Reduce surface and overall contamination in plastics

Abstract

The present invention generally relates to a method for 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 purified integrally or on the surface and integrally, wherein the total contamination present in the first plastic is reduced. The resulting purer plastic is pure enough to potentially be used in demanding applications. Background Art

[0002] Synthetic plastics are ubiquitous in daily life due to their relatively low production cost and well-balanced material properties. They are widely used in various applications such as packaging, motor vehicle parts, medical devices, and consumer goods. To meet the high requirements of these applications, hundreds of millions of tons of synthetic plastics are produced globally every year. The vast majority of synthetic plastics are produced from increasingly scarce fossil resources such as oil and gas. Additionally, manufacturing synthetic plastics from fossil sources results in greenhouse gas (GHG), mainly CO2 emissions into the atmosphere.

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

[0004] Plastic recycling has become a solution to mitigate the problems associated with poor plastic waste management. 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 increasing due to increased awareness among consumers, businesses, and industrial manufacturers, as well as due to regulatory frameworks. Most recycled materials, including plastics (except films), are mixed into a single stream, which is collected and processed by a materials recycling facility (MRF). At the MRF, the materials are sorted, washed, and packaged (e.g., into bales) for resale. Plastics can be separated into individual materials, such as single streams of high-density polyethylene (HDPE) and poly(ethylene terephthalate) (PET), or mixed streams of other common plastics (such as polypropylene (PP), low-density polyethylene (LDPE), polyvinyl chloride (PVC), polystyrene (PS), polycarbonate (PC), and polyamide (PA)). The single stream or mixed stream can then be further sorted, washed, and reprocessed in a plastic recycling facility (PRF) into pellets suitable for reuse in plastic processing such as extrusion blow molding, profile extrusion, injection molding, and film making.

[0005] However, the utilization of these recycled plastics is currently limited due to contamination, which makes the plastics less valuable compared to virgin plastics. The key to increasing the recycling rate and reducing CO2 emissions and plastic pollution is to reduce contamination to a level that allows for more widespread utilization in a greater number of end markets, especially those involving demanding applications that require low contamination.

[0006] Films are a special case of recycled plastics and are mainly polyolefins in composition. Films present unique challenges for recycling that have not been resolved. The recycled film supply stream can be divided into two general categories: 1) pre-consumer recycled films, which include in-plant scrap / trimmings that can be reused in the same process in which the film is produced and post-industrial recycled (PIR) films, which are films produced from in-plant scrap that is not used in the same process in which it is generated; 2) post-consumer recycled (PCR) films, including post-commercial recycled films, which are films that have been used in commerce but not directly by household consumers (e.g., store overwrap, pallet wrap, wholesale bags, furniture wrap, agricultural films, etc.), and post-household recycled films, which are films that have been used in commerce directly by household consumers (e.g., retail bags, retail food packaging, outer packaging for diapers and hygiene products, garbage bags, etc.). Post-industrial film scrap for recycling is collected on a plant-by-plant basis in controlled end markets and may or may not (or need) involve significant cleaning steps prior to recycling. Post-commercial films are collected at the point of sale and transported to various PRFs dedicated to films for various cleaning operations and ultimately distribution to end markets. In the United States, post-household films are mainly collected in store recycling programs, where the end consumer returns the film to collection bins at local stores. Film-based PRFs collect film scrap and transport it to end markets after sorting and cleaning. Due to contamination, the use of recycled film materials is very limited. Films are more contaminated than other forms because of their higher surface area to volume ratio, which presents a greater opportunity for external contamination. Currently, most film-based recycled plastics are downcycled into non-circular and limited-size markets such as plastic lumber. As the collection of film-based scrap grows, demand for end markets other than plastic lumber is essential. Ideally, film-based scrap will ultimately find reuse in film-based applications, thus ensuring continuous recycling.

[0007] The end markets cannot grow unless contamination is significantly reduced. Given the large amount of film used in demanding applications, 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 crucial for achieving circularity and reducing CO2 emissions and plastic pollution. Plastic pollution is even more of a problem for films given the large surface area per use and the mobility of waste in the environment via air and water.

[0008] Although contamination is a problem for all end market applications, demanding applications have even more stringent requirements, especially for certain chemical contaminants. Depending on the chemical structure of the contaminant, the relevant chemical contaminants are divided into various chemical classes. Non-limiting examples of contaminants in these chemical classes are heavy metals, pesticides, dioxins, furans, polychlorinated biphenyls (PCBs), phthalates, polycyclic aromatic hydrocarbons (PAHs), organotin, bisphenols, isothiazolines, glyphosate, alkylphenols, alkylphenol ethoxylates, aromatic amines, and flame retardants. In addition, the target levels of these contaminants can be extremely low. For example, the target levels can be on the order of parts per million (ppm), parts per billion (ppb), and parts per trillion (ppt), where the initially contaminated plastics can contain levels 1,000 times the target levels. Therefore, a 1,000-fold reduction in chemical contamination is typically required.

[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 S.M. Al-Salem, P. et al., Waste Management, 29(10)(2009), 2625 - 2643. Mechanical recycling of rigid plastics typically involves some form of surface washing, followed by drying and melt densification. The melt densification step typically includes melt filtration and devolatilization. For film-based materials, there are dry and wet methods. In the dry method, a controlled film stream is typically shredded, dried, and then melt-extruded into its final form. Melt filtration and devolatilization are typically part of the extrusion step. In the wet method, a controlled film stream is typically shredded, washed in one or more aqueous solutions, dried, and then melt-extruded into its final form. Melt filtration and devolatilization are typically part of the extrusion step. The above methods are generally acceptable for 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 No. 10,022,725 discloses a mechanical recycling method for cleaning linear low-density polyethylene (LLDPE) / LDPE films for recycling. The patent also discloses steps of shredding, a first water washing step, a second pulverization step involving wet grinding, one or more friction washing steps using hot water in at least one step, a drying or multiple drying steps, and a compaction step. This method may be quite effective in removing some 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 No. 9,616,595 discloses a mechanical recycling method for deinking surface-printed plastic films. The patent also discloses steps of grinding, ink removal step, general washing, cleaning solution recovery, recovered pigment, and drying. The ink removal step involves using an aqueous cleaning fluid with a high pH and a selective detergent such as dodecyl sulfate and high turbulence. This method claims the ability to remove surface-printed ink, which may cause chemical contamination after heating during the recycling process. Due to the limited solubility of bulk contaminants in the aqueous washing medium and / or the limited diffusion rate of bulk contaminants in the plastic, this method will have a limited ability to remove bulk contaminants.

[0012] To overcome the fundamental limitations of mechanical recycling, many methods have been developed to purify contaminated plastics. Most of these methods use solvents to purify and refine plastics. U.S. Patent No. 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 No. 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 for a specific residence time. The starting material is porous granules, and the extraction conditions are below the melting temperature to enable conveyance in the method. The patent also discloses increasing the temperature of the solvent (or a second solvent) before filtration to dissolve the polymer. Additionally, the patent discloses the use of shear flow for precipitating polypropylene from the solution. The polypropylene blend described in the patent contains up to 5.6 wt% of polyethylene contaminants.

[0014] European Patent Application 849,312 discloses a method for obtaining a purer polyolefin from a polyolefin-containing plastic mixture or polyolefin-containing waste. The patent application discloses extracting a polyolefin mixture or waste with a hydrocarbon fraction of gasoline fuel or 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 filled leaching clay and / or activated carbon to remove foreign components from the solution. Additionally, 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 vacuo or precipitating the polyolefin by passing an air stream through it, 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 5,198,471 discloses a method for separating a polymer from a physically mixed solid mixture containing a plurality of polymers (such as 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 filtration of the insoluble polymer component.

[0016] U.S. Patent 5,233,021 discloses a method for extracting pure polymer components from a multi-component structure (such as 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 5,198,471, this patent only discloses filtration of the undissolved components.

[0017] U.S. Patent 5,739,270 discloses a method and apparatus for continuously separating the polymer components of a plastic from the contaminants and other components of the plastic using a cosolvent and a working fluid. The cosolvent at least partially dissolves the polymer, and the 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 the step of filtering the thermoplastic cosolvent (with or without the working fluid) to remove particulate contaminants (such as glass particles).

[0018] U.S. Patent 5,368,796 discloses a method for surface cleaning of polyethylene films. The patent also discloses the following steps: shredding, a first surface washing step (involving boiling solvent at a temperature below the melting temperature of polyethylene and at or near ambient pressure while applying vigorous mechanical agitation for 30 min to wipe off the ink), a second surface washing step (involving fresh solvent below the melting temperature of polyethylene while applying vigorous mechanical agitation for 30 min), a third surface washing step (involving solvent below the melting temperature of polyethylene while applying vigorous mechanical agitation for 30 to 60 min, and devolatilization), and melt densification. Optionally, the method may include a water washing step prior to treatment with solvent to remove surface dirt. The patent also discloses that solvent washing effects extraction, where the solvent does not dissolve the polymer. However, a small amount of wax, typically <1 wt%, may be removed. The solvent washing and extraction steps are further disclosed as being carried out at the boiling point of the solvent, which is chosen to be below the softening point of polyethylene to avoid agglomeration. The above method focuses on the removal of surface printed 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 method that involves granulating to form plastic fragments, surface washing with supercritical CO2, surface washing and extraction with a high boiling point solvent or solvent mixture (such as limonene and ethylene lactate), 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 fragment feed material is agitated with the solvent and the shape of the fragments is maintained. Additionally, it is disclosed that the recovered material remains in fragments, meaning 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 recycled polypropylene with a first fluid solvent having a standard boiling point below 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 recycled polypropylene; dissolving the extracted recycled polypropylene in a solvent selected from the group consisting of the first fluid solvent, a second fluid solvent, and mixtures 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; sedimenting the first solution comprising polypropylene, at least one dissolved contaminant, and at least one suspended contaminant 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 second solution comprising polypropylene, at least one dissolved contaminant, and less of 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 comprising purer polypropylene, at least one dissolved contaminant, and even less of at least one suspended contaminant; and separating the purer polypropylene from the third solution; and wherein the second fluid solvent has the same or different chemical composition as the first fluid solvent. The above method is well-suited for removing contaminants. However, the ability to dissolve, sediment, and filter plastics is very difficult and may not be feasible or practical for plastics having a high molecular weight (MW), such as those used in membranes and blow molded containers. In addition, the above method does not mention removing surface contaminants prior to extraction and dissolution, thus increasing the burden of such disclosed methods, particularly filtration.

[0021] In summary, the solvent-based method for purifying contaminated plastics as described above does not solve the problem of adequately and effectively removing surface and bulk contaminants from plastics such that they can be used in sensitive packaging and product applications, particularly in membrane and rigid applications involving high MW plastics. Accordingly, there is a need for a method that: 1) produces purer plastics, i.e., plastics free of significant amounts of contamination; 2) is relatively simple in terms of the number of unit operations; and 3) can be used with high MW plastics, such as those derived from membrane and rigid applications. SUMMARY OF THE INVENTION

[0022] A method for extracting contaminants from a first plastic to produce a purer plastic is provided. The method includes providing a first plastic containing individual contaminants, each individual contaminant having a certain concentration; using a leaching solvent in an extraction stage at a certain temperature and pressure to extract the individual contaminants from the first plastic for a period of time and each stage for a period of time to produce a purer plastic containing the individual contaminants each having a certain concentration; wherein the extraction is packed leaching, wherein the temperature is lower than the initial melting point of the first plastic; wherein the extraction stage is carried out at a mass ratio of the leaching solvent to the first plastic; wherein the mass ratio of the leaching solvent to the first plastic at each stage and any time point is less than about 5:1; wherein the pressure is between about atmospheric pressure and 1,000 atm; wherein the first plastic individual contaminants include at least one of alkylphenols, bisphenols, dioxins, PCBs, and phthalates; 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 reduction of the concentration of the first plastic contaminants relative to the reduced concentration of the purer plastic contaminants 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. For the purposes of the present invention, the terms "polymer" and "plastic" may be 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-consumer plastic, including films, fibers, nonwovens, and rigid packaging.

[0026] As used herein, the term "recycled plastic" refers to recycled plastic that has been converted into a form for use in manufacturing products and packaging that are blended with virgin plastic or with itself. Recycled plastic can be purer than recycled plastic or can be the same except in form.

[0027] As used herein, the term "first plastic" refers to plastic that is fed into a purification process and has a level of contamination that can include both surface and bulk contamination. Non-limiting examples of the first plastic are recycled films and recycled HDPE bottles.

[0028] As used herein, the term "purer plastic" refers to plastic produced from the first plastic by a purification method. The purer plastic generally has a lower level of contamination than the first plastic.

[0029] As used herein, the term "first-life plastics" refers to virgin plastics that have not been used for any purpose in their polymeric form.

[0030] As used herein, the term "contaminant" refers to any unwanted material on or in the plastic. The term "chemical contaminant" refers to any unwanted chemical substance on the surface of or within the body of the plastic and includes the molecular or elemental composition of the contaminant. Depending on the context, the terms may be used interchangeably. For example, paper contaminants include cellulose. Thus, cellulose is a chemical contaminant within paper contaminants. As used herein, the term "contamination" refers to the sum total of all contaminants, and the term "chemical contamination" refers to the sum total of all chemical contaminants. Chemical contaminants are grouped by category, which includes chemical contaminants having similar chemical structures. For example, As, Hg, and Cr are chemical contaminants within the "heavy metals" category. Each contaminant may have different chemical properties, such as solubility and diffusivity in the plastic, as well as target levels depending on concentration and end-use market.

[0031] As used herein, the term "surface contaminant" refers to contaminants on the surface of the plastic. Similarly, the term "surface chemical contaminant" refers to the molecular or elemental composition of surface contaminants. 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. Generally, surface contaminants will have a surface area embedded in the plastic of less than about 80%.

[0032] As used herein, the term "bulk contaminant" refers to contaminants within the bulk of the plastic. Similarly, the term "bulk chemical contaminant" refers to the molecular or elemental composition of bulk contaminants. Generally, bulk contaminants will have a surface area embedded in the plastic of more than about 80%.

[0033] As used herein, the terms "surface contamination" and "surface chemical contamination" refer to the sum total of all surface contaminants and all surface chemical contaminants, respectively.

[0034] As used herein, the terms "bulk contamination" and "bulk chemical contamination" refer to the sum total of all bulk contaminants and all bulk chemical contaminants, respectively.

[0035] 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.

[0036] As used herein, the term "permeable contaminant" refers to chemical contaminants that are soluble and diffusible in the plastic. Non-limiting examples of permeable contaminants are formaldehyde, bisphenol A, and naphthalene.

[0037] As used herein, the term "impermeable contaminant" refers to chemical contaminants that are insoluble or non-diffusive 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).

[0038] 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. If described in molecular or elemental terms, the sum of all permeable and impermeable contaminants is "chemical contaminants", or if described in general terms (such as cellulose and paper), it is simply "contaminants".

[0039] As used herein, the term "intentional contaminant" refers to contaminants 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. 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" is the sum of all intentional contaminants, and the term "intentional chemical contamination" is the intentional contamination described by its chemical composition.

