Patent ID: 8147644

Claim:
A method of manufacturing a wide, fused thermoplastic membrane, comprising: drawing a release liner web into a throat between parallel, spaced apart first and second nip rollers of a membrane extruder, the release liner web having first and second sides and first and second opposed edges; simultaneously extruding a molten first thermoplastic and a molten second thermoplastic that are compatible and fusible with each other into the throat of the two rollers, wherein the first thermoplastic is extruded between the first side of the release liner web and the first roller, and wherein the-molten second thermoplastic is extruded into the throat of the two rollers between the second side of the release liner web and the second roller, the resulting first and second thermoplastic membranes being wider than the release liner web and thereby fusing the first thermoplastic and the second thermoplastic proximally to the first and second edges of the release liner web to encapsulate the release liner web and to form a thermoplastic/release liner web composite; and slitting an edge of the resulting thermoplastic/release liner web composite to provide the first thermoplastic membrane coated on the first side of the release liner and the second thermoplastic membrane coated on the second side of the release liner, wherein the first thermoplastic membrane and the second thermoplastic membrane are fused proximally to the second edge of the release liner web.