Method for manufacturing oligomeric polyethylene terephthalate (PET) substrates

Abstract

The present invention provides a method for producing an oligomeric polyethylene terephthalate (PET) substrate for use in the manufacture of recycled PET (rPET), the method comprising adding recycled dihydroxy terephthalate (rBHET) or a higher molecular weight oligomer derived from rBHET and water to a reaction zone, and causing the rBHET and water in the reaction zone to react to produce an oligomeric PET substrate represented by formula (I), wherein R1 is a carboxyl end group or a hydroxyl end group, R2 is a carboxyl end group or a hydroxyl end group, and n is the degree of polymerization (Dp).

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 035,186, filed June 5, 2020, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to methods for manufacturing oligomeric PET substrates from recycled polyethylene dihydroxyterephthalate (rBHET) or virgin BHET derived from virgin dimethyl terephthalate (vBHET), manufacturing oligomeric PET for use in the manufacture of recycled PET, and manufacturing PET polymers made from 0-100% recycled PET comprising oligomeric PET substrates, wherein 0% recycled PET represents PET polymers derived from vDMT. Background Technology

[0004] PET (polyethylene terephthalate) is a synthetic material first produced in the mid-1940s. PET possesses desirable properties and processing capabilities, and is therefore now widely used globally for packaging applications in the food and beverage industry, industrial products, and the textile industry.

[0005] Typically, PET has petrochemical origins. Purified terephthalic acid is first produced in a purified terephthalic acid manufacturing facility via aerobic catalytic oxidation of p-xylene in an acetic acid medium. This purified terephthalic acid (PTA) then reacts with ethylene glycol to produce PTA-based oligomers (and water), which then undergo condensation polymerization to form PET polymers. An alternative route for preparing PET polymers is via the polymerization of dihydroxy terephthalate (BHET) monomers; however, this route is less economically advantageous. BHET monomers are formed by the reaction of dimethyl terephthalate (DMT) (a diester formed from terephthalic acid and methanol) with ethylene glycol, followed by the self-polymerization of the BHET monomers to form longer PET chains.

[0006] In the PET manufacturing process, there are three main stages in the molten phase to prepare the PET polymer: (1) esterification, (2) prepolymerization, and (3) polymerization. When preparing PET resin, the PET polymer enters an additional solid-state polymerization (SSP) stage for further modifications, which involves increasing the molecular weight of the polymer. In the initial esterification stage, PTA (or DMT) and ethylene glycol are mixed and fed into the esterification unit, where esterification, whether catalytic or non-catalytic, is carried out at atmospheric pressure and a temperature range of 270°C to 295°C. Water (or methanol in the case of DMT) and excess ethylene glycol produced by the esterification reaction are evaporated. Additives (including catalysts and colorants) are typically added to the process between the esterification stage and the subsequent prepolymerization stage. In the prepolymerization stage, the product from the esterification unit is sent to the prepolymerization unit and reacted with additional ethylene glycol at a temperature range of 270°C to 295°C and a significantly reduced pressure to allow for an increase in the degree of polymerization of the oligomers. During the polymerization stage, the product from the prepolymerization stage undergoes further low-pressure and temperature-range (270°C to 295°C) treatment in horizontal polymerization units to further allow the degree of polymerization to increase to approximately 80-120 repeating units. In embodiments, this is referred to as a trimmer or trimmer container. When preparing PET resin, a fourth solid-state polymerization (SSP) stage involving a crystallization step is typically required, where amorphous granules generated during the molten phase are converted into crystalline granules, which are then further processed according to the final PET product, which can be diverse, such as containers / bottles for liquids and food or industrial products and resins.

[0007] The aim is to reduce the amount of plastic sent to landfills by recycling post-use PET-containing waste. One known recycling method utilizes post-use PET-containing waste to produce post-use recycled (PCR) flakes. These PCR flakes can then be glycolytically digested to convert them into recycled polyethylene terephthalate (rBHET). This rBHET can then be used in PET manufacturing to produce recycled PET (rPET; so named because the oligomers it is based on are derived from post-use PET or PCR, rather than PTA or DMT). This avoids the need to use more petrochemically derived PTA combined with ethylene glycol to produce PTA-based oligomers in the virgin (vPTA) process or to produce virgin (vBHET) in the virgin (vDMT) process. Furthermore, rPET has a lower carbon footprint than vPET because it requires less petrochemical products compared to new PET (called virgin PET (vPET)). Therefore, rPET is attractive based on its 'green' credentials, which in themselves may bring economic benefits in certain jurisdictions.

[0008] However, rPET made from rBHET tends to be less reactive in both the melt phase process and the solid-phase polymerization stage. If rBHET is used in PET manufacturing, the amount of rPET produced is approximately 20% lower than that produced using PTA-based oligomers (i.e., short-chain PET oligomers made by esterification of purified terephthalic acid with ethylene glycol). Furthermore, rPET made from rBHET tends to be darker (lower L*) and more yellow, primarily due to impurities in the rPET polymer. Therefore, currently, the rPET manufacturing process using rBHET (a glycolysis product of PET waste) is neither attractive nor competitive compared to vPET processes using PTA-based oligomers or vBHET.

[0009] Therefore, there is a need to produce oligomeric PET substrates that have increased reactivity and thus the ability to increase polymerization to form rPET in order to compete with the process for preparing vPET. Summary of the Invention

[0010] This disclosure particularly provides a method for producing an oligomeric PET substrate for use in the rPET manufacturing process, the method comprising reacting polyethylene dihydroxyterephthalate (rBHET) from a recycled source or from vDMT, or a higher molecular weight oligomer derived from a similar BHET source, with water to produce an oligomeric PET substrate represented by Formula I:

[0011]

[0012] Where R1 is a carboxyl end group (COOH) or a hydroxyl end group (OH), R2 is a carboxyl end group or a hydroxyl end group, and n is the degree of polymerization.