[0040] As used herein, the surface area to volume ratio of plastics is calculated as follows: for objects that are typically spherical, such as pellets, ground pellets, micronized pellets, etc., the surface area to volume ratio is calculated by 3 / r; where r is the mass average radius. For objects that are typically flat and thin, such as films, the surface area to volume ratio is calculated by 2 / t; where t is the mass average thickness. For objects that are typically long and columnar, such as fibers, the surface area to volume ratio is calculated by 2 / r; where r is the mass average radius.

[0041] As used herein, the term "unintentional contaminant" refers to any contaminant that is not intentionally added. Examples include dirt and cross-contamination that are 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" is the sum of all unintentional contaminants, and the term "unintentional chemical contamination" is the unintentional contamination described by its chemical composition.

[0042] As used herein, the term "densification" 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 the wetting fluid is made inaccessible. The method of producing densified materials is called densification.

[0043] As used herein, the term "melt densification" refers to densification carried out at, near, or above the initial melting point of the plastic. Non-limiting methods of melt densification include melt extrusion and agglomeration using equipment such as Herbold HV series plastic compactors.

[0044] As used herein, the term "initial melting point" refers to the peak melting point (the highest endothermic peak on the zero slope baseline) of a plastic as measured using differential scanning calorimetry (DSC). For the purposes of this invention, the terms "initial melting point", "melting point", "melting temperature", and "initial melting temperature" may be used interchangeably. For amorphous materials and / or materials lacking distinct melting points, the defined temperature will be the approximate softening point of the material, which can be best characterized by the glass transition temperature. Those skilled in the art will understand the appropriateness of the criteria for non-semicrystalline materials.

[0045] As used herein, the term "hexane" refers to a blend of hexane isomers such as n-hexane (at least 45 volume %, and typically about 53 volume %), isohexane (2-methylpentane, 3-methylpentane, and 2,3-dimethylbutane), and neohexane (2,2-dimethylbutane).

[0046] As used herein, the term "quantitation limit" or "LOQ" refers to the lower limit of detection of a given chemical contaminant as determined by the analytical methods disclosed in Part 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 methods listed in Part IX.

[0047] As used herein, the term "ppm" refers to parts per million, "ppb" refers to parts per billion, and "pptr" refers to parts per trillion.

[0048] II. First Plastic

[0049] When first produced at resin suppliers such as Dow, Nova, ExxonMobil, etc., plastics are substantially free of contamination (virgin plastics). However, during the life cycle of plastics, contamination is introduced, either intentionally or inadvertently.

[0050] 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 the 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. Additionally, unintentional contamination can be generated by reactions involving intentional contaminants, such as the oxidation of paper labels to dioxins, the degradation of adhesives or printing binders, etc. Most of the latter occur during the melt densification method used in the recycling process. Furthermore, during the melt processing steps (such as those for the original packaging or product manufacturing and / or the recycling of the latter), the oxidation of plastics will produce unintentional contamination, such as gels. Additionally, unintentional contamination may be caused by interaction with the product. For example, packaging materials containing cleaning mixtures (such as limonene, surfactants, etc.), food (such as various organic substances), etc. will potentially be contaminated by such products. Finally, unintentional contamination can enter the plastic during production, for example, contaminating the plastic with reaction by-products, unreacted monomers, etc.

[0051] It should be recognized that different sources of recycled plastics have different levels of contamination and associated risks. Clearly, recycled plastic streams of unknown origin and life cycle will be the most abundant but also represent the highest likelihood of contamination. On the other hand, controlled recycled plastic streams are available and exhibit lower potential risks for demanding applications.

[0052] Pre-consumer plastics generally have the lowest level of contamination due to their known composition and controlled history. It can include intentional contamination, such as surface printing and opacifiers, but because these are known and controlled, it is very easy to find applications that can tolerate such known contaminants. Additionally, due to the controlled history, pre-consumer plastics tend to have a small amount of unintentional contamination, thus preventing external contamination. Therefore, pre-consumer plastics originally intended for demanding applications will be an ideal source of recycled plastics for the same end markets with the least amount of cleaning / purification. The latter pre-consumer plastics in film form are called "industry post-use films from approved sources" (ASPIF). The downside is that the ASPIF feedstock supply is very limited and does not support roundness.

[0053] Post-consumer plastics are generally more contaminated than pre-consumer plastics. Considering the slightly more controlled life cycle in the commercial supply chain, the post-consumer commercial subcategory has the second lowest level of contamination relative to pre-consumer recycling. Generally, post-consumer recycled plastics will have a known and controlled level of intentional contamination and can thus be widely used as recycled plastics. However, unintentional contamination is known to be prevalent and this stream has problems that prevent its widespread use in demanding applications. Post-consumer plastics from demanding applications will likely return to those areas after sufficient cleaning / purification. Post-consumer plastics from demanding applications in the form of film are called "Approved Source Post-Consumer Film" (ASPCF). To meet the continuing demand for purer recycled plastics, recycled source material suppliers have recently introduced post-consumer film sources with a more controlled and known history. These new sources are called high-custody sources and are mainly used with the post-consumer film stream. Thus, high-custody post-consumer film sources should have a reduced level of contamination relative to general post-consumer film sources. The downside is that these high-custody sources are limited in volume and costly.

[0054] Considering the uncontrolled life cycle within the commercial channel, the post-consumer household subcategory has the highest level of contamination. Such plastics have a highly variable, unknown, and uncontrolled high level of both intentional and unintentional contamination. Such plastics can include plastic sources that were not initially suitable for demanding applications. Thus, the market for such plastic sources is limited and they are essentially not available in demanding applications.

[0055] Surprisingly, the purer plastics made by the present invention allow for the wider use of source plastics from industrial post-consumer (both ASPIF and uncontrolled sources), commercial post-consumer (both ASPCF and uncontrolled sources), and household post-consumer in demanding applications. In addition, most consumers of all types require purer materials than are currently available and the purer plastics of the present invention meet this demand for a wider range of purer plastics from any source.

[0056] For the purposes of the present invention, non-limiting examples of plastics are film, sheet, injection molded parts, blow molded parts, fibers, non-wovens, woven fabrics, thermoformed parts, and extruded line stock.

[0057] The first plastic can be virgin plastic or recycled plastic. Additionally, 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 an 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 fiber, a nonwoven, a woven fabric, a thermoformed part, an extruded strand, or a mixture thereof.

[0058] In an embodiment of the present invention, the first plastic comprises regrind / trim / 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-consumer plastic. In another embodiment of the present invention, the first plastic comprises post-consumer film. In another embodiment of the present invention, the first plastic comprises post-consumer nonwoven. In yet another embodiment of the present invention, the post-consumer film is ASPCF. In another embodiment of the present invention, the first plastic comprises high-keeper post-consumer 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.

[0059] 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, and copolymers of any of the foregoing and mixtures of any of the foregoing. 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 an 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.

[0060] The first plastic can be in many forms, including but not limited to pellets, micronized pellets, ground pellets, shredded film, shredded or ground injection molded parts, shredded or ground blow molded parts, thermoformed parts, shredded nonwovens or woven fabrics, extruded strands or agglomerated particles. In an embodiment of the present invention, the first plastic comprises pellets.

[0061] III. Pollutants and Contamination

[0062] Contaminants can generally be broken down into two migration categories: 1) permeable; and 2) non-permeable. Permeable contaminants have solubility and diffusivity in the first plastic to allow migration into, through, and out of the plastic due to a chemical potential gradient. In other words, permeable contaminants and the grouping called permeable contamination are mobile. Non-permeable means that the contaminant does not have sufficient solubility and diffusivity to significantly move into, through, and out of the plastic. In other words, non-permeable contamination, represented by the sum of all non-permeable contaminants, is essentially fixed.

[0063] Chemical contaminants in the first plastic can be diverse but generally fall into one of several related chemical classes. Representative classes include pesticides, aldehydes, allergenic fragrances, indolines, alkylphenol ethoxylates, alkylphenols, bisphenols, dioxins, dioxin-like, furans, PCBs, organotins, metals, phthalates, polycyclic aromatic hydrocarbons (PAHs), etc. Only some of these chemical classes are commonly present in pre-consumer and post-consumer recycled materials, including pesticides, alkylphenol ethoxylates, alkylphenols, bisphenols, dioxins, dioxin-like, furans, PCBs, metals, organotins, phthalates, and PAHs.

[0064] Using the analytical methods disclosed in the Part IX method, the LOQs of various contaminants can vary by several orders of magnitude. For example, the LOQ of a typical pesticide is about 10 ppb; the LOQ of a typical alkylphenol ethoxylate is about 50 ppb; the LOQ of a typical alkylphenol is about 5 ppb; the LOQ of bisphenol A is about 5 ppb; the LOQ of a typical dioxin is about 0.2 pptr; the LOQ of a typical furan is about 0.2 pptr; the LOQ of a typical PCB is about 5 pptr; the LOQ of a typical heavy metal is about 100 ppb; the LOQ of a typical organotin is about 300 pptr; the LOQ of a typical phthalate is 50 ppb; the LOQ of a typical PAH is 1 ppb.

[0065] As shown in Tables 1a - 1i, several membrane sources were broadly classified for chemical fouling using the analytical methods disclosed in the partial IX method, including three ASPIF sources, three high - custody commercial post - use membrane sources, three commercial post - use membrane sources, and one household post - use membrane source. Note: To simplify the presentation of the chemical fouling 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 will be 10X LOQ or only 10 will be shown in the data table.

[0066] Table 1a - 1i

[0067] Chemical fouling of ASPIF, high - custody commercial post - use (HCPC), commercial post - use (PC), and household post - use (PH) membrane sources

[0068] Table 1a

[0069] Pesticide Chemical Contamination

[0070]

[0071]

[0072] Table 1b

[0073] Alkylphenol Ethoxylate Chemical Contamination

[0074]

[0075]

[0076] Table 1c

[0077] Alkylphenol Chemical Contamination

[0078]

[0079] Table 1d

[0080] Bisphenol Chemical Contamination

[0081]

[0082] Table 1e

[0083] Dioxin, Furan, and PCB Chemical Contamination

[0084]

[0085]

[0086] Table 1f

[0087] Heavy Metal Chemical Contamination

[0088]

[0089]

[0090] Table 1g

[0091] Organotin Chemical Contamination

[0092]

[0093]

[0094] Table 1h

[0095] Phthalate Chemical Contamination

[0096]

[0097] Table 1i

[0098] PAH Chemical Contamination

[0099]

[0100] With the exception of alkylphenols and heavy metals, as well as small amounts of organotin and PAH, the tested ASPIF sources were largely free of chemical contaminants at detectable levels. Since the ability of heavy metals to migrate from recycled sources is limited, they were not included in the ongoing analysis. The tested high-custody post-consumer film sources were largely free of pesticides and alkylphenol ethoxylates, but contained detectable levels of alkylphenols, bisphenol A, dioxins / furans / PCBs, and PAH, as well as low levels of phthalates. Each of the categories evaluated for the tested post-consumer film sources was severely contaminated.

[0101] From Tables 1a - 1i, representative chemicals are selected from various categories based on the prevalence in the spectra of recycled sources. The representative chemicals selected within these categories include: piperonyl butoxide (representing pesticides); 4 - tert - octylphenol hexaethoxylate and isononylphenol triethoxylate (representing alkylphenol ethoxylates); isononylphenol and 4 - tert - amylphenol (representing alkylphenols); bisphenol A (representing phenols); 1,2,3,6,7,8 - HxCDD, 1,2,3,4,6,7,8 - HpCDD, and OCDD (representing dioxins); OCDF (representing furans); PCB 105 and PCB 118 (representing PCBs); monobutyltin and dibutyltin (representing organotin); dibutyl phthalate and di - 2 - ethylhexyl phthalate (representing phthalates); and fluoranthene and phenanthrene (representing polycyclic aromatic hydrocarbons (PAHs)).

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

[0103] 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.

[0104] To simplify the analysis of the purification results of the objectives and related examples of the present invention, the number of chemicals presented for each chemical category is limited to the above - mentioned representative chemicals for each chemical category as shown in Table 2, as well as the relevant LOQs and corresponding levels of the tested ASPIF sources. Note: Although a more in - depth and complete chemical analysis has been completed for all objectives of the present invention, only the representative chemicals are continuously shown. This simplification will not affect or change the present invention or the conclusions drawn therefrom.

[0105] Table 2

[0106] Simplified Chemical Pollutants and Related LOQ Concentrations

[0107]

[0108]

[0109] In an embodiment of the present invention, the concentration of each pesticide in the purer plastic is lower than its corresponding LOQ; wherein the first plastic has at least one detectable pesticide. In an embodiment of the present invention, the concentration of bisphenol A in the purer plastic is lower than its corresponding LOQ; wherein the first plastic has at least detectable bisphenol A. In an embodiment of the present invention, the concentration of each dioxin in the purer plastic is lower than its corresponding LOQ; wherein the first plastic has at least one detectable dioxin. In an embodiment of the present invention, the concentration of each PCB in the purer plastic is lower than its corresponding LOQ; wherein the first plastic has at least one detectable PCB. In an embodiment of the present invention, the concentration of each phthalate in the purer plastic is lower than its corresponding LOQ; wherein the first plastic has at least one detectable phthalate.

[0110] 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 pptr; 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; and 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.

[0111] Typically, the efficacy of a cleaning process in removing a specific 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, due to the inability to determine concentrations below the LOQ, the removal efficiency is slightly insufficient. For example, if the cleaning process reduces the contamination from 2X LOQ to less than LOQ, the removal efficiency can be any value between 50% and 100%, which is a significant difference. Therefore, the removal efficiency is sufficient only when the chemical contaminant concentrations in both the first plastic and the purer plastic are above the LOQ. For simplicity, if the purer plastic has a chemical contaminant concentration below the LOQ, the chemical contaminant concentration of the purer plastic is assumed to be at the LOQ, and the removal efficiency is considered to be the minimum value and is designated with > to calculate the removal efficiency. For the above example, the removal efficiency would be calculated as 100(2×LOQ – 1×LOQ) / (2×LOQ) = 100(2 - 1) / 2 = 50%. Therefore, the removal efficiency will be >50%. In some cases, due to 1) measurement errors, 2) contaminant hotspots and cold spots in the first plastic, 3) external contamination during sampling, and 4) the purification process increasing contamination, the purer plastic will have a higher level of contaminants than the first plastic. In such cases, the removal efficiency is set to 0% so as not to deviate from the average result. If this occurs consistently during a given cleaning process, it is more likely to be attributed to the purification process and should be examined more closely, but this is generally not the case for the cleaning process of the present invention.

[0112] In one embodiment of the present invention, the removal efficiency of piperonyl butoxide contaminant is >55%, wherein the concentration of the piperonyl butoxide in the first plastic is at least 10 parts per billion. In another embodiment of the present invention, the removal efficiency of piperonyl butoxide contaminant is >96%, wherein the concentration of the piperonyl butoxide in the first plastic is at least about 10 parts per billion.

[0113] In an embodiment of the present invention, the removal efficiency of isononylphenol triethoxylate contaminant is >55%, wherein the concentration of the isononylphenol triethoxylate in the first plastic is at least 50 parts per billion. In another embodiment of the present invention, the removal efficiency of isononylphenol triethoxylate contaminant is >97%, wherein the concentration of the isononylphenol triethoxylate in the first plastic is at least 50 parts per billion.

[0114] In an embodiment of the present invention, the removal efficiency of 4-tert-amylphenol contaminant is >55%, wherein the concentration of the 4-tert-amylphenol in the first plastic is at least 5 parts per billion. In another embodiment of the present invention, the removal efficiency of 4-tert-amylphenol contaminant is >99%, wherein the concentration of the 4-tert-amylphenol in the first plastic is at least 5 parts per billion.

