| 摘要 |
PROBLEM TO BE SOLVED: To control a thickness ratio altering unit of each resin layer of a parison to be discharged from an annular slit of an extrusion head in a short range by extruding one molten resin to a resin supply passage, and sucking molten resin left in other resin supply passage. SOLUTION: In the molding step of a thickness ratio altering unit of a parison to be discharged from an annular slit 18 of a boundary between a rigid part and a soft part, in the molding of the rigid part, a large quantity of a molten hard resin is fed to a second resin supply passage 14 by a plunger 24, and an infinitesimal amount of a molten soft resin is fed to a first resin supply passage 13 by a plunger 20. Then, the plunger 24 starts to suck at a starting position of the altering unit of the parison, and stops at an ending position. The plunger 20 is advanced at the starting position of the altering unit of the parison, passed through the ending position of the altering unit, advanced to molding of the soft part, and a large quantity of the molten soft resin is fed to the passage 13. |