[0013] In some embodiments, when the method includes reacting rBHET with water, n is 1 to 10, preferably 3 to 7. In some embodiments, when the method includes reacting a higher molecular weight oligomer derived from rBHET with water, n is 20 to 50, preferably 25 to 35. In some embodiments, when the method includes reacting rBHET with water, the oligomeric PET substrate has a CEG (acid-terminal molars / material te number) of 300 to 1500, preferably 500 to 1200, more preferably 700 to 1100. In some embodiments, when the method includes reacting a higher molecular weight oligomer derived from rBHET with water, the oligomeric PET substrate has a CEG (acid-terminal molars / material te number) of 40 to 200, preferably 150 to 190. In some embodiments, the oligomeric PET substrate has a hydroxyl-to-carboxyl-terminal ratio in the range of 1.66 to 6.66, preferably in the range of 2.22 to 4.0.

[0014] In some embodiments, when the method includes reacting rBHET with water, water is added to the reaction zone in the range of 2% to 20% by weight, preferably 5% to 10% by weight, relative to the PET polymer. In some embodiments, when the method includes reacting a higher molecular weight oligomer derived from rBHET with water, water is added to the reaction zone in the range of 0.1% to 2% by weight, preferably 0.1% to 0.5% by weight, relative to the PET polymer. In some embodiments, rBHET reacts with water at a temperature between 120°C and 300°C, preferably 150°C to 270°C. In some embodiments, the higher molecular weight oligomer derived from rBHET reacts with water at a temperature between 270°C and 300°C, preferably 285°C to 295°C. In some embodiments, the method includes a residence time in the reaction zone between 30 minutes and 120 minutes, preferably 40 minutes to 50 minutes. In some embodiments, rBHET reacts with water at a pressure between 3 barg and 30 barg. In some implementations, higher molecular weight oligomers derived from rBHET react with water at a pressure of 10 barg to 50 barg.

[0015] In some embodiments, rBHET or higher molecular weight oligomers derived from rBHET react with water using at least one exogenously added catalyst selected from antimony-containing catalysts, titanium-containing catalysts, zinc-containing catalysts, acetate-containing catalysts, manganese-containing catalysts, germanium-containing catalysts, aluminum-containing catalysts, and tin-containing catalysts. In some embodiments, the catalyst includes at least one selected from antimony trioxide, antimony glycolate, antimony triacetate, titanium alkoxide, zinc acetate, and manganese acetate. In some embodiments, the oligomeric PET substrate is fed directly or indirectly into the rPET manufacturing process.

[0016] This disclosure also provides PET substrates produced by the methods described herein. In one embodiment, the oligomeric PET substrate has a structure according to Formula I:

[0017] (I)

[0018] Wherein R1 is a carboxyl-terminal or hydroxyl-terminal group, R2 is a carboxyl-terminal or hydroxyl-terminal group, and n is the degree of polymerization, and wherein the oligomeric PET substrate further comprises any two of the following characteristics: i) a degree of polymerization where n is 1-10 or 20-50; ii) a carboxylic acid end group concentration (CEG) (moles of acid ends per metric ton (te) of material) between 300 and 1500 or 40 and 200; and iii) a hydroxyl-terminal to carboxyl-terminal ratio in the range of 1.66 to 6.66. In some embodiments, the oligomeric PET substrate is used in the range of 0-100% rPET to synthesize the polymer.

[0019] This disclosure also provides PET polymers made from 0-100% rPET, produced from oligomeric PET substrates as represented by Formula I. Attached Figure Description

[0020] Figure 1 Based on the flowchart of the process disclosed in this article, it shows where rBHET and water can be added to the rBHET process.

[0021] Figure 2 The flowchart, based on the process disclosed herein, shows the location in the process where water can be added later into the oligomer leaving the prepolymer container (UFPP).

[0022] Figure 3 This is an alternative flow diagram based on the process disclosed herein, showing the location in the process where water can be added later into the oligomer leaving the prepolymer container (UFPP).

[0023] Figure 4 It is a typical laboratory device designed to demonstrate the hydrolysis of BHET in the DMT transesterification reaction.

[0024] Figure 5 The flowchart diagram of the process disclosed in this article shows the location where water can be added to the BHET made by the DMT process.

[0025] Figure 6 This is an alternative flow diagram based on the process disclosed herein, showing the location where water can be added to the BHET produced by the DMT process.

[0026] Figure 7 This is a graph showing the trimmer pressure as a function of the simulated PET production process described in Comparative Example 5, based on the change in the oligomer OH:COOH ratio.

[0027] Figure 8 This is a graph showing the plant rate based on the change in the oligomer OH:COOH ratio in a simulated PET production process described in Comparative Example 5.

[0028] Figure 9 This is a graph showing the trimmer pressure versus %H2O for various aspects of the present disclosure, illustrating a simulated PET production process according to Example 7.

[0029] Figure 10 This is a graph showing the trimmer pressure versus oligomer OH:COOH during a simulated PET production process as described in Example 7. Detailed Implementation

[0030] This document discloses methods for producing oligomeric PET substrates from rBHET or higher molecular weight oligomers derived from BHET, producing oligomeric PET substrates for use in the manufacture of rPET, and producing PET polymers made from 0-100% recycled PET, the PET polymers comprising the oligomeric PET substrates. In the methods disclosed herein, rBHET or higher molecular weight oligomers derived from BHET and water are added to a reaction zone and reacted in the reaction zone under conditions conducive to the efficient production of oligomeric PET substrates.

[0031] The methods disclosed herein address a problem recognized in the art where rBHET exhibits lower reactivity compared to vBHET in the manufacture of PET oligomers, and therefore, PET oligomers prepared from rBHET have lower yields compared to those prepared from vBHET or PTA. Specifically, this disclosure provides a method for improving rPET manufacturing efficiency by reacting BHET or higher molecular weight oligomers derived from BHET with water at specific points in the manufacturing process. These methods enhance practitioners' ability to prepare PET from recycled starting materials in an economically competitive manner compared to methods used for the preparation of virgin PET.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although similar or equivalent methods and materials may be used to practice this invention, suitable methods and materials are described below. In case of any conflict, this specification (including definitions) shall prevail.

[0033] Furthermore, the materials, methods, and examples are illustrative only and are not intended to be limiting. Details of one or more embodiments of the invention are set forth in the following drawings and description. Other features, objects, and advantages of the invention will become apparent from the description, drawings, and claims. In accordance with standard practice in patent law, the word "comprising" in the claims may be replaced with "consistently consisting of" or "comprises of".

