| 摘要 |
<p>A sheet material (1) for use in packaging substances requiring a stable barrier layer and a method for producing same are provided. The packaging material comprises a substrate sheet (3) coated with a layer of polyvinylidene chloride copolymer (7) having a thickness of at least 10 micrometers. Preferably, a thin layer of primer material (5) is located between the polyvinylidene chloride copolymer layer (7) and the substrate (3). The sheet material is prepared by extruding a single layer of polyvinylidene chloride copolymer (7) onto a moving sheet of the substrate (3). A standard coat hanger die which has been modified to provide shortened flow paths for the polyvinylidene chloride copolymer is utilized for the extrusion process. Prior to introducing the polyvinylidene chloride copolymer into the die, the inner surfaces of the flow paths in the die are coated with polyethylene in order to minimize adherence of polyvinylidene chloride copolymer to the inner surfaces of the flow paths.</p> |
