Post-consumer recycled thermoplastics treated for melt-processing with enhanced quality

Abstract

A post-consumer recycled polyethylene terephthalate (PCR-PET) blend is disclosed comprising at least one recycled polyethylene terephthalate (rPET) flake; a chelant comprising an active chelant dispersed in a liquid carrier and / or a masterbatch comprising a solid component of active chelant and a resin; and at least one processing additive.

Description

POST-CONSUMER RECYCLED THERMOPLASTICS TREATED FOR MELTPROCESSING WITH ENHANCED QUALITYCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 729,603, filed on December 9, 2024, the entire contents of which being incorporated by reference herein.FIELD OF THE INVENTION

[0002] This invention relates to post-consumer recycled (PCR) thermoplastics including but not limited to polyesters such as polyethylene terephthalate (PET). More particularly, this invention relates to improved post-consumer recycled polyethylene terephthalate (PCR-PET) flake that is treated for use in making thermoplastic articles by subsequent melt-processing with enhanced quality such as reduced discoloration and lower levels of non-intentionally added substances (NIAS) such as benzene generated relative to untreated PCR-PET flake.BACKGROUND OF THE INVENTION

[0003] Polyesters, especially polyethylene terephthalate (PET), are versatile polymers that enjoy applicability in a variety of thermoplastic articles such as fibers, films, and three-dimensional structures. A particularly important use of PET is for bottles and containers, especially for food and beverages. This use has seen enormous growth over the last several decades and continues to enjoy increasing popularity.

[0004] More recently, demand has grown for food and beverage containers made from at least a portion of post-consumer recycled PET (PCR-PET). Supply of PCR-PET originates primarily from PET bottles collected through one of two routes: either established deposit or redemption programs (deposit PCR-PET) or local curbside recycling programs (curbside PCR-PET). Deposit PCR-PET, which typically is not admixed with other materials or food waste, is generally considered to be higher quality compared to curbside PCR-PET, although the supply of deposit PCR-PET is small compared to curbside PCR-PET. In any event, both deposit PCR-PET and curbside PCR-PET suffer some degree of quality loss relative to virgin PET. Moreover, both are considered contaminated and must undergo physical and thermal decontamination to be considered food-grade material.

[0005] Regardless of the collection route, PET bottles go through a complex process of sortation, grinding, air elutriation, screening, and sink-float steps to remove labels, glue, dirt, caps, and different types of polymers such as polyvinyl chloride (PVC). The cleaned and sorted PCR-PET product, which is in the form of ground flake, is washed extensively, dried, and further decontaminated by heating under vacuum or inert gas. Subsequently, at some point, the PCR-PET flake is melt- processed, and usually extruded into pellets. Then, the PCR-PET pellets can be mixed with virgin PET pellets and molded into new thermoplastic articles.

[0006] An entire industry, which is devoted to producing PCR-PET material suitable for use in food and beverage containers, has developed. But, throughout this industry, it is widely known that, despite best efforts, the quality of PCR-PET is not as high as that of virgin PET. Some quality issues, such as particulates, have been generally solved by melt-filtration. Other issues, including discoloration and generation of non-intentionally added substances (NIAS) such as benzene or bisphenol A (BPA), remain unaddressed. It is also recognized that these issues are unique to PCR- PET relative to virgin PET. For example, while the color of virgin PET generally increases with each cycle of its heat history (i.e., each occurrence of melt-processing the PET), this increase is trivial compared to the color generated by one heat history of PCR-PET. Similarly, the amount of benzene generated by one heat history of PCR-PET is significantly greater than that generated by one heat history of virgin PET. The origin of the discoloration and NIAS generation in melt- processed PCR-PET has variously been ascribed to contaminants such as inks, labels, glue, oxygen scavengers, or different polymers such as PVC. Nevertheless, these issues have remained unaddressed.

[0007] Consequently, a need exists for an improved PCR-PET, as well as PCR flake of other thermoplastics such as polyolefins, that can be melt-processed for use in making thermoplastic articles, especially containers for food and beverages, with enhanced quality as indicated by reduced discoloration or lower levels of generation of NIAS. There is further a need for inclusion of higher amounts of PCR-PET in such thermoplastic articles without negatively affecting the article quality. The aforementioned needs are met by one or more aspects of the disclosed invention.SUMMARY OF THE INVENTION

[0008] It has now been discovered that improved post-consumer polyethylene terephthalate (PCR-PET) blends can be produced that include at least one PCR-PET flake, a chelant, and at least one processing additive. The PCR-PET blends have reduced discoloration and lower levels of non- intentionally added substances (NIAS) relative to untreated PCR-PET flake. The chelant may be a liquid chelant comprising active chelant dispersed in a liquid carrier, such as an aqueous or nonaqueous carrier, or the chelant may be a chelant masterbatch comprising an active chelant and a resin. The processing additive may be selected from the group consisting of hindered phenols, organic phosphites, inorganic phosphites, antioxidants, scavengers, flow modifiers, chain extenders, odor absorbers, and mixtures thereof. In particular aspects, the processing additive is in the form of an additive package comprising a blend of two or more of an antioxidant, an acid scavenger, and a halogen scavenger.

[0009] Thus, certain aspects are directed to a post-consumer recycled polyethylene terephthalate (PCR-PET) blend comprising at least one recycled polyethylene terephthalate (rPET) flake; a liquid chelant composition comprising active chelant dispersed in a liquid carrier; and at least one processing additive. The liquid carrier may comprise an aqueous or non-aqueous carrier, and in some aspects, preferably a non-aqueous carrier. The non-aqueous carrier may comprise one or more of polyalkylene glycol, acetylated monoglycerides, aliphatic dibasic acid esters, benzoate esters, trimellitate esters, polyesters, citrates, food oils, and bio-based plasticizers.