[0034] Unless otherwise specified or obvious from the context, the term "about" as used herein shall be understood to mean within the normal tolerance range in the field, such as within 2 standard deviations of the mean. "About" can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the specified value. Unless the context otherwise requires, all numerical values ​​provided herein are modified by the term "about".

[0035] The term "PET" or "PET polymer" refers to polyethylene terephthalate.

[0036] The term "PTA" refers to purified terephthalic acid.

[0037] The term "vPTA" refers to PTA synthesized via aerobic catalytic oxidation of p-xylene in an acetic acid medium.

[0038] As used herein, "PTA-based oligomers" refers to short-chain PET oligomers synthesized through an esterification process involving purified terephthalic acid and ethylene glycol. Purified terephthalic acid (PTA) reacts with ethylene glycol to produce PTA-based oligomers (and water), which then undergo condensation to form PET polymers. When PTA reacts with ethylene glycol, short-chain PTA-based oligomers are formed, characterized by Dp (degree of polymerization or number of repeating units) and CEG (or carboxylic acid end-group concentration). The degree of polymerization (Dp) is calculated based on the number-average molecular weight Mn using the following formula: Dp = (Mn - 62) / 192, where Mn is calculated by rearranging IV (intrinsic viscosity) with the following correlation: IV = 1.7e-4(Mn). 0.83 The intrinsic viscosity (IV) of polyester can be measured using a melt viscosity technique equivalent to ASTM D4603-96. Typically, for PTA-based oligomers formed by reacting PTA with ethylene glycol, the degree of polymerization is usually between 3 and 7, and the CEG is typically between 500 and 1200 (molar number of acid ends / te number of materials). The ratio of hydroxyl-terminated groups (HEG) to carboxyl-terminated groups (CEG) is determined by the rearrangement of the CEG measurement and the following Mn calculation: Mn = 2e6 / (CEG + HEG).

[0039] As used in this article, "PET manufacturing process" refers to the facility that produces PET. Such facilities may be integrated with the PTA manufacturing process or may be completely independent.

[0040] As used herein, “post-use PET-containing waste” refers to any waste stream containing at least 10% PET waste. Therefore, post-use PET-containing waste can contain 10% to 100% PET. Post-use PET-containing waste can be municipal waste that itself contains at least 10% PET waste, such as PET plastic bottles or PET food packaging, or any post-use recycled PET-containing waste, such as waste polyester fiber. Waste polyester fiber sources include items such as clothing items (shirts, trousers, dresses, coats, etc.), bedding, comforter linings, or towels. “Post-use PET-containing waste” can also include post-use recycled (PCR) flakes, which are waste PET plastic bottles that have been mechanically shredded into smaller pieces for use in the recycling process.

[0041] As used herein, “vPET” refers to virgin PET, which is synthesized through an esterification process involving purified terephthalic acid and ethylene glycol. Purified terephthalic acid (PTA) reacts with ethylene glycol to produce PTA-based oligomers (and water), which then undergo polycondensation to form the PET polymer. Alternatively, vPET can be formed by reacting dimethyl terephthalate (DMT), a diester formed from terephthalic acid and methanol, with ethylene glycol. BHET monomers are formed by reacting dimethyl terephthalate (DMT), a diester formed from terephthalic acid and methanol, with ethylene glycol, followed by self-polymerization of the BHET monomers to form longer PET chains.

[0042] As used herein, “rPET” refers to recycled PET, which is PET manufactured wholly or at least partially from oligomers derived from post-use PET-containing waste. rPET can be synthesized from 100% oligomers derived from post-use PET-containing waste. Alternatively, rPET can be synthesized from a combination of oligomers comprising those derived from post-use PET-containing waste, and those derived from vBHET or PTA-based oligomers used to prepare vPET. In one non-limiting embodiment, rPET comprises at least 5% oligomeric PET substrate derived from post-use PET-containing waste. In another non-limiting embodiment, rPET comprises at least 50% oligomeric PET substrate derived from post-use PET-containing waste. In yet another non-limiting embodiment, rPET comprises at least 80% oligomeric PET substrate derived from post-use PET-containing waste.

[0043] As used herein, “rPET manufacturing process” refers to manufacturing processes and facilities specifically designed and constructed to synthesize recycled PET (rPET), i.e., PET made from substrates including, in addition to virgin substrates (i.e., vBHET or PTA-based oligomers), those derived from any post-use PET waste, as well as manufacturing processes and facilities constructed to synthesize vPET, but which have been modified or adapted to allow the production of rPET. The changes required to vPET facilities for rPET production are typically not structurally significant, but rather involve substantial process modifications.

[0044] The term "BHET" refers to the monomer of dihydroxyethylene terephthalate (C... 12 H 14 O6), encompassing all structural isomers, is characterized by the absence of a carboxyl terminus, i.e., a carboxylic acid terminus concentration (CEG) of zero. The chemical structure of the para-isomer of the BHET monomer is shown below:

[0045]

[0046] To produce PET, BHET reacts with itself in a polycondensation reaction to prepare longer chains, thereby forming polyethylene terephthalate (PET) and releasing ethylene glycol in the process. BHET, the BHET monomer, is typically formed by the reaction of dimethyl terephthalate (DMT) with ethylene glycol, but it is also a minor component in oligomers made from PTA and ethylene glycol, contributing to the oligomer's molecular weight distribution. When PTA reacts with ethylene glycol, short-chain PTA-based oligomers are formed, characterized by Dp (degree of polymerization or number of repeating units) and CEG (or carboxylic acid end group concentration). Typically, for PTA-based oligomers formed by reacting PTA with ethylene glycol, the degree of polymerization is usually between 3 and 7 or between 25 and 35, and the CEG is usually between 500 and 1200 or between 150 and 190 (molar number of acid ends / te number of materials).

[0047] The term "vBHET" refers to native BHET, which is a BHET monomer formed by the reaction of dimethyl terephthalate (DMT) with ethylene glycol.

[0048] The term "rBHET" refers to recycled BHET, which is a BHET molecule produced by glycolysis of PET. Used PET-containing waste, such as PET plastic bottles, is mechanically broken down to produce used recycled (PCR) wafers. These PCR wafers are then glycolysis to convert them into rBHET.

