| 摘要 |
1,122,416. Melt extruding flat film. J. P. BEMBERG A.G. 30 Nov., 1965 [1 Dec., 1964], No. 50803/65. Heading B5B. In producing highly transparent flat film by melt extruding a synthetic organic polymeric material through a slot die on to an internally cooled cooling roll and contacting the film during its passage over the draw roll with a liquid coolant, the extrusion die and the draw roll are relatively so disposed that the length of the free path of travel of the film through the air from the extrusion die to the line at which the film first contacts the draw roll is short and the peripheral outer surface of the draw roll is continuously coated with a liquid coolant containing an anti-blocking agent either by arranging for the draw roll to be immersed to a shallow depth in a bath of the coolant in such a manner that both a portion of the peripheral surface of the draw roll covered by the film and a portion of the peripheral surface of the draw roll emerging from the bath and not covered by the film is immersed in the bath of coolant. Alternatively, the draw roll may be entirely surrounded by air and the liquid coolant sprayed on to a portion of the peripheral surface of the draw roll approaching the line of first contact of the film with the draw roll. In this case the film is caused to pass to a second draw roll over and in contact with which it travels in such a manner that the surface of the film which was exposed to the air during the passage of the film over the first draw roll is in contact with the peripheral surface of the second draw roll and liquid coolant is sprayed on to the surface of the second draw roll approaching the line of first contact of the film with the second draw roll. The liquid coolant may be water, the surface tension of which has been reduced by the addition of a wetting agent, an organic liquid which is a non-solvent for the film material (such as isopropanol) or an aqueous dispersion of a synthetic organic polymeric material. The coolant may contain an anti-static agent. |
