Waste polymer sorting and methods thereof

Abstract

A method of separating waste polymers includes removing magnetic materials from a plastic waste stream and shredding the plastic waste stream. The method further includes granulating the shredded plastic waste stream to form a plurality of granulated plastic waste particles and conveying the plurality of granulated plastic waste particles to a hydrocyclone to remove contaminants therefrom. The method further includes conveying the plurality of granulated plastic waste particles from the hydrocyclone to a float / sink tank apparatus configured to contain an aqueous separation solution and separating the plurality of granulated plastic waste particles into a first plurality of separated particles and a second plurality of separated particles. The method further includes collecting the second plurality of separated particles and conveying the second plurality of separated particles to a composition analysis unit. The method further includes performing a compositional analysis on the second plurality of separated particles.

Description

WASTE POLYMER SORTING AND METHODS THEREOFField of the Invention

[0001] The present disclosure relates to sorting waste plastic materials and methods thereof.Background of the Invention

[0002] Current separation methods and techniques used in managing plastic waste prior to recycling and reprocessing can have difficulties sorting materials of similar chemical and macromolecular compositions due to similar properties and chemical identifiers indicative of material classification. Additionally, certain analytical processes and sensing technologies struggle to analyze / differentiate materials having colorants or other additives (e g., near-infrared spectroscopy). Such processes are also costly and time intensive.

[0003] Thus, there is a need for separation techniques, processes, and sensing apparatuses / technologies capable of accurately / effectively sorting materials having similar chemical compositions and / or additive components.Summary of the Invention

[0004] In some embodiments, a method of separating waste polymers includes removing magnetic materials from a plastic waste stream and shredding the plastic waste stream to form a shredded plastic waste stream. The method further includes granulating the shredded plastic waste stream to form a plurality of granulated plastic waste particles and conveying the plurality’ of granulated plastic waste particles to a hydrocyclone to remove contaminants therefrom. The method further includes conveying the plurality of granulated plastic waste particles from the hydrocyclone to a float / sink tank apparatus configured to contain an aqueous separation solution and separating the plurality of granulated plastic waste particles into a first plurality' of separated particles and a second plurality of separated particles. The second plurality of separated particles has a specific gravity greater than the density of the aqueous separation solution. The method further includes collecting the second plurality of separated particles and conveying the second plurality of separated particles to a composition analysis unit. The composition analysis unit includes a conveyor and a plurality’ of sensors configured in communication with a computer. The method further includes performing a compositional analysis on the second plurality of separated particles.Brief Description of the Drawings

[0005] The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

[0006] FIG. 1 shows a flow diagram of the separation process implemented to separate plastic waste based upon material density.

[0007] FIG. 2 shows a flow diagram pertaining to the implementation of the composition analysis unit.Detailed Description

[0008] Plastic waste can be sourced from one or more operations such as material recovery facilities (MRFs), paper and plastic recyclers, landfills, molding operations, and others that handle scrap plastic materials. Plastic materials can include one or more of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyvinylchloride (PVC), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl acetate (PVA), acrylonitrile-butadiene-styrene (ABS) plastic, acrylonitrile-styrene-acrylate (ASA) plastic, polycarbonates (PC), various nylons, various epoxies, various polyurethanes, various polyureas, various polyesters, and other polymers, copolymers, or any combination(s) thereof used in packaging and product manufacture. In some embodiments, the plastic materials are mixed with other non-plastic materials, such as wire, used beverage cans, magnetic metal pieces, wood, paper, and other fiber materials, glass, wood waste, grit, and other inorganic matter. The plastic waste can vary' in size and shape to include films, thin sheets, and bulky items. The plastic content can vary’ widely depending on the source, such as about 10 wt% to about 70 wt%, such as about 25 wt% to about 60 wt%, such as about 35 wt% to about 55 wt%.

[0009] The plastic waste materials t pically arrive at waste recycling facilities in bales having various shapes, sizes, weights, and compositions. The size and weight can vary’ according to the source and type of baling device employed to compress and wrap the material. The composition of the bales can vary in physical form and content. Methods and processes described herein, as illustrated in FIG. 1, provide route(s) by which the contents of a plastic waste bales can be sorted based upon material composition, wherein differences in the material composition result in differing material densities. Such differences in density allow for material separation using a float / sink tank apparatus, whereby the contents of a plastic waste bale are sorted in accordance to the density inherently resulting from material composition.