[0010] In accordance with any aspect, the active chelant may be present in the PCR-PET blend an amount from about 1 to about 5000 ppm and selected from the group consisting of carboxylic acids and salts thereof; phosphoric acids and salts thereof; phosphonic acids and salts thereof; and combinations thereof. The processing additive may be present in an amount between 100 and 10,000 ppm and may comprise one or more of hindered phenols, organic phosphites, inorganic phosphites, antioxidants, scavengers, flow modifiers, chain extenders, and odor absorbers. In accordance with certain aspects, the processing additive may be present as an additive package comprising a blend of two or more of antioxidant, an acid scavenger, and a halogen scavenger. The antioxidant may comprise, for example, a phosphite antioxidant, phenolic antioxidant, or mixtures thereof and the scavenger may comprise, for example, calcium stearate, zinc stearate, zinc oxide, hydrotalcite, or mixtures thereof.

[0011] In accordance with any aspect, the additive package may include 200 ppm to 2000 ppm of one or more antioxidants and 50 ppm to 1500 ppm of one or more scavengers.

[0012] Further aspects of the present inventive concepts are directed to an extruded polyethylene terephthalate (PET) material. The extruded PET material comprises virgin PET and recycled PET (rPET), wherein the rPET comprises a chelant and at least one processing additive. The extruded PET material has a b* value that is at least 25% lower than the b* value of an otherwise comparative extruded PET material that does not include the chelant and processing additive.

[0013] In any of the exemplary aspects, the chelant may comprise a liquid in an aqueous or nonaqueous carrier, or a masterbatch comprising solid component of active chelant and a resin.

[0014] In any of the exemplary aspects, the PET material may be in the form of one or more pellets.

[0015] Further aspects of the present inventive concepts are directed to methods of treating recycled polyethylene terephthalate (rPET) flake. The methods include the steps of forming a postconsumer polyethylene terephthalate (PCR-PET) material by melt processing: at least one recycled polyethylene terephthalate (rPET) flake; a chelant; and at least one processing additive. The PCR- PET material has a b* value that is at least 25% lower than the b* value of an otherwise comparativeextruded PET material that does not include the chelant and processing additive. Optionally, the methods may further include a step pelletizing the PCR-PET material, forming a plurality of PCR- PET pellets.

[0016] As with the aspects discussed above, the chelant may comprise a liquid in an aqueous or non-aqueous carrier, or a masterbatch comprising solid component of active chelant and a resin.

[0017] Features of the invention will become apparent with reference to the following embodiments. There exist various refinements of the features noted in relation to the above- mentioned aspects of the disclosed invention. Additional features may also be incorporated in the above-mentioned aspects of the disclosed invention. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the described aspects of the invention may be incorporated into any of the described aspects of the invention alone or in any combination.DETAILED DESCRIPTION OF THE INVENTION

[0018] Disclosed herein are post-consumer polyethylene terephthalate (PCR-PET) blends that include at least one PCR-PET flake, a chelant, and optionally, at least one processing additive. The subject inventive concepts are further directed to thermoplastic articles formed using such PCR-PET blends with improved quality and performance.

[0019] Required and optional features of these and other embodiments of the disclosed invention are described.

[0020] The terminology as set forth herein is for description of the various aspects only and should not be construed as limiting the disclosure as a whole. All references to singular characteristics or limitations of the present disclosure shall include the corresponding plural characteristic or limitation, and vice versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made. Unless specified otherwise, “a,” “an,” “the,” and “at least one” are used interchangeably. Furthermore, as used in the description and the appended claims, the singular forms “a,” “an,” and “the” are inclusive of their plural forms, unless the context clearly indicates otherwise.

[0021] Unless otherwise expressly defined, all technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art.

[0022] Unless otherwise expressly stated, it is not intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that any apparatus article set forth herein be construed as requiring specific orders or orientations to its individual components.

[0023] Unless otherwise expressly stated, it is intended that any composition or mixture set forth herein can comprise, consist essentially of, or consist of the disclosed ingredients.

[0024] As used herein, the singular form of a term is intended to include the plural form of the term, unless the context clearly indicates otherwise.

[0025] As used herein, any disclosed numerical value is intended to refer to both exactly the disclosed numerical value and "about" the disclosed numerical value, such that either possibility is contemplated as an embodiment of the disclosed invention, unless the context clearly indicates otherwise. Also as described herein, the terms “substantially” and “about” are defined as at least close to (and includes) a given value or state (preferably within 10% of, more preferably within 1% of, and most preferably within 0.1% of).

[0026] To the extent that the term “includes” or “including” is used in the description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use.

[0027] Any composition described in the present disclosure can comprise, consist of, or consist essentially of the essential elements of the disclosure as described herein, as well as any additional or optional element described herein, or which is otherwise useful in the present inventive concepts.

[0028] All percentages, parts, and ratios as used herein are by weight of the total blend on an “dry” basis, i.e., without solvents, unless otherwise specified.

[0029] All ranges and parameters, including but not limited to percentages, parts, and ratios, disclosed herein are understood to encompass any and all sub-ranges assumed and subsumed therein, and every number between the endpoints. For example, a stated range of “1 to 10” should be considered to include any and all sub-ranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 1 to 6.1, or 2.3 to 9.4), and to each integer (1, 2, 3, 4, 5, 6, 7, 8, 9, and 10) contained within the range. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0030] The term “wt.%,” as described herein, refers to the weight fraction of the individual component based on a total weight of the thermoplastic layer composition, unless otherwise noted.

[0031] Additionally, as used herein, the term “exemplary” is intended to mean serving as an illustration or example of something, and is not intended to indicate a preference.

