JP2020511561A - Purification method of recovered polypropylene - Google Patents

Abstract

A method for purifying recovered polypropylene is provided. The method comprises obtaining recovered polypropylene, contacting the polypropylene with a first fluid solvent to produce extracted recovered polypropylene, and then dissolving the extracted recovered polypropylene in a solvent to produce polypropylene. And producing a first solution containing the suspended contaminants. The first solution is allowed to settle to produce a second solution containing polypropylene and residual contaminants. The second solution is purified by contacting the second solution with a solid medium to produce a third solution containing higher purity polypropylene. Finally, the higher purity polypropylene is separated from the third solution.

Description

  The present invention relates generally to methods for purifying contaminated polymers by using a pressurized solvent and a solid medium. More specifically, the present invention relates to a method for purifying recycled polymers, such as recycled plastics after consumer and industrial use, to produce colourless, transparent, odorless, virgin-like polymers. This is particularly useful for purifying polypropylene.

Polymers, especially synthetic plastics, are ubiquitous in everyday life due to their relatively low production cost and good material property balance. Synthetic plastics are used in a wide range of applications such as packaging, automobile parts, medical devices, and consumer goods. To meet the high demand for these applications, tens of billions of pounds of synthetic plastics are manufactured each year around the world. The vast majority of synthetic plastics are produced from the increasingly scarce fossil resources (eg oil and natural gas). In addition, the production of synthetic plastics from fossil resources produces CO _{2 as a} by-product.

  The ubiquitous use of synthetic plastics produces millions of tons of plastic waste each year. Most plastic waste is landfilled by municipal solid waste programs, but a significant portion of plastic waste is found in the environment as trash, which can be unaesthetic and potentially harmful to the environment. is there. Plastic waste often flows into river systems and eventually into the sea.

  To reduce the problems associated with the widespread use of plastics, plastic recycling has emerged as one solution. By recovering and reusing plastics, waste is prevented from entering landfills, demand for virgin plastics produced from fossil resources is reduced, and as a result, greenhouse gas emissions are reduced. . In industrialized countries such as the United States and the European Union, increased plastic recycling is driven by increased awareness among consumers, businesses and manufacturers. Most of the recycled materials, including plastics, are mixed into a single stream that is collected and processed at a material recovery facility (MRF). In MRF, materials are sorted, washed and packaged for resale. Plastics can be classified into individual materials such as high density polyethylene (HDPE) or poly (ethylene terephthalate) (PET), or other common plastics such as polypropylene (PP), low density polyethylene ( LDPE), Polyvinyl Chloride (PVC), Polystyrene (PS), Polycarbonate (PC), and Polyamide (PA), which may then be a mixed stream, which is then further classified. It can be washed and reprocessed into pellets, which are suitable for reuse in plastics processing such as blow molding and injection molding.

  Recycled plastics are sorted into predominantly uniform streams and washed with aqueous and / or caustic solutions, but the final reprocessed pellets are often desirous of, for example, spoiled food residues and residual flavor components. It remains highly contaminated with no waste impurities. In addition, the recycled plastic pellets are heavily colored with a mixture of dyes and pigments commonly used to color plastic articles, with the exception of plastic pellets obtained from recycled beverage containers. While some applications are less amenable to color and contamination (eg black plastic containers for paint, hidden automotive parts) most applications require colorless pellets. The need for high quality "virgin-like" recycled resins is particularly important in food and pharmaceutical contact applications such as food packaging. In addition to contamination by impurities and mixed colorants, many recycled resin products often have a heterogeneous chemical composition, with a significant amount of polymer contamination (eg polyethylene (PE) contamination in recycled PP, or vice versa). May be included.

  Mechanical recycling, also known as secondary recycling, is the process of converting recycled plastic waste into a reusable form for subsequent manufacturing processes. For a more detailed review of mechanical recycling and other plastic recovery processes, see S.W. M. Al-Salem, P .; Lettieri, J .; Baeyens, "Recycling and recovery routes of plastic solid waste (PSW): A review", Waste Management, Volume 29, Issue 10, October 10, SN03, 05-2, 026, 6-2, 6-2, 6-09, 6-IS26, 6-ISIS. Although advances in mechanical recycling technology have improved the quality of recycled polymers to some extent, mechanical decontamination approaches have fundamental limitations, such as the physical entrapment of the pigment within the polymer matrix. Therefore, even with improved mechanical recycling technology, the intense coloration and high levels of chemical pollution in the currently available recycled plastic wastes prevent the widespread use of recycled resins by the plastics industry.

  In order to overcome the fundamental limitations of mechanical recycling, a number of chemical approaches (chemical recycling) have been developed to purify contaminated polymers. Many of these methods use a solvent to decontaminate and purify the polymer. The use of a solvent allows the extraction of impurities and the dissolution of the polymer, which in turn allows another separation technique.

  For example, US Pat. No. 7,935,736 describes a method of recycling polyester from polyester-containing waste using a solvent to dissolve the polyester prior to cleaning. The US Pat. No. 7,935,736 patent further describes the need to recover polyester from solvent using precipitation.

  In another example, US Pat. No. 6,555,588 describes a method of producing polypropylene blends from plastic mixtures containing other polymers. US Pat. No. 6,555,588 describes extracting contaminants from a polymer with a selected solvent (eg, hexane) at a temperature below the dissolution temperature of the polymer for a given residence time. . The US Pat. No. 6,555,588 further describes increasing the temperature of the solvent (or second solvent) to dissolve the polymer prior to filtration. The US Pat. No. 6,555,588 patent still further describes the use of shear or flow to precipitate polypropylene from solution. The polypropylene blend described in US Pat. No. 6,555,588 contained up to 5.6 wt% polyethylene.

  In another example, European Patent Application No. 849,312 (translated from German to English) describes a process for obtaining purified polyolefin from a polyolefin-containing plastic mixture or polyolefin-containing waste. The '312 patent application uses a hydrocarbon fraction with a boiling point of gasoline or diesel fuel above 90 ° C to extract a polyolefin mixture or waste at temperatures between 90 ° C and the boiling point of its hydrocarbon solvent. Is described. European Patent Application No. 849,312 further describes removing foreign components from a solution by contacting the hot polyolefin solution with bleached clay and / or activated carbon. The '312 patent further provides for cooling the solution to a temperature below 70 ° C. to crystallize the polyolefin and then heating the polyolefin to a temperature above the melting point of the polyolefin or evaporating the deposited solvent under reduced pressure. , Or by passing the gas stream through a polyolefin precipitate and / or extracting the solvent with alcohols or ketones that boil below the melting point of the polyolefin to remove the adhering solvent.

  In another example, US Pat. No. 5,198,471 describes a method for separating a polymer from a physically admixed solid mixture (eg, waste plastic) containing a plurality of polymers, the method comprising: At the first, lower temperature, the solvent is used to form the first monolayer solution and the remaining solid components. The US Pat. No. 5,198,471 further describes heating the solvent to a higher temperature to dissolve additional polymer that was not solubilized at the first lower temperature. The US Pat. No. 5,198,471 patent describes filtering insoluble polymeric components.

  In another example, US Pat. No. 5,233,021 dissolves each component in a supercritical fluid at an appropriate temperature and pressure and then varies the temperature and / or pressure to sequentially extract the particular component. Describes a method for extracting a pure polymeric component from a multi-component structure (eg carpet waste). However, like US Pat. No. 5,198,471, US Pat. No. 5,233,021 describes only filtration of insoluble components.

  In another example, US Pat. No. 5,739,270 discloses a method and apparatus for continuously separating a polymeric component of a plastic from contaminants and other plastic components using cosolvents and working fluids. Is described. The co-solvent at least partially dissolves the polymer and the second fluid (which is liquid and in the critical or supercritical state) solubilizes the components of the polymer and partially dissolves the dissolved polymer. Precipitate from. The US Pat. No. 5,739,270 patent further describes a process for removing particulate contaminants such as glass particles by filtering a thermoplastic cosolvent (with or without working fluid).

  The known solvent-based methods for purifying contaminated polymers described above do not produce "virgin-like" polymers. In the method described above, co-dissolution, and thus cross-contamination of other polymers, often occurs. When using an adsorbent, filtration and / or centrifugation steps are often used to remove the spent adsorbent from the solution. In addition, a separation process for solvent removal, such as heating, vacuum evaporation, and / or precipitation with a precipitant is used to produce a polymer that is free of residual solvent.

US Patent No. 7,935,736 US Pat. No. 6,555,588 European Patent Application No. 849,312 US Pat. No. 5,198,471 US Pat. No. 5,233,021 US Pat. No. 5,739,270

S. M. Al-Salem, P .; Lettieri, J .; Baeyens, "Recycling and recovery routes of plastic solid waste (PSW): A review", Waste Management, Volume 29, Issue 10, October 3O25-3, 065-062, Page 64.

  Thus, using a solvent that is easily and economically removable from the polymer, it is relatively simple in terms of equipment operation, produces a significant amount of polymer without cross-contamination, and yields an essentially colorless polymer. There remains a need for improved solvent-based processes for purifying contaminated polymers that produce and produce essentially odorless polymers.