[0010] As used herein, the term "specific gravity" refers to a ratio of the density7of a material to the density of pure water under the same conditions (e.g. , temperature, pressure). Thus, the specific gravity of pure water is defined as 1. In some embodiments, the specific gravity’ is a specific gravity at room temperature (e.g., 25 °C) and at atmospheric pressure. However, because specific gravity is a ratio, it is less sensitive than density to changes in conditions (e.g., temperature, pressure). Hence, in some embodiments described herein, the specific gravity’ is a specific gravity’ under working conditions.Plastic Material

[0011] Plastic waste bales of the present disclosure can contain a singular polymeric material and / or a combined assortment of polymeric materials. The polymeric material is selected from PE, PP, PS, PET, PVC, PMA, PMMA, PVA, ABS plastic, PC, various nylons, various epoxies, various polyurethanes, various polyureas, various polyesters, and other polymers, copolymers, or any combination(s) thereof, as implemented in the manufacture of mass produced consumer products and containers thereof. Furthermore, the shape, size, and mass of the waste plastics can vary depending upon the intended application for each individual piece.

[0012] In some embodiments, plastic waste bales can include one or more PE based polymers selected from ultra-high molecular weight polyethylene (UHMWPE), ultra-low molecular weight polyethylene (ULMWPE), high molecular weight polyethylene (HMWPE), high density polyethylene (HDPE), medium density polyethylene (MDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE). very-low density polyethylene (VLDPE), or combinations thereof.

[0013] In some embodiments, the plastic waste bale includes PE and / or copolymer(s) thereof, in an amount of about 2 wt% to about 98 wt%. Typically, the PE has a density (as determined by ASTM 1505) of about 0.975 g / cm3to about 0.90 g / cm3, such as about 0.94 g / cm3to about 0.915 g / cm3, such as about 0.935 g / cm3to about 0.93 g / cm3.

[0014] In some embodiments, the PE contained within the plastic waste bale includes a PE copolymer derived from propylene and one or more comonomers selected from ethylene, 1 -butene, 1-hexene, 1-octene, 4-methyl-l -pentene, and any combination thereof. By incorporating these comonomers, linear polymer molecules having short-chain branches along the polymer backbone are produced.

[0015] In some embodiments, the PE copolymer includes a backbone architecture of at least one of a random copolymer, a block copolymer, an alternating copolymer, or a gradient copolymer. In one or more embodiments, the PE copolymer is a random copolymer. In one or more embodiments, the PE copolymer contains up to 25 weight percent of a comonomer. In particular, the PE copolymer may contain 0.01 to 25 weight percent of a comonomer and have a density as low as 0.89 g / cm3.

[0016] In some embodiments, the PE copolymer has a density (as determined by ASTM 1505) of about 0.975 g / cm3to about 0.89 g / cm3, such as about 0.94 g / cm3to about 0.915 g / cm3, such as about 0.935 g / cm3to about 0.93 g / cm3.

[0017] In some embodiments, the plastic waste bale includes PP, and / or copolymer(s) thereof, in an amount of about 1 wt. % to about 10 wt. %, such as about. Typically, the PP has a density (asdetermined by ASTM D792) of about 0.875 g / cm3to about 0.925 g / cm3, such as about 0.89 g / cm3to about 0.92 g / cm3, such as about 0.89 g / cm3to about 0.91 g / cm3, such as about 0.9 g / cm3.

[0018] In some embodiments, the PP contained within the plastic waste bale includes a PP copolymer derived from propylene and one or more comonomers selected from ethylene, 1 -butene, 1 -hexene, 1 -octene, 4-methyl-l -pentene, and any combination thereof. By incorporating these comonomers, linear polymer molecules having short-chain branches along the polymer backbone are produced. In some embodiments, the comonomer unit of the PP copolymer accounts for about 0.01 to 25 weight percent of the PP copolymer.

