EP4429809A2 - Dispositif et procédé pour la fabrication d'un dépolymère de polyester ainsi que dispositif et procédé pour la fabrication d'un polyester - Google Patents

Dispositif et procédé pour la fabrication d'un dépolymère de polyester ainsi que dispositif et procédé pour la fabrication d'un polyester

Info

Publication number
EP4429809A2
EP4429809A2 EP22813935.8A EP22813935A EP4429809A2 EP 4429809 A2 EP4429809 A2 EP 4429809A2 EP 22813935 A EP22813935 A EP 22813935A EP 4429809 A2 EP4429809 A2 EP 4429809A2
Authority
EP
European Patent Office
Prior art keywords
polyester
depolymer
recyclate
rpet
depolymerizing agent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22813935.8A
Other languages
German (de)
English (en)
Inventor
Matthias Schönnagel
Christopher Hess
Martin Hittorff
Michael Schubert
Alexander PAWELSKI
Heinrich Koch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Uhde Inventa Fischer GmbH
ThyssenKrupp AG
Original Assignee
Uhde Inventa Fischer GmbH
ThyssenKrupp AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Uhde Inventa Fischer GmbH, ThyssenKrupp AG filed Critical Uhde Inventa Fischer GmbH
Publication of EP4429809A2 publication Critical patent/EP4429809A2/fr
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/18—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material
    • C08J11/22—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic oxygen-containing compounds
    • C08J11/24—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic oxygen-containing compounds containing hydroxyl groups
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/18—Stationary reactors having moving elements inside
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/78—Preparation processes
    • C08G63/785—Preparation processes characterised by the apparatus used
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/14—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with steam or water
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/18—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material
    • C08J11/22—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic oxygen-containing compounds
    • C08J11/26—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic oxygen-containing compounds containing carboxylic acid groups, their anhydrides or esters
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

  • PET recycling the recovery of polyethylene terephthalate waste
  • environmental protection and sustainability in the use of resources will require ever higher recycling rates in the coming decades.
  • this quota must reach 100%.
  • An approved recycling process is the chemical depolymerization and subsequent repolymerization of PET.
  • Depolymerization can take place, for example, with water (hydrolysis) or with ethylene glycol (glycolysis), in which case the long-chain PET starting material is split into shorter chains (monomers, oligomers, prepolymer). .
  • COOH end groups formed by hydrolysis must be esterified again, this can preferably be done with ethylene glycol.
  • the depolymerized recyclate can then be polycondensed again at elevated temperature under vacuum conditions in special polycondensation apparatus which correspond to the prior art.
  • EP 0 942 035 B1 describes a process for recovering linear polyester, in which recycled material is melted in an extruder and prepolymer is obtained by simultaneous hydrolytic and glycolytic degradation. The melt is then returned to a virgin polyester manufacturing process for polycondensation.
  • the disadvantage of this technique is the use of extruders to melt the recyclate. Extruders are limited in capacity, have high acquisition costs and have to be operated with electrical energy.
  • rPET is also melted in an extruder and then glycolized with ethylene glycol (EG).
  • EG ethylene glycol
  • GB 610 136 A describes the depolymerization of aromatic polyesters with ethylene glycol at the boiling point of ethylene glycol or slightly above it in a reaction vessel and the subsequent repolymerization.
  • the reaction rate at these temperatures is too low for large capacities and when higher temperatures are used, the ethylene glycol escapes from the process.
  • a glycolysis process can be carried out in stirred reactors with feed of molten PET and EG under pressure, the reaction rate can be increased boosted by special catalysts, PET can be melted in a mixture of PET flakes and EG, PET can be melted in an oligomeric mixture of partially glycolyzed PET, PET can be melted by adding small amounts of EG by reactive depolymerization extrusion in extruders, all mentioned methods can also be carried out continuously.
  • Fine or coarse filtration has always been common.
  • Decolorizing with activated charcoal is new.
  • a technically different approach is the early detection of unexpected contamination in the supplied rPET and a quick reaction to it with minimal waste and identification of the supplied rPET batch.
  • the present invention specifies a device and a process for the production of a polyester depolymer.
  • the device and the method should be as cost-effective and technically simple and thus reliable as possible.
  • it is an object of the present invention to specify a device for producing a polyester by means of which the polyester depolymer produced according to the present invention can be further processed into a polyester.
  • an energetically and materially optimized process is sought that can cover recycling rates of 25% to 100%, with which high-quality products can be manufactured and which have low investment and operating costs having.
  • the present invention thus relates to a device for producing a polyester depolymer, comprising a mixing container with an inlet for solid polyester recyclate, an inlet for a liquid polyester depolymer and an outlet for a mixture containing or consisting of the polyester recyclate and the polyester depolymer, at least one feed option for a depolymerizing agent downstream of the outlet of the mixing tank, and a switch downstream of the feed option for splitting the polyester depolymer stream into at least two partial flows, one partial flow being connected to the inlet for the polyester depolymer of the mixing tank is in connection, and the further partial flow or the further partial flows serve to remove the polyester depolymer from the device, with all components of the device being in fluid communication by means of a pipeline.
  • the switch is preferably preceded by a receiving container for intermediate storage of the polyester depolymer.
  • a mixer in particular a static mixer, is connected downstream of the feed option for a depolymerizing agent.
  • the depolymerizing agent can contain further agents and/or additives which are advantageous for a later modification of the polyester produced therefrom.
  • the task option for a depolymerizing agent is a temperature control device, preferably a heat exchanger, in particular a Be tube bundle heat exchanger downstream, preferably be downstream of the mixer according to the preceding claim.
  • At least one storage device for storing the polyester is connected upstream of the inlet for the polyester recyclate, which is connected in particular to a conveyor device, such as a conveyor screw, rotary valve, weighing device and/or feed chute with the inlet for the polyester recyclate connected to the mixing tank.
  • a conveyor device such as a conveyor screw, rotary valve, weighing device and/or feed chute with the inlet for the polyester recyclate connected to the mixing tank.
  • the mixing container and/or the receiving container preferably has at least one possibility for applying a vacuum, with the vacuum device preferably having a spray condenser.
  • the device has at least one supply of inert gas, which opens out, for example, into the storage device, the conveyor device and/or the storage container.
  • the pipeline can preferably have at least one feed pump.
