Method and a device for preparation of expanded microspheres

摘要

The invention relates to a method and a device for the preparation of expanded thermoplastic microspheres from unexpanded thermally expandable thermoplastic microspheres comprising a thermoplastic polymer shell encapsulating a blowing agent. The method comprises: (a) feeding a slurry of such expandable thermoplastic microspheres in a liquid medium into a heating zone; (b) heating the slurry in the heating zone, without direct contact with any fluid heat transfer medium, so the expandable microspheres reach at least a temperature at which they would have started to expand at atmospheric pressure, and maintaining a pressure in the heating zone sufficiently high so the microspheres in the slurry do notfullyexpand; and, (c) withdrawing the slurry of expandable microspheres from the heating zone into a zone with a pressure sufficiently low for the microspheres to expand.