Patent ID: 7815828

Claim:
A method for manufacturing spherical thermoplastic resin expandable granules comprising the steps of: injecting a blowing agent under pressure into a thermoplastic resin which is melted in an extruder; extruding the melted resin containing the blowing agent as an extrudate from a plurality of small holes in a die attached to a distal end of the extruder directly into a coolant liquid, and directly cutting the extrudate by high-speed rotary blades using a hot-cut method; and cooling and solidifying the extrudate by contacting with the coolant liquid, and thereby obtaining the expandable granules wherein the melted resin containing the blowing agent passing through land parts of the small holes of the die is extruded such that a shearing speed is 12,000 to 35,000 sec −1 , and an apparent melt viscosity of the resin is 100 to 700 poise.