[0019] In some embodiments, the PP copolymer includes a backbone architecture of at least one of a random copolymer, a block copolymer, an alternating copolymer, or a gradient copolymer. In one or more embodiments, the PP copolymer is a random copolymer.

[0020] In some embodiments, the PP copolymer has a density' (as determined by ASTM D792) of about 0.875 g / cm3to about 0.925 g / cm'. such as about 0.89 g / cm' to about 0.92 g / cm3, such as about 0.89 g / cm3to about 0.91 g / cm3, such as about 0.9 g / cm3.

[0021] In at least one embodiment, the waste PP and / or copolymer(s) thereof include one or more filler materials, such as any one or more pigments, reinforcing agents, ultra-violet (UV) stabilizers, and the like. As such, the filled PP has a density (as determined by ASTM D792) of about 0.95 g / cm3to about 1.2 g / cm3, such as about 0.97 g / cm3to about 1.17 g / cm3, such as about 1 g / cm3to about 1.1 g / cm3.Separation Process

[0022] One or more plastic waste bales is transported to an intake facility', wherein the components of the bales are to be sorted based upon their molecular composition, as shown in FIG. 1. The polymenc waste feedstock (line 102) typically is presented in bales held together by retainer bands. In a typical operation, the retainer bands are cut and the bale is pulled apart for initial visual inspection 100. Such process can be done manually or by a machine as determined by the operator. If any non-film objects are initially seen in the polymeric waste feedstock (line 102), such objects are removed either manually or by machine.

[0023] The unbaled waste plastic is then transported by a conveyor apparatus to a metal detection apparatus 104 to facilitate removal of certain forms of metal materials. In some embodiments, the metal detection apparatus 104 can include an induction metal detector having a plurality of magnets to detect and assist in removal of magnetic materials from the polymeric waste feedstock (line 102)without the need for process intervention. In at least one embodiment, the plurality of magnets can include one or more independent forms of magnets, such as an electromagnet. Additionally or alternatively, the plurality' of magnets can be disposed throughout the metal detection apparatus 104 at one or more appropriate distances such that the polymeric wastefeedstock (line 102)can be conveyed through the metal detection apparatus 104 in a continuous process where magnetic materials can be continuously detected and removed from the polymeric waste feedstock (line 102).

[0024] The polymeric waste feedstock 102 is then conveyed from the metal detection apparatus 104 to a shredder 106, for example a Vecoplan or Wiema shredder, that is configured to tear / shred the polymeric waste feedstock (line 102)into chunks and pieces which are then discharged through a sorting screen. The sorting screen separates the shredded chunks and pieces of the polymeric waste feedstock (line 102)according to their size, which may vary depending upon operational requirements. In some embodiments, a sorting screen has a plurality of openings each having a 3- inch diameter, such as a plurality of openings each having a I -inch diameter, such as a plurality of openings each having a 0.5-inch diameter.

[0025] The shredded polymeric waste feedstock (line 102)is then conveyed to a wash and transport screw 108. The wash and transport screw 108 wets and conveys the shredded polymeric waste feedstock (line 102)to a float / sink tank apparatus 110 containing an aqueous separation solution (e.g., water). While in the float / sink 110 apparatus, further separation of high density materials not recognized by the metal detection apparatus 104, for example stone, glass, sand, or other waste polymers having a specific gravity higher than the density of the aqueous separation solution, sink to the bottom of the float / sink apparatus 110 for later removal. While in the float / sink tank apparatus 110 the polymeric waste feedstock (line 102)and aqueous separation solution are agitated by a series of rotating paddles to promote the separation of high density materials from the polymeric waste feedstock.

[0026] In some embodiments, the float / sink tank apparatus 110 can also serve to clean the polymeric waste feedstock (line 102)by adding one or more cleaning agents to the aqueous separation medium. Such cleaning agents can include one or more surfactants, detergents, or other cleaning agents known to one of ordinary skill in the art to remove substances such as, for example inks, adhesives, and the like from the polymeric waste feedstock (line 102).

