In extrusion coating and lamination, resin is melted and formed into thin hot film, which is coated onto a moving, flat substrate such as paper, paperboard, metal foil, or plastic film. The coated substrate then passes between a set of counter-rotating rolls, which press the coating onto the substrate to ensure complete contact and adhesion.
Extrusion laminating, also called sandwich laminating, is a process related to extrusion coating. However, in this case, the extrusion coated layer is used as an adhesive layer between two or more substrates. A second layer is applied to the extrusion coating while it is still hot and then the sandwich is pressed together by pressure rolls. The extrusion coated layer may also serve as a moisture barrier.