Reducing surface and bulk contamination in plastics

Abstract

The present invention generally relates to a method of reducing pollution from plastics. The resulting purer plastics can be used in demanding applications.

Description

Technical Field

[0001] The present invention generally relates to a method for producing a purer plastic from a first plastic. More specifically, the first plastic is subjected to bulk purification or surface and bulk purification, wherein the total contamination present in the first plastic is reduced. The resulting purer plastic is purer enough to allow use in demanding applications. Background Art

[0002] Synthetic plastics are ubiquitous in everyday life due to their relatively low production costs and well-balanced material properties. They are widely used in a variety of applications, such as packaging, automotive parts, medical devices and consumer products. In order to meet the high demands of these applications, hundreds of millions of tons of synthetic plastics are produced worldwide each year. The vast majority of synthetic plastics are produced from increasingly scarce fossil resources such as oil and natural gas. In addition, the manufacture of synthetic plastics from fossil sources results in greenhouse gases (GHG), mainly CO2, being emitted into the atmosphere.

[0003] The widespread use of synthetic plastics has resulted in millions of tons of plastic waste being generated each year. While most plastic waste is landfilled through municipal solid waste programs, a large portion of plastic waste is found in the environment as litter, which is unsightly and can be harmful to ecosystems. In addition, plastic waste leaks into the environment, for example being washed into river systems and eventually out to the sea.

[0004] Plastic recycling has become a solution to alleviate the problems associated with poor management of plastic waste. Recycling and reusing plastics diverts waste from landfills and reduces the demand for virgin plastics made from fossil resources, thereby reducing GHG emissions. In developed regions of the world, such as the United States and the European Union, plastic recycling rates are rising due to increased awareness among consumers, businesses and industrial manufacturing and due to regulatory frameworks. Most recycled materials, including plastics (except films), are mixed into a single stream, which is collected and processed by a material recycling facility (MRF). At the MRF, the materials are sorted, washed and packaged (e.g., in bales) for resale. Plastics can be divided into individual materials, such as a single stream of high-density polyethylene (HDPE) and poly(ethylene terephthalate) (PET), or a mixed stream of other common plastics (such as polypropylene (PP), low-density polyethylene (LDPE), polyvinyl chloride (PVC), polystyrene (PS), polycarbonate (PC) and polyamide (PA)). The single or mixed streams can then be further sorted, washed and reprocessed in a plastics recycling facility (PRF) into pellets suitable for reuse in plastics processing such as extrusion blow molding, profile extrusion, injection molding and film making.

[0005] However, the use of these recycled plastics is currently limited due to contamination, which makes the plastics less valuable compared to virgin plastics. The key to increasing recycling rates and reducing CO2 emissions and plastic pollution is to reduce contamination to levels that allow for wider use in more end markets, especially those involving demanding applications.

[0006] Film is a special case of recycled plastics, and it is mainly polyolefin in composition. Film provides unique challenges for recycling that have not yet been solved. The recycled film supply stream can be divided into two general categories: 1) pre-consumer recycled film, which includes in-plant waste / offcuts that can be reused in the same process of producing the film and industrial post-recycling (PIR) film, which is a film produced by in-plant waste that is not used in the same process of producing it; 2) post-consumer recycling (PCR) film, including commercial post-recycling film and household post-recycling film, which is a film that has been used in business but not directly used by household consumers (e.g., post-store shrink wrap, pallet packaging, wholesale bags, furniture packaging, agricultural films, etc.), and the household post-recycling film is a film that has been used directly by household consumers in business (e.g., retail bags, retail food packaging, outer packaging of diapers and hygiene products, garbage bags, etc.). Industrial post-film waste for recycling is collected on a plant-by-plant basis in controlled terminal markets, and may or may not involve (or require) significant cleaning steps before recycling. Commercial post-film is collected at the point of sale and transported to various PRFs dedicated to films for various cleaning operations and ultimately distributed to the terminal market. In the United States, domestic post-film is mainly collected in store recycling programs, where the final consumer returns the film to the collection box of the local store. Film-based PRFs collect film waste and transport it to the terminal market after sorting and cleaning. Due to pollution, the use of film recycling materials is very limited. The pollution of film is higher than other forms, because its surface area to volume ratio is higher, which makes the opportunity for external pollution greater. At present, most of the recycled plastics based on film are recycled down to non-circular and limited size markets, such as plastic lumber. With the growth of film-based waste collection, the demand for terminal markets other than plastic lumber is essential. Ideally, film-based waste will eventually find reuse in film-based applications, thereby ensuring continuous circulation.

[0007] End markets cannot grow unless contamination is significantly reduced. Given the large volumes of membranes used in demanding end markets, it is important that recycled plastics from these markets re-enter the same end markets to support circularity. Therefore, the ability to remove even higher levels of contaminants is critical to achieving circularity and reducing CO2 emissions and plastic pollution. Plastic contamination is even more problematic for membranes given the extremely large surface area per use and the mobility of waste in the environment through air and water.

[0008] Although pollution is problematic for all end-market applications, demanding markets have even more stringent requirements, especially for certain chemical pollutants. According to the chemical structure of the pollutant, the relevant chemical pollutants are divided into various chemical categories. Non-limiting examples of pollutants of these chemical categories are heavy metals, pesticides, dioxins, furans, polychlorinated biphenyls (PCBs), phthalates, polycyclic aromatic hydrocarbons (PAHs), organotin, bisphenols, isothiazolin, glyphosate, alkylphenols, alkylphenol ethoxylates, aromatic amines and flame retardants. In addition, the target levels of these pollutants may be extremely low. For example, the target level can be the order of magnitude of parts per million (ppm), parts per billion (ppb) and parts per trillion (ppt), wherein the initial contamination plastics may contain 1,000 times the level of the target level. Therefore, it is usually necessary to reduce 1,000 times the chemical pollution.

[0009] Mechanical recycling, also known as secondary recycling, is the process of converting recycled plastic waste into a reusable form for subsequent manufacturing. A more detailed review of mechanical recycling and other plastic recycling methods is described in SMA1-Salem, P. et al., Waste Management, 29 (10) (2009), 2625-2643. Mechanical recycling of rigid plastics generally involves some form of surface washing, followed by drying and melt densification. The melt densification step generally includes melt filtration and devolatilization. For film-based materials, there are dry and wet processes. In the dry process, a controlled film flow is generally chopped, dried, and then melt-extruded into a final form. Melt filtration and devolatilization are generally part of the extrusion step. In the wet process, a controlled film flow is generally chopped, washed in one or more aqueous solutions, dried, and then melt-extruded into a final form. Melt filtration and devolatilization are generally part of the extrusion step. The above methods are generally acceptable at removing intentional surface contaminants such as paper labels and unintentional surface contaminants such as dirt, but are poor at removing bulk contaminants.

[0010] U.S. Patent 10,022,725 discloses a mechanical recycling process for cleaning linear low density polyethylene (LLDPE) / LDPE film for recycling. The patent also discloses the steps of shredding, a first water washing step, a second comminution step involving wet grinding, one or more friction washing steps using hot water in at least one step, drying or multiple drying steps, and a compacting step. The method may be quite effective in removing certain loosely bound surface contaminants, but will be ineffective in removing bulk contaminants because the solubility of bulk contaminants in the aqueous washing medium is extremely low and / or the diffusion rate of bulk contaminants within the plastic is limited.

[0011] U.S. Patent 9,616,595 discloses a mechanical recycling process for de-inking surface printed plastic films. The patent also discloses the steps of grinding, ink removal step, general washing, cleaning solution recovery, pigment recovery and drying. The ink removal step involves the use of an aqueous cleaning fluid with a high pH and a selective cleaning agent such as lauryl sulfate and high turbulence. The method claims the ability to remove surface printed ink, which may cause chemical contamination after heating during the recycling process. The method will have a limited ability to remove bulk contaminants due to the limited solubility of the bulk contaminants in the aqueous washing medium and / or the limited diffusion rate of the bulk contaminants in the plastic.

[0012] In order to overcome the fundamental limitations of mechanical recycling, many methods have been developed to purify contaminated plastics. Most of these methods use solvents to clean and purify plastics. U.S. Patent 7,935,736 discloses a method for recycling polyester from plastic waste using a solvent to dissolve the polyester before cleaning. The patent also discloses the need to use a precipitant to recover the polyester from the solvent.

[0013] U.S. Patent 6,555,588 discloses a method for producing a polypropylene blend from a plastic mixture containing other polymers. The patent discloses extracting contaminants from the polymer at a temperature below the dissolution temperature of the polymer in a selected solvent such as hexane within a specific residence time. The starting material is a porous pellet, and the extraction conditions are below the melting temperature to achieve transportation in the method. The patent also discloses increasing the temperature of the solvent (or second solvent) to dissolve the polymer before filtering. In addition, the patent discloses the use of shear flow for precipitating polypropylene from solution. The polypropylene blend described in the patent contains up to 5.6% by weight of polyethylene contaminants.

[0014] European Patent Application 849,312 discloses a method for obtaining purer polyolefins from a plastic mixture containing polyolefins or a waste containing polyolefins. The patent application discloses extracting the polyolefin mixture or waste with a hydrocarbon portion of a gasoline fuel or a diesel fuel having a boiling point above 90°C at a temperature between 90°C and the boiling point of the hydrocarbon solvent. The patent application also discloses contacting the hot polyolefin solution with bleaching clay and / or activated carbon to remove foreign components from the solution. In addition, the patent application discloses cooling the solution to a temperature below 70°C to crystallize the polyolefin, and then removing the adhering solvent by heating the polyolefin above its melting point, or evaporating the adhering solvent in a vacuum or passing a gas stream through the polyolefin to precipitate, and / or extracting the solvent with an alcohol or ketone having a boiling point below the melting point of the polyolefin.

[0015] U.S. Patent No. 5,198,471 discloses a method for separating a polymer from a physically mixed solid mixture containing multiple polymers (e.g., waste plastics) using a solvent at a first lower temperature to form a first single-phase solution and a remaining solid component. The patent also discloses heating the solvent to a higher temperature to dissolve additional polymers that are insoluble at the first lower temperature. Finally, the patent discloses filtering of the insoluble polymer component.

[0016] U.S. Patent No. 5,233,021 discloses a method for extracting pure polymer components from a multi-component structure (e.g., waste carpet) by dissolving each component in a supercritical fluid at a suitable temperature and pressure, and then changing the temperature and / or pressure to sequentially extract specific components. However, similar to U.S. Patent No. 5,198,471, this patent only discloses the filtration of undissolved components.

[0017] U.S. Patent No. 5,739,270 discloses a method and apparatus for continuously separating a polymer component of a plastic from contaminants and other components of the plastic using a cosolvent and a working fluid. The cosolvent at least partially dissolves the polymer, and a second fluid (i.e., in a liquid, critical, or supercritical state) solubilizes components from the polymer and precipitates some of the polymer dissolved in the cosolvent. The patent also discloses a step of filtering the thermoplastic cosolvent (with or without the working fluid) to remove particulate contaminants (such as glass particles).

[0018] U.S. Patent No. 5,368,796 discloses a method for surface cleaning polyethylene film. The patent also discloses the following steps: shredding, a first surface washing step (involving a boiling solvent at a temperature lower than the melting temperature of polyethylene and at or near ambient pressure, while applying 30min of violent mechanical stirring to wipe off ink), a second surface washing step (involving a fresh solvent lower than the melting temperature of polyethylene, while applying 30min of violent mechanical stirring), a third surface washing step (involving a solvent lower than the melting temperature of polyethylene, while applying 30min to 60min of violent mechanical stirring, and devolatilization) and melt densification. Optionally, the method may include a water washing step before being treated with a solvent to remove surface dirt. The patent also discloses that solvent washing realizes extraction, wherein the solvent does not dissolve the polymer. However, a small amount of wax, usually <1% by weight, can be removed. The solvent washing and extraction steps are further disclosed as being carried out at the boiling point of the solvent, and the boiling point is selected to be lower than the softening point of polyethylene to avoid agglomeration. The above method focuses on the removal of surface printing ink, and does not mention the removal of overall permeable contaminants, such as those previously described.

[0019] U.S. Patent Application 2009 / 0178693 discloses a method for purifying plastics. The patent application also discloses a multi-step process involving granulation to form plastic chips, surface washing with supercritical CO2, surface washing and extraction with a high boiling point solvent or solvent mixture (such as limonene and ethylene lactic acid), final surface washing with supercritical CO2 to remove the high boiling point solvent on the surface, and devolatilization. It is also disclosed that the plastic chip feed material is stirred with the solvent and the shape of the chips is maintained. In addition, it is disclosed that the recovered material remains as chips, which means that the method is completed at a temperature below the initial melting point of the plastic.