[0032] “Polyethylene terephthalate” or “Polyethylene terephthalate polymer”, also abbreviated PET, are used interchangeably and refer to a thermoplastic polymer resin of the polyester family, produced from monomers of monoethylene glycol (MEG) and dimethyl terephthalate (DMT) or purified terephthalic acid (PTA). PET may exist both as an amorphous and as a semi-crystalline polymer. In the context of the invention, homopolymers and copolymers of PET are also encompassed.

[0033] As used herein, the term "flake" or “rPET flake” means the form of PCR-PET as produced by grinding post-consumer recycled PET bottles, containers, or the like, as part of conventional postconsumer recycling processes. Generally, without intended to be limiting, the form can be any shape of fragment, piece, chunk, or the like, and implies the PCR-PET is in a solid (i.e., not melted) state.

[0034] As used herein, the term "formed from" (including related terms such as "forming") means, with respect to a thermoplastic article (or component of the article) and a thermoplastic material, that the thermoplastic article (or component of the article) is extruded, molded, shaped, pressed, or otherwise made, in whole or in part, from the thermoplastic material under sufficient heating to enable such forming. As such, the term "formed from" (including related terms such as "forming") means, in some embodiments, the article (or component of an article) can comprise, consist essentially of, or consist of, the material; and, in other embodiments, the article (or component of an article) consists of the material because the article (or component of an article) is, for example, made by an extrusion process or a molding process. As used herein, the term "formed from" (including related terms such as "forming") is not intended to be limited to a single forming step or process; rather, it is intended to include one or more forming steps or processes. For example, the term "formed from" can include a first step of extruding a thermoplastic material into pellets followed by a second step of forming the pellets into a thermoplastic article by a process forming such as extrusion, molding, and the like.

[0035] As used herein, the term "NIAS" means "non-intentionally added substance" and generally refers to a chemical or substance that is present in an article formed from a thermoplastic material but was not added for a technical reason during the production process. Non-limiting examples of NIAS may include hydrocarbons such as benzene or any chemical contaminant or product of degradation.

[0036] As used herein, the term "PCR-PET" means post-consumer recycled polyethylene terephthalate. In some instances, the term "rPET" is used to refer to PCR-PET. rPET Flake

[0037] In various aspects provided herein, a PCR-PET blend is provided that includes one or more rPET flakes.

[0038] According to embodiments of the invention, rPET flake is blended with chelant to reduce either discoloration or NIAS generation, or both discoloration and NIAS generation, upon meltprocessing of the rPET flake.

[0039] While not intending to be limited by theory, it is believed that inorganic contaminants such as transition metal ions and metal catalysts can be present on or associated with rPET flakes, and these contaminants can contribute at least in part to the higher levels of discoloration and NIAS generation that have been observed heretofore upon melt-processing of the PCR-PET flake.

[0040] It is believed these transition metals can come from a variety of sources, including corrosion metals from the PCR-PET processing equipment, debris from the recycling centers and transportation vehicles, and metals from co-mingled recyclate, including printed circuit boards, scrap metal, and rust. These and other residues can be incorporated into the PET matrix upon meltprocessing. A number of these metals, such as iron, nickel, and copper are known decarboxylation catalysts for benzoic acid. Although it is known to blend rPET flakes with an aqueous chelant prior to melt processing to sequester and deactivate the metal ions, such that the ions are not available for decarboxylation reactions and color formation, it was surprisingly discovered that this effect is substantially improved by incorporation of a chelant in either liquid or solid form, optionally including an additive package.

[0041] Although embodiments of the invention are applied to rPET flake, it is contemplated that the present disclosure is not necessarily limited thereto and the principles of the invention can be applied to other types of post-consumer recycled thermoplastics including but not limited to other types of polyesters or polyolefins such as polyethylene and polypropylene.Chelant

[0042] In various aspects provided herein, the PCR-PET blend further includes at least one chelant. As used herein, the term “chelant,” “chelating agent,” and “chelator” may be used interchangeably to refer to a compound that reacts or forms a complex with metal ions. Chelants suitable for use in the subject PCR-PET blend include chelating agents capable of complexing with transition metal ions. In various aspects, the chelant may have a log K stability constant (Kf) with transition metal ions that is greater than 3, such as, for example, greater than 5, greater than 7, or greater than 10.

[0043] According to any aspect, the chelant may comprise an organic acid, inorganic acid, or mixtures thereof. The chelant is a non-reducing agent and therefore does not readily donate electrons. In any exemplary aspect, the chelant may be selected from carboxylic acids and saltsthereof; phosphoric acids and salts thereof; phosphonic acids and salts thereof; and combinations thereof.

[0044] In some embodiments, the chelant comprises ethylenediamine tetraacetic acid (EDTA); phosphoric acid; pyrophosphoric acid, editronic acid, alkyl phosphonic acid, sodium acid pyrophosphate, disodium EDTA; and combinations thereof. In some aspects, the chelant preferably comprises phosphoric acid.

[0045] The chelant may be in liquid form, whereby the chelant is dispersed within an aqueous or non-aqueous carrier as a solution, dispersion, emulsion, or the like. The carrier for the liquid chelant may particularly comprise a carrier that is non-aqueous and non-degrading to PET at elevated processing temperatures (about 250-300°C). The non-aqueous carrier may comprise a non-volatile carrier. Exemplary non-volatile carriers include aliphatic dibasic acid esters (i.e., glutarates, adipates, azelates, and sebacates), benzoate esters, trimellitate esters, polyesters, citrates, and bio-based plasticizers. Particular examples include carriers based on food oils, such as soybean oil, canola oil, olive oil; epoxidized food oils; polyalkylene glycol; and acetylated monoglyceride.

[0046] When in liquid form, the chelant may be included into the PCR-PET blend in any manner that is sufficient to blend the chelant with the rPET flakes. For instance, the liquid chelant may be added to PCR-PET wash water prior to dewatering the rPET flake. Accordingly, the chelant can help solubilize metal ions on the surface of the rPET flake or in the wash water generally. Alternatively, or in addition, the liquid chelant may be sprayed onto the flakes as a mist or injected into an extruder at a feeding zone that is prior to the polymer melting zone.

