Methods for purifying a reclaimed polymer
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-03
- Publication Date
- 2026-08-13
Smart Images
Figure US2026013643_13082026_PF_FP_ABST
Abstract
Description
85572-WO-PCT / DOW 85572 WO1METHODS FOR PURIFYING A RECLAIMED POLYMERCROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application Serial No.63 / 754,170 filed February 5, 2025, the contents of which are incorporated in their entirety herein.TECHNICAL FIELD
[0002] Embodiments of the present disclosure are directed towards methods for purifying a reclaimed polymer and, more specifically, towards solvent based methods for purifying a reclaimed polymer.TECHNICAL BACKGROUND
[0003] There is currently a high and increasing demand for polymers. At the same time, there is increasing pressure to limit the impact polymers have on the environment. Recycling polymeric waste is one way to limit that impact. Generally, polymer recycling can be classed into physical recycling methods (e.g., mechanical and solvent based methods) and chemical recycling methods (e.g., pyrolysis).
[0004] Mechanical polymer recycling methods involve collecting and sorting reclaimed materials into predominately uniform polymer streams that are washed and mechanically transformed (e.g., by crushing, grinding, extruding, and / or melting) into pellets of recycled polymers. However, the pellets are often contaminated with impurities, including organoleptic compounds, coloring agents, gels, heavy metals, plasticizers, and other polymers. Some of these impurities are located on the surface of the polymer pellets and the rest are incorporated into the polymer pellets. Generally, mechanical polymer recycling methods are unable to remove at least the impurities that are incorporated into the pellets. These impurities result in recycled polymers with composition that is distinct from virgin polymers and the processing of the reclaimed polymers results in diminished mechanical properties that limit their reuse.
[0005] Solvent based methods address some of the limitations of mechanical recycling as they can remove some of the impurities that are incorporated into the pellets to produce purer reclaimed polymers with improved physical properties relative to mechanical recycling. The85572-WO-PCT / DOW 85572 WO2potential impurities to be removed are matched to different solvents and solvent-based process operations (e.g., dissolution, crystallization, sedimentation, centrifugation, filtration, adsorption, and extraction) tailored to remove specific impurities. While capable of producing purified polymers with properties approaching those of the virgin material, solvent-based methods entail higher complexity and thus higher costs, relative to mechanical methods.
[0006] Of particular importance in solvent based recycling processes is the selection of solvent. The choice of solvent is not obvious, with different solvents displaying improved ability to process various polymers (e.g., polyethylene and polypropylene) in different unit operations. In general, higher normal boiling point hydrocarbon solvents are more effective at dissolving the polymers, result in lower capital costs due to the lower pressure many unit operations need to operate at, and open up advantaged unit operations (e.g. semi-batch operation, direct solids conveying, and centrifugation) that are not commercially viable or proven for higher pressure applications. Lower normal boiling point solvents, have the advantages of operation at lower temperatures for certain unit operations and may create advantaged processing conditions in the polymer-solvent mixture (e.g., lower viscosity) and lower volatiles in the final reclaimed product.
[0007] Prior attempts to overcome mechanical recycling limitations have utilized a series of unit operations using different solvents in different stages. Such multi-solvent methods may be able to take advantage of the properties of different solvents for different unit operations. Generally, in the first stage, the polymer can be dissolved in a first, higher normal boiling solvent and then insoluble contaminants can be removed through unit operations such as filtration or centrifugation. Then, the first solvent is removed, a second solvent is added, and further contaminants can be removed via a liquid-liquid extraction step. Generally, a liquid-liquid extraction can only occur when the underlying thermodynamics (temperature, pressure, concentration) cause a polymer solution to separate into two phases: a polymer rich phase and a polymer lean phase. The exact set of temperatures and pressures (represented as a curve) that this occurs for a given composition of a polymer-solvent system is commonly known as the cloud point. It should be understood that pressure is a function of temperature, polymer concentration, and solvent choice. Generally, the first hydrocarbon solvent was removed as the first hydrocarbon solvent was believed to shift the cloud point to conditions where the liquid-liquid extraction step becomes impractical (e.g., due to thermal degradation85572-WO-PCT / DOW 85572 WO3of the target polymer). However, the additional solvent removal step further complicates the process and increases capital / operational costs.
[0008] Accordingly, solvent based methods which can leverage the advantages of multiple different solvents without the difficulty of removing one of the solvents are desired.BRIEF SUMMARY
[0009] Embodiments of the present disclosure meet this need by first dissolving a reclaimed polymer in a first hydrocarbon solvent and then removing an insoluble contaminant. Then, a second solvent is added and a liquid-liquid extraction step can be performed, without the need for an expensive and complex solvent removal process. Without being limited by theory, it is believed that the use of a first hydrocarbon solvent having an initial boiling point from 65 °C to 250 °C and a second solvent having a final boiling point of less than 40 °C, can effectively shift the cloud point of the system to sufficiently low temperatures to enable the liquid-liquid extraction to occur at acceptable temperatures and pressures.
[0010] Embodiments of the present disclosure are directed to a method for purifying a reclaimed polyolefin polymer, the method comprising: dissolving the reclaimed polymer with a first hydrocarbon solvent to make a first composition, wherein the first hydrocarbon solvent has an initial boiling point from 65 °C to 250 °C; removing an insoluble contaminant from the first composition; introducing a second solvent to the first composition, thereby forming a second composition, wherein: the second solvent has a final boiling point of less than 40 °C; the first hydrocarbon solvent is from 50 to 95 wt. % of the total weight of solvent in the second composition; and the second solvent is from 5 to 50 wt. % of the total weight of solvent in the second composition; removing a portion of the second solvent, and a soluble contaminant from the second composition; and removing a portion of the first hydrocarbon solvent from the second composition, wherein removing the portion of the second solvent, the portion of the first hydrocarbon solvent, and the soluble contaminant forms a purified reclaimed polymer.
[0011] These and other embodiments are described in more detail in the Detailed Description. It is to be understood that both the foregoing general description and the following detailed description present embodiments of the presently disclosed technology, and are intended to provide an overview or framework for understanding the nature and85572-WO-PCT / DOW 85572 WO4character of the technology as it is claimed. Additionally, the descriptions are meant to be merely illustrative, and are not intended to limit the scope of the claims in any manner.BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:
[0013] FIG. 1 is a flow chart illustrating a method of purifying a reclaimed polymer, in accordance with one or more embodiments of the present disclosure.
[0014] FIG. 2 is a diagram depicting a system for purifying a reclaimed polyolefin polymer, in accordance with one or more embodiments of the present disclosure.
[0015] FIG. 3 graphically depicts a phase diagram of some embodiments of the solvent systems described herein.
[0016] FIG. 4 graphically depicts the phase behavior of some embodiments of the solvent systems described herein.
[0017] Reference will now be made in greater detail to various embodiments, some embodiments of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar process steps.DETAILED DESCRIPTION
[0018] Methods for purifying a reclaimed polymer are disclosed herein. Embodiments of the present disclosure may, in some embodiments, provide improved contaminant removal efficiency from a variety of polymer feeds (including solid feeds) with fewer unit operations (e.g., may not need to remove any / a predominant portion of the first hydrocarbon solvent from a composition prior to addition of a second solvent to the composition).
