Abstract: A method for joining foils which includes the steps of mechanically coating at a high speed at least one of the foil sides to be joined with a reaction product of a hydroxy-functional polyethers or polyesters with polyisocyanates or polyisothiocyanates, said reaction product containing free --NCO or --NCS groups and being reactable with H-acid compounds, and subsequently laminating foils. The reaction product has an average molecular weight of from about 500-10,000 and a --NCO or --NCS group content of from about 1-10% by weight, is substantially solvent-free when applied and has a viscosity of at most 60 Pas under application conditions. The temperature of the reaction product application conditions is adjusted to at most 140.degree. C but not less than a temperature which is so far below the temperature of the ambient air that air humidity will be condensed in the reaction product to be applied in such an amount that its pot-life would drop the value required for the implementation of the method.