The MRS extruder processes undried PET bottle flake without any pre-treatment directly into pellets. The polymer melt is intensively and rapidly exchanged in the multiple screw section of the extruder. The huge surface area is exchanged at an unparalleled rate so that even with a moderate vacuum level of 25 to 40 mbar in the degassing section, contaminants are efficiently evaporated out of the melt. A letter of Non Objection (LNO) from the FDA underlines the decontamination efficiency. If, in order to boost the intrinsic viscosity (IV) a JUMP reactor or a downstream solid state polymerisation system (SSP) is used, this can be specified far shorter than otherwise necessary as the extruder has already carried out the decontamination of the bottle flakes. The end product is of especially high quality with regard to transparency and yellowness.