| 摘要 |
PURPOSE:To wholly and uniformly expand a thick bridged foam material by using a system in which the temperature of a die is kept at a temperature below the decomposing temperature of a blowing agent used in the former stage but kept at a temperature above the decomposing temperature in the latter stage, a lubricating agent is supplied from near an inlet, and a drawing die is provided at an inlet. CONSTITUTION:A bridgeable thermoplastic resin is uniformly mixed with a cross-linking atent and a blowing agent at a temperature at which the main portions of the cross-linking agent and the blowing agent undergo no decomposition, and the mixture is extruded into long land dies 2 and 3. On the other hand, a lubricating agent is continuously supplied to a slit 2a over the whole periphery of the inlet 4 of the long land dies. A drawing die 5 is provided near the outlet of the long land die 3. A synthetic thermoplastic resin supplied into the die is practically bridged in the former stage 2 of the die under the compressed condition, the blowing agent is decomposed in the latter stage 3 in such a way that no bubbles are formed in the molten resin in the decomposition of the blowing agent, and the resin is extruded from the drawing die 5 under atmospheric pressure or controlled pressures to form a bridged, foamed product having a large thickness and wholly and uniformly expanded cells. |
