| 摘要 |
1,093,018. Polyolefin films. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. Sept. 8, 1966. No. 40188/66 Heading B5B. In a process for the manufacture of a polyolefin film an extruded, internally blown tubular film 4 is drawn downwards from an extruder 2 into a body of cooling liquid 6 within which the tubular film is fully collapsed to lay-flat form, said film being mainly but not completely collapsed to lay-flat form by passage between a pair of parallel, spaced-apart, chilling rollers 9, 10 disposed at the surface of the body of cooling liquid for rotation, partly immersed therein in positions such that the chilling rollers support, but do not nip, the film as it enters the body of cooling liquid. Preferably, the chilling rollers are disposed with their axes of rotation lying substantially within the plane containing the surface of the body of liquid. Cooling liquid adhering to each of said chilling rollers may be removed prior to its contacting said tubular film, e.g. by a doctor blade, or alternatively, where cooling water is used the water may contain a surface-active agent in an amount sufficient to ensure the formation of an even water film on the surface of each chilling roller. Suitably, the surfaces of the rollers are chromium plated, and the cooling liquid is preferably water maintained at a temperature at least 50‹ C. below the softening point of the polyolefin, and especially the cooling liquid is water maintained at a temperature within the range 10‹ to 20‹ C. The vertical distance between the annular extrusion orifice of the die and the surface of the body of the cooling liquid for polypropylene film manufacture is suitably between 6 and 20 inches, especially from 11 to 15 inches, and the diameter of the chilling rollers should be chosen so as to provide adequate support for the maximum film width contemplated; in general chilling rollers 10 inches in diameter are suitable for the manufacture of polypropylene films. In apparatus as shown, the partially collapsed film is fully collapsed to lay-flat condition by means of nipping rollers 11 disposed wholly within the body of the cooling liquid, and a circulation of the cooling water is provided by means of water inlet 7, water outlet 8 and weir 81. |