[0115] In an embodiment of the present invention, the removal efficiency of bisphenol A pollutant is > 55%, wherein the concentration of the bisphenol A in the first plastic is at least 5 parts per billion. In another embodiment of the present invention, the removal efficiency of bisphenol A pollutant is > 99%, wherein the concentration of the bisphenol A in the first plastic is at least 5 parts per billion.

[0116] In an embodiment of the present invention, the removal efficiency of OCDD pollutant is > 55%, wherein the concentration of the OCDD in the first plastic is at least about 0.2 parts per trillion. In another embodiment of the present invention, the removal efficiency of OCDD pollutant is > 99%, wherein the concentration of the OCDD in the first plastic is at least about 0.2 parts per trillion.

[0117] In an embodiment of the present invention, the removal efficiency of OCDF pollutant is > 55%, wherein the concentration of the OCDF in the first plastic is at least about 0.2 parts per trillion. In another embodiment of the present invention, the removal efficiency of OCDF pollutant is > 90%, wherein the concentration of the OCDF in the first plastic is at least about 0.2 parts per trillion.

[0118] In an embodiment of the present invention, the removal efficiency of PCB 118 pollutant is > 55%, wherein the concentration of the PCB 118 in the first plastic is at least 10 parts per trillion. In another embodiment of the present invention, the removal efficiency of PCB 118 pollutant is > 99%, wherein the concentration of the PCB 118 in the first plastic is at least about 10 parts per trillion.

[0119] In an embodiment of the present invention, the removal efficiency of di-2-ethylhexyl phthalate pollutant is > 55%, wherein the concentration of the di-2-ethylhexyl phthalate in the first plastic is at least about 50 parts per billion. In another embodiment of the present invention, the removal efficiency of di-2-ethylhexyl phthalate is > 90%, wherein the concentration of the di-2-ethylhexyl phthalate in the first plastic is at least about 50 parts per billion.

[0120] In an embodiment of the present invention, the removal efficiency of phenanthrene pollutant is > 55%, wherein the concentration of the phenanthrene in the first plastic is at least 1 part per billion. In another embodiment of the present invention, the removal efficiency of phenanthrene pollutant is > 90%, wherein the concentration of the phenanthrene in the first plastic is at least 1 part per billion.

[0121] Contamination can be located on the surface or throughout the plastic. Surface contamination is most conveniently and easily removed by surface cleaning techniques available on the current market. If the surface contamination in the plastic is permeable, it will become bulk contamination over time through a diffusion mechanism, thus complicating reduction and limiting the effectiveness of surface cleaning techniques. If the surface contamination is impermeable in the plastic, such contamination will not diffuse into the bulk and will be reduced by simple surface cleaning methods such as aqueous washing. Bulk contamination of the permeable or impermeable type generally cannot be effectively removed by simple surface purification methods such as aqueous washing. Impermeable type of bulk contamination (also known as bulk impermeable contamination) is trapped within the bulk plastic and can be released by mechanisms including melt convection, melt filtration, or dissolution / decomposition of the bulk plastic.

[0122] 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, over time the contamination will migrate into the bulk plastic. Thus, in the absence of contamination or purification events, the contamination will remain substantially constant, but the balance between surface and bulk contamination will change over time and will approach equilibrium over a long period. Generally, loosely bound surface contamination such as dirt can be from 0.01 wt% to about 0.1 wt%; while chemical contamination, especially the chemical contaminants involved in the present invention, will be in ppm, ppb, or even pptrillion.

[0123] Permeable and impermeable contamination represent different challenges in demanding applications. For example, permeable contamination, whether in the bulk plastic or on the surface of the plastic, will have the potential to migrate to uncontaminated materials such as products or human skin. However, if the contaminant is impermeable and in the bulk of the plastic, it will have a low ability to transfer to the product or the user's skin, unless the bulk plastic is broken down or ingested. 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. Permeable and impermeable surface contamination can be converted to bulk contamination by convective mechanisms such as melt blending and melt densification. These methods exchange or eliminate the surface region with the bulk material. For example, if a surface-contaminated film is melt densified or melt extruded into a different shape, such as pellets, all of the original surface contamination will become bulk contamination, whether it is impermeable or not, and such bulk contamination will be more difficult to remove with purification methods. Melt densification is common in the recycling industry. Shredding incoming plastics is also common in the recycling industry. The latter method generally does not convert surface contamination to bulk contamination. Ideally, surface purification methods such as surface washing occur on the original contaminated surface such as shredded film, where all of the original surface area is accessible by the surface washing fluid.

[0124] Generally, it is difficult to distinguish surface contamination from bulk contamination using analytical methods. Most analytical methods for permeable chemical contaminants involve solvent extraction of the contaminants from the plastic over an extended period of >6 hours and exposure to an extreme solvent-to-plastic mass ratio of >100:1, followed by the use of methods such as gas chromatography-mass spectrometry (GC-MS) to quantify the contaminants in the solvent. Such analytical methods quantify the contamination but do not distinguish between surface and bulk contaminants. The efficiency of a purification method for removing surface contamination can be estimated based on the difference in contamination before and after the surface cleaning step, but this assumes that the bulk contamination is not significantly affected, which may be the case for surface washing with the aqueous surface washing fluids discussed in the present invention. A more precise way to quantify surface contamination is by washing, then solvent extraction of the contaminants at different times, and then extrapolating the amount of contaminants removed at infinitesimal time, which will approximate the amount of surface contamination. However, this method is time-consuming and costly, especially for contaminants that are generally difficult to measure. In addition, since the equilibrium between surface and bulk contaminants is dynamic, it is difficult to quantify without reference to the exact 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.

[0125] Generally, overall contamination will not be significantly removed by simple aqueous surface washing. Permeable overall contamination can be removed by diffusion mechanisms through chemical potential gradients. Although overall non-permeable contamination is essentially trapped by the bulk polymer, methods for releasing the trapped contaminants include melt convection, melt filtration, and dissolution / disintegration of the plastic.

[0126] IV. Surface Purification Methods

[0127] Surface purification methods reduce surface contamination. One such method is surface washing with a surface washing fluid that is typically water-based. Surface washing is ideally done before any melt blending or melt densification to allow effective cleaning of the pristine contaminated surface. The first plastic is typically 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 surface wash due to their overall large size. Therefore, a pelletizing or shredding step is preferred before surface washing. For films, it is particularly important to exfoliate all available film layers so that the washing fluid can access all the original surface contamination. Therefore, the size reduction step before surface washing should not significantly reduce the surface area to volume ratio of the recycled source or exchange it with a new surface area. In an embodiment of the present invention, the surface washing of the first plastic is carried out after the shredding or pelletizing step. In an embodiment of the present invention, the surface area to volume ratio of the recycled source is preferably higher than about 1 mm-1, more preferably higher than about 5 mm-1, even more preferably higher than about 20 mm-1, and most preferably higher than about 50 mm-1. Surface washing will include significant mechanical agitation to loosen surface dirt and other contaminants, thereby allowing physical removal and transfer into the washing fluid, where the dirt or other contaminants may or may not dissolve. As used herein, a surface washing method is any method in which recycled plastic in its original contaminated form (except for the possibility of volume size reduction not exceeding 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 methods 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. The typical level of loosely bound surface contamination for film-based recycled sources is between about 0.01 wt% and 0.1 wt%. For the purposes of the present invention regarding the first plastic involving surface washing, the surface washing method will remove more than about 80% of the loosely bound surface contamination, as determined by Method 2 shown in Part IX.

[0128] Surface washing techniques are widely available on the market. One representative technique is from Lindner (Lindner Washtech GmbH, 4, Germany). This technology is described in detail elsewhere (https: / / www.lindner-washtech.com / system-solutions), but involves the possibility of water washing under intense mechanical agitation and the application of caustic soda to remove adhesives, followed by drying and granulation.

[0129] Another representative surface washing technology comes 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 intense mechanical agitation, followed by drying and granulation.

[0130] Another representative technology comes from Sorema (Sorema S.r.l., Anzano del Parco, Italy). This technology is described in detail elsewhere (http: / / sorema.it / en_US / applications / washing-line / ) but involves aqueous operations similar to Lindner and Herbold.

[0131] Another representative surface washing technology comes from Cadel, called deinking (Cadel Deinking, Alicante, Spain). This technology is described elsewhere (http: / / cadeldeinking.com / en / ), but basically involves the surface washing of materials using a high-temperature aqueous solution with specific surfactants, followed by water rinsing and drying. This alternative method may include densification, melt filtration, devolatilization, and granulation after surface washing. This method differs from other known methods in that it requires the removal of surface printed ink. This would be advantageous as the burden of removing chemical contaminants is reduced by the overall purification method of the present invention.

[0132] Three surface washing technologies of the prior art were evaluated to remove target classes of chemical contaminants (Comparative Example 1, Comparative Example 2, and Comparative Example 3). Different recycled film inputs with different levels of contamination were used to evaluate each surface washing technology. Overall, the surface washing technologies of the prior art cannot adequately purify recycled materials for controlled end markets. For the target contaminants, although the initial contamination of the corresponding recycled sources is low, the commercial technologies cannot reduce it to levels close to the LOQ. In addition, the average removal efficiencies of 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate are less than about 55%.

[0133] V. Melt Densification

[0134] Assume that the surface purification temperature is lower than the initial melting point of the first plastic. Then, the plastic emerging from the surface purification step typically has a similar geometry and a similar surface area to volume ratio as the incoming recycled plastic. For example, if the recycled plastic is a loose film, after shredding and surface washing at a temperature lower than the initial melting point of the first plastic, the film will leave the surface purification as shredded film. Since such loose plastics are difficult to feed into certain bulk purification methods such as liquid-liquid extraction, it may be desirable to densify such plastics into a melt prior to bulk purification. A preferred method of melt densification is melt extrusion. Melt extrusion not only densifies the plastic, but it can also provide the pressure required for downstream bulk purification such as liquid-liquid extraction. Melt extrusion can 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 downstream bulk purification steps. Other densification methods are known in the art, including rotary disk and rotary drum densifiers, which operate at lower temperatures relative to melt-based methods.

[0135] In an embodiment of the present invention, the melt densification includes melt extrusion. In another embodiment of the present invention, the melt extrusion includes melt filtration. In another embodiment of the present invention, the melt extrusion includes melt devolatilization. In yet another embodiment of the present invention, the melt extrusion includes melt pumping. In an embodiment of the present invention, the melt densification includes melt extrusion, melt filtration, melt devolatilization, and melt pumping.

[0136] VI. Bulk Purification

[0137] Generally, simple aqueous surface washing will not significantly reduce bulk contamination. Melt filtration and melt devolatilization will have the potential to remove bulk contaminants of large geometric size and to remove some volatile bulk contaminants, but will be largely ineffective for most bulk contaminants, particularly for the required levels.

[0138] One technique available on the market for performing bulk purification is the InterRema Refresher from EREMA (EREMA Group, Ansfelden, Austria) https: / / www.erema.com / en / refresher / TMThis technique is described in detail elsewhere, but basically involves devolatilizing particulate material at a temperature below the initial melting point of the plastic for an extended period of time to remove volatile organic compounds. Most of the chemical contaminants associated with recycled materials and discussed in the previous section are highly non-volatile, having standard boiling points typically above 200 °C. Thus, this type of devolatilization technique will have limited ability to remove most of the chemical contaminants mentioned in this application.

[0139] Other techniques based on devolatilization are common. These can be standalone unit operations or combined with other operations including extrusion and melt filtration. Those utilizing sub-atmospheric pressure above the molten stream of recycled plastic are common.

[0140] The purification ability of an overall purification technique involving devolatilization was analyzed. This technique 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 in Comparative Example 4 below). Commercial devolatilization techniques cannot adequately remove the target contaminants. For example, the target contaminants are still far above the LOQ. Additionally, the average removal efficiency is ~20%.

[0141] Extraction is the preferred overall purification method. Extraction involves using a purification solvent to remove overall permeable contaminants by creating a chemical potential gradient between the first plastic and the solvent. The rate of removal of permeable chemical contaminants will depend on the diffusivity and solubility of the contaminants in the plastic under the conditions created in the method. For high molecular weight plastics, the diffusivity of the large molecules indicative of chemical contaminants is very low, especially in the solid state of the plastic. Additionally, solubility may be limited due to the high MW of the first plastic and the lack of enthalpic mixing. Thus, the time required to remove permeable contaminants by a diffusion mechanism can be quite long and is not conducive to a method that is economically viable on a commercial scale. Methods to address these timescale limitations include 1) increasing diffusivity by elevated temperature and / or increasing 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 convective transport of contaminants across the plastic / solvent interface by increasing the solubility of the contaminants in the solvent, increasing the partitioning of the contaminants in the solvent relative to the plastic; increasing convection at the plastic / solvent interface, and increasing the solvent bath relative to the plastic bath. The solubility of the overall purification solvent in the plastic can be increased by operating the extraction at high pressures, particularly at, near, or above the critical pressure.

[0142] Importantly, the extraction method is scalable to large volumes at low cost. Accordingly, the time required for extraction should be short to permit such 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 done in stages, the time for each stage can be less than this range, but the total time will still fall within these times.

[0143] The extraction can be carried out at, near, at or below the initial melting point of the first plastic. Extraction carried out at or near or above the initial melting point of the first plastic is referred to as liquid-liquid extraction. Extraction carried out below the initial melting point of the first plastic is referred to as packed leaching extraction. The extraction solvent used in packed leaching extraction is referred to as the packed leaching solvent.

[0144] In the filling leaching method of the present invention, the first plastic is in a filled form, and the volume of the solvent in contact with the first plastic at any point in time is sufficient to fill or insufficient to fill the void volume. For the purposes of the present invention, such a filling leaching method is referred to as a filling leaching method. For loose-filled shredded membranes, the void volume % can be as high as about 90%, but once in contact with the filling leaching solvent, the void volume typically drops to less than about 83%. Thus, at most about 5 volumes of solvent will be able to fill about 1 volume of the filled shredded membrane. Since most of the solvents of interest in the present invention have a density lower than that of the recycled plastic, the maximum mass ratio of the solvent capable of completely filling the loose-filled shredded membrane will be less than 5:1. Since the shredded membrane tends to have the lowest bulk density of the recycled material, the mass of the solvent required to fill this filled volume is less than about 5:1 relative to the mass of the first plastic. Thus, for the purposes of the present invention involving filling leaching extraction, the mass ratio of the solvent in contact with the first plastic at any point in time and at any stage is preferably less than about 5:1. Such filling leaching methods can be percolation-type or immersion-type, and such filling leaching methods are common in the edible oil industry but not common in the plastics industry. In a percolation-type filling leaching method, the volume of the solvent in contact with the material to be extracted at any point in time within any stage is less than the void volume in the material to be extracted. The filling leaching solvent continuously drips through the filled material in a series of stages. The material can be continuously moved from one stage to another by the filling leaching method. Commercial examples of such percolation-based filling leaching methods include Rotocel, Carousel, and Loop extractors, which are commonly used to extract various oils from biological sources. In an immersion-type filling leaching method, the volume of the solvent in contact with the material to be extracted at any point in time and at any stage is equal to or greater than the void volume in the filled material. In an immersion filling leaching method, the material to be extracted is held in place while the solvent flows through, such as a filled bed, or the material is conveyed using mechanical means (such as a conveying screw, such as solid-state extrusion or a belt). Examples of solid-state extrusion are commercial methods such as those provided by PureVision Technologies, where the solvent flows countercurrently to the flow of the extraction solids (http: / / www.purevisiontechnology.com / about / ). Other examples of screw-type systems are the Hildebrand reactor. Another example of an immersion filling leaching method is the Type IV extractor of Crown Iron Works Company.