A method for purifying recovered polypropylene is provided. This method
a. Obtaining a recovered polypropylene, wherein the recovered polypropylene is selected from the group consisting of polymers after consumer use, polymers after industrial use, and combinations thereof;
b. The recovered polypropylene is combined with a first fluid solvent having a normal boiling point of less than about 70 ° C. at a temperature of about 80 ° C. to about 220 ° C. and a pressure of about 150 psig (1.03 MPa) to about 15,000 psig (103.42 MPa). Contacting to produce an extracted recovered polypropylene,
c. The extracted recovered polypropylene is treated with a first fluid solvent, a second fluid solvent, at a temperature of about 90 ° C. to about 220 ° C. and a pressure of about 350 psig (2.41 MPa) to about 20,000 psig (137.90 MPa). And dissolved in a solvent selected from the group consisting of a mixture thereof to form a first solution containing polypropylene and suspended contaminants,
d. At a temperature of about 90 ° C. to about 220 ° C. and a pressure of about 350 psig (2.41 MPa) to about 20,000 psig (137.90 MPa), a first solution containing polypropylene and suspended contaminants is allowed to settle, Forming a second solution containing polypropylene and remaining contaminants;
e. Purifying the second solution at a temperature of about 90 ° C. to about 220 ° C. and a pressure of about 350 psig (2.41 MPa) to about 20,000 psig (137.90 MPa) by contacting the second solution with a solid medium. And producing a third solution containing higher purity polypropylene,
f. Separating the higher purity polypropylene from the third solution.

  The second fluid solvent may have the same or different chemical composition as the first fluid solvent.

  In one embodiment, polypropylene is separated from the third solution at a temperature of about 0 ° C. to about 220 ° C. and a pressure of about 0 psig (0 MPa) to 2,000 psig (13.79 MPa). In another embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of at least 0.5%. In yet another embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of at least 1%. In one embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of at least 2%.

  In one embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of at least 3%. In another embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of at least 4%. In yet another embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of at least 5%.

  In one embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of up to 20%. In another embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of up to 18%. In yet another embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of up to 16%. In one embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of up to 14%. In another embodiment, the recovered polypropylene is dissolved in the fluid solvent or fluid solvent mixture at a weight percent concentration of up to 12%.

  In one embodiment, the recovered polypropylene is polypropylene derived from recycling after consumer use. In another embodiment, the recovered polypropylene is a polypropylene homopolymer or a copolymer of predominantly polypropylene. In yet another embodiment, the fluid solvent has a normal boiling point of less than about 0 ° C. and greater than about −45 ° C., and a standard enthalpy of vaporization change of less than about +25 kJ / mol.

In one embodiment, the fluid solvent is selected from the group consisting of olefinic hydrocarbons, aliphatic hydrocarbons, and mixtures thereof. In another embodiment, the aliphatic hydrocarbons, C ₁ -C ₆ aliphatic hydrocarbons, and is selected from the group consisting of mixtures. In yet another embodiment, the aliphatic hydrocarbons and mixtures thereof consists mainly C ₄ aliphatic hydrocarbons.

In another embodiment, the fluid solvent consists essentially of C ₄ liquefied petroleum gas. In one embodiment, the fluid solvent is n-butane, butane isomers, or mixtures thereof. In another embodiment, the temperature of the contacting, lysing, settling, and purifying step is from about 110 ° C to about 170 ° C.

  In one embodiment, the pressure in the contacting step is from about 1,100 psig (7.58 MPa) to about 2,100 psig (14.48 MPa). In another embodiment, the pressure in the contacting step is less than about 1,100 psig (7.58 MPa). In yet another embodiment, the pressure during the lysing, settling, and purification steps is greater than about 1,100 psig (7.58 MPa). In one embodiment, the pressure during the lysing, settling, and purification steps is greater than about 2,100 psig (14.48 MPa).

  In one embodiment, the solid medium is selected from the group consisting of inorganic materials, carbonaceous materials, and mixtures thereof. In another embodiment, the inorganic material is selected from the group consisting of silicon oxides, aluminum oxides, iron oxides, aluminum silicates, amorphous volcanic glasses, and mixtures thereof. In yet another embodiment, the inorganic material is selected from the group consisting of silica gel, diatomaceous earth, sand, quartz, alumina, perlite, fuller's earth, bentonite, and mixtures thereof.

  In one embodiment, the carbonaceous material is selected from the group consisting of anthracite, carbon black, coke, activated carbon, cellulose, and mixtures thereof. In another embodiment, contacting the polypropylene solution with the solid medium is performed within a packed bed of the solid medium. In one embodiment, the packed bed is greater than 20 cm in length.

  Additional features of the invention will be apparent to those of skill in the art upon reviewing the following detailed description, together with the examples.

It is a block flow diagram which shows the main processes of one embodiment of the present invention. 3 is a calibration curve for the calculation of the polyethylene component in polypropylene using the enthalpy value by DSC measurement. 4 is a schematic view of an experimental apparatus used in the extraction process of Examples 2 and 3. FIG. FIG. 4 is a schematic view of an experimental apparatus used in the dissolution and precipitation steps of Examples 2 and 3. It is a photograph figure of each test piece of an example.

I. Definitions As used herein, the term "reclaimed polymer" refers to a polymer that was previously used for a purpose and then recovered for further processing.

  The term "reclaimed polypropylene" (rPP), as used herein, refers to a polypropylene polymer previously used for a purpose and then recovered for further processing. Refers to.

  The term "after consumer use" as used herein refers to a material resource that occurs after the end consumer has used the material in a consumer good or product.

  The term "recycle after consumer use" (PCR), as used herein, refers to material that is produced after the end consumer discards the material in a waste stream.

  The term “after industrial use” as used herein refers to a material resource that arises during the manufacture of goods or products.

  The term "fluid solvent" as used herein refers to a substance that can exist in a liquid state under certain temperature and pressure conditions. In some embodiments, the fluid solvent may be a predominantly homogeneous chemical composition of one molecule or isomer, and in other embodiments, the fluid solvent may contain several different molecular compositions or isomers. It may be a mixture of isomers. Furthermore, in some embodiments of the invention, the term "fluid solvent" also applies to substances that are at, near, or above their critical temperature and pressure (critical point). . Those of ordinary skill in the art are well aware that a substance beyond its critical point is known as a "supercritical fluid," which does not have the typical physical properties (ie, density) of a liquid. Has been.

The term "dissolve" as used herein means that at the molecular level, a solute (polymer or non-polymer) is at least partially incorporated in the solvent. Furthermore, the thermodynamic stability of solute / solvent solutions can be described by Equation 1 below:
Formula 1
ΔG _mix = ΔH _m −TΔS _mix
In the formula, ΔG _mix is the Gibbs free energy change of the mixture of the solute and the solvent, ΔH _mix is the enthalpy change of the mixture, T is the absolute temperature, and ΔS _mix is the entropy of the mixture. The Gibbs free energy must be negative and minimal to maintain a stable solution of the solute in the solvent. Thus, any combination of solute and solvent that minimizes the negative Gibbs free energy at the appropriate temperature and pressure can be used in the present invention.

  The term "normal boiling point" as used herein is the boiling point at an absolute pressure of exactly 100 kPa (1 bar, 14.5 psia, 0.9869 atm) established by the International Union of Pure and Applied Chemistry (IUPAC). Refers to.

  As used herein, the term "standard enthalpy of vaporization change" refers to the enthalpy change required for a given amount of a substance to change from a liquid to a vapor at its normal boiling point.

  The term "polypropylene solution" as used herein refers to a solution of polypropylene dissolved in a solvent. Since the polypropylene solution may contain undissolved material, the polypropylene solution can also be a "slurry" of undissolved material suspended in a solution of polypropylene dissolved in a solvent. .

  As used herein, the terms "sedimentation" and "sedimentation" refer to the tendency of particles in a suspension to separate from a liquid in response to a force acting on the particles (usually gravity).

  As used herein, the term "suspended contaminant" refers to an undesirable or unwanted ingredient present throughout the bulk of the medium of a heterogeneous mixture.

  The term "solid medium" as used herein refers to a substance that exists in the solid state under the conditions of use. The solid medium can be crystalline, quasicrystalline, or amorphous. The solid medium may be granular and may be provided in different shapes (ie spheres, cylinders, pellets, etc.). When the solid medium is granular, the particle size and particle size distribution of the solid medium can be defined by the mesh size used for the granular medium. An example of a standard mesh size notation can be found in the American Society for Testing and Materials (ASTM) standard ASTM E11, "Standard Specification for Woven Wire Test Sieve Clost and Test Sieves." The solid medium may also be a non-woven fiber mat or woven fabric.

  The term "higher purity polypropylene solution" as used herein refers to a polypropylene solution that has less contaminants than the same polypropylene solution prior to the purification step.

  As used herein, the term "extraction" refers to the process of transferring a solute species from a liquid phase (or solid substrate) across a phase boundary into another immiscible liquid phase. The driving force for extraction is explained by the theory of distribution.

  As used herein, the term "extracted" refers to a material that has less solute species for the same material prior to the extraction step. As used herein, the term "extracted recovered polypropylene" refers to recovered polypropylene having less solute species relative to the same recovered polypropylene prior to the extraction step.

