METHOD FOR PREPARING OF POLYPROPYLENE PELLETS

摘要

Method for continuously preparing polypropylene pellets having reduced low-molecular weight volatile organic compounds, the method comprising the steps of • a) preheating polypropylene pellets, • b) feeding the preheated polypropylene pellets of step a) to a purge vessel and maintaining the pellets in said purge vessel while directing a flow of at least 10 Nm3 purge gas per hour per m3 of polypropylene pellets (Nm3/ m3 pp.hour) through the pellets, • c) removing polypropylene pellets from said purge vessel, wherein the residence time of polypropylene pellets in said purge vessel is at least 24 hours and the polypropylene pellets are maintained at a temperature Tp of from 100 to 140 °C, wherein in the preheating step a) the pellets are preheated to a temperature in the range of Tp - 20°C and Tp + 10°C; wherein the polypropylene pellets have a temperature < 40°C before the preheating step a)