Methods for recycling containers including optimization of antioxidant addition to prevent yellowing in PCR flake-to-pellet conversion

Abstract

A method for converting post-consumer recycled (PCR) flakes of polyethylene terephthalate (PET) to pellets as part of a container recycling procedure, the method including: adding triphenyl phosphite antioxidant to a reactor at a concentration of 0.05 wt.% to 0.15 wt.%; coating the PCR flakes with the triphenyl phosphite in the reactor; and converting the PCR flakes to the pellets in an extruder after coating the PCR flakes with the triphenyl phosphite to reduce yellowing of the pellets during the conversion.

Description

Attorney Docket No. 8330-000744-WO-PCMETHODS FOR RECYCLING CONTAINERS INCLUDING OPTIMIZATION OF ANTIOXIDANT ADDITION TO PREVENT YELLOWING INPCR FLAKE-TO-PELLET CONVERSIONFIELD

[0001] The present disclosure relates to methods for recycling polyethylene terephthalate (PET) including optimization of antioxidant addition to prevent yellowing in post-consumer recycled (PCR) flake-to-pellet and flake-to-molded part conversion.BACKGROUND

[0002] Containers made of polyethylene terephthalate (PET) are often recycled after use. Recycling is environmentally friendly, conserves resources, and may reduce costs. While current recycling systems and methods are suitable for their intended use, they are subject to improvement. For example, undesirable yellowing of PET may occur during the conversion of PCR PET flake into pellets or final molded parts. The present disclosure addresses this yellowing phenomenon.SUMMARY

[0003] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0004] The present disclosure provides for, in various features, a method for converting post-consumer recycled (PCR) flakes of polyethylene terephthalate (PET) to pellets as part of a container recycling procedure, the method including: adding an antioxidant to a flake-to-pellet conversion process at a concentration of 0.05 wt.% to 0.15 wt.%; coating the PCR flakes with the antioxidant; and converting the PCR flakes to the pellets in an extruder after coating the PCR flakes with the antioxidant to reduce yellowing of the pellets during the conversion.

[0005] In further features, the antioxidant is a triphenyl phosphite based compound.

[0006] In further features, the triphenyl phosphite based compound is blended with phosphoric acid.

[0007] In further features, the triphenyl phosphite based compound is a blend of at least 2 different forms of triphenyl phosphite.Attorney Docket No. 8330-000744-WO-PC

[0008] In further features, the triphenyl phosphite based compound is blended with hindered phenols or hindered amines.

[0009] In further features, the triphenyl phosphite based compound is blended with diphosphites or monophosphites.

[0010] In further features, the antioxidant is added to the flakes to pellet conversion process at a reactor, decontamination tank, or flake to pellet extruder.

[0011] In further features, the antioxidant is added prior to a melt filtration step.

[0012] In further features, the antioxidant is heated to between 35 C and 90 C before being added to the flake-to-pellet conversion process.

[0013] In further features, the antioxidant has a viscosity of between 40 cP and 1000 cP before being added to the flake-to-pellet conversion process.

[0014] In further features, a concentration ratio of the antioxidant is configured to prevent reduction of antimony trioxide to elemental antimony.

[0015] In further features, the reactor is an agitated vessel under temperature and vacuum.

[0016] In further features, the reactor is configured to pre-crystallize the PCR flake before the extruder.

[0017] In further features, the reactor is configured to raise an intrinsic viscosity of the PCR flake before the extruder.

[0018] In further features, the decontamination tank is designed to remove volatile substances.

[0019] In further features, the extruder is configured to form the pellets.

[0020] In further features, the antioxidant reduces yellowing of the pellets during subsequent solid state polymerization.

[0021] In further features, the antioxidant prevents yellowing of the pellets during subsequent drying of the pellets.

[0022] The present disclosure also provides for, in various features, a method for converting post-consumer recycled (PCR) flakes of polyethylene terephthalate (PET) to a molded part, the method includes: adding an antioxidant to a flake-to-molded part conversion process at a concentration of 0.05 wt.% to 0.15 wt.%; coating the PCR flakes with the antioxidant; and converting the PCR flakes to a molded part after coating the PCR flakes with the antioxidant to reduce yellowing of the molded part.

[0023] In further features, the molded part is injection molded or compression molded.Attorney Docket No. 8330-000744-WO-PC

[0024] In further features, the molded part is a preform configured for blow molding into a final container.

[0025] In further features, the antioxidant is a triphenyl phosphite based compound.

[0026] In further features, the triphenyl phosphite based compound is blended with phosphoric acid.