[0027] After a predetermined amount of time, the polymeric waste feedstock (line 102)is conveyed from the float / sink tank apparatus 110 to a first granulator 112. The first granular 112 further reduces the size of the polymeric waste feedstock 102 received from the shredder 106 and sink / float tank 110 to form a plurality of granulated polymeric waste particles(line 114). In some embodiments, a granulated waste particle (line 114) has a size of less than 25 millimeters in at least one dimension.

[0028] From the first granulator 112, the granulated waste particles (line 114) are conveyed to a hydrocyclone apparatus 116, such as for example a hydrocyclone produced by Herbold Meckesheim. The hydrocyclone 116 operates under water pressure from a pump which moveswater in a spiral to further separate contaminants from the granulated waste particles 114 by rotational forces of the moving water within the hydrocyclone 116.

[0029] The granulated waste particles (line 114) leave the hydrocyclone 116 at its upper end with the main stream of water, with any sinking material (e.g. , higher density material) at the lower end. The granulated waste particles (line 114) are then conveyed and deposited into a second float / sink tank apparatus 118 containing an aqueous separation solution (e.g., water). The granulated waste particles (line 114) are immersed in the separation solution and agitated using one or more methods know to one of ordinary7skill in the art, such as use of paddlewheels, waterjets, and the like. The aqueous separation solution of the second float / sink tank apparatus 118 is configured such that the granulated waste particles (hne 114) are separated based upon the density of the materials, wherein higher density materials sink to the bottom of the float / sink tank apparatus 118 and lower density materials float on the aqueous separation solution.

[0030] Because the particles normally tends to float on the surface of the aqueous separation solution, the float / sink tank apparatus 118 is provided with agitation devices to not only move the particles within the float / sink tank apparatus 118 but also to immerse the particles, e.g., force the particles pieces under water, throughout its migration in the float / sink tank apparatus 118. In some embodiments, the bottom of the float / sink tank apparatus 118 includes a baffle honeycomb configured with vertical baffles and angled baffles. The angle of the baffles may be at an angle determined by the operator and adjacent baffles may be at different angles. The vertical baffles may be the same height or different adjacent heights. As water is moved in the float / sink tank apparatus 118 the baffle honeycomb causes turbulence in the water stream which agitates the floating particles.

[0031] Movement of the particles, and the water, in the float / sink tank apparatus 118 is facilitated by a paddlewheel which is in fluid communication with the water surface. The paddlewheel may be an emersion paddlewheel with a substantial portion of its structure below the water line of the float / sink tank apparatus 118. In addition to the paddlewheel, a number of surface paddlewheels may be coupled to the float / sink tank apparatus 118 to assist in movement of the water and the floating particles from one end of the tank to the other. In some embodiments, the paddlewheels may operate at the same or different rpms.

[0032] The granulated waste particles (line 114) are moved along the surface of the aqueous separation solution by current flow or in sequence to the propulsion of one or more paddlewheels and / or by a water spray system. Water jets of a water spray system are configured to provide sufficient force through a supply tube and a plurality of spray bars, to assist in propelling the granulated waste particles (line 114) throughout the float / sink tank apparatus 118, and provide an additional separation function by driving the granulated waste particles (line 114) under the surfaceof the aqueous separation solution to further facilitate separation by material density. The propelled floating granulated waste particles (line 114) are then discharged from the aqueous separation solution via a waterfall separator into a discharge auger conveying system which is configured to remove excess water and convey the semi-wet less dense first plurality of separated particles (line 119A) into a pair of turbo dryers 121A.

[0033] Additionally and / or alternatively, once the less dense materials have been separated and removed from the float / sink tank apparatus 118, the aqueous separation solution is drained therefrom in order to collect the second plurality of separated particles (line 119B) having a density greater than that of the aqueous separation solution.