[0047] In other aspects, either as an alternative to or in addition to the chelant in liquid form, the chelant may be in the form of a solid, such as with a solid masterbatch along with a resin. The chelant masterbatch may be formed by dispersing solid chelant particles in a carrier resin. The carrier resin may comprise a polyester resin, such a polyethylene terephthalate, for optimal compatibility with the PET flakes. Alternatively, or in addition to the PET carrier resin, the masterbatch may comprise other carrier polymers, providing that such polymers are compatible with the PET flakes, such as, for example, polycarbonate, polybutylene terephthalate (PBT), poly(butylene adipate-co-terephthalate) (PBAT), or other resin compatible with the PET flakes. As used herein, the term “masterbatch” refers to concentrates of active material (such as the chelant) in a polymer carrier, which are intended to be subsequently incorporated into another polymer (compatible with the polymer already contained in these masterbatches).

[0048] The solid chelant may be blended with the rPET in any manner sufficient to blend the active chelant with the rPET flakes. For instance, the chelant masterbatch may be added directly toan extruder or other compounding device, prior to melting the rPET flakes. In other aspect, the chelant masterbatch and rPET flakes may be pre-blended, prior to addition to the extruder.

[0049] The amount of chelant present in the PCR-PET blend may be characterized by defining an amount of active chelant. The term “active chelant,” as used herein, means the amount of chelant material present in the liquid carrier or masterbatch that is subsequently incorporated in the PCR-PET blend.

[0050] The amount of active chelant present in the PCR-PET blend should be sufficient to at least partially, and, in some embodiments, completely complex the transition metals present in the PCR- PET blend. In any of the exemplary aspects, the blend may comprise about 1 to about 5000 ppm active chelant, based on the total weight of the PCT-PET blend, including, for example, about 25 to about 2500 ppm, about 50 to about 1000 ppm, about 75 to about 750 ppm, about 100 to about 500 ppm, and about 150 to about 300 ppm, including all endpoints and subranges therebetween.

[0051] As discussed above, while not intending to be limited by theory, it is believed that inorganic water-borne contaminants such as transition metal ions and catalysts such as antimony, zinc, titanium and the like can be present in the wash water, on the surface of rPET flake, or otherwise associated with the rPET flakes. By treating the rPET flake with the chelant, whether in solid (dry) or liquid form, the contaminants associated with (i.e., on the surface of the rPET flake or within a material carrying the rPET, such as wash water, matrix materials, or other carriers) the rPET flake can be made unavailable for the mechanisms responsible for the discoloration and the NIAS generation, for example, by deactivating and / or solubilizing (and washing away) the transition metal ions and / or catalysts. In some embodiments, chelant is bonded to, and forms coordination complexes with, at least a portion of the transition metal ions and catalysts that are associated with the rPET.Processing Additives

[0052] In various aspects provided herein, the PCR-PET blend includes one or more processing additives. Various processing additives, or combination of additives, may be used, such as, for example, organic phosphites, inorganic phosphites, antioxidants, scavengers, flow modifiers, chain extenders, odor absorbers, and the like. In any of the exemplary aspects, the PCR-PET blend may comprise an additive package or blend, comprising at least two processing additives. It has been surprisingly discovered that particular additives and additive packages have a synergistic effect when used in combination with chelants, providing an improved reduction in color and allows for an increased amount of rPET that may be utilized in the manufacture of downstream thermoplastic articles.

[0053] As with the chelant discussed above, the amount of processing additive(s) present in the PCR-PET blend may be characterized by defining an amount of active processing additive (provided in ppm or % active). The term “active processing additive,” as used herein, means the amount of processing additive material present in the PCR-PET blend. In any of the exemplary aspects, if present, the PCR-PET blend may comprise about 100 to about 10,000 ppm active processing additive, including, for example, about 500 to about 5,000 ppm, about 750 to about 2500 ppm, about 1000 to about 2000 ppm, about 1200 to about 1500 ppm, including all endpoints and subranges therebetween.

[0054] The processing additives may comprise one or more of an antioxidant, acid scavenger, a halogen scavenger, a chain extender, and the like. Exemplary antioxidants include primary antioxidants, such as phenolics, and secondary antioxidants, such as phosphites, amines, and mixtures thereof. Effective commercial antioxidants may include Irganox® 1010 and Doverphos S-9228®. Exemplary scavengers include calcium stearate, zinc stearate, zinc oxide, hydrotalcite, and specifically DHT®-4C, and DHT®-4A2. Exemplary chain extenders include anhydrides, epoxy, melamines, oxazolines, oxazolinones, lactams carbodiimides, polyepoxides isocyanates polyacyllactams, and phosphonates. When the chain extender is an anhydride, it may be a multifunctional anhydride. Examples include aromatic acid anhydrides, cyclic aliphatic anhydrides, halogenated acid anhydrides, pyromellitic dianhydride, benzophenonetetracarboxylic acid dianhydride, cyclopentanetetracarboxylic dianhydride, diphenyl sulfone tetracarboxylic dianhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-l,2-dicarboxylic dianhydride, bis(3,4- dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)thioether dianhydride, bisphenol-A bisether dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 2, 3,6,7- napthalenetetracarboxylic acid dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1, 2,5,6- napthalenetetracarboxylic acid dianhydride, 2,2',3,3'-biphenyltetracarboxylic acid, hydroquinone bisether dianhydride, 3,4,9, 10-perylene tetracarboxylic acid dianhydride, 1, 2,3,4- cyclobutanetetracarboxylic acid dianhydride, 3, 4-dicarboxy- 1,2,3, 4-tetrahydro-l -naphthalene- succinic acid dianhydride, bicyclo(2,2)oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 4,4'-oxydiphthalic dianhydride (ODPA), and ethylenediamine tetraacetic acid dianhydride (EDTAh), or combinations thereof. Exemplary polyepoxide structures include bisphenol-A-diglycidylether, bis (3,4- epoxycyclohexylmethyl) adipate, N,N-diglycidyl benzamide (and related species) N,N-diglycidyl nailine and related structures, N,N diglycidylhydantoin, barbituric acid, isocyanuric acid or uracil species, N,N-diglycidyl di-imides, N,N-diglycidyl imidazolones, epoxy novolaks, phenyl glycidyl ether di ethyleneglycol diglycidyl ether or Epikote® products such as Epikote® 815 or Epikote® 828,or combinations thereof. In particular aspects, the chain extender is pyromellitic dianhydride (PMDA) at 500 to 3000 ppm.

