| 摘要 |
948,937. Film making apparatus. INTERNATIONAL DEVELOPMENT CO. OF NATIONAL DISTILLERS & CHEMICAL CORPORATION S.A. Sept. 22, 1960 [Oct. 6, 1959], No. 32629/60. Heading B5B. Either a continuous flat or a continuous tubular film is formed by extruding a molten or heat softened organic thermoplastic material through a slot die or an annular die to form a flat or a tubular film which is then passed through at least one cooling zone in which the film, if of the tubular type, is inflated and stretched to produce molecular orientation. The freshly extruded flat or tubular film is passed in a free path through a chamber or chimney which extends between the die and the cooling zone and forms an annealing zone. The temperature of the freshly extruded film during its passage through the chimney is maintained between the extrusion temperature and a temperature not more than 50‹ F. below the extrusion temperature. As shown in Fig. 1, the heated thermoplastic material is expelled from the extruder 1 through the elbow 5 in which its temperature is maintained by the electric resistance heater 27 and extruded through the annular extrusion orifice 17, to form a tubular film which is drawn from the orifice by nip rolls 31 and 33 and inflated by the introduction of slightly pressurized air through the conduits 23, 19 and 21. In conventional operation, the film is subjected to shock cooling as soon as it leaves the die by means such as an annular hollow body 41 having an inner wall 43 provided with a ring of ports 49 through which a slightly pressurized flow of air from a conduit 45 is discharged against the film. In conventional apparatus the member 41 is disposed immediately above the extrusion orifice. In the present invention the cooling zone, in this case provided by the member 41, is disposed axially in spaced relation to the extrusion orifice 17 by a distance of, for example, about 4 to about 28 inches, preferably about 6 to 10 inches. In this space between the cooling ring 41 and the upper end 9 of the die is disposed an annealing chimney 51 consisting of a vertical metal tube of which the lower end portion is threaded to be engaged by a coupling nut 53 also adapted to engage the upper end 9 of the die. The chimney 51 is lagged with a thermal insulation jacket 55 or may be enclosed in a cylindrical electrical heating jacket. The ratio of the internal diameter of the chimney 51 to the outer diameter of the die extrusion orifice may range from about 1.1 to 1 to about 4 to 1, preferably about 2: 1 to about 3: 1. The chimney may be split longitudinally in two removably mounted halves to obviate the necessity for threading the film through a one-part chimney at the commencement of film production. The process and apparatus of the invention enable films of improved gloss and transparency to be produced. |