[0019] As used herein a “vessel”, may refer to one or more pieces of equipment (where more than one piece of equipment is used, the multiple pieces may be arranged in series, in parallel, or a combination thereof) capable of containing a composition.
[0020] As used herein, “a”, “an”, or “a number of’ can refer to one or more of something.
[0021] As used herein, the terms “undissolvable”, “insoluble”, and “undissolved” may be used interchangeably.85572-WO-PCT / DOW 85572 WO5
[0022] As used herein “solvent”, such as “the first hydrocarbon solvent” or “the second solvent”, refers to a single solvent, e.g., pentane, or a combination of solvents, e.g., a mixture of individual compounds such as ISOPAR™-E. In some embodiments, when a mixture of compounds is utilized for one or both of the first hydrocarbon solvent or the second solvent, each of the compounds of the mixture may have a normal boiling point within 50 °C of one another, such as within 45 °C, within 40 °C, within 35 °C, within 30 °C, within 25 °C, within 20 °C, or even within 15 °C of one another.
[0023] The present disclosure refers to the “removal” of various components, (e.g., the first hydrocarbon solvent, the insoluble contaminant, the soluble contaminant, and the second solvent) from a composition. It should be understood that at least a portion of the component (e.g., at least 50 wt. %, at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, at least 95 wt. %, at least 98 wt. %, at least 99 wt. %, at least 99.9 wt. %, or even at least 99.99 wt. % of the component, based on the total amount of the component previously in the composition) may be removed from the composition.
[0024] “Virgin polymer” refers to polymers that can be characterized as “primary (virgin) raw material,” as defined by ISO 18604. The term virgin polymer can include polymers that have never been processed into any form of end-use product. Virgin polymer may also be referred to as various other terms.
[0025] As used herein, the term “reclaimed polymer” is distinct from virgin polymer and refers to a polymer that has been used for a previous purpose and then recovered for recycling and reuse. For instance, “reclaimed polymer” can refer to polymers recovered from “postconsumer material” as defined by ISO 14021, polymers recovered from “pre-consumer material” as defined by ISO 14021, and combinations thereof. The generic term “postconsumer material” includes blends of polymers recovered from materials generated by households or by commercial, industrial, and institutional facilities in their role as end-users of the material, which can no longer be used for its intended purpose. The generic term “postconsumer material” also includes blends of polymers recovered from returns of materials from the distribution chain. The generic term “pre-consumer material” includes blends of polymers recovered from materials diverted from the waste stream during a manufacturing process. The reclaimed polymer may include a polymer or a blend of polymers recovered from post-consumer material, pre-consumer material, or combinations thereof.85572-WO-PCT / DOW 85572 WO6
[0026] The reclaimed polymer can be a homopolymer, a copolymer, or a combination thereof. Examples of reclaimed polymer include polyolefins, such as polyethylene and / or polypropylene, vinyl polymers, such as poly(vinyl chloride), acrylonitrile, butadiene and styrene homopolymer and interpolymers, acrylics, such as poly(methyl methacrylate), fluorocarbon polymer, polyesters, such as poly(ethylene terephthalate) and poly(bisphenol-A carbonate), polyethers, polyamides, such as Nylon 66, polysaccharides, silicones, such as poly(dimethylsiloxane), thermoplastic elastomers, such as ethylene-propylene rubber, among others. In some embodiments, the reclaimed polymer may be a polyolefin. In some embodiments, the reclaimed polymer may comprise, consist of, or consist essentially of polyethylene, polypropylene, or both.
[0027] The reclaimed polymer may include a number of contaminants. The contaminants may be soluble or insoluble in hydrocarbon solvents. Examples of generally insoluble contaminants include cellulose fibers, rubber (e.g., nitrile rubber), fillers (e.g., calcium carbonate), pigments (e.g., titanium dioxide (white), carbon black, cadmium selenium sulfide (red), molybdate orange, and lead chromate (yellow)), dirt and rock, crosslinked polymers, talc. Examples of generally soluble contaminants include organoleptic compounds (e.g., aldehydes, ketones, and esters), dyes and inks, glycerol monostearate, antistatic agents (e.g., polyethylene glycol), slip promoting agents (e.g., erucamide and oleamide), antioxidants (e.g., hindered phenol and phosphite antioxidants) and their degradation products, cling agents (e.g., polyisobutylene), and UV stabilizer (e.g., hindered amines). In some embodiments, insoluble contaminants remain as solid particles, i.e., they do not dissolve and exist in the solid state, when contacted with the solvent(s). Soluble contaminants are partially or completely dissolved in the solvent, i.e., they exist in the liquid state.
[0028] The reclaimed polymer can be collected and processed prior to purification by the methods disclosed herein. For instance, for pre-purification the reclaimed polymer can be shredded, be washed, undergo metals reduction, e.g., removal, be density separated, be dried, and / or be sorted.
[0029] Embodiments of the present disclosure provide that the reclaimed polymer, or a portion thereof, may be dissolvable in a first hydrocarbon solvent. As used herein, the terms “dissolvable”, “soluble”, and “dissolved” indicate the association of the molecules or ions of a solute, e.g., the reclaimed polymer, with the molecules of a solvent, i.e., the act of solvation, that results in an incorporation of the solute in the solvent. The stability of a solute dissolved85572-WO-PCT / DOW 85572 WO7within a solvent depends strongly on the intermolecular interactions between the solute molecules, the solvent molecules, and between each other.
[0030] Referring now to FIG. 1, a method 10 of purifying a reclaimed polymer is disclosed. The method 10 may comprise a dissolving step 11, wherein a reclaimed polymer is dissolved in a first hydrocarbon solvent to make a first composition. Then, first removing step 12, wherein an insoluble contaminant is removed from the first composition. Then introducing step 13, wherein a second solvent is introduced to the first composition. Together, these steps 11-13 may form a second composition. The method 10 may further comprise a second removing step 14, where a portion of the first hydrocarbon solvent, a portion of the second solvent, and a second soluble contaminant are removed from the second composition to make a purified reclaimed polymer. Each of these steps will be described in more detail in the context of purification system 102 depicted in FIG. 2.
[0031] It should be understood that each of the first composition and the second composition refer to a composition that moves along a process and changes composition though the addition or removal of various components. Thus, the first composition and the second composition may each have different compositions as they move through time and / or space. However, the claimed compositions may be present for at least a portion of the time and / or space along which the first composition and the second composition travel. As the first composition and the second composition move along the process, they may be referred to herein by different names. For example, the first composition may be referred to herein, at various times or spaces in the process, as a polymer dissolution vessel composition and a solid / liquid separation vessel composition. Similarly, the second composition may be referred to herein, at various times or spaces in the process, as an extraction vessel composition and a polymer concentration vessel composition.
[0032] Referring now to FIG. 2, in some embodiments, the purification system 102 can include a polymer dissolution vessel 104, a solid / liquid separation vessel 112, an extraction vessel 124, and a polymer concentration vessel 130. In some embodiments, dissolving step 11 may occur in polymer dissolution vessel 104. Removing step 12 may occur in the solid / liquid separation vessel 112. In some embodiments, solid / liquid separation vessel 112 may comprise one or more vessels or one or more processes may be conducted in a single vessel. Introducing step 13 may occur in one of several vessels (e.g., solid / liquid separation vessel 112 or extraction vessel 124), or inbetween vessels, such as in a mixer or pipe junction85572-WO-PCT / DOW 85572 WO8upstream of extraction vessel 124. Removing step 14 may occur in extraction vessel 124, polymer concentration vessel 130, or both. Each of these method steps will now be described in greater detail in the context of specific vessels and unit operations. However, it should be understood that, in some embodiments, the method steps may be performed using alternate unit operations or vessels.
