| abstract |
A foamed, non-crosslinked resin particle having a bulk density of not greater than 0.045 g/cm3 and an average cell diameter of at least 200 mu m. The non-crosslinked resin includes a polypropylene resin to which a vinyl comonomer is graft-polymerized in such an amount that the weight ratio of the polypropylene resin to the grafted polymer of the vinyl comonomer is in the range of 97:3 to 65:35. The foamed resin particles are produced by grafting a vinyl comonomer to polypropylene resin particles at a temperature of less than 90 DEG C. in the presence of a specific radical polymerization initiator to obtain modified polypropylene resin particles and, then, expanding the modified polypropylene resin particles. The initiator used requires a temperature of not higher than 70 DEG C. for obtaining a half life of 10 hours. |