| 摘要 |
1,264,852. Extruding foamed plastics sheet. MONSANTO CHEMICALS Ltd. 18 March, 1970 [15 April, 1969], No. 19187/69. Heading B5A. [Also in Division C3] Widthwise expansion and consequent surface corrugation of an extruded foamed thermoplastics sheet or film 6 e.g. of 0À02 to 0À5 inch thickness, is restricted e.g. to below 15%, by adherence of the extrudate during expansion thereof to an endless moving arcuate surface e.g. a cylindrical roller of 1 to 10 inch diameter, which is cooled to a temperature below the softening point of the thermoplastics, and is located at 0À02 to 0À5 inch from the orifice 5 of a heated extruder 1. In the particular examples, the sheet or film 6 is produced from polyethylene or ethylene/vinyl acetate copolymer including calcium propionate nucleating agent and using, as blowing agent, nitrogen injected into the extruder barrel; polystyrene including talc nucleating agent and using carbon dioxide injected into the barrel. Various other thermoplastics, blowing agents of a gaseous liquid or decomposable solid nature and nucleating agents are referred to in the Specification. The expanded sheet preferably comprises closed cells of 0À001 to 0À05 inch diameter. Expansion of the sheet 6 may continue after removal from the roller 6, which may be idle or driven by a variable speed drive, and may be air cooled on the external surface thereof, or may be internally air or water cooled. The sheet 6 is drawn from the roller 7 by a roller nip or endless track mechanism and may be further calendered to impart a glossy or matted surface thereto, and may be laminated to film. |