[0033] In some embodiments, a reclaimed polymer input 106 and a first hydrocarbon solvent input 108 may be fluidly connected to the polymer dissolution vessel 104, and may provide reclaimed polymer and first hydrocarbon solvent to the polymer dissolution vessel 104 respectively. The reclaimed polymer may be dissolved in the first hydrocarbon solvent to form the polymer dissolution vessel composition (i.e., the first composition).
[0034] A polymer dissolution vessel 104 may refer to one or more polymer dissolution vessels, such as a series of vessels, vessels in parallel, or a combination thereof. As used herein, the term “vessel” refers to a tank, pipe, separator, decanter, column, heat exchanger, extruder, and / or other fluid processing hardware. The polymer dissolution vessel 104 may include a number of known components (e.g., an agitator and / or a heating coil).
[0035] The reclaimed polymer may comprise any polymer, such as a polyolefin, such as polyethylene and / or polypropylene. In some embodiments, the reclaimed polymer may comprise polyethylene. In some embodiments, the reclaimed polymer may comprise at least 50 wt. %, at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, at least 95 wt. %, or at least 99 wt. %, of polyolefin (e.g., polyethylene and / or polypropylene), on the basis of the total weight of polymer in the reclaimed polymer. In some embodiments, the reclaimed polymer transferred to the polymer dissolution vessel 104 may be a solid (e.g., in a solid state rather than in a liquid state). The solid reclaimed polymer can be crystalline, semi-crystalline, amorphous, or be a physical mixture of polymers containing combinations thereof. Transferring the reclaimed polymer to the polymer dissolution vessel 104 as a solid can reduce costs associated with melting the reclaimed polymer being transferred to the polymer dissolution vessel 104, reduce processing complications associated with melting the reclaimed polymer being transferred to the polymer dissolution vessel 104, and / or aid in the selective dissolution of the transferred reclaimed polymer in the polymer dissolution vessel 104. The solid reclaimed polymer can have various shapes and / or sizes. For example, the solid reclaimed polymer can be shreds, spheres, cylinders, pellets, or combinations thereof,85572-WO-PCT / DOW 85572 WO9among other shapes. The solid reclaimed polymer can have an average dimension from 1 to 200 millimeters (mm).
[0036] The first hydrocarbon solvent may be selected based upon the reclaimed polymer to be dissolved. In other words, different first hydrocarbon solvents can be utilized for different reclaimed polymers. Generally, the first hydrocarbon solvent may have an initial boiling point (e.g., an initial normal boiling point) of from 65 °C to 250 °C, such as from 65 °C to 75 °C, from 75 °C to 85 °C, from 85 °C to 95 °C, from 95 °C to 105 °C, from 105 °C to 120 °C, from 120 °C to 130 °C, from 130 °C to 140 °C, from 140 °C to 150 °C, from 150 °C to 160 °C, from 160 °C to 170 °C, from 170 °C to 180 °C, from 180 °C to 190 °C, from 190 °C to 200 °C, from 200 °C to 210 °C, from 210 °C to 220 °C, from 220 °C to 230 °C, from 230 °C to 240 °C, from 240 °C to 250 °C, or any combination of two or more of these ranges. “Normal boiling point” refers to the boiling temperature at an absolute pressure of exactly 101.325 kPa. “Initial boiling point” refers to the boiling point temperature of the lowest boiling point compounds in the liquid. “Initial normal boiling point” refers to the temperature at which the lowest boiling point portions of the liquid will begin to boil, at an absolute pressure of exactly 101.325 kPa. In some embodiments, the first hydrocarbon solvent may include aliphatic, aromatic or cyclical, saturated or unsaturated hydrocarbons, and a mixture of them. In one or more embodiments, the first hydrocarbon solvent is selected from alkanes (e.g., linear or branched alkanes, e.g., C7 alkanes, C8 alkanes, C9 alkanes, or mixtures thereof), aromatic hydrocarbons, or mixtures thereof. In one or more embodiments, the first hydrocarbon solvent may comprise paraffins, isoparaffins, or both (e.g., at least 50 wt. %, at least 75 wt. %, at least 85 wt. %, at least 90 wt. %, at least 95 wt. %, at least 99 wt. %, or at least 99.99 wt. %). Isoparaffins are branched chain aliphatic hydrocarbons, such as 2, 3, 3 -trimethylheptane. Mixtures of isoparaffins are commercially available under the tradename ISOPAR™, e.g., ISOPAR™ C, ISOPAR™ E(also referred to herein as “IE”), ISOPAR™ G, and ISOPAR™ H, for instance. In one or more embodiments, the reclaimed polymer is polyethylene and the first hydrocarbon solvent comprises an isoparaffinic hydrocarbon, such as a combination of branched alkanes including trimethyl pentane, which is commercially available as ISOPAR™ E (IE).
[0037] The first hydrocarbon solvent may dissolve the reclaimed polymer to form the polymer dissolution vessel composition (e.g., the first composition) (e.g., at least 50 wt. %, at least 75 wt. %, at least 85 wt. %, at least 90 wt. %, at least 95 wt. %, at least 99 wt. %, or85572-WO-PCT / DOW 85572 WO10at least 99.99 wt. % of the reclaimed polymer may be dissolved). The polymer dissolution vessel composition (e.g., the first composition) can include the first hydrocarbon solvent, dissolved reclaimed polymer, insoluble contaminants, and soluble contaminants.
[0038] The first hydrocarbon solvent may be maintained as a liquid within the polymer dissolution vessel 104 (e.g., by utilization of an appropriate temperature and pressure). The reclaimed polymer may be dissolved by the first hydrocarbon solvent at a temperature of from 70 °C to 250 °C, such as, from 70 °C to 80 °C, from 80 °C to 90 °C, from 90 °C to 100 °C, from 100 °C to 110 °C, from 110 °C to 120 °C, from 120 °C to 130 °C, from 130 °C to 140 °C, from 140 °C to 150 °C, from 150 °C to 160 °C, from 160 °C to 170 °C, from 170 °C to 180 °C, from 180 °C to 190 °C, from 190 °C to 200 °C, from 200 °C to 210 °C, from 210 °C to 220 °C, from 220 °C to 230 °C, from 230 °C to 240 °C, and from 240 °C to 250 °C, or any combination of two or more of these ranges. The reclaimed polymer may be dissolved by the first hydrocarbon solvent at a pressure of from 1 bar to 30 bar, such as from 1 bar to 5 bar, from 5 bar to 10 bar, from 10 bar to 15 bar, from 15 bar to 20 bar, from 20 bar to 25 bar, from 25 bar to 30 bar, or any combination of two or more of these ranges.