[0020] U.S. Patent No. 9,834,621 discloses a method for purifying polypropylene. The patent also discloses contacting the regenerated polypropylene 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 280°C and a pressure of about 10 atm to about 544 atm to produce extracted regenerated polypropylene; dissolving the extracted regenerated polypropylene in a solvent selected from the group consisting of the first fluid solvent, the second fluid solvent, and a mixture thereof at a temperature of about 90°C to about 280°C and a pressure of about 14 atm to about 544 atm to produce a first solution comprising polypropylene, at least one dissolved contaminant, and at least one suspended contaminant ... The method is characterized in that the first solution containing polypropylene, at least one dissolved contaminant and at least one suspended contaminant is sedimented at a pressure of about 544 atm to produce a second solution containing polypropylene, at least one dissolved contaminant and less at least one suspended contaminant; filtering the second solution at a temperature of about 90° C. to about 280° C. and a pressure of about 14 atm to about 544 atm to produce a third solution containing purer polypropylene, at least one dissolved contaminant and even less at least one suspended contaminant; and separating the purer polypropylene from the third solution; and wherein the second fluid solvent has the same chemical composition as the first fluid solvent or a different chemical composition. The above method is very suitable for removing contaminants. However, the ability to dissolve, settle and filter plastics is very difficult and may not be feasible or practical for plastics with high molecular weight (MW), such as those used in films and blow molded containers. In addition, the above method does not mention the removal of surface contaminants before extraction and dissolution, thereby increasing the burden of such disclosed methods, especially filtration.

[0021] In summary, the solvent-based methods for purifying contaminated plastics described above do not address the problem of adequately and effectively removing surface and bulk contaminants from plastics to enable use in demanding applications, particularly film and rigid applications involving high MW plastics. Therefore, there is a need for a method that: 1) produces purer plastics, i.e., plastics without significant amounts of contamination, which would allow them to be used in demanding applications; 2) is relatively simple in terms of the number of unit operations; and 3) can be used in high MW plastics, such as those derived from film and rigid applications. Summary of the invention

[0022] In an embodiment of the present invention, a method for extracting pollutants from a first plastic to produce a purer plastic is provided, the method comprising providing a first plastic containing individual pollutants, each of which has a certain concentration; extracting the individual pollutants from the first plastic using an extraction solvent at a certain temperature and pressure in an extraction stage to produce a purer plastic containing individual pollutants each having a certain concentration; wherein the extraction is liquid / liquid, wherein the temperature is higher than the initial melting point of the first plastic; wherein the first plastic individual pollutants include at least one of alkylphenols, bisphenols, dioxins, PCBs and phthalates; wherein the concentration of each individual pollutant in the purer plastic is reduced compared to the concentration of each individual pollutant in the first plastic; and wherein the average value of the reduction in the concentration of the first plastic pollutants relative to the purer plastic pollutants is at least about 55% or LOQ. DETAILED DESCRIPTION

[0023] I. Definitions

[0024] As used herein, the term "plastic" refers to polymers such as polyethylene (PE), PP, PET, LLDPE, LDPE, HDPE, polyethylene copolymers, ethyl vinyl acetate copolymers (EVA), ethyl vinyl alcohol copolymers (EVOH), ethylene acrylic acid copolymers (EAA), PS, PC, PVC, PET, SBS, PA, etc., or mixtures thereof. Such polymers are characterized by high molecular weight, which generally determines melt processability and solid-state mechanical properties. For the purposes of the present invention, the terms "polymer" and "plastic" are used interchangeably, and the term "MW" refers to the weight average molecular weight of the polymer.

[0025] As used herein, the term "recycled plastic" refers to various forms of regrind, post-industrial, post-commercial, or post-domestic plastics, including films, fibers, nonwovens, and rigid packaging.

[0026] As used herein, the term "recycled plastic" refers to recycled plastic that is converted into a form for use in making products and packaging for blending with virgin plastic or itself. The recycled plastic may be purer than the recycled plastic, or may be identical except in form.

[0027] As used herein, the term "pre-consumer plastic" refers to plastic waste that has not met its intended end purpose and has not been used commercially or by the end consumer. Pre-consumer plastic has two recycling subcategories, including 1) internal scrap / regrind and 2) post-industrial. Internal scrap / regrind differs from post-industrial in that post-industrial is not reusable in the same process in which it was produced. The recycling resulting from post-industrial recovery is called post-industrial recycling or PIR.

[0028] As used herein, the term "post-consumer plastic" refers to plastic recyclate that has served its intended end purpose and has been used in commerce. Post-consumer plastic has two recycling subcategories, including 1) post-commercial plastic and 2). post-domestic plastic. Post-commercial plastic includes plastic that has been used in commerce and served its intended purpose. Examples include post-store recyclate and wholesale bags. Post-domestic plastic includes plastic that has been used in retail consumers' homes. Examples include pre-store plastic, retail bags, retail packaging, etc. The recycling generated from the recycling of post-consumer plastic is called post-consumer recycling or PCR.

[0029] As used herein, the term "first plastic" refers to a plastic that is fed into a purification process and has a contamination level that may include both surface and bulk contamination. Non-limiting examples of first plastics are recycled film and recycled HDPE bottles.

[0030] As used herein, the term "purer plastic" refers to a plastic produced from a first plastic by a purification process. The purer plastic has a generally lower level of contamination than the first plastic.

[0031] As used herein, the term "1st life plastic" refers to virgin plastic that has not been used in its polymer form for any purpose.

[0032] As used herein, the term "contaminant" refers to any undesirable material contained on or in a plastic. The term "chemical contaminant" refers to any undesirable chemical substance on the surface of a plastic or in the body of a plastic, and includes the molecular or elemental composition of the contaminant. Depending on the intent, the terms can be used interchangeably. For example, paper contaminants include cellulose. Therefore, cellulose is a chemical contaminant among paper contaminants. As used herein, the term "contamination" refers to the sum of all contaminants, and the term "chemical contamination" refers to the sum of all chemical contaminants. Chemical contaminants are grouped by category, which includes chemical contaminants with similar chemical structures. For example, As, Hg and Cr are chemical contaminants in the "heavy metal" classification. Each contaminant can have different chemical properties, such as solubility and diffusivity in plastics, and target levels depending on concentration and end-use markets.

[0033] As used herein, the term "surface contaminant" refers to contaminants on the surface of a plastic. Similarly, the term "surface chemical contaminant" refers to the molecular or elemental composition of the surface contaminant. Surface contaminants may be loosely attached to the plastic surface by physical attraction, or more strongly attached to the plastic surface by polar or other forces. Typically, a surface contaminant will have less than about 80% of its surface area embedded in the plastic.

[0034] As used herein, the term "bulk contaminant" refers to the contaminant in the bulk of the plastic. Similarly, the term "bulk chemical contaminant" refers to the molecular or elemental composition of the bulk contaminant. Typically, a bulk contaminant will have more than about 80% of its surface area embedded in the plastic.

[0035] As used herein, the terms "surface contamination" and "surface chemical contamination" refer to the sum of all surface contaminants and all surface chemical contaminants, respectively.

[0036] As used herein, the terms "total pollution" and "total chemical pollution" refer to the sum of all total pollutants and all total chemical pollutants, respectively.

[0037] As used herein, the term "total contamination" refers to the sum of surface contamination and bulk contamination and the sum of all surface chemical contamination and bulk chemical contamination, respectively.

[0038] As used herein, the term "permeable contaminants" refers to chemical contaminants that are soluble and diffusible in plastics. Non-limiting examples of permeable contaminants are formaldehyde, bisphenol A, and naphthalene.

[0039] As used herein, the term "impermeable contaminants" refers to chemical contaminants that are insoluble or non-diffusible in plastics. Non-limiting examples of impermeable contaminants are heavy metals and gel particles composed of cross-linked or ultra-high molecular weight plastics (too large to diffuse).

[0040] As used herein, the term "permeable contamination" is the sum of all permeable contaminants, and the term "impermeable contamination" is the sum of all impermeable contaminants. The sum of all permeable and impermeable contaminants is a "chemical contaminant" if described in molecular or elemental terms, or simply a "contaminant" if described in general terms (such as cellulose and paper).

[0041] As used herein, the term "intentional contaminant" refers to a contaminant that is intentionally added by the supply chain for a specific purpose to benefit the producer, retailer or consumer, but may not be desired in recycled plastics. Examples include printed matter, paper labels, adhesives for labels, pigments (such as TiO2), processing additives (such as antioxidants (AO)), etc., which are necessary for marketing, branding, processability and / or end-use performance. As used herein, the term "intentional chemical contaminant" refers to an intentional contaminant described by its chemical composition. As used herein, the term "intentional contamination" refers to the sum of all intentional contaminants, and the term "intentional chemical contamination" refers to intentional contamination described by its chemical composition.

[0042] As used herein, the term "unintentional contaminant" refers to any contaminant that is not intentionally added. Examples include dirt and cross-contamination that is not intentionally added by the producer, retailer, or consumer. As used herein, the term "unintentional chemical contaminant" refers to an unintentional contaminant described by its chemical composition. As used herein, the term "unintentional contamination" refers to the sum of all unintentional contaminants, and the term "unintentional chemical contamination" refers to an unintentional contamination described by its chemical composition.

[0043] As used herein, the term "densified" refers to a state of plastic where the bulk density of the plastic is higher than that of the original / pre-densified plastic and the original surface of the plastic is reduced and / or made inaccessible to wetting fluids. The process of producing a densified material is called densification.

[0044] As used herein, the term "melt densification" refers to densification near, at, or above the initial melting point of the plastic. Non-limiting methods of melt densification include melt extrusion and agglomeration using equipment such as the Herbold HV series plastic compactor.

[0045] As used herein, the term "initial melting point" refers to the peak melting point (highest endothermic peak on a zero slope baseline) of a plastic as measured using differential scanning calorimetry (DSC). For purposes of the present invention, the terms "initial melting point," "melting point," "melting temperature," and "initial melting temperature" are used interchangeably. For amorphous materials and / or materials that lack a distinct melting point, the limiting temperature will be the approximate softening point of the material, which may be best characterized by the glass transition temperature. Those skilled in the art will understand the appropriateness of the criteria for non-semi-crystalline materials.

[0046] As used herein, the term "hexane" refers to a blend of hexane isomers, such as n-hexane (at least 45 vol %, and typically about 53 vol %), isohexane (2-methylpentane, 3-methylpentane, and 2,3-dimethylbutane), and neohexane (2,2-dimethylbutane).

[0047] As used herein, the term "limit of quantitation" or "LOQ" refers to the lower limit of detection of a given chemical contaminant as determined by the analytical method disclosed in Section IX. The LOQ is a function of the method used and can vary depending on the test method. The LOQ used herein is specific to the method listed in Section IX.

[0048] As used herein, the term "ppm" means parts per million, "ppb" means parts per billion, and "pptr" means parts per trillion.

[0049] II. First Plastic

[0050] Plastics are primarily free of contamination (virgin plastic) when first produced at resin suppliers such as Dow, Nova, ExxonMobil, etc. However, during the life cycle of plastics (from production to distribution, consumer utilization, and ultimate recycling), contamination is introduced intentionally or unintentionally.

[0051] Non-limiting examples of intentional contamination include surface printing, paper labels, adhesives for labels, pigments (such as TiO2), processing additives (such as antioxidants (AO)), etc., which are necessary for market, brand, processability and / or end-use performance. Non-limiting examples of unintentional contamination are dirt, cross-contamination, certain heavy metals, pesticides, dioxins, furans, PCBs, etc. In addition, unintentional contamination can be generated by reactions involving intentional pollutants, such as oxidation of paper labels to dioxins, degradation of adhesives or printing binders, etc. Most of the latter occur during the melt densification method used in the recycling process. In addition, during the melt processing steps (such as those used for original packaging or product manufacturing and / or the latter recycling), the oxidation of plastics will produce unintentional contamination, such as gel. In addition, unintentional contamination may be caused by interaction with products. For example, packaging materials containing cleaning mixtures (such as limonene, surfactants, etc.), food (such as various organics), etc. will potentially be contaminated by such products. Finally, unintentional contamination can enter plastics during production, such as contaminating plastics with reaction byproducts, unreacted monomers, etc.

[0052] It should be recognized that different sources of recycled plastics have different contamination and associated risks. Obviously, recycled plastic streams of unknown origin and life cycle will be the most abundant, but also represent the highest possibility of contamination. On the other hand, controlled recycled plastic streams are available and present lower potential risks for demanding applications. For example, if it is known that the recycled plastic stream comes from medical or food applications, such recycled plastic streams will not contain any undesirable contaminants until distributed to consumers, otherwise these plastics will not be approved for these applications. Therefore, the contamination that prevents reuse in these same applications is mainly unintentional contamination, which must originate from external sources and enter the plastic through surface contamination. Small amounts of contamination may be caused by reactions involving intentional contamination, such as the oxidation of cellulose to dioxins during melt densification.