  As used herein, the term "virgin-like" means essentially contaminant-free, pigment-free, odorless, homogeneous and similar in properties to virgin polymers.

  The term "predominantly polypropylene copolymer" as used herein refers to a copolymer having more than 70 mol% polypropylene repeating units.

  As used herein, any reference to international units of pressure (eg, MPa) refers to gauge pressure.

II. Method of Purifying Contaminated Polypropylene Surprisingly, in a preferred embodiment, certain fluid solvents that exhibit temperature and pressure dependent polymer solubilities have been found to contaminate contaminated polymers (especially when used in relatively simple processes). It has been found that recovered or recycled polymer) can be used to purify to near virgin quality. This process comprises, as illustrated in FIG. 1, 1) obtaining the recovered polypropylene (step a in FIG. 1) and then 2) extraction temperature (T _E ) and extraction pressure (P _E ). , extracting the polypropylene fluid solvent and (step b in Figure 1), then 3) the melting temperature (T _D) and dissolution pressure (P _D), polypropylene dissolving in the fluid solvent (in FIG. 1 and step c), then, 4) the melting temperature _{(T D)} and dissolution pressure _{(P D),} to precipitate the polymer solution (step in FIG. 1 d), then 5) dissolution temperature _{(T D} ) And dissolution pressure (P _D ), contacting this dissolved polypropylene solution with a solid medium (step e in FIG. 1) and then separating polypropylene from the fluid solvent (step f in FIG. 1). ,including.

  In one embodiment of the invention, the purified polypropylene can be sourced from waste streams after consumer use and is essentially contaminant-free, pigment-free, odorless, homogeneous, and characterized. Similar to virgin polypropylene. Moreover, in a preferred embodiment, the physical properties of the fluid solvent of the present invention may allow for a more energy efficient method of separating the fluid solvent from the purified polypropylene.

Recovered Polypropylene In one embodiment of the invention, the method for purifying recovered polypropylene comprises obtaining recovered polypropylene. For purposes of this invention, the recovered polypropylene is sourced from consumer, industrial, commercial, and / or other specialty waste streams. For example, waste polypropylene after consumer use may come from the roadside recycling stream, which allows end-users to put used polymer from packaging and products into designated containers, which Are collected by a cleaning company or a recycling company. Post-consumer waste polymer may also come from an in-store "return" program, which allows the consumer to bring the waste polymer to the store and put it into a designated collection container. Put in. An example of waste polymer after industrial use may be waste polymer that was collected by the manufacturer as unusable material and that was produced during the manufacture or transportation of the goods or products (ie, cuttings, out-of-specification materials, initial operation). Disposal of time). An example of a waste polymer from a specialty waste stream can be a waste polymer from the recycling of electronic waste, also known as e-waste. Another example of waste polymers from specialty waste streams can be waste polymers from automotive recycling. Another example of waste polymers derived from specialty waste streams can be waste polymers derived from the recycling of used carpet and fabric.

  For the purposes of the present invention, the recovered polypropylene is a homogenous composition of the individual polymers or a mixture of different polypropylene compositions. Non-limiting examples of polypropylene compositions include homopolymers of propylene, copolymers of propylene and ethylene (including "impact" and "random clarified" copolymers), copolymers of propylene and alpha-olefins, polypropylene rubber, and those skilled in the art. Other soluble polypropylene compositions as may be apparent from

  This recovered polypropylene is further used for various pigments, dyes, processing aids, stabilizers, fillers, and other performance enhancing agents added to the polymer in polymerizing or converting the original polymer into the final form of the article. Additives may be included. Non-limiting examples of pigments are organic pigments (eg copper phthalocyanine), inorganic pigments (eg titanium dioxide), and other pigments as may be apparent to those skilled in the art. One non-limiting example of an organic pigment is Basic Yellow 51. Non-limiting examples of processing aids are antistatic agents (eg glycerol monostearate) and lubricity enhancers (eg erucamide). One non-limiting example of a stabilizer is octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate. Non-limiting examples of fillers are calcium carbonate, talc, and fiberglass.

Solvent The fluid solvent of the present invention has a normal boiling point of less than about 70 ° C. Pressurization keeps solvents having normal boiling points below the operating temperature range of the present invention with little or no solvent vapor formation. In one embodiment, the fluid solvent having a normal boiling point of less than about 70 ° C. is selected from the group consisting of carbon dioxide, ketones, alcohols, ethers, alkenes, alkanes, and mixtures thereof. Non-limiting examples of fluid solvents having a normal boiling point of less than about 70 ° C. are carbon dioxide, acetone, methanol, dimethyl ether, diethyl ether, ethyl methyl ether, tetrahydrofuran, methyl acetate, ethylene, propylene, 1-butene, 2- Butene, isobutylene, 1-pentene, 2-pentene, branched isomers of pentene, 1-hexene, 2-hexene, methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, neopentane, n- Hexane, isomers of isohexane, and other materials as may be apparent to one of ordinary skill in the art.

  The choice of fluid solvent used defines the temperature and pressure ranges used to carry out the process of the invention. A review of the properties of polymer phases in solvents of the type described in this invention can be found in the reference: McHugh et al. (1999) Chem. Rev. 99: 565-602.

Extraction In one embodiment of the invention, a method for purifying polypropylene comprises contacting the fluid solvent with the recovered polypropylene at a temperature and pressure at which the polymer is essentially insoluble in the fluid solvent. Without being bound by theory, Applicants have found that while preventing the fluid solvent from completely solubilizing the polymer, the fluid solvent diffuses into the polymer and extracts extractable contaminants. It is believed that the temperature and pressure dependent solubility can be controlled in such a way. This extractable contaminant may be residual processing aids added to the polymer, residual product formulations in contact with the polymer (eg, perfumes and flavors, dyes, and other intentionally added or unintentionally added polymers. Can be an extractable material (eg, during waste collection and subsequent accumulation with other waste materials).

  In one embodiment, the controlled extraction involves fixing the temperature of the polymer / fluid solvent system and then controlling the pressure to a pressure below the pressure or pressure range at which the polymer dissolves in the fluid solvent. Is achieved. In another embodiment, the controlled extraction is by fixing the pressure of the polymer / solvent system and then controlling the temperature below the temperature or temperature range at which the polymer dissolves in the fluid solvent. Is achieved. For temperature and pressure controlled extraction of polymers with fluid solvents, suitable pressure vessels can be used and configured in such a way as to allow continuous polymer extraction with fluid solvents. In one embodiment of the invention, the pressure vessel may be a continuous liquid-liquid extraction column, with the molten polymer pumped to one end of the extraction column and the fluid solvent at the same end of the extraction column. Or pump to the opposite end. In another embodiment, the extracted contaminant-containing fluid is removed from the process. In another embodiment, the extracted contaminant-containing fluid is purified, recovered, recycled and used in the extraction step or in another step of the process. In one embodiment of the invention, this extraction can be performed in a batch procedure, in which case the recovered polypropylene is fixed in a pressure vessel and the fluid solvent is continuously pumped into the fixed Pass through the polymer phase. The extraction time or amount of fluid solvent used depends on the desired purity of the final higher purity polymer and the amount of extractable contaminants in the recovered polypropylene of the starting material. In another embodiment, the extracted contaminant-containing fluid is contacted with the solid medium in a separate step, as described in the "Purification" section below. In another embodiment, a method of purifying recovered polypropylene comprises contacting the recovered polypropylene with a fluid solvent at a temperature and pressure at which the polymer is in a molten and liquid state. In another embodiment, the recovered polypropylene is contacted with the fluid solvent at a temperature and pressure where the polymer is in the solid state.

  In one embodiment, the method of purifying the recovered polypropylene comprises contacting the polypropylene with a fluid solvent at a temperature and pressure at which the polypropylene remains substantially undissolved. In another embodiment, the method for purifying recovered polypropylene comprises contacting the polypropylene with n-butane at a temperature of about 80 ° C to about 220 ° C. In another embodiment, the method for purifying recovered polypropylene comprises contacting the polypropylene with n-butane at a temperature of about 100 ° C to about 200 ° C. In another embodiment, the method of purifying recovered polypropylene comprises contacting the polypropylene with n-butane at a temperature of about 130 ° C to about 180 ° C. In another embodiment, a method of purifying recovered polypropylene comprises contacting polypropylene with n-butane at a pressure of about 150 psig (1.03 MPa) to about 3,000 psig (20.68 MPa). In another embodiment, a method of purifying recovered polypropylene comprises contacting polypropylene with n-butane at a pressure of about 1,000 psig (6.89 MPa) to about 2,750 psig (18.96 MPa). In another embodiment, a method of purifying recovered polypropylene comprises contacting polypropylene with n-butane at a pressure of about 1,500 psig (10.34 MPa) to about 2,500 psig (17.24 MPa).

