| 摘要 |
PROBLEM TO BE SOLVED: To provide a screw for an extruder, in which in the case of molding a nonhalogen flame resistant extrusion material, even if the number of revolutions of a screw is raised, extrusion temperature is low maintained and while suppressing change of properties due to foaming, a material can be sufficiently kneaded and productivity is enhance and also the properties of an outward appearance are enhanced. SOLUTION: A screw 10 for an extruder consists of three zones of a material feeding zone 20, a plasticizing zone 30 and a metering zone 40. The plasticizing zone 30 is comprised of a double flight and a single flight. The channel bases 51, 52, 53 of the single flight are changed into an uneven shape in the direction of a channel width and channel depth is changed into a wave shape in the longitudinal direction. Furthermore, volume ratio of a flow path of a material for the metering zone 40 of the material feeding zone 20 is made to 0.99-0.5 by setting of both a fundamental screw pitch of each zone and depth a screw channel.
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