PRE-FOAMING OF THERMOPLASTIC RESIN GRANULE

摘要

PURPOSE:To uniformly expand the granules of a thermoplastic resin preliminarily without causing hot-bonding of the granules by a method in which thermoplastic resin granules containing a volatile blowing agent are dispersed in water in a pressure-resistant container, pressurized and heated under specific conditions, and then discharged to a low-pressure free space from a discharge port leading to the inside of the container. CONSTITUTION:Thermoplastic resin granules 2 containing a volatile blowing agent are dispersed in water in a pressure-resistant container 1 and then heated at a temperature below the softening temperature (of the thermoplastic resin containing the blowing agent) plus 50 deg.C by a heater 4. Furthermore, while keeping the internal pressure of the container at a pressure below the vapor pressure (of the blowing agent) plus 30kg/cm<2> (guage), the mixture inside the container is discharged to a conduit pipe 8 or a container 9 having a free space larger than the flying locus of the expanded granules discharged or a lower free space than the internal pressure of the container from a discharge port provided to an orifice plate 7 after a discharge valve 6 leading to the inside of the container. Thus, objective pre-expanded resin granules 10 can be obtained.