| 摘要 |
1,224,395. Making tubular film of thermoplastic synthetic resin. MITSUBISHI YUKA K.K. 9 May, 1968 [9 May, 1967], No. 22003/68. Heading B5B. In the manufacture of tubular film of thermoplastic synthetic polymeric material by melt extruding the material downwards through an annular orifice simultaneously expanding the film radially to a predetermined degree by introducing pressurized air into the interior of the film, drawing the inflated tubular film thereby formed through a bath of cooling liquid below the extrusion die, and thereafter through the nip of a pair of nip rolls, the film during its passage through the bath of cooling liquid is caused to travel along mutually opposed flat apertured surfaces immersed in the bath. The aperture of the surfaces communicate with suction means and the film is folded to a flat form and cooled, the suction applied to the apertures holding the film against the surfaces and drawing cooling liquid between the film and the surfaces and into the apertures. As shown in Fig. 1, a tubular film f is melt extruded downwards through the annular orifice of a die 1 and is drawn by the nip rolls 14 into a bath of a cooling liquid 3 in which are immersed two suction boxes 5 facing one another. The opposed flat surfaces 6 of boxes 5 are provided with apertures and may, for example, be fine mesh wire screens through which the cooling liquid 3 can be sucked into chambers 7 within the boxes 5 by means of suction tubes 9 communicating with the chambers 7 and leading to a circulating pump 8 which returns the liquid through duet 11 to the lower part of the tank 2. Duct 11 may include means for cooling the liquid. The portion of the film between the die and the surface of the cooling bath is expanded radially to a predetermined degree in the usual manner by the introduction of air at a constant controlled pressure into the interior of the film. The flattened film after leaving the nip rolls 14 is drawn over a guide roll 15 and between rolls 16 to a wind-up roll 17 outside the cooling tank. As shown in Fig. 1 the mutually opposed surfaces 6 of the suction boxes converge in the direction of travel of the film. |