[0027] In further features, the triphenyl phosphite based compound is a blend of at least two different forms of triphenyl phosphite.

[0028] In further features, the triphenyl phosphite based compound is blended with hindered phenols or hindered amines.

[0029] In further features, the triphenyl phosphite based compound is blended with diphosphites or monophosphites.

[0030] In further features, the antioxidant is added to the flakes to molded part conversion process at a reactor, decontamination tank, or extruder.

[0031] In further features, the antioxidant is added prior to a melt filtration step.

[0032] In further features, the antioxidant is heated to between 35 C and 90 C before being added to the flake-to-molded part conversion process.

[0033] In further features, the antioxidant has a viscosity of between 40 cP and 1000 cP before being added to a flake-to-molded part conversion process.

[0034] In further features, a concentration ratio of the antioxidant is configured to prevent reduction of antimony trioxide to elemental antimony.

[0035] In further features, the reactor is an agitated vessel under temperature and vacuum.

[0036] In further features, the reactor is configured to pre-crystallize the PCR flake before the extruder.

[0037] In further features, the reactor is configured to raise an intrinsic viscosity of the PCR flake before the extruder.

[0038] In further features, the decontamination tank is designed to remove volatile substances.

[0039] The present disclosure also provides for, in various features, a method for converting post-consumer recycled (PCR) flakes of polyethylene terephthalate (PET) to pellets as part of a container recycling procedure. The method includes: adding an antioxidant to a reactor at a concentration of 0.05 wt.% to 0.15 wt.%; coating the PCR flakes with the antioxidant; and converting the PCR flakes to the pellets in an extruderAttorney Docket No. 8330-000744-WO-PC after coating the PCR flakes with the antioxidant to reduce yellowing of the pellets during the conversion, wherein the antioxidant is a triphenyl phosphite based compound.

[0040] In further features, the triphenyl phosphite based compound is blended with phosphoric acid.

[0041] In further features, the triphenyl phosphite based compound is a blend of at least two different forms of triphenyl phosphite.

[0042] In further features, the triphenyl phosphite based compound is blended with at least one of hindered phenols, hindered amines, diphosphites, monophosphites.

[0043] In further features, the antioxidant is heated to between 35°C and 90°C to raise viscosity to between 40 cP and 1000 cP before being added to the reactor.

[0044] In further features, a concentration ratio of the antioxidant is configured to prevent reduction of antimony trioxide to elemental antimony.

[0045] In further features, the reactor is an agitated vessel under temperature and vacuum configured to pre-crystallize the PCR flake and raise an intrinsic viscosity of the PCR flake before the extruder.

[0046] In further features, the extruder is configured to form the pellets.

[0047] In further features, the antioxidant reduces yellowing of the pellets during subsequent solid state polymerization, drying of the pellets, and molding of a final part.

[0048] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

[0049] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.DRAWINGS

[0050] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0051] FIG. 1 illustrates an exemplary recycling method in accordance with this present disclosure; and

[0052] FIG. 2 illustrates an additional exemplary recycling method in accordance with the present disclosure.Attorney Docket No. 8330-000744-WO-PC

[0053] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.DETAILED DESCRIPTION

[0054] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0055] The present disclosure pertains to innovative methods, systems, and processes designed to enhance the recycling of post-consumer recycled (PCR) polyethylene terephthalate (PET) containers. Specifically, it addresses the challenge of yellowing that occurs during the conversion of PCR PET flake into pellets or final molded parts, a process critical for maintaining the quality and appearance of recycled materials.

[0056] The yellowing phenomenon is primarily attributed to the formation of chromophores, such as quinones, resulting from the degradation of the benzene ring in PET. To combat this issue, the present disclosure emphasizes the incorporation of antioxidants, particularly triphenyl phosphite, during the flake-to-pellet conversion. Key components of the present disclosure include optimization of let-down ratio (LDR), blending methodology, reactor process control, and antimony catalyst management.

[0057] Optimization of let-down ratio (LDR) is the concentration of triphenyl phosphite that prevents yellowing. Concentrations below 0.05 wt.% are ineffective, while concentrations exceeding 0.15 wt.% can lead to undesirable darkening due to the reduction of antimony trioxide (Sb20a) to elemental antimony.

[0058] With respect to blending methodology, the present disclosure proposes an effective pre-coating method where PCR flake is coated with triphenyl phosphite prior to the extrusion process. This method enhances the interaction between the antioxidant and the flake, improving its protective efficacy. Additional techniques for antioxidant introduction, such as direct addition during the extrusion phase, are also considered.