  • the mixing container has at least one device for mixing polyester recyclate and polyester depolymer, for example a dynamic mixer, a screw pump and/or a jet mixer, which in particular has flat jet nozzles, and/or is free of active mechanical mixing devices, such as stirring elements.
  • a dynamic mixer for example a dynamic mixer, a screw pump and/or a jet mixer, which in particular has flat jet nozzles, and/or is free of active mechanical mixing devices, such as stirring elements.
  • At least one device for separating particulate and/or chemical impurities is preferably provided within the pipeline, in particular upstream of the removal of the polyester depolymer from the device and/or the receiving container.
  • the at least one device for separating particulate and/or chemical contaminants is preferably selected from the group consisting of starting from particle filters, in particular for separating particles with a diameter of ⁇ 10 ⁇ m, activated carbon filters, ion exchangers, distillation and crystallization apparatuses and combinations thereof.
  • Mixing container, switch, pipeline and, if necessary, receiving container, mixer and temperature control device can be heatable and/or thermally insulated, for example by means of a double-walled structure in which a liquid or gaseous heat exchanger can be guided.
  • the mixing container and/or the conveying device preferably have a pressure relief device which, at a predetermined pressure, derives excess pressure from the device, for example a pressure relief valve and/or a bursting disk.
  • a pressure relief device which, at a predetermined pressure, derives excess pressure from the device, for example a pressure relief valve and/or a bursting disk.
  • the present invention relates to a process for producing a polyester depolymer in which solid polyester recyclate is mixed with a liquid polyester depolymer and converted into a melt, a depolymerizing agent is added to the melt at least once and with the melt is reacted, whereby polyester depolymer is produced, and then a partial flow of the polyester depolymer produced is used for mixing with the polyester recyclate and the remainder of the polyester depolymer is obtained as a product.
  • the method according to the invention can be carried out in particular with the device according to the invention described above.
  • a preferred embodiment of the method provides that the liquid polyester depolymer when mixed with the polyester recyclate at a temperature of 240 to 320 ° C, preferably 250 to 300 ° C, particularly preferably 260 to 290 ° C and / or the polyester recyclate during mixing with the polyester depolymer at a temperature of from -40.degree. C. to 230.degree. C., preferably from 0.degree. C. to 100.degree. C., particularly preferably from 10.degree. C. to 50.degree.
  • the thermal damage due to the significantly faster melting at temperatures well above the melting point of the polyester recyclate is advantageously reduced by the shortest possible residence times.
  • the required higher temperatures can be made possible by using only small amounts of depolymerizing agent.
  • the nitrogen inerting required for safe plant operation is also used to minimize thermal-oxidative damage at the desired process temperatures.
  • Mixing is preferably carried out using a dynamic mixer, a screw pump, an agitator and/or a jet mixer, with a jet mixer being particularly preferred.
  • a mixing ratio (weight/weight) of polyester recyclate with polyester depolymer of at least 1:5, preferably at least 1:2 or particularly preferably less than or equal to 1:1.4 is selected in the process according to the invention.
  • the depolymerizing agent based on the proportion by mass of recycled polyester, is preferably added in proportions by mass of less than or equal to 1 to 0.1 (depolymerizing agent), preferably less than or equal to 0.05 (depolymerizing agent), particularly preferably less than or equal to 0.01 (depolymerizing agent).
  • the advantage is that the less depolymerizing agent that is added, the less depolymerizing agent has to be removed again later with increased expenditure on equipment.
  • a residence time of the mixture from mixing the polyester recyclate with the polyester depolymer to addition of the depolymerizing agent of 0.5 to 30 minutes, preferably 1 to 10 minutes, particularly preferably 2 to 5 minutes and/or a total residence time of ⁇ 1.5 hours, preferably ⁇ 60 min, particularly preferably ⁇ 30 min set.
  • the COOH end group concentration of the polyester depolymer removed as product is advantageously less than or equal to 250 mmol/kg, preferably less than or equal to 150 mmol/kg, particularly preferably less than or equal to 50 mmol/kg.
  • the melt can be adjusted to an average degree of polymerization of less than 50, preferably less than 30, particularly preferably less than 20, at the latest when the depolymerizing agent is added.
  • the melt is preferably mixed after the addition of the diol and before it is divided into partial streams, for example by means of a static mixer.
  • the melt is heated, preferably to temperatures of 240 to 320° C., preferably 250 to 300° C., particularly preferably 260 to 280° C., in particular by means of a heat exchanger, the residence time of the melt during the Tempering is 1 to 30 min, preferably 2 to 20 min, particularly preferably 5 to 10 min.
  • the depolymerizing agent is particularly preferably selected from the group consisting of diols, eg monoethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,3-propanediol, 1,4-butanediol, cyclohexanedimethanol and/or ethylene diglycol, in particular one used for the production of the original polyester diol corresponding to the diol used, a mixture of different diols, water, organic acids, in particular lactic acid, and mixtures thereof, it being possible for the depolymerizing agent to contain further additives.
  • diols eg monoethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,3-propanediol, 1,4-butanediol, cyclohexanedimethanol and/or ethylene diglycol, in particular one used for the production of the original polyester diol corresponding to the diol used, a mixture of different diol
  • a diol corresponding to the diol used for the preparation of the original polyester is the diol from which the corresponding alcoholic repeating unit in the corresponding polyester is derived, ie, for example, ethylene glycol for polyethylene terephthalate.
  • diols can also be used, or the corresponding (open-chain) hydroxy acids derived from the underlying lactones, e.g. for polylactic acid, lactic acid, etc.
  • the mixing is preferably carried out under reduced pressure or atmospheric pressure, preferably under reduced pressure, by applying a vacuum, vapors drawn off by the vacuum in particular being washed out by means of a spray condenser.
  • the polyester depolymer removed as a product is cleaned, preferably filtered and/or chemically cleaned, with particulate and/or chemical impurities being removed.
  • This can be done, for example, by means of a particle filter and/or ion exchanger.
  • Further possible purification steps are the treatment of the polyester depolymer with activated charcoal, the distillation of the polyester depolymer, for example in a thin-film evaporator, and/or the crystallization of the polyester depolymer.
  • the mixing, melting and reacting is preferably carried out in an inert atmosphere with an oxygen content of ⁇ 5% by volume, preferably ⁇ 1% by volume, particularly preferably ⁇ 0.1% by volume, in particular a nitrogen atmosphere.
  • the polyester depolymer produced is preferably temporarily stored or collected and/or filtered before it is separated into partial streams.
