VERFAHREN UND EINRICHTUNG ZUM HERSTELLEN VON KASCHIERTEN THERMOPLASTISCHEN SCHAUMSTOFFBAHNEN

摘要

Laminated thermoplastics foam sheet, esp. of polystyrene foam, is mfd. The foamable plastics is melted in an extruder and mixed with an expanding agent, then extruded in the form of a tube, blown to expand its diameter and cooled; it is then longitudinally slit, laid flat to form a sheet and passed through a hot water bath to steam chest. The surface sheets are then applied to both sides of it and the resultant laminated material is hardened. Pref. the sheet is held parallel at its longitudinal sides during the expansion of the foam. After expansion, the moisture may be extracted by vacuum. By comparison with a previous process, where the material was initially foamed with the cells expanding on leaving the extruder, later stored for about two days after cutting into sheets and then finally subjected to a second foaming stage, the new arrangement achieves a higher degree of foaming in one single process. It is found that the use of a hot water bath or steam, chest causes the cells to expand and produce the foam structure but does not allow them to collapse due to softening of the walls.