[0049] As used herein, “oligomeric PET substrate” refers to a molecule according to Formula I:

[0050] Formula I

[0051] Either end of Formula I can be a carboxyl terminus (COOH) or a hydroxyl terminus (OH). Therefore, R1 or R2 can be either a carboxyl terminus or a hydroxyl terminus. The optimal hydroxyl to carboxyl terminus (HEG:CEG) ratio in oligomeric PET substrates is typically between 1.66 and 6.66. Formula I polymerizes with itself in an esterification reaction, where the carboxyl terminus reacts with the hydroxyl terminus to form an ester bond, releasing water. “n” represents the degree of polymerization (Dp) or the number of repeating units of Formula I present in the oligomeric PET substrate, and can be, for example, between 3 and 7 or between 25 and 35. In addition to being characterized by the degree of polymerization (Dp), oligomeric PET substrates are also characterized by their carboxylic acid terminus concentration (referred to herein as CEG). CEG (unit: moles of acid terminus / material te number) can be, for example, between 500 and 1200 or between 150 and 190.

[0052] This disclosure provides a method for producing oligomeric PET substrates. Methods for producing rPET typically employ a process of glycolysis of PET (or a waste source containing PET) using, for example, ethylene glycol to produce polyethylene dihydroxyterephthalate (rBHET). This method of producing rPET uses rBHET and polymerizes it to produce rPET. However, this rBHET exhibits lower reactivity compared to PTA-based oligomers formed through the esterification of purified terephthalic acid with ethylene glycol. Therefore, when used to prepare rPET, for a similar process, rBHET produces approximately 20% less rPET compared to vPET produced using PTA-based oligomers (formed through the esterification of purified terephthalic acid with ethylene glycol).

[0053] In this disclosure, it was unexpectedly discovered that rBHET or higher molecular weight oligomers derived from rBHET can be hydrolyzed to produce oligomeric PET substrates with increased reactivity compared to unmodified rBHET. Specifically, water is added to and reacted with rBHET or higher molecular weight oligomers derived from rBHET to produce oligomeric PET substrates. These oligomeric PET substrates exhibit increased reactivity compared to the unmodified oligomers, i.e., rBHET. Therefore, aspects of this disclosure relate to a method for producing oligomeric PET substrates by reacting rBHET or higher molecular weight oligomers derived from rBHET with water.

[0054] Oligomeric PET substrates are represented by Formula I:

[0055]

[0056] In embodiments, either end of Formula I can be a carboxyl terminal group or a hydroxyl terminal group. Therefore, R1 or R2 can be a carboxyl terminal group or a hydroxyl terminal group. As described herein, the optimal ratio of hydroxyl terminal to carboxyl terminal group in Formula I is typically between 1.66 and 6.66, preferably between 2.22 and 4.0. The degree of polymerization (Dp) or the number of repeating units present in the oligomeric PET substrate can vary depending on whether the PET substrate is prepared by reacting rBHET or a higher molecular weight oligomer derived from rBHET with water. When rBHET reacts with water, the degree of polymerization (Dp) can be between 1 and 10, more typically between 3 and 7, and preferably 6. When a higher molecular weight oligomer derived from rBHET reacts with water, the degree of polymerization (Dp) can be between 20 and 50, and preferably between 25 and 35. In addition to being characterized by the degree of polymerization (Dp) and the hydroxyl to carboxyl end group ratio, oligomeric PET substrates are also characterized by their carboxylic acid end group concentration (referred to herein as CEG). CEG (unit: moles of acid ends / material te number) can vary depending on whether the PET substrate is prepared by reacting rBHET or higher molecular weight oligomers derived from rBHET with water. When rBHET reacts with water, CEG can typically be between 300 and 1500, and preferably between 500 and 1200, or even between 700 and 1100. When higher molecular weight rBHET oligomers react with water, CEG can be from 40 to 200, and preferably from 150 to 190.

[0057] In one non-limiting embodiment, the oligomeric PET substrate includes a hydroxyl end-to-carboxyl end-to-hydroxyl ratio between 1.66 and 6.66, a Dp between 4 and 7, and a CEG between 700 and 1100 molars of acid ends / material te number.

[0058] In another non-limiting embodiment, the oligomeric PET substrate includes a hydroxyl end-to-carboxyl end-to-hydroxyl ratio between 1.66 and 6.66, a Dp between 25 and 35, and a CEG between 150 and 190 molars of acid ends / material te number.

[0059] The benefits associated with the optimized end-group ratio are found to stem from the balance between the reaction rates of esterification and polycondensation, the relative partial pressures of the condensation products (i.e., water and ethylene glycol), and the balance of the chemical equilibrium constants between esterification and polycondensation. This balance yields a natural optimum in the range of 2.22 to 4.0, as previously described.

[0060] In one non-limiting embodiment, water is added to rBHET in the range of 2% to 20% by weight, and preferably in the range of 5% to 10% by weight, relative to the final PET polymer.

[0061] In another non-limiting embodiment, water is added to the higher molecular weight rBHET oligomer in the range of 0.1% to 2% by weight, and preferably 0.1% to 0.5% by weight, relative to the final PET polymer.

[0062] In one non-limiting embodiment, rBHET reacts with water at a temperature between 120°C and 300°C, and preferably between 150°C and 270°C.

[0063] In another non-limiting embodiment, higher molecular weight oligomers derived from rBHET react with water at a temperature between 270°C and 300°C, and preferably between 285°C and 295°C.

[0064] In one non-limiting embodiment, rBHET is melted before being added to the reaction zone. Water and rBHET can be injected into the reaction zone separately or combined upstream of the reaction zone. The reaction zone is located before the additive is injected into the process. The residence time in the reaction zone can be from 30 minutes to 120 minutes, and preferably from 40 minutes to 50 minutes.

[0065] In one non-limiting embodiment, rBHET reacts with water at a pressure of 3 barg to 30 barg. In another non-limiting example, higher molecular weight oligomers derived from rBHET react with water at a pressure of 10 barg to 50 barg. This pressure is typically generated in a reaction zone, such as a linear reactor. The linear reactor provides a residence time at a given temperature to complete the reaction of rBHET or higher molecular weight oligomers derived from rBHET with water. In this example, it refers to the oligomer retention time.

