| 摘要 |
1,166,937. Extruding foamed resins. MONSANTO CHEMICALS Ltd. 3 April, 1968 [19 May, 1967], No. 23303/67. Heading B5A. [Also in Division C3] A foamed resin board is made by extruding a foamable, thermoplastic polyvinylaromatic resin through a rectangular die orifice into a zone of lower pressure defined by a pair of opposing concave surfaces maintained at a temperature below the extrusion temperature (i.e. temperature of the unfoamed resin at the die orifice) so that the resin foams in the zone, and wherein the surfaces are shaped so that they do not exert any substantial pressure on the foaming resin. The zone defining surfaces (which may initially comprise arcs of circles) reach their greatest separation where the foamed resin has fully expanded and thereafter extend parallel to each other. The parallel section may comprise movable belts, driven by contact with the foamed polymer. The die used may be as specified in British Patents 1,034,120, 1,084,000, 1,098,408 or 1,159,920, and the lower pressure zone is preferably cooled to a temperature 60-105‹ C. below that of the extrusion temperature by water cooling of concave surfaces. The maximum separation of the zone defining surfaces is preferably 1À2 to 4 times the height of the die nozzles producing a board between 1À5 and 4 inches thick of density 0À9 to 1À5 1bs. per cubic ft. Many suitable resins and blowing agents are described; the preferred resin being polystyrene. |