[0145] The filling of the first plastic should be sufficient to prevent excessive tumbling or agitation, but not so high as to eliminate the surface area for mass transfer.

[0146] Particularly for packed leaching, a packed leaching solvent that causes excessive swelling and thus softening of the first plastic can be problematic due to agglomeration. In such cases, it may be necessary to further reduce the packed leaching temperature to avoid agglomeration. Since the first plastic does not exhibit significant swelling or softening, using an oxygen-containing and / or polar packed leaching solvent may not have such problems. Unlike liquid-liquid where phase stability may be problematic with oxygen-containing or polar packed leaching solvents, using an oxygen-containing or polar packed leaching solvent can provide benefits for packed leaching, including higher partitioning of contaminants into the packed leaching solvent.

[0147] In the packed leaching method of the present invention, the pressure can range from atmospheric pressure to less than about 1,000 atm.

[0148] In the packed leaching method of the present invention, the packed leaching temperature can be at or below the standard boiling point of the packed leaching solvent. Additionally, the pressure in such cases can be at atmospheric pressure or above atmospheric pressure. In an embodiment of the present invention, the overall extraction is packed leaching, and the pressure of the packed leaching is about atmospheric pressure, and the packed leaching solvent is at or below the standard boiling point. For a polyolefin first plastic, a preferred packed leaching solvent for packed leaching has a boiling point of less than about 90 °C. Examples of such solvents are THF, dimethyl ether, propane, ethane, hexane, propanol, diethyl ether, hexane, acetone, ethanol, methanol, propanol, isopropanol, MEK, and ethyl acetate. In another embodiment of the present invention, the packed leaching solvent has a standard boiling point below about 90 °C, and the pressure is above atmospheric pressure but below 1,000 atm.

[0149] In one embodiment of the present invention, the packed leaching solvent has a standard boiling point above the packed leaching temperature. In another embodiment of the present invention, wherein the packed leaching solvent is ethyl acetate; the temperature of the packed leaching is between about 20 °C and about 120 °C; and the pressure of the packed leaching is between about atmospheric pressure and about 1,000 atm. In another embodiment of the present invention, wherein the overall purification is packed leaching; wherein the packed leaching solvent is hexane; the temperature of the packed leaching is between about 20 °C and about 120 °C; and the pressure of the packed leaching is between about atmospheric pressure and about 1,000 atm.

[0150] Due to the elevated packing leaching pressure, packing leaching solvents with a standard boiling point lower than the packing leaching temperature are also preferred. In an embodiment of the present invention, the packing leaching solvent has a standard boiling point lower than the packing leaching temperature. In one embodiment of the present invention, the packing leaching solvent is propane. In one embodiment of the present invention, wherein the overall purification is packing leaching; wherein the packing leaching solvent is propane; the temperature of the packing leaching is between about 20 °C and about 120 °C; and the pressure of the packing leaching is between about 9 atm and about 1,000 atm. In another embodiment of the present invention, the packing leaching solvent is dimethyl ether (DME). In one embodiment of the present invention, wherein the overall purification is packing leaching; wherein the packing leaching solvent is DME; the temperature of the packing leaching is between about 20 °C and about 120 °C; and the pressure of the packing leaching is between about 6 atm and about 1,000 atm.

[0151] Packing leaching solvents with a standard boiling point lower than the packing leaching temperature and a critical temperature lower than the packing leaching temperature are also preferred. In an embodiment of the present invention, the packing leaching solvent has a standard boiling point lower than the packing leaching temperature and a critical temperature lower than the packing leaching temperature. In one embodiment of the present invention, the packing leaching solvent is ethane. In another embodiment of the present invention, the packing leaching solvent is critical or supercritical ethane. In yet another embodiment of the present invention, wherein the overall purification is packing leaching; wherein the packing leaching solvent is ethane; the temperature of the packing leaching is between about 31 °C and about 120 °C; and the pressure of the packing leaching is between about 40 atm and about 1,000 atm. In another embodiment of the present invention, the packing leaching solvent is CO2. In yet another embodiment of the present invention, wherein the overall purification is packing leaching; wherein the packing leaching solvent is CO2; the temperature of the packing leaching is between about 31 °C and about 120 °C; and the pressure of the packing leaching is between about 68 atm and about 1,000 atm. In yet another embodiment of the present invention, the purified packing leaching solvent is CO2 with <5 wt% H2O.

[0152] For percolation packing leaching of the present invention, the density of the packing leaching solvent is not important. For immersion packing leaching of the present invention, the density of the packing leaching solvent is preferably less than the density of the first plastic at the temperature and pressure of the packing leaching. For polyethylene recycled materials, the density of the immersion packing leaching solvent at the temperature and pressure of the packing leaching is preferably less than about 0.90 g / cc if a packed bed type of immersion process is used, but higher densities can still be used.

[0153] Preferred leaching solvents include solvents that have a higher affinity for chemical contaminants than for the first plastic. Solvents that have a high affinity for the chemical contaminants of interest in recycled polyolefins relative to their affinity for polyolefins include, but are not limited to, diethyl ether, MEK, ethyl acetate, THF, acetone, dichloromethane, and methanol. Other oxygenated and polar hydrocarbon solvents may have similar desired affinities. Solvents lacking such properties may still be used, but higher solvent-to-polymer ratios may be required. Preferably, the solvent should not significantly dissolve the first plastic (<~5 wt% soluble) at the temperature and pressure of the process. For the filling leaching process of the present invention, the filling leaching solvent should preferably not significantly soften or swell the first plastic, otherwise agglomeration of the filled first plastic may become a problem. This is especially true in packed bed and screw-based conveyor filling leaching, where the first plastic can be under significant compaction pressure.

[0154] In an embodiment of the present invention, the filling leaching solvent is selected from the group consisting of hydrocarbons. In another embodiment of the present invention, the leaching solvent is selected from the group consisting of aliphatic hydrocarbons. In yet another embodiment of the present invention, the leaching solvent is selected from the group consisting of aromatic hydrocarbons. In yet another embodiment of the present invention, the leaching solvent is selected from the group consisting of alkanes.

[0155] In an embodiment of the present invention, the leaching solvent is selected from the group consisting of: methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, neopentane, hexane (n-hexane, isohexane, neohexane, heptane), octane, or mixtures thereof.

[0156] The temperature can be changed during the extraction process, but is typically consistent within a given stage of the unit operation. The pressure can be changed to vary the solubility of the solvent in the first plastic or to increase the solubility of the chemical contaminants in the solvent.

[0157] The packed leaching extraction method can be carried out in stages and combined with other types of additional packed leaching extraction methods. The same is true for liquid-liquid extraction methods. In addition, the liquid-liquid method can be combined with the packed leaching method at different stages to form a given purification method. In an embodiment of the present invention, the number of stages is more than one. In another embodiment of the present invention, the number of liquid-liquid stages is more than one. In another embodiment of the present invention, the number of packed leaching stages is more than one. In yet another embodiment of the present invention, the number of liquid-liquid stages is one or more, and the number of packed leaching stages is one or more. A single stirred tank reactor will achieve a certain removal efficiency. The efficiency can be increased by having multiple stirred tank reactors in series, where the first plastic from the first stage is mainly separated from the first stage purification solvent, and this first stage plastic is used in the second stage with fresh purification solvent. This is repeated for each additional stage. The method increases the removal efficiency at the expense of additional reactors and complexity, but maintains the total time, throughput, and solvent utilization.

[0158] While not wishing to be bound by theory, the theoretical maximum contaminant removal capacity of the packed leaching method is based on the thermodynamic equilibrium / distribution of chemical contaminants between the first plastic and the packed leaching solvent at the temperature and pressure of the method. Due to kinetic limitations during the packed leaching process, the thermodynamic equilibrium may not be achieved. This is true for the complete packed leaching process and for each packed leaching stage. A higher packed leaching solvent to first plastic mass ratio will drive the thermodynamics and kinetics in favor of purification, at the expense of greater solvent consumption and a larger extraction process size, which equals greater cost. Therefore, for a target chemical contaminant removal efficiency, a balance must be found between these important design and operating variables. Generally, the applicant has found that the total fresh or renewed packed leaching 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 packed leaching is done in stepwise or continuous stages, the packed leaching solvent to first plastic ratio for each stage can be lower than this specified range (but still higher than the minimum per stage of ∼5:1), 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 method can be renewed by known methods such as distillation, filtration, ion exchange, etc. or combinations thereof.

[0159] Another important kinetic driver is the surface area to volume ratio of the first plastic that is within and exposed to the packed leaching solvent. Generally, the time required to extract chemical contaminants from the first plastic is a strong function of the diffusion path length within the first plastic. The diffusion path length is indirectly proportional to the surface area to volume ratio of the geometry of the first plastic and the ability to access the surface region with the packed leaching solvent. Accordingly, a higher surface area to volume ratio will result in a reduced diffusion path length and faster diffusion kinetics. For the packed leaching method, a high surface area to volume ratio is a key parameter for rapid and efficient removal of surface and bulk contaminants.

[0160] For packed leaching extraction, since the processing temperature is below the initial melting point, the surface area to volume ratio of the first plastic that is within and exposed to the extraction solvent is substantially the same as the surface area to volume ratio of the first plastic. For membrane-based regeneration, the packed leaching method is desirable because of the extremely high inherent surface area to volume ratio. If the regenerated material is provided in other forms with a lower surface area to volume ratio, such as pellets, granulated bottles, granulated parts, etc., it would be advantageous to increase the surface area to volume ratio in various ways. These ways include but are not limited to mechanical grinding, cryogenic grinding, calendering, pressing, stretching, etc. The applicant has found that the use of a first plastic with a surface area to volume ratio greater than ~1 mm-1, greater than ~5 mm-1 is preferred, even more preferably greater than ~20 mm-1, and most preferably greater than ~50 mm-1. In an embodiment of the present invention, the surface area to volume ratio of the first plastic is greater than about 1 mm-1. In another embodiment of the present invention, the surface area to volume ratio of the first plastic is greater than about 5 mm-1. In another embodiment of the present invention, the surface area to volume ratio of the first plastic is greater than about 20 mm-1. In yet another embodiment of the present invention, the surface area to volume ratio of the first plastic is greater than about 50 mm-1.

[0161] A known method of increasing the effective mass transfer at the first plastic-solvent interface by a given surface area to volume ratio and a given set of conditions is to apply energy to the first plastic, such as but not limited to vibrational energy in the form of ultrasonic energy and / or microwaves.

[0162] After bulk purification involving extraction, the plastic can be devolatilized to produce a purer plastic. The contaminated solvent will contain a small amount of dissolved purer plastic, the extracted contaminants, and the pure leaching solvent. There are many methods for recovering the purer polymer and bulk purifying the solvent that are independent of the extracted contaminants.

[0163] Typically, regardless of the method type or solvent, small amounts of the first plastic can dissolve into the leaching solvent. In particular, low molecular weight waxes are particularly prone to dissolving into the extraction solvent. Due to the deposition of wax on the processing equipment, these can become problematic in the distillation-based recovery of the purification solvent. Methods for reducing this tendency are known. One such method is to lower the temperature of the contaminated solvent below the cloud point to precipitate the polymer or wax phase, followed by filtration. Unlike the first plastic, the residual plastic or wax resulting from the precipitation of the contaminated solvent may contain significant chemical contamination.

[0164] Distillation of the contaminated overall purification solvent can be used to regenerate the solvent for reuse in various extraction operations. However, considering the high solvent volumes used in the present invention, distillation may not be economically viable. Additionally, because the concentrations of the chemical contaminants of interest in the present invention are extremely low, the concentrations of these chemical contaminants in the contaminated solvent can be correspondingly low or even lower. Therefore, the preferred method for purifying the contaminated solvent is by directly removing the contaminants without volatilizing the overall solvent phase. 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. Additionally, 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 method can be updated by known methods such as distillation, filtration, ion exchange, etc. or combinations thereof. In one embodiment of the present invention, the packed leaching solvent is purified using an absorption or adsorption-based method. In another embodiment of the present invention, the packed leaching solvent is purified using an absorption or adsorption-based method, followed by distillation.

[0165] The purer plastic can contain small amounts of solvent in the form of physical adsorption or bulk adsorption. The concentration of the 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 solvent content of <1 wt% in the first plastic.

[0166] Overall, packed leaching is significantly more effective than prior art methods in removing target contaminants. For example, using supercritical CO2, removal efficiencies in the range of approximately 55% to greater than approximately 85% are obtained. Additionally, using supercritical ethane, removal efficiencies greater than approximately 90% are obtained where most target chemical contaminants are removed below the LOQ. Additionally, using propane, removal efficiencies greater than approximately 97% are obtained where all target chemical contaminants are near the LOQ. Finally, using DME, removal efficiencies in the range of approximately 94% to approximately greater than 98% are obtained.

[0167] In an embodiment of the present invention, the packed leaching solvent comprises a supercritical fluid; the supercritical fluid comprises ethane; the temperature of the packed leaching is from about 35°C to about 90°C; wherein the pressure is between about 73 atm and about 1,000 atm; wherein the packed leaching solvent is CO2.

[0168] In one embodiment of the present invention (Table 7 of Example 1A), the packed leaching solvent comprises a supercritical fluid; the supercritical fluid comprises CO2; the temperature of the packed leaching is about 80°C; the pressure of the packed leaching is about 340 atm; the mass ratio of CO2 to the first plastic is ~20:1; the surface area to volume ratio of the first plastic is ~6 1 / mm; and the average packed leaching time is ~110 minutes; wherein the purification method results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate of about 67%.

[0169] In another embodiment of the present invention (Examples 1B and Table 7), the packed leaching solvent comprises a supercritical fluid; the supercritical fluid comprises CO2; the surface area to volume ratio of the first plastic is ~6 1 / mm; the temperature of the packed leaching is about 90°C; the packed leaching involves 2 stages; the pressure of the first stage of the packed leaching is about 340 atm; the mass ratio of CO2 to the first plastic in the first stage is ~30:1; and the average extraction time of the first stage is ~110 minutes; wherein the pressure of the second stage of the packed leaching is about 680 atm; the ratio of CO2 to the first plastic in the second stage is ~30:1; and the average extraction time of the second stage is ~110 minutes; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate > about 85%.

[0170] In another embodiment of the present invention (Table 7 of Example 1C), the packed leaching solvent comprises a supercritical fluid; the supercritical fluid comprises CO2 saturated with water; the temperature of the packed leaching is about 80°C; the pressure of the packed leaching is about 340 atm; the mass ratio of CO2 to the first plastic is ~20:1; the surface area to volume ratio of the first plastic is ~6 1 / mm; and the average extraction time is ~70 minutes; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate > 77%.

[0171] In an embodiment of the present invention, the packed leaching solvent comprises a supercritical fluid; the supercritical fluid comprises ethane; the temperature of the packed leaching is from about 35 °C to about 90 °C; wherein the pressure is between about 48 atm and about 340 atm; wherein the packed leaching solvent is ethane.