[0039] The reclaimed polymer may contact the first hydrocarbon solvent, in the polymer dissolution vessel, for different residence times. In some embodiments, the reclaimed polymer can have an average residence time from 0.01 to 3 hours, such as from 0.01 to 0.1 hours, from 0.1 hours to 0.5 hours, from 0.5 hours to 1 hour, from 1 hour to 2 hours, from 2 hours to 3 hours, or any combination of two or more of these ranges, within the polymer dissolution vessel.
[0040] Dissolving the reclaimed polymer in the first hydrocarbon solvent may form the polymer dissolution vessel composition (e.g., the first composition). The polymer dissolution vessel composition (e.g., the first composition) may comprise at least 95 wt. % of the first hydrocarbon solvent, such as from 95 wt. % to 100 wt. %, from 95 wt. % to 96 wt. %, from 96 wt. % to 97 wt. %, from 97 wt. % to 98 wt. %, from 98 wt. % to 99 wt. %, from 99 wt. % to 100 wt. %, or any combination of two or more of these ranges of the first hydrocarbon solvent. Similarly, the polymer dissolution vessel composition may comprise from 1 wt. % to 5 wt. %, such as from 1 wt. % to 2 wt. %, from 2 wt. % to 3 wt. %, from 3 wt. % to 4 wt. %, from 4 wt. % to 5 wt. %, or any combination of two or more of these ranges of the reclaimed polymer. In some embodiments, the polymer dissolution vessel composition may comprise at least 95 wt. %, at least 97 wt. %, at least 99 wt. %, at least 99.9 wt. %, or even85572-WO-PCT / DOW 85572 WO11at least 99.99 wt. % of the combined weight of the first hydrocarbon solvent and the reclaimed polymer.
[0041] The polymer dissolution vessel composition may be a solution, a suspension, or a melt.
[0042] The system 102 may include a solid / liquid separation vessel 112, fluidly connected to polymer dissolution vessel 104 by output 110. Output 110 can be utilized to transfer the polymer dissolution vessel composition to a solid / liquid separation vessel 112, wherein it may be referred to as a solid / liquid separation vessel composition (e.g., the first composition when it is in the solid / liquid separation vessels). The method may comprise removing an insoluble contaminant from the solid / liquid separation vessel composition. In some embodiments, the insoluble contaminant may be removed from the solid / liquid separation vessel composition in the solid / liquid separation vessel 112. Once separated, the insoluble contaminant may be passed out of output 114, which may include some inadvertent solvent removal. The solid / liquid separation vessel composition in the solid / liquid separation vessel 112 may be in a liquid phase, such as a solution, suspension, or a molten state. In some embodiments not depicted in the figures, the solid / liquid separation vessel 112 can include multiple vessels, such as a filtration vessel and a sorptive separation vessel.
[0043] Referring again to FIG. 2, the solid / liquid separation vessel 112 may include various filter media such as cloth, wool, linen, glass fiber, steel mesh, sintered metal, and combinations thereof. The solid / liquid separation vessel 112 may include a solid bowl centrifuge, a self-cleaning strainer, a drum filter, a candle filter, a leaf filter, and / or rotary pressure filter, among others. One or more embodiments provide that the solid / liquid separation vessel 112 may include one or more filters, such as a plurality of filters configured in a sequence. The plurality of filters can be configured to successively filter a solid / liquid separation vessel composition. The plurality of filters can be configured to remove the first insoluble contaminant. For instance, the plurality of filters can include a first filter and a second filter that is downstream from the first filter. In such instances, the first filter can have a first size rating and the second filter can have a second size rating that is different (e.g., smaller) than the first size rating. The first filter may be maintained in a different (e.g., lower) temperature range than a temperature range associated with the second filter. Employing the plurality of filters with different (e.g., successively smaller) size ratings and / or different (e.g.,85572-WO-PCT / DOW 85572 WO12successively higher temperatures) temperatures may assist in removing the first insoluble contaminant from the solid / liquid separation vessel composition.
[0044] The first composition may have an average residence time from 0.01 to 12 hours, such as from 0.01 to 0.1 hours, from 0.1 hours to 0.5 hours, from 0.5 hours to 1 hour, from 1 hour to 2 hours, from 2 hours to 4 hours, from 4 hours to 6 hours, from 6 hours to 8 hours, from 8 hours to 10 hours, from 10 hours to 12 hours, or any combination of two or more of these ranges, within the solid / liquid separation vessel 112.
[0045] The solid / liquid separation vessel 112may have an operating temperature from 70 °C to 250 °C and an operating pressure from 1 bar to 30 bar, such as from 70 °C to 250 °C, such as from 70 °C to 80 °C, from 80 °C to 90 °C, from 90 °C to 100 °C, from 100 °C to 110 °C, from 110 °C to 120 °C, from 120 °C to 130 °C, from 130 °C to 140 °C, from 140 °C to 150 °C, from 150 °C to 160 °C, from 160 °C to 170 °C, from 170 °C to 180 °C, from 180 °C to 190 °C, from 190 °C to 200 °C, from 200 °C to 210 °C, from 210 °C to 220 °C, from 220 °C to 230 °C, from 230 °C to 240 °C, from 240 °C to 250 °C, or any combination of two or more of these ranges, and / or an operating pressure of from 1 bar to 30 bar, such as from 1 bar to 5 bar, from 5 bar to 10 bar, from 10 bar to 15 bar, from 15 bar to 20 bar, from 20 bar to 25 bar, from 25 bar to 30 bar, or any combination of two or more of these ranges.
[0046] A filtration aid may be present in the filter vessel. The filtration aid may serve to improve removal of contaminants, such as soluble or insoluble contaminants. The filtration aid may comprise solid filtration aids, such as solid particles. In one embodiment, the solid filtration aids may be selected from the group consisting of inorganic material, carbon-based material, and mixtures thereof. Non-limiting examples of inorganic materials are silica (silicon oxide), alumina (aluminum oxide), activated alumina (activated aluminum oxide), iron oxide, aluminum silicate, magnesium silicate, amorphous volcanic glass, reclaimed glass, silica gel, diatomaceous earth, sand, quartz, perlite, fuller's earth, bentonite, and mixtures thereof. In another embodiment, the inorganic material is selected from the group consisting of silica, alumina, iron oxide, aluminum silicate, amorphous volcanic glass, and mixtures thereof. In yet another embodiment, the inorganic material comprises diatomaceous earth. In even yet another embodiment, the inorganic material comprises activated alumina. In one embodiment, the inorganic material comprises reclaimed glass. Non-limiting examples of carbon-based materials are anthracite coal, carbon black, coke, activated carbon, cellulose, and mixtures thereof. In one embodiment, the carbon-based material is selected from the85572-WO-PCT / DOW 85572 WO13group consisting of anthracite coal, carbon black, coke, activated carbon, cellulose, and mixtures thereof. In another embodiment, the carbon-based material comprises activated carbon.
[0047] The method may further comprise removing a soluble contaminant from the solid / liquid separation vessel composition. In embodiments, the soluble contaminant may be removed from the solid / liquid separation vessel composition by contacting the composition with solid media, which may remove a contaminant (e.g., a first soluble contaminant) by adsorption, absorption, electrostatics, size exclusion, ion exclusion, ion exchange, and / or the like. The solid media may be an inorganic material, a carbon-based material, and combinations thereof. Examples of the solid media include zeolite, activated carbon, activated alumina, silica gel, diatomite, perlite, clay, sand, molecular sieve, glass fiber, cellulose material, and combinations thereof. The solid media may be fluidized, agitated, moved en masse, or maintained in a stationary position within the solid / liquid separation vessel 112. In some embodiments not depicted in the figures, the sorptive separation may occur in a separate vessel from the filtration, or in the same vessel (e.g., by the inclusion of the sorptive media in the solid / liquid separation vessel 112).