[0066] In one non-limiting embodiment, the added water is added to the reaction zone after the prepolymerization reactor.

[0067] In one non-limiting embodiment, the added water is added to the reaction zone after the intermediate polymerization reactor.

[0068] In one non-limiting embodiment, water is added to the bottom of a continuous DMT transesterification reactor having a titanium alkoxide catalyst.

[0069] The reaction can be catalytic or non-catalytic, depending on the composition of the PCR wafers used to prepare rBHET. In a non-limiting embodiment, rBHET or higher molecular weight rBHET oligomers and water react in the presence of an exogenously added catalyst. Due to its manufacturing process, post-PET waste or PCR wafers may contain latent catalysts. Therefore, in some embodiments, rBHET derived from PCR wafers may have sufficient endogenous catalyst. However, additional exogenous catalysts may be added if desired. Non-limiting examples of catalysts that can be added to the reaction include catalysts containing antimony, titanium, zinc, manganese, germanium, aluminum, and tin. These can be selected from antimony-containing catalysts, titanium-containing catalysts, zinc-containing catalysts, acetate-containing catalysts, manganese-containing catalysts, germanium-containing catalysts, aluminum-containing catalysts, or tin-containing catalysts. These can be, for example, antimony trioxide, antimony glycolate, antimony triacetate, titanium alkoxide, zinc acetate, or manganese acetate. Such catalysts are added to the reaction zone, which is generally referred to as the esterification unit. The titanium-containing catalyst is typically added at 2-100 ppm, and preferably about 10 ppm, relative to the final PET polymer. All other catalysts (except titanium-containing catalysts) are typically added at 40 ppm to 300 ppm, preferably about 240 ppm.

[0070] In some non-limiting embodiments, the oligomeric PET substrate is used in the rPET manufacturing process, a process previously designed for the synthesis of vPET but modified for the preparation of rPET. In another alternative non-limiting embodiment, the oligomeric PET substrate is used in the rPET manufacturing process, which is specifically designed from the outset for the preparation of rPET.

[0071] This disclosure also relates to oligomeric PET substrates produced by or obtainable through the methods described herein. In one non-limiting embodiment, this disclosure relates to oligomeric PET substrates produced using rBHET derived from PCR wafers. In another non-limiting embodiment, this disclosure relates to oligomeric PET substrates produced using vBHET derived from vDMT (dimethyl terephthalate). In yet another non-limiting embodiment, this disclosure relates to oligomeric PET substrates produced using a combination of rBHET derived from PCR wafers and vBHET derived from vDMT.

[0072] In some implementations, the oligomeric PET substrate has a structure according to Formula I:

[0073] (I)

[0074] Where R1 is a carboxyl or hydroxyl end group, R2 is a carboxyl or hydroxyl end group, and n is the degree of polymerization, and the oligomeric PET substrate is represented by two or more of the following characteristics:

[0075] i)n is the degree of aggregation from 1 to 10;

[0076] ii) CEG (molar number of acid ends / material te number) of 300 to 1500; and

[0077] iii) The ratio of hydroxyl end group to carboxyl end group in the range of 1.66 to 6.66.

[0078] In some embodiments, the oligomeric PET substrate is characterized by: (i) a degree of polymerization of n from 1 to 10 and (ii) a CEG (molar number of acid ends / te number of materials) of 300 to 1500. In some embodiments, the oligomeric PET substrate is characterized by: (i) a degree of polymerization of n from 3 to 7 and (ii) a CEG (molar number of acid ends / te number of materials) of 700 to 1100.

[0079] In some implementations, the oligomeric PET substrate has a structure according to Formula I:

[0080] (I)

[0081] Where R1 is a carboxyl or hydroxyl end group, R2 is a carboxyl or hydroxyl end group, and n is the degree of polymerization, and the oligomeric PET substrate is represented by two or more of the following characteristics:

[0082] i)n is the degree of polymerization, which is between 20 and 50;

[0083] ii) CEG (molar number of acid ends / material te number) of 40 to 200; and

[0084] iii) The ratio of hydroxyl end group to carboxyl end group in the range of 1.66 to 6.66.

[0085] In some embodiments, the oligomeric PET substrate is characterized by: (i) a degree of polymerization of n of 20 to 50 and (ii) a CEG (molar number of acid ends / te number of materials) of 40 to 200. In some embodiments, the oligomeric PET substrate is characterized by: (i) a degree of polymerization of n of 25 to 35 and (ii) a CEG (molar number of acid ends / te number of materials) of 150 to 190.

[0086] Another aspect of this disclosure relates to PET polymers manufactured using oligomeric PET substrates produced by or obtainable through the methods described herein during polymerization. The PET polymers can range from 0-100% rPET. Therefore, the PET polymers can be entirely virgin PET (produced from 100% vBHET, which is itself derived from vDMT), entirely recycled PET (produced from 100% rBHET), or a mixture thereof comprising vPET and rPET.

[0087] refer to Figure 1 The diagram illustrates a system according to one aspect of this disclosure for producing oligomeric PET substrates from rBHET powder stored in a hopper 110. In the illustrated system, rBHET powder is fed from the hopper 110 into a melting vessel 120, where the rBHET powder is melted and stirred. The molten rBHET is then mixed with water, and the mixture is supplied to a reaction zone 130, also known as a linear reactor 130. The reaction zone 130 is maintained under conditions that allow the rBHET to react with water to produce oligomeric PET substrates. The effluent from the reaction zone 130 is then first fed into a prepolymerization vessel 140, and then into a trimmer vessel 150 to increase the degree of polymerization of the monomers.

[0088] refer to Figure 2 The diagram illustrates a system according to one aspect of this disclosure for producing oligomeric PET substrates from rBHET powder stored in a hopper 210. In the illustrated system, rBHET powder is fed from hopper 210 into a melting vessel 220, where the rBHET powder is melted and stirred. The mixture is pumped to a prepolymerization vessel (UFPP) 240. Water is then added to the effluent from the UFPP 240 and conveyed to a reaction zone 260 (also referred to as a linear reactor 260). The reaction zone 260 is maintained under conditions that allow rBHET to catalytically react with water to produce oligomeric PET substrates. The effluent from the reaction zone 260 is then fed to a trimmer vessel 250 to increase the degree of polymerization of the monomers.

