PROCESS FOR THE PRODUCTION OF FOAMED POLYSTYRENE SHEETS

摘要

The invention relates to a process for manufacturing a multi-layer, preferable twin-layer composite of a polystyrene foam film and a coextruded unfoamed film, especially for further processing into labels or mouldings making use of the shrinking capacity of the films, in which a polystyrene material is extruded together with nitrogen as the blowing agent and a pore former from the nozzle (16) of an extruder (2) and the extruded material is blown below the softening point before cooling. In order to produce polystyrene foam film which is as aging-resistant and easily printed as possible with the greatest possible saving in material and as reliably as possible, the invention proposes that 1/30 to 1/50 nitrogen (measured in NL) of the weight of the film (expressed in grams per square metre) be used as the blowing agent per kilogram of foam film, together with a powdered mixture of sodium bicarbonate and citric acid, and that the rigidity/surface quality of the film be controlled by the blowing ratio.