[0048] The solid / liquid separation vessel composition may contact the solid media for an average residence time from 0.01 to 12 hours, such as from 0.01 to 0.1 hours, from 0.1 hours to 0.5 hours, from 0.5 hours to 1 hour, from 1 hour to 2 hours, from 2 hours to 4 hours, from 4 hours to 6 hours, from 6 hours to 8 hours, from 8 hours to 10 hours, from 10 hours to 12 hours, or any combination of two or more of these ranges. The solid / liquid separation vessel composition may contact the solid media at an operating temperature from 70 °C to 180 °C, such as from 70 °C to 80 °C, from 80 °C 90 °C, from 90 °C to 100 °C, from 100 °C to 120 °C, from 120 °C to 140 °C, from 140 °C to 160 °C, from 160 °C to 170 °C, from 170 °C to 180 °C, or any combination of two or more of these ranges and / or an operating pressure from 1 bar to 30 bar, such as from 1 bar to 5 bar, from 5 bar to 10 bar, from 10 bar to 15 bar, from 15 bar to 20 bar, from 20 bar to 25 bar, from 25 bar to 30 bar, or any combination of two or more of these ranges.
[0049] Output 116 can be utilized to transfer the solid / liquid separation vessel composition (e.g., the first composition) to the extraction vessel 124. The first composition may be in a liquid phase, such as a solution or a molten state, as it is passed to the extraction vessel 124.85572-WO-PCT / DOW 85572 WO14
[0050] According to some of embodiments, the methods and systems may retain all, of or a predominant portion of, the first hydrocarbon solvent in the solid / liquid separation vessel composition (e.g., the first composition) transferred to the extraction vessel 124. In some embodiments, no step of removing the first hydrocarbon solvent is utilized before transferring the first composition to the extraction vessel 124. The solid / liquid separation vessel composition, including all or a predominant portion of the first hydrocarbon solvent, may be transferred directly to the extraction vessel 124 in the absence of intervening vessels (e.g., in the absence of a polymer concentration vessel). Similarly, in some embodiments, no step of removing the first hydrocarbon solvent is utilized before introducing the second solvent to the first composition. As a result, approaches herein may yield reduced capital equipment costs, reduced energy consumption, and other benefits as compared prior approaches that remove the first hydrocarbon solvent prior transferring a composition to an extraction vessel and / or prior to addition of a second solvent.
[0051] A second solvent may be introduced to the first composition, and thereby a second composition may be formed. Referring again to FIG. 2, the second solvent may be transferred to the extraction vessel 124, (e.g., by input 129) and introduced to the solid / liquid separation vessel composition to form the extraction vessel composition (e.g., the second composition). In some embodiments not depicted in the figures, the second solvent may be introduced to the first composition upstream of the extraction vessel 124 and passed to the extraction vessel 124 with the rest of the first composition. For example, the second solvent maybe introduced to the first composition between the solid / liquid separation vessel 112 and the extraction vessel 124, or in the extraction vessel 124, or a combination of these.
[0052] In the extraction vessel 124, a liquid-liquid extraction may be performed. Generally, a liquid-liquid extraction refers to a process whereby one or more compounds are separated based on their solubility in two different liquids. In some embodiments, the two liquids form separate phases and the one or more compounds may move from one liquid to the other liquid based on relative solubility of the compounds in the different liquids. In some embodiments, a single phase may initially be present, then, due to the application of the second solvent and / or the manipulation of conditions, such as temperature and pressure, the single phase may separate into two phases (i.e., a lighter polymer lean phase and a heavier polymer rich phase). This set of conditions is determined by the cloud point.85572-WO-PCT / DOW 85572 WO15
[0053] The extraction vessel 124 itself may be made of various materials and have differing shapes and / or sizes for various applications. The extraction vessel 124 may include a number of known components, such as a separator, decanter, or extraction column.
[0054] The second solvent is different from the first hydrocarbon solvent. The second solvent may be selected based upon an ability to carry soluble contaminants in the polymer lean phase of the extraction step and for the ability to favorably modify the cloud point of the resulting solution. In other words, different second solvents can be utilized in different amounts for different reclaimed polymers, different contaminants, and different first hydrocarbon solvents. The second solvent may have a final boiling point (e.g., final normal boiling point) of less than 40 °C, such as less than 38 °C, less than 36 °C, less than 34 °C, less than 32 °C, less than 30 °C, less than 25 °C, less than 20 °C, less than 15 °C, less than 10 °C, less than 5 °C, less than 0 °C, less than - 20 °C, less than -40 °C, less than -60 °C, or even less than -75 °C. “Final normal boiling point” refers to the boiling point temperature of the highest boiling point compounds in a liquid at an absolute pressure of 101.325 Kpa. The second solvent may have an initial boiling point of greater than -100 °C. Examples of the second solvent may include carbon dioxide (CO2), or alkanes, such as a C1-C5 alkane, such as alkanes comprising 1, 2, 3, 4, or 5 carbon atoms, or a mixture of these. In one or more embodiments, the reclaimed polymer input 106 may comprise polyethylene and the second solvent may be CO2 or pentane.
[0055] The composition transferred to the extraction vessel 124 may form the extraction vessel composition (e.g., the second composition). The extraction vessel composition may comprise at least the first hydrocarbon solvent, the second solvent, and the reclaimed polymer.
[0056] In some embodiments, the extraction vessel composition (e.g., the second composition) may comprise from 50 wt. % to 95 wt. % of the first hydrocarbon solvent and from 5 wt. % to 50 wt. % of the second solvent, on the basis of the total weight of solvent in the extraction vessel composition, before any constituents have been removed. For example, the extraction vessel composition may comprise from 50 wt. % to 55 wt. %, from 55 wt. % to 60 wt. %, from 60 wt. % to 65 wt. %, from 65 wt. % to 70 wt. %, from 70 wt. % to 75 wt. %, from 75 wt. % to 80 wt. %, from 80 wt. % to 85 wt. %, from 85 wt. % to 90 wt. %, from 90 wt. % to 95 wt. %, or any combination of two or more of these ranges of the first hydrocarbon solvent, on the basis of the total weight of solvent in the extraction vessel85572-WO-PCT / DOW 85572 WO16composition. Likewise, the extraction vessel composition may comprise from 5 wt. % to 10 wt. %, from 10 wt. % to 15 wt. %, from 15 wt. % to 20 wt. %, from 20 wt. % to 25 wt. %, from 25 wt. % to 30 wt. %, from 30 wt. % to 35 wt. %, from 35 wt. % to 40 wt. %, from 40 wt. % to 45 wt. %, from 45 wt. % to 50 wt. %, or any combination of two or more of these ranges of the second solvent, on the basis of the total weight of solvent in the extraction vessel composition. It should be understood that the concentration of each of the first hydrocarbon solvent and the second solvent are important factors in determining the cloud point of the solution, which in turn, determines the operating conditions required for the liquid-liquid extraction.
