Apparatus for the extrusion of cellular thermoplastic material

摘要

The invention provides apparatus for the production of cellular thermoplastic material comprising an extruder having a hollow barrel, screw means mounted in said barrel to advance material therethrough, mixer head means mounted in said barrel and gaseous blowing agent inlet means positioned in said barrel near the upstream end of said mixer head means, said mixer head means having in the surface thereof a plurality of alternate land and groove means, said land means having close clearance with the internal walls of said barrel near the upstream end thereof in the region of said blowing agent inlet means and alternately spaced and close clearance with said walls in the mixing region downstream of said blowing agent inlet means.