[0055] In any of the exemplary aspects, the additive package may include 200 ppm to 2000 ppm of one or more antioxidants and 50 ppm to 1500 ppm of one or more scavengers, including, for example, from 400 ppm to 1800 ppm of one or more antioxidants and from 150 ppm to 1000 ppm of one or more scavengers, including all endpoints, subranges, and combinations therein.Methods of Treating PCR-PET Flake

[0056] Various aspects of the present disclosure relate to methods of forming a PCR-PET blend from rPET flakes for its use in forming PCR-PET pellets and / or manufacturing a thermoplastic article therefrom. The method includes the steps of: (a) providing the rPET flake; (b) providing a chelant and optionally, processing additive(s); and (c) forming a PCR-PET blend by mixing the rPET flakes with the chelant and optional processing additive package.

[0057] The process for treating rPET flakes may be performed in a batch process or a continuous process. Blending (also known as compounding) devices are well known to those skilled in the art and generally include feed means, especially at least one hopper for pulverulent materials and / or at least one injection pump for liquid materials; high-shear blending means, for example a corotating or counter-rotating twin-screw extruder, usually comprising a feed screw placed in a heated barrel (or tube); an output head, which gives the extrudate its shape; and means for cooling the extrudate, either by air cooling or by circulation of water. The extrudate is generally in the form of rods continuously exiting the device and able to be cut or formed into pellets. However, other forms may be obtained by fitting a die of desired shape on the output die.

[0058] For example, the materials for the PCR-PET blend (i.e., the rPET flakes, the chelant, and optional processing additives) may be fed to an extruder (e.g., 27 MM Leistriz Twin Extruder (L / D 52)) and blended. The blending (e.g., in the barrel of the extruder) may be carried out at a temperature sufficient to melt the ingredients such that they are sufficiently blended and capable of being formed into strands in the die. For PCR-PET, this is usually accomplished at melt temperatures between about 250 °C to about 300 °C. In accordance with the present disclosure, the blending results in a PCR- PET material that may be further processed by forming into a thermoplastic article, such as extruded pellets or molded articles.

[0059] The chelant, whether in the form of a liquid solution or a solid masterbatch, may be continuously added to the extruder at a feeding zone that is prior to the polymer melting zone. Additional or alternative blending of liquid chelant with rPET may occur by immersing the rPET flake in a solution containing the chelant then dewatering the PCR-PET flake, or by spraying the surface of the PCR-PET flake with a solution of the chelant followed by agitation.

[0060] In any of the exemplary aspects, the liquid chelant may be provided either pre-blended with rPET flake prior to addition to the extruder or added directly to the extruder feeding zone. Alternatively, or in addition to the liquid chelant, the chelant may be provided as a solid masterbatch and added to the extruder at the feeding zone. As mentioned above, in aspects whereby the chelant is in the form of a liquid or a solid masterbatch, the inclusion of the processing additive is optional and may, in some embodiments, be excluded.

[0061] It should be understood one or more melt-processing steps can be used when making a thermoplastic article by melt-processing in accordance with the disclosed invention.Methods of Making Thermoplastic Articles

[0062] Various aspects of the present disclosure are directed to methods of making a thermoplastic article formed (using one or more melt-processing steps) at least in part from rPET flakes. The thermoplastic article comprises a blend of virgin (unprocessed) thermoplastic material and PCR-PET material. In any of the aspects contemplated herein, the thermoplastic article may comprise an increased ratio of post-consumer material than previously possible, such as in processes whereby rPET flake was coated with an aqueous chelant without the additive package introduced herein. Thermoplastic articles such as bottles, containers, sheets, formed parts, pellets, fibers, and the like can be made from the PCR-PET material produced according to the present invention using conventional methods such as injection molding, blow molding, extrusion, thermoforming, fiber spinning, and the like.

[0063] The method for making a thermoplastic article from PCR-PET includes the steps of: (a) providing a plurality of rPET flake(s); (b) providing a chelant and optional processing additive(s); (c) forming a PCR-PET blend by mixing the rPET flakes with the chelant and optional additive(s); and (d) melt-processing the PCR-PET blend to provide the thermoplastic article; wherein steps (a), (b), and (c) each occurs prior to step (d). Optionally, additional PET material (either virgin PET or recycled / reclaimed PET) may be melt-blended with the PCR-PET blend in step (d).

[0064] According to various aspects, melt-processing step (d) may include the addition of virgin thermoplastic material, particularly virgin PET material, and forming a recycled thermoplastic article therefrom. Step (d) may also optionally include more than one melt-processing step to provide the thermoplastic article. For example, the PCR-PET material and optional virgin PET may be extruded into pellets, as a first melt-processing step, and the pellets undergo solid state polymerization (SSP) before being used in a melt-forming process, such as molding or extrusion, as a second meltprocessing step, to make the end-use thermoplastic article.

[0065] In some embodiments, step (d) includes only one melt-processing step to provide the thermoplastic article. For example, the PCR-PET flake is melt-processed in an extruder and directly formed into the end-use thermoplastic article such as a sheet.