  In another embodiment, the method of purifying recovered polypropylene comprises contacting polypropylene with propane at a temperature of about 80 ° C to about 220 ° C. In another embodiment, the method of purifying recovered polypropylene comprises contacting polypropylene with propane at a temperature of about 100 ° C to about 200 ° C. In another embodiment, the method of purifying recovered polypropylene comprises contacting polypropylene with propane at a temperature of about 130 ° C to about 180 ° C. In another embodiment, a method of purifying recovered polypropylene comprises contacting polypropylene with propane at a pressure of about 200 psig (1.38 MPa) to about 8,000 psig (55.16 MPa). In another embodiment, a method of purifying recovered polypropylene comprises contacting polypropylene with n-butane at a pressure of about 1,000 psig (6.89 MPa) to about 6,000 psig (41.37 MPa). In another embodiment, a method of purifying recovered polypropylene comprises contacting polypropylene with propane at a pressure of about 2,000 psig (13.79 MPa) to about 4,000 psig (27.58 MPa).

Dissolution In one embodiment of the invention, a method of purifying recovered polypropylene comprises dissolving the recovered polypropylene in the fluid solvent at a temperature and pressure at which the polymer is dissolved in the fluid solvent. Without wishing to be bound by theory, applicants believe that temperature and pressure can be controlled in such a way as to achieve thermodynamically favorable dissolution of the recovered polymer in the fluid solvent. . Furthermore, the temperature and pressure can be controlled in such a way that it is capable of dissolving a particular polymer or mixture of polymers and at the same time does not dissolve another polymer or mixture of polymers. This controllable dissolution allows for polymer separation from the polymer mixture.

  In one embodiment of the invention, the method for purifying a polymer comprises dissolving the contaminated recovered polypropylene in a solvent that does not dissolve the contaminant under the same temperature and pressure conditions. This contaminant can include pigments, fillers, mud, and other polymers. These contaminants are released from the polypropylene recovered on dissolution and then removed from the polymer solution by a subsequent solid-liquid separation step.

  In one embodiment, the method for purifying recovered polypropylene comprises dissolving the polypropylene in the fluid solvent at a temperature and pressure at which the polypropylene is dissolved in the fluid solvent. In another embodiment, the method of purifying recovered polypropylene comprises dissolving polypropylene in n-butane at a temperature of about 90 ° C to about 220 ° C. In another embodiment, the method of purifying recovered polypropylene comprises dissolving polypropylene in n-butane at a temperature of about 100 ° C to about 200 ° C. In another embodiment, the method of purifying recovered polypropylene comprises dissolving polypropylene in n-butane at a temperature of about 130 ° C to about 180 ° C. In another embodiment, a method of purifying recovered polypropylene comprises dissolving polypropylene in n-butane at a pressure of about 350 psig (2.41 MPa) to about 4,000 psig (27.57 MPa). In another embodiment, a method of purifying recovered polypropylene comprises dissolving polypropylene in n-butane at a pressure of about 1,000 psig (6.89 MPa) to about 3,500 psig (24.13 MPa). In another embodiment, a method of purifying recovered polypropylene comprises dissolving polypropylene in n-butane at a pressure of about 2,000 psig (13.79 MPa) to about 3,000 psig (20.68 MPa). In another embodiment, a method of purifying recovered polypropylene comprises dissolving polypropylene in n-butane at a weight percent concentration of at least 0.5%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 1%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 2%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 3%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 4%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 5%. In another embodiment, the method for purifying recovered polypropylene comprises dissolving polypropylene in n-butane at a weight percent concentration of up to 20%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 18%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 16%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 14%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 12%.

  In another embodiment, the method of purifying recovered polypropylene comprises dissolving polypropylene in propane at a temperature of about 90 ° C to about 220 ° C. In another embodiment, the method of purifying recovered polypropylene comprises dissolving polypropylene in propane at a temperature of about 100 ° C to about 200 ° C. In another embodiment, the method of purifying recovered polypropylene comprises dissolving polypropylene in propane at a temperature of about 130 ° C to about 180 ° C. In another embodiment, a method of purifying recovered polypropylene comprises dissolving polypropylene in propane at a pressure of about 2,000 psig (13.79 MPa) to about 8,000 psig (55.16 MPa). In another embodiment, a method of purifying recovered polypropylene comprises dissolving polypropylene in propane at a pressure of about 3,000 psig (20.68 MPa) to about 6,000 psig (41.37 MPa). In another embodiment, a method of purifying recovered polypropylene comprises dissolving polypropylene in propane at a pressure of about 3,500 psig (24.13 MPa) to about 5,000 psig (34.47 MPa). In another embodiment, the method of purifying recovered polypropylene comprises dissolving polypropylene in propane at a weight percent concentration of at least 0.5%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 1%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 2%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 3%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 4%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 5%. In another embodiment, the method for purifying recovered polypropylene comprises dissolving polypropylene in propane at a weight percent concentration of up to 20%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 18%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 16%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 14%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 12%.

Precipitation In one embodiment of the invention, the method for purifying polypropylene is not dissolved from the polypropylene solution by a precipitation (also known as precipitation) step at a temperature and pressure where the polymer remains dissolved in the fluid solvent. Includes separating pollutants. In one embodiment, the settling process causes the undissolved contaminants to undergo a force that causes the undissolved contaminants to move uniformly in the direction of the force. Typically, the settling force applied is gravity, but may be centrifugal force, centripetal force, or some other force. The amount of force applied and the length of settling time include, but are not limited to, contaminant particle size, contaminant particle density, fluid or solution density, and fluid or solution viscosity. Depends on multiple parameters including. The following equation (Equation 2) is a relational expression between the above-mentioned parameter and the sedimentation velocity which is a measure of the sedimentation velocity of pollutants.

式中、ｖは、沈降速度であり、ρ_ｐは、汚染物質粒子の密度であり、ρ_ｆは、流体又は溶液の密度であり、ｇは、適用される力（通常は重力）による加速度であり、ｒは、汚染物質粒子の半径であり、ηは、流体又は溶液の動的粘度である。溶液粘度を決定する重要なパラメータのいくつかとして、流体溶媒の化学組成、流体溶媒中に溶解したポリマーの分子量、流体溶媒中に溶解したポリマーの濃度、流体溶媒溶液の温度、及び流体溶媒溶液の圧力がある。

Where v is the sedimentation velocity, ρ _p is the density of pollutant particles, ρ _f is the density of the fluid or solution, and g is the acceleration due to the applied force (usually gravity). Yes, r is the radius of the contaminant particle, and η is the dynamic viscosity of the fluid or solution. Some of the important parameters that determine solution viscosity include the chemical composition of the fluid solvent, the molecular weight of the polymer dissolved in the fluid solvent, the concentration of the polymer dissolved in the fluid solvent, the temperature of the fluid solvent solution, and the fluid solvent solution. There is pressure.

  In one embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / fluid solvent solution at a temperature and pressure that maintains the polypropylene dissolved in the fluid solvent. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / n-butane solution at a temperature of about 90 ° C to about 220 ° C. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / n-butane solution at a temperature of about 100 ° C to about 200 ° C. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / n-butane solution at a temperature of about 130 ° C to about 180 ° C. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / n-butane solution at a pressure of about 350 psig (2.41 MPa) to about 4,000 psig (27.57 MPa). In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / n-butane solution at a pressure of about 1,000 psig (6.89 MPa) to about 3,500 psig (24.13 MPa). Including. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / n-butane solution at a pressure of about 2,000 psig (13.79 MPa) to about 3,000 psig (20.68 MPa). Including. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / n-butane solution, the polypropylene being dissolved at a weight percent concentration of at least 0.5%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 1%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 2%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 3%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 4%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 5%. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / n-butane solution, the polypropylene being dissolved at a weight percent concentration of up to 20%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 18%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 16%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 14%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 12%.

  In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / propane solution at a temperature of about 90 ° C to about 220 ° C. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / propane solution at a temperature of about 100 ° C to about 200 ° C. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / propane solution at a temperature of about 130 ° C to about 180 ° C. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / propane solution at a pressure of about 2,000 psig (13.79 MPa) to about 8,000 psig (55.16 MPa). In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / propane solution at a pressure of about 3,000 psig (20.68 MPa) to about 6,000 psig (41.37 MPa). In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / propane solution at a pressure of about 3,500 psig (24.13 MPa) to about 5,000 psig (34.47 MPa). In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / propane solution, the polypropylene being dissolved at a weight percent concentration of at least 0.5%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 1%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 2%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 3%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 4%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 5%. In another embodiment, a method of purifying recovered polypropylene comprises precipitating contaminants from a polypropylene / propane solution, the polypropylene being dissolved at a weight percent concentration of up to 20%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 18%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 16%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 14%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 12%.

Purification In one embodiment of the present invention, a method of purifying polypropylene comprises contacting a contaminated polymer with a solid medium at a temperature and pressure at which the polymer remains dissolved in a fluid solvent. The solid medium of the present invention is any solid material that removes at least some contamination from the solution of recovered polypropylene dissolved in the fluid solvent of the present invention. Without being bound by theory, Applicants believe that this solid medium decontaminates by various mechanisms. Non-limiting examples of possible mechanisms include adsorption, absorption, size exclusion, ion exclusion, ion exchange, and other mechanisms that may be apparent to those of ordinary skill in the art. Furthermore, the pigments and other contaminants commonly found in recovered polypropylene can be polar compounds, which can preferentially interact with solid media, which can be at least slightly polar. This polar-polar interaction is especially preferred when non-polar solvents (eg alkanes) are used as fluid solvents.

