US Patent 8080118 Two-piece container seal and method of manufacture

The present invention provides an improved method of preparing a two-piece container seal. The method comprises contacting a first thermoplastic surface of a moving web of a first flexible sheet material with a second thermoplastic surface of a moving web of a second flexible sheet material, the webs of first and second flexible sheet material moving at substantially the same speed and in the same direction; ultrasonically forming at least one array of spaced, frangible ultrasonic welds between the first and second thermoplastic surfaces, thereby producing a flexible multilayer sheet material having an adhesive-free interface between the first and second thermoplastic surfaces thereof; and cutting a container seal from the multilayer sheet material.