Process for producing polyethylene resin particles and foamable polyethylene resin particles

A process for producing foamable polyethylene resin particles which comprises the steps of:

• a. suspending in an aqueous medium polyethylene resin particles having an MI value of 0.3 to 10, a density of less than 0.93 g/cm.sup.3 and a softening point below 85.degree.C;
• b. adding to said aqueous suspension of (a) a cross-linking agent for cross-linking said polyethylene resin particles;
• c. adding to said aqueous suspension of (b) 30 to 100% by weight based on the weight of said particles of a styrene monomer and a catalyst for polymerizing said monomer;
• d. cross-linking said polyethylene resin particles and polymerizing said monomer in the interior of said polyethylene resin particles;
• and
• incorporating, after the polymerization, a blowing agent into the resulting cross-linked polyethylene resin particles which contain a polystyrene resin formed by the polymerization of said styrene monomer at a temperature below the softening point of said polyethylene resin particles, wherein said blowing agent does not substantially reduce the viscosity of the polymerization system, does not dissolve said resin particles or only slightly swells the polyethylene resin particles, said polyethylene resin particles exhibiting excellent foaming ability and blowing agent retention.