WO2025116884A1

WO2025116884A1 - Ultrasonic biodegradation of contaminants for post-consumer recyclate resins

Info

Publication number: WO2025116884A1
Application number: PCT/US2023/081179
Authority: WO
Inventors: Nicholas M. BRIGGS; Steven W. Horwatt; Mark K. Reinking
Original assignee: Equistar Chemicals LP
Current assignee: Equistar Chemicals LP
Priority date: 2023-11-27
Filing date: 2023-11-27
Publication date: 2025-06-05
Anticipated expiration: 2026-05-27

Abstract

A method for recycling plastic waste including the step of biodegrading plastic waste under ultrasonic conditions, wherein the plastic waste is selected from the group consisting of post-consumer recyclate and post-industrial recyclate.

Description

ULTRASONIC BIODEGRADATION OF CONTAMINANTS FOR POST-CONSUMER

RECYCLATE RESINS

FIELD OF THE INVENTION

[0001] In general, the present disclosure relates to the field of chemistry. More specifically, the present disclosure relates to post-consumer recyclate. In particular, the present disclosure relates to biodegrading post-consumer recyclate under ultasonic conditions, related processes, and products prepared therefrom.

BACKGROUND OF THE INVENTION

[0002] The downside to the demand for polyolefin plastics is an increase in plastic waste. As such, there is considerable interest in developing methods to recycle plastic waste. In addition to reducing the amount of plastic waste, other benefits of recycling plastic waste include reducing carbon footprint, consuming less energy, improving water consumption, and using less raw materials.

[0003] In many instances, before plastic waste is recycled and turned into usable resin, the plastic materials are gathered and sent through a process to produce plastic resin pellets. In some instances, the plastics recycling system is a mechanical recycling system, including the steps of sorting, cleaning, shredding, melting, and remolding.

[0004] In some instances, the resulting plastic resin pellets are made from or containing polyolefins, non-poly olefinic polymers, and other contaminants. In some instances, the non- polyolefinic polymers or the other contaminants are present in an amount that adversely affects the properties of the plastic resin pellets. In some instances, the non-polyolefinic polymers or the other contaminants provide stress points in articles made from or containing the plastic resin pellets.

BRIEF SUMMARY OF THE INVENTION

[0005] In a general embodiment, the present disclosure provides a method for recycling plastic waste including the step of biodegrading plastic waste under ultrasonic conditions, wherein the plastic waste is selected from the group consisting of post-consumer recyclate and postindustrial recyclate. [0006] In some embodiments, the present disclosure provides a post-consumer recycled resin prepared from a post-consumer recyclate, wherein the resin is selected from the group consisting of polyethylene and polypropylene. In some embodiments, the polyethylene is a high- density polyethylene.

[0007] In some embodiments, the present disclosure provides a post-industrial recycled resin prepared from a post-industrial recyclate, wherein the resin is selected from the group consisting of polyethylene and polypropylene. In some embodiments, the polyethylene is a high- density polyethylene.

[0008] In some embodiments, the present disclosure provides a polymer composition made from or containing resin selected from the group consisting of a post-consumer recycled resin and a post-industrial recycled resin.

[0009] In some embodiments, the present disclosure provides an article of manufacture made from or containing a resin selected from the group consisting of post-consumer recycled resins and post-industrial recycled resins.

[0010] While multiple embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description. As will be apparent, certain embodiments, as disclosed herein, are capable of modifications in various aspects, without departing from the spirit and scope of the claims as presented herein. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

DETAILED DESCRIPTION OF THE INVENTION

[0011] While the provided embodiments will be described more fully hereinafter, these embodiments are provided to satisfy applicable laws and regulations. As such, it will be apparent to those skilled in the art that the embodiments can incorporate changes and modifications without departing from the general scope. This disclosure is intended to include the modifications and alterations in so far as the modifications and alterations come within the scope of the appended claims or the equivalents thereof.