[0059] With respect to reactor process control, the present disclosure provides for an optimal reactor design in which the antioxidant is added during the precrystallization of PCR flake. This ensures effective coating and protection of the material before extrusion, thereby maintaining intrinsic viscosity and minimizing degradation.Attorney Docket No. 8330-000744-WO-PC

[0060] With respect to antimony catalyst management, the present disclosure provides for the management of antimony trioxide, which is a catalyst used in PET production. The recycling system of the present disclosure prevents the reduction of antimony trioxide to elemental antimony, which contributes to discoloration. The optimized LDR for antioxidants prevents this reduction while maintaining the quality of the final product.

[0061] The present disclosure thus presents a refined methodology for incorporating antioxidants in the recycling of PET, focusing on minimizing yellowing during the conversion process. By optimizing both the LDR and the blending techniques, the present disclosure enhances the protection against discoloration, which ultimately improves the quality and utility of recycled PET pellets and final parts.

[0062] The present disclosure relates to methods, systems, and processes for recycling polyethylene terephthalate (PET), such as PET containers that include the addition of antioxidants to post-consumer recycled (PCR) PET flake during a flake conversion process, which prevents yellowing in PCR flake-to-pellet and flake-to- molded part conversion. The resulting pellets, molded parts (such as container preforms), and subsequent blow molded containers made from the recycled PET exhibit reduced yellowing.

[0063] To quantify changes in color, the CIELAB color system is employed, which is a three-dimensional model comprising three axes: L* for lightness; a* for the red-green component; and b* for the blue-yellow component. Yellowing, specifically, can be assessed through shifts in the b* channel. With respect to the present disclosure, yellowing is evaluated by monitoring changes in the b* value of 3mm thick plaques injection-molded from PCR pellets that include an antioxidant at a specified weight percentage. Before subjecting the pellets to solid-state polymerization, the b* value of these plaques is expected to decrease by approximately 2 units compared to plaques molded from PCR pellets without the antioxidant. After undergoing solid-state polymerization, plaques molded from PCR pellets containing the antioxidant at the preferred weight percentage are likewise anticipated to show a reduction in the b* value by approximately 2 units relative to plaques molded from solid-state polymerized PCR pellets that lack the antioxidant. The change in b* can be precisely measured using a colorimeter, such as the Hunter Lab ColorQuest XE dual beam xenon flash spectrophotometer, or other equivalent spectrophotometric equipment.Attorney Docket No. 8330-000744-WO-PC

[0064] The present disclosure addresses the following two areas in particular: (1) the let-down ratio (LDR) of the antioxidant; and (2) the method of blending the antioxidant with the PCR flake. The optimized procedure of the present disclosure includes the use of triphenyl phosphite antioxidant at a particular concentration or within a concentration range, and the pre-coating of flake with this additive before extrusion to maximize effectiveness and prevent discoloration.

[0065] Post-consumer recycled (PCR) polyethylene terephthalate (PET) may experience yellowing during the flake conversion process. This yellowing is primarily due to the formation of chromophores, such as quinones, from the degradation of the benzene ring in PET. To mitigate this issue, antioxidants and stabilizers are employed to inhibit the formation of these chromophores.

[0066] The present disclosure provides for a yellowing prevention pathway. The yellowing prevention pathway includes the following steps: (1 ) metals promote autoxidation reactions, which form free radicals; (2) free radicals react with PET and abstract hydrogen from terephthalate ring; (3) resulting aryl radical reacts with hydrogen to form a peroxide (ROOH); (4) peroxides decompose to form hydroxyterephthalates; and (5) quinone formation via further oxidation of dihydroxy acid. Quinones are “yellow” color bodies formed from benzene ring degradation.

[0067] The present disclosure provides for a multi-step process for quinone formation. In a first step, metals promote autoxidation reactions, which form free radicals. In a second step, free radicals react with PET and abstract hydrogen from a terephthalate ring. In a third step, a resulting aryl radical reacts with hydrogen to form a peroxide (ROOH). In a fourth step, peroxides decompose to form hydroxyterephthalates. In a fifth step, quinone formation occurs via further oxidation of dihydroxy acid.