[0089] refer to Figure 3The diagram illustrates a system according to one aspect of this disclosure for producing oligomeric PET substrates from rBHET powder stored in a hopper 310. In the illustrated system, rBHET powder is fed from the hopper 310 into a melting vessel 320, where the rBHET powder is melted and stirred. The mixture is pumped to a prepolymerization vessel (UFPP) 340. Water is then added to the effluent from the prepolymerization vessel (UFPP) 340 and conveyed to a reaction zone 360 ​​(also referred to as a linear reactor 360). The reaction zone 360 ​​is maintained under conditions that allow rBHET to catalytically react with water to produce oligomeric PET substrates. The effluent from the reaction zone 360 ​​is then fed to an intermediate polymerizer (IP) 370 and then to a trimmer vessel 350 to increase the degree of polymerization of the monomers.

[0090] refer to Figure 4 It shows typical laboratory equipment designed to demonstrate the hydrolysis of BHET in the DMT transesterification reaction.

[0091] refer to Figure 5 This diagram illustrates a system according to one aspect of the present disclosure for producing oligomeric PET substrates from BHET derived from DMT. DMT and ethylene glycol, along with a catalyst, are added to an ester exchange column 510. Water is added to the effluent (BHET) from the ester exchange column 510 and fed to a reaction zone 520 (also referred to as a linear reactor 520). The reaction zone 520 is maintained under conditions that allow the BHET to react catalytically with water to produce oligomeric PET substrates. The effluent from the reaction zone 520 is then fed to a prepolymerization vessel (UFPP) 530, and subsequently to a trimmer vessel 540 to increase the degree of polymerization of the monomers.

[0092] refer to Figure 6 This diagram illustrates a system according to one aspect of the present disclosure for producing oligomeric PET substrates from BHET derived from DMT. DMT, ethylene glycol, catalyst, and water are added to an ester exchange column 610. The effluent (BHET) from the ester exchange column 610 is fed to a reaction zone 620 (also referred to as a linear reactor 620). The reaction zone 620 is maintained under conditions that allow the BHET to react catalytically with water to produce oligomeric PET substrates. The effluent from the reaction zone 620 is then fed into a prepolymerization vessel (UFPP) 630, and subsequently into a trimmer vessel 640 to increase the degree of polymerization of the monomers.

[0093] Example

[0094] The aspects of this disclosure are demonstrated through process modeling examples of continuous polymerization (CP) operations, which show the predictive effect of water on dihydroxyethylene terephthalate (BHET).

[0095] In addition, the method disclosed herein has been demonstrated on a 20L (liter) semi-factory scale batch reactor using the following experimental scheme.

[0096] Typically, under ambient conditions, 8 kg of PTA-based oligomer or 10.58 kg of BHET is charged into the reactor along with sufficient antimony trioxide catalyst to obtain 280 ppm Sb (as elemental), cobalt acetate tetrahydrate to obtain 40 ppm Co (as elemental), and triethyl phosphate (TEP) to obtain 20 ppm P (as elemental). Other additives are added as described in the detailed example below. The reactor is then separated under a nitrogen layer and heat is applied. The reactor temperature setpoint is then set to 260°C, and the reactor pressure naturally increases due to the vapor pressure of water and ethylene glycol as the temperature of the contents increases. During this time and throughout the initial period, the contents are stirred at 50 rpm–1200 rpm. Once 260°C has been reached, the reactor is held for a predetermined time, typically 30 to 60 minutes, then the pressure is released to atmospheric pressure, and a sample of the oligomer liquid is removed. The vapors released during depressurization are condensed and collected in a receiving container. Once the oligomer sample has been collected, a vacuum is gradually applied to the reactor, from 1000 mbar absolute pressure (mBara) to a full vacuum, typically less than 2 mBara, in 15-minute increments of 250 mBara. Simultaneously, the reactor temperature setpoint is increased to 290°C. The reactor temperature setpoint is reached at the end of the vacuum drop, typically after 60 minutes. The following period is referred to as the polycondensation time while the contents are maintained at 290°C, under full vacuum, and stirred at 100 rpm. These conditions are maintained until the stirrer torque reaches a predetermined value of 15 Nm and the intrinsic viscosity (iV) is 0.54 dL / g, at which point the vacuum is released and the stirrer is stopped to degas the resulting polymer. Throughout the process, volatiles are condensed and collected as previously described. When degassing is complete, typically after 10 minutes, the molten polymer is discharged under a 2 barg overpressure and granulated through a cooling tank.

[0097] Then, to determine the metal content, the resulting polymer was subjected to various standard PET analysis procedures, including iV, carboxyl end group analysis (COOH), diethylene glycol analysis (DEG), CIE color analysis, and X-ray fluorescence (XRF) analysis.

[0098] Comparative Example 1 :

[0099]

[0100] In Comparative Example 1, 8.0 kg of PET-derived BHET was polymerized at 290 °C. As shown in the table, the resulting polymer had a COOH value of 30.7 microequivalents / g, an iV of 0.549 dl / g, an L* color of 45.61, and a b* color of 11.5. The oligomer COOH numbers cited in the table are relative to the starting material. The polymerization time was 75 minutes.

[0101] Comparative Example 2 :

[0102]

[0103] In Comparative Example 2, 8.0 kg of a commercial-scale PTA-based oligomer was polymerized at 290 °C. As shown in the table above, the resulting polymer had a COOH value of 26.4 microequivalents / g, an iV of 0.541 dl / g, an L* color of 63.99, and a b* color of 9.89. The COOH numbers of the oligomers cited in the table are relative to the starting material. The polymerization time was 95 minutes.

[0104] Comparative Example 3 :

[0105]

[0106] In Comparative Example 3, 6.92 kg vPTA was reacted with 3.62 kg ethylene glycol at 246 °C for 9 hours. As esterification occurred, the pressure in the sealed autoclave naturally increased, but was periodically reduced from 9 barg to 4 barg to allow water release. When no further pressure increase was observed, this indicated that esterification was complete, and the vessel was allowed to cool and the additives were added as in the previous example. The resulting oligomer was then polymerized at 290 °C. As can be seen in the table, the resulting polymer had a COOH value of 30.9 microequivalents / g, an iV of 0.535 dl / g, an L* color of 59.45, and a b* color of 12.56. For this example, no oligomer COOH number was available. The polymerization time was 75 minutes.

