Patent ID: 7658874

Claim:
A process for the startup of an underwater melt cutter for polymers wherein a molten polymer having a melt temperature above 200° C. has been forced through a die having an exit face and one or more die holes, and upon exiting said die holes said polymer is cut by one or more rotating knives, and wherein said polymer is underwater or in contact with water in the vicinity of the exit face of said die, wherein the improvement comprises: (a) providing a die assembly having a die plate or a die body having one or more die holes, said die holes having a reverse taper, wherein the reverse taper has a taper angle of about 0.5° to about 5°, wherein the polymer in said die in the vicinity of at least a portion of said reverse taper of said die holes is at a temperature below the melting point of said polymer, or if said polymer has no melting point, at a temperature below the glass transition point of said polymer, thereby providing a solid polymer plug wherein the solid polymer plug seals the die plate, while said exit face is in contact with water; (b) rotating said knives; and (c) after (a) and (b) have been accomplished forcing said molten polymer through said die holes no earlier than 5 seconds after said water is in contact with said exit face.