Abstract: Extrusion machine and process, the machine having a barrel having a feed section for receiving solid extrusion material, and containing a screw for moving the solid extrusion material through a solids conveying section to a compression section of the barrel to generate heat and pressure to melt the extrusion material and force the melt through a downstream extrusion die. The solids conveying section of the barrel has a cross-section comprising a plurality of flat or slightly curved surfaces which extend substantially tangentially relative to the extrusion screw circumference, providing axial recesses which restrain the rotation of the solid extrusion material with the screw as it is moved axially into the compression section. The present machine and process causes plastic extrusion composition to be packed as a non-rotating mass to fill the solids-conveying and compression sections and increase the dead head pressure and extrusion output of the machine.

Abstract: Extrusion process and apparatus, the apparatus including an extrusion barrel having axial grooves which extend through the feed section and solids conveying section and disappear at the exit end of the compression section. The apparatus also includes a helical thread extrusion screw having a maximum channel depth in the feed section, which depth disappears at the exit end thereof. The process and apparatus causes plastic extrusion composition to be packed as a non-rotating mass to fill the solids-conveying and compression sections and increase the dead head pressure and extrusion output of the apparatus.

Abstract: A method and apparatus for continually metering a gaseous blowing agent in an accurate and precise manner into a molten resin charge, such as polystyrene. This is accomplished by a free piston-cylinder combination which is actuated by the gas blowing agent and which continually meters discrete uniform volumetric charges of the gaseous agent into the molten resin. The blowing agent is uniformly distributed throughout the resin charge and extruded into a region of lower pressure to yield a foamed structure.

Abstract: Thermoplastic foams of polystyrene, for example, are prepared with a blowing agent which is a mixture of an organic plasticizing blowing agent, such as pentane, and an atmospheric gas, such as carbon dioxide. Typically, such foams prepared with organic blowing agent alone were aged prior to thermoforming the foam into articles. Foams prepared with the mixed blowing agent of this invention exhibit the advantage of reduced atmospheric emissions on aging.

Abstract: Polymer foam is extruded as a tube or sheet into a cooling liquid which is maintained at a temperature up to about 85.degree. C. Either one or both surfaces of the polymer are cooled as the extrudate emerging from the die orifice passes through the liquid. Styrenic polymer foam extrudate produced by such a method exhibits excellent puncture resistance and tensile properties.

Abstract: A continuous foam production system is disclosed wherein a molten thermoplastic resin is mixed with volatile blowing agent at elevated pressure to form an extrusion mass. A helical screw extruder means is adapted to extrude the molten resin with volatile blowing agent into a low pressure foaming zone to form a foam sheet, tube or other shape. An improved fluid handling system includes storage means for holding at least one of a plurality of disparate volatile liquids under pressure sufficient to maintain a normally gaseous blowing agent in liquified state and cooling means for receiving a pressurized first stream of liquified thermally-gaseous blowing agent and cooling below its autogenous temperature. A pump operatively connected between the cooling means and extruder means increases pressure of the first stream higher than the elevated pressure of the extruder, where it may be combined with a pressurized stream of second liquid blowing agent.