[0053] Pre-consumer plastics generally have the lowest contamination levels due to their known composition and controlled history. It can include intentional contamination, such as surface printing and sunscreens, but because these are known and controlled, it is very easy to find applications that tolerate such known contaminants. In addition, due to the controlled history, pre-consumer plastics tend to have a small amount of unintentional contamination, thereby preventing external contamination. Therefore, pre-consumer plastics originally intended for demanding applications such as medical or food would be an ideal source of recycled plastics for various uses with minimal cleaning / purification. The latter type of pre-consumer plastic in film form is called "approved source post-industrial film" (ASPIF). On the downside, ASPIF streams are in very limited supply and do not support roundness.

[0054] Post-consumer plastics are usually more polluted than pre-consumer plastics. Considering the slightly controlled life cycle in the commercial supply chain, the commercial post-consumer sub-category of post-consumer plastics has the second lowest pollution level relative to pre-consumer recycling. Generally, commercial post-recycled plastics will have known and controlled levels of intentional pollution, so they can be widely used as recycled plastics. However, it is known that unintentional pollution is ubiquitous, and there are problems with this stream, which hinders widespread use in controlled fields such as medical or food. Commercial post-plastics derived from controlled fields such as medical or food may be returned to these fields after sufficient cleaning / purification. Commercial post-plastics derived from demanding applications in the form of films are referred to as "approved source commercial post-film" (ASPCF). In order to meet the continued demand for purer recycled plastics, recycled source material suppliers have recently introduced commercial post-film sources with more controlled and known histories. These new sources are called high-custody sources and are mainly used with commercial post-film streams. Therefore, relative to general commercial post-film sources, high-custody commercial post-film sources should have reduced pollution levels. The downside is that these high-custody sources are limited in volume and cost more.

[0055] The post-consumer, post-home subcategory has the highest levels of contamination given the uncontrolled lifecycle within the commercial channel. This category of plastics has high levels of intentional and unintentional contamination that are highly variable, unknown, and uncontrolled. This category of plastics can include sources of plastics that were not originally intended for demanding applications.

[0056] Surprisingly, the purer plastics produced by the present invention may allow plastics from post-industrial sources (ASPIF and uncontrolled sources), post-commercial sources (ASPCF and uncontrolled sources), and post-domestic sources to be used in demanding areas of medical and food applications with certain restrictions.

[0057] For purposes of the present invention, non-limiting examples of plastics are films, sheets, injection molded parts, blow molded parts, fibers, nonwovens, wovens, thermoformed parts, and extruded strands.

[0058] The first plastic can be a virgin plastic or a recycled plastic. In addition, the first plastic can be a first life plastic (used only once before it enters the recycled plastic stream), a second life plastic (used twice before it enters the recycled plastic stream), or a higher life plastic (used multiple times before entering the recycled plastic stream). In an embodiment of the present invention, the first plastic comprises recycled plastic. In another embodiment of the present invention, the first plastic comprises virgin plastic. In one embodiment of the present invention, the first plastic comprises a film. In another embodiment of the present invention, the first plastic is selected from the group consisting of a film, an injection molded part, a blow molded part, a nonwoven, a woven, a thermoformed part, an extruded strand, or a mixture thereof.

[0059] In an embodiment of the present invention, the first plastic comprises regrind / offcut / in-plant scrap plastic. In another embodiment of the present invention, the first plastic comprises post-industrial plastic. In another embodiment of the present invention, the first plastic comprises post-industrial film. In another embodiment of the present invention, the first plastic comprises post-industrial nonwoven. In yet another embodiment of the present invention, the post-industrial film is ASPIF. In an embodiment of the present invention, the first plastic comprises post-commercial plastic. In another embodiment of the present invention, the first plastic comprises post-commercial film. In another embodiment of the present invention, the first plastic comprises post-commercial nonwoven. In yet another embodiment of the present invention, the post-commercial film is ASPCF. In another embodiment of the present invention, the first plastic comprises high-shelf commercial post-film. In an embodiment of the present invention, the first plastic comprises post-domestic plastic. In another embodiment of the present invention, the first plastic comprises post-domestic film. In another embodiment of the present invention, the first plastic comprises post-domestic nonwoven.

[0060] In an embodiment of the present invention, the first plastic comprises polystyrene, copolystyrene, polyamide, copolyamide, polycarbonate, thermoplastic elastomer, styrene block copolymer, polyester, copolyester, polyvinyl alcohol, pvc, copolymers of any of the above, and mixtures of any of the above. In an embodiment of the present invention, the first plastic comprises polyolefin, polyolefin copolymer, and polyolefin polar copolymer. In another embodiment of the present invention, the first plastic comprises LDPE and LLDPE copolymer. In another embodiment of the present invention, the first plastic comprises PP. In another embodiment of the present invention, the first plastic comprises HDPE and HDPE copolymer. In an embodiment of the present invention, the first plastic comprises a film, and the film comprises polyethylene and polyethylene copolymer.

[0061] The first plastic can be in many forms, including but not limited to pellets, micronized pellets, ground pellets, chopped films, chopped or ground injection molded parts, chopped or ground blow molded parts, thermoformed parts, chopped nonwovens or wovens, extruded strands, or agglomerated particles. In an embodiment of the present invention, the first plastic comprises pellets.

[0062] III. Pollutants and pollution

[0063] Pollutants can generally be broken down into two migration categories: 1) permeable; and 2) impermeable. Permeable pollutants have solubility and diffusivity in the first plastic to allow migration into, through, and out of the plastic due to the chemical potential gradient. In other words, permeable pollutants and groups called permeable pollution are movable. Impermeable means that the pollutant does not have enough solubility and diffusivity to significantly move into, through, and out of the plastic. In other words, the impermeable pollution represented by the sum of all impermeable pollutants is essentially fixed. Therefore, no matter where the impermeable pollutant is first deposited, such pollution will remain in that position until physically removed, convectively transferred, or placed in contact with a different material that is permeable to the pollutant.

[0064] The chemical contaminants in the first plastic can be diverse, but generally belong to one of several related chemical classes. Representative classes include pesticides, aldehydes, allergenic fragrances, indolines (izioalines), alkylphenol ethoxylates, alkylphenols, bisphenols, dioxins, dioxin-like, furans, PCBs, organotins, metals, phthalates, polyaromatic hydrocarbons (PAHs), etc. Only some of these chemical classes are commonly found in pre- and post-consumer recycled materials, including pesticides, alkylphenol ethoxylates, alkylphenols, bisphenols, dioxins, dioxin-like, furans, PCBs, metals, organotins, phthalates, and PAHs.

[0065] Using the analytical methods disclosed in the Part IX method, the LOQs for various contaminants can vary by several orders of magnitude. For example, the LOQ for a typical pesticide is about 10 ppb; the LOQ for a typical alkylphenol ethoxylate is about 50 ppb; the LOQ for a typical alkylphenol is about 5 ppb; the LOQ for bisphenol A is about 5 ppb; the LOQ for a typical dioxin is about 0.2 pptr; the LOQ for a typical furan is about 0.2 pptr; the LOQ for a typical PCB is about 5 pptr; the LOQ for a typical heavy metal is about 100 ppb; the LOQ for a typical organotin is about 300 pptr; the LOQ for a typical phthalate is 50 ppb; and the LOQ for a typical PAH is 1 ppb.

[0066] As shown in Tables 1a-1i, several membrane sources were broadly classified for chemical contamination using the analytical methods disclosed in the Part IX method, including three ASPIF sources, three high-custody commercial post-membrane sources, three commercial post-membrane sources, and one domestic post-membrane source. Note: To simplify the presentation of chemical contamination results, concentration data are shown as LOQ rather than absolute weight fraction. For example, if the contaminant concentration is 10 ppm and the LOQ is 1 ppm, the concentration would be 10 X LOQ or simply 10 in the data table.

[0067] Table 1a-1i

[0068] Chemical contamination from ASPIF, High Custody Commercial Post-Use (HCPC), Commercial Post-Use (PC), and Domestic Post-Use (PH) membrane sources

[0069] Table 1a

[0070] Pesticide chemical pollution

[0071]

[0072] Table 1b

[0073] Alkylphenol Ethoxylate Chemical Pollution

[0074]

[0075]

[0076] Table 1c

[0077] Alkylphenol Chemical Pollution

[0078]

[0079] Table 1d

[0080] Bisphenol chemical pollution

[0081]

[0082] Table 1e

[0083] Dioxin, furan and PCB chemical pollution

[0084]

[0085]

[0086] Table 1f

[0087] Heavy metal chemical pollution

[0088]

[0089]

[0090] Table 1g

[0091] Organotin chemical pollution

[0092]

[0093] Table 1h

[0094] Phthalate Chemical Pollution

[0095]

[0096]

[0097] Table 1i

[0098] PAH chemical pollution

[0099]

[0100] Except for alkylphenols and heavy metals and small amounts of organotin and PAH, the ASPIF sources tested are mainly free of detectable levels of chemical contaminants. The chemical contamination results of these ASPIF sources are used as a guide to the chemical contamination levels representing these controlled end markets, and prove that heavy metals with low transfer risks are prevalent in all film sources anyway. Therefore, heavy metals are not included in the ongoing analysis within this application. The high-custody commercial post-membrane sources tested are largely free of pesticides and alkylphenol ethoxylates, but contain detectable levels of alkylphenols, bisphenol A, dioxins / furans / PCBs and PAHs and low levels of phthalates. The commercial post-membrane sources tested are severely polluted by each category evaluated; for example, dioxins are usually up to 40 times the LOQ, but for one source, dioxins are up to 200 times the LOQ. The tested household post-sources are the most polluted; for example, dioxins are up to 300 times the LOQ, and PCBs are up to 180 times the LOQ.

[0101] From Tables 1a-1i, representative chemicals were selected from various categories based on prevalence in at least the spectrum of the source. The selected representative chemicals within these categories include: piperonyl butoxide (indicating pesticides); 4-tert-octylphenol hexaethoxylate and isononylphenol triethoxylate (indicating alkylphenol ethoxylates); isononylphenol and 4-tert-amylphenol (indicating alkylphenols); bisphenol A (indicating phenols); 1.2.3.6.7.8-HxCDD, 1.2.3.4.6.7.8-HpCDD, and OCDD (indicating dioxins); OCDF (indicating furans); PCB 105 and PCB 118 (indicating PCBs); monobutyltin and dibutyltin (indicating organotins); dibutylphthalate and di-2-ethylhexylphthalate (indicating phthalates); and fluoranthene and phenanthrene (indicating polycyclic aromatic hydrocarbons (PAHs)).

[0102] In an embodiment of the present invention, the chemical pollutants in the first plastic include at least one chemical pollutant, and the chemical pollutants include the following group: pesticides, alkylphenols, alkylphenol ethoxylates, bisphenols, dioxins, furans, PCBs, phthalates, PAHs or mixtures thereof.

[0103] In an embodiment of the present invention, the pesticides include piperonyl butoxide, BAC, DEET and DDAC. In another embodiment of the present invention, the alkylphenol ethoxylates include isononylphenol monoethoxylate, isononylphenol diethoxylate, isononylphenol triethoxylate and isononylphenol tetraethoxylate. In another embodiment of the present invention, the alkylphenols include isononylphenol, 4-tert-butylphenol and 4-tert-amylphenol. In even another embodiment of the present invention, the bisphenols include bisphenol A. In even another embodiment of the present invention, the dioxins include 1,2,3,6,7,8-HxCDD, 1.2.3.4.6.7.8-HpCDD and OCDD. In even another embodiment of the present invention, the furans include OCDF. In even another embodiment of the present invention, the PCBs include PCB 77, PCB 81, PCB 126, PCB 105, PCB 114, PCB 118, PCB 123, PCB 156 and PCB 167. In another embodiment of the present invention, the phthalates include di-2-propylheptyl phthalate, diisobutyl phthalate, dibutyl phthalate, di-1-ethylhexyl phthalate, and diisononyl phthalate. In even another embodiment of the present invention, the PAHs include acenaphthene, acenaphthylene, anthracene, benzo[a]anthracene, benzo[b]fluoroanthracene, benzo[e]pyrene, benzo[ghi]perylene, Cyclopenta[cd]pyrene, fluoranthene, fluorene, naphthalene, phenanthrene and pyrene. In even another embodiment of the present invention, the organotin includes monobutyltin, dibutyltin and dioctyltin.

[0104] In an embodiment of the present invention, the contaminants in the first plastic may include 4-tert-amylphenol. In an embodiment of the present invention, the contaminants in the first plastic may include bisphenol A. In an embodiment of the present invention, the contaminants in the first plastic may include OCDD. In an embodiment of the present invention, the contaminants in the first plastic may include PCB 118. In an embodiment of the present invention, the contaminants in the first plastic may include di-2-ethylhexyl phthalate.