[0068] Secondary antioxidants, such as phosphites and thioethers, are crucial in this process as they react with hydroperoxides formed during the recycling process. These antioxidants protect the polymer from degradation and discoloration by converting reactive hydroperoxides into stable, non-reactive products. Among these, triphenyl phosphites have shown considerable effectiveness in preventing yellowing.Attorney Docket No. 8330-000744-WO-PCThe antioxidant may be a compound containing one or more triphenyl phosphite variants, and may also be blended with phosphoric acid. In order to enhance the duration of the antioxidant effect, the compound may also be blended with hindered phenols, hindered amines, diphosphites, or monophosphites.

[0069] The following illustrates a phosphite antioxidant mechanism:

[0070] The triphenyl phosphite is both (1 ) oxidized preferentially, and (2) resistant to hydrolysis:

[0071] An example embodiment of a triphenyl phosphite based compound is the following:Attorney Docket No. 8330-000744-WO-PCPhosphoric Acid Triphenyf Phosphite1 ) Optimization of Let-Down Ratio (LDR)

[0072] The LDR of the antioxidant, particularly triphenyl phosphite, plays a critical role in the effectiveness of the yellowing prevention process. Addition of an antioxidant, such as triphenyl phosphite, at concentrations below 0.05 wt.% results in diminished effectiveness in preventing yellowing (suboptimal addition). At concentrations above 0.15 wt.%, triphenyl phosphite causes a reduction of antimony trioxide (Sb20a) to elemental antimony, which leads to a darkening of the PCR material.2) Additional Optimization of Let-Down Ratio (LDR)The present disclosure provides for methods of blending the antioxidant with PCR flake. For example, the present disclosure includes a pre-coating method in which PCR flake is pre-coated with an antioxidant, such as triphenyl phosphite, prior a to melt stream filtration step, in a dedicated reactor before extrusion, which has been found to be the most effective. This method allows the antioxidant to adhere to the flake surface, ensuring better interaction and protection during the extrusion process. The present disclosure further provides for an extruder addition, which includes introducing the additive directly into the pre-melted flake within the extruder. In some applications, the effectiveness of the pre-coating method is greater than introducing the additive directly into the pre-melted flake within the extruder. The antioxidant can also be added to a decontamination tank configured to remove volatile substances, prior to the reactor. The antioxidant compound is typically heated to between 35°C and 90°C to raise the viscosity to between 40 cP and 1000 cP, for ease of delivery to the process, prior to the melt filtration step.Attorney Docket No. 8330-000744-WO-PC3) Reactor Process

[0073] An optimal location for adding the secondary antioxidant is within a reactor configured to pre-crystallize the PCR flake and raise its intrinsic viscosity (IV) before extrusion. The reactor includes an agitated vessel operating under controlled temperature and vacuum conditions. Adding an antioxidant compound such as triphenyl phosphite to the reactor enables it to coat the flake effectively, which protects the material before it undergoes the extrusion process.4) Antimony Catalyst Management

[0074] The present disclosure provides for effective management of an antimony catalyst. For example, antimony trioxide is used as a polycondensation catalyst in PET production, and is controlled to avoid reduction to elemental antimony. Optimized LDR for antioxidants such as triphenyl phosphite prevents the reduction of antimony trioxide to elemental antimony, thereby avoiding darkening of the PCR material.

[0075] The present disclosure provides for optimization of the LDR for the antioxidant to both prevent “yellowing” and prevent the reduction of the antimony catalyst, which causes the final container to take on a grey or greyish color. Elemental antimony [Sb(0)] is a lustrous grey metal. An example of an antimony polycondensation catalyst is antimony trioxide (Sb20a), which is a white powder. When used for the production of virgin PET, glycol concentration and temperature are controlled to prevent the reduction of antimony catalyst to elemental antimony. In the presence of excess antioxidant, antimony catalyst reduces to elemental antimony by way of the following mechanism:

[0076] FIG. 1 illustrates an exemplary recycling method 110 in accordance with this present disclosure for recycling polyethylene terephthalate (PET), such as any suitable PET container (including any suitable PCR, PET container). The method 110 may be performed using any suitable mechanical recycler and any suitable flake-to- pellet extruder. At block 120 of the method 110, the PET is separated and baled at anyAttorney Docket No. 8330-000744-WO-PC suitable materials recovery facility (MRF). The method 110 proceeds to block 130 with sub-blocks 140-152, where the PET is separated and washed. Specifically, at block 140 a trommel process is performed whereby water and friction removes closures and some labels of PET containers. At block 142, re-sort is performed, which includes color stream separation / removal of metals, paper, polyolefins, etc. At block 144, grinding is performed, which shreds packages. At block 146, a float sink tank, for example, is used to separate polyolefins, pulp, and labels. At block 148, a wash tank is used to clean flake (glue / food / HPC). At block 150, another float sink tank process is performed to separate polyolefins, pulp, and labels. At block 152, elutriation is performed to separate pulp and labels and / or dry flakes.

