Process and apparatus for making a thermoplstic foam structure employing downstream injection of water

Abstract

Disclosed is a process for making a thermoplastic polymer foam structure with a blowing agent having water. The process comprises in sequence: a) melting the polymer to form a polymer melt; b) incorporating a brominated aliphatic fire retardant into the polymer melt; c) incorporating and mixing a first blowing agent into the polymer melt to form a first foamable gel; d) cooling the first foamable gel to a suitable foaming temperature; e) incorporating and mixing a second blowing agent comprising water into the cooled first foamable gel to form a second foamable gel; f) optionally further cooling the second foamable gel to a suitable foaming temperature; and g) extruding the second foamable gel through an extrusion die to form a foam structure. Incorporating of the water blowing agent downstream in the process after the foamable gel has been cooled reduces or minimizes process corrosion problems. Further disclosed is an apparatus for making the foam structure.

Dependencies are inferred from the claim text.