Patent ID: 8425818

Claim:
A method of extruding foamed thermoplastic plastic pellets, comprises the steps of: uniformly mixing thermoplastic material and foaming agent; extruding the thermoplastic material mixed with the foaming agent to a high-pressure underwater pelletizing machine; forcing high temperature liquid at a high pressure over a cutter to rotate the cutter, said cutter being rotatable about an axis of rotation parallel to or coincident with a flow path of the forced high temperature liquid over the cutter; cutting extruded thermoplastic material mixed with the foaming agent into thermoplastic pellets by rotation of the cutter; and transporting the thermoplastic pellets out of the high-pressure underwater pelletizing machine using the high-temperature liquid in a direction parallel to the axis of rotation of the cutter, said transporting comprising delivering the thermoplastic pellets to a foaming chamber through a pressure drop device connected thereto and cooling the foamed thermoplastic pellets in the foaming chamber, said foaming chamber being connected to the high-pressure underwater pelletizing machine.