| 摘要 |
PURPOSE:To make it possible to extrude not only a thick-walled foamed body whose expansion ratio may range from a high expansion ratio to a low expansion ratio but also a foamed body whose cells have a fine diameter and that is high in resiliency, by giving a back pressure to the resin present in the early stage of an elongate land die. CONSTITUTION:A crosslinkable thermoplastic resin, a foaming agent and a crosslinking agent whose thermal decomposition temperature is higher than the plasticating temperature of the resin are extruded into an elongate land die. A lubricant is fed from near the inlet of the elongate land die to a sliding section between the die and the melted resin, and the resin present between the sliding sections of the die and the melted resin, the sliding sections extending from the early stage 8 of the die to the intermediate of the latter stage thereof, is removed so that a back pressure may be given to the resin present in the early stage 8 of the elongate land die. The resin is allowed to be crosslinked at the early stage and then the pressure at the latter stages 10, 11 is reduced to allow the foaming agent to volatilize or the foaming agent is heated to decompose. Then a foamed body is extruded from the die. |
