a polymer resin extrusion head includes one or more coaxial annular extrusion modules each including a pair of mating annular members with central frustoconical portions having apexes with an axial dimension greater than the axial dimension of the outer portions of the modules so as to form air spaces around each module including frustoconical air space portions to avoid direct heat transfer between adjacent modules . a spiral channel having one or more convolutions extends from a resin inlet on the periphery of the module and gradually opens into a frustoconical transfer passage leading to an annular extrusion outlet on the inner edge of the module . the spiral channel evenly distributes resin from the inlet to the annular outlet .