ULTRAHIGH-MOLECULAR POLYETHYLENE FOAM AND PROCESS FOR PRODUCING THE SAME

摘要

[PROBLEMS] To provide: a skinned foam which has a satisfactory appearance and to which functions such as lightweight properties, heat-insulating properties, sound-absorbing properties, a reduced permittivity, cushioning properties, and flexibility have been imparted without significantly reducing excellent properties inherent in ultrahigh-molecular polyethylene, such as wearing resistance, self-lubricity, impact resistance, low-temperature properties, and chemical resistance; and a process for stably producing the foam. [MEANS FOR SOLVING PROBLEMS] The foam is one which is obtained by foaming ultrahigh-molecular polyethylene having a viscosity-average molecular weight of 300,000 to 10,000,000 and which has a density of 0.02 to 0.7 g/cm3. The foam can be produced by adding, in an extruder, carbon dioxide to the ultrahigh-molecular polyethylene in a molten state and extruding and foaming the melt in such a manner that the resin residence time and pressure in the die part are specific values and that the surface temperature and central-part temperature of the resin immediately after ejection from the die are given values.