Lldpe and LDPE sorting and methods thereof

Abstract

In some embodiments, a method of separating waste polymers includes conveying a plastic waste stream to a metal detection apparatus and conveying the plastic waste stream from the metal detection apparatus to a shredder. The method further includes conveying the shredded plastic waste stream to a first float / sink tank apparatus and separating the shredded plastic waste stream into a first plurality of plastic waste and a second plurality of plastic waste. The method further includes conveying the first plurality of plastic waste to a first granulator and conveying the plurality of granulated plastic waste particles to a hydrocylone. The method further includes conveying the plurality of particles from the hydrocylone to a second float / sink tank apparatus 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 first plurality of separated particles.

Description

LLDPE AND LDPE 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] Currently, various technologies exist to manage and / or eliminate plastic waste. Waste recycling / reprocessing has gained considerable interest due to the large feedstock of such materials produced as a byproduct of consumer demand. However, reprocessing materials of different chemical and macromolecular compositions can have unintended consequences, e.g., gelation, crystallization, and phase separation. Thus, standard recycling processes including sorting steps to separate plastic waste materials in terms of their chemical and macromolecular compositions.

[0003] However, while there exist multiple different sorting processes, they are not without their own inherent drawbacks (e.g, costly and time intensive). In addition, sorting materials of similar chemical and macromolecular compositions (e.g., high density polyethylene, low density polyethylene, and linear low density polyethylene) is often difficult, due to similar properties and chemical identifiers indicative of material classification.

[0004] Thus, there is a need to develop separation techniques and processes capable of identifying and sorting materials of similar chemical and macromolecular compositions.Summary of the Invention

[0005] The present disclosure relates to sorting waste plastic materials and methods thereof.

[0006] In some embodiments, a method of separating waste polymers includes conveying a plastic waste stream to a metal detection apparatus, wherein the metal detection apparatus is configured to remove magnetic materials. The method further includes conveying the plastic waste stream from the metal detection apparatus to a shredder, wherein the shredder is configured to tear / shred the plastic waste stream to form a shredded plastic waste stream. The method further includes conveying the shredded plastic waste stream to a first float / sink tank apparatus, the first fl oat / sink tank apparatus configured to contain a first aqueous separation solution. The method further includes separating the shredded plastic w aste stream into a first plurality of plastic w aste and a second plurality of plastic waste. The method further includes conveying the first plurality of plastic waste to a first granulator to form a plurality of granulated plastic waste particles. The method further includes conveying the plurality of granulated plastic waste particles to a hydrocylone to remove contaminates therefrom. The method further includes conveying the plurality of granulated plastic waste particles from the hydrocylone to a second float / sink tank apparatus, wherein the second float / sink tank apparatus is configured to contain a second aqueous separation solution. The method further includes separating the plurality of granulated plasticwaste particles into a first plurality of separated particles and a second plurality of separated particles. The method further includes collecting the first plurality of separated particles.Brief Description of the Drawings

[0007] 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.

[0008] FIG. 1 shows a flow diagram of the separation process implemented to separate plastic waste based upon material density.Detailed Description

[0009] 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, but are not limited to, one or more of high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyvinylchloride (PVC), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl acetate (PVA), acrylonitrile-butadiene-styrene (ABS) plastic, 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%.

[0010] The plastic waste materials typically 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 vary7in 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, as for example separating LDPE from LLDPE. In some embodiments, processes described herein utilize differences in material densities to separate materials having different compositions. 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.

[0011] As used herein, the term "specific gravity" refers to a ratio of the density of 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.LDPE and LLDPE

[0012] Plastic waste bales of the present disclosure can contain a singular polymeric material and / or a combined assortment thereof. The polymeric material is selected from HDPE, LDPE, LLDPE, PP, PS, PET, PVC, PMA, PMMA, PVA, ABS plastic, 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. In some embodiments, the plastic waste bales include varying amounts of LDPE and LLDPE.

[0013] In some embodiments, the plastic waste bale includes LLDPE, and / or copolymer(s) thereof, in an amount of about 2 wt% to about 98 wt%. Typically, the LLDPE has a density' (as determined by ASTM 1505) of about 0.90 g / cm3to about 0.94 g / cm3, such as about 0.9 g / cm3to about 0.92 g / cm3, such as about 0.9 g / cm3to about 0.915 g / cm3. In some embodiments, the LLDPE has a melt index (as determined by ASTM D-1238; 190 °C with a 2.16 kg load) of about 0.2 g / 10 min to about 20 g / 10 min, such as about 0.5 g / 10 min to about 5 g / 10 min, such as about 1 g / 10 min to about 5 g / 10 min.

