Patent ID: 8377357

Claim:
A method for manufacturing a thermoplastic synthetic integral foam board having a coarsely porous core, sealed and smoothed side surfaces and at least one sealed and smoothed side edge, said method comprising the steps of: mixing a thermoplastic synthetic material in an extruder; extruding the thermoplastic synthetic material through a wide-slot nozzle to form a flat plastic web having a coarsely porous core; cooling and calibrating the plastic web on a calendar roll pair to form sealed and smoothed side surfaces; drawing off the plastic web; and heating the side edge of the plastic web in a guide groove of a smoothing device to at least a melting temperature of the thermoplastic synthetic material following calibration, while pressing the contact surface of the smoothing device against the side edge to smooth and densify the thermoplastic synthetic material, thereby to smooth and seal the side edge of the coarsely porous core while simultaneously maintaining adjacent peripheral surface areas of the plastic web in the smoothing device at a temperature below the softening temperature of the thermoplastic synthetic material by cooling.