[0066] Different process steps and routes that can be used to provide thermoplastic articles formed (using one or more melt-processing steps) at least in part from rPET flake are well known to those skilled in the art of thermoplastics polymer engineering. For example, typical process steps and routes are described by European PET Bottle Platform, "PET Recycling Test Protocol: Website version" (September 2017).

[0067] Subsequent forming, extrusion, molding, thermoforming, foaming, calendering, and / or other processing techniques are well known to those skilled in the art of thermoplastics polymer engineering. Without undue experimentation but with reference to publications such as "Extrusion, The Definitive Processing Guide and Handbook", "Handbook of Molded Part Shrinkage and Warpage", "Specialized Molding Techniques", "Rotational Molding Technology", and "Handbook of Mold, Tool and Die Repair Welding", all part of the Plastics Design Library series published by Elsevier, one can make thermoplastic articles using the principles of the disclosed invention.

[0068] According to various aspects, the thermoplastic articles formed in accordance with the preset inventive concepts has reduced discoloration, compared to thermoplastic articles formed with either untreated rPET flakes or rPET flakes treated with an aqueous carrier in the absence of one or more processing additives. Reduction of discoloration may be quantified, in some embodiments, according to the L*a*b* color scale, whereby L* indicates lightness, a* is the red / green coordinate, and b* is the yellow / blue coordinate. In any of the aspects contemplated herein, the thermoplastic article formed with a PCR-PET blend comprising rPET flake, chelant, and optional additive package demonstrates a reduction in b* of at least 25%, compared to an otherwise comparable thermoplastic article formed with conventional, untreated rPET flakes, including for example, a reduction in b* of at least 30%, at least 35%, at least 40%, at least 45%, at least 50% and at least 55%.

[0069] Because PCR-PET flake treated in accordance with the present invention results in resin with reduced discoloration and lower levels of generation of NIAS such as benzene, food and beverage containers containing PCR-PET can be made with improved color and reduced potential for migration of NIAS such as benzene into the product. Consequently, higher levels of PCR-PET and lower quality PCR-PET may be utilized for these packages.

[0070] The level of PCR-PET that may be utilized in a specific product may depend on factors such as application, product color, etc. For example, PET bottles, such as soft drink bottles, generally include conventional PCR-PET (without employing the subject inventive concepts) in amountsbetween 5 wt.% and 25 wt.%. However, by implementing the technology disclosed in the present inventive concepts, the amount of PCR-PET may be increased by a factor of at least 1.5, or a factor of at least 2. Additionally, the yellowness of the PCR-PET is decreased by at least 25%, or at least 50%, as demonstrated by the following examples.EXAMPLES

[0071] The following non-limiting examples illustrate the efficacy of solid chelant and / or nonaqueous chelant solutions, with an optional additive package, to reduce discoloration in melt- processed PCR-PET.Example 1 - Batch Process

[0072] Various PCR-PET samples were prepared comprising a variety of compositions. The Control 1 flake included post-consumer clear washed rPET bottle flake. The material was split into equal portions. One portion (Comparative Example la) was prepared by blending the rPET flake with 1% by weight of an aqueous solution containing 2.5% phosphoric acid aqueous chelant, in accordance with the disclosure of WO 2022 / 147213 Al, such that the flake surface was coated with 250 ppm by weight of phosphoric acid. Another portion (Comparative Example lb) was treated with an additive blend comprising 400 ppm of a phosphite antioxidant (Doverphos S- 9228®); 200 ppm of acid scavenger (DHT®-4C), and 200 ppm sterically hindered primary phenolic antioxidant stabilizer (Irganox® 1010). A final portion (Example 1) was prepared by treating the rPET flake with the additive blend of Comparative Example lb and the aqueous chelant of Comparative Example la. Both the treated and the untreated flakes of PCR-PET were dried at 160 °C for approximately 4 hours before further processing. All samples were formed into strands through a 27 mm twin-screw extruder with a low shear screw design at approximately 290 °C. The strands were cooled in a water bath and subsequently cut into pellets. The pellets were dried, crystallized in a vacuum oven for approximately 3 hours at 160 °C, and subsequently solid state polymerized (SSP) in the vacuum oven for approximately 6 hours at 220 °C. The dried and SSP pellets were molded into 3 mm plaques at approximately 280 °C on a Milacron Injection Molding machine. The resulting plaques were measured for color properties in transmission mode. The four samples tested were the untreated Control 1 flake, Comparative Example la, Comparative Example lb, and Example 1.

[0073] The Samples were tested for b* color and % b* reduction, compared to Control 1. The results are summarized in Table 1.TABLE 1

[0074] The results summarized in Table 1 show that Example 1, which includes blending the rPET flake with both aqueous chelant and an additive package exhibits a significant reduction in b*, compared to rPET flakes treated only with the aqueous chelant (Comparative Example la) and rPET flakes blended only with the additive package (Comparative Example lb). The change in the value of b*, which describes the color of the sample on a blue to yellow continuum indicates that both the comparative examples can reduce the yellowness compared to untreated control flake. However, when both treatments are applied as in the example of this invention, the yellowness of the materials is significantly decreased.Example 2 - Continuous Process

[0075] Another sample of washed, clear rPET bottle flake was tested in a similar manner as Example 1, except that the flake was not pretreated with a phosphoric acid solution before drying, but rather the phosphoric acid solution was incorporated into the flake by pumping the appropriate amount into the feedthroat of the extruder. In addition, a higher amount of additives were included in the additive package. The additive package included: 1200 ppm Doverphos S-9228®, 600 ppm DHT® -4C and 600 ppm Irganox® 1010. All other steps in the process were consistent with Example 1.

