| 摘要 |
The present specification discloses a method and apparatus for use in the production of plastics film and sheet. A well know system for producing thermoplastics film and sheet comprises the cooling of a molten film by casting the material onto the surface of a rotating metal drum (1). The drum (1) is cooled by passing, for example, water through the hollow interior of the drum. The cooling water is circulated by passageways in the drum (1). If sufficient heat is not conveyed away by the water then the plastics material will stick to the drum (1). The problem arises in that a boundary layer of warm water tends to stay adjacent to the inside wall (21) of the drum (1), acting as a barrier to further heat transfer. This thus impedes the allowable speed of production. The present invention provides for the cooling fluid to be atomised and sprayed at high velocity onto the inside wall (21) of the drum (1), the sprayed fluid breaking up the boundary layer (25) and enhancing the cooling effect. Further, the cooling fluid collected at the bottom of the preferably horizontal drum (1), is pumped away continuously to further enhance the cooling effect. This improved cooling allows for higher speed production as compared to prior art arrangements. |