[0034] Upon exiting the waterfall separator, the two groups of separated particles (line 119A and line 119B) are deposited in a first set of turbo dryers 121A and 121B, respectively, wherein the two groups of separated particles are maintained as such. The turbo dry ers 121A and 121B removes moisture from the separated particles (line 119A and line 119B, respectively), and through separate pneumatic transport systems 122A and 122B. the separated particles (line 119A and line 119B, respectively), are deposited in a second set of turbo dryers 123A and 123B. The second set of turbo dryers 123A and 123B removes additional moisture from the separated particles (line 119A and line 119B). In some embodiments, one or both of the turbo driers can incorporate a thermal drying apparatus which uses heat to remove additional moisture from the separated particles (line 119A and line 119B). The separated particles (line 119A and line 119B), now ty pically in the form of separate flakes, are conveyed to a composition analysis unit 124.

[0035] The composition analysis unit 124 can include any one or more sensors, known to one of ordinary skill in the art, that allow for rapid compositional identification of polymeric materials.

[0036] In some embodiments, the one or more sensors can include any one or more sensor systems utilizing irradiated or reflected electromagnetic radiation, such as infrared (IR) spectroscopy, Fourier transform IR (FTIR) spectroscopy, forward-looking IR (FLIR) spectroscopy, very near IR (VNIR) spectroscopy, near IR (NIR) spectroscopy, short wavelength IR (SWIR) spectroscopy, long wavelength IR (LWIR) spectroscopy, medium wavelength IR (MWIR) spectroscopy, x-ray transmission (XRT) spectroscopy, gamma ray spectroscopy, ultraviolet-visible light (UV-vis) spectroscopy, x-ray fluorescence (XRF), laser induced breakdown spectroscopy (LIBS), Raman spectroscopy, anti-stokes Raman spectroscopy, hyperspectral spectroscopy, acoustic spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, microwave spectroscopy, terahertz spectroscopy, and / or other type of sensor technology, including chemical or radioactive. In at least one embodiment, the compositional analysis unit includes an automated NIR sensor.

[0037] In some embodiments, the composition analysis unit 124 includes an NIR sensor, wherein light is emitted at a wavelength range from about 800 to 2500 nm. The NIR beam is directed ontothe separated particles (line 119A and / or line 119B) which then reflects the beam to a NIR light detector. In one or more embodiments, the NIR light detector is a scanning grating NIR spectrometer and / or a diode array NIR spectrometer. In at least one embodiment, the NIR light detector is a diode array NIR spectrometer. Without being bound by theory, it is believed that the diode array NIR spectrometer is capable of generating more spectra in a given time, thus allowing for more rapid sorting.

[0038] In instances wherein the separated particles (line 119A and / or line 119B) contain a colorant and / or are colored, NIR may not be a viable option for determining the relative composition of such particles. In which case, it desirable and / or necessary to incorporate multiple different sensor systems (e.g., NIR, XRF, and LIBS) within the composition analysis unit 124, as shown in FIG. 2. As such, the composition analysis unit 124 can include a conveyor 202 to convey the separated particles (line 119A and / or line 119B) through a plurality7of sensors 204, selected from any one or more sensors previously disclosed, wherein the plurality of sensors are in communication with a computer 206 through which the obtained data provides information corresponding to the composition of the separated particles (line 119A and / or line 119B).

[0039] Without being bound by theory7, the composition analysis unit 124 allows an operator to determine, approximately, the composition of the separated particles (line 119A and / or line 119B). If it is determined that the separated particles (line 119A and / or line 119B) include more than one composition at an unacceptable level, the separated particles (line 119A and / or line 119B) may then be reintegreated / retumed to the second float / sink tank apparatus 118 (via line 126A and / or 126B, respectively) and subjected to additional separation processes. However, the aqueous separation solution contained within the second float / sink tank apparatus 118 can be tuned such that the density of the aqueous separation solution allows for more defined separation of materials based upon such material density7. Thus, the second float / sink tank apparatus 118 is configured to further separate granulated waste particles of more closely related densities. Such separation and analysis are continually conducted until such separated particles (line 119A and / or line 119B) contain an acceptable composition for an intended purpose.

[0040] Upon and / or prior to compositional analysis and reintegration of the separated particles to the second float / sink tank apparatus 118 for additional separation processes, the density7of the aqueous separation solution can be tuned such that the separation process has higher degrees of selectivity7to provide sufficient separation of granulated waste particles 114.

