Patent ID: 8338563
Filing Date: 2012-12-25
Classification: B29B,B29K,B29L,C08J,Y02P,Y02W

Abstract:
1. A method for purifying a plastic, the method comprising: dissolving the plastic to be purified under pressure in a polar organic solvent to obtain a mixture of a solution of the plastic and insoluble materials; adjusting at least one of density and viscosity of the plastic solution by adding an apolar organic solvent phase separation agent to the plastic solution mixture; introducing the adjusted plastic solution mixture into a centrifugal settler; subjecting the adjusted plastic solution mixture to gravitational and centrifugal force at a pressure above atmospheric pressure in the centrifugal settler such that the insoluble materials move to a periphery of the centrifugal settler, and settle to an outlet orifice at a settlement end of the centrifugal settler and a purified solution of the plastic migrates towards a center of the centrifugal settler and flows in an opposite direction to the settlement direction to an overflow end of the centrifugal settler; controlling a level of the adjusted plastic solution mixture in the centrifugal settler to adjust an overflow rate to an effective degree of separation of the insoluble materials; removing the purified plastic solution from the centrifugal settler by overflow through an overflow orifice; and removing the insoluble materials from the centrifugal settler through the outlet orifice at the settlement end of the centrifugal settler; wherein the centrifugal settler comprises: a housing or bowl having a cylindrical portion and a conical portion, rotating at a speed; a screw concentric with the housing or bowl, rotating in a same direction as the housing or bowl but at a lower speed, and an amount of the apolar organic solvent phase separation agent added is sufficient to reduce at least one of the density and viscosity of the plastic solution and, at the same time, preserve or increase its plastic dissolution capacity.