  • the polyester recyclate is rPET and the depolymerizing agent is the diol ethylene glycol, rPBT (polybutylene terephthalate recyclate) and the hydrolyzing agent is the diol 1,4-butylene glycol, rPTT (polytrimethylene terephthalate recyclate) and the hydrolyzing agent is the diol 1,3-propanediol, rPBS (polybutylene succinate recyclate) and the hydrolyzing agent is the diol 1,4-butylene glycol, rPEN (polyethylene naphthale recyclate) and the hydrolyzing agent is the diol ethylene glycol, rPEF (polyethylene furanoate recyclate) and the hydrolyzing agent is the diol ethylene glycol or the polyester recyclate is rPLA (polylactic acid recyclate) and the hydrolyzing agent s water and/or lactic acid.
  • the polyester recyclate is preferably fed in the form of granules and/or flakes.
  • the process can be operated continuously.
  • An exemplary and particularly preferred independent depolymerization process in several stages, in which rPET is partially hydrolyzed by mixing it into hot depolymer, monomer or prepolymer in a container and glycolized during the subsequent melting with small amounts of EG in a heat exchanger and the resulting depolymer is cleaned and is polymerized to form a high-quality polyester, characterized by a) exclusion of atmospheric oxygen by rendering it inert with N2 to increase safety and quality, b) a high melting and depolymerization temperature of 260 to 290°C, particularly preferably 270°C below almost atmospheric Conditions for the addition of rPET, c) mass ratios of rPET to EG of less than or equal to 1:0.25, preferably less than 1:0.1, particularly preferably less than 1:0.05, d) residence times of the depolymerization of less than or equal to 1, 5 hours, preferably less than 60 min, particularly preferably less than 30 min, e) low
  • the proportion of rPET used reduces the amount of PTA and EG required in the ES stage and the energy released as a result can be used to melt the rPET.
  • the integration into existing vacuum systems can be used to generate the required negative pressure. It can be integrated into existing EG dosing systems. Existing monomer or prepolymer lines can be used to fill the depoly system. i) Use of the existing processing stages for water and EG of a PET plant, j) Short reaction times to quality problems with rPET with low levels of contamination, k) both a preferred continuous mode of operation and a batch mode, or also called batch mode, are possible. l) minimal arrival and departure quantities, and a device (rPET monomer jet mixer) for inexpensive and efficient mixing of large quantities of rPET into hot monomer,
  • Mixers in general (e.g. an agitator, a dynamic mixer, screw conveyor) and preferably using the impact energy of a jet or several jets of liquid monomer, prepolymer or depolymer, entraining and mixing in these liquid jets falling and/or pressed rPET, see above that the resulting mixture of melted rPET and liquid depolymer can be conveyed from a small reservoir using commercially available feed pumps, with the minimum mixing temperature of rPET and liquid depolymer always being set above the solidification range of this mixture.
  • the present invention relates to a device for the production of polyesters, comprising, connected in series, a device according to the invention for the production of a polyester depolymer as described above and at least one polycondensation stage.
  • the present invention makes it possible, for example, to retrofit an existing device for the production of polyesters with the device for the production of a polyester depolymer, or to set up separate devices for the production of polyesters.
  • the device for producing polyesters preferably comprises the stages described above, ie for example at least one falling-film reactor or a prepolymerizer, at least one disc reactor or a final polymerizer and optionally one or more devices for carrying out a solid-phase post-condensation.
  • the present invention relates to a process for the production of polyesters, in which a polyester depolymer is first produced in the inventive manner described above and this is subsequently polymerized to give the polyester.
  • the prepolymerization stage can be skipped in this process.
  • PET stands for polyethylene terephthalate, a polyester which can be produced in PET plants by esterification of the raw materials PTA (purified terephthalic acid) and EG (ethylene glycol) or, to a lesser extent, by transesterification of the raw materials DMT (dimethyl terephthalate) and EG and subsequent polycondensation in each case.
  • PTA purified terephthalic acid
  • EG ethylene glycol
  • DMT dimethyl terephthalate
  • EG ethylene glycol
  • subsequent polycondensation in each case.
  • purified terephthalic acid less terephthalic acid or non-purified terephthalic acid can be used as long as the desired quality of the end product is achieved and material properties of the PET plant are not adversely affected.
  • PET is a macromolecule made up of many of the same basic building blocks.
  • the average degree of polymerization also referred to below as Pn or also as the average chain length, indicates the number of basic building blocks per PET molecule.
  • degree of polymerization is synonymous with degree of polycondensation.
  • the basic monomeric building block is -[OOC-CeH ⁇ COO-fCHzh]- with a molecular weight of 192 g/mol.
  • a Pn of 5 means that there are 5 basic building blocks in the PET molecule as in are strung together in a chain.
  • the two end groups can each be an OH- from ethylene glycol or a -COOH from terephthalic acid, or twice the same end group.
  • the Wallace-Hume-Carothers equation for linear AA/BB systems is valid, which states that sufficiently high chain lengths can only be achieved if the conversion of reacted COOH end groups is sufficiently high, i.e. only small amounts of unreacted COOH end groups are present.
  • the viscosity of PET is usually given as intrinsic viscosity, called IV below, with the unit dl/g.
  • Effective catalysts e.g. antimony, titanium or aluminum compounds
  • a wide variety of additives are also added, such as stabilizers, dyes, matting agents or other auxiliaries, in order to achieve certain properties.
  • PTA, DMT, EG are referred to as monomeric starting materials.
  • a chemical reaction first produces an intermediate product, also known as a monomer.
  • comonomers can also be produced by adding other dicarboxylic acids and other dialcohols in order to achieve properties that deviate from pure PET but are useful in some areas.
  • the resulting PET is also referred to as co-PET.
  • PET recyclate hereinafter referred to as rPET or also "Post Consumer Recycling PET” (PCR-PET) is collected, cleaned and granulated or shredded PET or generally any form of PET after the first or multiple use after production in a PET plant .
  • the rPET is preferably largely homogeneous and free of foreign substances through the use of current processing methods.
  • the rPET can be comminuted using common comminution methods, e.g. shredding or grinding, shredded bottle waste is particularly preferred (since this currently accounts for the largest proportion of available rPET in terms of quantity.
  • Below rPET can also be understood as comminuted intermediate product (monomers, oligomers, prepolymers) from PET plants.
