Patent GB-1012923-A (GB)
Title: Process and apparatus for the surface treatment of polymeric film
IPC: B29C59/08
Filed: 1962-10-04
Abstract: 1,012,923. Films. E. I. DUPONT DE NEMOURS & CO. Sept. 24, 1963 [Sept. 24, 1962], No. 37582/63. Heading B5B. The flame-treatment of continuous polymeric film is effected by bringing the film F continuously into intimate contact with a thermally-conductive surface and while in contact therewith passing the film through the flame of an elongated burner spaced from and disposed parallel to the film and transversely to the direction of travel thereof, to heat the surface of the film exposed to the flame to an elevated temperature, the thermally-conductive surface opposite said flame being maintained at a temperature substantially below said elevated temperature, and directing a narrow stream of substantially inert gas through the gap between the film and the burner in the vicinity of the edge of the film and in a direction substantially parallel to the direction of travel thereof. As shown, film from roll 1 passes around idler roll 2, tension isolation roll 3, idler roll 4, nipping roll 5 in contact with the rotating metal treating roll 6 which is equipped for the internal circulation of a heat-transfer fluid, suitably water, passes through the flame of burner 7, under idler roll 8, over tension isolation roll 9 and under idler roll 10 to the driven wind-up roll 11. Jets of inert gas, e.g. air, nitrogen, helium or carbon dioxide are supplied through the nozzles 14, positioned below the burners and aimed upwards. Alternatively the nozzles may be positioned above the burner, aiming downward. The burner may alternatively be positioned above the treating roll directing its flame downward or below the treating roll directing its flame upward. In either of these arrangements, the nozzles 14 will be positioned to direct their jets in a substantially horizontal direction either in the direction of film travel or counter thereto. The nozzles are preferably skewed a few degrees away from a line parallel to the direction of film travel. Film speeds of 20 to 500 ft. per min. with gas rates of 0À05-0À75 standard cubic feet per min. are preferred, the gas stream being effective to extinguish that portion of the flame in the path of the stream. The gas stream may be moved laterally responsive to variations in the path of travel of the edge of the film through the flame, so as to maintain the stream in a fixed position with respect to the edge of the film. This may be effected manually, by suspending the jet delivery nozzles from a slotted traversing bar by keyed bushings, the lateral portion of which is manually variable through the action of hand-cranked worm gears. Preferably this is effected automatically, as shown, by means of edge-sensing nozzles 15 at either edge of the film. A pneumatic pressure signal from the upper jaw of edge-sensing nozzle 15 passes through signal line 16 to controller 17, a pneumatic-hydraulic transducer. If the amplitude of the signal varies from a pre-set value, owing to the film edge varying laterally from a pre-determined position, the controller acts through the hydraulic lines 18 to establish a differential hydraulic pressure across the piston 23 in cylinder 12 of such magnitude and direction that the piston, and thus the nozzle 15, is moved to a position which restores the pneumatic signal to its pre-set value, so that the position of the nozzle 14 in relation to the edge of the film is unchanged. In examples, films of polyvinyl fluoride, polyvinyl chloride, isotactic linear polypropylene, high density linear polyethylene, and low density branched polyethylene are so treated. The method eliminates film edge distortion caused by overheating during flame treatment, and enables untreated margins or lanes to be provided on the film being treated.