Method for making a low density thermally recyclable polymer foam

Abstract

A 2-step processing method to form a partly cross-linked polyurethane (PU) comprising foam having densities below 600 kg/m3, preferably in the range 20-300 kg/m3, said method comprising: A first processing which comprises at least following steps: a) providing a reactive mixture comprising an isocyanate composition comprising at least one isocyanate compound, an isocyanate-reactive composition comprising at least one isocyanate reactive compound, a crosslinking agent and a blowing agent composition comprising at least a heat activatable blowing agent which is heat activatable to achieve blowing at an activation temperature Tactivate, and b) allowing the reactive mixture to polymerize, optionally using a shape or mold, at a process temperature Tprocess wherein Tprocess<Tactivate and Tprocess<Tmelt to form a polyurethane comprising material having a melting temperature Tmelt and which is solid at room temperature, and then A second processing which comprises at least following steps: c) placing the polyurethane comprising material in an autoclave, pressure vessel or pressurizable mold, d) subjecting the polyurethane comprising material to a temperature sufficient to soften the polymer material (Tsoftening) wherein Tsoftening≥Tactivate in combination with an elevated pressure P1 wherein P1 is higher than atmospheric pressure (Patm), and then subsequently e) subjecting the polyurethane comprising material to a pressure reduction which is sufficient to achieve expansion (foaming) and to obtain the partly cross-linked polyurethane comprising foam

Dependencies are inferred from the claim text.