METHOD FOR PRODUCING SUPERFICIALLY CRYSTALLINE SPHERICAL GRANULES BY MEANS OF AIR-COOLED HOT DIE FACE PELLETIZING AND APPARATUS FOR CARRYING OUT THE METHOD

摘要

A method and a device for producing superficially crystalline spherical granules by means of air-cooled hot die face pelletizing in a cutting chamber. A crystallizable plastic material can be melted and then extruded through a perforated plate. During the air-cooled hot die face pelletizing, at least one cutting blade can be moved relative to the perforated plate. The perforated plate can be temperature-controlled while maintaining a viscosity of the plastic material within nozzle openings. A superficial cooling to a crystal nucleation temperature of the dry-cut granules is performed by means of a centripetally inflowing process gas. The crystal nucleation temperature is below an optimum crystal growth temperature and above a glass transition temperature. By controlling the quantity of process gas at an adiabatic temperature, an average granule temperature is maintained in a range of an optimum crystal growth temperature.