[0172] In another embodiment of the present invention (Table 8 of Example 2), the packed leaching solvent comprises a supercritical fluid; the supercritical fluid comprises ethane; the temperature of the packed leaching is about 70 °C; the pressure of the overall purification varies between about 340 atm and about 82 atm; wherein the packed leaching is completed in 13 stages; wherein the total mass ratio of ethane to the first plastic is about 34 and the total extraction time is about 278 minutes; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate greater than 90%.

[0173] In an embodiment of the present invention, the packed leaching solvent comprises propane; the temperature of the packed leaching is from about 20 °C to about 90 °C; wherein the pressure is between about 7 atm and about 1,000 atm.

[0174] In another embodiment of the present invention (Table 9 of Example 3), the packed leaching solvent comprises propane; the temperature of the packed leaching is about 70 °C; the pressure of the packed leaching is about 238 atm; wherein the packed leaching involves 3 packed leaching stages; wherein Stage 1 involves a mass ratio of dimethyl ether to the first plastic of ~7.3 and a time of about 29.9 minutes; wherein Stage 2 involves a mass ratio of propane to the first plastic of 0 and a time of about 60 minutes; wherein Stage 3 involves a mass ratio of propane to the first plastic of ~12.2 and a time of about 49.9 minutes, with a total mass ratio of propane to the first plastic of ~19.5 and a total packed leaching time of about 139.8 minutes; the surface area to volume ratio of the first plastic is ~6 1 / mm; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate > about 96.5%.

[0175] In an embodiment of the present invention, the packed leaching solvent comprises dimethyl ether; the temperature of the packed leaching is from about 20 °C to about 90 °C; wherein the pressure is between about 5 atm and about 1,000 atm.

[0176] In another embodiment of the present invention (Table 10 of Example 4A), the packed leaching solvent comprises dimethyl ether; the temperature of the packed leaching is about 70 °C; the pressure of the packed leaching is about 238 atm; wherein the packed leaching involves 3 packed leaching stages; wherein Stage 1 involves a dimethyl ether to first plastic mass ratio of ~9.5 and a time of about 37.3 minutes; wherein Stage 2 involves a dimethyl ether to first plastic mass ratio of 0, for a time of about 60 minutes; wherein Stage 3 involves a dimethyl ether to first plastic mass ratio of ~15.8, for a time of about 62.2 minutes, the total dimethyl ether to first plastic mass ratio being ~25.3 and the total packed leaching time being about 159.5 minutes; the surface area to volume ratio of the first plastic is ~61 / mm; and the average extraction time is ~160 minutes; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate > about 98.3%.

[0177] In another embodiment of the present invention, the packed leaching solvent comprises dimethyl ether (Table 10 of Example 4B); the temperature of the packed leaching is about 70 °C; the pressure of the packed leaching is about 27 atm; wherein the packed leaching involves 3 packed leaching stages; wherein Stage 1 involves a dimethyl ether to first plastic mass ratio of ~8 and a time of about 33.8 minutes; wherein Stage 2 involves a dimethyl ether to first plastic mass ratio of 0, for a time of about 60 minutes; wherein Stage 3 involves a dimethyl ether to first plastic mass ratio of ~13.3, for a time of about 56.4 minutes, the total dimethyl ether to first plastic mass ratio being ~21.3 and the total packed leaching time being about 150.2 minutes; the surface area to volume ratio of the first plastic is ~61 / mm; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate > about 95%.

[0178] In an embodiment of the present invention, the packed leaching solvent comprises ethyl acetate; the temperature of the packed leaching is from about 20 °C to about 90 °C; wherein the pressure is between about atmospheric pressure and about 340 atm.

[0179] In another embodiment of the present invention, the packed leaching solvent comprises ethyl acetate (Table 11 of Example 5); the temperature of the packed leaching is about 70 °C; the pressure of the packed leaching is about 10 atm; wherein the packed leaching involves 3 packed leaching stages; wherein stage 1 involves an ethyl acetate to first plastic mass ratio of ~11.1 and a time of about 27.5 minutes; wherein stage 2 involves an ethyl acetate to first plastic mass ratio of 0, for a duration of about 60 minutes; wherein stage 3 involves an ethyl acetate to first plastic mass ratio of ~18.5, for a duration of about 45.8 minutes, with a total ethyl acetate to first plastic mass ratio of ~29.6 and a total packed leaching time of about 133.3 minutes; the surface area to volume ratio of the first plastic is ~6 1 / mm; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate > about 94.1%.

[0180] After packed leaching, the purer plastic may be physically wetted by the residual solvent and may contain a small amount of absorbed solvent. As discussed previously, there are many methods for recovering the purer polymer and overall purifying the solvent that are unrelated to the extracted contaminants. The purified polymer can be dried and devolatilized by many known commercial means. One method is by flash drying. Another method is by melt extrusion with a devolatilization section. In an embodiment of the present invention, the purer plastic is processed to reduce the packed leaching solvent in the first plastic to less than about 1 wt%. The contaminated solvent can be cleaned by known distillation methods, ion exchange, filtration, etc. The resulting devolatilized first plastic can be used as is or can be further processed into other forms, including pellets, by various methods.

[0181] VI. Surface + Bulk Purification

[0182] Generally, a combination of surface purification methods and overall purification methods provides the benefit of overall removal of contamination. Surface purification methods will effectively remove non-permeable and permeable surface contamination, including chemical contaminants and chemical contaminant precursors. Thus, surface purification reduces the burden of overall purification and makes it more effective. If the first plastic is severely contaminated with surface contamination, it is preferably first treated by surface purification methods and then by overall purification methods 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 not significantly removed by this two-step method is overall non-permeable contamination, such as heavy metals intentionally added during the production of the original plastic part.

[0183] The preferred method of surface washing has 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 contaminants such as dirt, but also removes the ink printed on the surface. 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 method, where surface contaminants including surface printed ink, dirt, grit, paper, adhesives, etc. are 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 where the method removes surface imprints (ΔE measured using Method 3 in Part IX) that are sufficient to result in a ΔE difference of less than about 10% between the deinked first plastic and the unprinted first plastic.

[0184] For naming purposes, the contaminated plastic fed into 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 into the bulk purification process and purified into a purer plastic. The surface purification method can involve multiple surface purification processes. The bulk purification method can involve various types of multiple bulk purification processes. The removal efficiency of the combined surface and bulk purification method will be calculated based on the first plastic concentration and the associated purer plastic.

[0185] The combination of the surface washing and bulk purification techniques of the present invention provides an average removal efficiency of greater than about 96% to greater than about 98% for bisphenol A, 4-tert-amylphenol, OCDD, PCB 108, and di-2-ethylhexyl phthalate (Examples 6 to 9 and Tables 12 to 15). In most cases, the target contaminants are removed to levels close to or below the LOQ, which would potentially enable use in a controlled end market.

[0186] In an embodiment of the present invention, a method of producing a purer plastic from a first plastic is provided; wherein the first plastic has a certain concentration of contaminants; wherein the purer plastic has a certain concentration of contaminants; wherein the contaminants of the first plastic include at least one of the following chemical classes; dioxins, PCBs, phthalates, bisphenols, and alkylphenols; wherein the method comprises 1) a surface washing method for removing surface contamination, followed by 2) extraction at a certain temperature and pressure and using a leaching solvent; wherein the surface washing method removes more than 80% of the loose surface contamination; wherein the method reduces the concentration of the contaminants in the first plastic to the concentration of the contaminants in the purer plastic; and wherein the average reduction in the concentration of the contaminants from the first plastic to the purer plastic is at least about 55% or the LOQ.

[0187] In an embodiment of the present invention, the extraction is carried out after surface washing. In another embodiment of the present invention, the extraction is carried out after surface washing, wherein the first plastic is not densified before surface washing. In another embodiment of the present invention, the extraction is carried out after surface washing; wherein the first plastic is not densified before surface washing; wherein the second plastic may be densified before the extraction process.

[0188] In an embodiment of the present invention, the extraction uses a leaching solvent operating at a certain temperature and pressure; wherein the overall purification method operates in stages; wherein the first plastic has been partially purified using a surface washing method.

[0189] In one embodiment of the present invention (Table 12 of Example 6), wherein the surface washing involves deinking commercially available through Cadel; wherein the surface washing removes >80% of the loose surface contamination; wherein the overall purification involves packed leaching in a packed bed; wherein the overall purification solvent includes a supercritical fluid; the supercritical fluid includes CO2; the surface area to volume ratio of the first plastic is ~6 1 / mm; the temperature of the overall purification is about 90 °C; the overall purification involves 2 stages; the pressure of the overall purification stage 1 is about 340 atm; the mass ratio of CO2 to the first plastic in stage 1 is ~30:1; and the average extraction time in stage 1 is ~180 minutes; wherein the pressure of the overall purification stage 2 is about 680 atm; the ratio of CO2 to the first plastic in stage 2 is ~30:1; and the average extraction time in stage 2 is ~180 minutes; wherein the purification method results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 108, and di-2-ethylhexyl phthalate > about 96%.

[0190] In another embodiment of the present invention (Table 13 of Example 7), wherein the surface washing involves deinking commercially available through Cadel; wherein the surface washing removes more than 80% of the loose surface contamination; wherein the overall purification involves packed leaching in a packed bed; wherein the packed leaching solvent includes supercritical; the supercritical fluid is ethane; the temperature of the packed leaching is about 70 °C; the pressure of the overall purification varies between about 340 atm and 82 atm; wherein the packed leaching is completed in 13 stages; wherein the total mass ratio of ethane to the first plastic is about 34 and the total extraction time is about 278 minutes; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 108, and di-2-ethylhexyl phthalate greater than about 96%.

[0191] In another embodiment of the present invention (Table 14 of Example 8), wherein the surface washing involves deinking commercially available through Cadel; wherein the surface washing removes more than 80% of the loose surface contamination; wherein the overall purification involves packed leaching; wherein the packed leaching solvent includes dimethyl ether; the temperature of the packed leaching is about 70 °C; the pressure of the packed leaching is about 238 atm; wherein the packed leaching involves 3 packed leaching stages; wherein Stage 1 involves a dimethyl ether to first plastic mass ratio of ~9.5 and a time of about 37.3 minutes; wherein Stage 2 involves a dimethyl ether to first plastic mass ratio of 0, for a time of about 60 minutes; wherein Stage 3 involves a dimethyl ether to first plastic mass ratio of ~15.8, for a time of about 62.2 minutes, the total dimethyl ether to first plastic mass ratio being ~25.3 and the total packed leaching time being about 159.5 minutes; the surface area to volume ratio of the first plastic is ~80 1 / mm; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 108, and di-2-ethylhexyl phthalate > about 98.3%.

[0192] In another embodiment of the present invention (Table 15 of Example 9A), wherein the surface washing involves deinking commercially available through Cadel; wherein the surface washing removes loose surface contamination > 80%; wherein the overall purification involves packed leaching; wherein the packed leaching solvent includes dimethyl ether; the temperature of the packed leaching is about 70 °C; the pressure of the packed leaching is about 27 atm; wherein the packed leaching involves 3 packed leaching stages; wherein Stage 1 involves a dimethyl ether to first plastic mass ratio of ~7.3 and a time of about 33.8 minutes; wherein Stage 2 involves a dimethyl ether to first plastic mass ratio of 0, for a time of about 60 minutes; wherein Stage 3 involves a dimethyl ether to first plastic mass ratio of ~12.2, for a time of about 56.4 minutes, the total dimethyl ether to first plastic mass ratio being ~19.5 and the total packed leaching time being about 150.2 minutes; the surface area to volume ratio of the first plastic is ~6 1 / mm; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 108, and di-2-ethylhexyl phthalate > about 93.9%.

[0193] In another embodiment of the present invention (Table 15 of Example 9B), wherein the surface washing involves deinking commercially available from Cadel; wherein the surface washing removes >80% of the loose surface contamination; wherein the overall purification involves packed leaching in a packed bed; wherein the packed leaching solvent comprises dimethyl ether; the temperature of the packed leaching is about 70 °C; the pressure of the packed leaching is about 27 atm; wherein the packed leaching involves 3 packed leaching stages; wherein stage 1 involves a dimethyl ether to first plastic mass ratio of ~7.4 and a time of about 33.8 minutes; wherein stage 2 involves a dimethyl ether to first plastic mass ratio of 0, for a time of about 60 minutes; wherein stage 3 involves a dimethyl ether to first plastic mass ratio of ~12.3, for a time of about 56.4 minutes, with a total dimethyl ether to first plastic mass ratio of ~19.7 and a total packed leaching time of about 150.2 minutes; the surface area to volume ratio of the first plastic is ~6 1 / mm; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 108, and di-2-ethylhexyl phthalate of > about 98%.

[0194] 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 certain concentration of contaminants; wherein the purer plastic has a certain concentration of contaminants; wherein the contaminants of the first plastic include at least one of the following chemical classes; dioxins, PCBs, phthalates, bisphenols, and alkylphenols; wherein the method comprises 1) a surface washing method for removing surface contamination, followed by 2) extraction at a certain temperature and pressure, and using a leaching solvent; wherein the extraction temperature is below the initial melting point of the first plastic, referred to as packed leaching; wherein at a given stage and any point in time the packed leaching solvent to first plastic ratio is less than about 5:1; wherein the packed leaching is carried out for a period of time and each stage is carried out for a period of time; wherein the packed leaching reduces the concentration of the contaminants in the first plastic to the concentration of the contaminants in the purer plastic; and wherein the average reduction in the concentration of the contaminants from the first plastic to the purer plastic is at least about 55% or LOQ.

[0195] In an embodiment of the present invention, the extraction is carried out after surface washing; wherein the surface washing removes more than 80% of the loosely bound surface contaminants. In another embodiment of the present invention, the extraction is carried out after surface washing; wherein the surface washing is a deinking type; wherein the deinking removes more than 80% of the loosely bound surface contaminants; wherein the deinking results in a ΔE change of <10%. In another embodiment of the present invention, the extraction is carried out after surface washing, wherein the first plastic is not densified before surface washing. In another embodiment of the present invention, the extraction is carried out after surface washing; wherein the first plastic is not densified before surface washing; wherein the second plastic can be densified before the extraction process.

[0196] In one embodiment of the present invention (Table 12 of Example 6), the surface washing involves deinking commercially available through Cadel; wherein the surface washing removes >80% of the loosely bound surface contaminants; the overall purification includes packed leaching at a pressure between about 90 °C and about 340 atm to 680 atm; wherein the packed leaching solvent is CO2; wherein the number of stages is 2; wherein the CO2 to total mass feed ratio of the first plastic is ~60:1 and the average extraction time is ~360 minutes; the average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate is greater than about 96%.

[0197] In one embodiment of the present invention (Table 13 of Example 7), the surface washing involves deinking commercially available through Cadel; wherein the surface washing removes >80% of the loosely bound surface contaminants; wherein the overall purification involves packed leaching; wherein the packed leaching solvent includes a supercritical fluid; wherein the supercritical fluid is ethane; wherein the temperature of the packed leaching is about 70 °C; wherein the pressure of the overall purification varies between about 340 atm and 82 atm; wherein the packed leaching is completed in 13 stages; wherein the ethane to total mass ratio of the first plastic is about 34, and the total extraction time is about 278 minutes; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate greater than about 96%.

