| 摘要 |
PURPOSE:To obtain the title extruded foam where the same possesses neither a corrugating phenomenon nor a void phenomenon, a homogeneous cell diameter and characteristic value free from directional properties, by specifying a foaming angle showing an extrusion shearing rate into a low-temperature and low-pressure foaming sphere of specific foamable polyolefin resin and a widthwise expansion rate of extruded resin. CONSTITUTION:Polyolefin resin fed through a hopper 1 and melted by an extruding machine 2 receives supply of a foaming agent through a foaming agent supply port 4, kneaded and transferred by a screw 3, becomes noncrosslinked foamable polyolefin resin, temperature- controlled with a tank 5, led by a duct 10, extruded through an extrusion die 7 and becomes a foam. The foamable polyolefin resin to be melted and extruded into a low-temperature and low-pressure foaming sphere through the die 7 is made into a matter which is kept remaining within a sealed system under a high-temperature and high-pressure for at least 20 minutes during a period of time extending from after contacting of the polyolefin resin of a base material with the foaming agent up to extrusion of them. Extrusion shearing rate at the time of melting and extruding of the foamable polyolefin resin within the low- temperature and low-pressure sphere is made at least 500/sec. Then a foaming angle showing a widthwise expansion rate of expanding extruded resin is made 45 degrees or less by a method wherein foaming of the extruded foamable resin is made into a natural foaming state and an air bubble within the resin is grown. |
