US Patent 11802245 Processes for viscosity breaking of plastics

A process for converting solid plastic waste to hydrocarbon oil includes melting a feed comprising solid plastic waste to produce a liquefied plastic stream and visbreaking the liquefied plastic stream in a visbreaker unit having a visbreaker furnace and a soaker vessel. Visbreaking includes heating the liquefied plastic stream in the visbreaker furnace to produce a heated liquefied plastic stream, maintaining the heated liquefied plastic stream at the reaction temperature in the soaker vessel for a residence time to produce a visbreaker effluent, and injecting a stripping gas into the soaker vessel. The stripping gas includes at least one of steam, nitrogen, helium, argon, or combinations of these. The process includes introducing the stripping gas to the liquefied plastic stream upstream of the visbreaker furnace, the heated liquefied plastic stream downstream of the visbreaker furnace, or both. The visbreaker effluent is separated to produce a liquid hydrocarbon oil.