[0077] From the PET separation and washing at block 130, the method 110 proceeds to block 160 where flake to final pellet takes place. At block 170, flake decontamination takes place including volatile removal pre-extrusion. At block 172, the antioxidant is added to the flake to pellet process at a reactor, decontamination tank, or flake to pellet extruder. At block 174, flake extrusion takes place, such as with a twin- screw extrusion machine. At block 176, melt filtration is performed. At block 178, pelletization takes place, and at block 180 pellet crystallization takes place. From block 180, the method 110 proceeds to block 190 where solid-state polymerization (SSP) takes place.

[0078] FIG. 2 illustrates another method 210 in accordance with the present disclosure for recycling PET, such as any suitable PET container (including any suitable PCR, PET container). The method 210 converts flake to any suitable molded part, such as a preform configured to form a container. At block 220 of the method 210, the PET is separated and baled at any suitable materials recovery facility (MRF). The method 210 proceeds to block 230 with sub-blocks 240-252, where the PET is separated and washed. Block 230 (and sub-blocks 240-252) is similar to block 130 (and sub-blocks 140-152). Thus, the description of block 130 (and sub-blocks 140-152) also describes block 230 (and sub-blocks 240-252).

[0079] Unlike the method 110, the method 210 includes at block 260 a process of converting PET flake to a molded part. The block 260 includes blocks 270, 272, 274 and 276, which are the same as, or substantially similar to, blocks 170, 172, 174, and 176 of the method 110. Thus, the description of the blocks 170, 172, 174, and 176 also describes the method 210 at blocks 270, 272, 274, and 276. From block 276, the method 210 proceeds to block 290. At block 290, the PET flake is used for injection orAttorney Docket No. 8330-000744-WO-PC compression molding of any suitable part, such as any suitable container preform, for example.Conclusion

[0080] This invention provides a refined approach to the addition of antioxidants in the recycling of PET, particularly focusing on preventing yellowing during the flake conversion process. By optimizing both the LDR and the method of blending, the process ensures enhanced protection against discoloration, thereby improving the quality, appearance, and usefulness of the final recycled PET.

[0081] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

[0082] Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0083] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring theirAttorney Docket No. 8330-000744-WO-PC performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

[0084] When an element or layer is referred to as being "on," “engaged to,” "connected to," or "coupled to" another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," “directly engaged to,” "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0085] Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

[0086] Spatially relative terms, such as “inner,” “outer,” "beneath," "below," "lower," "above," "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the example term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

Claims

Attorney Docket No. 8330-000744-WO-PCCLAIMSWhat is claimed is:1 . A method for converting post-consumer recycled (PCR) flakes of polyethylene terephthalate (PET) to pellets as part of a container recycling procedure, the method comprising: adding an antioxidant to a flake-to-pellet conversion process at a concentration of 0.05 wt.% to 0.15 wt.%; coating the PCR flakes with the antioxidant; and converting the PCR flakes to the pellets in an extruder after coating the PCR flakes with the antioxidant to reduce yellowing of the pellets during the conversion.

2. The method of claim 1 , wherein the antioxidant is a triphenyl phosphite based compound.

3. The method of claim 2, wherein the triphenyl phosphite based compound is blended with phosphoric acid.

4. The method of claim 2, wherein the triphenyl phosphite based compound is a blend of at least 2 different forms of triphenyl phosphite.

5. The method of claim 2, wherein the triphenyl phosphite based compound is blended with hindered phenols or hindered amines.

6. The method of claim 2, wherein the triphenyl phosphite based compound is blended with diphosphites or monophosphites.

7. The method of claim 1 , wherein the antioxidant is added to the flakes to pellet conversion process at a reactor, decontamination tank, or flake to pellet extruder.

8. The method of claim 1 , wherein the antioxidant is added prior to a melt filtration step.Attorney Docket No. 8330-000744-WO-PC9. The method of claim 1 wherein the antioxidant is heated to between 35 C and 90 C before being added to the flake-to-pellet conversion process.

10. The method of claim 1 wherein the antioxidant has a viscosity of between 40 cP and 1000 cP before being added to the flake-to-pellet conversion process.11 . The method of claim 1 , wherein a concentration ratio of the antioxidant is configured to prevent reduction of antimony trioxide to elemental antimony.

