APPARATUS FOR PRODUCING SYNTHETIC RESIN FOAMED OBJECT

摘要

PURPOSE:To provide an apparatus capable of always making the injection amt. of a gaseous foaming agent into an extruder constant and capable of stably obtaining a high foaming degree. CONSTITUTION:An injection nozzle 6 is provided to inject a gaseous foaming agent into an extruder 1. The orfice diameters of the injection nozzle are set so that the nozzle inlet and outlet pressure ratio corresponding to the ratio of the pressure on the outlet side of the injection nozzle 6 and that on the inlet side thereof becomes larger than a critical pressure ratio. A flow rate control valve 11 allowing a constant amt. of the gaseous foaming agent to flow to the injection nozzle 6 is provided. A temp. control means 18 controlling the temp. between the flow rate control valve 11 and the injection nozzle 6 is provided to control the pressure on the inlet side of the nozzle so that the gas flow rate in the nozzle becomes constant to the fluctuations of the pressure on the outlet side of the nozzle.