| abstract |
Provided is a method for producing a molding material that contains a cyclic olefin polymer and has a low volatile impurity content. This method for producing a molding material comprises passing a raw material resin that contains a cyclic olefin polymer through an extruder in a molten state to produce a molding material, wherein the method is characterized in that: the extruder is equipped with a cylinder, a screw housed within the cylinder, a resin introduction port for introducing the raw material resin into the cylinder, a resin discharge port for discharging the molten resin from the cylinder, a fluid injection port for injecting carbon dioxide or water into the cylinder between the resin introduction port and the resin discharge port, and a fluid discharge port for removing the fluid in the cylinder by suction downstream of the fluid injection port and between the resin introduction port and the resin discharge port; there are provided a step for injecting 1-6 parts by mass of carbon dioxide or water per 100 parts by mass of raw material resin into the cylinder from the fluid injection port while transporting the molten raw material resin within the cylinder to bring the carbon dioxide or water into contact with the molten raw material resin, and discharging the fluid in the cylinder from the fluid discharge port, thereby removing the volatile compounds in the raw material resin, and a step for cooling and solidifying the molten resin discharged from the resin discharge port; the screw speed during extrusion of the molten resin is 150 rpm or higher; and the oxygen concentration of the gas phase within the cylinder is 5% by volume or less. |