| abstract |
Cold-seal adhesives are disclosed that contain no natural rubber and are capable of forming dry coatings on flexible films which adhere to one another with commercially acceptable packaging strength at room temperature by pressure contact, but also allow such layered substrates to be reeled into rolls and stored for extended periods of time without blocking. The flexible films are usable in forming packages, particularly for comestibles and pharmaceuticals, without need for heat sealing. Such cold-seal adhesives are aqueous dispersions having a Zahn Cup #2 viscosity between 16-40 seconds containing 30 to 50 percent solids content of a polyurethane ionomer reaction product of 50-80% polyester polyol, 15-25% aliphatic diisocyanate and 3-6% dimethylol propionic acid neutralized with a base selected from tertiary amines and alkali metal hydroxides and the reaction product possesses a Tg of between about -20 DEG to 5 DEG C. |