[0014] In some embodiments, the LLDPE contained within the plastic waste bale includes a LLDPE copolymer derived from ethylene and one or more comonomers selected from propylene, 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 LLDPE copolymer accounts for about 5 wt% to about 25 wt% of the polymer.

[0015]

[0016] In some embodiments, the plastic waste bale includes LDPE, and / or copolymer(s) thereof, in an amount of about 2 wt% to about 98 wt%. Typically, the LDPE has a density (as determined by ASTM 1505) of about 0.915 g / cm3to about 0.935 g / cm3, such as about 0.925 g / cm3to about 0.935 g / cm3, such as about 0.925 g / cm3to about 0.93 g / cm3. In some embodiments, the LDPE has a melt index (as determined by ASTM D-1238; 190 °C with a 2.16 kg load) of about 0.2 g / 10 minto about 20 g / 10 min, such as about 1 g / 10 min to about 10 g / 10 min. such as about 5 g / 10 min to about 10 g / 10 min.

[0017] In some embodiments, the LDPE contained within the plastic waste bale includes a LDPE copolymer derived from ethylene and one or more comonomers selected from propylene, 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 LDPE copolymer accounts for about 5 wt% to about 25 wt% of the polymer, such as about 0.01 wt% to about 15 wt%, such as about 0.01 wt% to about 5 wt%.Separation Process

[0018] 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 polymeric 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.

[0019] 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 waste feedstock (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 102.

[0020] The polymeric waste feedstock (line 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 w aste feedstock (line 102) according to their size, which may vary depending upon operational requirements. In some embodiments, a sorting screen has a plurality' of openingseach having a 3-inch diameter, such as a plurality of openings each having a 1-inch diameter, such as a plurality of openings each having a 0.5-inch diameter.

[0021] 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.

[0022] 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 know 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).

[0023] 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 about 25 millimeters or less in at least one dimension. In some examples, the granulated waste particle has a size of less than 100 microns. In some embodiments, the plurality of granulated waste particles 113 has an average size of about 10 to 15 millimeters.

[0024] 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 moves water in a spiral to further separate contaminates from granulated waste particles (line 114) by rotational forces of the moving water within the hydrocyclone 116.

[0025] The granulated waste particles (line 114) leave the hydrocyclone 116 at its upper end with the mainstream 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. The granulated waste particles (line 114) are immediately immersed in the separation solution and agitated using one or more methodsknow to one of ordinary skill in the art. such as 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 (line 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.

[0026] 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 flakes of particles.

[0027] Movement of the flakes, 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 flakes of particles from one end of the tank to the other. In some embodiments, the paddlewheels may operate at the same or different RPMs.

[0028] 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 surface of 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 separated particles (line 119) into a pair of turbo dryers 120.

[0029] Upon exiting the waterfall separator, the separated particles (line 119) are deposited in a first turbo dryer 121. The turbo dryer 121 removes moisture from the granulated waste particles(line 114) and through a pneumatic transport system 122 deposits the PC particles in a second turbo dryer 123. The second turbo dryer 123 removes additional moisture from the separated particles (line 119). 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 119). The separated particles (line 119), now typically in the form of separate flakes, are conveyed to a composition analysis unit 124.

[0030] The composition analysis unit 124 can include any one or more sensors, known to one of ordinary' skill in the art, which allow for rapid compositional identification of polymeric materials.

[0031] In some embodiments, the one or more sensors can include any one or more sensor systems utilizing irradiated or reflected electromagnetic radiation such as, but not limited to 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 any other type of sensor technology, including but not limited to, chemical or radioactive. In at least one embodiment, the compositional analysis unit includes a FTIR sensor.

[0032] FTIR is widely utilized as a rapid analytical tool to identify the type of short chain branching (SCB) in LLDPE. Prasad et al. (Poly. Eng. Sci. 1998, 38 (10), 1716-1728.) discloses a method by which LLDPE and LDPE a-olefm blends can be qualitatively and rapidly analyzed by FTIR spectroscopy over the entire blend composition range. Prasad et al. is incorporated herein by reference in its entirety. Without being bound by theory', ethyl, butyl, and hexyl ty pe SCB in LLDPEs are readily distinguishable by methyl deformation and rocking bands (1377-1379 cm’1and 886-894 cm’1, respectively). The absorption bands at 887 cm’1, 894 cm’1, and 889 cm’1can be used to identify butane-1, hexane-1, and octane-1 copolymers in blends having, at least, 20 wt% LLDPE.