  In one embodiment of the invention, the solid medium is selected from the group consisting of inorganic materials, carbonaceous materials, or mixtures thereof. Useful examples of inorganic materials include silicon oxide, aluminum oxide, iron oxide, aluminum silicate, magnesium silicate, amorphous volcanic glass, silica, silica gel, diatomaceous earth, sand, quartz, recovered glass, alumina, Examples include perlite, fuller's earth, bentonite, and mixtures thereof. Useful examples of carbonaceous materials include anthracite, carbon black, coke, activated carbon, cellulose, and mixtures thereof. In another embodiment of the invention, the solid medium is recycled glass.

  In one embodiment of the invention, the solid medium is contacted with the polymer for a period of time with stirring. In another embodiment, the solid medium is removed from the higher purity polymer solution via a solid-liquid separation step. Non-limiting examples of solid-liquid separation steps include filtration, decantation, centrifugation, and sedimentation. In another embodiment of the invention, the contaminated polymer solution is passed through a stationary layer of solid medium. In another embodiment of the invention, the height or length of the fixed bed of solid medium is greater than 5 cm. In another embodiment of the invention, the height or length of the fixed bed of solid medium is greater than 10 cm. In another embodiment of the invention, the height or length of the fixed bed of solid medium is greater than 20 cm. In another embodiment of the invention, the solid medium is optionally replaced to maintain the desired polymer purity. In yet another embodiment, the solid medium is recycled and reused in the purification process. In another embodiment, the solid medium is recycled by fluidizing the solid medium during the rewash process.

  In one embodiment, the method of purifying the recovered polypropylene comprises contacting the polypropylene / fluid solvent solution with a solid medium at a temperature and pressure at which the polypropylene remains dissolved in the fluid solvent. In another embodiment, the method for purifying recovered polypropylene comprises contacting the polypropylene / n-butane solution with a solid medium at a temperature of about 90 ° C to about 220 ° C. In another embodiment, the method of purifying recovered polypropylene comprises contacting the polypropylene / n-butane solution with a solid medium at a temperature of about 100 ° C to about 200 ° C. In another embodiment, the method for purifying recovered polypropylene comprises contacting the polypropylene / n-butane solution with a solid medium at a temperature of about 130 ° C to about 180 ° C. In another embodiment, a method of purifying recovered polypropylene comprises contacting a polypropylene / n-butane solution with a solid medium at a pressure of about 350 psig (2.41 MPa) to about 4,000 psig (27.57 MPa). In another embodiment, the method for purifying recovered polypropylene comprises contacting the polypropylene / n-butane solution with a solid medium at a pressure of about 1,000 psig (6.89 MPa) to about 3,500 psig (24.13 MPa). Including. In another embodiment, the method for purifying recovered polypropylene comprises contacting the polypropylene / n-butane solution with a solid medium at a pressure of about 2,000 psig (13.79 MPa) to about 3,000 psig (20.68 MPa). Including. In another embodiment, a method of purifying recovered polypropylene comprises contacting a polypropylene / n-butane solution with a solid medium, the polypropylene being dissolved at a weight percent concentration of at least 0.5%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 1%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 2%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 3%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 4%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 5%. In another embodiment, a method of purifying recovered polypropylene comprises contacting a polypropylene / n-butane solution with a solid medium, the polypropylene being dissolved at a weight percent concentration of up to 20%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 18%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 16%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 14%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 12%.

  In another embodiment, the method for purifying recovered polypropylene comprises contacting the polypropylene / propane solution with a solid medium at a temperature of about 90 ° C to about 220 ° C. In another embodiment, the method for purifying recovered polypropylene comprises contacting the polypropylene / propane solution with a solid medium at a temperature of about 100 ° C to about 200 ° C. In another embodiment, the method for purifying recovered polypropylene comprises contacting the polypropylene / propane solution with a solid medium at a temperature of about 130 ° C to about 180 ° C. In another embodiment, a method of purifying recovered polypropylene comprises contacting a polypropylene / propane solution with a solid medium at a pressure of about 2,000 psig (13.79 MPa) to about 8,000 psig (55.16 MPa). In another embodiment, a method of purifying recovered polypropylene comprises contacting a polypropylene / propane solution with a solid medium at a pressure of about 3,000 psig (20.68 MPa) to about 6,000 psig (41.37 MPa). In another embodiment, a method of purifying recovered polypropylene comprises contacting a polypropylene / propane solution with a solid medium at a pressure of about 3,500 psig (24.13 MPa) to about 5,000 psig (34.47 MPa). In another embodiment, a method of purifying recovered polypropylene comprises contacting a polypropylene / propane solution with a solid medium, the polypropylene being dissolved at a weight percent concentration of at least 0.5%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 1%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 2%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 3%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 4%. In another embodiment, polypropylene is dissolved at a weight percent concentration of at least 5%. In another embodiment, a method of purifying recovered polypropylene comprises contacting a polypropylene / propane solution with a solid medium, the polypropylene being dissolved at a weight percent concentration of up to 20%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 18%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 16%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 14%. In another embodiment, polypropylene is dissolved at a weight percent concentration of up to 12%.

Separation In one embodiment of the invention, a method for purifying recovered polypropylene comprises separating a higher purity polymer from a fluid solvent at a temperature and pressure at which the polymer precipitates from solution and is no longer soluble in the fluid solvent. including. In another embodiment, precipitation of the higher purity polymer from the fluid solvent is accomplished by lowering the pressure at a fixed temperature. In another embodiment, precipitation of the higher purity polymer from the fluid solvent is accomplished by lowering the temperature at a fixed pressure. In another embodiment, precipitation of the higher purity polymer from the fluid solvent is accomplished by raising the temperature at a fixed pressure. In another embodiment, precipitation of the higher purity polymer from the fluid solvent is accomplished by lowering both temperature and pressure. The solvent can be partially or completely converted from the liquid to the vapor phase by controlling the temperature and pressure. In another embodiment, controlling the temperature and pressure of the solvent during the separation step separates the precipitated polymer from the fluid solvent without completely converting the fluid solvent to 100% vapor phase. Separation of the precipitated, higher purity polymer is accomplished by any method of liquid-liquid or liquid-solid separation. Non-limiting examples of liquid-liquid or liquid-solid separations include filtration, decantation, centrifugation, and sedimentation.

  In one embodiment, the method for purifying the recovered polypropylene comprises separating the polypropylene from the polypropylene / fluid solvent solution at a temperature and pressure at which the polypropylene precipitates from the solution. In another embodiment, the method for purifying recovered polypropylene comprises separating the polypropylene from the polypropylene / n-butane solution at a temperature of about 0 ° C to about 220 ° C. In another embodiment, a method of purifying recovered polypropylene comprises separating polypropylene from a polypropylene / n-butane solution at a temperature of about 100 ° C to about 200 ° C. In another embodiment, a method of purifying recovered polypropylene comprises separating polypropylene from a polypropylene / n-butane solution at a temperature of about 130 ° C to about 180 ° C. In another embodiment, a method of purifying recovered polypropylene comprises separating contaminants from a polypropylene / n-butane solution at a pressure of about 0 psig (0 MPa) to about 2,000 psig (13.79 MPa). In another embodiment, a method of purifying recovered polypropylene comprises separating polypropylene from a polypropylene / n-butane solution at a pressure of about 50 psig (0.34 MPa) to about 1,500 psig (10.34 MPa). In another embodiment, a method of purifying recovered polypropylene comprises separating polypropylene from a polypropylene / n-butane solution at a pressure of about 75 psig (0.52 MPa) to about 1,000 psig (6.89 MPa).

  In another embodiment, a method of purifying recovered polypropylene comprises separating polypropylene from a polypropylene / propane solution at a temperature of about -42 ° C to about 220 ° C. In another embodiment, a method of purifying recovered polypropylene comprises separating polypropylene from a polypropylene / propane solution at a temperature of about 0 ° C to about 150 ° C. In another embodiment, a method of purifying recovered polypropylene comprises separating polypropylene from a polypropylene / propane solution at a temperature of about 50 ° C to about 130 ° C. In another embodiment, a method of purifying recovered polypropylene comprises separating contaminants from a polypropylene / propane solution at a pressure of about 0 psig (0 MPa) to about 6,000 psig (41.37 MPa). In another embodiment, a method of purifying recovered polypropylene comprises separating polypropylene from a polypropylene / propane solution at a pressure of about 50 psig (0.34 MPa) to about 3,000 psig (20.68 MPa). In another embodiment, a method of purifying recovered polypropylene comprises separating polypropylene from a polypropylene / propane solution at a pressure of about 75 psig (0.52 MPa) to about 1,000 psig (6.89 MPa).

III Test Methods The test methods described herein are used to measure the effectiveness of various methods for purifying polymers. Specifically, this described method provides improved color and translucency / clarity (ie, bringing the color and opacity of the recovered polypropylene closer to that of the colorless virgin polymer). , Reduction or removal of elemental pollution (ie removal of heavy metals), reduction or removal of non-combustible pollutants (ie inorganic fillers), volatile compounds (especially volatile compounds that contribute to the malodor of recovered polypropylene) ), As well as the reduction or removal of polymer contaminants (ie polyethylene incorporation in polypropylene).