  • a depolymerizate or PET depolymerizate is a mixture of > 70% of short-chain PET macromolecules (i.e. monomers with a degree of polymerization of usually 1 to 25 of the PET monomer basic unit C10H8O4), which also contains residues from others May contain monomers, organic or inorganic additives and foreign substances. Other possible monomers can arise from other added dicarboxylic acids such as isophthalic acid or adipic acid or other diols such as diethylene glycol, cyclohexanedimethanol or butanediol. Polyester depolymers then correspond to short-chain macromolecules consisting of any number of different dicarboxylic acids and any number of different diols and polyesters. Depolymers or polyester depolymers are preferably obtained by hydrolysis and glycolysis, or generally by solvolysis of polyesters at elevated process temperatures.
  • a melt can be a pumpable mixture of rPET and depolymer or just consist of a pumpable mixture of depolymer.
  • a typical PET plant according to the prior art for producing PET from the main monomeric starting materials PTA and EG essentially comprises six production stages. Several production stages can be combined in individual reactors.
  • An example is a 2R-PET plant from Uhde Inventa-Fischer for the production of PET for films, fibers or packaging material, for example. All information on process parameters and product properties such as temperatures, pressures, IVs, COOH end group content and degrees of polymerization are guide values. Depending on the recipe and capacity, slight deviations are possible and necessary.
  • PET plants also contain processing stages for reaction products such as water, methanol, EG and other by-products.
  • Stages for processing the polycondensation product into a salable product such as pelletizing devices, in particular strand or underwater pelletizing, can be downstream, or there is a direct connection to spinning machines, preform machines or lines for manufacturing PET films or other PET end products.
  • Conditioning devices and solid phase polycondensations can also be installed downstream to reduce unwanted by-products such as acetaldehyde and to increase the viscosity.
  • the first production stage is simply called the esterification stage (ES stage) because it is mainly the COOH end groups that are esterified with the OH end groups, resulting in water.
  • ES stage esterification stage
  • PTA HOOC-C6H4-COOH
  • EG HO-[CH 2 ] 2 -OH
  • the mixture of the different PET molecules with different end groups from the ES stage is called a monomer, not to be confused with the raw materials PTA and EG, which are also known as monomeric starting materials.
  • PTA and EG which are also known as monomeric starting materials.
  • Short-chain PET molecules are also called oligomers. Since the esterification reactions are equilibrium reactions, the water formed must be removed from the reaction mixture in order to achieve high conversion rates. 100% conversion rate corresponds to complete conversion of all available COOH end groups.
  • the reverse reaction with water is called hydrolysis.
  • the monomer has an average Pn of ca. 4.2 with a residual concentration of COOH end groups of approx. 600 mmol/kg.
  • the intrinsic viscosity (IV) according to ASTM is approx. 0.05-0.10 dl/g.
  • Fig. 1 shows a typical result of GPC analysis of ES-stage monomer.
  • the mean molar mass (Mn) was found to be 802 g/mol. If you now divide Mn by the molecular weight of 192 g/mol of the basic unit (C10H8O4), you get an average degree of polymerization of 4.2.
  • the water resulting from the reaction is drawn off from the ES stage together with a portion of the EG supplied and this mixture of substances is fed to a distillation column with connected water and waste gas treatment for separation.
  • the esterification reaction does not require an additional catalyst because the esterification reactions are autocatalyzed by the acidic H + ions of the terephthalic acid moieties.
  • the second production stage is called post-esterification (also post-ester or PE stage), because there the conversion rate of the esterification is further increased by reducing the pressure to an absolute pressure of approx. 60 kPa and increasing the temperature to approx. 275°C, recognizable on the increase in the average degree of polymerization, an intrinsic viscosity increase to approx. 0.10-0.15 dl/g and the further decrease in the COOH end group concentration to approx. 200 mmol/kg.
  • the absolute pressure of approx. 60 kPa is generated by a vacuum system and the withdrawn amounts of reaction water and released amounts of EG are fed back to a distillation column with connected water and waste gas treatment for separation.
  • the mixture of the different PET molecules from the PE stage is also called a monomer. If you want to distinguish this monomer from the monomer of the ES stage, you can, for example, specify the production stage with or give an indication of the chain length. Typical average chain lengths of this monomer from the PE stage are between 5 and 15.
  • Fig. 2 shows a typical result of GPC analysis of PE-stage monomer.
  • the mean molar mass (Mn) was determined to be 2310 g/mol. If one now divides Mn by the molecular weight of 192 g/mol of the basic unit, one obtains an average degree of polymerization of 12.0.
  • the third production stage is called pre-polymerization, pre-polymerization or also pre-condensation, abbreviated PP stage.
  • the dominant reaction is no longer the esterification of COOH and OH end groups, but the polymerization or polycondensation reaction through transesterification of ester groups with liberation of ethylene glycol.
  • the esterification reaction with the release of water of reaction still takes place to a small extent, recognizable from the further decrease in the COOH end groups.
  • the polycondensation reaction requires a catalyst to achieve useful reaction rates. Proven catalysts are Sb, Ti or Al compounds.
  • the polycondensation requires extremely low pressures, further elevated temperatures and thin diffusion layers in order to be able to draw off the EG formed.
  • the polycondensation reaction is an equilibrium reaction and the reverse reaction with EG is called glycolysis.
  • the consequence of the polycondensation reaction is a further increase in the degree of polymerization with an increase in intrinsic viscosity.
  • the required low pressure is generated by a vacuum system and the removed amounts of EG with traces of water are fed back to a distillation column with attached water and waste gas treatment for separation.
  • a further reduction in the COOH end groups to 60 mmol/kg and an intrinsic viscosity increase to approx. 0.30 dl/g are achieved.
  • Fig. 3 shows a typical result of GPC analysis of PP-stage prepolymer.
  • Mn mean molar mass
  • the fourth stage of production is called polymerisation, polycondensation or final polymerisation (hereinafter referred to as DIS stage).
  • the dominant reaction is the polycondensation reaction through transesterification of ester groups with liberation of EG.
  • the required low pressure is generated by a vacuum system and the withdrawn amount of EG with traces of water is fed back to a distillation column with connected water and waste gas treatment for separation.
  • the required thin diffusion layers are typically generated in special reactors with rotating disks.
  • the reactors required for this are generally called finishers or end polymerizers or specifically DISCAGE® reactors for generating particularly high intrinsic viscosities or particularly high degrees of polymerisation in the polymer melt.
  • the mixture of the different PET molecules from the DIS stage is called a polymer.
