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US-12624189-B2 - Process for recycling polyethylene terephthalate using a separated feedstock

US12624189B2US 12624189 B2US12624189 B2US 12624189B2US-12624189-B2

Abstract

One aspect is a method for producing a first intermediate product. A feedstock is provided that comprises a first polyester. The feedstock is separated into a least a first feedstock amount and a further feedstock amount. The first feedstock amount and the further feedstock amount comprise the first polyester. The first feedstock amount is transported into a first reaction line, and the further feedstock amount is transported into a further reaction line. In a reaction line the first polyester is contacted with a further amount of a first organic compound, a weight average molar mass of the first polyester is reduced; the first polyester is contacted with a further organic compound to obtain a further initial mixture; a weight average molar mass of the first polyester is reduced to obtain a first intermediate mixture. The first intermediate mixture comprises a first intermediate product and the further organic compound. At least one process parameter varies by at least 10%, between the first reaction line and the further reaction line.

Inventors

  • Suresh L. MAKHIJA
  • Dhanvant YEOLA
  • Christian Neumann

Assignees

  • REVALYU RESOURCES GMBH

Dates

Publication Date
20260512
Application Date
20230919
Priority Date
20220920

Claims (12)

  1. 1 . A method for producing a first intermediate product, comprising the steps of a. providing a feedstock that comprises a first polyester; b. separating the feedstock into at least a first feedstock amount and a further feedstock amount, wherein the first feedstock amount and the further feedstock amount comprise the first polyester; c. transporting i. the first feedstock amount into a first reaction line, and ii. the further feedstock amount into a further reaction line; wherein a reaction line comprises the following steps: I. contacting the feedstock amount with a first amount of a first organic compound, in a volume section V 1 , to obtain a first initial mixture, wherein the first amount is in the form of a liquid, and wherein a temperature of the first initial mixture, in the volume section V 1 , is in the range of 60° C. to 80° C.; II. contacting the first polyester with a further amount of the first organic compound in a volume section V 2 , III. reducing a weight average molar mass of the first polyester in the volume section V 2 , wherein, after the reduction step has been completed in the volume section V 2 , the first polyester has an intrinsic viscosity in the range of 0.10 dL/g to 0.45 dL/g, IV. contacting the first polyester with a further organic compound, in a volume section V 3 , to obtain a further initial mixture; V. reducing a weight average molar mass of the first polyester, in the volume section V 3 , to obtain a first intermediate mixture, wherein the first intermediate mixture comprises i. a first intermediate product that has an intrinsic viscosity in the range of 0.010 dL/g to 0.090 dL/g, ii. the further organic compound; wherein at least one process parameter varies by at least 10% between the first reaction line and the further reaction line; the first polyester in the feedstock is in the form of a plurality of fragments, and wherein the following applies: A. at least 60 wt-% of the fragments of the first polyester in the first feedstock amount has a thickness that is less than 1.0 mm, B. at least 60 wt-% of the fragments of the first polyester in the further feedstock amount has a thickness that is 1.0 mm or larger, with the intrinsic viscosity and the wt-% of the fragments with a certain thickness determined according to the methods described herein.
  2. 2 . A method for producing a first intermediate product, comprising the steps of a. providing a feedstock that comprises a first polyester; b. separating the feedstock into at least a first feedstock amount and a further feedstock amount, wherein the first feedstock amount and the further feedstock amount comprise the first polyester; c. transporting i. the first feedstock amount into a first reaction line, and ii. the further feedstock amount into a further reaction line; wherein a reaction line comprises the following step: I. contacting the feedstock amount with a first amount of a first organic compound, in a volume section V 1 , to obtain a first initial mixture, wherein the first amount is in the form of a liquid, and wherein a temperature of the first initial mixture, in the volume section V 1 , is in the range of 60° C. to 80° C.; II. contacting the first polyester with a further amount of the first organic compound in a volume section V 2 , III. reducing a weight average molar mass of the first polyester in the volume section V, wherein, after the reduction step has been completed in the volume section V 2 , the first polyester has an intrinsic viscosity in the range of 0.10 dL/g to 0.45 dL/g; d. combining the first polyester in the first reaction line with the first polyester in the further reaction line to obtain a