[0105] In order to simplify the presentation of the purification results for the present invention objects and related examples, the number of chemicals presented per chemical class is limited to the above representative chemicals for each chemical class as shown in Table 2, along with the associated LOQ and corresponding levels of the ASPIF sources tested. Note: Although more in-depth and complete chemical analysis was completed for all objects of the present invention, only representative chemicals are continuously shown. This simplification does not affect or alter the present invention or the conclusions drawn therefrom. The specific chemicals selected fully and consistently represent the broader categories with respect to purification.

[0106] Table 2

[0107] Simplified list of chemical contaminants and associated LOQ concentrations

[0108]

[0109]

[0110] In embodiments of the invention, each pesticide is present at a concentration below its corresponding LOQ in the purer plastic; wherein the first plastic has at least one detectable pesticide. In embodiments of the invention, bisphenol A is present at a concentration below its corresponding LOQ in the purer plastic; wherein the first plastic has at least detectable bisphenol A. In embodiments of the invention, each dioxin is present at a concentration below its corresponding LOQ in the purer plastic; wherein the first plastic has at least one detectable dioxin. In embodiments of the invention, each PCB is present at a concentration below its corresponding LOQ in the purer plastic; wherein the first plastic has at least one detectable PCB. In embodiments of the invention, each phthalate is present at a concentration below its corresponding LOQ in the purer plastic; wherein the first plastic has at least one detectable phthalate.

[0111] In an embodiment of the present invention, the concentration of piperonyl butoxide in the purer plastic is less than about 10 ppb; wherein the concentration of piperonyl butoxide in the first plastic is higher than 10 ppb; the concentration of 4-tert-amylphenol in the purer plastic is less than about 5 ppb; wherein the concentration of 4-tert-amylphenol in the first plastic is higher than 5 ppb; the concentration of bisphenol A in the purer plastic is less than about 5 ppb; wherein the concentration of bisphenol A in the first plastic is higher than 5 ppb; the concentration of OCDD in the purer plastic is less than about 0.2 pptt; wherein the concentration of OCDD in the first plastic is higher than 0.2 pptr; the concentration of PCB118 in the purer plastic is less than about 10 pptr; wherein the concentration of PCB118 in the first plastic is higher than 10 pptr; the concentration of di-2-ethylhexyl phthalate in the purer plastic is less than about 50 ppb; wherein the concentration of di-2-ethylhexyl phthalate in the first plastic is higher than 50 ppb.

[0112] Typically, the efficacy of a cleaning process in removing a particular chemical contaminant is determined by the removal efficiency, which is defined as the difference between the concentration of the chemical contaminant in the first plastic and the concentration of the chemical contaminant in the purer plastic divided by the concentration of the chemical contaminant in the first plastic, expressed as a percentage. However, since concentrations below LOQ cannot be determined, the removal efficiency is somewhat insufficient. For example, if the cleaning process reduces contamination from 2 X LOQ to less than LOQ, the removal efficiency can be anywhere between 50% and 100%, which is a significant difference. Therefore, the removal efficiency is sufficient only when both the first plastic and the purer plastic chemical contaminant concentrations are above LOQ. For simplicity, if the purer plastic has a chemical contaminant concentration below LOQ, the removal efficiency is calculated by assuming that the chemical contaminant concentration of the purer plastic is at LOQ, and the removal efficiency is considered to be the minimum value and is specified as >. For the above example, the removal efficiency would be calculated as 100(2 X LOQ–1 X LOQ) / (2 X LOQ)=100(2-1) / 2=50%. Therefore, the removal efficiency would be >50%. In some cases, the purer plastic will have higher levels of contaminants than the first plastic due to 1) measurement errors, 2) hot and cold spots of contaminants in the first plastic, 3) external contamination during sampling, and 4) added contamination from the purification process. In this case, the removal efficiency is set to 0% to not skew the average results. If this happens consistently in a given cleaning process, it is more likely due to the purification process and should be examined more carefully, but this is generally not the case with the cleaning process of the present invention.

[0113] In an embodiment of the invention, the removal efficiency of piperonyl butoxide contaminants is >55%, wherein the concentration of piperonyl butoxide in the first plastic is at least 10 ppb. In another embodiment of the invention, the removal efficiency of piperonyl butoxide contaminants is >75%, wherein the concentration of piperonyl butoxide in the first plastic is at least 10 ppb. In another embodiment of the invention, the removal efficiency of piperonyl butoxide contaminants is >90%, wherein the concentration of piperonyl butoxide in the first plastic is at least about 10 ppb.

[0114] In an embodiment of the present invention, the removal efficiency of 4-tert-amylphenol contaminants is >55%, wherein the concentration of 4-tert-amylphenol in the first plastic is at least 5 ppb. In another embodiment of the present invention, the removal efficiency of 4-tert-amylphenol contaminants is >70%, wherein the concentration of 4-tert-amylphenol in the first plastic is at least 5 ppb.

[0115] In an embodiment of the present invention, the removal efficiency of bisphenol A contaminants is >55%, wherein the concentration of bisphenol A in the first plastic is at least 5 ppb. In another embodiment of the present invention, the removal efficiency of bisphenol A contaminants is >75%, wherein the concentration of bisphenol A in the first plastic is at least 5 ppb. In another embodiment of the present invention, the removal efficiency of bisphenol A contaminants is >90%, wherein the concentration of bisphenol A in the first plastic is at least 5 ppb.

[0116] In an embodiment of the invention, the removal efficiency of OCDD contaminants is >55%, wherein the concentration of OCDD in the first plastic is at least about 0.2 pptr. In another embodiment of the invention, the removal efficiency of OCDD contaminants is >75%, wherein the concentration of OCDD in the first plastic is at least about 0.2 pptr. In another embodiment of the invention, the removal efficiency of OCDD contaminants is >85%, wherein the concentration of OCDD in the first plastic is at least about 0.2 pptr.

[0117] In an embodiment of the present invention, the removal efficiency of PCB 118 contaminants is >55%, wherein the concentration of PCB 118 in the first plastic is at least 10 pptr. In another embodiment of the present invention, the removal efficiency of PCB 118 contaminants is >75%, wherein the concentration of PCB 118 in the first plastic is at least 10 pptr. In another embodiment of the present invention, the removal efficiency of PCB 118 contaminants is >90%, wherein the concentration of PCB 118 in the first plastic is at least 10 pptr.

[0118] In an embodiment of the present invention, the removal efficiency of phenanthrene contaminants is >55%, wherein the concentration of phenanthrene in the first plastic is at least 1 part per billion. In another embodiment of the present invention, the removal efficiency of phenanthrene contaminants is >75%, wherein the concentration of phenanthrene in the first plastic is at least 1 part per billion. In another embodiment of the present invention, the removal efficiency of phenanthrene contaminants is >90%, wherein the concentration of phenanthrene in the first plastic is at least 1 part per billion.

[0119] In general, chemical contaminants include permeable and impermeable chemical contaminants. Without wishing to be bound by theory, applicants believe that, with respect to polyethylene and polypropylene type recycled materials, contaminants such as pesticides, dioxins, furans, PCBs, phthalates, PAHs, bisphenols, alkylphenols and alkylphenol ethoxylates should be permeable; and contaminants such as heavy metals should be impermeable. Depending on the molecular size, organotins can be permeable or impermeable.

[0120] Pollution can be located on the surface of plastics or in the whole. Through the surface cleaning technology available on the market, the pollution on the surface is most conveniently and easily removed. If the surface pollution in the plastic is permeable, it will become the whole pollution through the diffusion mechanism over time, thus complicating the reduction and limiting the effectiveness of the surface cleaning technology. If the surface pollution is impermeable in the plastic, such pollution will not spread into the whole and will be reduced by simple surface cleaning methods such as aqueous washing. The whole pollution of permeable or impermeable types cannot be effectively removed by simple surface purification methods such as aqueous washing. The whole pollution of impermeable types (also referred to as whole impermeable pollution) is trapped in the whole plastic and can be released by the mechanism including melt convection, melt filtration or dissolution / decomposition of the whole plastic.

[0121] As previously discussed, contamination can be introduced from the outside throughout the life cycle of the plastic. If the contamination is impermeable, such contamination will remain largely on the surface until recycling during the life cycle of the plastic. If the contamination is permeable, the contamination will migrate into the bulk plastic over time. Therefore, in the absence of contamination or purification events, the contamination will remain essentially constant, but the balance of surface and bulk contamination will change over time, but will approach equilibrium over a long period of time. Typically, loosely bound surface contamination such as dirt can be 0.01% to about 0.1% by weight; while chemical contamination, especially chemical contaminants to which the present invention relates, will be ppm, ppb or even pptrillion.

[0122] Permeable and impermeable contamination represent different challenges in various uses such as medical or food applications. For example, permeable contamination, whether in the overall plastic or on the surface of the plastic, will have the potential to migrate to uncontaminated materials such as products or human skin. Therefore, if the packaging contains permeable contaminants, such contaminants will have the potential to migrate into the product and make it unsuitable for various uses. However, if the contaminant is impermeable and in the overall plastic, it will have a low ability to transfer to the product or the user's skin unless the overall plastic is decomposed or ingested. Therefore, packaging can potentially use this contaminated plastic material, and there is no risk of contamination transfer to the product or directly to the skin. However, if the contaminant is impermeable and on the surface of the plastic, such contaminants will have the ability to transfer to the product or skin by direct contact transfer, and will be unacceptable for use in these harsh applications. Permeable and impermeable surface contamination can be converted into overall contamination by convection mechanisms (such as melt mixing and melt densification). These methods exchange or eliminate surface areas with the overall material. For example, if the film melt of surface contamination is densified or melt extruded into different shapes, such as pellets, all original surface contamination will become overall contamination, whether it is impermeable or not, and such overall contamination will be more difficult to remove with purification methods. Melt densification is common in the recycling industry. It is also common to crush incoming plastics in the recycling industry. The latter method does not convert surface contamination into overall contamination usually. Ideally, surface purification methods such as surface washing occur on the original contaminated surface such as shredded film, wherein all original surface areas are accessible by surface washing fluids.

[0123] Usually, it is difficult to distinguish surface contamination and overall contamination using analytical methods. Most analytical methods for permeable chemical contaminants relate to>>6 hours of extended time period and exposed to>>100:1 extreme solvent and plastic mass ratio from plastic solvent extraction pollutants, and then use methods such as gas chromatography-mass spectrometry (GC-MS) to quantitatively pollute the pollutants in the solvent. Such analytical methods quantitatively pollute, but can not distinguish between surface and overall pollutants. The efficiency of the purification method for removing surface contamination can be estimated according to the difference of pollution before and after the surface cleaning step, but it is assumed that overall pollution is not significantly affected, which may be the case of surface washing with the aqueous surface washing fluid discussed in the present invention. The more accurate way of quantitative surface contamination is by washing, then at different times to pollutant solvent extraction, and then extrapolating the amount of pollutants removed in infinitesimal time, which will approximate the amount of surface contamination. However, the method is time-consuming and costly, particularly for pollutants that are usually difficult to measure. In addition, because the balance of surface and overall pollutants is dynamic, it is difficult to quantify without reference to accurate sampling time. A simple method for quantifying general surface contamination (not chemical surface contamination or substance based chemical contamination) is to weigh the first plastic before and after the surface washing step.

[0124] Typically, bulk contamination will not be significantly removed by simple aqueous surface washing. Permeable bulk contamination can be removed by diffusion mechanisms via chemical potential gradients. While bulk impermeable contamination is essentially trapped by the bulk polymer, methods for releasing the trapped contaminant include melt convection, melt filtration, and dissolution / disintegration of the plastic.

[0125] IV. Surface Purification Methods

[0126] Surface purification methods reduce surface contamination. One such method is to wash the surface with a surface washing fluid that is usually water-based. Surface washing is ideally completed before any melt mixing or melt densification to allow effective cleaning of the original contaminated surface. The first plastic is generally in the form of pellets, loose or compacted films, loose or compacted flexible packaging, loose or compacted rigid materials, loose or compacted nonwovens, etc., which are difficult to wash due to their overall size. Therefore, before surface washing, a granulation or chopping step is preferred. For films, it is particularly important to strip all available film layers so that the washing fluid can approach all original surface contamination. Therefore, the size reduction step before surface washing should not significantly reduce the surface area to volume ratio of the regeneration source, or exchange with a new surface area. In an embodiment of the present invention, the surface washing of the first plastic is carried out after the chopping or granulation step. Surface washing will include significant mechanical agitation to loosen surface dirt and other contaminants, thereby allowing physical removal and transfer to the washing fluid, wherein the dirt or other contaminants may or may not be dissolved. As used herein, a surface washing process is any process in which a recycled plastic in its original contaminated form (except without eliminating the possibility of a volumetric size reduction of more than 25% of the original surface) is contacted with an aqueous solution under mechanical agitation and then separated from the aqueous medium now containing such contamination. Such processes will generally remove most of the loosely bound surface contamination, including but not limited to dirt, wood, loosely bound paper, and some surface chemical contamination. Typical levels of loosely bound surface contamination based on the recycled source of the membrane are between about 0.01% and 0.1% by weight. For the purposes of the present invention involving a first plastic that is surface washed, the surface washing process will remove greater than about 80% of the loosely bound surface contamination, as determined by Method 2 shown in Section IX.

