Question: Francesca asks “is it possible to avoid the problem of consistent wetting and reaction of the primer and the aluminum oxide surface of the metallized films by using a particular adhesive (for example with amino silanes) for the lamination?”
Answer: This is a good question as it highlights the effect of metal surface contamination when wouldn in a roll. As explained in the post ” Aluminum layer contamination in wound rolls of metallized films” the metal surface is contaminated by migratory additives in the film while wound in roll form. So the question is what to do to obtain uniform converting of the metal surface with a primer.
In my experience I usually tell people that if you want uniform printing of metallized surfaces you need to prime, but to get uniform priming you have to treat the metal surface to clean it of the organic contamination which interferes with the uniform wetting of the metal surface with the primer. In this case I don’t think the chemical functionality of the primer, by itself, will make much difference to improving the wetting and reaction of the primer /aluminum surface as long as the surface contamination remains. However, if the primer can dissolve the surface contamination to clean the surface then you might be able to eliminate the surface cleaning retreatment of the aluminum surface.
So the use of a two part primer or adhesive might work if it dissolved the surface contamination. Likewise the use of a solvent bourn adhesive or primer might dissolve the contamination and allow wetting and reaction of the primer or adhesive to the metal surface. But if the surface contamination is too great there may not be enough time for the solvent to cut through it and expose the metal surface to the reactive sites of the primer or adhesive. Also, it is unlikely that water based systems will wet the metal surface if it is covered with the migratory additives.
So to insure the uniformity of the priming process I would still recommend that the metal surface was cleaned by a retreatment process. Of course you need to be careful and not overdo the treatment, especially with a heat sealable film as it could hurt the heat sealing properties of the film (could increase the seal initiation temperature)