Abstract:
The extrusion of a tire sidewall or tread and sidewall strip with a white sidewall stripe integrally formed therewith is made possible by an improved, modified preform unit for extrasion die. The preform unit has a first passageway for the sidewall or tread-sidewall strip that extends from the entrance side through to the exit side of the unit. The unit is modified to include a second passageway for the white sidewall material that introduces the white material into the stream of the black sidewall material as it passes through the unit. Upstream of the point where the white side material is introduced, the blockage means interrupts the flow of the black material, creating a void in the stream into which the white material can flow.