Color and opacity measurements:
The color and opacity / translucency of a polymer are important parameters that determine whether the desired visual aesthetics of articles made from the polymer can be achieved. Recycled polypropylene, especially that derived from post consumer use, is typically dark and opaque due to residual pigments, fillers, and other contaminants. Therefore, color and opacity measurements are important parameters that determine the effectiveness of polymer purification methods.

  Prior to color measurement, samples of either polymer powder or pellets were pressed into molds into square test specimens of width 30 mm x length 30 mm x thickness 1 mm (rounded corners). The powder sample was first cold-pressed into a sheet between clean stainless steel foils as a contact release layer between stainless steel platens at room temperature (about 20-23 ° C). ) To increase the density. Then, about 0.85 g of cold pressed powder or pellets was applied to a Carver Press Model C (Carver, Inc., Wabash, IN 46992-0554 USA) preheated to 200 ° C., an aluminum platen, and unused aluminum. Test specimens were compressed using a stainless steel shim with a foil release layer and cavities corresponding to the square test specimen dimensions described above. The sample was heated for 5 minutes before applying pressure. Then, after 5 minutes, the press was compressed with a hydraulic pressure of at least 2 tons (1.81 metric tons) for at least 5 seconds and then released. The mold stack was then removed and sandwiched between two thick, flat metal heat sinks for cooling. The aluminum foil contact release layer was then peeled from the sample and discarded. The flash around at least one side of the sample was stripped to the edge of the mold, then the sample was extruded from the mold. Each test specimen was visually inspected for void / bubble defects, and only samples with no defects in the color measurement area (minimum 0.7 inch (17.78 mm) diameter) were used for color measurement.

The color of each sample was characterized using the International Commission on Illumination (CIE) L ^* , a ^* , b ^* three-dimensional color space. The dimension L ^* is a measure of the lightness of the sample, L ^* = 0 corresponds to the darkest black sample and L ^* = 100 corresponds to the brightest white sample. The dimension a ^* is the red or green measurement of the sample, corresponding to red when a ^* is a positive value and green when a ^* is a negative value. The dimension b ^* is the blue or yellow measurement of the sample, which corresponds to yellow when b ^* is a positive value and blue when b ^* is a negative value. The L ^* a ^* b ^* values of each of the square test specimen samples having a width of 30 mm, a length of 30 mm, and a thickness of 1 mm were measured using a HunterLab model LabScan XE spectrophotometer (Hunter Associates Laboratory, Inc., Reston, VA 20190-5280, USA). It was measured at. This spectrophotometer was equipped with D65 as a standard light source, and was configured with an observation angle of 10 °, a field area diameter of 1.75 inches (44.45 mm), and a port diameter of 0.7 inches (17.78 mm).

The opacity of each sample is a measure of how much light passes through the sample (ie a measure of the translucency of the sample), which is measured by the HunterLab spectrophotometer described above in terms of contrast ratio opacity. Determined using the mode. Two measurements were made to determine the opacity of each sample. One is to measure the brightness Y _{white backing} of the sample with a _{white backing} and the other is to measure the brightness Y _{black backing} of the sample with a _{black backing} . The opacity was then calculated from these lightness values using Equation 3 below:

Elemental analysis:
Many of the recovered polypropylene resources have unacceptably high levels of heavy metal contamination. The presence of heavy metals (eg, lead, mercury, cadmium, and chromium) can preclude the use of recovered polypropylene in certain applications (eg, food or drug contact applications, or medical device applications). Therefore, measuring the concentration of heavy metals is important in determining the effectiveness of polymer purification methods.

Elemental analysis was performed using inductively coupled plasma mass spectrometry (ICP-MS). Depending on the effectiveness of the sample, at n = 2 to n = 6, about 0.25 g of the sample was mixed with 4 mL of concentrated nitric acid and 1 mL of concentrated hydrofluoric acid (HF) to prepare a test solution. . The sample was digested using the UltraWAVE microwave sample digestion protocol (up to 125 ° C for 20 minutes, up to 250 ° C for 10 minutes, hold 250 ° C for 20 minutes). The decomposed sample was cooled to room temperature. To this decomposed sample, 0.25 mL of 100 ppm Ge and Rh was added as an internal standard, and then diluted to 50 mL. Pre-degradation spikes were prepared by spiking virgin polymer to assess the accuracy of the measurements. Virgin polymer spike samples were weighed using the same procedure described above and tested for each single element standard of interest (including Na, Al, Ca, Ti, Cr, Fe, Ni, Cu, Zn, Cd, and Pb). The spike was done in the appropriate amount. The spikes were prepared at two different levels: "low spike" and "high spike". Each spike was prepared in triplicate. In addition to the virgin polymer spike, the blank was also spiked to ensure that there were no errors during pipetting and to track recovery throughout the process. The blank spiked sample was also prepared in triplicate at two different concentrations and treated in the same manner as the spiked virgin polymer and the test sample. 0.05, 0.1, 0.5, 1, 5, 10, 50, 100, and 500 ppb solutions containing Na, Al, Ca, Ti, Cr, Fe, Ni, Cu, Zn, Cd, and Pb. To prepare a 9-point calibration curve. All calibration standards were prepared by diluting undiluted standard reference solution with 0.25 mL of 100 ppm Ge and Rh as internal standard plus 4 mL of concentrated nitric acid and 1 mL of concentrated HF. The prepared standards, test samples, and spiked test samples were analyzed using Agilent's 8800ICP-QQQMS, optimized according to the manufacturer's recommendations. The m / z observed for each sample and the collision cell gas used for the analysis were as follows: Na, 23 m / z, H ₂ ; Al, 27 m / z, H ₂ ; Ca, 40 m / z. , H ₂ ; Ti, 48 m / z, H ₂ ; Cr, 52 m / z, He; Fe, 56 m / z, H ₂ ; Ni, 60 m / z; no gas; Cu, 65 m / z, no gas; Zn, 64 m / z, He; Cd, 112 m / z; H ₂ ; Pb, total of 206 ≧ 206, 207 ≧ 207, 208 ≧ 208 m / z, no gas; Ge, 72 m / z, all modes; Rh, 103 m / z , All modes. Ge was used as an internal standard for all elements <103 m / z, and Rh was used as an internal standard for all elements> 103 m / z.

Residual ash content:
Much of the recovered polypropylene resources include various fillers such as calcium carbonate, talcum, and fiberglass. Although these fillers were useful in the original application of the recovered polypropylene, they were used in such a way that the physical properties of the polymer could be undesired for subsequent use of this recovered polypropylene. Change the physical characteristics. Therefore, measuring the amount of filler is important in determining the effectiveness of the polymer purification method.

  Thermogravimetric analysis (TGA) was performed to quantify the amount of non-combustible material (sometimes also referred to as ash) in the sample. Approximately 5-15 mg of sample was placed on a platinum sample dish and heated to 700 ° C at a rate of 20 ° C / min in a TA Instruments model Q500TGA instrument under an air environment. Samples were held isothermally at 700 ° C for 10 minutes. After the isothermal holding, the residual mass percentage was measured at 700 ° C.

Odor analysis:
Odor sensory analysis was performed by placing approximately 3 g of each sample in a 20 mL glass vial and equilibrating the samples for at least 30 minutes at room temperature. After equilibration, each vial was opened and a trained judge sniffed the headspace (Bunny sniff) to determine the odor intensity and descriptor profile. The odor intensity was evaluated according to the following scale:
5 = very strong 4 = strong 3 = moderate 2 = weak to moderate 1 = weak 0 = odorless

Polymer contamination analysis:
Many of the recovered polypropylene resources (especially those recovered from mixed stream resources) may contain unwanted polymer contamination. Without being bound by theory, polymer incorporation (eg, polyethylene incorporation in polypropylene) can affect the physical properties of the polymer through the presence of heterogeneous phases and the resulting weak interactions. Furthermore, polymer incorporation can increase the opacity of the polymer and can also affect color. Therefore, measurement of the amount of polymer contamination is important in determining the effectiveness of the polymer purification method.

Quasicrystalline polymer incorporation was evaluated using differential scanning calorimetry (DSC). A set of 5 polypropylene / polyethylene blends was prepared to determine the amount of polyethylene incorporation in polypropylene. This includes 2, 4, 6, 8, and 10 wt% of Formolene® HB5502F HDPE (Formosa Plastics Corporation, USA) in Pro-fax 6331 polypropylene (Lyondell Basell Industries Holdings, BV). Prepared. About 5-15 mg of each sample was sealed in an aluminum DSC dish and analyzed on a TA Instruments model Q2000 DSC using the following method:
1. Equilibrate at 0.000 ° C 2. Heat to 200.00 ° C at a rate of 220.00 ° C / min 4. Mark cycle 0 4.2 Bring to 30.00 ° C at a rate of 0.000 ° C / min 5. Mark cycle 1 6.2 Heat to 200.00 ° C at a rate of 0.000 ° C / min 7. Mark cycle 2 8.2 Bring to 30.00 ° C at a rate of 0.000 ° C / min 9. Mark cycle 3 10. Heat to 200.00 ° C at a rate of 10.5.00 ° C / min 11. Mark cycle 4

  Using the 5.00 ° C / min DSC thermogram, the melting enthalpy of the HDPE peak near 128 ° C was calculated for each sample of known HDPE content. By plotting the enthalpy of fusion and the known HDPE concentration (wt%), the linear calibration curve shown in Figure 2 was obtained.

