Coatings binders adhere directly to aluminum without adding a promoter
A new generation of heat-sealing bead polymers reduces the complexity of coating formulation because only a single binder is used and only one solvent is therefore necessary.
Methacrylate binders from Evonik, marketed as “Degalan”, offer good possibilities for formulation of heat-sealing lacquers. They are used in the sealing of yoghurt containers and Pharmaceutical blister packaging.
The requirements placed on packaging coatings are high because packaging substrates can vary widely. Yogurt lids, for example, consist of aluminum or plastic; these in turn must be sealed to a variety of container materials such as polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET).
Heat seal strength on a variety of substrates
“Degalan VP P 34” is a bead polymer that is easily soluble in ethyl acetate, a commonly used, highly volatile solvent for heat-sealing lacquers. Formulations can be applied directly on the aluminum foil so that primers or formulations with a PVC-based adhesion promoter, which are still necessary today, can now be dispensed with.
A further advantage is the heat seal strength on a variety of substrates and over a range of temperatures. A coating based on the product applied on aluminum foil and sealed against PVC blister packs, has a heat seal strength exceeding 7 N/15mm at a sealing temperature of 180°C. For yogurt lids sealed against PS this same heat seal strength can be attained at a sealing temperature of only 140°C.