  • the fifth production stage is the processing of the polymer melt into solid and uniform granules using strand or underwater pelletizers.
  • the fifth production stage can also be the direct further processing of the polyester melt into staple fibers, films, foils, preforms or other typical PET end products.
  • the sixth production stage includes the post-treatment of the granules to increase the intrinsic viscosity and/or to reduce accompanying substances such as acetaldehyde. Typical designations for the sixth production stage are, for example, post-condensation plant, solid-phase condensation, SSP or conditioning.
  • the device for producing a polyester depolymer (depolymerization unit) consists of several stages. a) Stage 1 includes the storage (silo 90) and feed device (conveyor screw 91) for rPET to the mixing stage (mixing tank 10) with nitrogen inerting 110, b) Stage 2 is the mixing stage (mixing tank 10) for mixing rPET into liquid polyester -Depolymerizate in a template for a feed pump.
  • a water spray system (spray condenser 101) is connected to stage 2 to suppress the vapors drawn off, mainly water and low boilers, with connection to a vacuum unit 100, c) Stage 3 includes the EG dosing (feed option for a depolymerizing agent 20) , d) stage 4 comprises a heat exchanger 80 with possible subsequent coarse filtration 140, e) stage 5 comprises the polyester depolymer storage tank 60, from which the mixing device 10 is operated and the melted excess is discharged into an existing PET plant, optionally with a fine filtration and emergency lowering device.
  • Stage 1 includes the storage and feeding facility for rPET.
  • the stage can include a silo 90 , a dosing screw 91 with a weighing device and a feed chute to the mixing stage 10 .
  • stage 1 can also be present twice or more, in each case specifically tailored to the storage and dosing task of the different types of rPET used.
  • the addition of sufficient nitrogen as an inert gas is preferred in order to minimize possible oxygen input through the rPET.
  • the entrainment of oxygen at high temperatures can lead to fire and explosion hazards in the presence of sufficient amounts of ethylene glycol or other combustible gases.
  • An inherent system safety can be guaranteed with less than 5% by volume of oxygen. If this amount is exceeded, the supply of rPET and ethylene glycol must be stopped immediately. At the temperatures used, even small amounts of oxygen can lead to a significant deterioration in the color that can be achieved. Therefore, the residual oxygen input should preferably be kept below 0.1% by volume.
  • oxygen measuring cells can be installed in the rPET feed and in the exhaust gas from stage 2.
  • the amount of nitrogen required is mainly determined by the amount of rPET fed in and the vacuum required in stage 2 to extract the amounts of water vapor that are produced.
  • a safety valve or a rupture disc or a similar pressure relief option can be provided preferably on the feed shaft and on the level 2 storage tank.
  • a digital optical online incoming inspection of the rPET is advantageous, as is the integration of rPET batch data and quality parameters in the continuous recording and evaluation of the operating data of the entire depolymerization unit.
  • An emergency discharge device on silo 90 is also recommended so that rPET that has already been filled can be discharged outside of the depolymerization unit.
  • the silo 90 is advantageous with an exhaust air filter and with stand, temperature and pressure measurements.
  • the feed chute is advantageously equipped with sight glasses and opening options and with level, temperature and pressure measurements.
  • Stage 2 includes the mixing of non-dried rPET with e.g. Stage 2 also includes a connected spray system 101 for suppression of the extracted vapors (mainly water and other light ends) and a connection to a vacuum system 100.
  • a connected spray system 101 for suppression of the extracted vapors (mainly water and other light ends) and a connection to a vacuum system 100.
  • rPET depolymer jet mixer 131 Large amounts of rPET can be mixed into liquid polyester depolymer with commercially available dynamic mixers or optimized worm pumps or optimized agitators or, most cost-effectively, with a device which utilizes the tendency of rPET to stick to liquid polyester depolymer and utilizes the impact energy rPET falling and/or pressed into these depolymer jets is entrained and mixed by one or more jets of hot, liquid polyester depolymer, referred to below as rPET depolymer jet mixer 131 .
  • Level 2 can advantageously be equipped with sight glasses and manholes, as well as level, temperature and pressure measurements. From stage 2 to stage 5, the depolymerization unit, including the pipes 50, is heated on the shell side. A double-walled design of containers and pipelines is particularly suitable for this, which can then be heated with organic heat transfer media in liquid or preferably vapor form.
  • rPET is mixed into liquid, hot polyester depolymer without significant additional heat input, it must also be noted that the higher thermal energy of the hot polyester depolymer is transferred to the cold rPET (approx. room temperature). As long as the temperature of the hot depolymerizate or the mixture is above the melting point or melting range of the rPET (typically approx. 245-250°C), it will melt rapidly. If the mixing temperature falls below the melting point of the rPET, the rPET remains in a melted but solid state until the common lowest mixing temperature is reached.
  • a melting of rPET particles reduces the size of the rPET particles and leads to a lower required mass ratio of rPET to polyester depolymer for the production of a transportable mixture and reduces frictional losses during transport.
  • the resulting mixing temperature of rPET and polyester depolymer can be calculated approximately using Riechmann's rule of mixtures:
  • the mixing temperature is always above the solidification point or of the solidification range of the mixture remains, in order to be able to rule out system malfunctions or damage caused by this.
  • the solidification range of various polyester-depolymerizate-rPET mixtures at approx. 185 to 195°C was determined experimentally.
  • the following mixing temperatures can be calculated approximately if the specific heat capacity of rPET at 20°C is 1.05 kJ/kg/K and that of polyester depolymer at 270°C is 1.95 kJ/kg/K (CWSmith/ M.Dole, J. Polymer Sci. 20, 1956): Sci. 20, 1956):
  • a minimum mass ratio of rPET to polyester depolymer of 1:1.4 should not be undercut without safety measures in order to avoid unplanned but possible solidification and thus a significant process disruption with possible damage to the plant.
  • the mixing reservoir 60 is advantageously run with a short residence time (2-5 min), so that on the one hand a continuous flow can be guaranteed with commercially available feed pumps 120 and on the other hand the temperature drop is as small as possible until the heat exchanger stage is heated up again.
  • a short residence time is reflected both in small container sizes and, associated with this, in low investment costs as well as in improved product quality through the lowest possible thermal stress over time.
  • the total residence time of the depolymerization unit and the general temperature profile of the process are similar to the conditions to which monomers or prepolymers are typically exposed in PET plants.