[0012] As used in this specification and the claims, the singular forms “a,” “an,” and “the” include plural referents unless the context dictates otherwise.

[0013] As used in this specification and the claims, the terms “comprising,” “containing,” or “including” mean that at least the named compound, element, material, particle, or method step is present in the composition, the article, or the method, but does not exclude the presence of other compounds, elements, materials, particles, or method steps even if the other such compounds, elements, materials, particles, or method steps have the same function as that which is named, unless expressly excluded in the claims. It is also to be understood that the mention of one or more method steps does not preclude the presence of additional method steps before or after the combined recited steps or intervening method steps between those steps expressly identified.

[0014] Moreover, it is also to be understood that the lettering of process steps or ingredients is for identifying discrete activities or ingredients and the recited lettering can be arranged in any sequence, unless expressly indicated.

[0015] For the purpose of the present description and of the claims which follow, except where otherwise indicated, numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified by the term “about”. Also, ranges include any combination of the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

[0016] Definitions

[0017] In the present description, the term “additive composition” refers to a composition made from or containing an additive.

[0018] In the present description, the term “a-olefin” or “alpha-olefin” means an olefin of formula CHz=CH — R, wherein R is a linear or branched alkyl containing from 1 to 10 carbon atoms. In some embodiments, the a-olefin is selected from the group consisting of propylene, 1- butene, 1 -pentene, 1 -hexene, 1 -octene, and 1 -decene.

[0019] In the present description, the term “biodegradation” refers to the decomposition of organic matter by a microorganism, including bacteria, fungi, or other living organisms. As the term is used herein, biodegradation includes the decomposition or depolymerization of plastics, involving excretion of extracellular enzymes by a microorganism, attachment of the enzymes to the surface of plastic, and hydrolysis of the plastic to monomers, oligomers, or other small molecules. Other biodegradable organic matter includes a variety of non-plastic materials, such as food stuffs and paper.

[0020] For plastics, the rate of biodegradation depends on several factors. Exposure- related factors include biosurfactants, hydrophobicity, moisture, pH, temperature, and ultraviolet radiation while polymer-related factors include additives, availability, bonds in the polymeric chains, crosslinking, crystallinity, functional groups, molecular weight, morphology, and surface characteristics.

[0021] Because enzymatic activities include hydrolysis/oxidation/hydroxylation, plastics can be classified in two groups: (i) hydrolysable polymers, which are polymers having (a) amide bonds, (b) ester bonds, or (c) hetero/carbamate bonds, and include polyamide, polyethylene terephthalate, and polyurethane polymers and (ii) non-hydrolysable polymers, which are polymers having carbon-carbon backbones and include polyethylene, polypropylene, polyvinylchloride, and polystyrene polymers.

[0022] In the present description, the term “contaminant” refers to any chemical substance present in a post-consumer recyclate (PCR), a post-industrial recyclate (PIR), a post-consumer recycled resin (PCR resin), or a post-industrial recycled resin (PIR resin), wherein the PCR, the PIR, the PCR resin, or the PIR resin is made from or containing a selected polymer and the presence of the chemical substance thereby renders the PCR, the PIR, the PCR resin, or the PIR resin compositionally different from the pure, selected polymer. In some embodiments, the contaminant is present in an amount ranging from parts per billion (ppb) to percentages, based upon the total weight of the PCR, the PIR, the PCR resin, or the PIR resin. In some embodiments, a multiplicity of contaminants is present. In some embodiments, the contaminant is selected from the group consisting of acrylonitrile butadiene styrene, calcium carbonate, coffee grounds, diapers, dirt, fillers, food stuffs, glass, grass, labels, metals (including aluminum), nylon, other inorganics, other polymers, paper, plant stems, polycarbonates, polyethylene terephthalate, polyurethane, processing additives, property -imparting additives, rubbers, and wood.

[0023] In the present description, the term “depolymerization” refers to a process in which a polymer is degraded to monomers, oligomers, and other molecules smaller than the polymer. In some instances, the constituent monomers are then available for repolymerization.

