Patent ID: 8641854

Claim:
A method comprising: providing a co-extruded, multilayer, and biaxially-oriented polypropylene film comprising: (A) at least one first heat sealable covering layer comprising at least 80% by weight of an ethylene polymer, a propylene polymer, or a mixture thereof; and (B) at least one vacuolate layer comprising at least one propylene polymer having a thickness of at least 5 μm; irradiated the co-extruded, multilayer, and biaxially-oriented polypropylene film with electrons on the side opposing said at least one first heat sealable covering layer; wherein the at least one first sealable covering layer has a Hot Tack value, wherein the Hot Tack value after irradiation with electrons is less than or equal to 10% below the Hot Tack value before irradiation with electrons and is capable of.