  • the process can be further optimized with the operating parameter mass ratio of rPET to polyester depolymer in combination with the temperatures achieved and set, with the design of the heat exchanger and with the minimum required EG ratio.
  • PET or rPET is highly hygroscopic and usually contains 0.1-0.4 wt% water. If undried rPET comes into contact with hot polyester depolymerization product, most of the water contained will evaporate in mixing stage 10 at 270°C and a small part of the water will hydrolyze the rPET. The long-chain PET molecules are randomly split, the degree of polymerization decreases and new COOH end groups are generated. In addition, any unwanted low boilers (impurities) that may be present in the rPET will also evaporate or be entrained with the evaporating water.
  • impurities impurities
  • the average molar mass (Mn) of an example where rPET flakes were dissolved in polyester depolymer was found to be 1290 g/mol. If one now divides Mn by the molecular weight of 192 g/mol of the basic unit, one obtains an average degree of polymerization of 6.7.
  • the low chain length or viscosity is the basis for good flowability and a low melting point of the polyester depolymer-rPET mixture.
  • the average molar mass that results from hydrolysis depends heavily on how much water is hygroscopically bound in the rPET or how much water is added in total with the rPET. In addition, the extent of hydrolysis is influenced by how much of the water supplied reacts with the rPET, this is also influenced by the system design and mode of operation.
  • a negative pressure can be generated in the mixing stage in a targeted manner, which removes the water vapors and other low boilers and excess nitrogen that are produced from the mixing stage.
  • the negative pressure can be set in such a way that no water vapor or low boilers can get back through the feed line into the rPET feed and into the silo.
  • the spray condenser 101 is preferably connected to a collection container 102, as is customary in the prior art.
  • the collection container 102 has a feed pump 103 with a connected filter 104 for filtration and a subsequent heat exchanger 105 for sufficient cooling of the water circuit on the ground.
  • the excess water with any low boilers can then be fed, for example, to the waste water treatment stage 106 of a connected PET plant or to a separate waste water treatment stage.
  • FIG. 1 A possible embodiment of the mixing device 130 in the form of a rPET depolymerizate jet mixer 131 is shown in FIG Polyester depolymer is pressed and sprayed. The sprayed polyester depolymer contacts the rPET falling into the mixing tank 10 .
  • the rPET feed 11, 133 is advantageously designed as a vertical round, square or rectangular feed line.
  • the diameter selected is at least large enough for the entire amount of rPET to be fed in in free fall without any disruption. Additional nitrogen feeds can help to intensify the feed of the rPET and build up counter-pressure to the water vapor that forms when the undried rPET is mixed into the hot polyester depolymer.
  • the size of the arrangement of the two flat jet nozzles 132 is to be designed according to the diameter of the rPET supply line, so that all the rPET can hit the flat jets in free fall. The speed of the two flat jets must be high enough to absorb the volume flow of rPET.
  • the rPET volume flow that can be absorbed by the polyester depolymer jets results from the average layer thickness of rPET recorded on the polyester depolymer jets multiplied by the width of the polyester depolymer jets on which the rPET can fall and multiplied by the speed of the Polyester depolymerizate blasting:
  • V' h * b * v
  • the resulting average layer thickness of rPET on the polyester depolymer jets is positively favored by the high mutual sticking tendency of rPET and hot, liquid polyester depolymer. Also positive due to the weight of a rPET column standing on the polyester depolymer beams. Adding nitrogen to the feed chute can increase the pressure when mixing the rPET into the polyester depolymer if the pressure drop across the feed screw is higher. It is also possible to press the rPET into the polyester depolymer jet(s) in a targeted manner via a screw feeder 101 .
  • the crossed and downward spray direction dictates the direction of the mixture together with the downward gravitational force.
  • An advantageous embodiment is the downward inclination of the flat nozzles 132 at 45°.
  • the selected slit height specifies the maximum permitted size of solid insoluble components in the rPET or the minimum coarse filtration fineness required for this.
  • v V'/A
  • v velocity of the polyester depolymerization jets in m/s
  • V' rPET volume flow in m 3 /s
  • A nozzle exit area (slot width in m x slot height in m)
  • the slot exit area together with the inlet geometry of the nozzles 132, determines the drop in pressure across the nozzles 132, which must be applied by the pump from the polyester depolymer storage tank to the second stage.
  • the slot dies 132 are easily interchangeable to attach to the unit to accommodate different capacities and grades of rPET. It is also advantageous to use robust and low-wear materials such as hardened stainless steel for the nozzles 132 .
  • Stage 3 includes the addition via the feed option for a depolymerizing agent 20, in particular a diol (EG in the example) in the smallest possible amounts, less than or equal to 0.1, preferably less than 0.05, particularly preferably less than 0.01 kg of EG per 1 kg of rPET after the hydrolysis has taken place and a lower viscosity or lower degree of polymerization is already present than was originally present in the rPET.
  • a depolymerizing agent 20 in particular a diol (EG in the example) in the smallest possible amounts, less than or equal to 0.1, preferably less than 0.05, particularly preferably less than 0.01 kg of EG per 1 kg of rPET after the hydrolysis has taken place and a lower viscosity or lower degree of polymerization is already present than was originally present in the rPET.
  • the addition of EG only serves to further reduce the degree of polymerization, but mainly serves to control the esterification of the COOH end groups so that the subsequent repolymerization
  • the reaction of the EG with the rPET/polyester depolymer mixture preferably takes place at high process temperatures through esterification reactions within a few minutes.
  • the pressure that has arisen as a result of the evaporation of the EG in the hot polyester depolymer also decreases again, at 270°C max. approx. 6.4 bar absolute.
  • the required EG can be obtained from a suitable pick-up point from a PET plant be removed.
  • a sampling point may be provided before and/or after EG interference.
  • a suitable mixing section (mixer 70) with a short residence time can be connected after injection into one or preferably more injection points, the mixing section not containing the not yet melted rPET or contained impurities may impede the passage.
  • Level 3 can advantageously be equipped with flow, temperature and pressure measurements.
  • Stage 4 includes a heat exchanger 80, with which the necessary melting energy for the rPET can be provided.
  • the heat exchanger 80 can be designed cost-effectively as a tube bundle heat exchanger, since the low viscosity of polyester depolymer allows good heat transfer.
