Patent ID: 7767724

Claim:
A method for producing expandable particles of a styrene-modified linear low-density polyethylene-based resin comprising, in the order recited: dispersing 100 parts by weight of non-crosslinked linear low-density polyethylene-based resin particles, 30 to 300 parts by weight of a styrene-based monomer, and 0.1 to 0.9 parts by weight of a polymerization initiator relative to 100 parts by weight of the styrene-based monomer into a suspension containing a dispersant; impregnating the styrene-based monomer into the low-density polyethylene-based resin particles by heating a resultant dispersion at such a temperature that polymerization of the styrene-based monomer does not substantially take place; performing a first polymerization of the styrene-based monomer at a temperature of higher than (T−8) ° C. and lower than (T+1) ° C., T ° C. being a melting point of the low-density polyethylene-based resin particles; adding a styrene-based monomer and 0.1 to 0.9 parts by weight of a polymerization initiator relative to 100 parts by weight of the styrene-based monomer after the first polymerization has reached a conversion ratio of from 80% to 99.9%, and performing an impregnation of the styrene-based monomer into the low-density polyethylene-based resin particles and a second polymerization of the styrene-based monomer at a temperature of higher than (T−15) ° C. and lower than (T+5) ° C., T ° C. being a melting point of the polyethylene-based resin particles; and impregnating a volatile blowing agent during or after the polymerization; a total amount of the styrene monomers used in the first and second polymerizations being more than 300 parts by weight and not more than 1000 parts by weight relative to 100 parts by weight of the low-density polyethylene-based resin particles; whereby resin components of the expandable particles contain a gel component comprising from 2 to 40 wt% of a graft polymer.