[0127] Surface washing technology is widely used in the market. A representative technology comes from Lindner (Lindner Washtech GmbH, 4, Germany). The technology is described in detail elsewhere (https: / / www.lindner-washtech.com / system-solutions), but involves water washing under vigorous mechanical agitation and the application of caustic soda to remove the binder, followed by drying and the possibility of granulation.

[0128] Another representative surface washing technology is from Herbold (Herbold Meckesheim USA, North Smithfield, RI). This technology is described in detail elsewhere (https: / / www.herbold.com / en / machines / washing-separating-drying-2 / ) and also involves various water washing steps under vigorous mechanical agitation, followed by drying and granulation.

[0129] Another representative technology is from Sorema (Sorema Srl, Anzano del Parco, Italy). This technology is described in detail elsewhere (http: / / sorema.it / en_US / applications / washing-line / ) but involves similar aqueous procedures relative to Lindner and Herbold.

[0130] Another representative surface washing technology is from Cadel, called deinking (Cadel Deinking, Alicante, Spain). The technology is described elsewhere (http: / / cadeldeinking.com / en / ), but basically involves surface washing of the material using a high temperature water-based solution with a specific surfactant, followed by water rinsing, drying, devolatilization and granulation. This method differs from other known methods in that it requires the removal of surface printing ink. This will be advantageous because the burden of removing chemical contaminants is reduced by the overall purification method of the present invention.

[0131] Three surface washing technologies of the prior art were evaluated to remove target categories of chemical contaminants (Comparative Examples 1, 2, and 3). Each surface washing technology was evaluated using different regeneration membrane inputs with different contamination levels. In general, the surface washing technologies of the prior art cannot adequately purify the regenerated material for use in controlled end markets. For the target contaminants, although the initial contamination of the corresponding regeneration source is low, the commercial technology cannot be reduced to a level close to the LOQ. In addition, the average removal efficiency of 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate is less than about 55%.

[0132] V. Melt Densification

[0133] The plastic from the surface washing step will generally be in a similar geometric form and have a surface area to volume ratio similar to that of the incoming recycled plastic. For example, if the recycled plastic is a loose film, after the surface washing, the film will leave the surface purification as a shredded film. Because such loose plastics are difficult to feed into certain overall purification methods, it may be desirable to densify such plastic melts before overall purification. The preferred method for melt densification is melt extrusion. Melt extrusion not only densifies the plastic, but it can also provide the pressure required for downstream overall purification such as liquid-liquid extraction. Melt extrusion may also include optional steps such as melt filtration and / or devolatilization to remove bulk contaminants and / or volatile bulk contaminants. In addition, the melt-densified plastic can be further pressurized using a melt pump. A melt pump may be required to increase the pressure required for the downstream overall purification step. Other densification methods are known in the art, including rotating disks and rotating drum densifiers, which are performed at lower temperatures relative to melt-based methods. In an embodiment of the present invention, the melt densification includes melt extrusion. In another embodiment of the invention, the melt extrusion comprises melt filtration. In another embodiment of the invention, the melt extrusion comprises melt devolatilization. In an embodiment of the invention, the melt densification comprises melt extrusion, melt filtration, melt devolatilization and melt pumping.

[0134] VI. Overall purification

[0135] In general, bulk contamination will not be significantly reduced by simple aqueous surface washing. Melt filtration and melt devolatilization will have the potential to remove large geometric bulk contaminants and remove some volatile bulk contaminants, but will be largely ineffective for most bulk contaminants, especially at the levels required.

[0136] One technology available on the market for accomplishing overall purification is the InterRema Refresher from EREMA (EREMA Group, Ansfelden, Austria) https: / / www.erema.com / en / refresher / ) TM This technique is described in detail elsewhere, but essentially involves devolatilizing the particulate material to remove volatile organics at a temperature below the initial melting point of the plastic for an extended period of time. Most of the chemical contaminants associated with recycled materials and discussed in the previous section are highly non-volatile, having normal boiling points generally above 200°C. Therefore, this type of devolatilization technique will have limited ability to remove most of the chemical contaminants mentioned in this application.

[0137] Other techniques based on devolatilization are common. These can be stand-alone unit operations, or combined with other operations including extrusion and melt filtration. Those utilizing sub-ambient pressures above the molten stream of recycled plastic are common.

[0138] An overall purification technology involving devolatilization was analyzed for its purification capabilities. The technology involves slightly elevated temperatures but below the initial melting point of the plastic, long residence times (> about 2 hours), and continuous reflux of purified air to provide devolatilization (as shown below in Comparative Example 4). The commercial devolatilization technology was not able to adequately remove the target contaminants. For example, the target contaminants were still well above the LOQ. In addition, the average removal efficiency was about 20%.

[0139] Extraction is the preferred overall purification method. Extraction involves the use of a purification solvent to remove overall permeable contaminants by creating a chemical potential gradient between the first plastic and the solvent. The permeable chemical contaminant removal rate will depend on the diffusivity and solubility of the contaminant in the plastic under the conditions generated in the method. For high molecular weight plastics, the diffusivity of the macromolecules indicating chemical contaminants is very low, especially in the solid state of the plastic. In addition, solubility may be limited by the high MW of the first plastic and the lack of enthalpy mixing. Therefore, the time required to remove permeable contaminants by diffusion mechanisms may be quite long and is not conducive to economically viable methods on a commercial scale. Methods to address these time scale limitations include 1) increasing the diffusivity by increasing the temperature and / or increasing the plastic relaxation by solvent swelling, 2) reducing the diffusion path length by increasing the surface area to volume ratio of the first plastic exposed to the solvent, 3) increasing the convective transport of contaminants through the plastic / solvent interface by: increasing the solubility of the contaminant in the solvent, increasing the distribution of the contaminant in the solvent relative to the plastic; increasing the convection to the plastic / solvent interface, and increasing the solvent tank relative to the plastic tank. The solubility of the bulk purification solvent in the plastic can be increased by operating the extraction at elevated pressure, particularly at, near or above the critical pressure.

[0140] Importantly, the extraction method can be expanded to large volumes at low cost. Therefore, the time required for extraction should be very short to allow for this scalability. In embodiments of the present invention, the total time for extraction is less than about 6 hours, preferably less than about 4 hours, more preferably less than about 2 hours, and even more preferably less than about 1 hour. If the extraction is completed in stages, the time for each stage can be less than this range, but the total time will still fall within these times.

[0141] The extraction may be performed above, near, at, or below the initial melting point of the first plastic. Extraction performed at, near, or above the initial melting point of the first plastic is referred to as liquid-liquid extraction. Liquid-liquid extraction is referred to as liquid / liquid because both the first plastic and the solvent are in a fluid state (not necessarily liquid, as supercritical conditions may exist). Extraction performed below the initial melting point of the first plastic is referred to as leaching extraction. Liquid-liquid extraction has the advantage of higher temperatures, which drives higher diffusion rates and greater ability to manipulate surface area exposed to the solvent compared to leaching extraction.

[0142] In an embodiment of the present invention, the temperature of the overall purification is higher than the initial melting point of the first plastic. In another embodiment of the present invention, the temperature of the overall purification is higher than the initial melting point of the first plastic, and the pressure of the overall purification is about atmospheric pressure. In another embodiment of the present invention, the temperature of the overall purification is higher than the initial melting point of the first plastic, and the pressure of the overall purification is low pressure (up to about 34atm). In another embodiment of the present invention, the temperature of the overall purification is higher than the initial melting point of the first plastic, and the pressure of the overall purification is high pressure (greater than about 34atm). In another embodiment of the present invention, the temperature of the overall purification is higher than the initial melting point of the first plastic and is equal to or higher than the critical temperature of the purification solvent, and the pressure of the overall purification is equal to or higher than the critical pressure.

[0143] The temperature may vary during the extraction process but is generally consistent within a given stage of a unit operation. The pressure may be varied to change the solubility of the solvent in the first plastic or to increase the solubility of a chemical contaminant within the solvent.

[0144] Liquid-liquid extraction can be performed in stages and combined with additional liquid-liquid extraction methods. In addition, liquid-liquid methods can be combined with leaching methods at different stages to form a given purification method. In one embodiment of the invention, the number of liquid-liquid stages is more than one. In another embodiment of the invention, the number of leaching stages is more than one. In another embodiment of the invention, the number of liquid-liquid stages is one or more, and the number of leaching stages is one or more.

[0145] Liquid-liquid extraction will include a heavy phase (also referred to as a raffinate phase) and a light phase (also referred to as an extraction phase), wherein the two phases are immiscible. In a preferred embodiment, the light phase will be represented by an overall purified rich solvent / lean plastic phase. The heavy liquid phase will be represented by a plastic-rich / lean overall purified solvent phase. Therefore, the liquid-liquid solvent should be dissolved into the plastic to form a miscible overall purified solvent / plastic heavy phase (<about 25% by weight solvent). In addition, the plastic should be slightly dissolved (<25% by weight of the first plastic) into the liquid-liquid solvent to form a miscible plastic / liquid-liquid solvent light phase. The heavy phase and the light phase will be immiscible. In the heavy phase, compared to the inherent first plastic, the contaminants will diffuse much faster, due to the relaxed state of the first plastic, due to the slight swelling / slight miscibility of the solvent in the first plastic. In addition, due to the mixing in the liquid state, the contaminants will be convectively transported closer to the surface. Ideally, the surface area between the heavy phase and the light phase will be maximized due to the combination of distributed mixing and dispersed mixing within the method. Maximum surface area content between the heavy and light phases is more easily achieved when the rheological and interfacial properties of the heavy and light phases are more closely matched. This will generally be better achieved when the liquid-liquid solvent and the first plastic are more similar and when the plastic dissolves into the solvent, as is the case for alkanes and other non-polar solvents when a polyolefin first plastic is used. The latter benefit may be offset by the reduced partitioning of contaminants in such non-polar solvents compared to the first plastic. Countercurrent and cocurrent liquid-liquid extraction apparatus and methods are well known to those skilled in the art. Assuming the rheological properties are within a matching range, such apparatus are designed to effectively distribute and disperse the light and heavy phases.

[0146] In an embodiment of the present invention, the overall purification comprises liquid-liquid extraction; and the overall purification solvent comprises a liquid-liquid extraction solvent. In another embodiment of the present invention, the liquid-liquid extraction comprises a plurality of extraction steps or stages.

[0147] In an embodiment of the present invention, less than about 25% of said first plastic dissolves in said liquid-liquid extraction solvent at said temperature of said liquid-liquid extraction and said pressure of said liquid-liquid extraction. In another embodiment of the present invention, less than about 10% of said first polymer dissolves in said liquid-liquid extraction solvent at said temperature of said liquid-liquid extraction and said pressure of said liquid-liquid extraction. In another embodiment of the present invention, less than about 5% of said first polymer dissolves in said liquid-liquid extraction solvent at said temperature of said liquid-liquid extraction and said pressure of said liquid-liquid extraction.

[0148] In an embodiment of the present invention, a two-phase system is formed in the liquid-liquid extraction solvent, the two-phase system comprising a first plastic-rich phase and a liquid-liquid extraction solvent-rich phase; and the first polymer-rich phase contains at least about 5% by weight of the liquid-liquid extraction solvent at the temperature of the liquid-liquid extraction and the pressure of the liquid-liquid extraction. In another embodiment of the present invention, a two-phase system is formed in the liquid-liquid extraction, the two-phase system comprising a first polymer-rich phase and a liquid-liquid extraction solvent-rich phase; and the first polymer-rich phase contains at least about 1% by weight of the liquid-liquid extraction solvent at the temperature of the liquid-liquid extraction and the pressure of the liquid-liquid extraction. In yet another embodiment of the present invention, a two-phase system is formed in the liquid-liquid extraction, the two-phase system comprising a first polymer-rich phase and a liquid-liquid extraction solvent-rich phase; and the first polymer-rich phase contains at least about 0.5% by weight of the liquid-liquid extraction solvent at the temperature of the liquid-liquid extraction and the pressure of the liquid-liquid extraction.

[0149] In an embodiment of the present invention, wherein the number of stages is from 1 to about 50. In another embodiment of the present invention, wherein the number of stages is five.