[0024] For example, the depolymerization of polyethylene terephthalate yields monomers (such as terephthalic acid and ethylene glycol) or oligomers (such as dimethyl terephthalate, methyl-2-hydroxyethyl terephthalate, bi s(2-hydroxy ethyl) terephthalate).

[0025] Nylon 6 (or polycaprolactam) is prepared from the monomer caprolactam while nylon 66 (or poly (hexamethylene adipamide)) is prepared from the monomers hexamethylene diamine and adipic acid. Similar to the description of the depolymerization of polyethylene terephthalate, the depolymerization of nylon 6 and nylon 66 would yield the monomers (a) caprolactam and (b) hexamethylene diamine and adipic acid, respectively.

[0026] In the present description, the term “elastomer” refers to polymer compounds having rubber-like properties and crystallinity in the range of from about 0 percent to about 20 percent.

[0027] In the present description, the term “enzyme” refers a substance produced by a microorganism which acts as a catalyst to enable or accelerate the biodegradation of plastic or nonplastic waste. In some instances, enzymes are suspended in water or other media. In some instances, the suspensions include other components such as preservatives and buffers.

[0028] In the present description, the term “enzymatic composition” refers a composition made from or containing an enzyme. In some embodiments, the enzymatic composition is further made from or containing coenzymatic additives, buffers, chelating agents, or preservatives.

[0029] In the present description, the term “first” refers to the order in which a particular species is presented and does not necessarily indicate that a “second” species will be presented. For example, “first polymer composition” refers to the first of at least one polymer composition. The term does not reflect priority, importance, or significance in any other way. Similar terms used that can be used herein include “second,” “third,” “fourth,” etc.

[0030] In the present description, the term “homopolymer” refers to polymers derived from a single monomeric unit. To the extent that a homopolymer is derived from more than a single monomeric unit, the incorporation of additional monomeric units has no measurable effect on the polymer’s primary, secondary or tertiary structure or no effect on the polymer’s physical or chemical properties. In other words, there is no measurable difference between a polymer, comprising 100 weight percent of a first monomeric unit, and a copolymer, including more than a single monomeric unit.

[0031] In the present description, the term “International Code Council (ICC) Certification” refers to products certified as using 100% post consumer resins.

[0032] In the present description, the term “interpolymer” refers to a polymer prepared by the polymerization of at least two types of monomers or comonomers. The term “interpolymer” includes copolymers, terpolymers, tetrapolymers, and the like. In some embodiments, the term “copolymer” refers to polymers prepared from two different types of monomers or comonomers. In some embodiments, the term “terpolymer” refers to polymers prepared from three different types of monomers or comonomers. In some embodiments, the term “tetrapolymer” refers to polymers prepared from four different types of monomers or comonomers. In some embodiments, the term “copolymer” is used interchangeably with “interpolymer” and refers to polymers made from three or more different types of monomers or comonomers.

[0033] In the present description, the terms “monomer” and “comonomer” are used interchangeably. The terms refer to any compound with a polymerizable moiety that is added to a reactor to produce a polymer. In those instances wherein a polymer is described as made from or containing one or more monomers, for example, a polymer made from or containing propylene and ethylene, the polymer, of course, is made from or containing units derived from the monomers, for example, — CH2 — CH2 — , and not the monomer itself, for example, CH2 TH2.

[0034] In the present description, the term “PCR” refers interchangeably to Post-Consumer Recycled or Post-Consumer Recyclate, including polymers such as high-density polyethylene (HDPE) and polypropylene (PP), which are recycled and reprocessed into a resin for use in various applications.

[0035] In the present description, the term “PIR” refers interchangeably to Post-Industrial Recycled or Post-Industrial Recyclate.

[0036] In the present description, the term “polyamide” refers to a polymer bearing recurring amide groups in the polymer’s backbone. Poly caprolactam and poly(hexamethylene adipamide) are commercially-available polyamides, which are respectively designated as “nylon 6” and “nylon 66”. Other nylons include nylon 11, nylon 12, nylon 46, and nylon 612.

