Preparation of foamed thermoplastic resin forms having wrinkle-free profile surfaces

Claim 1

A METHOD FOR PREPARING CONTINUOUS FOAMED THERMOPLASTIC RESIN FORMS HAVING SMOOTH, SUBSTANTIALLY WRINKLEFREE PROFILE SURFACES WHICH COMPRISES EXTRUDING A FOAMABLE THERMOPLASTIC RESIN COMPOSITION THROUGH AN ORIFICE INTO A FORMING DIE ADAPTED TO APPLY PRESSURE ON THE PROFILE OF THE EXTRUDED FORM, SAID FORMING DIE BEING DEFINED BY A PLURALITY OF SURFACES WHICH ARE DRIVEN IN THE DIRECTION OF EXTRUSION, THE RESIN FOAM CONTACTING SURFACES OF SAID FORMING DIE CARRYING A COATING OF A POLYMER OF THE GROUP CONSISTING OF CHLOROTRIFLUOROETHYLENE, TETRAFLUOROETHYLENE AND MIXTURES THEREOF, THE EXTRUSION TEMPERATURE OF THE FOAMABLE THERMOPLASTIC RESIN COMPOSITION BEING SUFFICIENTLY HIGH TO EXPAND THE EXTRUDED FORM BEYOND THE PROFILE LIMITS OF THE FORMING DIE, THE RESIN FOAM CONTACTING SURFACES OF THE FORMING DIE BEING MAINTAINED BETWEEN 140* F. AND ABOUT 180* FF. AND THE DISTANCE BETWEEN THE FACE OF THE EXTRUDER DIE ORIFICE AND THE FORMING DIE BEING SUFFICIENTLY SHORT SO THAT WHEN THE EXTRUDED THERMOPLASTIC RESIN FORM CONTACTS THE FORMING DIE ITS PROFILE IS SUBSTANTIALLY A UNIFORM EXPANSION OF THE PROFILE OF THE EXTRUDER DIE ORIFICE, SAID FOAMABLE THERMOSPLASTIC RESIN COMPOSITION COMPRISING A THERMOSPLASTIC RESIN AND, AS A FOAMING AGENT, A NON-REACTIVE ORGANIC LIQUID WHICH HAS NOT MORE THAN A SLIGHT SOLVENT ACTION ON THE THERMOPLASTIC RESIN AND WHICH BOILS BELOW THE SOFTENING POINT OF THE THERMOPLASTIC RESIN.

Claim 2

A METHOD FOR PREPARING CONTINUOUS FOAMED THERMOPLASTIC RESIN FORMS HAVING SMOOTH, SUBSTANTIALLY WRINKLEFREE PROFILE SURFACES WHICH COMPRISES EXTRUDING A FOAMABLE THERMOPLASTIC RESIN COMPOSITION THROUGH AN ORIFICE INTO A FORMING DIE ADAPTED TO APPLY PRESSURE ON THE PROFILE OF THE EXTRUDED FORM, SAID FORMING DIE BEING DEFINED BY A PLURALITY OF SURFACES WHICH ARE DRIVEN IN THE DIRECTION OF EXTRUSION, THE RESIN FOAM CONTACTING SURFACES OF SAID FORMING DIE CARRYING A COATING OF A POLYMER OF THE GROUP CONSISTING OF CHLOROTRIFLUOROETHYLENE, TETRAFLUOROETHYLENE AND MIXTURES THEREOF, THE EXTRUSION TEMPERATURE OF THE FOAMABLE THERMOPLASTIC RESIN COMPOSITION BEING SUFFICIENTLY HIGH TO EXPAND THE EXTRUDED FORM BEYOND THE PROFILE LIMITS OF THE FORMING DIE, THE RESIN FOAM CONTACTING SURFACES OF THE FORMING DIE BEING MAINTAINED BETWEEN 140* F. AND ABOUT 180* FF. AND THE DISTANCE BETWEEN THE FACE OF THE EXTRUDER DIE ORIFICE AND THE FORMING DIE BEING SUFFICIENTLY SHORT SO THAT WHEN THE EXTRUDED THERMOPLASTIC RESIN FORM CONTACTS THE FORMING DIE ITS PROFILE IS SUBSTANTIALLY A UNIFORM EXPANSION OF THE PROFILE OF THE EXTRUDER DIE ORIFICE, SAID FOAMABLE THERMOSPLASTIC RESIN COMPOSITION COMPRISING A THERMOSPLASTIC RESIN AND, AS A FOAMING AGENT, A NON-REACTIVE ORGANIC LIQUID WHICH HAS NOT MORE THAN A SLIGHT SOLVENT ACTION ON THE THERMOPLASTIC RESIN AND WHICH BOILS BELOW THE SOFTENING POINT OF THE THERMOPLASTIC RESIN.