[0033] Without being bound by theory, the compositional analysis unit 124 allow s an operator to determine, approximately, the composition of the separated particles (line 119). If it is determined that the separated particles (line 119) include more than one composition at an unacceptable level, the separated particles (line 119) may then reintegrated / retumed to the second float / sink tank apparatus 118 (via line 126) and subjected to additional separation processes. However, the aqueous separation solution contained within the second float / sink tank apparatus 118 can be tunedsuch that the density of the aqueous separation solution allows for more defined separation of materials based upon such material density. 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 119) contain an acceptable composition for an intended purpose.

[0034] 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 density of the aqueous separation solution can be tuned such that the separation process has higher degrees of selectivity to provide sufficient separation of granulated waste particles 114.

[0035] 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, a water-soluble, an alcohol, or combinations thereof. 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.

[0036] In some embodiments, the materials intended to be sorted and collected are granulated waste particles (line 114) and / or separated particles (line 119) of LLDPE and LDPE having specific gravities less than the density of water and / or that of the aqueous separation solution. As such, particles of both LLDPE and LDPE 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 LLDPE particles from the LDPE particles.

[0037] In some embodiments, the aqueous separation solution includes ethanol and w ater present in a weight ratio of about 10: 1 to about 1: 10 at a temperature of about 10 °C to about 40 °C. Without being bound by theory, altering both the weight ratio of ethanol: water 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 LLDPE and LDPE. In some embodiments, the ethanol in the separation solution is about 0.01 wt% to about 99.9 wt% of the separation solution, such as about 10 wt% to about 90 wt%, such as about 25 wt% to about 75 wt%, such as about 40 wt% to 60 wt%, such as about 45 wt% to about 55 wt%. In one or more alternative embodiments, the ethanol in the separation solution is about 0.01 wt% to about 10 wt % of the separation solution, alternatively about 10 wt% to about 25 wt%, alternatively about 25 wt% to about 40 wt%, alternatively about 40 wt% to about 45 wt%, alternatively about 55 wt% toabout 60 wt%, alternatively about 60 wt% to about 75 wt%, alternatively about 75 wt% to about 99.9 wt%. In some embodiments, the aqueous separation solution is maintained at a temperature of about 10 °C to about 40 °C, such as about 15 °C to about 35 °C, such as about 20 °C to about 30 °C. In such instances, the aqueous separation solution is maintained at such a temperature throughout the duration of the float / sink separation process.

[0038] In some embodiments, the aqueous separation solution has a density of about 1 g / cm3to about 0.8 g / cm3, such as about 0.95 g / cm3to about 0.85 g / cm3, such as about 0.93 g / cm3to about 0.87 g / cm3, such as about 0.93 g / cm3to about 0.9 g / cm3, such as about 0.925 g / cm3to about 0.92 g / cm3. In one or more alternative embodiments, the aqueous separation solution has a density of about 1 g / cm3to about 0.95 g / cm3, alternatively about 0.95 g / cm3to about 0.93 g / cm3, alternatively about 0.93 g / cm3to about 0.925 g / cm3, alternatively about 0.92 g / cm3to about 0.9 g / cm3, alternatively about 0.9 g / cm3to about 0.87 g / cm3, alternatively about 0.87 g / cm3to about 0.85 g / cm'. alternatively about 0.85 g / cm3to about 0.8 g / cm~.

[0039] As previously disclosed, the separation and analysis processes are continually / repeatedly conducted until such granulated waste particles (line 114) and / or separated particles (line 119) contain an acceptable composition for an intended purpose. In one or more embodiments, an acceptable composition can include a weight ratio of LLDPE:LDPE of about 2:98 to about 98:2. Material reprocessing

[0040] In some embodiments, the collected composition of LLDPE / LDPE particles can be used as a post-consumer resin (PCR). As such, the separated particles (line 119) 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 ordinary7skill 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.

[0041] 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 design of 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.

[0042] 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.

[0043] 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 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.

[0044] 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.

[0045] In one or more embodiments, the PCR has a density (as determined by ASTM 1505) of about 0.91 g / cm3to about 0.93 g / cm3.

[0046] 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 having specific gravity values less than the density of water. Additionally, the method(s) disclosed herein provide a pathway7to effectively separate granulated waste particles of similar densities (e.g., LLDPE and LDPE) 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.

[0047] The phrases, unless otherwise specified, "consists essentially of1and "consisting essentially of1do 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.

[0048] 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 explicitlyrecited, 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 lower or upper limit, to recite a range not explicitly recited.

[0049] 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 law. 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.