[0198] In another embodiment of the present invention (Table 14 of Example 8), the surface washing involves deinking commercially available through Cadel; wherein the surface washing removes >80% of the loosely bound surface contamination; wherein the overall purification involves packed leaching; wherein the packed leaching solvent is dimethyl ether; wherein the temperature of the packed leaching is about 70 °C; wherein the pressure of the packed leaching is about 238 atm; wherein the packed leaching involves 3 packed leaching stages; wherein Stage 1 involves a dimethyl ether to first plastic mass ratio of ~9.5 and a time of about 37.3 minutes; wherein Stage 2 involves a dimethyl ether to first plastic mass ratio of 0, for a time of about 60 minutes; wherein Stage 3 involves a dimethyl ether to first plastic mass ratio of ~15.8, for a time of about 62.2 minutes, with a total dimethyl ether to first plastic mass ratio of ~25.3 and a total packed leaching time of about 159.5 minutes; wherein the surface area to volume ratio of the first plastic is ~6 1 / mm; wherein the average extraction time is ~160 minutes; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate > about 98%.

[0199] In another embodiment of the present invention (Table 15 of Example 9A), the surface washing involves deinking commercially available through Cadel; wherein the surface washing removes >80% of the loosely bound surface contamination; wherein the overall purification involves packed leaching; wherein the packed leaching solvent comprises dimethyl ether; wherein the temperature of the packed leaching is about 70 °C; wherein the pressure of the packed leaching is about 27 atm; wherein the packed leaching involves 3 packed leaching stages; wherein Stage 1 involves a dimethyl ether to first plastic mass ratio of ~7.3 and a time of about 33.8 minutes; wherein Stage 2 involves a dimethyl ether to first plastic mass ratio of 0, for a time of about 60 minutes; wherein Stage 3 involves a dimethyl ether to first plastic mass ratio of ~12.2, for a time of about 56.4 minutes, with a total dimethyl ether to first plastic mass ratio of ~19.5 and a total packed leaching time of about 150.2 minutes; wherein the surface area to volume ratio of the first plastic is ~6 1 / mm; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate > about 94%.

[0200] In another embodiment of the present invention (Table 15 of Example 9B), the surface washing involves deinking commercially available from Cadel; wherein the surface washing removes >80% of the loosely bound surface contamination; wherein the overall purification involves packed leaching; wherein the packed leaching solvent includes dimethyl ether; wherein the temperature of the packed leaching is about 70 °C; wherein the pressure of the packed leaching is about 27 atm; wherein the packed leaching involves 3 packed leaching stages; wherein Stage 1 involves a dimethyl ether to first plastic mass ratio of ~7.4 and a time of about 33.8 minutes; wherein Stage 2 involves a dimethyl ether to first plastic mass ratio of 0, for a time of about 60 minutes; wherein Stage 3 involves a dimethyl ether to first plastic mass ratio of ~12.3, for a time of about 56.4 minutes, with a total dimethyl ether to first plastic mass ratio of ~19.7 and a total packed leaching time of about 150.2 minutes; wherein the surface area to volume ratio of the first plastic is ~6 1 / mm; wherein the packed leaching results in an average removal efficiency of bisphenol A, 4-tert-amylphenol, OCDD, PCB 118, and di-2-ethylhexyl phthalate > about 98%.

[0201] VII. Purer Plastic

[0202] The purer plastic produced from the first plastic has a lower level of contamination 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 desired, such steps can involve melt extrusion followed by pelletizing. The melt extrusion can optionally include a melt filtration step and / or a devolatilization step. The melt extrusion can include additional ingredients for the purer plastic, such as AO, slip agent, anti-blocking agent, TiO2, colorant, etc.

[0203] VIII. Examples

[0204] Comparative Example 1 - Using a commercially available water washing method #1, followed by melt densification to purify high - custody commercial post - film Back film

[0205] The first plastic material, consisting of high-security commercial post-consumer film #1, is fed into a commercially available purification method. 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 method's ability to remove a large amount of permeable contamination should be minimal. A small amount of volatile bulk contamination should be removed during drying and melt densification, but overall, the bulk contamination should be largely unaffected. In addition, the high-security commercial post-consumer film source used as the first plastic has limited chemical contamination, as evidenced by low levels of pesticides, dioxins, and phthalates. The types of chemical contaminants commonly present in recycled materials in the first plastic and the purer plastic are analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX. After purification, the purer plastic contains a slightly reduced level of chemical contamination, as shown in Table 3. The removal rates of the five selected substances are 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 approximately 52%.

[0206] Table 3

[0207] Using commercial water washing process #1 to purify high - custody commercial post (HCPC) source #1

[0208]

[0209]

[0210] Comparative Example 2 - Using water washing method #2, followed by melt densification to purify high - custody commercial post - film #2

[0211] Feed the first plastic material, which consists of high-custody commercial post-consumer film #2, into a commercially available purification process to produce a purer plastic. The cleaning process consists of shredding, hot water washing, drying, and melt densification. As in the case of the water washing process #1, the process should remove surface contamination, but has limited ability to remove a large amount of permeable contamination. Analyze the types of chemical contaminants commonly present in recycled materials in the first plastic and the purer plastic using the method disclosed in part IX of the method by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany), as shown in Table 4. The high-custody film source (the first plastic) has limited chemical contamination, as evidenced by low levels of dioxins, PCBs, phthalates, and PAHs. The purer plastic contains 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 severely contaminated feed streams and / or variability in the contamination level of the current feed. The removal rates of the five selected substances are 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 approximately 14%.

[0212] Table 4

[0213] Using commercial water washing process #2 to purify high - custody commercial post (HCPC) source #2

[0214]

[0215]

[0216] Comparative Example 3A - Using a commercial de - inking method from Cadel to purify commercial post - film #1 。

[0217] The first plastic material, which consists of commercial post-consumer film #1, is fed into a purification process called deinking (http: / / cadeldeinking.com / en / ) that is commercially available from Cadel to produce a purer plastic. The method consists of shredding, aqueous deinking, water washing / rinsing, and drying. According to the patented technology, the deinking step involves elevated temperature, elevated pH, and surfactants. The various washing steps should effectively remove surface contamination. Additionally, due to the elevated temperature, a small amount of overall permeable contamination will be removed, which will increase the diffusion rate, and due to the surfactant / pH combination, the solubility of the contaminants in water may increase. However, the overall extraction rate is expected to be low. The introduced first plastic was determined to have 0.125 wt% of loosely bound surface contamination compared to approximately 0.02 wt% of the purer plastic in the form of fragments. Thus, the cleaning process removes greater than 80% of the introduced loosely bound surface contamination. After cleaning but before analyzing the first plastic for chemical contamination, the fragments are melt densified at 190 °C using a single-screw extruder to produce pellets. The pellets are ground to a mass average diameter of 300 to 500 microns. The types of chemical contaminants typically present in recycled materials in the first plastic and the purer plastic are analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 5. The first plastic contains a moderate level of chemical contamination, indicating a lack of high custody life cycle for the commercial post-consumer film. For example, the introduced dioxins such as OCDD are 40 times the LOQ, which is higher than the high custody sources of Comparative Example 1, Comparative Example 2, and Comparative Example 5 described previously. Additionally, 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 (~1,000 times the LOQ), further indicating the level of chemical contamination within this recycled source. The first plastic consists of shredded film, where most of it melts together to form plastic blocks. Thus, the effectiveness of the surface cleaning technique using this source is somewhat inhibited due to the inability to access the fully contaminated surface. After the deinking process, the purer plastic contains a reduced level of chemical contamination. The removal rates for the five selected substances are as follows: for 4-tert-amylphenol, the removal efficiency is 71%. For bisphenol A, the removal efficiency is 0%. For OCDD, the removal efficiency is 60%. For PCB 118, the removal efficiency is 0%. For di-2-ethylhexyl phthalate, the removal efficiency is 22%. The average removal efficiency for the five target substances is approximately 31%.

[0218] Comparative Example 3B - Using a commercial de - inking method from Cadel to purify household post - film #1 。

[0219] The first plastic material consisting of post - consumer film #1 was fed into the surface purification method of Comparative Example 3A to produce a purer plastic. The introduced first plastic was determined to have 0.047 wt% of loosely - bound surface contamination, compared to approximately 0.003 wt% of the purer plastic. Thus, the cleaning process removed more than 80% of the introduced loosely - bound surface contamination. Before analyzing chemical contamination, the fragments of post - consumer film #1 were melt - densified and granulated using an extruder. The granular material was ground to a mass - average particle size of 300 to 500 microns. The types of chemical contaminants commonly present in recycled materials in the first plastic and the purer plastic were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 5. The first plastic contained extremely high levels of chemical contamination, including significant fouling. For example, the pesticide piperonyl butoxide was ~7 times the LOQ; alkylphenol ethoxylates were ~1,000 times the LOQ; dioxins and phthalates were ~300 times the LOQ. The purer plastic contained 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 the surface area exposed by the cleaning process, 2) differences in the distribution of chemical contaminants on the surface and within the bulk, and 3) the inherent variability of chemical contaminants within the samples and the variability of measurement techniques. The removal rates 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%.

[0220] Table 5

[0221] Using commercial de - inking to purify commercial post (PC) source #1 and household post (PH) source #1

[0222]

[0223] Comparative Example 4 - Using a commercial de - odorizing method to purify high - custody commercial post - film #3

[0224]

[0225] Feed a first plastic material consisting of high-custody commercial post-consumer film #3 into a purification method known as the deodorization technique. The method includes exposing the granular feed to moderate temperatures and continuous air rinsing. Thus, this cleaning technique mainly removes volatile surface and bulk contamination. However, most of the chemical contaminants associated with the controlled end markets are highly non-volatile. Analyze the types of chemical contaminants commonly present in recycled materials in the first plastic and the purer plastic using the method disclosed in part IX of the method by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany), as shown in Table 6. The high-custody film source #3 has limited chemical contamination, as evidenced by low levels of dioxins, PCBs, phthalates, and PAHs. The purer plastic contains slightly reduced levels of chemical contamination. The removal rates for 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 is 0%. The average removal efficiency for the five target substances is approximately 41%.

[0226] Table 6

[0227] Using commercial de - odorizing to purify high - custody commercial post (HCPC) source #3

[0228] Generally, established methods for purifying / cleaning films and other plastic wastes (including water washing, deinking, and devolatilization) currently cannot adequately remove chemical contaminants, especially in high-custody sources. Even with high-custody sources, chemical contamination still exists and is not completely removed, which may limit the end-use for certain consumers. Therefore, the need for a cleaning technique that can more completely remove chemical contamination sufficient for highly contaminated sources and for any market requiring purer recycled materials has not been met.

[0229] Example 1 - Bulk purification involving packed - bed leaching using supercritical CO2 and ground granular commercial post - film #3 of the first plastic 。

[0230] Example 1A - A grinding step was performed on a first plastic material consisting of granular commercial post - film #3 to reduce the mass average particle size from ~3 mm to 5 mm to ~1 mm. The resulting first plastic had a surface area to volume ratio of ~6 mm-1. The resulting ground commercial post - film was fed to an integral purification step involving packed - bed leaching (Phasex Corporation, 125 Flagship Drive, North Andover, MA). Approximately 168.1 g of the ground first plastic was loaded into a high - pressure packed bed with a volume of 500 mL. The temperature of the process was set at 80 °C (note: below the initial melting temperature of the first plastic), and the pressure was set at 340 atm. CO2 was introduced into the column at a CO2 flow rate of ~15 standard L / min or a CO2 to first - plastic mass ratio of approximately 20:1, and a packed - bed leaching solvent feed rate of ~15 SL / min or ~30 g / min. The total extraction time was ~110 minutes. The CO2 to first - plastic mass ratio at any point in the packed bed was between approximately 1 and 2:1. There was only 1 extraction step, and 167.5 g of a purer plastic was collected. The types of chemical contaminants commonly present in recycled materials in the first plastic and the purer plastic #1 were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 7. The first plastic was severely contaminated. For example, the pesticide piperonyl butoxide was ~28 times the LOQ, alkylphenols were ~100 times the LOQ, bisphenol A was 760 times, dioxins / furans / PCBs were up to ~200 times, phthalates LOQ was ~20 times, and PAH LOQ was ~40 times. The purer plastic #1 was significantly cleaner in all respects but still had a large amount of contaminants due to the extreme contamination of the feed source. Due to the increased surface area to volume ratio provided by the ground granular form, the overall removal rate was higher than in Example #2. The removal rates for five selected substances were as follows: For 4 - tert - amylphenol, the removal efficiency was 79%. For bisphenol A, the removal efficiency was 77%. For OCDD, the removal efficiency was 30%. For PCB118, the removal efficiency was 59%. For di - 2 - ethylhexyl phthalate, the removal efficiency was 91%. The average removal efficiency for the five target substances was approximately 67%.

[0231] Example 1B - The same ground first plastic material was fed to the overall purification step involving extraction by packed leaching as follows. Approximately 105.0 g of the ground first plastic was loaded into a typical supercritical CO2 extractor with a volume of 500 mL, and extraction was carried out at approximately 90 °C (below the initial melting point of the first plastic), approximately 340 atm, and a solvent-to-feed ratio of approximately 30:1 for approximately 110 min. Then the pressure was increased to 680 atm, where an additional 30:1 solvent was introduced and held for another 110 min to produce a purer plastic #2. The total solvent-to-first plastic mass ratio was approximately 60:1, and the total extraction time was approximately 220 minutes. The CO2-to-first plastic mass ratio at any point in the packed bed was between approximately 1 and 2:1. The purer plastic #2 was collected and had a mass of 104.4 g. The residue collected after evaporation of the contaminated CO2 was ∼0.6 g. The types of chemical contaminants typically present in recycled materials in the purer plastic #2 were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 7. The purer plastic #2 was significantly cleaner in all respects compared to the purer plastic #1, due to the increased solvent-to-first plastic ratio, increased extraction time, and increased pressure, but still had a large amount of contaminants due to the extreme contamination of the feed source. The removal rates for the five selected substances were as follows: for 4-tert-amylphenol, the removal efficiency was 99%. For bisphenol A, the removal efficiency was 87%. For OCDD, the removal efficiency was 50%. For PCB 118, the removal efficiency was 93%. For di-2-ethylhexyl phthalate, the removal efficiency >94%. The average removal efficiency for the five target substances was approximately >85%.

[0232] Example 1C - Feed the same ground first plastic material to the following packed leaching extraction overall purification step. Load approximately ~105.7 g of the ground first plastic into a typical supercritical CO2 extractor with a volume of 500 mL. At a purification temperature of approximately 80 °C, at a pressure of approximately 340 atm and a CO2 to first plastic mass ratio of approximately 20:1, extract with a CO2 feed rate of ~15 SL / min or ~30 g / min and a total extraction time of approximately 70 minutes using a CO2 purification solvent containing a saturated amount of water. The CO2 to first plastic mass ratio at any point in the packed bed is between approximately 1 and 2:1. Add a small amount of water to increase the solubility of polar components and potentially extract more polar contaminants in the first plastic. Produce approximately 105.0 g of a purer plastic #3 and analyze the types of chemical contaminants typically present in recycled materials using the method disclosed in Part IX by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany), as shown in Table 7. The purer plastic #3 is significantly cleaner in all aspects but still has a large amount of contaminants due to the extreme contamination of the feed source. The overall removal rate is higher than that of the purer plastic #1 but slightly lower than that of the purer plastic #2. However, the purer plastic #2 is produced at a significantly longer purification time, a higher solvent to first plastic ratio, and a higher pressure. Therefore, adding water significantly improves compared to adding CO2 alone. The increased polarity generated by water may increase the inherent solubility of chemical contaminants in the solvent, thus increasing the flux and efficiency at a given time. The removal rates of the five selected substances are as follows: for 4-tert-amylphenol, the removal efficiency > 99%. For bisphenol A, the removal efficiency is 92%. For OCDD, the removal efficiency is 23%. For PCB 118, the removal efficiency is 79%. For di-2-ethylhexyl phthalate, the removal efficiency > 94%. The average removal efficiency of the five target substances is greater than approximately 77%.