  • the dimensioning of the heat exchanger is determined by the minimum required residence time and the amount of energy supplied per unit of time. The minimum residence time required results from the time required to heat the rPET/polyester depolymer mixture back to approx. 270°C plus the melting time in which the remaining unmelted rPET melts. At 270°C, rPET dissolves completely within approx. 5 to 10 minutes if sufficient heat is applied.
  • Intensive mixing during flow can be achieved, for example, by using tubes with an irregular surface (e.g. dents), especially when using such tubes in the heat exchanger.
  • the mixture can also be partially and briefly overheated.
  • a sampling valve can be installed after the heat exchanger.
  • the heat required to melt the rPET is supplied by the heat exchanger, the rest of the unit is trace heated.
  • the released heat output of the esterification stage (due to the reduction of added PTA and EG to the proportion of added rPET) can be taken directly in the form of liquid, hot, organic heat transfer oils for the operation of the heat exchanger 80.
  • a separate heating stage can also be used if the heat exchanger 80 is to be operated with particularly high heating medium temperatures, for example 320° C. or higher, in order to keep the required heating surface area as small as possible.
  • Stage 4 can advantageously be equipped with viscosity, temperature and pressure measurements.
  • the heat exchanger 80 can advantageously be designed in several stages in order to control the heat input that is required in different ways for different capacities. Each stage can have a different geometry, heating temperature and heating surface and can therefore be heated individually.
  • the first internal heat exchanger stage after stage 3 has the highest heating temperature and possibly the largest heating surface, and the last internal heat exchanger stage before stage 5 has the lowest heating temperature.
  • a coarse filter 140 can now be installed downstream of the heat exchanger 80 .
  • the filtration rating 140 must be finer than the slit width of the nozzles used.
  • Stage 5 includes a container (polyester depolymer storage container 60) in which the melted mixture of rPET and polyester depolymer heated to about 270° C. coming from the heat exchanger 80 is expanded and temporarily stored with a minimum residence time.
  • Stage 2 is supplied from the polyester depolymer reservoir 60 with a feed pump 120 customary for this purpose.
  • the flow rate of this pump 120 determines or controls the maximum permitted supply quantity of rPET in relation to the minimum required mixing ratio according to the volumetrically required ratio, safety distance from the solidification temperature and shape or consistency of the rPET.
  • the polyester depolymer excess caused by the melting zen of the rPET and recognizable by the steady rise in the level in the depolymer storage tank in continuous operation is separated via the switch 30 and the outlet 40 and conveyed with a further pump 120 to a possibly connected PET plant.
  • Further filtration stages or cleaning stages 140 for example a fine filter, can be added to the process flow.
  • This pump 120 can advantageously be set up at the lowest point of the depolymerization unit, so that when the unit is switched off, it can be emptied of the lowest point and residues.
  • the excess polyester depolymer is fed into the stage of the connected PET plant that corresponds to the degree of polymerisation achieved, for example directly into the PP stage.
  • the sampling points can be used to detect contamination that is dangerous for the product quality at an early stage, either visually or with optical measuring methods.
  • an emptying option for the entire depolymerization unit can be provided. It can be emptied, for example, into waste trucks with a capacity of about 1 m 3 , into which about 200 liters of water are filled before filling. The resulting water vapors are sucked off and released into the open air. The polyester depolymerizate then has to cool down in the refuse truck for further use. The short residence times and thus the polyester depolymer volumes of the depolymerization unit limit the waste produced to a minimum. The possibly connected PET production plant with larger capacities and longer residence times is thus largely spared from contamination. In addition, the faulty batch must then be removed from the rPET feed silo 90 before regular operation can be resumed.
  • the polyester depolymer storage tank 60 can in particular also be used to start up the plant. Hot, liquid monomer or prepolymer can be removed from an optionally connected PET system until the depolymerization unit is filled and the cycle process can be started. The addition of rPET is then started, the polyester depolymer is produced and the excess polyester depolymer is transported to the PET plant.
  • Stage 5 is preferably connected to the vacuum stage of the post-esterification stage of the PET plant that may be connected. This allows a slight negative pressure to be generated in the monomer storage container and any remaining low boilers or small amounts of ethylene glycol released can be drawn off and processed.
  • Level 5 can advantageously be equipped with sight glasses and manholes, as well as level, temperature and pressure measurements and nitrogen inerting.
  • GPC Gel Permeation Chromatography
  • Mn represents the number-average molar mass and indicates the average molar mass of a polymer sample. Dividing Mn by the molecular weight of the monomeric repeat unit of the polymer gives the average number of monomeric repeat units, also called the degree of polymerization (Pn).
  • HFI P hexafluoroisopropanol
  • KTFAC potassium trifluoroacetate
  • the average molar mass values and their distribution are calculated using the computer-aided strip method based on the PMMA calibration curve.
  • the molar masses determined are not absolute molar masses but PMMA-equivalent molar masses.
  • the determination of the intrinsic viscosity is also called the determination of the relative solution viscosity and is a standard method in quality control in PET production.
  • the determined intrinsic viscosities correlate with the degree of polymerization and the average molecular weight.
  • the intrinsic viscosity is determined in accordance with ASTM 4603-03 (2003) on a 0.5% by weight sample solution in a mixture of 6 parts by weight phenol and 4 parts by weight 1,1,2,2-tetrachloroethane by determining the flow times of the solvent mixture and solution in an Ubbelohde capillary viscometer DIN type Ia (capillary diameter 0.95 mm) at 30°C.
  • the determination of the COOH end groups is also called determination of the carboxyl end groups and is a standard method in quality control in PET production.
  • the COOH end groups are determined in accordance with ASTM D7409-15 by dissolving 0.25-0.5 g polyester at 80° C. in 15 mL o-cresol and then diluting it with 60 mL dichloromethane by titration with a 0.01 normal solution of KOH in methanol by determining the transition point of the added indicator tetrabromophenol blue using an automatic titrator with a connected optical sensor.
  • Vs volume of KOH solution required for titration of the sample
  • Vb Volume of KOH solution required for titration of the solvent mixture (blank value)
  • a heatable 5L autoclave with a stirrer was available as a test apparatus.
  • the heating takes place with an organic heat transfer oil (Marlotherm SH) with a heating capacity of 4 kW.
  • the autoclave can be pressurized with nitrogen.
  • the stirrer is specially designed for low and high-viscosity PET products and, thanks to highly efficient surface renewal, PET Produce viscosities under suitable vacuum and temperature conditions up to 1500 Pas dynamic viscosity, which corresponds approximately to an IV of 0.85 dl/g at 275°C.
