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BR-112023002927-B1 - METHOD FOR MANUFACTURING POLYESTER POLYMER CONTAINING POLYESTER RESIDUES AND SYSTEM FOR MANUFACTURING POLYESTER POLYMER CONTAINING POLYESTER RESIDUES

BR112023002927B1BR 112023002927 B1BR112023002927 B1BR 112023002927B1BR-112023002927-B1

Abstract

PROCESS AND SYSTEM FOR USING POLYESTER WASTE IN A CONTINUOUS POLYESTER POLYMERIZATION PROCESS. A method for manufacturing polyester polymer containing polyester waste in a continuous polymerization unit that includes: a) providing an intermediate prepolymer stream from the continuous polymerization unit and diverting a portion of the intermediate polymer stream to a centrifugal mixer; b) adding polyester waste to said centrifugal mixer to obtain a homogeneous melt stream; and c) combining the homogeneous melt stream with the remaining portion of the intermediate polymer stream to form an output stream, wherein the method is characterized in that the residual polyester in step b) is not heated or melted.

Inventors

  • Michael KOWALSKE
  • Yashwant AWASTHI
  • MIGUEL ANGEL OSORNIO
  • DURGESH CHAND KUSHWAHA

Assignees

  • Auriga Polymers, Inc

Dates

Publication Date
20260310
Application Date
20210819
Priority Date
20200820

Claims (15)

  1. 1. Method for manufacturing polyester polymer containing polyester waste in a continuous polymerization unit comprising the following steps: a) providing an intermediate prepolymer stream (10) from the continuous polymerization unit and diverting a portion of the intermediate prepolymer stream (20) to a centrifugal mixer (300); b) adding polyester waste to said centrifugal mixer (300) to obtain a homogeneous melt stream (65); and c) combining the homogeneous melt stream (65) with the remaining portion of the intermediate polymer stream (70) forming an output stream; wherein the method is characterized in that the polyester waste in step b) is not heated or melted before entering the centrifugal mixer (300).
  2. 2. Method according to claim 1, characterized in that the polyester waste is PCR flake or post-industrial PET waste.
  3. 3. Method according to claim 1, characterized in that the output stream contains up to 75% polyester waste.
  4. 4. Method according to claim 1, characterized in that the difference between the intrinsic viscosities of the homogeneous melt stream (65) and the remaining portion of the intermediate polymer stream (70) is in the range of + 0.10 dl/g, measured in accordance with ASTM D4603-96 at 25 °C.
  5. 5. Method according to claim 1, characterized in that the difference between the intrinsic viscosities of the homogeneous melt stream (65) and the remaining portion of the intermediate polymer stream (70) is in the range of + 0.05 dl/g, measured in accordance with ASTM D4603-96 at 25 °C.
  6. 6. Method according to claim 1, characterized in that the residence time of the polyester waste in the centrifugal mixer (300) is less than 3 minutes.
  7. 7. Method according to claim 1, characterized in that the energy used in the centrifugal mixer (300) is between 0.69 MJ/kg and 1.21 MJ/kg.
  8. 8. Method according to claim 1, characterized in that it further comprises an additional feed stream (95) entering the centrifugal mixer (300) containing a component selected from the group consisting of ethylene glycol, pigments, toners, dyes, mold release agents, flame retardants, plasticizers, stabilizers, chain extenders, impact modifiers and a combination thereof.
  9. 9. System for manufacturing polyester polymer containing polyester waste, the system performing the method as defined in claim 1, characterized in that it comprises: a centrifugal mixer (300) with at least one first inlet, a second inlet, and an outlet; a first tube (40) configured to introduce polyester waste into the first inlet of the centrifugal mixer (300); a prepolymer flow line configured to divert a portion of the prepolymer flow (10) to the second inlet of the centrifugal mixer (300), wherein a homogeneous melt flow (65) exits the outlet of the centrifugal mixer (300); a mixing apparatus (400) configured to combine the homogeneous melt stream (65) with the remaining portion of the intermediate polymer stream (70) forming an outlet stream; wherein the polyester waste is not heated or melted before entering the centrifugal mixer (300); wherein the system performs the method as defined in claim 1.
  10. 10. System according to claim 9, characterized in that the polyester waste is PCR flake or post-industrial PET waste.
  11. 11. System according to claim 9, characterized in that the output stream contains up to 75% polyester waste.
  12. 12. System according to claim 9, characterized in that the difference between the intrinsic viscosities of the homogeneous melt stream (65) and the remaining portion of the intermediate polymer stream (70) is in the range of + 0.10 dl/g, measured in accordance with ASTM D4603-96 at 25 °C.
  13. 13. System according to claim 9, characterized in that the difference between the intrinsic viscosities of the homogeneous melt stream (65) and the remaining portion of the intermediate polymer stream (70) is in the range of + 0.05 dl/g, measured in accordance with ASTM D4603-96 at 25 °C.
  14. 14. System according to claim 9, characterized in that the residence time of the polyester waste in the centrifugal mixer (300) is less than 3 minutes.
  15. 15. System according to claim 9, characterized in that the energy used in the centrifugal mixer (300) is between 0.69 MJ/kg and 1.21 MJ/kg.

