To obtain an extruded sheet foam having a density of 0.075 to 0.018 g/cm3 which can solve drawbacks of conventional propylene-based resin extruded foams using a noncrosslinked propylene-based resin as a substrate resin, and to provide a method which has a wide suitable foaming temp. range and can easily obtain a propylene-based resin extruded sheet foam having excellent properties.
The noncrosslinked propylene-based resin having a melt tension of not less than 7 gf at 230°C and a semicrystallization time of not less than 800 sec at a temp. of crystallization temp. +15°C is provided as a substrate. This substrate and a foaming agent melt-kneaded within an extruder under high temperature and high pressure conditions. Next, the melt-kneaded product is extruded from the extruder through a circular die mounted at the front head of the extruder under low pressure conditions, and is foamed into a tube. The tubular foam is cut open to obtain an extruded sheet foam having a density of 0.075 to 0.018 g/cm3.
KINO TORU
MORITA KAZUHIKO
ITO HITOO
AOKI TAKESHI
