Process for depolymerization of polyalkylene terephthalates in an extruder.

Abstract

The present invention relates to a process for the depolymerization of at least one polymer P1, which is a polyalkylene terephthalate, i.e., a polymer containing terephthalic acid units and alkylene glycol units, in particular polyethylene terephthalate (PET) or polybutylene terephthalate (PBT). This process is particularly suitable for the depolymerization and recycling of PET-containing waste. The process is carried out in an extruder E having at least two barrels G1, G2, in which at least one polymer P1 is provided in barrel G1 in the form of a suspension S1 in a polyolefin PO, such as polyethylene PE or polypropylene PP. The suspension S1 is then conveyed to barrel G2. At least one glycol compound G, preferably ethylene glycol, and at least one alkali metal alkoxide are introduced into barrel G2 and mixed with the suspension S1. The at least one glycol compound G reacts with the at least one polymer P1 in the suspension S1 to form a mixture M containing the corresponding cleavage products P2. G2 The resulting mixture M G2 is the product outlet E of extruder E X and removed there. This process avoids uncontrolled increases in temperature and pressure during the depolymerization of polymer P1, making it a safer process mode.

Description

[Technical Field]

[0001] The present invention relates to a process for the depolymerization of at least one polymer P1, which is a polyalkylene terephthalate, i.e., a polymer containing terephthalic acid units and alkylene glycol units, in particular polyethylene terephthalate (PET) or polybutylene terephthalate (PBT). This process is particularly suitable for the depolymerization and recycling of PET-containing waste.

[0002] The process is carried out in an extruder E having at least two barrels G1, G2, in which at least one polymer P1 is provided in barrel G1 in the form of a suspension S1 in a polyolefin PO, such as polyethylene PE or polypropylene PP. The suspension S1 is then conveyed to barrel G2. At least one glycol compound G, preferably ethylene glycol, and at least one alkali metal alkoxide are introduced into barrel G2 and mixed with the suspension S1. The at least one glycol compound G reacts with the at least one polymer P1 in the suspension S1 to form a mixture M containing the corresponding cleavage products P2. G2 The resulting mixture M G2 is the product outlet E of extruder E X and removed there.

[0003] This process avoids uncontrolled increases in temperature and pressure during the depolymerization of polymer P1, making it a safer process mode. [Background technology]

[0004] Polyethylene terephthalate (PET) is one of the most important plastics, used in textile fibers, as films, and as a material for plastic bottles. In 2007 alone, approximately 10 7(F. Bockler, B. Dill, G. Eisenbrand, F. Faupel, B. Fugmann, T. Gamse, R. Matissek, G. Pohnert, A. Ruhling, S. Schmidt, G. Sprenger, ROMPP [Online], Stuttgart, Georg Thieme W. Caseri, Polyethylenterephthalate, RD-16-03258 (2009) in Verlag, January 2022).

[0005] PET constitutes one of the greatest current environmental problems due to its persistence and the amount of waste derived from it. Similar problems exist for other polyalkylene terephthalates similar to PET, such as polybutylene terephthalate ("PBT").

[0006] The solution to this problem lies in avoiding and efficiently reusing these plastics.

[0007] The prior art has proposed several processes for the cleavage of PET.

[0008] British Patent Application Publication No. 784,248(A) describes the methanolysis of PET.

[0009] Hydrolysis processes for the depolymerization of PET are described in JP 2000-309663(A), U.S. Pat. No. 4,355,175(A) and by T. Yoshioka, N. Okayama, A. Okuwaki, Ind. Eng. Chem. Res. 1998, 37, 336-340.

[0010] The reaction of PET with glycol compounds is described in U.S. Pat. No. 3,884,850, European Patent Application Publication No. 0 723 951 A1, U.S. Pat. No. 3,222,299 A, WO 2020 / 002999 A2, S.R. Shukla, A.M. Harad, Journal of Applied Polymer Science 2005, 97, 513-517 (hereinafter "Shukla & Harad") and N.D.P. Ingale, S.R. Shukla, European Polymer Journal 2008, 44, 4151-4156.