[0037] As polyamide fibers and polyamide thermoplastics, aliphatic polyamides are used in various applications. In some instances, polyamide fibers are prepared in a melt-spun process and used in apparel, carpets, home textiles, surgical sutures, tire reinforcement, and other applications.

[0038] In some instances, polyamide thermoplastics are prepared with processes blow molding, extrusion, injection molding, and other thermoplastic processing methods. Polyamide thermoplastics are used in automotive applications (including body panels, fenders, and head light housings), electrical applications (including connectors, plugs, sockets, and switches), packaging applications (including food containers as moisture and oxygen barriers), clothing, and toys. For some applications, polyamide thermoplastics are coextruded with other polymers. [0039] In the present description, the term “polyethylene terephthalate” refers to a saturated polyester obtained by the polycondensation of (a) terephthalic acid and ethylene glycol or (b) dimethyl terephthalate and ethylene glycol.

[0040] In the present description, the term “polymer” refers to a macromolecular compound prepared by polymerizing monomers of the same or different type. The term “polymer” includes homopolymers, copolymers, terpolymers, interpolymers, and so on.

[0041] In the present description, the term “polymer composition” refers to a composition made from or containing a polymer.

[0042] In the present description, the term “polyolefin” is used herein broadly to include polymers such as polyethylene, ethylene-alpha olefin copolymers (EAO), polypropylene, polybutene, and ethylene copolymers having at least about 50 percent by weight of ethylene polymerized with a lesser amount of a comonomer such as vinyl acetate, and other polymeric resins within the "olefin" family classification.

[0043] Polyolefins can be made by a variety of processes including batch and continuous processes using single, staged, or sequential reactors, slurry, solution, and fluidized bed processes and one or more catalysts including for example, heterogeneous and homogeneous systems and Ziegler, Phillips, metallocene, single-site, and constrained geometry catalysts to produce polymers having different combinations of properties.

[0044] In the present description, the term “polyurethane” refers to a polymer prepared by reacting a diisocyanate with a polyol. Diisocyanates include toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), hydrogenated methylene diphenyl diisocyanate (H12MDI), and isophorone diisocyanate (IPDI). Polyurethanes are used in various applications, including apparel, automotive parts, building and construction materials, electronics, floorings, furnishings, packaging, and other applications.

[0045] In the present description, the term “post consumer recycled (PCR) resin” refers to the recycled product of waste created by consumers, including high-density polyethylene postconsumer recycled resin (HDPE PCR) and polypropylene post-consumer recycled resin (PP PCR). Among other forms, PCR resins may take the form of granules, pellets, and powders.

[0046] In the present description, the term “post industrial recycled (PIR) resin” refers to the recycled product of waste generated by manufacturers during the preparation of polymer-based products. In the present description, the disclosed, recycling processes for preparing and using PCR resins are extendable to PIR resins.

[0047] In the present description, the term “recycle” refers to the conversion of waste into a reusable material. The waste is created by consumers, in the case of post-consumer waste, or by manufacturers during the preparation of polymer-based products, in the case of post-industrial waste.

[0048] In the present description, the term “room temperature” refers to a temperature of about 25 degrees Celsius.

[0049] In the present description, the term “thermoplastic polymer” refers to a polymer that softens when exposed to heat and returns to its original condition when cooled to room temperature.

[0050] In the present description, the term “ultrasonic” or “ultrasonic mixing” refers to applying a cycle of alternating high and low pressure to a liquid medium, thereby creating vacuum bubbles which grow and merge together and then collapse to send shock waves through the mixture. The shock waves disrupt covalent bonds of materials suspended in the liquid medium. The shock waves are generated by an ultrasonic mixing device operating at a frequency greater than or equal to 20 kHz. In some instances, ultrasonic mixing creates localized regions of heat.