Description

FIELD OF THE INVENTION [0001] This invention relates to an energy-efficient method and system for utilizing polyester waste in a continuous polyester polymerization process. In particular, the waste is mixed with a side stream of prepolymer in a centrifugal mixer and returned to the unit to complete the polymerization. FUNDAMENTALS OF THE INVENTION [0002] In order to meet the global need for a circular economy in which plastics are reused and recycled, there is a need for low-cost processes to recycle these plastics back to the same state as the original virgin plastic. Poly(ethylene terephthalate), PET, is the plastic of choice for use in water bottles, soft drinks, and other packaging items. These bottles and other containers are easily recovered from consumer recycled waste by sorting, granulation, washing, and subsequent classification into streams of transparent polyester granules or flakes (PCR). In order to meet regulations targeting the use of polyester for food contact applications, further purification of the PCR is necessary to remove any absorbed contaminants and increase the molecular weight to that of standard bottle resins in order to be able to reuse the PCR. Major owners of carbonated soft drink and water bottle brands have set targets that the PCR content in the PET resin they purchase will be 50% by 2030. [0003] It is also known for chemically depolymerizing post-consumer polyester waste (PCR) into its initial feedstocks (monomers) which can then be used to manufacture PET resins. These processes use methanolysis, hydrolysis or glycolysis reactions to depolymerize the waste polyester into basic feedstocks such as dimethyl terephthalate, terephthalic acid, glycol or the monomer (bishydroxymethyl terephthalate). All these processes require additional steps to purify the feedstocks or monomers before they can be used as feedstock or blended with virgin feedstock for PET manufacturing, which leads to an increase in cost. [0004] In a polyethylene terephthalate (PET) methanolysis process, residual PET reacts with methanol to produce the feedstocks dimethyl terephthalate (DMT) and ethylene glycol (EG). These reaction products must be purified to meet the same specifications as virgin feedstock before being used to produce virgin polyester (polyester formed from its feedstocks). However, most commercial PET production plants use terephthalic acid (TA) instead of DMT, and therefore further processing is required to convert DMT to TA. [0005] PET hydrolysis is the reaction of waste PET with water to depolymerize it into TA and EG. However, certain types of contaminants commonly present in PET waste are known to be very difficult to remove and require additional purification steps to obtain high-purity TA. [0006] PET glycolysis is the reaction of residual PET with glycol (such as EG) to produce the monomer bis-hydroxyethyl terephthalate (BHET) and other oligomers. This process has significant advantages over methanolysis or hydrolysis, primarily because BHET can be used as a feedstock in a DMT or TA polyester production process without major modifications to the production facilities. However, BHET must be purified before it can be used to manufacture PET resins with the same quality standards as virgin PET. [0007] Several processes have been disclosed in which PCR is melted in an extruder and added to the esterification reactor of a continuous polymerization unit. U.S. Patent Application 2003/0134915 discloses a process in which PCR is melted, with the addition of ethylene glycol, and extruded into the esterification reactor for depolymerization with the oligomeric esterification product; this reaction product is then polymerized in subsequent reactors of the continuous polymerization unit. Vacuum in the final polycondensation reactor (“finisher”) removes contaminants that were absorbed into the PCR. The amorphous granules can be solid-phase polymerized to the molecular weight required for the container application or can be polymerized to the final molecular weight in the finisher. Current processes for adding PCR flake to existing CP lines are run at an average of 25% recycled content. The latest CP lines installed have a capacity of over 30 tons/day, and adapting these lines to the addition of 50% PCR would require extruders capable of operating at 15 tons/hour, exceeding the rate of current extruder technology. The capital cost for one or more high-throughput extruders and the cost of energy lost in the motor and gearboxes of these extruders make this technology unattractive. [0008] In addition, the glycol recovered during the continuous PET manufacturing process is recycled back to be used with virgin glycol in the initial esterification process with terephthalic acid. Contaminants and degradation products from the addition of a large quantity of PCR flakes would require the recovered glycol to be purified before being used as an initial raw material. [0009] Document WO2019/162265 discloses a c