Laminating adhesives are used for large-area bonding of individual foils and films to form laminates like PET/PE, or PET/AL/PP. The properties of the individual foils and films are combined in such a way that the laminate is suitable for subsequent use as a packaging material for the packaging of goods, such as, for example, foodstuffs, health care, medical or pharmaceutical articles or items which need protection from damage prior to first usage.
Laminating adhesives most often consist as a rule of isocyanate group-containing polyurethane binders. Most of the available laminating adhesive give, after cross-linking, are transparent appearance.
Due to legal regulations a very limited number of raw materials are permitted or suitable for the use in flexible packaging adhesives. Besides their damage to the environment because of the high content of volatile organic solvents, the necessity of high energy consuming drying tunnels to flash-off those solvents to achieve the demanding prooperties, even the necessary adhesive lay down needed for the production of the laminates is about two times higher than the lay down regarding solvent-free adhesives. The laminating adhesive must also be resistant to an effect called “tunneling”. which is the localized separating or delamination of the substrates caused by two films of different extensibility that stretch or relax at different rates. Other general considerations in selecting an adhesive for lamination include adhesion, mechanical bond strength, formulating flexibility, and heat and chemical resistance. One must also determine the ability of the adhesive to flow uniformly over the film’s surface and form a smooth continuous coting.