[0051] In the present description, the term “virgin polymers” refers to polymers prepared in polymerization processes from monomers, with or without catalysts or processing aids, and which are yet to be manufactured into first-use consumer or industrial products.

[0052] In a general embodiment, the present disclosure provides a method for recycling plastic waste including the step of biodegrading plastic waste under ultrasonic conditions, wherein the plastic waste is selected from the group consisting of post-consumer recyclate and postindustrial recyclate.

[0053] In some embodiments, the biodegrading step is achieved enzymatically. As previously-noted, plastics can be classified in two groups: (i) hydrolysable polymers and (ii) non- hydrolysable polymers. In some embodiments, the enzymes biodegrade selectively hydrolysable polymers, thereby removing the hydrolysable polymers and yielding a residue of the plastic waste made from or containing non-hydrolysable polymers. [0054] In some embodiments, the method is free from a step of sorting hydrolysable polymers from the plastic waste.

[0055] In some embodiments, the enzymes biodegrade selectively hydrolysable polymers, thereby converting the hydrolyzable polymers into the polymers’ monomeric constituents, oligomers, and other small molecules. In some embodiments, the monomeric constituents are collected. In some embodiments, the small monomers, oligomers, or other small molecules are removed via filtration, chemical extraction, or washing.

[0056] In some embodiments, the enzymatic biodegradation is achieved by an enzymatic composition made from or containing enzymes for biodegrading components of plastic waste. In some embodiments, the components include hydrolysable plastics and non-plastic organic materials. In some embodiments, the enzyme biodegrades selectively the non-plastic organic material, thereby yielding a product having a lower concentration of the non-plastic organic material.

[0057] In some embodiments, the enzymes of the enzymatic composition are selected for a spectrum of plastic waste components.

[0058] In some embodiments, the plastic waste is analyzed to determine the polymeric components of the plastic waste. In some embodiments, the analytical technique is selected from the group consisting of Fourier Transform Infrared spectroscopy, nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. In some embodiments, the enzyme or a combination of enzymes is selected based upon the analytical results. In some embodiments, the enzymatic composition is tailored and targeted to the identified plastic waste components.

[0059] It is believed that ultrasonic conditions accelerate the enzymatic degradation of the contaminants. In some embodiments, the shock waves disrupt the covalent bonds of the contaminant. In some embodiments, the ultrasonic conditions produce localized regions of heat, thereby creating enhanced loci for enzymatic degradation.

[0060] In some embodiments, the plastic waste is suspended in a liquid medium. In some embodiments, the medium is water or an organic composition. In some embodiments, the liquid medium is further made from or containing an additive selected from the group consisting of acids, bases, biosurfactants, and buffers, thereby improving the surface attachment of the enzyme and accelerating the biodegradation of the contaminant. [0061] In some embodiments, the biodegrading step occurs at a temperature above room temperature. In some embodiments, the contaminant is a polymer having a glass transition temperature (T_g) and the biodegrading step occurs at a temperature greater than or equal to T_g, alternatively greater than or equal to T_g.

[0062] In some embodiments, the biodegrading step occurs in the presence of ultraviolet radiation.

[0063] In some embodiments, the method for recycling plastic waste includes the steps of:

(a) collecting the plastic waste from residential, commercial, and industrial sites, wherein the plastic waste is selected from the group consisting of postconsumer recyclate and post-industrial recyclate, and made from or containing a polyolefin and a concentration of a contaminant;

(b) biodegrading the plastic waste under ultrasonic conditions, thereby degrading the contaminant and yielding a polymer mixture made from or containing the polyolefin and a concentration of contaminant lower than the concentration in the former plastic waste;

(c) melting the polymer mixture, thereby yielding a fusion-melt; and

(d) pelletizing the fusion-melt, thereby forming a pelletized resin selected from the group consisting of a pelletized, post-consumer recycled (PCR) resin and a pelletized, post-industrial recycled (PIR) resin.