combined first polyester; e. contacting the combined first polyester with a further organic compound, in a volume section V 3 , to obtain a further initial mixture; f. reducing the weight average molar mass of the combined first polyester, in the volume section V 3 , to obtain a first intermediate mixture, wherein the first intermediate mixture comprises i. a first intermediate product that has an intrinsic viscosity in the range of 0.010 dL/g to 0.090 dL/g, ii. the further organic compound; wherein at least one process parameter varies by at least 10% between the first reaction line and the further reaction line; the first polyester in the feedstock is in the form of a plurality of fragments, and wherein the following applies: A. at least 60 wt-% of the fragments of the first polyester in the first feedstock amount has a thickness that is less than 1.0 mm, B. at least 60 wt-% of the fragments of the first polyester in the further feedstock amount has a thickness that is 1.0 mm or larger, with the intrinsic viscosity and the wt-% of the fragments with a certain thickness determined according to the methods described herein.
  3. 3 . The method according to claim 1 , wherein the at least one process parameter is at least one or all of the following: a. a mass ratio of a feedstock amount to the first organic compound in the volume section(s) V 2 ; b. the mass ratio of the further organic compound to the first polyester in the volume section(s) V 3 ; c. a residence time in at least one or all of the following: the volume section(s) V 2 , the volume section(s) V 3 ; d. a temperature in at least one or all of the following: the volume section(s) V 2 , the volume section(s) V 3 ; e. a pressure in at least one or all of the following: the volume section(s) V 2 , the volume section(s) V 3 ; with the above parameters determined according to the methods described herein.
  4. 4 . The method according to claim 1 , wherein at least one or all of the following applies: a. the mass ratio of the first polyester to the first organic compound in the volume section V 2 of the first reaction line is in the range of 0.1 to 10.0; b. the mass ratio of the first polyester to the first organic compound in the volume section V 2 of the further reaction line is in the range of 0.4 to 30.0; with the mass ratios of the first polyester to the first organic compound in the first and further reaction lines determined according to the method described herein.
  5. 5 . The method according to claim 1 , further comprising the step of reducing at least one physical dimension of the first polyester.
  6. 6 . The method according to claim 1 , wherein the first polyester is selected from the group consisting of a polyethylene terephthalate, a polybutylene terephthalate, a polylactide, a polytrimethylene terephthalate, a polyethylene naphthalate, a polycarbonate, a polyester carbonate, a polyarylate, a polyester resin, and a combination of two or more thereof.
  7. 7 . The method according to claim 1 , wherein the first organic compound has at least one or all of the following properties: a. comprises at least two hydroxyl groups; b. a molar mass of at least 60 g/mol; c. a boiling point of at least 192° C.
  8. 8 . The method according to claim 2 , wherein the at least one process parameter is at least one or all of the following: a. a mass ratio of a feedstock amount to the first organic compound in the volume section(s) V 2 ; b. the mass ratio of the further organic compound to the combined first polyester in the volume section(s) V 3 ; c. a residence time in at least one or all of the following: the volume section(s) V 2 , the volume section(s) V 3 ; d. a temperature in at least one or all of the following: the volume section(s) V 2 , the volume section(s) V 3 ; e. a pressure in at least one or all of the following: the volume section(s) V 2 , the volume section(s) V 3 ; with the above parameters determined according to the methods described herein.
  9. 9 . The method according to claim 2 , wherein at least one or all of the following applies: a. the mass ratio of the first polyester to the first organic compound in the volume section V 2 of the first reaction line is in the range of 0.1 to 10.0; b. the mass ratio of the first polyester to the first organic compound in the volume section V 2 of the further reaction line is in the range of 0.4 to 30.0; with the mass ratios of the first polyester to the first organic compound in the first and further reaction lines determined according to the method described herein.
  10. 10 . The method according to claim 2 , further comprising the step of reducing at least one physical dimension of the first polyester.
  11. 11 . The method according to claim 2 , wherein the first polyester is selected from the group consisting of a polyethylene terephthalate, a polybutylene terephthalate, a polylactide, a polytrimethylene terephthalate, a polyethylene naphthalate, a polycarbonate, a polyester carbonate, a polyarylate, a polyester resin, and a combination of two or more thereof.