[0233] If water-saturated CO2 is combined with pressure pulses, further improvement in removal efficiency may be achieved.

[0234] Table 7

[0235] Using standard conditions (purer plastic #1), pulsed conditions (purer plastic #2), and wet conditions (purer plastic #3), solid / liquid extraction with scCO2 in a packed bed to purify commercial post (PC) film #3 source Example 2 - Bulk purification by packed - bed leaching using supercritical ethane at 70 °C in a packed bed of ground granular commercial post - film #3

[0236]

[0237]

[0238] Example 2 - Bulk purification by packed - bed leaching using supercritical ethane at 70 °C in a packed bed of ground granular commercial post - film #3 Example 2 - Bulk purification by packed - bed leaching using supercritical ethane at 70 °C in a packed bed of ground granular commercial post - film #3 。

[0239] A grinding step is performed on the first plastic material composed of granular commercial post-film #3 to reduce the mass average particle size from ~3 mm to 5 mm to ~1 mm, with a surface area to volume ratio of ~6 mm-1. This first plastic is fed into the following overall purification step involving packed leaching extraction (Phasex Corporation, 125 Flagship Drive, North Andover, MA). Approximately 100.5 g of the first plastic is loaded into a 500 mL volume high-pressure packed bed extractor. The extraction is completed in 13 stages. For stage #1, at a pressure of 340 atm, the bed is filled with ethane at a ratio of approximately 1.6 of ethane to the mass of the first plastic at 70 °C for a time of approximately 9.6 minutes. For stage #2, an amount of ethane equal to an ethane to first plastic mass ratio of approximately 1.2:1 is evacuated to reduce the pressure to 82 atm, and then a similar 1.2 ethane to first plastic mass ratio is introduced to increase the pressure back to approximately 340 atm over a time period of approximately 14.6 minutes. This stage is repeated 5 times. For stage #7, ethane is continuously added to the packed bed at approximately 340 atm for approximately 61.2 minutes to a total ethane to first plastic ratio of approximately 10.2; for stages #8 to #12, stages #2 to #6 are repeated. For stage #13, stage #7 is replicated to produce a purer plastic. The total ethane to first plastic mass ratio is approximately 34, and the total extraction time is approximately 278 minutes. The mass of the contaminants collected by volatilizing the contaminated ethane is ~1.3 g. The purer plastic is collected and has a mass of ~99.2 g. The types of chemical contaminants commonly present in recycled materials in the purer plastic are analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 8. The removal rates of the five selected substances are as follows: for 4-tert-amylphenol, the removal efficiency is 98%. For bisphenol A, the removal efficiency is 85%. For OCDD, the removal efficiency is 75%. For PCB 118, the removal efficiency >99.6%. For di-2-ethylhexyl phthalate, the removal efficiency >94%. The average removal efficiency of the five target substances is greater than approximately 90%.

[0240] Table 8

[0241] Using packed - bed leaching with sc ethane at 70 °C in a packed bed to purify commercial post (PC) film #3 source 。

[0242]

[0243]

[0244] Example 3 - Bulk purification by packed - bed leaching using propane at 70 °C in a packed bed of ground granular commercial post - film #3 Example 3 - Bulk purification by packed - bed leaching using propane at 70 °C in a packed bed of ground granular commercial post - film #3 。

[0245] The same first plastic material as the first plastic ground in Example 2 was fed to the following overall purification step involving packed leaching (Phasex Corporation, 125 Flagship Drive, North Andover, MA). Approximately 100.4 g of the first plastic was loaded into a high-pressure packed bed extractor with a total volume of 500 mL. The extraction was carried out at approximately 70 °C and approximately 238 atm for a total of 3 stages. For all stages, the mass ratio of propane to the first plastic in the packed bed was less than approximately 4:1. The first stage involved a propane to first plastic mass ratio of approximately 7.3 and an extraction time of approximately 30 minutes. The second stage was to hold for 60 minutes without adding new propane. The third stage involved a propane to first plastic mass ratio of approximately 12.2 and an extraction time of approximately 50 minutes. The total propane to first plastic mass ratio was approximately 19.5 and the total extraction time was 140 minutes. The purer plastic was collected and had a mass of 97.2 g, and the contaminants remained in the evaporated contaminated propane. The types of chemical contaminants commonly present in recycled materials in the purer plastic were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 9. The purer plastic was significantly cleaner than the severely contaminated feed material. Propane was surprisingly more effective in removing a wide range of contaminants compared to supercritical ethane.

[0246] For 4-tert-amylphenol, the removal efficiency > 99%. For bisphenol A, the removal efficiency was 96%. For OCDD, the removal efficiency was 94%. For PCB 118, the removal efficiency > 99.6%. For di-2-ethylhexyl phthalate, the removal efficiency > 94%. The average removal efficiency of the five target substances was greater than approximately 97%.

[0247] Table 9

[0248] Using packed - bed leaching with propane at 70 °C in a packed bed to purify commercial post (PC) film #3 source 。

[0249]

[0250]

[0251] Example 4 - Bulk purification by packed - bed leaching in a packed bed of ground granular commercial post - film #3 and household post - film #1 Example 4 - Bulk purification by packed - bed leaching in a packed bed of ground granular commercial post - film #3 and household post - film #1

[0252] Example 4A - Overall purification using packed leaching with DME in the packed bed of ground granular commercial post-film #3.

[0253] The same first plastic material as that ground in Example 2 was fed to the overall purification step (Phasex Corporation, 125 Flagship Drive, North Andover, MA) as extracted below. The first plastic had a mass average particle size of ~1 mm and an average surface area to volume ratio of ~6 mm-1. Approximately 101.4 g of the first plastic was loaded into a high-pressure packed bed extractor with a total volume of 500 mL. The leaching solvent was dimethyl ether (DME). The extraction was carried out at approximately 70 °C and approximately 238 atm and included 3 stages. At all times, the DME to first plastic ratio was less than approximately 4:1. The solvent feed rate was approximately 26 g / min for approximately 37 minutes (DME:first plastic mass ratio of ~9.5:1), followed by holding for approximately 60 minutes with no additional dimethyl ether added, and then feeding fresh dimethyl ether at approximately 26 g / min (DME:first plastic mass ratio of ~15.8:1) for approximately 62 minutes. Thus, the total solvent to first plastic mass ratio was approximately 25:1, and the total extraction time was approximately 160 minutes. The contaminants collected by evaporating the contaminated dimethyl ether were ~3.6 g, and the mass of the purer plastic was ~97.8 g. The types of chemical contaminants commonly present in recycled materials in the purer plastic were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 10. The purer plastic was almost completely below the LOQ for all chemical contaminants, even with a severely contaminated feed stream. If a cleaner feed stream such as high custody commercial post-use was used, even cleaner and purer plastic would be produced. For 4-tert-amylphenol, the removal efficiency >99.1%. For bisphenol A, the removal efficiency >99.9%. For OCDD, the removal efficiency was 99%. For PCB 118, the removal efficiency >99.6%. For di-2-ethylhexyl phthalate, the removal efficiency >94%. The average removal efficiency of the five target substances was greater than approximately 98%.

[0254] Example 4B - Bulk purification by packed - bed leaching using DME in a packed bed of ground household post #1

[0255] The first plastic material consisting of post-consumer #1 film has been melt-compacted using a single-screw extruder to produce 3 mm to 5 mm pellets, which are then ground to a mass-average particle size of ~1 mm. Thus, the first plastic has a surface area to volume ratio of ~6 mm-1. The first plastic is fed to the integral purification involving packed leaching as follows (Phasex Corporation, 125 Flagship Drive, North Andover, MA). Approximately 109.0 g of the first plastic is loaded into a high-pressure packed-bed extractor with a total volume of 500 mL. At all times, the DME to first plastic ratio in the packed bed is less than about 4:1. The extraction is carried out at 70 °C and a pressure of 27 atm, with DME introduced into the packed bed at a rate of ~26 g / min for a total of 34 minutes (DME:first plastic mass ratio ~8:1), followed by a hold of 60 min with no additional dimethyl ether added, and then another phase of solvent flow at ~26 g / min for 56 minutes (DME:first plastic mass ratio ~13.3:1). Thus, the total feed of DME to the first site is ~21:1, and the total extraction time is ~150 minutes. The mass of the residue collected after evaporation of the contaminated diethyl ether is 2.9 g, and the total mass of the purer plastic is ~106.1 g. The types of chemical contaminants typically present in recycled materials in the purer plastic are analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 10. For 4-tert-amylphenol, the removal efficiency >99.7%. For bisphenol A, the removal efficiency is 75%. For OCDD, the removal efficiency is 99.7%. For PCB118, the removal efficiency >99.3%. For di-2-ethylhexyl phthalate, the removal efficiency is 99.9%. The average removal efficiency of the five target substances is greater than about >95%.

[0256] Table 10A

[0257] Using packed - bed leaching with DME at 70 °C in a packed bed to purify commercial post (PC) film #3 source 。

[0258]

[0259] Table 10B

[0260] Using DME in a packed bed with packed - bed leaching to purify ground household post (PH) film #1

[0261]

[0262] Example 5 - Bulk purification by packed - bed leaching using ethyl acetate in a packed bed of ground commercial post #3 Example 5 - Bulk purification by packed - bed leaching using ethyl acetate in a packed bed of ground commercial post #3

[0263] The first plastic material, consisting of commercial post-consumer film #3, has been melt-compacted using a single-screw extruder to produce 3 mm to 5 mm pellets, which were then ground to a mass-average particle size of ~1 mm. Thus, the first plastic has a surface area to volume ratio of ~6 mm-1. The first plastic was fed to the following integral purification step involving packed leaching extraction (Phasex Corporation, 125 Flagship Drive, North Andover, MA). Approximately 121.8 g of the first plastic was loaded into a high-pressure packed bed extractor with a total volume of 500 mL. The extraction was carried out at 70 °C and a pressure of approximately 10 atm. At all times, the mass ratio of ethyl acetate to the first plastic in the packed bed was less than approximately 4:1. Ethyl acetate was introduced into the packed bed at a rate of ~49 g / min for ~28 minutes (ethyl acetate: first plastic mass ratio ~11.1:1), followed by a 60 min hold, followed by another stage at ~49 g / min for 46 minutes (ethyl acetate: first plastic mass ratio ~18.5:1). Thus, the total feed of ethyl acetate to the first plastic was ~30:1, and the total extraction time was ~133 minutes. The purer plastic was collected and had a mass of 120.1 g. The contaminant residue collected after evaporation of the contaminated ethyl acetate was ~1.7 g. The types of chemical contaminants typically present in recycled materials in the purer plastic were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 11.

[0264] For the contaminant 4-tert-amylphenol, the removal efficiency was 79.3%. For the contaminant bisphenol A, the removal efficiency was 98.6%. For the contaminant OCDD, the removal efficiency was 98.9%. For PCB 118, the removal efficiency >99.6%. For di-2-ethylhexyl phthalate, the removal efficiency >94.4%. The average removal capacity for the contaminants 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate was >94.1%.

[0265] Table 11

[0266] Purification by packed leaching using ethyl acetate in a packed bed of ground post - consumer (PC) film #3

[0267]

[0268]

[0269] Example 6 - Combination of surface washing by Cadel deinking and overall purification by packed leaching using post - consumer film #1 and scCO2 in a packed bed Table 12

[0270] The first plastic material in the form of shredded film composed of a purer plastic from Comparative Example 3B (referred to as purer plastic #1 in this example) was fed to the following overall purification step involving packed-bed extraction (Phasex Corporation, 125 Flagship Drive, North Andover, MA). Approximately 96.7 g of the first plastic was loaded into a typical supercritical CO2 extractor with a volume of approximately 500 mL, and leaching was carried out at approximately 90 °C, approximately 340 atm, and a solvent-to-feed ratio of approximately 30 for about 3 hours. The pressure was then pulsed to 680 atm, where an additional 30 volumes of solvent were introduced into the polymer and held for another 3 hours to produce a purer plastic. The total CO2-to-first plastic mass ratio was approximately 60:1, and the total extraction time was approximately 360 minutes. At all times, the mass of CO2 in the packed bed was less than approximately 4:1 relative to the mass of the first plastic. The mass of contaminants collected from the contaminated CO2 was 1.8 g, and the total mass of the purer plastic was ~94.9 g. The surface area-to-volume ratio of the first plastic was approximately 80 mm-1. The types of chemical contaminants commonly present in recycled materials in the purer plastic were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 12. In all respects, the purer plastic was significantly cleaner. The combination of surface washing followed by overall extraction produced a cleaner recycled material. If a high-holding or cleaner feed source is available, this combination of cleaning methods will be even cleaner.

[0271] For the contaminant 4-tert-amylphenol, the removal efficiency > approximately 99.9%. For the contaminant bisphenol A, the removal efficiency > 99%. For the contaminant OCDD, the removal efficiency was 91%. For PCB 118, the removal efficiency > 93%. For di-2-ethylhexyl phthalate, the removal efficiency was 99%. The average removal capacity for the contaminants 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate was greater than approximately 96%.

[0272] Purification involving surface washing and overall purification by packed leaching of post - consumer (PH) film #1 using scCO2 in a packed bed

[0273] Example 7 - Combination of surface washing by Cadel deinking + overall purification involving packed leaching using supercritical ethane in a packed bed of post - consumer film #1 Table 13

[0274]

[0275]

[0276] Purify post - consumer (PH) film #1 using both surface washing and overall purification involving packed leaching using sc ethane in a packed bed Example 8 - Combination of surface washing by Cadel deinking and overall purification involving packed leaching using DME in a packed bed of post - consumer film #1

[0277] A first plastic material consisting of a purer plastic from Comparative Example 3B (surface area to volume ratio of 80 mm-1) is fed to a solid-liquid extraction involving packed leaching in a packed bed involving 13 stages at 70 °C. Approximately 100.7 g of the first plastic is loaded into a high-pressure packed bed extractor with a total volume of 500 mL. At all times, the ratio of ethane to the first plastic in the packed bed is less than approximately 4:1. The first stage involves an ethane to first plastic mass ratio of approximately 1.6 and a time of approximately 9.6 minutes at a pressure of 340 atm. The second stage involves evacuating ethane with an ethane to first plastic mass ratio of 1.2 to provide a pressure of 82 atm, followed by introducing ethane with an ethane to first plastic mass ratio of 1.2 to generate a pressure of approximately 340 atm over a period of approximately 14.6 minutes. The second stage is repeated five times. The seventh stage involves an ethane to first plastic ratio of approximately 10.2 and lasts for approximately 61.2 minutes at approximately 340 atm. Stages 8 to 12 are replicas of Stages 2 to 6. The 13th stage is a replica of the 7th stage. The total ethane to first plastic mass ratio is approximately 34, and the total extraction time is approximately 278 minutes. The contaminated ethane is devolatilized to leave 3.5 g extracted from the first plastic and ∼97.2 g of a purer plastic. The types of chemical contaminants typically present in recycled materials in the purer plastic are analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 13. The purer plastic is significantly cleaner than the severely contaminated feed material. Except for dioxins and bisphenol A, the chemical contaminants are removed almost to the LOQ. For the contaminant 4-tert-amylphenol, the removal efficiency is approximately 97%. For the contaminant bisphenol A, the removal efficiency is 89%. For the contaminant OCDD, the removal efficiency > 99.7%. For PCB 118, the removal efficiency > 93%. For di-2-ethylhexyl phthalate, the removal efficiency > 99.8%. The average removal capacity for the contaminants 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate is greater than approximately 96%.

