Apparatus for continuously forming a blown film

摘要

An apparatus is used in the continuous extrusion of blown films which includes a die suitable for use in forming a blown film bubble, and one or more primary gas outlets for use in stretching and drawing the extruded film prior to it stabilizing. The primary gas outlets direct cooling gas streams on the interior and/or exterior surface of an unstabilized portion of the blown film bubble as it emerges from the die. Secondary cooling gas outlets are also provided to introduce secondary gas streams into an upper stabilized portion of the blown film bubble above the bubble frost line. An exhaust conduit in gaseous communication with an interior of the bubble is used to maintain the gas pressure in the blown film bubble interior at a desired pressure. The exhaust inlet is located at a position adjacent the bubble frost line spaced away from the primary cooling gas outlets and marginally towards the secondary gas outlet.