[0076] The untreated Control 2 flake was compared to treatment with the additive package (Comparative Example 2a), treatment with 200 ppm of aqueous phosphoric acid (Comparative Example 2b), and Example 2, which was prepared by melt-blending rPET flake treated with an aqueous phosphoric acid chelant according to Comparative Example 2b with the additive package of Comparative Example 2a, in accordance with the present inventive concepts.

[0077] The PCR-PET materials of each sample were tested for b* color and % b* reduction, compared to Control 2. The Results are summarized in Table 2.

[0078] As illustrated in Table 2, below, the % improvement in color for the Example 2 was 2.5 to 3.5 times higher than the untreated Control 2. The amount of yellowness improvement is alsolarger than in Example 1, which may be a characteristic of the quality of the PET recycle flake, or a function of the amount of additives added, or the method of treating the flake by pumping into the extruder. It is likely that all three variables were factors.TABLE 2Example 3 - Solid Chelant Masterbatch

[0079] A similar method of preparing plaques from another sample of rPET flake was executed with two different additive package combinations. Additive package 3(a) included 1200 ppm Doverphos S-9228®, 600 ppm DHT® -4C and 600 ppm Irganox® 1010. Additive package 3(b) included 1200 ppm Doverphos S-9228® and 150 ppm DHT® -4A2. The phosphoric acid chelant was introduced in two ways: 1) the first method was identical to Example 2, and the second method was through the feeding of a solid masterbatch containing 2% active phosphoric acid in a PET carrier. In all cases, the targeted level of phosphoric acid was 200 ppm in the final plaques. Comparative Example 3(a) included Control 3 flake with additive package 3(a); Example 3(a)-l included the Control 3 flake with additive package 3(a) and 200 ppm phosphoric acid (as in Example 2); Example 3(a)-2 included Control 3 flake with additive package 3(a) and 200 ppm phosphoric acid (solid masterbatch form). Comparative Example 3(b) included the Control 3 flake with additive package 3(b); Example 3(b)-l included the Control 3 flake with additive package 3(b) and 200 ppm phosphoric acid (as in Example 2 above); Example 3(b)-2 included the Control 3 flake with additive package 3(b) and 200 ppm phosphoric acid (solid masterbatch form).

[0080] The PCR-PET materials of each sample were tested for b* color and % b* reduction, compared to the Control.

[0081] Tables 3(a) and 3(b) illustrate that the solid masterbatch method of introducing phosphoric acid chelant is substantially as effective as using an aqueous solution. In both cases, yellowness reduction b* of 50% or higher was obtained vs the Control 3 flake, and the color was much improved compared to the use of additives alone. In some cases, as in 3(b), the additive package is largely ineffective without the addition of the phosphoric acid chelant. This is postulated to be a function of the contaminant composition of the flake.TABLE 3(a)TABLE 3(b)Example 4

[0082] Samples were made as described in the above Examples. All samples with phosphoric acid chelant utilized a masterbatch of 2 wt.% active phosphoric acid in PET fed at 1% of the overall rate to achieve 200 ppm in the final pellets. Example 4 included Control 4(a) rPET flake and Control 4(b) rPET flakes, respectively. Comparative Example 4(a) included Control 4(a) flake and 200 ppm phosphoric acid (solid masterbatch). Comparative Example 4(b) included Control 4(b) flake and an additive package comprising: 1200 ppm Doverphos S-9228®, 300 ppm DHT®-4A2 and 400 ppm Irganox® 1010. Example 4 included Control 4(b) flake with the additive blend according to Comparative Example 4(b) and 200 ppm phosphoric acid (solid masterbatch) as in Comparative Example 4(a). With this particular batch of rPET flake, it can be clearly seen that additives or phosphoric acid alone result in a certain level of color improvement, but the combination of the technologies shows clearly superior performance.TABLE 4Example 5

[0083] Samples were prepared as described in the above Examples. Comparative Example 5 included the Control 5 rPET flake and an additive package comprising 1000 ppm Doverphos S- 9228®, 200 ppm DHT® -4A2 and 400 ppm Irganox® 1010. Example 5 included the Control flake, the additive package of Comparative Example 5, and a masterbatch of 2 wt.% active phosphoric acid in PET fed at 1% of the overall rate to achieve 200 ppm in the final pellets.TABLE 5

[0084] As illustrated in Table 5, the % improvement in color for Example 5 was significantly higher than Comparative Example 5.Example 6

[0085] Samples were prepared as described in the above Examples. The exemplary samples were made rPET flakes treated with differing levels of phosphoric acid chelant in combination with an additive package. The additive package of Example 6 included 1000 ppm Doverphos S-9228®, 200 ppm DHT® -4A2 and 400 ppm Irganox® 1010. Example 6(a) included the additive package and 50 ppm phosphoric acid (solid masterbatch). Example 6(b) included the additive package and 100 ppm phosphoric acid (solid masterbatch). Example 6(c) included the additive package and 200 ppm phosphoric acid (solid masterbatch).

[0086] The data in Table 6, below, demonstrates that a range of phosphoric acid loadings are effective in significantly reducing color of rPET flake when used in combination with the additive package, according to the present inventive concepts.TABLE 6Example 7

[0087] Another sample of rPET flake was obtained which was significantly contaminated, as shown in Table 7 by the high haze and lower values of L. Yellowness was in the general range of previous flake samples. The samples were produced on a Single Screw Extruder utilizing liquid dispersions of an additive package and phosphoric acid chelant in a non-aqueous acetylated monoglyceride carrier (Grindsted Soft N Safe, IFF). The additive package 7(a) included 500 ppm Doverphos S-9228® and 500 ppm Irganox® 1010. The additive package 7(b) included 1000 ppm Doverphos S-9228® and 1000 ppm Irganox® 1010. Comparative Example 7-1 included Control 7 flake and additive package 7(a) and Comparative Example 7-2 included Control 7, and 240 ppm phosphoric acid in non-aqueous carrier. Example 7 includes Control 7, 220 ppm phosphoric acid in non-aqueous carrier and the additive blend 7(b). The materials were crystallized, SSP, and molded using larger scale stirred processors rather than a static vacuum oven as in Examples 1-6. The PCR- PET materials of each sample were tested for b* color and % b* reduction, compared to the Control. The test results are shown in Table 7.TABLE 7

[0088] The sample of Example 7 shows significantly improved yellowness compared to the use of additive package alone or the application of phosphoric acid alone. It also indicates that for certain types of contaminated flakes, improvement in haze and light transmission (as measured by L*) may be seen with the technology of this invention.

