# US 11,993,681 B2 · Method for producing recycled polyethylene with virgin-like optical properties

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- Number: US 11,993,681 B2
- Document ID: US11993681B2
- Status: Granted
- Kind: B2
- Application number: 18/121,677
- 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/US11993681B2

## CPC

- C08J 11/08: using selective solvents for polymer components
- B29B 17/02: Separating plastics from other materials
- B29B 2017/0293: {Dissolving the materials in gases or liquids}
- B29K 2023/06: {PE, i.e. polyethylene}
- B29K 2023/0608: {characterised by its density}
- 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)
- B29B: PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## Abstract

A method for purifying a contaminated reclaimed polyethylene is provided. The method comprises obtaining the contaminated reclaimed polyethylene, extracting it with a solvent to produce an extracted contaminated reclaimed polyethylene, and then dissolving it in the solvent to produce a first suspension comprising dissolved polyethylene and suspended contaminants. The first suspension is settled to produce a second suspension comprising dissolved polyethylene and suspended remaining contaminants, and the second suspension is purified by contacting it with solid media to produce a third suspension comprising purer polyethylene. Finally, the purer polyethylene is separated from the third suspension and it has virgin-like optical properties.

## Claims

### Claim 1

A method for purifying contaminated reclaimed polyethylene (crPE) to produce recycled polyethylene with virgin-like optical properties (vlPE) comprising:
a. Obtaining said crPE; wherein said crPE is selected from the group consisting of post-consumer recycled (PCR) polyethylene, post-industrial recycled (PIR) polyethylene, and combinations thereof;
b. Obtaining an extraction solvent; wherein said extraction solvent and said crPE 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 crPE in said extraction solvent at about 5 wt % concentration;
ii. is a monotonically increasing function of temperature;
iii. exceeds 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 crPE 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 polyethylene (ecrPE) is produced;
d. Dissolving the ecrPE 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 polyethylene (PE) 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 PE 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 PE is produced; and
g. Separating said purer PE from said third suspension; and wherein said purer PE is said vlPE;
wherein said vlPE has an L* greater than about 82, a* greater than about −3, b* lower than about 5, and Y lower than about 40%.

### Claim 2 (depends on 1)

The method of claim 1, wherein said cloud point pressure is about 1,200 psig (82.7 barg) at about 120° C., about 1,650 psig (113.8 barg) at about 140° C., about 1,950 psig (134.4 barg) at about 160° C., and about 2,300 psig (158.6 barg) at about 180° C.

### Claim 3 (depends on 1)

The method of claim 1, wherein said dissolution solvent is n-butane and said extraction solvent is n-pentane.

### Claim 4 (depends on 1)

The method of claim 1, wherein said dissolution solvent is the same as said extraction solvent.

### Claim 5 (depends on 4)

The method of claim 4, wherein said extraction solvent is n-butane.

### Claim 6 (depends on 4)

The method of claim 4, wherein said extraction solvent is n-pentane.

### Claim 7 (depends on 1)

The method of claim 1, wherein said crPE comprises contaminated reclaimed high-density polyethylene (crHDPE).

### Claim 8 (depends on 1)

The method of claim 1, wherein said crPE comprises contaminated reclaimed low-density polyethylene (crLDPE).

### Claim 9 (depends on 1)

The method of claim 1, wherein said crPE comprises contaminated reclaimed linear low-density polyethylene (crLLDPE).

### Claim 10 (depends on 1)

The method of claim 1, wherein said crPE comprises a mixture of crLDPE and crLLDPE.

### Claim 11 (depends on 6)

The method of claim 6, wherein said crPE is crHDPE.

### Claim 12 (depends on 1)

The method of claim 1, wherein said extraction mass concentration is greater than about 2 wt %.

### Claim 13 (depends on 12)

The method of claim 12, wherein said extraction mass concentration is greater than about 5 wt %.

### Claim 14 (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 15 (depends on 14)

The method of claim 14, wherein said inorganic material is selected from the group consisting of silica, alumina, iron oxide, aluminum silicate, amorphous volcanic glass, and mixtures thereof.

### Claim 16 (depends on 15)

The method of claim 15, wherein said inorganic material comprises activated alumina.

### Claim 17 (depends on 14)

The method of claim 14, wherein said carbon-based material is selected from the group consisting of anthracite coal, carbon black, coke, activated carbon, cellulose, and mixtures thereof.

### Claim 18 (depends on 1)

The method of claim 1, wherein said solid media are placed in an axial flow filter.

### Claim 19 (depends on 1)

The method of claim 1, wherein said solid media are placed in a candle filter.

### Claim 20 (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 21 (depends on 2)

The method of claim 2, wherein said extraction solvent is n-pentane; wherein said crPE is crHDPE; wherein said extraction temperature is about 205° C. and said extraction pressure is about 1,900 psig (131 barg); wherein said dissolution temperature is about 140° C. and said dissolution pressure is about 1,900 psig (131 barg); wherein said settling temperature is about 140° C. and said settling pressure is about 1,900 psig (131 barg); wherein said purification temperature is about 140° C. and said purification pressure is about 1,900 psig (131 barg); and wherein said vlPE has L* greater than about 82, a* greater than about −3, b* less than about 5, and Y less than about 40%.