The requirements placed on packaging coatings are high because packaging substrates can vary widely, the company said. 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).
Evonik’s methacrylate experts have now succeeded in developing a new generation of heat-sealing bead polymers. DEGALAN VP P 34 reduces the complexity of coating formulation enormously because only a single binder is used and only one solvent is therefore necessary. The reason is that DEGALAN VP P 34 is a bead polymer that is easily soluble in ethyl acetate, a commonly used, highly volatile solvent for heat-sealing lacquer formulations.
DEGALAN VP P 34 based formulations can be applied directly on aluminum foil. A coating based on DEGALAN VP P34 applied on aluminum foil and sealed against PVC blister packs, has a heat seal strength exceeding 7 N/15 mm 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.