So far selective extraction of polymers has not been used for recycling because generally the solvents are expensive, toxic and their removal is energy intensive. Research has shown however, that high quality plastics can be recovered from mixed plastic waste by selective extraction, using simple, cheap and nontoxic solvents at moderately elevated pressure and temperature.
The objective of the laboratory research was to determine physicochemical aspects such as yield, purity, selectivity and kinetics. The influence of the following parameters on the process were tested out with models as well as with real scrap: solvent, temperature, retention time, pressure, particle size, solvent/polymer rate, presence of detergents, presence of water. These experiments allowed determination of the critical parameters and optimization of the process for several polymer/solvent systems. The purity of the recovered polymers was shown with differential scanning calorimetry (DSC) and infrared analysis. A good selectivity could be obtained.
The kinetics of the process were studied, especially the kinetics of the recovery of polyolefines.
Although the solvatation process can be simulated on a laboratory scale, a lot of aspects can only be evaluated on a larger (pilot) scale. Only one solvent can be applied at a time. When testing processing routes involving the use of multiple solvents, tests will occur in batches. For this reason, an extractor with a limited volume has been selected. According to expectations, this corresponds with an extraction capacity of about 10 kg/h of polymer. The design of the pilot plant was carried out according to these principles.
Funding SchemeCSC - Cost-sharing contracts
3197 KK Rotterdam / Botlek
20090 Assago Milano
2611 JJ Delft