  Samples with unknown PE content were analyzed using the same DSC apparatus and method described above. PE content was calculated using the calibration curve described above. The particular HDPE used to generate the calibration curve is likely to have a different degree of crystallinity than the polyethylene (or polyethylene blend) contamination that may be present in the recovered polypropylene sample. Crystallinity can independently affect the measured enthalpies of fusion of polyethylene and thus also the calculation of the resulting polyethylene content. However, the DSC test method described herein is intended to be used as a relative indicator to compare the effectiveness of various methods of purifying polymers, and is a rigorous measure of polyethylene content in polymer blends. It is not intended to be quantitative. Although the above method describes the determination of polyethylene incorporation in polypropylene, the method is also applicable to the determination of other quasicrystalline polymers using different temperature ranges and peaks in the DSC thermogram. . In addition, other methods such as nuclear magnetic resonance (NMR) spectroscopy can be used to measure the amount of incorporation of both quasicrystalline and amorphous polymers in the sample.

  The following examples further describe and demonstrate embodiments within the scope of the present invention. These examples are provided for illustrative purposes only, and many modifications thereof are possible without departing from the spirit and scope of the invention and should not be construed as limiting the invention. Absent.

Example 1
Samples of recycled polypropylene mixed color flakes derived from after consumer use were obtained from recycled resin suppliers. This post-consumer recycled polypropylene originated in the United States and Canada. The as-received mixed color flakes were mixed and homogenized in a Century / W & P ZSK30 twin screw extruder, equipped with two 30 mm general purpose screws, each equipped with standard mixing and conveying elements. The screw rotation speed was about 50 rpm, the feeder throughput was about 20 lb / hr (9.07 kg / hr), and the barrel temperature was in the range of about 210 ° C. (die temperature) to about 150 ° C. (feed port temperature). The gray strands leaving the extruder were cooled in a room temperature water bath, dried in air and cut into pellets.

  The sample was characterized using the test methods disclosed herein. The resulting data is summarized in Table 1. The purpose of this example is to show the properties of recycled resin derived from a typical consumer use before purification.

The pellet and the corresponding square test specimen were dark gray as indicated by the L ^* a ^* b ^* values of the square test specimen. The opacity of the samples averaged about 100% opacity (ie no light transmission). A photograph of this square test sample is shown as Example 1 in FIG. As shown in FIG. 4, this sample was deep in color and lacked translucency.

  This example serves as a representative baseline for heavy metal contamination found in recycled polypropylene derived from after consumer use. It was found that the heavy metal contamination was much greater in recycled polypropylene derived from as-received post consumer use when compared to other examples.

  The sample of Example 1 has an average ash value of about 1.2117% by weight, which also serves as a baseline for the amount of non-combustible material often present in recycled polypropylene derived from after consumer use. Fulfill.

  This example also serves as a representative baseline for odorous compound contamination found in recycled polypropylene derived from after consumer use. The sample of Example 1 was found to have an odor intensity of 3.75 on a 5 point scale (5 being the strongest) and was described as having a "dusty", "dusty", "sour" odor. Was done.

  This example also serves as a typical baseline for polyethylene contamination found in recycled polypropylene derived from after consumer use. The sample of Example 1 had an average polyethylene content of about 5.5% by weight.

Example 2
Samples of recycled polypropylene mixed color flakes derived from after consumer use as described in Example 1 were processed using the experimental apparatus shown in Figures 3A and 3B and the following procedure.
1.286 g of mixed color flakes were placed in a Parr Instrument Company, Model 4552M, 7.57 liter autoclave equipped with an overhead mechanical stirrer.
2. The autoclave was then completely filled with n-butane and equilibrated to an internal fluid temperature of 140 ° C and a fluid pressure of 900 psig (6.21 MPa).
3. The material in the autoclave was then extracted using the experimental setup shown in Figure 3A and the following procedure.
a. The system was stirred at 140 ° C. and 900 psig (6.21 MPa) for 10 minutes.
b. After stirring, the system was allowed to settle at 140 ° C. and 900 psig (6.21 MPa) for 10 minutes.
c. A volume of n-butane for one container was flowed through an autoclave into a sampling flask at 140 ° C and 900 psig (6.21 MPa).
d. The above extraction procedure was repeated 4 more times.
e. The material collected in all extraction cycles was labeled as "Fraction 1".
4. The material remaining in the autoclave after extraction was then dissolved in n-butane using the experimental setup shown in Figure 3B and the following procedure.
a. The system pressure was equilibrated to 1800 psig (12.41 MPa).
b. The system was stirred at 140 ° C. and 1800 psig (12.41 MPa) for 10 minutes.
c. Stirring was then stopped and the solution was allowed to settle for 30 minutes at 140 ° C. and 1800 psig (6.21 MPa).
d. After settling, the solution was removed from the autoclave by purging with pressurized nitrogen (pre-equilibrated to 140 ° C. and 1800 psig). The solution flowing out of the autoclave through the dip tube was then passed through two heat traced solid medium columns. Each column had an inner diameter of 0.68 inches (1.73 cm) and a length of about 9.5 inches (24.13 cm). The first column was about 21 g of 8-16 mesh Fuller Ear (Jaxon Filtration, JF752-8) pre-mixed with about 21 g of 30-60 mesh Fuller Earth (Jaxon Filtration, JF752-3060, USA) in a beaker. / 16, USA). The second column contained about 21 g of silica gel (Silicycle Ultra Pure Silica Gels, SilaFlash GE60, Parc-Technol), which was pre-mixed with about 21 g of aluminum oxide (activated alumina, Selexsorb CDX, 7x14, BASF, USA) in a beaker. , USA). The fluid flow exiting the bottom of the second pressure vessel was decompressed and transferred into an Erlenmeyer flask with a branch through an expansion valve. After depressurizing the fluid stream and transferring it into an Erlenmeyer flask, the solvent vapor was allowed to escape from the side port of the flask and all liquid / solids were collected in the flask as fractions. Each fraction contained approximately 30 g of material and was labeled in order from "Fraction 2". Fractions were collected until no material was observed to elute in the flask.
5. After collecting all samples, the autoclave was equilibrated to atmospheric pressure and room temperature. Then all residual material in the autoclave was collected as a residual sample.

  Data for a sample of Fraction 3 collected according to the procedures disclosed herein are summarized in Table 1.

The solid isolated in fraction 3 of this example was white. The white solid from fraction 3 was compression molded into a square test piece which was colorless and transparent and had an appearance similar to virgin polypropylene. A photograph of a square test piece made from fraction 3 is shown as Example 2 in FIG. For reference, virgin polypropylene is shown as Example 4 in FIG. As shown in FIG. 4, this test piece was transparent and had a color and a light-transmitting property equivalent to those of virgin polypropylene. The L ^* a ^* b ^* values indicate that this square test piece is essentially colorless and comes from the square test piece of Example 1 (ie, after consumer use at the time of acquisition). (Polypropylene) showed a dramatic improvement in color. The L ^* values for the square specimens of fraction 3 of Example 2 averaged 80.44, which is significantly higher than the average L ^* value of the square specimens of Example 1 of 39.76. Had been improved to. The opacity of the Square specimens of Fraction 3 of Example 2 averaged 10.30% opacity (ie, about 90% translucency), which is also of the square specimen opacity of Example 1. It was a significant improvement compared to an average of about 100% opacity.

  The concentration of heavy metal contamination of the fraction 3 sample of Example 2 was also significantly improved compared to the sample of Example 1. For example, the sodium concentration in the fraction 3 sample of Example 2 averaged only 4100 ppb, while the sodium concentration in the sample of Example 1 averaged 136,000 ppb (a decrease of about 97%). All other measured elemental concentrations were 77-100% lower in the sample from fraction 3 of Example 2 than in the sample of Example 1.

  The ash value of the samples from fraction 3 of Example 2 averaged about 0.3874% by weight, which was significantly lower than the ash value of the samples of Example 1 (average about 1.2117% by weight).

  The sample from fraction 3 of Example 2 was found to have an odor intensity of 0.5 on a 5 point scale (5 being the strongest), which is the sample of Example 1 (odor intensity 3. Compared to the odor intensity of 75), it was much improved. Although the odor intensity was low, samples from Fraction 2 of Example 2 were described as having a "plastic" like odor similar to virgin polypropylene.

  The sample from fraction 3 of Example 2 has an average polyethylene content value of about 1.1 wt%, which is compared to the polyethylene content of the sample of Example 1 (average of about 5.5 wt%). And was greatly improved.