[0057] In some embodiments, at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, at least 95 wt. %, or even at least 99 wt. % of the first hydrocarbon solvent transferred to the polymer dissolution vessel 104 may be present in the extraction vessel composition (e.g., the second composition).
[0058] In one or more embodiments, the extraction vessel 124 may utilize conditions, e.g., temperature and pressure, such that a conventional liquid-liquid extraction is performed. The exact operating pressure and temperature can depend on a choice of the solvent, solvent concentration, and concentration of the reclaimed polymer. In embodiments, the liquid-liquid extraction (e.g., in the extraction vessel 124) may occur operating temperature from 90 °C to 250 °C, such as from 90 °C to 110 °C, from 110 °C to 130 °C, from 130 °C to 150 °C, from 150 °C to 170 °C, from 170 °C to 190 °C, from 190 °C to 210 °C, from 210 °C to 230 °C, from 230 °C to 250 °C, from 250 °C to 270 °C, or any combination of two or more of these ranges and a pressure from 30 bar to 300 bar, such as from 30 bar to 50 bar, from 50 bar to 75 bar, from 75 bar to 100 bar, from 100 bar to 125 bar, from 125 bar to 150 bar, from 150 bar to 200 bar, from 200 bar to 250 bar, from 250 bar to 300 bar, or any combination of two or more of these ranges.
[0059] The extraction vessel composition may have an average residence time from 0.01 to 3 hours within the extraction vessel, such as from 0.01 to 0.1 hours, from 0.1 hours to 0.5 hours, from 0.5 hours to 1 hour, from 1 hour to 2 hours, from 2 hours to 3 hours, or any combination of two or more of these ranges.
[0060] In some embodiments where two liquid phases are formed in the extraction vessel composition, a first polymer rich liquid phase may comprise from 5 wt. % to 60 wt. %, such as from 5 wt. % to 10 wt. %, from 10 wt. % to 20 wt. %, from 20 wt. % to 30 wt. %, from 3085572-WO-PCT / DOW 85572 WO17wt. % to 40 wt. %, from 40 wt. % to 50 wt. %, from 50 wt. % to 60 wt. %, or any combination of two or more of these ranges of reclaimed polymer, on the basis of the total weight of the polymer rich phase. The second polymer lean liquid phase may comprise less than 15 wt. %, such as less than 10 wt. %, less than 5 wt. %, less than 2 wt. %, or even less than 1 wt. % of reclaimed polymer, on the basis of the total weight of the second liquid phase.
[0061] The reclaimed polymer may include polyethylene and polypropylene. In such embodiments, the extraction vessel composition, as described herein, may comprise a first liquid phase including a predominant fraction (e.g., at least 50 wt. %, at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, or at least 95 wt. %) of the polyethylene and a second liquid phase including a predominant fraction (e.g., at least 50 wt. %, at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, or at least 95 wt. %) of the polypropylene.
[0062] In the liquid-liquid extraction, a soluble contaminant may concentrate in one of the two phases, such as a light or upper phase (e.g., the second liquid phase). Then, the method may comprise removing a portion of the second solvent and a soluble contaminant. For example, still referring to FIG. 2, a portion of the extraction vessel contents (e.g., the light or second liquid phase) may be removed from the extraction vessel 124 (e.g., by output 126). The portion of the extraction vessel contents removed by output 126 can include a portion of the second solvent and a soluble contaminant. Such a separation may be by a physical process, such as by decanting a lighter phase (e.g., the second liquid phase). Generally, such removal may include a larger proportion of the second solvent (a lighter solvent) than the first hydrocarbon solvent (a heavier solvent).
[0063] When a portion of the extraction vessel contents is removed from the extraction vessel 124, the portion may be from 15 wt. % to 90 wt. % of the total material, such as from 15 wt. % to 25 wt. %, from 25 wt. % to 35 wt. %, from 35 wt. % to 45 wt. %, from 45 wt. % to 55 wt. %, from 55 wt. % to 65 wt. %, from 65 wt. % to 75 wt. %, from 75 wt. % to 85 wt. %, from 85 wt. %, to 90 wt. %, or any combination of two or more of these ranges, of the total material in the extraction vessel. Where a portion of the second solvent and the soluble is removed, at least 50 wt. %, at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, at least 95 wt. %, or even at least 99 wt. % of the second (lighter) liquid phase may be removed, and at least 50 wt. %, at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at85572-WO-PCT / DOW 85572 WO18least 90 wt. %, at least 95 wt. %, or even at least 99 wt. % of the first (heavier) liquid phase may remain in the extraction vessel.
[0064] In some embodiments, when a portion of the second solvent and soluble contaminant is removed from the second composition (e.g., removed from the extraction vessel 124 by output 126) less than 20 wt. % of the reclaimed polymer may be removed from the second composition. For example, less than 15 wt. %, less than 10 wt. %, or even less than 5 wt. %, or even less than 1 wt. % of the reclaimed polymer may be removed from the second composition.
[0065] In some embodiments, when a portion of the second solvent and soluble contaminant is removed from the second composition (e.g., removed from the extraction vessel 124 by output 126) at least 50 wt. % (e.g., at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, or even at least 99 wt. %) of the second solvent may be removed from the second composition.
[0066] As mentioned, a soluble contaminant can be separated during the liquid-liquid extraction and subsequently removed from the second composition. The soluble contaminant may include non-volatile contaminants. Examples of the soluble contaminants include organoleptics, antioxidants, plasticizers, anti-block agents, antistatic agents, cling agents, ink components, and combinations thereof. Various amounts of the soluble contaminant can be removed from the second composition for different applications.
[0067] The first hydrocarbon solvent, and optionally additional soluble contaminants, may be removed from the second composition to form the purified, reclaimed polymer in a polymer concentration vessel. Still referring to FIG. 2, a remaining portion (e.g., the first or heavier liquid phase) of the extraction vessel composition (e.g., the second composition) can be transferred to a polymer concentration vessel 130 by output 128 in order to remove a further portion of the remaining solvents and / or remaining soluble contaminants and leave behind the purified reclaimed polymer. The polymer concentration vessel 130 may include a number of known components, e.g., a throttling valve, heaters, separators, devolatilization extruder, or gas purge. While a single polymer concentration vessel 130 is illustrated, embodiments are not so limited. For instance, the polymer concentration vessel 130 may comprise one or more flash vessels, e.g., a series of flash vessels, flash separators or flash drums.85572-WO-PCT / DOW 85572 WO19
[0068] The remaining portion of the second composition, which may be in a fluid phase, that is transferred to the polymer concentration vessel 130 can undergo a reduction in pressure, e.g., by passing through one or more throttling valves or other throttling devices. One or more embodiments provide that the polymer concentration vessel 130 may utilize a series of reduced pressures, e.g., where a particular reduced pressure is lower relative to a preceding reduced pressure, to remove (e.g., a portion) of the first hydrocarbon solvent, the second solvent, and / or soluble contaminants to make the purified reclaimed polymer. The solvent and / or contaminants can be removed from polymer concentration vessel 130 by output 132.
