Process for producing foamed plastic articles

A method of making a molded foamed thermoplastic article from a particulate thermoplastic resin comprising:

• intensively mixing and thermokenetically heating a particulate composition comprising thermoplastic resin particles and a foaming agent, said foaming agent having a trigger temperature at which a gas is evolved therefrom to effect foaming, said mixing and heating being effected by mixing said particulate composition in an enclosed mixing chamber with a plurality of blades attached to arms rotating within said chamber with a blade tip speed of at least about 18 meters per second;
• continuing said mixing of said particulate composition in said enclosed chamber until said particulate composition is heated to a mixing temperature at or above said trigger temperature of said foaming agent, said mixing temperature being sufficient to effect fluxing of said particulate composition to an extent such that the fluxed composition has a viscosity sufficient to contain gas evolved from said foaming agent;
• discharging the fluxed composition from said mixing chamber when the fluxed composition is at said mixing temperature and when said foaming agent is just beginning to foam;
• and
• feeding the discharged fluxed composition to a mold and confining the composition within said mold to mold the composition while foaming of said composition continues, to form a molded foamed plastic article in said mold.