  • Two capacitors are connected in series to the autoclave.
  • the first condenser serves as a simple separation stage for mixtures of substances, for example to keep ethylene glycol in the reactor and to allow the water that forms to escape.
  • the second condenser then condenses all extracted gases according to the cooling medium temperature used.
  • a vacuum pump can be connected after the condensers in order to enable the necessary vacuum for a polycondensation of monomer to polymer.
  • a cold trap operated with cryogenic, liquid nitrogen can be placed in front of the pump.
  • the heating autoclave wall
  • the heating temperature was 262°C after 10 minutes, the product temperature (mixture of melted and undissolved flakes) was only 196°C.
  • the heating temperature had risen to 300°C and the product temperature at 254°C was already above the typical melting range of flakes at 245-251°C.
  • the fact that the flakes had already largely melted by this point is also indicated by the torque at 50 rpm, which has fallen sharply to 0.2-0.3 Nm.
  • a polycondensation of the resulting depolymer was then carried out in an autoclave at about 270° C. and 0.7 mbar. No additional catalysts or other additives or auxiliaries were added. As the viscosity increased, the speed of the stirrer was reduced from 150 to 50 to 10 rpm. Within 1.75 hours the viscosity increased quite linearly from 0.158 to 0.492 to 0.626 to 0.918 dl/g.
  • the heating was then stopped for an adiabatic mode of operation and a further 500 g of granules were added through the open sampling opening. After the addition, the sampling opening remained open so that the further melting process could be observed visually.
  • a polycondensation of the resulting depolymer was then carried out in an autoclave at about 270° C. and 0.7 mbar. No additional catalysts or other additives or auxiliaries were added. As the viscosity increased, the speed of the stirrer was reduced from 150 to 50 to 10 rpm. Within 1.5 hours the intrinsic viscosity increased from 0.087 to 0.203 to 0.407 to 0.570 to 0.672 to 0.787 to 0.886 dl/g.
  • the heating temperature was constant at 290° C. and the product temperature was 223° C., and the first distillate dripped back from condenser 1, which indicates the start of the esterification reaction. 110 min later, the accumulation of distillate from condenser 2 stopped, the esterification reaction was complete and the product temperature was 264°C. Now the heating temperature was set to 325°C and condenser 1 to 210°C. 15 min later the heater temperature was 325°C, the product temperature was 295°C and the condenser 2 temperature was 210°C.
  • the heating temperature was now set to a target of 200°C and both the heating and the product temperature began to fall steadily. 40 minutes later the heater temperature had dropped to 202°C and the product temperature to 194°C. At this point the melt became cloudy and the torque from the stirrer began to increase, whereas before it had always indicated a constant 0.4 Nm. A further 6 minutes later, at a product temperature of 184° C., the depolymer had solidified as a whole and was circulated as a block by the stirrer. This was possible because the stirrer is extremely powerful and the solidified depolymer easily disintegrates.
  • Example 4 The procedure was as in Example 4, but 2000 g of flakes were stirred into the produced low molecular weight PET of about 1000 g and dissolved within 12 minutes.
  • the flakes dissolved within 15 minutes from the beginning of the addition, but with brief increases in torque up to 2 Nm. After the flakes had melted, a stable torque of 0.35 Nm was restored.
  • the heating temperature was now set to a target of 200°C and both the heating and the product temperature began to fall steadily. 32 minutes later, the heating temperature had dropped to 203° C. and the product temperature to 196° C., and the depolymer suddenly solidified as a whole.

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Abstract

Le recyclage du PET (la valorisation des déchets de polyéthylène téréphtalate) se pratique depuis plusieurs dizaines d'années déjà de manières très diverses, étant donné que le PET est disponible en grandes quantités. Cependant, la protection de l'environnement et l'exploitation durable des ressources imposent des taux de recyclage qui ne cesseront d'augmenter au cours des prochaines décennies. Afin de parvenir à une économie circulaire, il faudra tôt ou tard que ce taux finisse par atteindre les 100 %.
EP22813935.8A 2021-11-11 2022-11-03 Dispositif et procédé pour la fabrication d'un dépolymère de polyester ainsi que dispositif et procédé pour la fabrication d'un polyester Pending EP4429809A2 (fr)

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DE102021212695.2A DE102021212695A1 (de) 2021-11-11 2021-11-11 Vorrichtung und verfahren zur herstellung eines polyester-depolymerisats sowie vorrichtung und verfahren zur herstellung eines polyesters
PCT/EP2022/080689 WO2023083692A2 (fr) 2021-11-11 2022-11-03 Dispositif et procédé pour la fabrication d'un dépolymère de polyester ainsi que dispositif et procédé pour la fabrication d'un polyester

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CN107459788B (zh) * 2017-07-20 2019-05-24 东华大学 一种聚酯回收料的再生利用方法
DE102018202547A1 (de) 2018-02-20 2019-10-02 Thyssenkrupp Ag Vorrichtung und Verfahren zum Einmischen von Recyclingmaterial in eine Polyesterschmelze
WO2020149798A1 (fr) 2019-01-15 2020-07-23 Köksan Pet Ve Plasti̇k Ambalaj Sanayi̇ Ve Ti̇caret Anoni̇m Şi̇rketi̇ Procédé de glycolyse chimique dans lequel des déchets de pet transparents sont recyclés pour être utilisés dans la production de résine pet de qualité bouteille
FR3092324B1 (fr) * 2019-02-01 2021-04-23 Ifp Energies Now Procédé de production d’un polyester téréphtalate intégrant un procédé de dépolymérisation
US11518865B2 (en) * 2019-05-20 2022-12-06 Octal Saoc Fzc Process for reclamation of polyester by reactor addition
FR3106134B1 (fr) * 2020-01-09 2022-12-16 Ifp Energies Now Procédé optimisé de dépolymérisation par glycolyse d’un polyester comprenant du polyéthylène téréphtalate
EP3875523A1 (fr) * 2020-03-03 2021-09-08 UAB Neo Group Procédés de recyclage de polyéthylène téréphtalate
CN115380066A (zh) * 2020-04-13 2022-11-22 伊士曼化工公司 化学回收来自各种来源的废塑料包括湿细料

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WO2023083692A2 (fr) 2023-05-19
WO2023083692A3 (fr) 2023-07-20
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MX2024005605A (es) 2024-05-22
CN118215535A (zh) 2024-06-18

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