A METHOD AND APPARATUS FOR PRODUCING MULTI-LAYER EXPANDED FILMS

摘要

Method and apparatus for forming multi-layer expanded film. A base film extruded by a die is coated, immediately downstream of the die mouth, by a further layer of fluid propelled from a manifold through a metering orifice. The combination of manifold and metering orifice is necessary to permit accurate control of the flow rate of the fluid and hence of the thickness of the coating, and the mouth of the die and the metering orifice must be very close so that the base film is as resistant as possible to deflection by the impact of the coating fluid, and so that contact takes place before any substantially expansion has taken place. The downstream end of the resulting multi-layer tubular film is then held closed in known fashion and the closed tube is expanded by air under pressure admitted by an opening in the die.