EXPANDABLE POLYSTYRENE-BASED COMPOSITION, PRE-EXPANDING PROCESS AND PROCESS FOR PREPARING SAID COMPOSITION

摘要

The invention relates to a polymeric composition based on expandable polystyrene comprising: (a) 100 parts by weight of a styrene polymer having an average molecular mass of 150000...300000 and a content of residue monomer of less than 2000 ppm, (b) 2...9 parts by weight of at least one blowing agent containing n-pentane, (c) from 0.1 to less than 1.0 parts by weight of a petroleum wax comprising a mixture of C18-C80 alkanes and (d) up to 1.0 parts by weight of a cell-forming agent selected from Fischer-Tropsch synthetic wax and polyolefin wax. The claimed composition allows the improvement of the granule pre-expansion stage by increasing the granule expansion rate and by improving the efficiency of the pre-expansion stage without substantially affecting the final mould pressing stage.