[0041] Such tuning can be conducted through the addition of one or more aqueous soluble additives to the aqueous separation solution. In some embodiments, the one or more aqueous soluble additives can include a water-soluble salt, an alcohol, or combinations thereof. Without being bound by theory, it is worth noting that including water-soluble salts typically increase thedensity of the aqueous separation solution and including an alcohol typically decreases the density of the aqueous separation solution. In at least one embodiment, a water-soluble salt can include sodium chloride, potassium chloride, sodium bromide, potassium bromide, calcium chloride, calcium nitrate, potassium carbonate, or combinations thereof. In at least one embodiment, the water-soluble carbohydrate can include glucose, sucrose, lactose, fructose, or combinations thereof. In at least one embodiment, the alcohol is ethanol and / or isopropanol. In at least one embodiment, the water-soluble salt is sodium chloride (NaCl).

[0042] In some embodiments, the materials intended to be sorted and collected are separated particles (line 119A), having specific gravities less than the density of water and / or that of the aqueous separation solution. As such, the separated particles (line 119A) float in the float / sink tank apparatus 118 when such a separation solution is implemented. Thus, it is advantageous to formulate an aqueous separation solution having a suppressed density (e.g., ethanol and water) sufficient to float / sink separate the particles further to form a third plurality of separated particles (line 119C) and a fourth plurality of separated particles (line 119D). wherein separated particles (line 119C) has a specific gravity lower than the aqueous separation solution and separated particles (line 119D) has a specific gravity greater than the aqueous separation solution. As previously disclosed, the separation and analysis processes can be continually / repeatedly conducted until the waste plastic materials are adequately separated into distinct compositions based on material density’.

[0043] In some embodiments, the aqueous separation solution includes ethanol and water present in a weight ratio of about 99 parts ethanol to 1 part water to about 1 part ethanol to 99 parts water. Without being bound by theory, altering both the weight ratio of ethanol: water and the temperature at which the separation process is performed allows an operator greater control over the density of the aqueous separation solution, and thus more precise separation and sorting of particles derived from separated particles (line 119A).

[0044] As previously disclosed, the separation and analysis processes are continually / repeatedly conducted until such granulated waste particles contain an acceptable composition for an intended purpose. In one or more embodiments, compositions derived from separated particles (line 119A)include a weight ratio of PE:PP of about 99: 1 to about 90: 10.

[0045] In some embodiments, the materials intended to be sorted and collected are separated particles (line 119B). having specific gravities greater than the density of water and / or that of the aqueous separation solution. As such, the separated particles (line 119B) sink in the float / sink tank apparatus 118 when such a separation solution is implemented. Thus, it is advantageous to formulate an aqueous separation solution having a modified density (e.g, salt-water) sufficient to float / sink separate the particles further to form a fifth plurality of separated particles (line 119E)and a sixth plurality of separated particles (line 119F). wherein separated particles (line 119E) has a specific gravity lower than the aqueous separation solution and separated particles (line 119F) has a specific gravity greater than the aqueous separation solution. As previously disclosed, the separation and analysis processes can be continually / repeatedly conducted until the waste plastic materials are adequately separated into distinct compositions based on material density.

[0046] In some embodiments, the aqueous separation solution includes NaCl and water present in a w eight ratio of about 1 wt. % NaCl to about 25 wt. % NaCl. Without being bound by theory', altering both the weight ratio of NaCl: ater and the temperature at which the separation takes place allows an operator greater control over the density of the aqueous separation solution, and thus more precise separation and sorting of particles derived from separated particles (line 119B).

[0047] In some embodiments, the aqueous separation solution has a density of about 0.80 g / cm3to about 1.7 g / cm3.