Example 3
Samples of recycled polypropylene mixed color flakes derived from after consumer use as described in Example 1 were processed using the experimental apparatus shown in Figures 3A and 3B and the following procedure.
6.173 g of mixed color flakes were placed in a Parr Instrument Company, Model 4552M, 7.57 liter autoclave equipped with an overhead mechanical stirrer.
7. The autoclave was then completely filled with n-butane and equilibrated to an internal fluid temperature of 140 ° C and a fluid pressure of 900 psig (6.21 MPa).
8. The material in the autoclave was then extracted using the experimental setup shown in Figure 3A and the following procedure.
f. The system was stirred at 140 ° C. and 900 psig (6.21 MPa) for 10 minutes.
g. After stirring, the system was allowed to settle at 140 ° C. and 900 psig (6.21 MPa) for 10 minutes.
h. A volume of n-butane for one container was flowed through an autoclave into a sampling flask at 140 ° C and 900 psig (6.21 MPa).
i. The above extraction procedure was repeated 4 more times.
j. The samples collected in each extraction cycle were labeled in order from "fraction 1" to "fraction 5".
9. The material remaining in the autoclave after extraction was then dissolved in n-butane using the experimental setup shown in Figure 3B and the following procedure.
e. The system pressure was equilibrated to 1800 psig (12.41 MPa).
f. The system was stirred at 140 ° C. and 1800 psig (12.41 MPa) for 10 minutes.
g. The stirring was then stopped and the solution was allowed to settle at 140 ° C. and 1800 psig (6.21 MPa) for 60 minutes.
h. After settling, the solution was removed from the autoclave by displacement with pressurized n-butane (pre-equilibrated to 140 ° C. and 1800 psig). The solution flowing out of the autoclave through the dip tube was then passed through two heat traced solid medium columns. Each column had an inner diameter of 0.68 inches (1.73 cm) and a length of about 9.5 inches (24.13 cm). In this example, all columns were empty and free of solid media. The fluid flow exiting the bottom of the second pressure vessel was decompressed and transferred into an Erlenmeyer flask with a branch through an expansion valve. After depressurizing the fluid stream and transferring it into an Erlenmeyer flask, the solvent vapor was allowed to escape from the side port of the flask and all liquid / solids were collected in the flask as fractions. Each fraction contained approximately 30 g of material and was labeled in order from "fraction 6". Fractions were collected until no material was observed to elute in the flask.
10. After collecting all samples, the autoclave was equilibrated to atmospheric pressure and room temperature. Then all residual material in the autoclave was collected as a residual sample.

  Data for a sample of Fraction 6 collected according to the procedures disclosed herein are summarized in Table 1.

The color of the solid isolated in fraction 6 of this example was off-white to yellow. Off-white to yellow solids from fraction 6 were compression molded into square test pieces and the color of each test piece was yellow. A photograph of this square test piece is shown as Example 3 in FIG. As shown in FIG. 4, the color and translucency of the sample of Example 3 was improved over the sample of Example 1, but not as much as the virgin polypropylene shown in FIG. 4 as Example 4. Even without the step of contacting with the solid medium, the L ^* a ^* b ^* values are similar to those for the square specimen of fraction 6 of Example 3 for the sample of Example 1 (ie, consumer use as received). The color is improved with respect to the polypropylene derived from the latter). The square specimens from fraction 6 of Example 3 have an average L ^* value of 72.41, which is an improvement over the average L ^* value of the square specimens of Example 1 of 39.76. It had been. The opacity of the Square specimens of Fraction 6 of Example 3 averaged 35.25%, which is also improved compared to the average opacity of square specimens of Example 1 of about 100% opacity. Was there.

  For the sample of fraction 6 of Example 3, the concentration of heavy metal contamination was also improved compared to the sample of Example 1. For example, the sample from fraction 6 of Example 3 had an average sodium concentration of only 16400 ppb, whereas the sample of Example 1 had an average sodium concentration of 136,000 ppb (a reduction of about 88%). All other measured elemental concentrations were 82-100% lower in the sample from fraction 6 of Example 3 than in the sample of Example 1.

  The ash value of the fraction 6 sample of Example 3 averaged about 0.2292 wt%, which was significantly lower than the ash value of the sample of Example 1 (about 1.2117 wt% average).

  The sample from fraction 6 of Example 3 was found to have an odor intensity of 0.5 on a 5 point scale (5 being the strongest), which is the sample of Example 1 (odor intensity 3. Compared to the odor intensity of 75), it was significantly improved. Although the odor intensity was low, the sample of Fraction 6 of Example 3 was described as having a "plastic" -like odor similar to virgin polypropylene.

  The sample from fraction 6 of Example 3 had an average polyethylene content value of about 1.0 wt%, which is compared to the polyethylene content of the sample of Example 1 (average of about 5.5 wt%). And was greatly improved.

Example 4: Virgin polypropylene comparative sample Pro-fax 6331 polypropylene (Lyondell Basell Industries Holdings, BV) was used as all "virgin PP" comparative samples. Virgin PP pellets were processed into square specimens according to the methods described herein. The L ^* a ^* b ^* values of the test pieces produced from virgin PP averaged 85.13 ± 0.18, −0.71 ± 0.01, and 2.27 ± 0.02, respectively. The square specimen had an average opacity of 7.56 ± 0.21% opacity. This example serves as a comparison of the amount of heavy metal contamination found in a representative sample of virgin polypropylene. The virgin polypropylene sample had an average ash value of about 0.3031% by weight. The virgin PP pellets had an odor intensity of 0.5 on a 5 point scale (5 being the strongest) and had an odor described as "plastic". No polyethylene was detected in the virgin propylene sample.

  All documents cited herein, including any patents or patent applications that are cross-referenced or related, are hereby incorporated by reference in their entirety, unless expressly excluded or otherwise limited. Be done. Citation of any reference to such invention, whether it is prior art relating to any invention disclosed and claimed herein, or whether it is alone or in any combination with any other reference No admission is made to teach, suggest, or disclose. Furthermore, if any meaning or definition of a term in this document conflicts with the meaning or definition of the same term in the document incorporated by reference, the meaning or definition given to that term in this document shall apply. Shall be.

  While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims (15)

A method for purifying recovered polypropylene, comprising:
a. Obtaining the recovered polypropylene, wherein the recovered polypropylene is selected from the group consisting of polymers after consumer use, polymers after industrial use, and combinations thereof;
b. A first fluid having a normal boiling point of less than about 70 ° C. at a temperature of about 80 ° C. to about 220 ° C. and a pressure of about 150 psig (1.03 MPa) to about 15,000 psig (103.42 MPa). Contacting with a solvent to produce extracted recovered polypropylene,
c. The extracted recovered polypropylene is treated with a first fluid solvent and a second fluid at a temperature of about 90 ° C. to about 220 ° C. and a pressure of about 350 psig (2.41 MPa) to about 20,000 psig (137.90 MPa). Dissolving in a solvent and a solvent selected from the group consisting of a mixture thereof to form a first solution containing polypropylene and suspended contaminants;
d. The first solution containing polypropylene and suspended contaminants is allowed to settle at a temperature of about 90 ° C. to about 220 ° C. and a pressure of about 350 psig (2.41 MPa) to about 20,000 psig (137.90 MPa). Forming a second solution containing polypropylene, and remaining contaminants;
e. Contacting the second solution with a solid medium at a temperature of about 90 ° C. to about 220 ° C. and a pressure of about 350 psig (2.41 MPa) to about 20,000 psig (137.90 MPa). To produce a third solution containing higher purity polypropylene,
f. Separating the higher purity polypropylene from the third solution,
The method, wherein the second fluid solvent has the same or a different chemical composition as the first fluid solvent.   The method of claim 1, wherein the polypropylene is separated from the third solution at a temperature of about 0 ° C. to about 220 ° C. and a pressure of about 0 psig (0 MPa) to 2,000 psig (13.79 MPa). .   The method of claim 1, wherein the recovered polypropylene is dissolved in a fluid solvent or fluid solvent mixture at a weight percent concentration of at least 0.5%.   The method of claim 1, wherein the recovered polypropylene is dissolved in a fluid solvent or fluid solvent mixture at a weight percent concentration of at least 2%.   The method of claim 1, wherein the recovered polypropylene is dissolved in a fluid solvent or fluid solvent mixture at a weight percent concentration of at least 5%.   The method of claim 1, wherein the recovered polypropylene is dissolved in a fluid solvent or fluid solvent mixture at a weight percent concentration of up to 20%.   The method of claim 1, wherein the recovered polypropylene is dissolved in a fluid solvent or fluid solvent mixture at a weight percent concentration of up to 12%.   The method of claim 1, wherein the recovered polypropylene is polypropylene derived from recycling after use by a consumer.   The method of claim 1, wherein the recovered polypropylene is a polypropylene homopolymer or a predominantly polypropylene copolymer.   The method of claim 1, wherein the fluid solvent has a normal boiling point of less than about 0 ° C. and greater than about −45 ° C. and a standard enthalpy of vaporization change of less than about +25 kJ / mol.   The method of claim 1, wherein the fluid solvent is selected from the group consisting of olefinic hydrocarbons, aliphatic hydrocarbons, and mixtures thereof. Wherein the aliphatic hydrocarbon is an aliphatic hydrocarbon C ₁ -C _6, and is selected from the group consisting of mixtures A method according to claim 11.   12. The method of claim 11, wherein the fluid solvent is n-butane, butane isomers, or mixtures thereof.   The method of claim 1, wherein the temperature in the contacting, dissolving, settling, and refining steps is from about 110 ° C to about 170 ° C.   The method of claim 1, wherein the pressure in the contacting step is from about 1,100 psig (7.58 MPa) to about 2,100 psig (14.48 MPa).

Images