Patent ID: 6946090

Claim:
A method of extruding a polymeric foam from an extrudate comprising a polymeric resin and a blowing agent for providing the polymeric resin with a cellular structure upon exiting from an extruder having an annular die with an annular die opening and a choke ring having a choke ring aperture formed by an annular choke ring surface and sized to receive at least a portion of the annular die, the annular die defining a longitudinal axis from which the annular die opening is spaced a first radial distance and the annular choke ring surface is spaced a second radial distance, the method comprising: forming the extrudate by mixing a polymeric resin and a blowing agent; and extruding the extrudate through the annular die opening so that the extrudate leaving the annular die opening contacts the annular choke ring surface within a contact time of 1.0 to 20.0 milliseconds (ms).