[0048] As previously disclosed, the separation and analysis processes are continually / repeatedly conducted until such granulated waste particles, derived from separated particles (line 119B), contain an acceptable composition for an intended purpose, such as including only a singular polymer composition.Material reprocessing

[0049] In some embodiments, the collected composition of PE / PP particles can be used as a postconsumer resin (PCR). As such, the separated particles (lines 119A-F) are processed via any one or more methods known to one of ordinary skill in the art, such as blending in solution and / or in thermal processing. In some embodiments, melt screw' extrusion is implemented to form the PCR extrudate, which can then be further processed via pelletization to form a pelletized polymeric resin. Melt blending is one suitable method for preparing the final polymer blend of the present disclosure, although any suitable polymer blending techniques available to those of ordinary skill in the art may be used. Techniques for melt blending of a polymer with additives of all types are known to those of ordinary' skill the art and can typically be used with the present disclosure. In one type of melt blending operation useful with the present disclosure, the individual components of the blend are combined in a mechanical extruder or mixer, and then heated to a temperature sufficient to form a polymer melt.

[0050] The mechanical mixer can be a continuous or batch mixer. Examples of suitable continuous mixers include single screw extruders, intermeshing co-rotating twin screw extruders such as Wemer & Pfleiderer ZSK™ extruders, counter-rotating twin screw extruders such as those manufactured by Leistritz™, and reciprocating single screw kneaders such as Buss™ co-kneaders. Examples of suitable batch mixers are lateral 2-roll mixers such as Banbury ™ or Boling™ mixers. The temperature of the melt, residence time of the melt within the mixer, and the mechanical designof the mixer are several well-known variables that control the amount of shear to be applied to the composition during mixing, and can be readily selected by one of ordinary skill in the art based on the disclosure herein.

[0051] The PCR disclosed herein may be pelletized via strand pelleting or commercial underwater pelletization. Pellets of the polymeric resin may then be easily processed into shaped articles by injection molding, profile extrusion, blow molding, and other forming processes to give products which have well balanced properties suitable for commercial applications.

[0052] In at least one embodiment, pellets of the PCR are formed in a continuous process. As such, components of the PCR are fed into a continuous mixer, a single screw or twin screw extruder via volumetric or gravimetric feeders. The extruder is heated to a temperature sufficient to melt the polymers, for example between 150 °C and 250 °C. The components are fed into an extruder and mixed / blended together in a molten state. The extruder speed may be from about 20 to about 200 revolutions per minute (rpm). The gas from the extruder may be evacuated by a vacuum pump. The PCR extrudate is typically cooled (e.g., in a water bath or underwater pelletizer) and pelletized to form pellets of the polymeric resin.

[0053] In at least one embodiment, pellets of the PCR are formed in a batch process. As such, components of the polymeric resin are added to a mixing device, such as a Banbury mixer, and heated to a temperature sufficient to melt the polymer, such as about 150 °C to about 250 °C. The output from the mixer was cooled and pelletized to form pellets of the polymeric resin.

[0054] In one or more embodiments, the PCR has a density (as determined by ASTM 1505) of about 0.86 g / cm3to about 1.7 g / cm3.

[0055] Overall, the plastic waste bale sorting method(s) of the present disclosure can provide an efficient route to float / sink separation of granulated waste particles based on the specific gravity of the material relative to that of the aqueous separation solution. The method(s) disclosed herein provide an efficient and cost-effective pathway for which a wide variety of waste plastic compositions can be prepared, sorted, and processed via manipulating the density' of the aqueous separation solution and a series of continuous / repeated separation and analysis processes. The separated particles can then be recycled and processed into a PCR and used in the formation of new products.

[0056] The phrases, unless otherwise specified, "consists essentially of' and "consisting essentially of' do not exclude the presence of other steps, elements, or materials, whether or not, specifically mentioned in this specification, so long as such steps, elements, or materials, do not affect the basic and novel characteristics of the present disclosure, additionally, they do not exclude impurities and variances normally associated with the elements and materials used.

[0057] For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, within a range includes every point or individual value between its end points even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other low er or upper limit, to recite a range not explicitly recited.

[0058] All documents described herein are incorporated by reference herein, including any priority documents and or testing procedures to the extent they are not inconsistent with this text. As is apparent from the foregoing general description and the specific embodiments, while forms of the present disclosure have been illustrated and described, various modifications can be made without departing from the spirit and scope of the present disclosure. Accordingly, it is not intended that the present disclosure be limited thereby. Likewise, the term "comprising" is considered synonymous with the term “including’’ for purposes of United States laws Likewise whenever a composition, an element or a group of elements is preceded with the transitional phrase “comprising,” it is understood that we also contemplate the same composition or group of elements with transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “is” preceding the recitation of the composition, element, or elements and vice versa.