[0050] 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: conveying a plastic waste stream to a metal detection apparatus, wherein the metal detection apparatus is configured to remove magnetic materials; conveying the plastic waste stream from the metal detection apparatus to a shredder, wherein the shredder is configured to tear / shred the plastic waste stream to form a shredded plastic waste stream; conveying the shredded plastic waste stream to a first float / sink tank apparatus, the first float / sink tank apparatus configured to contain a first aqueous separation solution; separating the shredded plastic waste stream into a first plurality of plastic waste and a second plurality of plastic waste; conveying the first plurality7of plastic waste to a first granulator to form a plurality7of granulated plastic waste particles; conveying the plurality of granulated plastic waste particles to a hydrocylone to remove contaminates therefrom; conveying the plurality7of granulated plastic waste particles from the hydrocylone 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 plurality of granulated plastic waste particles into a first plurality of separated particles and a second plurality of separated particles; and collecting the first 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 high density polyethylene (HDPE), low density polyethy lene (LDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyvinylchloride (PVC), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl acetate (PVA), acrylonitrile-butadiene-styrene (ABS) plastic, or combinations thereof.

3. The method of claim 1, wherein the first aqueous separation solution is water.

4. The method of claim 1, wherein the first plurality of plastic waste comprises a specific gravity less than the density7of the first aqueous separation solution.

5. The method of claim 1. wherein the second plurality of plastic waste comprises a specific gravity greater than the density of the first aqueous separation solution6. The method of claim 1, wherein the second aqueous separation solution comprises a mixture of ethanol and water.

7. The method of claim 1. wherein the first plurality of separated plastic waste particles comprises a specific gravity less than the density of the second aqueous separation solution.

8. The method of claim 1, wherein the second plurality of separated plastic waste particles comprises a specific gravity greater than the density of the second aqueous separation solution.

9. The method of claim 1. wherein the first plurality of separated plastic waste particles comprising a plurality of linear low density polyethylene (LLDPE) particles and a plurality of low density polyethylene (LDPE) particles.

10. The method of claim 9, wherein the plurality of LLDPE particles have a density (as determined by ASTM 1505) of about 0.9 g / cm3to about 0.94 g / cm3.

11. The method of claim 9, wherein the plurality of LLDPE particles have a melt index (as determined by ASTMD-1238; 190 °C with a 2.16 kg load) of about 0.2 g / 10 min to about 20 g / 10 min.

12. The method of claim 9, wherein the plurality of LDPE particles have a density (as determined by ASTM 1505) of about 0.915 g / cm3to about 0.935 g / cm3.

13. The method of claim 9, wherein the plurality’ of LDPE particles have a melt index (as determined by ASTMD-1238; 190 °C with a 2.16 kg load) of about 0.2 g / 10 min to about 20 g / 10 min.

14. The method of claim 1, wherein collecting the first plurality of separated particles comprises: depositing the first plurality’ of separated particles into a first turbo dryer to remove moisture from the first plurality of separated particles; transporting the first plurality of separated particles through a pneumatic transport system from the first turbo dryer to a second turbo dryer, the second turbo dryer configured to remove additional moisture from the first plurality of separated particles; conveying the first plurality’ of separated particles from the second turbo dryer to a composition analysis unit; and performing a compositional analysis on the first plurality of separated particles.

15. The method of claim 14, wherein the compositional analysis unit 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), Raman spectroscopy, anti-stokes Raman spectroscopy, hyperspectral spectroscopy, acousticspectroscopy, nuclear magnetic resonance (NMR) spectroscopy, microwave spectroscopy, terahertz spectroscopy, or combinations thereof.

16. The method of claim 15, wherein the compositional analysis unit comprises a FTIR sensor.

17. The method of claim 16, wherein the first plurality' of separated plastic waste particles comprising a plurality of linear low density’ polyethylene (LLDPE) particles and a plurality of low density polyethylene (LDPE) particles.

18. The method of claim 17, wherein the weight ratio of LLDPE: LDPE of about 2:98 to about 98:2.

19. The method of claim 18, further comprising: conveying the first plurality of separated particles to a third float / sink tank apparatus, wherein the third float / sink tank apparatus is configured to contain a third aqueous separation solution having a density' of about 0.92 g / cm3to about 0.925 g / cm3; separating the first plurality of separated particles into a third plurality of separated particles and a fourth plurality of separated particles; collecting the third plurality of separated particles; depositing the third plurality7of separated particles into a first turbo dryer to remove moisture from the third plurality of separated particles; transporting the third plurality of separated particles through a pneumatic transport system from the first turbo dryer to a second turbo dryer, the second turbo dryer configured to remove additional moisture from the third plurality' of separated particles; conveying the third plurality' of separated particles from the second turbo dry er to a composition analysis unit; and performing a compositional analysis on the third plurality of separated particles.

20. The method of claim 19, wherein the third plurality of separated plastic waste particles comprising a plurality7of LLDPE particles and a plurality' of LDPE particles in a weight ratio of LLDPE:LDPE of about 2:98 to about 98:2.

Images