PROCEDURES FOR THE ESTABLISHMENT OF AN INVESTIGATED GRANULATE AND PROCEDURE FOR THE PRODUCTION OF AN INVESTIGATED GRANULATE

摘要

A method for producing a foamed granulate, wherein a thermoplastic synthetic material is placed in an extruder, the synthetic material is melted, a pressurized expanding agent is fed through one or several injection nozzles, the molten material enriched with the expanding medium is foamed as it exits through a perforated plate arranged at the outlet of the extruder and is granulated by a cutting device arranged behind the perforated plate. Also disclosed is a device for implementing the method and the foamed granulate. The invention is characterized in that the molten material is cooled in a controlled manner as it comes out of the perforated plate and exits directly into a flowing cooling medium, in that the temperature of the molten material and the temperature and pressure of the cooling medium are regulated in such a way that once the molten material exits the perforated plate, the surface of the molten material is directly hardened into a closed film with a smooth surface having a thickness that ranges from 10 to 500 mum, preferably 20 to 200 mum, whereupon the molten material is foamed and a granulate with a rounded surface and a bulk density of 10 to 600 g/l is formed. A semi-spherical granulate with a smooth surface is thus obtained.