Polyurethane adhesives are generally known. Especially PU adhesives for laminating multilayer films. The adhesives suitable according to the application are one component polyurethane adhesives or two-component polyurethane adhesives. The adhesives may be liquid, but they may also be hot-melt adhesives. The adhesives may contain solvent, but they are preferably solvent-free. Crosslinking of the polyurethane adhesive suitable according to the application is based on the reaction of reactive NCO groups.
Dry laminations are those in which the liquid adhesive is first dried before lamination.
Lamination adhesive is then in the dry solid or slightly tacky stage when joined with the other substrate. The bonding is generally achieved during a high temperature, high pressure nip. The temperature and pressure are sufficient to cause the adhesive to flow and create an instantaneous bond when it cools and gels. Dry lamination can be applied to a broader range of products such as film-to-film and film-to-foil bonding.
Adhesive lamination is the preferred joining process when a specific film composition cannot be effectively run in a coextrusion system due to equipment limitations or when the high temperatures required in coextrusion would be harmful to the film. Adhesive lamination is also preferred when the adhesive itself can provide additional functionality to the final product.
