1,168,273. Embossing. IMPERIAL CHEMICAL INDUSTRIES Ltd. 20 Nov., 1967 [25 Nov., 1966], No. 52825/66. Heading B6J. A thermoplastic sheet is embossed by arranging the sheet to face the embossing surface of a non-porous embossing medium, applying suction to the space between the sheet and the embossing surface, forcing the sheet into intimate contact with the embossing surface by means of a flexible diaphragm, applying heat to the thermoplastic sheet and removing the embossed sheet from the embossing surface. As shown, Fig. 1, a thermoplastic sheet 6 (e.g. vinyl polymer or copolymer 1 lies between a flexible, non-pourous diaphragm 3 (of metal, silicone elastomer or plastics material), and the embossing surface of embossing medium 7 (of metal, silicone elastomer or glass). Air is evacuated simultaneously from compartments 1 and 2 and then air is admitted to compartment 2, thus forcing diaphragm 3, sheet 6 and medium 7 against heated surface 8. Air ie then admitted to compartment 1 to equalize the pressure and the embossed sheet is stripped from the embossing surface before or after cooling. Diaphragm 3 may be provided with an embossing pattern and may be used in place of or in addition to medium 7. In an alternative embodiment (Fig. 2) sheet 6 serves as the diaphragm and the embossing surface 7 is placed directly on top of it. In a further embodiment the embossing medium may be maintained in permanent contact with a heat source. Heating of the sheet and/or the medium may be effected by conduction or radiation or electronically. Sheet 6 may be provided with a supporting cellular layer of thermoplastic material.
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