Verfahren zur Aufbereitung von Altkunststoffen oder Altkunststoffgemischen für das rohstoffliche Recycling

摘要

Previous processes for reprocessing produce plastics waste products which, owing to their extremely varied molecular weight distribution, can be separated and mixed only inadequately during admixing with petroleum intermediates and cause disturbances and irregularities in further processing. The object was therefore to develop a process for reducing the molecular weight of plastics waste or plastics waste mixtures in which products are produced which result in stable mixtures during admixing with petroleum intermediates. According to the invention, the reprocessing of the plastics waste or plastics waste mixtures is performed by means of extruders having a progressive temperature profile over 2/3 and a degressive temperature profile over 1/3 of the effective screw length of the extruder. The melt itself and the molecular weight are made more uniform by means of downstream static mixers having a graduated temperature profile. The process unit for reprocessing may be integrated in the refinery units (cracking, hydrogenation, gassification, visbreaking), or be installed externally, the plastics waste to be treated then being incorporated in the refinery flow by means of a bypass device.