12. The method of claim 7, wherein the reactor is an agitated vessel under temperature and vacuum.

13. The method of claim 12, wherein the reactor is configured to pre-crystallize the PCR flake before the extruder.

14. The method of claim 12, wherein the reactor is configured to raise an intrinsic viscosity of the PCR flake before the extruder.

15. The method of claim 7, wherein the decontamination tank is designed to remove volatile substances.

16. The method of claim 7, wherein the extruder is configured to form the pellets.

17. The method of claim 1 , wherein the antioxidant reduces yellowing of the pellets during subsequent solid state polymerization.

18. The method of claim 1 , wherein the antioxidant prevents yellowing of the pellets during subsequent drying of the pellets.

19. A method for converting post-consumer recycled (PCR) flakes of polyethylene terephthalate (PET) to a molded part, the method comprising: adding an antioxidant to a flake-to-molded part conversion process at a concentration of 0.05 wt.% to 0.15 wt.%; coating the PCR flakes with the antioxidant; andAttorney Docket No. 8330-000744-WO-PC converting the PCR flakes to a molded part after coating the PCR flakes with the antioxidant to reduce yellowing of the molded part.

20. The method of claim 19, wherein the molded part is injection molded or compression molded.

21. The method of claim 19, wherein the molded part is a preform configured for blow molding into a final container.

22. The method of claim 19, wherein the antioxidant is a triphenyl phosphite based compound.

23. The method of claim 22, wherein the triphenyl phosphite based compound is blended with phosphoric acid.

24. The method of claim 22, wherein the triphenyl phosphite based compound is a blend of at least two different forms of triphenyl phosphite.

25. The method of claim 22, wherein the triphenyl phosphite based compound is blended with hindered phenols or hindered amines.

26. The method of claim 22, wherein the triphenyl phosphite based compound is blended with diphosphites or monophosphites.

27. The method of claim 19, wherein the antioxidant is added to the flakes to molded part conversion process at a reactor, decontamination tank, or extruder.

28. The method of claim 19, wherein the antioxidant is added prior to a melt filtration step.

29. The method of claim 19, wherein the antioxidant is heated to between 35 C and 90 C before being added to the flake-to-molded part conversion process.Attorney Docket No. 8330-000744-WO-PC30. The method of claim 19, wherein the antioxidant has a viscosity of between 40 cP and 1000 cP before being added to a flake-to-molded part conversion process.

31. The method of claim 19, wherein a concentration ratio of the antioxidant is configured to prevent reduction of antimony trioxide to elemental antimony.

32. The method of claim 27, wherein the reactor is an agitated vessel under temperature and vacuum.

33. The method of claim 32, wherein the reactor is configured to pre-crystallize the PCR flake before the extruder.

34. The method of claim 32, wherein the reactor is configured to raise an intrinsic viscosity of the PCR flake before the extruder.

35. The method of claim 27, wherein the decontamination tank is designed to remove volatile substances.

36. A method for converting post-consumer recycled (PCR) flakes of polyethylene terephthalate (PET) to pellets as part of a container recycling procedure, the method comprising: adding an antioxidant to a reactor at a concentration of 0.05 wt.% to 0.15 wt.%; coating the PCR flakes with the antioxidant; and converting the PCR flakes to the pellets in an extruder after coating the PCR flakes with the antioxidant to reduce yellowing of the pellets during the conversion, wherein the antioxidant is a triphenyl phosphite based compound.

37. The method of claim 36, wherein the triphenyl phosphite based compound is blended with phosphoric acid.

38. The method of claim 36, wherein the triphenyl phosphite based compound is a blend of at least two different forms of triphenyl phosphite.Attorney Docket No. 8330-000744-WO-PC39. The method of claim 36, wherein the triphenyl phosphite based compound is blended with at least one of hindered phenols, hindered amines, diphosphites, monophosphites.

40. The method of claim 36, wherein the antioxidant is heated to between 35°C and 90°C to raise viscosity to between 40 cP and 1000 cP before being added to the reactor.

41. The method of claim 36, wherein a concentration ratio of the antioxidant is configured to prevent reduction of antimony trioxide to elemental antimony.

42. The method of claim 36, wherein the reactor is an agitated vessel under temperature and vacuum configured to pre-crystallize the PCR flake and raise an intrinsic viscosity of the PCR flake before the extruder.

43. The method of claim 36, wherein the extruder is configured to form the pellets.

44. The method of claim 36, wherein the antioxidant reduces yellowing of the pellets during subsequent solid state polymerization, drying of the pellets, and molding of a final part.

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