[0150] Although not wishing to be bound by theory, the theoretical maximum contaminant removal capacity of the extraction process is based on the thermodynamic equilibrium / partitioning of chemical contaminants between the first plastic and the solvent at the temperature and pressure of the process. Due to kinetic limitations in the extraction process, thermodynamic equilibrium may not be achieved. This is true for the complete extraction process, and for each extraction stage. A higher solvent to first plastic mass ratio will drive thermodynamics and kinetics in favor of purification, at the expense of greater solvent consumption and larger extraction process size, which equals greater cost. Therefore, for the target chemical contaminant removal efficiency, a balance must be found between these important design and operating variables. Generally, the applicant has found that the overall fresh or renewed solvent to first plastic mass ratio is preferably higher than about 5: 1, more preferably higher than about 10: 1, more preferably higher than about 15: 1, even more preferably higher than about 20: 1, and most preferably higher than about 30: 1 but less than about 100: 1. If the extraction is completed in a stepwise or continuous stage, the ratio of solvent to first plastic in each stage can be lower than the specified range, but the total solvent used in the total first plastic represented by the sum of the solvents used in all stages should be within this range. In addition, the contaminated solvent from any stage can be used "as is" as the solvent for another stage. The contaminated solvent at any point in the process may be renewed by known methods of distillation, filtration, ion exchange, etc. or a combination.

[0151] A means for increasing the effective mass transfer is by indirectly applying energy to the first plastic, such as, but not limited to, vibrations in the form of ultrasonic energy and / or microwaves.

[0152] The solvent is critical in many ways. Generally, the solvent should have a reasonably low boiling point to allow removal from the first plastic and use of distillation to renew / purify the solvent. Higher boiling point solvents can be used, but once purified, solvent regeneration and first polymer devolatilization becomes more difficult. Preferably, the solvent has a normal boiling point of <200°C, more preferably <120°C, and most preferably <90°C.

[0153] The solvent may be a hydrocarbon. The solvent may be a straight chain hydrocarbon or a branched chain hydrocarbon. The solvent may be aliphatic or aromatic. The hydrocarbon may be an alkane.

[0154] In an embodiment of the present invention, the extraction solvent is selected from the group comprising hydrocarbons. In another embodiment of the present invention, the extraction solvent is selected from the group comprising aliphatic hydrocarbons. In even another embodiment of the present invention, the extraction solvent is selected from the group comprising aromatic hydrocarbons. In even another embodiment of the present invention, the extraction solvent is selected from the group comprising alkanes.

[0155] In an embodiment of the present invention, the extraction solvent is selected from the group comprising methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, neopentane, hexane (n-hexane, isohexane and neohexene), heptane, octane or a mixture thereof. In another embodiment of the present invention, the overall purification solvent comprises critical or supercritical ethane. In another embodiment of the present invention, the overall purification solvent comprises critical or supercritical butane. In even another embodiment of the present invention, the overall purification solvent comprises supercritical pentane. In an embodiment of the present invention, the overall purification solvent comprises critical or supercritical hexane.

[0156] The solvent can be oxidized. Non-limiting examples of oxygenates are alcohols, esters, ethers, aldehydes, ketones, etc. Specific non-limiting examples include, but are not limited to, dimethyl ether (DME), ether, MEK, ethyl acetate, THF, acetone, and methanol. Polar solvents such as methylene chloride can be used. The solvent can be CO2. The solvent can be CO2 at critical or supercritical conditions. CO2 can be blended with other solvents including water to adjust solubility. The solubility of CO2 in polymers and the solubility of pollutants in CO2 can vary widely based on the temperature and pressure of CO2. Therefore, CO2 can be used to extract different pollutants at different times based on pulsing pressure within a certain pressure range.

[0157] In an embodiment of the present invention, the extraction solvent is selected from the group comprising dimethyl ether (DME), diethyl ether, MEK, ethyl acetate, THF, acetone, methanol and CO2. In another embodiment of the present invention, the extraction solvent comprises dimethyl ether. In another embodiment of the present invention, the extraction solvent comprises critical or supercritical dimethyl ether. In even another embodiment of the present invention, the extraction solvent comprises ethyl acetate. In even another embodiment of the present invention, the extraction solvent comprises THF. In even another embodiment of the present invention, the extraction solvent comprises CO2. In even another embodiment of the present invention, the extraction solvent comprises critical or supercritical CO2.

[0158] Solvents can be used as blends suitable for removing specific contaminants. In addition, different solvents or solvent blends can be used during different stages of each extraction or each type of extraction. The specific solvent selected will be affected by the type of extraction method desired.

[0159] After overall purification involving extraction, the plastic can be devolatilized to produce a purer plastic. The contaminated solvent will contain small amounts of dissolved purer plastic, extracted contaminants, and pure extraction solvent. There are many methods for recovering purer polymers and overall purification of solvents independent of extracted contaminants.

[0160] Typically, up to about 25% by weight of the first plastic can be dissolved in the extraction solvent, which complicates the recovery of the solvent and the first plastic. In particular, the low molecular weight waxes inherent to most first plastics are particularly susceptible to dissolution into the extraction solvent. These can become problems in the distillation-based recovery of the purified solvent due to the deposition of wax on the processing equipment. Methods for reducing this tendency are known. One such method is to reduce the temperature of the contaminated solvent to below the cloud point to precipitate the polymer or wax phase and then filter. Unlike the first plastic, the residual plastic or wax produced by the precipitation of the contaminated solvent may contain significant chemical contaminants and may not be used in a variety of fields.

[0161] The distillation of the contaminated overall purified solvent can be used for regenerating the solvent for reuse in various extraction operations. However, due to the high solvent volume used in the present invention, distillation may not be preferred. In addition, because the concentration of the chemical pollutants concerned in the present invention is extremely low, the concentration of these chemical pollutants in the contaminated solvent can be correspondingly low or even lower (ppb and pptr). Therefore, the preferred method for purifying the contaminated solvent is by directly removing the pollutants without having to completely volatilize the contaminated solvent. Such methods include ion exchange, adsorption / absorption methods, etc. Examples include passing the contaminated solvent through an activated carbon or alumina bed. This method can be used alone or in combination with distillation to achieve the correct purification level at the correct energy consumption. In an embodiment of the present invention, the contaminated extraction solvent is updated by an adsorption / absorption method, and can potentially include continuous or distillation at different time points when necessary.

[0162] The purer plastic may contain a small amount of solvent in the form of physical adsorption or bulk adsorption. The concentration of solvent in the purer plastic can be reduced by devolatilization techniques. In an embodiment of the present invention, the purer plastic is devolatilized to a content of <1 wt % solvent in the first plastic.

[0163] In an embodiment of the present invention, the temperature of the liquid-liquid extraction is between about the initial melting point of the first plastic and about 300°C; and the pressure of the liquid-liquid extraction is between about atmospheric pressure and about 1,000atm. In another embodiment of the present invention, the temperature of the liquid-liquid extraction is between about 150°C and about 250°C; and the pressure of the liquid-liquid extraction is between about atmospheric pressure and about 1,000atm. In even another embodiment of the present invention, the temperature of the liquid-liquid extraction is between about 150°C and about 250°C; and the pressure of the liquid-liquid extraction is between about 14atm and about 340atm. In even another embodiment of the present invention, the temperature of the liquid-liquid extraction is between about 150°C and about 240°C; and the pressure of the liquid-liquid extraction is between about 34atm and about 68atm. In even another embodiment of the present invention, the temperature of the liquid-liquid extraction is about 235°C; and the pressure of the liquid-liquid extraction is about 41atm. In even another embodiment of the present invention, said temperature of said liquid-liquid extraction is about 235° C.; said pressure of said liquid-liquid extraction is about 41 atm; and said liquid-liquid extraction solvent comprises hexane.

[0164] It was determined that the removal efficiency of liquid-liquid was significantly more effective than existing surface washing methods. For example (Example 1 and Table 8), liquid-liquid extraction with hexane removed most of the target pollutants to below LOQ, and the average removal efficiency of 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate was greater than about 70%.

[0165] In one embodiment of the present invention, the liquid-liquid extraction is carried out at about 235°C and about 41atm using a liquid-liquid extraction solvent including hexane; wherein the mass ratio of hexane to the first plastic is about 55:1 and the total extraction time in the liquid-liquid state is about 65 minutes; wherein the average removal efficiency of 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate is greater than about 70%.

[0166] In one embodiment of the present invention, the temperature of the liquid-liquid extraction is about 170°C; the pressure of the liquid-liquid extraction is about 129 atm, and the liquid-liquid extraction solvent comprises dimethyl ether. In another embodiment of the present invention, the liquid-liquid extraction is performed at about 170°C; wherein the liquid-liquid extraction is performed at a liquid-liquid extraction solvent to first plastic ratio of about 107:1, and the total extraction time is about 65 minutes; wherein the pressure of the liquid-liquid extraction is about 129 atm, and the liquid-liquid extraction solvent of the liquid-liquid extraction comprises supercritical dimethyl ether. In even another embodiment of the present invention (Table 9 of Example 2), the liquid-liquid extraction involves 5 stages using a liquid-liquid extraction solvent including dimethyl ether at about 170°C and about 41atm, wherein the mass feed ratio of dimethyl ether to the first plastic is about 22.7, 21.9, 21.0, 20.8 and 20.8 in stages 1 to 5, respectively, and the average extraction time for each stage is about 13 minutes, the total mass ratio of dimethyl ether to the first plastic is about 107:1, and the total extraction time is about 65 minutes; wherein the average removal efficiency of 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate is about 66.8%.

[0167] In an embodiment of the present invention, the liquid-liquid extraction solvent is CO 2. In an embodiment of the present invention, the liquid-liquid extraction is performed in a stirred tank; wherein the stirred tank may be staged.

[0168] VI. Surface + bulk purification

[0169] Typically, the combination of a surface purification method with an overall purification method provides a synergistic benefit for the overall removal of contamination. The surface purification method will effectively remove impermeable and permeable surface contamination, including chemical contaminants and chemical contaminant precursors. Therefore, surface purification reduces the burden of overall purification and makes it more effective. If the first plastic is seriously contaminated by surface contamination, it is preferably firstly removed by a surface purification method and then by an overall purification method to remove such contamination. Once the surface purification method removes the surface contamination, the overall purification method will remove the remaining overall permeable contamination. The only contamination that is not significantly removed by this two-step method is overall impermeable contamination, such as heavy metals intentionally added during the production of the original plastic parts. In addition, due to the larger size of the first plastic and the resulting low permeability, organotin will be difficult to remove. The latter can still be removed with extensive overall purification.

[0170] Preferred methods for surface washing have been discussed in the surface purification section. An even more preferred surface washing method is the deinking method also described in the surface purification method (Comparative Example 3). This method not only removes surface contamination, such as dirt, but also removes surface printed ink. This method is also quite effective in removing paper labels that are precursors to chemical contaminants. In this method, a first plastic having an exposed original surface area is fed into a multi-step aqueous washing process, wherein surface contamination including surface printed ink, dirt, grit, paper, adhesives, etc. is removed. The resulting material is then dried. The dried material can be further densified into pellets using extrusion including devolatilization and melt filtration. For the purposes of the present invention, the deinking method is any surface washing method, wherein the method removes surface imprints sufficient to produce a dE difference of less than about 10% between the deinked first plastic and the unprinted first plastic (dE measured using method 3 in Section IX).

[0171] For nomenclature purposes, the contaminated plastic fed to the surface purification process will be referred to as the first plastic. The resulting surface purified plastic will be referred to as the second plastic. The second plastic is fed to the bulk purification process and will be purified into a purer plastic. The surface purification method may involve multiple surface purification processes. The bulk purification method may involve multiple bulk purification processes of various types. The removal efficiency of the combined surface and bulk purification methods will be calculated based on the first plastic concentration and the associated purer plastic.

[0172] In an embodiment of the present invention, a method for producing a purer plastic from a first plastic is provided; wherein the first plastic has a concentration of contaminants; wherein the purer plastic has a concentration of contaminants; wherein the contaminants of the first plastic include at least one of the following chemical categories; dioxins, PCBs, phthalates, bisphenols and alkylphenols; wherein the method comprises 1) a surface washing method to remove surface contamination, followed by 2) liquid-liquid extraction at temperature and pressure, and using an extraction solvent; wherein the method reduces the concentration of contaminants in the first plastic to the concentration of contaminants in the purer plastic; and wherein the average value of the reduction in the concentration of contaminants from the first plastic to the purer plastic is at least about 55% or LOQ.

[0173] In an embodiment of the present invention, the extraction is performed after surface washing. In another embodiment of the present invention, the extraction is performed after surface washing, wherein the first plastic is not densified before surface washing. In another embodiment of the present invention, the extraction is performed after surface washing; wherein the first plastic is not densified before surface washing; wherein the second plastic can be densified before the extraction process.

