PP PE

PP and PE are very difficult for most adhesives to adhere to. Typically they need some priming or surface treatment (corona, plasma, flame,...) in order for there to be any adhesion beyond the level of Post-It notes. With water soluble adhesives, you are going to need the maximum amount of treatment you can get. Once you have treated the films, apply the adhesive as soon as possible, as the surface treatments will fade over time, (days and months, not hours).

A google search for "water soluble adhesive" will give you lots of leads for suppliers.

Ciao, John

Chlorinated polyolefins stick well, and are available as a dispersion in water. However, they probably need various surface-active agents to avoid 'beading up'and also might need viscosity modification to turn into a working adhesive. There's no major problems I'm aware of but the question always is: how much do you need?

If it's between two layers of PP or PE then a further issue might be how you're going to dry the adhesive if it's water-base.

have fun