Patent ID: 8562885

Claim:
A method of making an annular multilayer structure, comprising: providing a multilayer flow stream of thermoplastic resinous materials, the multilayer flow stream comprising a microlayer portion having at least 30 layers and at least one additional layer on a first and second side of the microlayer portion, the microlayer portion having a microlayer structure; feeding the multilayer flow stream through a tubular flow channel having an inlet and outlet to a single distribution manifold of an annular die, wherein the tubular flow channel has a curved arc section between the inlet and outlet, the curved arc section having a circular channel diameter, wherein the curved arc section has a radius of curvature larger than the circular channel diameter; splitting the multilayer flow stream into at least two flow streams, wherein the at least two flow streams move in opposite directions around a circumference of the distribution manifold to form an annular multilayer flow stream, an end of one of the flow streams overlapping an end of another flow stream in an overlapped area, and wherein the microlayer structure is maintained in the overlapped area; and removing the annular multilayer flow stream from the annular die to form the annular multilayer structure.