[0069] In some embodiments, the first hydrocarbon solvent, and optionally additional soluble contaminants, may be removed from the second composition to form the purified, reclaimed polymer at a temperature from 130 °C to 300 °C, such as from 130 °C to 150 °C, from 150 °C to 175 °C, from 175 °C to 200 °C, from 200 °C to 225 °C, from 225 °C to 250 °C, from 250 °C to 275 °C, from 275 °C to 300 °C, or any combination of two or more of these ranges and / or a pressure from 0.02 bar to 50 bar, such as from 0.02 bar to 0.1 bar, from 0.1 bar to 0.5 bar, from 0.5 bar to 1 bar, from 1 bar to 5 bar, from 5 bar to 10 bar, from 10 bar to 20 bar, from 20 bar to 30 bar, from 30 bar to 40 bar, from 40 bar to 50 bar, or any combination of two or more of these ranges.
[0070] One or more embodiments provide that from 75 to 99.9999 wt. % of all solvent, e.g., the first hydrocarbon solvent and the second solvent, fed to the system 102 can be separated from the purified reclaimed polymer. For example, 75 to 85 wt. %, 85 to 95 wt. %, 95 to 97 wt. %, 97 to 99 wt. %, 99 to 99.9 wt. %, 99.9 to 99.99 wt. %, 99.99 to 99.999 wt. %, 99.999 to 99.9999 wt. %, or any combination of two or more of these ranges, of the solvent may be separated from the purified reclaimed polymer
[0071] The purified reclaimed polymer can be removed from the polymer concentration vessel 130 by output 134. After being removed from the polymer concentration vessel 130, the purified reclaimed polymer may undergo a number of further processing steps, such as pelletization.
[0072] The purified reclaimed polymer can have a number of properties that are desirable for various applications. For instance, the purified reclaimed polymer can provide low residual solvent, low odor, low gels, desirable color, and / or good mechanical properties, while exhibiting a reduction in regulated contaminants.85572-WO-PCT / DOW 85572 WO20
[0073] In some embodiments, the purified reclaimed polymer may comprise less than 25 wt. % (e.g., less than 20 wt. %, less than 15 wt. %, less than 10 wt. %, less than 5 wt. %, less than 4 wt. %, less than 3 wt. %, less than 2 wt. %, less than 1 wt. %, less than 0.5 wt. %, less than 0.1 wt. %, less than 0.05 wt. %, or even less than 0.01 wt. %) of insoluble contaminants, less than 25 wt. % (e.g., less than 20 wt. %, less than 15 wt. %, less than 10 wt. %, less than 5 wt. %, less than 4 wt. %, less than 3 wt. %, less than 2 wt. %, less than 1 wt. %, less than 0.5 wt. %, less than 0.1 wt. %, less than 0.05 wt. %, or even less than 0.01 wt. %) of soluble contaminants, less than 1 wt. % (e.g., less than 0.5 wt. %, less than 0.1 wt. %, less than 0.05 wt. %, or less than 0.01 wt. %) of the first hydrocarbon solvent, and / or less than 1 wt. % (e.g., less than 0.5 wt. %, less than 0.1 wt. %, less than 0.05 wt. %, or less than 0.01 wt. %) of the second solvent on the basis of the total weight of the purified reclaimed polymer.
[0074] In one or more embodiments not depicted in the figures, the first hydrocarbon solvent and / or the second solvent can be purified and separated from one another in separate process steps and recycled to the dissolution and / or extraction vessels, thus reducing the amount of fresh solvent, e.g., fresh first hydrocarbon solvent and / or fresh second solvent, utilized for the method discussed herein. For instance, embodiments herein provide that a removed target portion of the first hydrocarbon solvent can be separated from removed target portion of the second solvent, the removed target portion of the first hydrocarbon solvent can subsequently be transferred via a first recycle stream to the polymer dissolution vessel to form at least a portion of the first hydrocarbon solvent transferred to the polymer dissolution vessel and / or the removed target portion of the second solvent can be mixed with the polymer dissolution vessel composition to form at least a portion of the second solvent that makes up the extraction vessel composition.EXAMPLES
[0075] The described embodiments will be further clarified by the following examples and comparative examples. The below examples illustrate the properties required by solvent systems in the extraction vessel composition.
[0076] The below examples use ISOPAR™-E, a synthetic isoparaffinic hydrocarbon solvent having an initial normal boiling point of 111 °C, a final normal boiling point of 143 °C, and an aromatic content of less than or equal to 0.01 wt. %. ISOPAR™-E is commercially available from ExxonMobil Chemical Co.85572-WO-PCT / DOW 85572 WO21
[0077] Table 1 provides solvent compositions and distribution coefficients for various contaminants in those solvent systems, at the operating temperatures and pressures given in the table. It should be noted that pressure is merely a function of temperature, polymer concentration, and solvent choice. The values presented were obtained from the state-of-art equation of state named Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT). Model parameters were obtained from experimental data and phase boundaries can be calculated. The polymers used in the model involve DOWLEX™ 2020 (commercially available from Dow Chemical) and FT200WV (Commercially available from Braskem), represented by 10 pseudo-components (Prasanna K. Jog, Walter G. Chapman, Sumnesh K. Gupta, and Robert D. Swindoll Industrial & Engineering Chemistry Research 200241 (5), 887-891 DOI: 10.1021 / ie000604b) that resemble the number and weight average molecular weights of the said polymers. The ISOPAR™-E is modeled as 2, 3, 3 -trimethylpentane. The distribution coefficients for impurities are calculated from the ratios of weight fractions of impurities between the two liquid phases in the two-phase region. FIG. 3 shows a phase diagram illustrating the behavior of different polyethylene-solvent systems, including Comparative Example A (CE A) and Examples 2 (EX 2), 3 (EX 3), and 4 (EX 4) alongside the operating temperature and pressure an extraction step would need to operate at for such a system (also referred to as the cloud point). FIG. 4 shows an experimental validation of the phase behavior of some of the mixed solvent systems described herein. CE A, EX 2, EX 3, and EX 4 all comprise 10 wt. % polyethylene and 90 wt. % solvents, on the basis of the total weight of the composition.Table 185572-WO-PCT / DOW 85572 WO22
[0078] CE ANO wt. % PE in solvent (99 wt. % ISOPAR™-E + 1 wt. % Propane, on the basis of the total amount of solvent). The cloud point curve of the solvent in the CE A is very similar to that of ISOPAR™-E only (as is shown in FIG. 3). Thus, the extraction operating temperature remains at prohibitively high temperatures (e.g., greater than 250 °C) despite reasonable distribution coefficients.
[0079] EX 2: 10 wt. % PE in solvent (67 wt. % ISOPAR™-E + 33 wt. % Propane, on the basis of the total amount of solvent). As depicted in FIG. 3, EX 2 shows substantial cloud point modification vs ISOPAR™-E, such that it can mimic the operation of pentane (a more conventional second solvent). The cloud point of EX 2 is low enough to enable extraction at reasonable temperatures (e.g., less than 250 °C), pressures (e.g., low enough to prevent the use of more expensive components, such as flanges), and predicted distribution coefficients.
[0080] EX 3: 10 wt. % PE in solvent (77 wt. % ISOPAR™-E + 23 wt. % CO2, on the basis of the total amount of solvent). As depicted in FIG. 3, EX 3 shows substantial cloud point modifications vs ISOPAR™-E, such that it can mimic the operation of pentane (a more conventional second solvent). The cloud point of EX 3 is low enough to enable extraction at reasonable temperatures, pressures, and predicted distribution coefficients. We note that the pressures used as the operating point in EX 3 is higher than in the other examples to avoid the CO2 gassing out of the ISOPAR™-E liquid.