[0174] VII.Pure plastics

[0175] The purer plastic produced by the first plastic has a lower contamination level relative to the first plastic. The purer plastic from the overall purification step can be further processed to produce pellets or other end-use materials. If pellets are needed, such steps can involve melt extrusion and then granulation. Melt extrusion can optionally include a melt filtration step and / or a devolatilization step. Melt extrusion can include additional ingredients of purer plastics, such as AO, slip agents, anti-blocking agents, TiO2, coloring agents, etc. In an embodiment of the present invention, the purer plastic has a concentration of the liquid-liquid extraction solvent less than about 1 weight %.

[0176] VIII. Examples

[0177] Comparative Example 1 - Purification of high shelf life commercial post-treatment using commercially available water washing method #1 followed by melt densification membrane

[0178] The first plastic material consisting of high-shelf commercial post-film #1 is fed into a commercially available purification process. The cleaning process consists of shredding, various water washing steps, drying and melt densification. Shredding homogenizes the material while reducing its basic size. Aqueous solution washing should effectively remove surface contamination. However, due to the low solubility of chemical contaminants in water, the ability of this method to remove a large amount of permeable contamination should be minimal. A small amount of volatile overall contamination should be removed during drying and melt densification, but overall, overall contamination should be largely unaffected. In addition, the high-shelf commercial post-film source used as the first plastic has limited chemical contamination, as demonstrated by low levels of pesticides, dioxins and phthalates. The methods disclosed in the Part IX method are analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) to analyze the types of chemical contaminants commonly present in recycled materials in the first plastic and purer plastics. After purification, the purer plastic contains slightly reduced levels of chemical contamination, as shown in Table 3. The removal efficiency of the five selected substances is as follows: For 4-tert-amylphenol, the removal efficiency is 0%. For bisphenol A, the removal efficiency is 94%. For OCDD, the removal efficiency is 78%. For PCB 118, the removal efficiency is 68%. For di-2-ethylhexyl phthalate, the removal efficiency is 22%. The average removal efficiency of the five target substances is about 52%.

[0179] Table 3

[0180] Purification of High-Care Commercial Post-Use (HCPC) Source #1 Using Commercial Water Washing Process #1

[0181]

[0182]

[0183] Comparative Example 2 - Purification of High Shelf Life Commercial Post Film #2 Using Water Wash Method #2, Followed by Melt Densification

[0184] The first plastic material consisting of high-preservation commercial post-film #2 is fed into a surface purification process available on the market to produce purer plastics. The cleaning process consists of shredding, hot water washing, drying and melt densification. As in the case of water washing process #1, the process should remove surface contamination, but the ability to remove a large amount of permeable contamination is limited. The methods disclosed in the first plastic and purer plastics were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in the part IX method, the types of chemical contaminants commonly present in recycled materials, as shown in Table 4. The high-preservation film source (first plastic) has limited chemical contamination, as demonstrated by low levels of dioxins, PCBs, phthalates and PAHs. Purer plastics contain a mixture of increased and slightly reduced chemical contamination levels. The increase in certain chemical contaminants may be due to cross-contamination from other more seriously contaminated feed streams and / or the variability of the contamination level of the current feed. The removal efficiency of the five selected substances is as follows: For 4-tert-amylphenol, the removal efficiency is 0%. For bisphenol A, the removal efficiency is 96%. For OCDD, the removal efficiency is 0%. For PCB 118, the removal efficiency is 68%. For di-2-ethylhexyl phthalate, the removal efficiency is 0%. The average removal efficiency of the five target substances is about 14%.

[0185] Table 4

[0186] Purification of High-Care Commercial Post-Use (HCPC) Source #2 Using Commercial Water Washing Process #2

[0187]

[0188] Comparative Example 3A - Purification of Commercial Post-#1 Membrane Using Commercial Deinking Process from Cadel .

[0189] The first plastic material consisting of commercial post-film #1 was fed into a purification process called deinking (http: / / cadeldeinking.com / en / ) available on the market from Cadel to produce a purer plastic. The process consists of shredding, aqueous deinking, aqueous washing / rinsing, and drying. According to patented technology, the deinking step involves elevated temperature, elevated pH, and surfactants. The various washing steps should effectively remove surface contamination. In addition, a small amount of overall permeable contamination will be removed due to the elevated temperature, which will increase the diffusion rate, and the solubility of the contaminants in water may increase due to the surfactant / pH combination. However, the overall extraction rate is expected to be lower. The first plastic introduced was determined to have 0.125% by weight of loosely bound surface contamination, compared to about 0.02% by weight of the purer plastic in the form of chips. Therefore, the cleaning process removed more than 80% of the incoming loosely bound surface contamination. After cleaning but before analyzing the first plastic for chemical contamination, the chip melt was densified at 190°C using a single screw extruder to produce pellets. The pellets were ground to a mass average diameter of 300 to 500 microns. The types of chemical contaminants commonly present in recycled materials were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in the Part IX method, as shown in Table 5. The first plastic contains a moderate level of chemical contamination, indicating that the commercial post-film lacks a high storage life cycle. For example, the dioxins such as OCDD that enter are 40 times the LOQ, which is higher than the high storage sources of Comparative Examples 1, 2 and 5 described previously. In addition, this particular source has a high level of paper contamination, which may form additional chemical contamination once remelted for densification / granulation. This particular source is particularly high in alkylphenols (about 1,000 times the LOQ), further indicating the level of chemical contamination in the recycled source. The first plastic consists of shredded films, most of which are melted together to form plastic blocks. Therefore, due to the inability to approach a completely contaminated surface, the effectiveness of the surface cleaning technology using this source is suppressed to a certain extent. After the deinking process, the purer plastic contained reduced levels of chemical contamination. The removal rates for the five selected substances were as follows: For 4-tert-amylphenol, the removal efficiency was 71%. For bisphenol A, the removal efficiency was 0%. For OCDD, the removal efficiency was 60%. For PCB 118, the removal efficiency was 0%. For di-2-ethylhexyl phthalate, the removal efficiency was 22%. The average removal efficiency for the five target substances was about 31%.

[0190] Comparative Example 3B - Purification of Post-Domestic Membrane #1 Using Commercial Deinking Process from Cadel .

[0191] The first plastic material consisting of the home post-film #1 was fed into the surface purification method of Comparative Example 3A to produce a purer plastic. Compared with about 0.003% by weight of the purer plastic, the first plastic introduced was measured to have a loosely bound surface contamination of 0.047% by weight. Therefore, the cleaning process removes more than 80% of the loosely bound surface contamination entering. Before analyzing chemical contamination, the fragment melt of the home post-film #1 was densified and granulated using an extruder. The granular material was ground to a mass average particle size of 300 microns to 500 microns. The types of chemical contaminants commonly present in recycled materials in the first plastic and purer plastics were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in the Part IX method, as shown in Table 5. The first plastic contains extremely high levels of chemical contamination, including significant dirt. For example, the pesticide piperonyl butoxide was approximately 7 times the LOQ; alkylphenol ethoxylates were approximately 1,000 times the LOQ; and dioxins and phthalates were approximately 300 times the LOQ. Purer plastics contain reduced levels of chemical contamination. Note: Despite using the same cleaning process, the difference in removal efficacy between Comparative Example 3A and Comparative Example 3B may be due to 1). differences in surface area exposed by the cleaning process, 2). differences in the distribution of chemical contaminants on the surface and within the bulk, and 3). inherent variability of chemical contaminants within the sample and variability in the measurement technique. The removal efficiencies for the five selected substances were as follows: For 4-tert-amylphenol, the removal efficiency was 38%. For bisphenol A, the removal efficiency was 92%. For OCDD, the removal efficiency was 21%. For PCB 118, the removal efficiency was 0%. For di-2-ethylhexyl phthalate, the removal efficiency was 73%. The average removal efficiency for the five target substances was approximately 45%.

[0192] Table 5

[0193] Purification of Post-commercial (PC) Source #1 and Post-domestic (PH) Source #1 using commercial deinking

[0194]

[0195]

[0196] Comparative Example 4 - Purification of High-Performance Commercial Post-#3 Membrane Using Commercial Deodorization Method

[0197] A first plastic material consisting of a high-shelf commercial post-film #3 was fed into the deodorization technology. The method involves exposing the granular feed to moderate temperatures and continuous air flushing. Therefore, the cleaning technology mainly removes volatile surface and bulk contamination. However, most of the chemical contaminants associated with controlled end markets are highly non-volatile. The types of chemical contaminants commonly present in recycled materials in the first plastic and purer plastics were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the methods disclosed in Part IX Method, as shown in Table 6. High-shelf film source #3 has limited chemical contamination, as demonstrated by low levels of dioxins, PCBs, phthalates, and PAHs. Purer plastics contain slightly reduced levels of chemical contamination. The removal rates of the five selected substances are as follows: For 4-tert-amylphenol, the removal efficiency is 88%. For bisphenol A, the removal efficiency is 96%. For OCDD, the removal efficiency is 20%. For PCB 118, the removal efficiency is 0%. For di-2-ethylhexyl phthalate, the removal efficiency was 0%. The average removal efficiency of the five target substances was about 41%.

[0198] Table 6

[0199] Using Commercial Deodorizer to Purify High-Care Commercial Post-Use (HCPC) Sources #3

[0200]

[0201]

[0202] Typically, established processes for purifying / cleaning film and other plastic wastes, including washing, deinking, and devolatilization, currently do not adequately remove chemical contaminants, especially in high-care sources. Even with high-care sources, chemical contamination is still present and not completely removed, which may limit end-use for certain consumers. Thus, there is an unmet need for cleaning technologies that can more completely remove chemical contamination sufficient for use in highly contaminated sources and for any market requiring purer recycled materials.

[0203] Example 1 - Batch liquid / liquid extraction of granular commercial post-membrane #2 using liquid / liquid extraction in critical hexane For overall purification

[0204] A first plastic material consisting of commercial post-membrane #2 in pellet form was fed into a laboratory-scale batch liquid / liquid extraction process. The first plastic was in the form of approximately 4 mm spherical pellets with a surface area to volume ratio of approximately 1.5 mm-1. The first plastic was subjected to an overall purification step of liquid-liquid extraction as follows (at Phasex Corporation, 125 Flagship Drive, North Andover, MA). A 7L autoclave was charged with approximately 280 g of pellets of the first plastic; the autoclave was then evacuated and purged with N2 three times, and heated to an internal temperature of approximately 235°C and a pressure of approximately 41 atm; then, approximately 3,100 g of hexanes (Hexanes ACS; Catalog No.: 35900ACS; >98.5% hexane isomers and methylcyclopentane; Pharmco by Greenfield Global, Inc.; Brookfield, CT) was added to the autoclave. At those conditions, the hexane is at critical conditions (the critical temperature of n-hexane is 235°C, and the pressure is 31 atm). After the autoclave reaches the above temperature and pressure, mechanical stirring is started at about 680rpm and lasts for about 10 minutes. Under those conditions, the polyethylene of the first plastic and hexane forms a two-phase system, with a light phase (extract) of low-concentration polyethylene in hexane and a heavy phase (raffinate) of high-concentration polyethylene in hexane. Then, stirring stops for about 10min, the raffinate phase settles, the extraction phase floats on the top, and the hexane stream of about 3,100 grams of fresh hexane is added to the reactor in such a way that hexane is removed from the stage 1 of liquid-liquid extraction. This step is repeated 4 more times, and the material (i.e., raffinate phase) remaining after 5 extraction steps in the autoclave is collected, devolatilized and solidified to produce purer plastics. The total ratio of hexane to the mass of the first plastic is 55:1, and the total extraction time is about 100 minutes, but only about 65 minutes is in the best mass transfer state of stirring. In a commercial liquid-liquid countercurrent continuous extractor, the relevant time scale is about 65 minutes. Therefore, the actual extraction time is close to about 65 minutes. The purer plastic after devolatilization had a mass of about 230 g, with a total extracted mass of about 50 g (18 wt %), which included the first plastic contaminant and the dissolved first plastic. The above method was used to simulate a continuous and large-scale liquid-liquid extraction known in the art. The first plastic and the purer plastic were analyzed for types of chemical contaminants commonly found in recycled materials by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the methods disclosed in Part IX Method, as shown in Table 7. Prior to analyzing the purer plastic, it was ground to a mass average particle size of about 1 mm. The first plastic contained a moderate level of chemical contamination.For example, the pesticide piperonyl butoxide was about 12 times the LOQ; the alkylphenol isononylphenol was about 170 times the LOQ, bisphenol A was about 320 times the LOQ; OCDD was about 17 times the LOQ; PCB 118 was about 30 times the LOQ, and PAH was 50 to 100 times the LOQ. The purer plastics contained significantly reduced levels of chemical contamination, as shown in Table 10. The vast majority of chemical contaminants were extensively removed. Pesticides, alkylphenol ethoxylates, bisphenol A, and most dioxins / furans and PCBs were removed below the LOQ. Even when not reduced below the LOQ, most were significantly reduced. At least one contaminant from the categories of pesticides, alkylphenol ethoxylates, bisphenol A, dioxins, PCBs, phthalates, and PAHs was removed with >99% efficiency. For the contaminant 4-tert-amylphenol, the removal efficiency was 72%. For the contaminant bisphenol A, the removal efficiency was 99.7%. For the contaminant OCDD, the removal efficiency was 88%. For PCB 118, the removal efficiency was 88%. For di-2-ethylhexyl phthalate, the removal efficiency was not calculated due to external contamination during the sampling process. However, a similar removal rate of dibutyl phthalate was >89%. The minimum removal capacity for the contaminants, 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate was 72%. Only organic tin was not significantly removed by extraction due to the low diffusion rate in molten PE and the availability in the initial integral first plastic. If a high-preservation film source had been used, it is likely that most (if not all) of the chemical contaminants would have been completely removed.

