Process for continuous production of laminated structures comprising foamed plastic layers

Claim 1

A PROCESS FOR CONTINUOUS PRODUCTION OF LAMINATED STRUCTURES BY BONDING A PREEXPANDED, RIGID, FOAMED PLASTIC LAYER OF THE CLOSED-CELL TYPE FORMED ESSENTIALLY OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF POLYVINYL CHLORIDE AND COPOLYMERS THEREOF, WITH AT LEAST ONE OUTER LAYER, SAID PROCESS COMPRISING THE STEPS OF PROVIDING AT LEAST ONE OF THE LAYERS WITH AN ADHESIVE COAT; MOVING THE LAYERS THROUGH A HEATING ZONE AT THE SAME RATE OF SPEED AND IN THE SAME DIRECTION IN SUCH A WAY THAT THE ADHESIVE COAT IS LOCATED THEREBETWEEN AND SIMULTANEOUSLY HEATING THE OUTER LAYER TO SUCH AN EXTENT THAT THE HEAT PENETRATES AT LEAST TO SAID ADHESIVE COAT, SUBJECTING THE LAYERS TO EXTERNAL COMPRESSIVE FORCE WHILE THE LAYERS PASS THROUGH AT LEAST A PORTION OF SAID HEATING ZONE WHEREBY THE LAYERS ARE BONDED TO EACH OTHER UNDER THE ACTION AND HEAT AND PRESSURE; MOVING THE BONDED LAYERS THROUGH A COOLING ZONE WHEREBY THE GAS PRESSURE IN THE CLOSED CELLS OF SAID FOAMED LAYER WILL BE REDUCED; AND SUBJECTING THE BONDED LAYERS TO EXTERNAL PROGRESSIVELY INCREASING COMPRESSIVE FOCE SUFFICIENT TO AT LEAST COMPENSATE SAID REDUCTION IN GAS PRESSURE IN SAID CLOSED CELLS WHILE THE LAYERS PASS THROUGH SAID COOLING ZONE.