[0064] In some embodiments, the method for recycling plastic waste further includes the steps of:

(a.i) sorting the plastic waste; and

(a.ii) cleaning the plastic waste.

[0065] In some embodiments, the method for recycling plastic waste further includes the steps of:

(a.iii) sieving the plastic waste; and

(a.iv) separating the plastic waste by particle size.

[0066] In some embodiments, the method for recycling plastic waste includes the steps of: (a) collecting the plastic waste from residential, commercial, and industrial sites, wherein the plastic waste is selected from the group consisting of postconsumer recyclate and post-industrial recyclate, and made from or containing a polyolefin and a contaminant;

(a.i) sorting the plastic waste;

(a.ii) cleaning the plastic waste;

(a.iii) sieving the plastic waste; and

(a.iv) separating the plastic waste by particle size;

(c) melting the polymer mixture, thereby yielding a fusion-melt; and

[0067] In some embodiments, the method for recycling plastic waste include one or more pretreating steps. In some embodiments, the pretreatment is selected from the group consisting of acid pretreatment, alkaline pretreatment, biological pretreatment, electroporation, grinding or other surface-area-increasing treatment, irradiation, microwave, organic solvent pretreatment, ozone, sonication, supercritical fluidization, temperature pretreatment.

[0068] In some embodiments, the acid pretreatment involves mixing the plastic waste with acid and water to form a slurry, heating the slurry with steam, and flashing the composition to atmospheric pressure . In some embodiments, the acid is sulfuric acid.

[0069] In some embodiments, the alkaline pretreatment is selected from the group consisting of sodium hydroxide, lime, wet oxidation, ammonia percolation, and ammonia fiber/freeze expansion. [0070] In some embodiments, the temperature pretreatment occurs in the range of 10-300 degrees Celsius. In some embodiments, the temperature pretreatment with mixing. In some embodiments, the temperature pretreatment is achieved by adding water or steam.

[0071] As previously noted, the mention of one or more method steps does not preclude the presence of additional method steps before or after the combined recited steps or intervening method steps between those steps expressly identified.

[0072] In some embodiments, the plastic waste is made from or containing automobile parts, bleach bottles, food containers, freezer and shopping bags, milk jugs, outdoor furniture, packaging materials, piping, plastic bottles, playground equipment, shampoo bottles, signage and fixtures, toys, and contaminants. In some embodiments, the contaminants are selected from the group consisting of acrylonitrile butadiene styrene, calcium carbonate, coffee grounds, diapers, dirt, fillers, food stuffs, glass, grass, labels, metals (including aluminum), nylon, other inorganics, other polymers, paper, plant stems, polycarbonates, polyethylene terephthalate, polyurethane, processing additives, property-imparting additives, rubbers, and wood.

[0073] In some embodiments, the present disclosure provides a post-consumer recycled resin prepared from a post-consumer recyclate, wherein the resin is selected from the group consisting of polyethylene and polypropylene. In some embodiments, the polyethylene is a high- density polyethylene.

[0074] In some embodiments, the present disclosure provides a post-industrial recycled resin prepared from a post-industrial recyclate, wherein the resin is selected from the group consisting of polyethylene and polypropylene.

[0075] In some embodiments, the present disclosure provides a polymer composition made from or containing resin selected from the group consisting of a post-consumer recycled resin and a post-industrial recycled resin. In some embodiments, the polymer composition is made from or containing:

(a) from 5 % by weight to 95 % by weight, based upon the total weight of the polymer composition, of a resin selected from the group consisting of a post-consumer recycled resin and a post-industrial recycled resin; and

(b) from 5 % by weight to 95 % by weight, based upon the total weight of the polymer composition, of a virgin polymer. [0076] In some embodiments, the resin is selected from the group consisting of HDPE PCR and PP PCR. In some embodiments, the resin is the base resin of the polymer composition. In some embodiments, the resin is a complementary resin. In some embodiments, the resin is a component in an additive composition or a filler, for use with a virgin or other PCR resin. In some embodiments, the resin is used as a filler in amount up to 50 % by weight, alternatively from 0.5 % by weight to 30 % by weight, alternatively from 1.0 % by weight to 20% by weight, based upon the total weight of the polymer composition.

