Currently, general-purpose solvent-free adhesives used for soft packaging lamination mainly have the following problems:
(1) Great influence on the slipperiness of PE film
When the curing temperature of solvent-free lamination is higher than 40°C, it has a significant impact on the solvent-free laminated film with PE film as the inner layer (especially for the structure where the thickness of the PE film is less than 45μm). It is prone to the phenomenon of a significantly increased coefficient of friction. This is mainly because the higher the curing temperature, the more intense the molecular movement of the slip agent in the PE film. The slip agent is likely to migrate to the adhesive layer and react with it, thus being consumed. Eventually, this leads to an increase in the coefficient of friction of the laminated film.
(2) Transfer of the aluminized layer
For aluminized films, especially polyester aluminized films (VMPET), the transfer of the aluminized layer is likely to occur during the solvent-free lamination process, resulting in insufficient peeling strength of the laminated film.
(3) Dissolution with the ink
During the solvent-free lamination process, sometimes the phenomenon of the adhesive dissolving with the ink will occur, especially for dye-based inks.