MANUFACTURE OF NON-CROSSLINKED POLYETHYLENE RESIN PREFOAMED BEADS

摘要

PROBLEM TO BE SOLVED: To manufacture non-crosslinked polyethyene resin prefoamed beads having desired properties only using foaming agents which will not cause global environmental pollution. SOLUTION: Non-crosslinked polyethylene resin beads are dispersed in an aqueous medium in a tightly closed vessel, then an inorganic gas contg. nitrogen is introduced into the vessel to make the pressure in the vessel to 0.1-30kg/cm<2> G. Then the content is heated to not lower than the softening temp of the non- crosslinked polyethylene, and by releasing the content to an atmosphere with a lower pressure than the inner pressure of the tightly closed vessel through an orifice to obtain a low multiplicity foamed beads. These prefoamed beads are obtd. by giving foaming ability to the low multiplicity foamed beads and expanding their volume by heating, while the max. valueαmax of circumference stress acting per unit cell membrane thickness is kept not greater than 10 [kg/cm<2> /μm].