# US 11,993,682 B2 · Method for producing recycled high-density polyethylene with natural-like optical properties > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,993,682 B2 - Document ID: US11993682B2 - Status: Granted - Kind: B2 - Application number: 18/121,706 - Filed: 2023-03-15 - Published: 2023-07-27 - Granted: 2024-05-28 - Earliest claimed: 2020-07-28 - Assignees: The Procter & Gamble Company - Applicants: The Procter & Gamble Company - Inventors: Dimitris Ioannis Collias; Amy Eichstadt Waun; James Carmony; John Moncrief Layman - Web page: https://patentgrep.com/patent/US11993682B2 ## CPC - C08J 11/08: using selective solvents for polymer components - C08J 2323/06: Polyethene - Y02W 30/62: Plastics recycling; Rubber recycling - C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29) - Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT ## Abstract A method for purifying a contaminated reclaimed HDPE is provided. The method comprises obtaining the contaminated reclaimed HDPE, extracting it with a solvent to produce an extracted contaminated reclaimed HDPE, and then dissolving it in the solvent to produce a first suspension comprising dissolved HDPE and suspended contaminants. The first suspension is settled to produce a second suspension comprising dissolved HDPE and suspended remaining contaminants, and the second suspension is purified by contacting it with solid media to produce a third suspension comprising purer HDPE. Finally, the purer HDPE is separated from the third suspension and it has natural-like optical properties. ## Claims ### Claim 1 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 an extraction solvent; wherein said extraction 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 extraction 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 extraction 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 a dissolution 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; wherein at least one of said extraction solvent or said dissolution solvent has a normal boiling point higher than about 70° C.; and wherein said nlHDPE has an L* greater than about 75, a* greater than about −6, b* lower than about 11, and Y lower than about 80%. ### Claim 2 (depends on 1) The method of claim 1, wherein said cloud point pressure is about 100 psig (6.9 barg) at about 140° C., about 383 psig (26.4 barg) at about 160° C., about 770 psig (53.1 barg) at about 180° C., about 1,200 psig (82.7 barg) at about 200° C., and about 1,515 psig (104.5 barg) at about 220° C. ### Claim 3 (depends on 1) The method of claim 1, wherein said extraction solvent is the same as said dissolution solvent. ### Claim 4 (depends on 1) The method of claim 1, wherein said extraction mass concentration is greater than about 2 wt %. ### Claim 5 (depends on 4) The method of claim 4, wherein said extraction mass concentration is greater than about 3 wt %. ### Claim 6 (depends on 5) The method of claim 5, wherein said extraction mass concentration is greater than about 5 wt %. ### Claim 7 (depends on 1) The method of claim 1, wherein said solid media are selected from the group consisting of inorganic material, carbon-based material, and mixtures thereof. ### Claim 8 (depends on 7) The method of claim 7, wherein said inorganic material is selected from the group consisting of silica, alumina, iron oxide, aluminum silicate, amorphous volcanic glass, and mixtures thereof. ### Claim 9 (depends on 8) The method of claim 8, wherein said inorganic material comprises activated alumina. ### Claim 10 (depends on 7) The method of claim 7, wherein said carbon-based material is selected from the group consisting of anthracite coal, carbon black, coke, activated carbon, cellulose, and mixtures thereof. ### Claim 11 (depends on 1) The method of claim 1, wherein said solid media are placed in an axial flow filter. ### Claim 12 (depends on 1) The method of claim 1, wherein said solid media are placed in a candle filter. ### Claim 13 (depends on 1) The method of claim 1, wherein said purification comprises contacting said second suspension with said solid media in a candle filter followed by an axial flow filter; and wherein said solid media of said candle filter comprise diatomaceous earth and said solid media of said axial flow filter comprise activated alumina. ### Claim 14 (depends on 1) The method of claim 1, wherein said extraction temperature is about 230° C. and said extraction pressure is about 600 psig (41.4 barg); wherein said dissolution temperature is about 210° C. and said dissolution pressure is about 1,900 psig (131 barg); wherein said settling temperature is about 210° C. and said settling pressure is about 1,900 psig (131 barg); wherein said purification temperature is about 210° C. and said purification pressure is about 1,900 psig (131 barg); and wherein said nlHDPE has L* greater than about 75, a* greater than about −6, b* less than about 11 and Y less than about 80%. ### Claim 15 A method for purifying crHDPE to produce 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. Extracting said crHDPE with an extraction solvent at an extraction mass concentration of about 3.5 wt %, at an extraction temperature of about 230° C., and at an extraction pressure of about 600 psig (41.4 barg) to produce an extracted contaminated reclaimed HDPE (ecrHDPE); c. Dissolving the ecrHDPE in a dissolution solvent at a mass concentration of about 3.5 wt %, at a dissolution temperature of about 210° C., and at a dissolution pressure of about 1,900 psig (131 barg) to produce a first suspension comprising dissolved HDPE and suspended particulate contaminants; d. Settling said first suspension at about 210° C. and at about 1,900 psig (131 barg) to produce a second suspension comprising dissolved HDPE and suspended remaining particulate contaminants; e. Purifying said second suspension by contacting said second suspension with solid media at about 210° C. and at about 1,900 psig (131 barg) to produce a third suspension comprising purer HDPE; wherein said purification comprises contacting said second suspension with said solid media in a candle filter followed by an axial flow filter; and wherein said solid media of said candle filter comprise diatomaceous earth and said solid media of said axial flow filter comprise activated alumina; and f. Separating said purer HDPE from said third suspension; wherein said purer HDPE is said nlHDPE; wherein at least one of said extraction solvent or said dissolution solvent has a normal boiling point higher than about 70° C.; and wherein said nlHDPE has L* greater than about 75, a* greater than about −6, b* less than about 11, and Y less than about 80%. ### Claim 16 (depends on 15) The method of claim 15, wherein said extraction solvent is the same as said dissolution solvent.