[0089] Although the present invention has been described with reference to particular means, materials and embodiments, from the foregoing description, one skilled in the art can easily ascertain the essential characteristics of the present invention and various changes and modifications can be made to adapt the various uses and characteristics without departing from the spirit and scope of the present invention as described above and set forth in the attached claims.

[0090] From the foregoing, it will be seen that this invention is one well-adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure.

[0091] It will be understood that certain features and subcombinations are of utility and can be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

[0092] While specific elements and steps are discussed in connection to one another, it is understood that any element and / or steps provided herein is contemplated as being combinable with any other elements and / or steps regardless of explicit provision of the same while still being within the scope provided herein. Since many possible embodiments can be made of the disclosure without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

[0093] All documents cited herein are incorporated herein by reference in their entirety unless otherwise specified. The citation of any document is not to be construed as an admission that it is prior art with respect to the disclosed invention.

[0094] It will be apparent that modifications and variations are possible without departing from the scope of the disclosure defined in the appended claims. Although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

Claims

CLAIMSWhat is claimed is:

1. A post-consumer recycled polyethylene terephthalate (PCR-PET) blend comprising: at least one recycled polyethylene terephthalate (rPET) flake; a chelant; and at least one processing additive.

2. The PCR-PET blend of claim 1, wherein the chelant is a liquid chelant composition comprising active chelant dispersed in a liquid carrier.

3. The PCR-PET blend of claim 2, wherein the liquid carrier is a non-aqueous carrier.

4. The PCR-PET blend of claim 3, wherein the non-aqueous carrier is selected from the group consisting of polyalkylene glycol, acetylated monoglycerides, aliphatic dibasic acid esters, benzoate esters, trimellitate esters, polyesters, citrates, food oils, bio-based plasticizers, and mixtures thereof.

5. The PCR-PET blend of claim 1, wherein the chelant is a chelant masterbatch comprising a solid component of active chelant and a resin.

6. The PCR-PET blend of any one of claims 1 to 5, wherein the active chelant is present in the PCR-PET blend in an amount from about 1 to about 5000 ppm.

7. The PCR-PET blend of any one of claims 1 to 6, wherein the processing additive is present in the PCT-PET blend in an amount between 100 and 10,000 ppm.

8. The PCR-PET blend of any one of claims 1 to 7, wherein the processing additive is selected from the group consisting of hindered phenols, organic phosphites, inorganic phosphites, antioxidants, scavengers, flow modifiers, chain extenders, odor absorbers, and mixtures thereof.

9. The PCR-PET blend of any one of claims 1 to 8, wherein the processing additive is present as an additive package comprising a blend of two or more of antioxidant, an acid scavenger, and a halogen scavenger.

10. The PCR-PET blend of any one of claims 8 or 9, wherein the antioxidant includes a phosphite antioxidant, phenolic antioxidant, or mixtures thereof.

11. The PCR-PET blend of any one of claims 8 to 10, wherein the scavenger includes calcium stearate, zinc stearate, zinc oxide, hydrotalcite, or mixtures thereof.

12. The PCR-PET blend of any one of claims 8 to 11, the additive package may include 200 ppm to 2000 ppm of one or more antioxidants and 50 ppm to 1500 ppm of one or more scavengers.

13. The PCR-PET blend of any one of claims 1 to 12, wherein the chelant is selected from the group consisting of carboxylic acids and salts thereof; phosphoric acids and salts thereof; phosphonic acids and salts thereof; and combinations thereof.

14. The PCR-PET blend of any one of claims 1 to 13, wherein the chelant is selected from the group consisting of phosphoric acid; pyrophosphoric acid, editronic acid, alkyl phosphonic acids, sodium acid pyrophosphate; and combinations thereof.

15. An extruded polyethylene terephthalate (PET) material comprising a blend of: virgin PET; and recycled PET (rPET), wherein the rPET comprises: a liquid chelant composition comprising active chelant dispersed in a liquid carrier; and at least one processing additive, wherein the extruded PET material has a b* value that is at least 25% lower than the b* value of an otherwise comparative extruded PET material that does not include the chelant masterbatch and processing additive.

16. The extruded PET material of claim 15, wherein the extruded PET material is in the form of one or more pellets.

17. The extruded PET material of any one of claims 15 or 16, wherein the active chelant is present in an amount from about 1 to about 5000 ppm.

18. The extruded PET material of any one of claims 15 to 17, wherein the chelant is selected from the group consisting of carboxylic acids and salts thereof; phosphoric acids and salts thereof; phosphonic acids and salts thereof; and combinations thereof.

19. A method of treating recycled polyethylene terephthalate (rPET) flake, the method comprising the steps of: forming a post-consumer polyethylene terephthalate (PCR-PET) material by melt processing: at least one recycled polyethylene terephthalate (rPET) flake; a liquid chelant composition comprising active chelant dispersed in a liquid carrier; and at least one processing additive, wherein the PCR-PET material has a b* value that is at least 25% lower than the b* value of an otherwise comparative extruded PET material that does not include the chelant masterbatch and optional processing additive.

20. The method of claim 19, further including a step pelletizing the PCR-PET material, forming a plurality of pellets.

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