.carrier feeder 7.water trougn 8.air-knife 9.pelletizer 10.product container 11.weighing and bagging
swelling, desolution, devolatilization, deforming spinning line