[0011] Shukla & Harad state that glycolysis of PET forms bis(2-hydroxyethyl) terephthalate (BHET), which can simultaneously be used as a reactant to produce new PET.

[0012] S. Ugduler, KM Van Geem, R. Denolf, M. Roosen, N. Mys, K. Ragaert, S. De Meester, Green Chem. 2020, 22, 5376-5394 ("Ugduler et al.") investigate the aqueous alkaline hydrolysis of PET waste to yield ethylene glycol and terephthalic acid (TS), specifically the effect of certain reaction parameters, such as temperature and ethanol / water ratio, on the depolymerization rate. Ugduler et al. also discuss the issue of contamination of the PET starting material with additional polymers, such as low-melting-point polyolefins (hereafter abbreviated as "PO").

[0013] In addition to these processes, there are numerous processes in which PET-containing waste is split in an extruder and then post-processed.

[0014] US Patent No. 5,545,746(A) describes the depolymerization of PET waste in an extruder to obtain ethylene glycol and TS.

[0015] L. Biermann, E. Brepohl, C. Eichert, M. Paschetag, M. Watts, S. Scholl, Green Process. Synth. 2021, 10, 361-373 ("Biermann et al."), referring to U.S. Pat. No. 5,545,746(A) and WO 2020 / 053051(A1), describe the hydrolysis of mixed waste (PET / PE) to obtain ethylene glycol and terephthalic acid (="TS") in a twin-screw extruder using solid sodium hydroxide.

[0016] WO 2020 / 053051 A1 describes in detail the saponification, i.e., hydrolysis, of PET using alkali metal hydroxides or alkaline earth metal hydroxides (page 8, line 1 of WO 2020 / 053051 A1), in which the ethylene glycol solvent is additionally provided to the reaction mixture as a separate stream from the alkali metal hydroxide / alkaline earth metal hydroxide stream (see Figure 1 of WO 2020 / 053051 A1; Example 2, page 19, lines 25-28; Example 4, page 20, lines 27-28). Biermann et al. also disclose the saponification of PET.

[0017] M.A. Mohsin, T. Abdulrehman, Y. Haik, Int. J. Chem. Eng. 2017, 5361251 ("Mohsin et al.") describes the reaction of molten PET with ethylene glycol in an extruder. However, Mohsin et al. do not describe the use of ethylene glycolate or the presence of an additional polymer in the PET.

[0018] B. Bergmann, W. Becker, J. Diemert, P. Elsner, Macromol. Symp. 2013, 333, 138-141 ("Bergmann et al.") describes the reaction of molten PET with ethylene glycol in an extruder and the analysis of the extruded product by near-infrared spectroscopy. The reaction regime is the same as that described by Mohsin et al.

[0019] U. Thiele presented a corresponding process for PET decomposition in an extruder in the context of an overview of various processes for PET depolymerization at the "5th China International Recycled Polyester Forum" held in Shanghai, China, September 2-4, 2009. The corresponding presentation is available at http: / / www.ccfei.net / upfile / conference / 200909181532368708140.pdf ("Thiele") (last accessed January 15, 2023).

[0020] J.D. Patterson, in his paper "Continuous Depolymerization of Poly(ethylene terephthalate) via Reactive Extrusion," p. 60ff (North Carolina State University, March 28, 2007, available at https: / / repository.lib.ncsu.edu / bitstream / handle / 1840.16 / 3783 / etd.pdf?sequence=1; "Patterson," last accessed January 15, 2023), discloses a process for PET decomposition in an extruder, which also uses ethylene glycol but not ethylene glycolate. Patterson also cites a paper by G. Colomines, F. Rivas, M.-L. Lacoste, and J.-J. Robin, Macromolecular Materials and Engineering 2005, 290, 710-720 ("Colomines et al."), which describes the decomposition of PET with diethylene glycol and the use of the reaction product in polyurethane formulations.

[0021] M. Dannoux, P. Cassagnau, A. Michel, Can J Chem Eng 2002, 80, 1075-1082, describe the alcoholysis of PET in an extruder using dibutyltin oxide as catalyst.

