Method for Producing Recycled High-Density Polyethylene with Natural-Like Optical Properties

A method for purifying contaminated reclaimed high-density polyethylene (crHDPE) to produce recycled HDPE with natural-like optical properties (nlHDPE) comprising:

• a. Obtaining said crHDPE;
• wherein said crHDPE is selected from the group consisting of post-consumer recycled (PCR) HDPE, post-industrial recycled (PIR) HDPE, and combinations thereof;
• b. Obtaining a solvent;
• wherein said solvent and said crHDPE form a one-phase solution at a temperature and at a pressure higher than the cloud point pressure corresponding to said temperature;
• wherein said cloud point pressure:
• i. corresponds to a solution of said crHDPE in said solvent at about 5 wt % concentration;
• ii. is a monotonically increasing function of temperature;
• iii. is lower than the following pressure levels:
• about 700 psig (48.3 barg) at about 120° C., about 1,150 psig (79.3 barg) at about 140° C., about 1,450 psig (100 barg) at about 160° C., and about 1,800 psig (124.1 barg) at about 180° C.;
• iv. includes smooth extrapolations at temperatures lower than about 120° C. and higher than about 180° C.;
• and
• v. includes smooth interpolations at temperatures between about 120° C. and about 180° C.;
• c. Extracting said crHDPE with said solvent at an extraction mass concentration of at least about 1 wt %, at an extraction temperature, and an extraction pressure;
• wherein said extraction temperature is from about 120° C. to about 260° C.;
• wherein said extraction pressure is below the cloud point pressure corresponding to said extraction temperature;
• and wherein an extracted contaminated reclaimed HDPE (ecrHDPE) is produced;
• d. Dissolving the ecrHDPE in said solvent at a dissolution mass concentration of at least about 1 wt %, at a dissolution temperature, and at a dissolution pressure;
• wherein said dissolution temperature is from about 120° C. to about 260° C.;
• wherein said dissolution pressure is above the cloud point pressure corresponding to said dissolution temperature;
• and wherein a first suspension comprising dissolved HDPE and suspended particulate contaminants is produced;
• e. Settling said first suspension at a settling temperature and at a settling pressure;
• wherein said settling temperature is from about 120° C. to about 260° C.;
• wherein said settling pressure is above the cloud point pressure corresponding to said settling temperature;
• and wherein a second suspension comprising dissolved HDPE and suspended remaining particulate contaminants is produced;
• f. Purifying said second suspension at a purification temperature and at a purification pressure by contacting said second suspension with solid media;
• wherein said purification temperature is from about 120° C. to about 260° C.;
• wherein said purification pressure is above the cloud point pressure corresponding to said purification temperature;
• and wherein a third suspension comprising purer HDPE is produced;
• and
• g. Separating said purer HDPE from said third suspension;
• and wherein said purer HDPE is said nlHDPE.