[0107] Example 4 :

[0108]

[0109] In Example 4, 0.26 kg of water was added to 10.58 kg of BHET derived from rPET, and the mixture was kept at 260°C for 55 min before polymerization at 290°C. As can be seen from the table, the resulting polymer had a COOH value of 21.5 microequivalents / g, an iV of 0.537 dl / g, an L* color of 42.06, and a b* color of 9.43. The oligomer COOH number of 535 microequivalents / g is significantly higher than that of the starting material, indicating that hydrolysis has occurred. The polymerization time was 70 min. In this case, and in subsequent examples, Co and P were added as a premixed solution in ethylene glycol (0.353 wt% Co, 0.204 wt% P).

[0110] Example 5 :

[0111] Examples 5, 6, and 7 employ a process model simulation of a three-vessel CP process operating at 450 metric tons / day to produce typical bottle-grade resin PET. The reactor series includes an esterifier, a UFPP reactor, and a trimmer vessel. The process conditions used for the simulation are described below:

[0112]

[0113] The key parameters of interest are the oligomer OH:COOH value of 3.63 and the dresser pressure of 2.29 mmHg. In the simulation, increasing the esterifier feed molar ratio upwards alters the oligomer OH:COOH, which affects reactivity and thus the predicted dresser vacuum requirement, as described in US 3551386 A. The effect of this prediction is shown in [reference needed]. Figure 7 .

[0114] An alternative way to represent this situation is to simulate the plant rate or plant capacity based on the variation of oligomer OH:COOH, while maintaining a constant dresser vacuum. This is in Figure 8 As shown in the image.

[0115] The change in oligomer OH:COOH from about 3.1 to about 3.6 clearly corresponds to about 5% of the plant's production capacity.

[0116] Example 6 :

[0117] The following is a predicted example of the same three-container CP process operated at 450 metric tons / day as in Example 5, producing the same typical bottle-grade PET resin, but this time using BHET feed.

[0118]

[0119] Key parameters of interest include the very high 508 oligomer OH:COOH and the significantly reduced 1.58 mmHg dresser pressure requirement. This oligomer OH:COOH is so high that it exceeds the production capacity chart above; in this case, to increase the dresser pressure to 2.3 mmHg, as in Example 5, the plant rate must be reduced to 390 tpd, representing a reduction in production capacity of approximately 20%. The deterioration of L* color is also significant.

[0120] Example 7 :

[0121] Keeping all parameters unchanged in Example 6, different amounts of water were added to a 24800 kg / h BHET, and the following results were obtained:

[0122]

[0123] This is Figure 9 The diagram shows the trimmer pressure required for the added %H2O.

[0124] A clear optimum was observed at approximately 7.2% H₂O, which corresponds to the maximum value predicted in the dresser vacuum requirement. Similarly, this is in Figure 10 The diagram shows the dresser vacuum requirement for oligomer OH:COOH. An optimal oligomer OH:COOH ratio of approximately 12:1 was observed. Clearly, based on the increased dresser vacuum requirement, the plant operation can be restored to full load of 450 tpd with the addition of approximately 7% water to the process.

[0125] Example 8 :

[0126] Examples 8 and 9 are process model simulations of a three-container CP process operating at 450 metric tons / day, using BHET feed and a linear reactor inserted between UFPP and trimmer containers to produce typical bottle-grade PET resin. The process conditions used for the simulation are described below:

[0127]

[0128] The key parameters of interest are the OH:COOH value of the oligomer in the linear reactor being 28.9 microequivalents / g, the iV of the oligomer in the linear reactor being 0.189 dl / g, and the dressing pressure being 1.50 mmHg.

[0129] Example 9 :

[0130] In this example, 960 kg / h of water (0.32 wt% based on PET) was added to the post-UFPP linear reactor.

[0131]

[0132] Now, the OH:COOH value of the linear reactor oligomer has decreased to 3.58, and the dressing pressure has dropped to 0.81 mmHg. Therefore, even though the addition of water increases the OH:COOH of the linear reactor, the hydrolysis reaction will still have an iV of 0.128 dl / g, meaning the dressing must operate more vigorously to maintain productivity. The weight percentage of water required to achieve the desired OH:COOH is significantly lower than in Example 7; this is a result of the higher molecular weight of the linear reactor oligomer.

[0133] Example 10 :

[0134] Examples 10 and 11 are process model simulations of a four-container CP process operating at 450 metric tons / day, using BHET feed, a linear reactor inserted after UFPP, an intermediate polymerizer (IP), and a finishing vessel to produce typical bottle-grade PET resin. The process conditions used for the simulation are described below:

[0135]

[0136] Key parameters of interest include, as in Example 8, the linear reactor oligomer OH:COOH value of 28.9, the linear reactor oligomer iV of 0.189 dl / g, the IP vacuum level of 5.81 mmHg, and the dresser pressure of 2.36 mmHg.

[0137] Example 11 :

[0138] In Example 11, 60 kg / h of water was added to the post-UFPP linear reactor:

[0139]

[0140] In Example 11, the OH:COOH value of the linear reactor oligomer was reduced to 3.58 as in Example 9, but this time, the dressing pressure was increased to 2.94 mmHg. Therefore, the addition of water increased the OH:COOH of the linear reactor, but this time, the use of IP allowed the dressing to fully utilize the increased reactivity. Again, it should be noted that the weight percentage of water required to achieve the desired OH:COOH is much lower than in Example 7; this is a result of the higher molecular weight of the linear reactor oligomer.

[0141] Comparative Example 12 :

[0142] Example 12 describes a laboratory glassware DMT transesterification process using the titanium catalyst TYZOR 131 organotitanate. The equipment used is as follows: Figure 4The process is outlined in the description, and the experimental details are as follows. DMT, ethylene glycol (EG), and the catalyst were placed in a glass container and heated to the set temperature of 200°C. As the reagents heated, the reaction began, and methanol (MeOH) vapor was released from the top of the column. As the temperature continued to rise, EG vapor was also generated, but it was returned to the flask through a Vigreux column, while the MeOH continued to flow through the condenser into the collection container.