  12. 12 . The method according to claim 2 , wherein the first organic compound has at least one or all of the following properties: a. comprises at least two hydroxyl groups; b. a molar mass of at least 60 g/mol; c. a boiling point of at least 192° C.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This Utility Patent Application claims priority under 35 U.S.C. § 371 to International Application Serial No. PCT/EP2023/075815, filed Sep. 19, 2023, which claims the benefit of EP patent application Ser. No. 22196668.2, filed Sep. 20, 2022; which are both incorporated herein by reference in their entirety. FIELD OF THE INVENTION The invention pertains to a method for producing a first intermediate product from a first polyester, e.g., a method for producing polyethylene terephthalate (PET) oligomers from PET flakes. The invention also pertains to the first intermediate product obtained by the aforementioned method. The invention further pertains to a method for producing a further intermediate product using the first intermediate product, e.g., the production of PET polymers using the PET oligomers. The invention also pertains to the further intermediate product. The invention also pertains to a product that comprises the further intermediate product, e.g., PET yarn. BACKGROUND Polyethylene terephthalate (PET) is one of the most widely used and economically important thermoplastic polymers. PET is used for, e.g., fibres for clothing, containers for food and beverages, such as bottles, and for films. As a result of the wide usage of PET and its non-biodegradability, PET-containing products have created serious ecological concerns. Methods for recycling PET are thus very important in order to reduce the amount of PET waste. One method of recycling is the reduction of PET into the chemical components that are used to produce PET, followed by the polymerisation of the chemical components to obtain recycled PET. This is known as chemical recycling. Disadvantages of the chemical recycling process include the following: the recycling process is generally very energy inefficient, is ecologically unfriendly, and has a low through-put. In particular, if the PET is depolymerised to monomers, this requires long depolymerisation times, and leads to the production of large amounts of degradation products that can't be removed from the recycled PET. Very often it is also required to mix the PET that is chemically recycled with virgin PET in order to obtain a recycled PET product of sufficiently high quality. The chemical recycling of polyethylene terephthalate is described by, e.g., Bartolome et al. (2012), Recent Developments in the Chemical Recycling of PET, Material Recycling—Trends and Perspectives. EP3778744 A1 discloses a method for recycling PET that includes mixing virgin PET liquid material with the recycled PET (virgin PET liquid material is defined as the chemical components required to produce virgin PET, i.e., PET that is not obtained using a recycling method). CN109134244 A discloses a method for recycling PET that uses both glycol and methanol to depolymerise PET. CN108395373 A discloses a method for recycling PET that uses ethylene glycol and propylene glycol. Objects An object of the present invention is to at least partially overcome at least one of the disadvantages encountered in the state of the art. It is a further object of the invention to provide a method for producing a first intermediate product, wherein the method reduces the degradation of a first polyester used to obtain the first intermediate product. It is a further object of the invention to provide a method for producing a first intermediate product, wherein the method reduces the degradation of the first intermediate product. It is a further object of the invention to provide a method for producing a first intermediate product, wherein the method reduces the variation in the molar weight of the first intermediate product. It is a further object of the invention to provide a method for producing a first intermediate product, wherein the method can remove more impurities during the production of the first intermediate product. Sources of impurities include the feedstock (amount) (used for the method for producing the first intermediate product), which contain impurities such as sand and polyvinyl chloride. It is a further object of the invention to provide a method for producing a first intermediate product, wherein the method can remove more caustic during the production of the first intermediate product. Caustic may be present due to, e.g., the feedstock (amount) (used for the method for producing the first intermediate product) having being subjected to a caustic wash. It is a further object of the invention to provide a method for producing a first intermediate product, wherein the method can more effectively remove adhesives adhering to the feedstock (amount) (used for the method for producing the first intermediate product). It is a further object of the invention to provide a method for producing a first intermediate product, wherein the transport rate of the feedstock (amount) through a production plant is increased. Here the feedstock (amount) refers to the feedstock (amount) of the method