[0278] Table 14

[0279] Purify post - consumer (PH) film #1 using both surface washing and overall purification involving packed leaching using DME in a packed bed Example 9 - Combination of surface washing by Cadel deinking and overall extraction involving packed leaching using post - consumer film #1 and DME in a packed bed 。

[0280]

[0281]

[0282] Table 9 Purify post - consumer (PC) film #1 using both surface washing and overall purification involving packed leaching using DME in a packed bed 。

[0283] Feed a first plastic material composed of a purer membrane from Comparative Example 3B to the following overall purification step involving packed leaching extraction (Phasex Corporation, 125 Flagship Drive, North Andover, MA). Load approximately 101.5 g of the first plastic into a 500 mL high-pressure packed bed extractor. The surface area to volume ratio of the first plastic is ~80 mm-1. At all times, the mass of DME in the packed bed is less than about 4:1 with respect to the mass of the first plastic. Conduct the extraction at 70 °C and a pressure of 238 atm, introducing DME into the packed bed at a rate of ~26 g / min for a total of 37 minutes (DME to first plastic ratio ~9.5:1), followed by holding for one hour with no additional DME added, and then another stage involving a feed rate of ~26 g / min (DME to first plastic ratio ~15.8:1) for 62 minutes. Thus, the final solvent to polymer ratio is ~25:1 and the extraction time is 160 minutes. Collect the purer plastic with a mass of ~98.0 g and a contaminant residue of ~3.5 g. Analyze the types of chemical contaminants commonly present in recycled materials in the purer plastic using the method disclosed in Part IX by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany), as shown in Table 14. The purer plastic is significantly cleaner than the original heavily contaminated post-consumer material and cleaner than the surface-washed version. Most chemical contaminants are reduced to below the LOQ. Although the starting levels are as high as ~1700X, all chemical contaminants are reduced to levels below about 10X LOQ. For the contaminant 4-tert-amylphenol, the removal efficiency is approximately 99%. For the contaminant bisphenol A, the removal efficiency > 99.3%. For the contaminant OCDD, the removal efficiency > 99.7%. For PCB 118, the removal efficiency > 94%. For di-2-ethylhexyl phthalate, the removal efficiency > 99.9%. The average removal efficiency of the contaminants 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate is greater than about 98%.

[0284] Example 10 - Combination of surface washing by Cadel deinking and overall purification involving packed leaching using post - consumer film #1 and DME in a packed bed

[0285] Table 16 Purify post - consumer (PH) film #1 using both surface washing and overall purification involving packed leaching using DME in a packed bed

[0286]

[0287]

[0288] Example 11 - Combination of surface washing and overall extraction involving submerged packed leaching using ethyl acetate in a Hildebrand extractor IX. Methods

[0289] First, the same first plastic material as that ground in Comparative Example 3 was pelletized using a single-screw extruder operating at ~190 °C. Then the pellets were ground using a cryogenic grinder to produce ground pellets with a mass average diameter of ~1 mm. Thus, the surface area to volume ratio of the first plastic was ~6 mm-1. The first plastic was fed into the following integral purification step involving packed leaching (Phasex Corporation, 125 Flagship Drive, North Andover, MA). Approximately 119.0 g of the first plastic was loaded into a high-pressure 500 mL packed bed extractor. At all times, the mass of DME in the packed bed was less than about 4:1 with respect to the mass of the first plastic. Extraction was carried out at 70 °C and a pressure of 27 atm, with DME introduced into the packed bed at a rate of ~26 g / min for 34 minutes (DME to first plastic ratio of ~7.3:1), followed by holding for 60 minutes, and then another stage at ~26 g / min for 56 minutes (DME to first plastic ratio of ~12.2:1). Thus, the total feed of DME to the first plastic was ~20:1, and the total extraction time was ~150 minutes. The purer plastic was collected and had a mass of 116.7 g, with ~2.3 g of contaminants remaining. The types of chemical contaminants typically present in recycled materials in the purer plastic were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 15. For the contaminant 4-tert-amylphenol, the removal efficiency was approximately 96.5%. For the contaminant bisphenol A, the removal efficiency > 91.2%. For the contaminant OCDD, the removal efficiency > 93.7%. For PCB 118, the removal efficiency > 98.1%. For di-2-ethylhexyl phthalate, the removal efficiency > 89.8%. The average removal capacity for the contaminants 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate was greater than about 93.9%.

[0290] ​

[0291] ​ ​

[0292]

[0293]

[0294] ​ ​ 。

[0295] The purer plastic from Comparative Example 4 was granulated using a single-screw extruder operating at ~190 °C. The resulting granules were cryogenically milled to a mass average particle size of ~1 mm. Thus, the surface area to volume ratio of the first plastic was ~6 mm-1. The first plastic was fed to an integral purification involving packed leaching (Phasex Corporation, 125 Flagship Drive, North Andover, MA) in a packed bed with a total volume of 500 mL. Approximately 117.9 g of the first plastic was loaded into a high-pressure packed bed extractor. At all times, the mass of DME in the packed bed was less than about 4:1 with respect to the mass of the first plastic. The extraction was carried out at 70 °C and a pressure of 27 atm, with DME introduced into the packed bed at a rate of ~26 g / min for 30 minutes (DME to first plastic ratio ~7.4:1), followed by a hold for 60 minutes, and then another stage at ~26 g / min for 56 minutes (DME to first plastic ratio ~12.3:1). Thus, the total feed of DME to the first plastic was ~19.7, and the total extraction time was ~150 minutes. The purer plastic was collected with a mass of 116.7 g, and the mass of the collected contaminants was ~1.2 g. The types of chemical contaminants typically present in recycled materials in the purer plastic were analyzed by GALAB Laboratories GmbH (Am Schleusengraben 7, 21029 Hamburg, Germany) using the method disclosed in Part IX, as shown in Table 15. For the contaminant 4-tert-amylphenol, the removal efficiency was approximately 99%. For the contaminant bisphenol A, the removal efficiency was 97.9%. For the contaminant OCDD, the removal efficiency >99.7%. For PCB 118, the removal efficiency >93%. For di-2-ethylhexyl phthalate, the removal efficiency >99.9%. The average removal capacity for the contaminants 4-tert-amylphenol, bisphenol A, OCDD, PCB 118, and di-2-ethylhexyl phthalate was greater than about 98%.

[0296] ​

[0297] ​ ​

[0298]

[0299]

[0300] ​ ​ 。

[0301] A first plastic material comprising shredded contaminated post-consumer film having a surface area to volume ratio greater than about 50 mm-1 is fed into a surface purification step that includes an aqueous surface wash step while applying vigorous mechanical agitation for ~30 min; wherein said surface wash step results in greater than about 80% of the loosely bound surface contamination. The resulting material is then conveyed at 70 °C and atmospheric pressure to a Hildebrand immersion packing leaching extractor using ethyl acetate as the packing leaching solvent. The ratio of ethyl acetate to the first plastic is about 40:1 and the average total extraction time is about 120 minutes. At any point in time in the Hildebrand extractor, the mass ratio of ethyl acetate in contact with the first plastic is less than about 5:1. The plastic from the extractor is devolatilized using mechanical cyclone action and then conveyed to an exhaust single screw extruder where the material is melted, devolatilized and melt filtered. The contaminated solvent from the extractor is purified using packed bed adsorption; wherein said contaminated solvent is distilled every 10 times and said solvent has been purified using packed bed adsorption. The resulting molten material is formed into pellets and quenched with water or air. The resulting pellets are a purer plastic. The average removal capacity for the contaminants 4-tert-amylphenol, bisphenol A, OCDD, PCB 118 and di-2-ethylhexyl phthalate is greater than about 55%.

[0302] ​

[0303] 1. The following methods are used for the analysis and measurement of various chemical pollutants. Pesticides: The Modular QuEChERS method of EN 15662:2018-07 is applied. For alkylphenol ethoxylates, alkylphenols, and bisphenols, the following technique is applied: The sample is cut, homogenized, and weighed; then, an internal standard (deuterated bisphenol A) is added, and then the sample is extracted with hexane at room temperature, derivatized with MSTFA (N-methyl-N-(trimethylsilyl)trifluoroacetamide), and the pollutant levels are determined by GC-MSD. For dioxins, furans, and PCBs: The method of ISO / IEC 17025:2005 is applied. The sample is cut into small pieces, a 13C / 12C-labeled PCDD / F internal standard is added to an aliquot of the sample material, the matrix is extracted and destroyed with hexane and H2SO4 for 1 hour, re-extracted with hexane (3 times for 30 min), multi-step chromatographic cleaning is applied, a 13C / 12C-labeled PCDD / F recovery standard is added to the measurement solution, and quantification is performed by an internal-labeled PCDD / F standard (isotope dilution technique and internal standard technique). For organotin: The method follows the EDANA protocol (WSP 351) for organotin compounds in absorbent hygiene products and their constituent raw materials. More specifically, the sample is extracted with ethanol containing sodium diethyldithiocarbamate solution, alkylated with sodium tetraethylborate, and transferred to the organic phase by extraction with hexane. Then, the tetra-substituted organotin compounds are separated by capillary gas chromatography and demonstrated using AED or MS as the detector. GC-ICP-MS is used as the detector system for organometallic analysis. For phthalates: The sample is cut, homogenized, and weighed. Then, an internal standard is used and the sample is extracted with hexane at room temperature. Then, the extracted phthalates are identified and quantified by GC-MSD. For PAH: The sample is cut, homogenized, and weighed. Then, an internal standard of deuterated PAH is added, and the sample is extracted with hexane. The extracted PAH is purified with silica gel, concentrated, and then characterized by GC-MSD.

[0304] 2. The amount of loosely bound surface contamination is determined by the following method: Approximately 20 g of plastic is added to a 1,000 mL round-bottom flask. Approximately 300 mL of distilled water is added to the 1,000 mL round-bottom flask. The round-bottom flask is capped and then shaken vigorously for approximately 60 seconds. The water is decanted from the flask. Approximately 600 mL of additional distilled water is added to the 1,000 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 dried overnight at 60 °C in a convection oven. The percentage change in the mass of the plastic is the amount of loosely bound surface contamination.

[0305] 3. Color measurements were obtained using a Minolta spectrophotometer, model CM580d. The “white” portion of the Leneta card was 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 were made using a D65 light source and a 10° observer. A minimum of three measurements were made for each sample in the compressed thermoplastic starch composition samples. The L, a, b values were averaged and reported along with the ΔE values. The ΔE value for 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.

[0306] The above description is given for clarity of understanding only and should not be construed as an undue limitation therefrom, as modifications within the scope of the invention will be apparent to those of ordinary skill in the art.

[0307] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm”.

[0308] Each document cited herein, including any cross-referenced or related patent or application, is incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any one or more other references, teaches, suggests, or discloses any such invention. Further, when 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 the term in this invention shall govern.

[0309] Although specific embodiments of the invention have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is intended that all such changes and modifications that fall within the scope of the invention be covered by the appended claims.

Claims

1. A method for extracting contaminants from a first plastic to produce a purer plastic, the method comprising: a. providing a first plastic containing individual contaminants, each individual contaminant having a certain concentration; b. using a leaching solvent in an extraction stage at a certain temperature and pressure to extract the individual contaminants from the first plastic for a period of time and each stage for a period of time to produce a purer plastic containing individual contaminants each having a certain concentration; wherein the extraction is packed leaching, wherein the temperature is lower than the initial melting point of the first plastic; wherein the extraction stage is carried out at a mass ratio of leaching solvent to first plastic; wherein the mass ratio of leaching solvent to first plastic at each stage and any point in time is less than 5:1; wherein the pressure is between atmospheric pressure and 1,000 atm; wherein the concentration of each individual contaminant in the purer plastic is lower compared to the concentration of each individual contaminant in the first plastic; and wherein the average reduction in the concentration of the first plastic contaminants relative to the reduced concentration of the purer plastic contaminants is at least 55% or LOQ, wherein the leaching solvent is THF, dimethyl ether, propane, ethane, hexane, propanol, diethyl ether, hexane, acetone, ethanol, methanol, propanol, isopropanol, MEK or ethyl acetate, wherein the contaminants of the first plastic include at least one of 4-tert-amylphenol, bisphenol A, OCDD, PCB 118 and bis(2-ethylhexyl) phthalate, and wherein the first plastic has a mass average surface area to volume ratio of at least 1 mm -1 .

2. The method according to claim 1, wherein the number of the stages is between 1 and 50.

3. The method according to claim 1 or 2, wherein the first plastic is a recycled plastic comprising at least one of post-industrial or post-consumer films.

4. The method according to claim 1 or 2, wherein the first plastic is surface-washed in a non-compact state by one or more surface washing methods before extraction, and wherein the one or more surface washing methods result in a reduction of more than 80% in loosely bound surface contamination; wherein the first plastic has a surface area to volume ratio of greater than 1 mm -1 before surface washing.

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

6. The method according to claim 1 or 2, wherein the period of time represented by the sum of the times of the individual packed leaching stages is less than 360 minutes.

7. The method according to claim 1 or 2, wherein the ratio of the total mass of the leaching solvent used in all stages to the mass of the first plastic is called the solvent ratio, and the solvent ratio is greater than 5:1 and less than 100:

1.

8. The method according to claim 1 or 2, wherein the leaching solvent is purified after the packed leaching or the one or more packed leaching stages to allow reuse in the packed leaching method by one or more solvent purification methods; wherein the one or more solvent purification methods include at least one stage of physical adsorption or absorption of chemical contaminants from the contaminated leaching solvent.

9. The method according to claim 1 or 2, wherein the first plastic is a recycled plastic, and the recycled plastic is at least one of post-industrial or post-consumer films.

10. The method according to claim 9, wherein the post-consumer film includes post-commercial and / or post-household films.

11. The method according to claim 1 or 2, wherein the packed leaching extraction is submerged leaching.

12. The method according to claim 11, wherein the leaching solvent completely fills the void volume in the first plastic.

13. The method according to claim 1 or 2, wherein the packed leaching extraction is percolation leaching.

14. The method according to claim 13, wherein the leaching solvent does not completely fill the void volume in the first plastic.

15. The method according to claim 1 or 2, wherein the leaching solvent is an organic solvent or a mixture of organic solvents.

16. The method according to claim 15, wherein the leaching solvent is at least one of an oxygen-containing solvent or a mixture thereof.

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