[0143]

[0144] The key parameters of interest are an oligomer COOH content of 16.8 microequivalents / g and a collected amount of MeOH of 37 ml under these conditions.

[0145] Example 13 :

[0146] In Example 13, laboratory glassware DMT transesterification using the titanium catalyst TYZOR 131 organotitanate was repeated, but this time in the presence of 10g of distilled water.

[0147]

[0148] It can be seen that the COOH content of the oligomer increases significantly to 273 microequivalents / g, while still removing MeOH. A titanium catalyst is required because more conventional transesterification catalysts such as manganese acetate are deactivated in aqueous environments.

Claims

1. A method for producing an oligomeric PET substrate for use in the rPET manufacturing process, the method comprising: React rBHET from a recycled source or from vDMT, or a higher molecular weight oligomer derived from rBHET, with water to produce an oligomeric PET substrate represented by Formula I: (I) Where R1 is a carboxyl or hydroxyl end group, R2 is a carboxyl or hydroxyl end group, and n is the degree of polymerization. Wherein the method includes reacting rBHET with water, n is 1 to 10, and wherein the method includes reacting a higher molecular weight oligomer derived from rBHET with water, n is 20 to 50. The rBHET mentioned therein is a glycolysis product of PET waste.

2. The method of claim 1, wherein when the method includes reacting rBHET with water, n is 3 to 7, and wherein when the method includes reacting a higher molecular weight oligomer derived from rBHET with water, n is 25 to 35.

3. The method of claim 1 or claim 2, wherein when the method includes reacting rBHET with water, the oligomeric PET substrate has a CEG of 300 to 1500, and wherein when the method includes reacting a higher molecular weight oligomer derived from rBHET with water, the oligomeric PET substrate has a CEG of 40 to 200.

4. The method of claim 3, wherein when the method includes reacting rBHET with water, the oligomeric PET substrate has a CEG of 500 to 1200, and wherein when the method includes reacting a higher molecular weight oligomer derived from rBHET with water, the oligomeric PET substrate has a CEG of 150 to 190.

5. The method of claim 4, wherein when the method includes reacting rBHET with water, the oligomeric PET substrate has a CEG of 700 to 1100.

6. The method of claim 1, wherein the oligomeric PET substrate has a hydroxyl end group to carboxyl end group ratio in the range of 1.66 to 6.

66.

7. The method of claim 1, wherein the oligomeric PET substrate has a hydroxyl end group to carboxyl end group ratio in the range of 2.22 to 4.

0.

8. The method of claim 1, wherein when the method includes reacting rBHET with water, the water is added to the reaction zone in the range of 2% to 20% by weight relative to the oligomeric PET substrate, and wherein when the method includes reacting a higher molecular weight oligomer derived from rBHET with water, the water is added to the reaction zone in the range of 0.1% to 2% by weight relative to the oligomeric PET substrate.

9. The method of claim 1, wherein when the method includes reacting rBHET with water, the water is added to the reaction zone in the range of 5% to 10% by weight relative to the oligomeric PET substrate, and wherein when the method includes reacting a higher molecular weight oligomer derived from rBHET with water, the water is added to the reaction zone in the range of 0.1% to 0.5% by weight relative to the oligomeric PET substrate.

10. The method of claim 1, wherein the rBHET reacts with the water at a temperature between 120°C and 300°C, and the higher molecular weight oligomer derived from rBHET reacts with water at a temperature between 270°C and 300°C.

11. The method of claim 1, wherein the rBHET reacts with the water at a temperature between 150°C and 270°C, and the higher molecular weight oligomer derived from rBHET reacts with water at a temperature between 285°C and 295°C.

12. The method of claim 7, wherein the method includes a residence time of the rBHET or the higher molecular weight oligomer derived from the rBHET in the reaction zone between 30 minutes and 120 minutes.

13. The method of claim 7, wherein the method includes a residence time of the rBHET or the higher molecular weight oligomer derived from the rBHET in the reaction zone of 40 to 50 minutes.

14. The method of claim 1, wherein the rBHET reacts with the water at a pressure between 3 barg and 30 barg, and the higher molecular weight oligomer derived from rBHET reacts with water at a pressure between 10 barg and 50 barg.

15. The method according to claim 1, wherein the rBHET or a higher molecular weight oligomer derived from rBHET is reacted with water using at least one exogenously added catalyst, said catalyst being selected from antimony-containing catalysts, titanium-containing catalysts, zinc-containing catalysts, acetate-containing catalysts, manganese-containing catalysts, germanium-containing catalysts, aluminum-containing catalysts, and tin-containing catalysts.

16. The method according to claim 15, wherein the catalyst comprises at least one selected from antimony trioxide, antimony glycolate, antimony triacetate, titanium alkoxide, zinc acetate, and manganese acetate.

17. The method of claim 1, wherein the oligomeric PET substrate is fed directly or indirectly into the rPET manufacturing process.

18. An oligomeric PET substrate, said oligomeric PET substrate being produced by the method according to any one of claims 1 to 17.

19. The oligomeric PET substrate according to claim 18, wherein the oligomeric PET substrate has the following structure: (I) And further includes any two of the following features: i) n is the degree of aggregation from 1 to 10; ii) CEG between 300 and 1500; or iii) The ratio of hydroxyl terminal groups to carboxyl terminal groups in the range of 1.66 to 6.

66. Furthermore, the oligomeric PET substrate is used to synthesize polymers comprising 0-100% rPET.

20. The oligomeric PET substrate according to claim 18, wherein the oligomeric PET substrate has the following structure: (I) And further includes any two of the following features: i)n is the degree of polymerization, which is between 20 and 50; ii) CEG between 40 and 200; or iii) The ratio of hydroxyl terminal groups to carboxyl terminal groups in the range of 1.66 to 6.

66. Furthermore, the oligomeric PET substrate is used to synthesize polymers comprising 0-100% rPET.

21. A PET polymer made of 0-100% rPET, produced from an oligomeric PET substrate according to claim 19 or claim 20.

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