[0081] EX 4: 10 wt. % PE in solvent (37.7 wt. % ISOPAR™-E + 33.3 wt. % n-Hexane + 29 wt. % Propane, on the basis of the total amount of solvent). As depicted in FIG. 3, EX 4 shows substantial cloud point modification vs ISOPAR™-E, such that it can mimic the operation of pentane (a more conventional second solvent). The cloud point of EX 4 low enough to enable extraction at reasonable temperatures, pressures, and predicted distribution coefficients.
[0082] Table 2 provides a further CE-B and EX-5, which comprise 10 wt. % of polypropylene and 90 wt. % solvents, on the basis of the total weight of the composition.Table 285572-WO-PCT / DOW 85572 WO23
[0083] CE-B: 10% PP in solvent (99 wt. % ISOPAR™-E + 1 wt. % Propane, on the basis of the total amount of solvent). As with CE-A, the cloud point has not been sufficiently reduced in temperature such that the required extraction operating temperature remains at prohibitively high temperatures (320 °C) despite reasonable distribution coefficients.
[0084] EX-5: 10% PP in solvent (68 wt. % ISOPAR™-E + 32 wt. % Propane, on the basis of the total amount of solvent). Substantial cloud point modification is observed to enable extraction at reasonable temperature (230 °C) and calculated distribution coefficients.
[0085] Experimental validation of the vapor liquid equilibria is shown in FIG. 4. Measurements of the cloud point (liquid-liquid phase equilibrium) were performed in a high-pressure variable volume view-cell located at Phasex Corporation (North Andover, MA). A solution of given composition of HDPE polymer (Formosa HB5502F) is added to the view cell at a given wt. % (5 wt. % or 9.5 wt. %) with the balance solvent (either a single solvent n-butane (nC4), n-pentane (nC5), or n-hexane (nC6)) or mixtures of ISOPAR™-E (ExxonMobil) and propane (nC3), carbon dioxide, or n-butane. The view-cell is heated and pressurized to dissolve the polymer and produce a single liquid phase. The pressure is then decreased until the solution turns cloudy, signifying the onset of liquid-liquid phase behavior and thus defining the cloud point pressure (at that particular temperature). The reported vapor pressures of the pure solvents are shown to illustrate the location of the vapor-liquid equilibrium.
Claims
85572-WO-PCT / DOW 85572 WO24CLAIMS1. A method for purifying a reclaimed polyolefin polymer, the method comprising: dissolving the reclaimed polymer with a first hydrocarbon solvent to make a first composition, wherein the first hydrocarbon solvent has an initial boiling point from 65 °C to 250 °C;removing an insoluble contaminant from the first composition;introducing a second solvent to the first composition, thereby forming a second composition, wherein:the second solvent has a final boiling point of less than 40 °C;the first hydrocarbon solvent is from 50 to 95 wt. % of the total weight of solvent in the second composition; andthe second solvent is from 5 to 50 wt. % of the total weight of solvent in the second composition;removing a portion of the second solvent and a soluble contaminant from the second composition; andremoving a portion of the first hydrocarbon solvent from the second composition, wherein removing the portion of the second solvent, the portion of the first hydrocarbon solvent, and the soluble contaminant forms a purified reclaimed polymer.
2. The method of claim 1, wherein the insoluble contaminant is removed from the first composition before the second solvent is introduced to the first composition.
3. The method of claim 1 or 2, wherein the reclaimed polymer comprises polyethylene.
4. The method of any one of claims 1 to 3, wherein the first hydrocarbon solvent comprises linear or branched alkanes, aromatic hydrocarbons, or a mixture thereof.
5. The method of any one of claims 1 to 4, wherein the second solvent is selected from CO2, ethylene, propylene, butylene, isomers thereof, and combinations thereof.
6. The method of any one of claims 1 to 4, wherein the second solvent comprises a Ci-C5 alkane.85572-WO-PCT / DOW 85572 WO257. The method of any one of claims 1 to 6, wherein the second solvent comprises CO2.
8. The method of any one of claims 1 to 7, wherein:the second composition comprises a first liquid phase comprising 5 wt. % to 60 wt. % of reclaimed polymer, on the basis of the total weight of the first liquid phase; andand the second composition comprises a second liquid phase comprising less than 5 wt. % of reclaimed polymer, on the basis of the total weight of the second liquid phase.
9. The method of any one of claims 1 to 8, wherein the dissolving of the reclaimed polymer and the removing of the insoluble contaminant each occurs at a temperature from 70 °C to 250 °C and a pressure from 1 bar to 30 bar.
10. The method of any one of claims 1 to 9, wherein the removing of the portion of the first hydrocarbon solvent, the portion of the second solvent, and the soluble contaminant occurs at a temperature from 90 °C to 250 °C and a pressure from 0 bar to 300 bar.
11. The method of any one of claims 1 to 10, wherein the first composition comprises from 95 to 100 wt. % of the first hydrocarbon solvent, on the basis of the total amount of solvent in the first composition.
12. The method of any one of claims 1 to 11, wherein:the reclaimed polymer is dissolved in a polymer dissolution vessel;the insoluble contaminant is removed in a solid / liquid separation vessel;the second solvent is introduced in an extraction vessel;the second composition comprises a first liquid phase and a second liquid phase, the second liquid phase comprising less than 5 wt. % of reclaimed polymer, on the basis of the total weight of the second liquid phase;the removing the portion of the first hydrocarbon solvent, the portion of the second solvent, and the soluble contaminant comprises removing at least a portion of the second liquid phase from the second composition in the extraction vessel; and85572-WO-PCT / DOW 85572 WO26the removing the portion of the first hydrocarbon solvent, the portion of the second solvent, and the soluble contaminant further comprises passing the first liquid phase to a polymer concentration vessel and removing at least a portion of the first hydrocarbon solvent, the second solvent, and additional soluble contaminants from first liquid phase.
13. The method of claim 12, wherein:the extraction vessel operates at a temperature of from 90 °C to 250 °C and a pressure of from 30 bar to 300 bar; andthe polymer concentration vessel operates at a temperature of from 90 °C to 250 °C and a pressure of from 0 bar (absolute) to 5 bar (absolute).
14. The method of any one of claims 1 to 13, wherein the reclaimed polymer is dissolved in a polymer dissolution vessel, and the portion of the first hydrocarbon solvent, the portion of the second solvent, and the soluble contaminant are removed from the second composition in an extraction vessel, a polymer concentration vessel, or both; the process further comprising:separating the portion of the first hydrocarbon solvent from the portion of the second solvent;transferring the separated portion of the first hydrocarbon solvent via a first recycle stream to the polymer dissolution vessel to form at least a portion of the first composition; andtransferring the separated portion of the second solvent via a second recycle stream to the extraction vessel to form at least a portion of the second composition.
15. The method of any one of claims 1 to 14, wherein the purified reclaimed polymer comprises less than 25 wt. % of insoluble contaminants and less than 25 wt. % of soluble contaminants, on the basis of the total weight of the purified reclaimed polymer.