Double bubble process for making strong, thin films

Abstract From the Canadian patent

Polymeric, thin oriented films can be made by use of a combination of a hot blown process and a blown bubble process, i.e. a double bubble process. The resulting film has use in replacing PVC for in store stretch wrap applications. Very low density polyethylene VLDPE, is an , especially preferred material for this process. It may be used as a monolayer, or as one layer of a multilayer structure. In practicing the invention the polymer is extruded and, hot blown and heated to a temperature above its orientation temperature. This heating can be accomplished by the use of a heated liquid reservoir or sock disposed at the lower end of the primary bubble, inside the bubble. The hot blown …