[0059] While the present disclosure has been described with respect to a number of embodiments and examples, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope and spirit of the present disclosure.

Claims

CLAIMS1. A method of separating waste polymers, the method comprising: removing magnetic materials from a plastic waste stream; shredding the plastic waste stream to form a shredded plastic waste stream; granulating the shredded plastic waste stream to form a plurality of granulated plastic waste particles; conveying the plurality of granulated plastic waste particles to a hydrocyclone to remove contaminants therefrom; conveying the plurality of granulated plastic waste particles from the hydrocyclone to a float / sink tank apparatus configured to contain an aqueous separation solution; separating the plurality of granulated plastic waste particles into a first plurality of separated particles and a second plurality' of separated particles, wherein the second plurality of separated particles has a specific gravity greater than the density of the aqueous separation solution; collecting the second plurality of separated particles; conveying the second plurality' of separated particles to a composition analysis unit, the composition analysis unit comprising a conveyor and a plurality of sensors configured in communication with a computer; and performing a compositional analysis on the second plurality of separated particles.

2. The method of claim 1, wherein the plastic waste stream comprises one or more materials selected from the group consisting of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyvinylchloride (PVC), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl acetate (PVA), acr lomtrile-butadiene-styrene (ABS) plastic, acrylonitrile-styrene-acrylate (ASA) plastic, polycarbonates (PC), or combinations thereof.

3. The method of claim 1. wherein the aqueous separation solution comprises water.

4. The method of claim 1, wherein the first plurality of separated particles has a specific gravity less than the density of the aqueous separation solution.

5. The method of claim 1, wherein the plurality' of sensors comprises any one or more sensor systems selected from the group consisting of infrared (IR) spectroscopy, Fourier transform IR (FTIR) spectroscopy, forward-looking IR (FLIR) spectroscopy, very near IR (VNIR) spectroscopy, near IR (NIR) spectroscopy, short wavelength IR (SWIR) spectroscopy, long wavelength IR (LWIR) spectroscopy, medium wavelength IR (MWIR) spectroscopy, x-ray transmission (XRT) spectroscopy, gamma ray spectroscopy, ultraviolet-visible light (UV-vis) spectroscopy, x-ray fluorescence (XRF), laser induced breakdown spectroscopy (LIBS), Ramanspectroscopy, anti-stokes Raman spectroscopy, hyperspectral spectroscopy, acoustic spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, microwave spectroscopy, terahertz spectroscopy, or combinations thereof.

6. The method of claim 1, wherein the plurality of sensors comprises at least one near IR (NIR) sensor, at least one x-ray fluorescence (XRF) sensor, and at least one laser induced breakdown spectroscopy (LIBS) sensor.

7. The method of claim 1, wherein performing a compositional analysis on the second plurality of separated particles comprises conveying the separated particles through the plurality of sensors.

8. The method of claim 1, wherein collecting the second plurality of separated particles further comprises: draining the aqueous separation solution from the float / sink tank apparatus; depositing the second plurality of separated particles into a first turbo dryer to remove moisture from the second plurality of separated particles; transporting the second plurality of separated particles through a pneumatic transport system from the first turbo dr er to a second turbo dryer, the second turbo dryer configured to remove additional moisture from the first plurality of separated particles; and conveying the second plurality of separated particles from the second turbo dryer to the composition analysis unit.

9. The method of claim 8, the method further comprising: conveying the second plurality of separated particles to a second float / sink tank apparatus, wherein the second float / sink tank apparatus is configured to contain a second aqueous separation solution; separating the second plurality of separated particles into a third plurality of separated particles and a fourth plurality of separated particles; collecting the fourth plurality of separated particles; conveying the fourth plurality of separated particles to the composition analysis unit; and performing a compositional analysis on the fourth plurality of separated particles.

10. The method of claim 9, wherein the density of the second aqueous solution is greater than the density of the first aqueous solution.

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