PROCESS FOR REDUCING THE DENSITY OF AN EXTRUDED FOAM BOARD OF A THERMOPLASTIC RESIN

摘要

The density of an extruded foam board (32) of a thermoplastic resin which board has a thickness of 1 cm or more is reduced by exposing the foam board simultaneously or in sequence to heated air and steam. The density reduction can be carried out in an expansion device (11) which comprises at least one chamber 12 in which simultaneously an atmosphere of steam and heated air is maintained. The chamber (12) is provided with a steam inlet port (14) which is in communication with a steam source (16) and with an air inlet port (18) which is in communication with an air source (20). The invention allows to control the density reduction of a foam material without influencing the supply of the installation and under atmosphere pressure.