Patent ID: 8551285

Claim:
A method of making a multilayer protective film, the method comprising steps: (a) forming a PU layer comprising an at least partially crosslinked polyurethane; (b) forming a TPU layer comprising a thermoplastic polyurethane; (c) forming a PSA layer comprising a pressure sensitive adhesive; (d) bonding one major surface of the PU layer to one major surface of the TPU layer; and (e) bonding the PSA layer to an opposite major surface of the TPU layer; wherein the TPU layer is sandwiched between the PU layer and the PSA layer, and wherein at least one of steps (a) or (b) comprises step: (i) forming a rolling bank of a polyurethane precursor material, wherein the rolling bank contacts first and second substrates; passing the first and second substrates with the polyurethane precursor material disposed therebetween through a nip; heating the polyurethane precursor material under conditions such that it forms the PU layer or the TPU layer in contact with the first and second substrates; and optionally removing at least one of the first or second substrates from the PU layer or the TPU layer to expose an outer surface of the PU layer or the TPU layer, respectively; or step (b) comprises step: (ii) introducing components into an extruder to provide a molten thermoplastic polyurethane; extruding the molten thermoplastic polyurethane through a die onto a third substrate; passing at least the third substrate and the extruded molten thermoplastic polyurethane through a nip to provide a layer of thermoplastic polyurethane on the third substrate; and solidifying the thermoplastic polyurethane; or step (a) comprises step (i) and step (b) comprises step (ii).