Patent ID: 8779019

Claim:
A noncrosslinked polyethylene resin expanded particle (first stage expanded particle) having a bulk density BD in a range of not less than 10 g/L and not more than 100 g/L, the noncrosslinked polyethylene resin expanded particle (first stage expanded particle) being obtained by: (a) first introducing, into a pressure-resistant container, a polyethylene resin particle together with water, a foaming agent, and a dispersing agent, the polyethylene resin particle containing not less than 0.05 part by weight and not more than 2 parts by weight of at least one kind selected from the group consisting of glycerin, polyethylene glycol, and polypropylene glycol with respect to 100 parts by weight of polyethylene resin whose density is in a range of not less than 0.920 g/cm 3 and less than 0.940g/cm 3 , and (b) expanding the polyethylene resin particle by discharging the polyethylene resin particle from the pressure-resistant container into a low-pressure atmosphere after a temperature and a pressure inside the pressure-resistant container are retained at predetermined levels, respectively, the low-pressure atmosphere being set at a temperature in a range of not less than 60° C. and not more than 120° C., the noncrosslinked polyethylene resin expanded particle (first stage expanded particle) having a shrinkage factor in a range of not less than 3% and not more than 30%, the shrinkage factor being obtained by the following formula (1): Shrinkage Factor =(BD − V BD)×100/ V BD (1), wherein: the BD is a bulk density of the noncrosslinked polyethylene resin expanded particle (first stage expanded particle) at 23° C. and at 0.1 MPa (at a normal atmospheric pressure); and the VBD is a bulk density of the noncrosslinked polyethylene resin expanded particle (first stage expanded particle) at 23° C. and at a reduced pressure of 0.002 MPa or less.