PRODUCTION OF POLYPROPYLENE FOAM

摘要

PURPOSE:To obtain the titled thick-walled foam having a low to high expansion ratio, by extruding polypropylene resin containing a crosslinking agent and foaming agent blended therein while feeing a lubricant into a long land die, thermally decomposing the crosslinking agent in the former stage part, decomposing the foaming agent in the latter stage part and extruding the resin. CONSTITUTION:Polypropylene resin which is ethylene-propylene random copolymer with 2-10wt.% ethylene content and >=5g/10min melt flow rate and <=1.4 melt expansion ratio is homogeneously blended with a crosslinking agent and foaming agent (e.g. azodicarbonamide) and the resultant blend is extruded through a long land die while feeding a lubricant from the vicinity of an inlet to a sliding contact part of die with the molten resin and extruded to thermally decompose the crosslinking agent in the former stage part of the above- mentioned die. A drawing die is provided in the intermediate part of the die to apply a back pressure to the molten resin in the die and the resin is heated at a decomposition temperature of the foaming agent or above in the latter stage part of the die, extruded through the aforementioned die and expanded.