[0205] The removal efficiencies of the five selected substances were as follows: For 4-tert-amylphenol, the removal efficiency was 72%. For bisphenol A, the removal efficiency was 99.7%. For OCDD, the removal efficiency was 88%. For PCB 118, the removal efficiency was 88%. For di-2-ethylhexyl phthalate, the removal efficiency was 0%. The average removal efficiency of the five target substances was > about 70%.

[0206] Table 7

[0207] Liquid-Liquid Extraction of Commercial Post-(PC) Membrane #2 Using Supercritical Hexane

[0208]

[0209]

[0210] Example 2 - Overall purification of membrane #1 after domestic use using batch liquid-liquid extraction using DME .

[0211] The home use back film #1 is chopped, melt densified into pellets using a single screw extruder, and then ground to a particle size of about 1mm. The resulting ground material is the first plastic. Therefore, the first plastic has a surface area to volume ratio of 6mm-1. The overall purification step of liquid-liquid extraction of the first plastic is performed as follows (at Phasex Corporation, 125 Flagship Drive, North Andover, MA). About 152g of the pellets of the first plastic are loaded into a 7L autoclave. Then, the autoclave is evacuated and purged with N2 three times, and heated to reach an internal temperature of about 170°C and a pressure of about 129atm. 3,500 grams of DME are added. After the autoclave reaches the above temperature and pressure, mechanical stirring is started at about 680rpm and lasts for about 10 minutes. At those conditions, the polyethylene of the first plastic and DME forms a two-phase system, with a light phase (extract) having a low concentration of polyethylene in DME and a heavy phase (raffinate) having a high concentration of polyethylene in DME. Then, stop stirring for about 10min, the raffinate phase settles, the extraction phase floats on the top, and the DME stream of about 3,300 grams of DME is added to remove the contaminated DME from stage 1. Start stirring and allow it to continue for 10 minutes. Repeat these stages a total of 5 times. Therefore, for a solvent ratio of about 111:1 to the first plastic, the total solvent used is about 17kg, and the total reaction time is about 65 minutes, similar to the liquid-liquid hexane example. The residue from the contaminated solvent is about 3.5 grams, and the mass of the purer plastic is about 148.5g. The material (i.e., the raffinate phase) remaining after 5 extraction steps in the autoclave is collected, devolatilized and solidified to produce a purer plastic. The types of chemical pollutants commonly present in the recycled materials in the first plastic and purer plastics are analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in the part IX method, as shown in Table 8. Before analyzing the purer plastics, they were ground to a mass average particle size of approximately 1 mm.

[0212] At least one contaminant from the categories of pesticides, alkylphenol ethoxylates, bisphenol A, dioxins, PCBs, phthalates, and PAHs was removed with an efficiency of 97.8%. For the contaminant 4-tert-amylphenol, the removal efficiency was 55%. For the contaminant bisphenol A, the removal efficiency was 97.6%. For the contaminant OCDD, the removal efficiency was 87.7%. For PCB 118, the removal efficiency was 97.6%. For di-2-ethylhexyl phthalate, the removal efficiency was about 0%. The average removal capacity for the contaminants 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate was about 67%.

[0213] Table 8

[0214] Liquid-Liquid Extraction of Commercial Post-(PC) Membrane #3 Using DME

[0215]

[0216] Example 3 - Purification of heavily fouled regenerated membrane using surface washing followed by liquid / liquid extraction with hexane

[0217] A method for producing purer plastics from recycled film; wherein a recycled film having a mass average surface area to volume ratio greater than about 40 mm-1 is fed to a surface washing step, the surface washing step comprising an aqueous surface washing step while applying vigorous mechanical agitation for about 30 minutes, wherein loosely bound surface contaminants are removed by greater than about 80%; wherein the surface washed plastic is fed to a melt extruder, the melt extruder delivers a molten and high pressure first plastic to an extraction process, the extraction process involving a continuous countercurrent liquid-liquid extractor operated at a temperature of about 235°C and a pressure of about 41 atm; wherein the extraction uses a liquid-liquid extraction solvent; wherein the liquid-liquid extraction solvent is hexane; wherein the mass ratio of hexane to surface washed plastic is greater than about 30:1; wherein the extraction method involves an extraction time; wherein the extraction time is less than about 1 hour; wherein the average removal capacity of the contaminants, 4-tert-amylphenol, bisphenol A, OCDD, PCB 118 and di-2-ethylhexyl phthalate is greater than about 55%.

[0218] IX. Methods

[0219] 1. The following methods were used to analyze and measure various chemical pollutants. Pesticides: EN 15662:2018-07 Modular QuEChERS method was applied. For alkylphenol ethoxylates, alkylphenols, and bisphenols, the following techniques were applied: the samples were cut, homogenized, and weighed; then, an internal standard (deuterated bisphenol A) was added, the samples were then extracted with hexane at room temperature, MSTFA (N-methyl-N-(trimethylsilyl)trifluoroacetamide) was added for derivatization, and the pollutant levels were determined by GC-MSD. For dioxins, furans, and PCBs: ISO / IEC 17025:2005 method was applied. The sample was cut into small pieces, 13C / 12C labeled PCDD / F internal standard was added to an aliquot of the sample material, extracted and matrix destroyed with hexane and H2SO4 for 1 hour, re-extracted with hexane (3 times for 30 min), multi-step chromatographic cleaning was applied, 13C / 12C labeled PCDD / F recovery standard was added to the measurement solution, and quantification was performed by internal labeled PCDD / F standard (isotope dilution technique and internal standard technique). For organotins: The method follows the EDANA protocol (WSP 351). More specifically, the sample was extracted with ethanol containing sodium diethyldithiocarbamate solution, alkylated with sodium tetraethylborate, and transferred to the organic phase by extraction with hexane. Then, the tetrasubstituted organotin compounds were separated by using capillary gas chromatography, demonstrated with AED or MS as detector. GC-ICP-MS was used as the detector system for organometallic analysis. For phthalates: The sample was cut, homogenized and weighed. Then an internal standard was used and extracted with hexane at room temperature. The extracted phthalates were then identified and quantified by GC-MSD. For PAH: The samples were cut, homogenized and weighed. Then, an internal standard of deuterated PAH was added and the samples were extracted with hexane. The extracted PAH was purified with silica gel, concentrated and then characterized by GC-MSD.

[0220] 2. The amount of loosely bound surface contamination is determined by the following method: About 20 grams of plastic is added to a 1000 mL round bottom flask. About 600 mL of distilled water is added to the 1000 mL round bottom flask. The round bottom flask is capped and then shaken vigorously for about 60 seconds. The water is decanted from the flask. About 600 mL of additional distilled water is added to the 1000 mL flask and then immediately decanted, leaving the original first plastic with a small amount of water. The first plastic is removed from the round bottom and allowed to dry overnight in a convection oven at 60°C. The % change in mass of the plastic is the amount of loosely bound surface contamination.

[0221] 3. Obtain color measurements using a Minolta spectrophotometer, model CM580d. The "white" portion of the Leneta card is used as a common background and as a reference point for ΔE calculations. ΔE is the color difference (dE or ΔE) between the sample color and the reference color. Color measurements are performed using a D65 light source and a 10° observer. A minimum of three measurements are performed for each sample in the compressed thermoplastic starch composition sample. The L, a, and b values ​​are averaged and reported together with the ΔE value. The ΔE value of a pure white Leneta card is zero, and a positive deviation from zero indicates an increase in discoloration. Those skilled in the art will know how to calculate the ΔE value.

[0222] The foregoing description has been given for clearness of understanding only, and no unnecessary limitations are to be understood therefrom, as modifications within the scope of the invention will be apparent to one skilled in the art.

[0223] The dimensions and values ​​disclosed herein are not to be understood as being strictly limited to the exact numerical values ​​cited. Instead, unless otherwise indicated, each such dimension is intended to represent the stated value and a functionally equivalent range around that value. For example, a dimension disclosed as "40 mm" is intended to mean "about 40 mm".

[0224] Unless expressly excluded or otherwise limited, each document cited herein, including any cross-referenced or related patent or application, is incorporated herein by reference in its entirety. Citation of any document is not an admission that it is prior art to any of the present invention disclosed or claimed herein, or that it, by itself or in combination with any one or more references, proposes, suggests, or discloses any such invention. In addition, to the extent that any meaning or definition of a term in this invention conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this invention shall govern.

[0225] Although specific embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications may be made without departing from the spirit and scope of the present invention. Therefore, it is intended that all such changes and modifications within the scope of the present invention be covered in the appended claims.

Claims

1. A method of extracting contaminants from a first plastic to produce a purer plastic, the method comprising: a. providing a first plastic comprising individual contaminants, each individual contaminant having a certain concentration; b. extracting the individual contaminants from the first plastic in an extraction stage using an extraction solvent comprising hexane or dimethyl ether at a temperature and pressure to produce a purer plastic comprising the individual contaminants each having a concentration, wherein the total extraction time is less than 6 hours; wherein the extraction is liquid / liquid, wherein the temperature is above the initial melting point of the first plastic, and both the first plastic and the extraction solvent are in a fluid state; wherein the extraction stages are performed at a total extraction solvent to first plastic mass ratio, wherein the total extraction solvent to first plastic mass ratio is greater than 5:1 and less than 100:1 in all stages; wherein The pressure is between atmospheric pressure and 1,000 atm; wherein the first plastic individual contaminant includes at least one of 4-tert-amylphenol, bisphenol A, OCDD, PCB 118 or 2-ethylhexyl phthalate; wherein the concentration of each individual contaminant in the purer plastic is reduced compared to the concentration of each individual contaminant in the first plastic; and wherein the average value of the reduction in the concentration of the first plastic contaminant relative to the purer plastic contaminant is at least 55% or LOQ; and wherein at the temperature and pressure of the liquid-liquid extraction, less than 25 weight percent of the first plastic dissolves in the extraction solvent to form a miscible plastic / extraction solvent light phase, and less than 25 weight percent of the extraction solvent dissolves into the plastic to form a miscible, integrally purified extraction solvent / plastic heavy phase. 2 . The method according to claim 1 , wherein the number of said stages is between 1 and 50. 3 .

3. The method of claim 1, wherein the first plastic is a recycled plastic comprising at least one of post-industrial or post-consumer film.

4. The method of claim 1 , wherein the first plastic is surface washed in a non-compacted state by one or more surface washing methods prior to extraction, and wherein the one or more surface washing methods result in a greater than 80% reduction in loosely bound surface contamination; wherein the first plastic has a surface area to volume ratio greater than 1 mm-1 prior to surface washing.

5. The method according to claim 4, wherein the surface washing method is of the deinking type; wherein The surface washing method results in a percent change in ΔE between the de-inked first plastic and the first plastic without surface printed ink of less than 10%.

6. A method according to claim 1, wherein the extraction solvent is purified after the extraction or one or more extraction stages to allow reuse in the extraction process by a solvent purification process; wherein the solvent purification process comprises at least one stage of physical adsorption or absorption of chemical contaminants from the contaminated extraction solvent.

7. The method of claim 1, wherein the first plastic is a recycled plastic, including but not limited to post-industrial or post-consumer film; wherein the post-consumer film includes post-commercial film and / or post-domestic film.

8. The method of claim 1, wherein the first plastic comprises polyolefins and mixtures thereof.

9. The method of claim 1, wherein the first plastic is a film, a rigid material, a fiber, a nonwoven, and mixtures thereof.

10. The method of claim 1, wherein the extraction solvent is a mixture of organic solvents.

11. The method according to claim 10, wherein the organic solvent is at least one of methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, neopentane, heptane, octane or a mixture thereof.

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