[0077] In some embodiments, the resin bears the International Code Council (ICC) Certification.

[0078] In some embodiments, the polymer composition is further made from or containing an additive composition. In some embodiments, the additive composition imparts properties such as thermal stability, light and ultraviolet protection, and color. In some embodiments, the additive composition is present in an amount from 0.05 % by weight to 10 % by weight, alternatively from 0.1 % by weight to 8 % by weight, based upon the total weight of the polymer composition.

[0079] In some embodiments, the present disclosure provides an article of manufacture made from or containing a resin selected from the group consisting of post-consumer recycled resins and post-industrial recycled resins. In some embodiments, the article of manufacture is selected from the group consisting of blow-molded articles, films, flexibles, injection-molded articles, packaging, and piping. In some embodiments, the article of manufacture is useful in noncosmetic-intensive, post consumer recycled resin applications, including agricultural film and trash bags.

[0080] It should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of this disclosure as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of the ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform the same function or achieve the same result as the corresponding embodiments described herein can be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

CLAIMS What is claimed is:

1. A method for recycling plastic waste comprising the step of: biodegrading plastic waste under ultrasonic conditions, wherein the plastic waste is selected from the group consisting of post-consumer recyclate and post-industrial recyclate.

2. The method for recycling plastic waste of Claim 1, comprising the steps of:

(a) collecting the plastic waste from residential, commercial, and industrial sites, wherein the plastic waste is selected from the group consisting of post-consumer recyclate and post-industrial recyclate, and comprising the polyolefin and the contaminant;

(c) melting the polymer mixture, thereby yielding a fusion-melt; and

(d) pelletizing the fusion-melt, thereby forming a pelletized resin selected from the group consisting of a pelletized, post-consumer recycled (PCR) resin and a pelletized, postindustrial recycled (PIR) resin.

3. The method for recycling plastic waste of Claim 2, wherein the biodegrading step occurs in the presence an enzymatic composition comprising an enzyme.

4. The method for recycling plastic waste of Claim 3, wherein the contaminant is a hydrolysable polymer and the enzyme biodegrades selectively the hydrolysable polymer, thereby converting the hydrolysable polymer to the hydrolysable polymer’s monomers, oligomers, or other small molecules.

5. The method for recycling plastic waste of Claim 3, wherein the contaminant is a non-plastic organic material and the enzyme biodegrades selectively the non-plastic organic material, thereby yielding a product having a lower concentration of the non-plastic organic material.

6. The method for recycling plastic waste of Claim 3, further comprising the step:

(a.i) analyzing the plastic waste, thereby determining the hydrolysable polymer; and (a.ii) selecting the enzyme such that the enzyme biodegrades selectively the hydrolysable polymer.

7. The method for recycling plastic waste of Claim 1, wherein the plastic waste comprises automobile parts, bleach bottles, food containers, freezer and shopping bags, milk jugs, outdoor furniture, packaging materials, piping, plastic bottles, playground equipment, shampoo bottles, signage and fixtures, toys, and contaminants.

8. The method for recycling plastic waste of Claim 7, wherein the contaminants are selected from the group consisting of acrylonitrile butadiene styrene, calcium carbonate, coffee grounds, diapers, dirt, fillers, food stuffs, glass, grass, labels, metals (including aluminum), nylon, other inorganics, other polymers, paper, plant stems, polycarbonates, polyethylene terephthalate, polyurethane, processing additives, property-imparting additives, rubbers, and wood.

9. A post-consumer recycled resin comprising a resin selected from the group consisting of polyethylene and polypropylene, free of enzyme-hydrolysable contaminants.

10. An article of manufacture comprising the post-consumer recycled resin of Claim 9.