[0022] U.S. Patent No. 3,884,850 describes a system for the depolymerization of PET in which PET is converted to BHET and low molecular weight oligomers of BHET. This process does not take place in an extruder.

[0023] The decomposition of polyesters, such as PET, in equipment typical for polymer processing, e.g., extruders, is typically carried out at temperatures above the melting temperature of the polyester in order to plasticize the material. However, the decomposition of polyalkylene terephthalates, particularly PET, presents a problem in that their melting temperatures exceed the boiling point of ethylene glycol.

[0024] The vapor pressure of glycol compounds generated during glycolysis leads to reactor pulsation and unstable operating conditions, so that only very small amounts of glycol compounds can be used, which leads to the formation of oligomeric melts with relatively high viscosities, or the extruder must be operated with pressure maintenance means to compensate for the vapor pressure of glycol compounds, especially ethylene glycol.

[0025] This drawback is particularly important when cleaving polyalkylene terephthalates, especially PET and PBT, to give the corresponding cleavage products, such as BHET, because this reaction is typically carried out with a large excess of ethylene glycol, often with the addition of a catalyst such as ethylene glycolate or an alkoxide of a monohydric C1-C6-alkyl alcohol.

[0026] The object of the present invention was therefore to provide an efficient process for the depolymerization of polyalkylene terephthalates, in particular PET and PBT, in an extruder, which does not have the above-mentioned drawbacks and ensures a safe process mode, in particular without pressure spikes, and which ensures these advantages, in particular in glycolytic depolymerization.

[0027] Summary of the Invention It has now surprisingly been found that the depolymerization of polyalkylene terephthalates in an extruder using glycol compounds can be carried out without the above-mentioned drawbacks (heterogeneous process mode, increased pressure spikes) if the associated polyester is used in the form of a suspension in which the polyester is present as a solid phase and the polyolefin PO is used as a continuous liquid phase. [Brief explanation of the drawings]

[0028] [Figure 1]1 shows an embodiment of the process according to the invention, which is shown in FIG. <31> and G2 <32> and product exit EX <33> and extruder E <3> Extruder E <3> is a twin-screw extruder, each barrel G1 <31> and G2 <32> is the screw element <91> , <92> PET particles (PPar) <41> and polyolefin PO <2> , preferably polyethylene (= "PE") G1 <31> 2, material flow <11> and material flow <21> G1 <31> The temperature of PO <2> is in liquid state, PET <1> The screw element is adjusted so that the <91> The mixing and kneading function of PO <2> There are PET particles in it. <41> The continuous phase PKon is suspended <42> PET <1> Particle PPar <41> In the form of barrel G1 <31> If the PET starting material is used in unground form, it is introduced into barrel G1 <31> To ensure sufficient grinding within the barrel, <31> Use additional fracture elements within the particle P <41> This can be further crushed. <1> can also be introduced with larger fragments, then barrel G1 <31> Optionally, suitable grinding elements may be used to grind the desired PET particles. <41> The resulting suspension S1 <4> PKon <42> PET particles in PPar <41> The screw elements are <91> At the same time, S1 <4> is the screw element <91> By Barrel G2 <32> In the direction of the product outlet EX <33> The barrel G2 is conveyed (or "transported") in the direction of ("downstream"). <32> In S1 <4> The ethylene glycol flow <5> and a stream of a 30 wt % solution of sodium methoxide in methanol (solid sodium methoxide can be used instead). <6> Mixed with barrel G1 <31> Suspension S1 <4> ethylene glycol, sodium methoxide, and methanol content is elevated compared to PET <1> Suspension S1 containing <7> Suspension <7> Extruder E <3> When passing through the mixture MG2 <8> is converted toPET <1> is reacted with ethylene glycol in a methoxide-catalyzed cleavage reaction to give the product BHET <43> and oligomers of BHET <44> In this way, a mixture MG2 containing BHET, BHET oligomers, PO, and ethylene glycol is obtained. <8> However, product exit EX <33> Barrel G2 <32> Inside PET <1> In an embodiment of the present invention in which the cleavage reaction of MG2 <8> still has a certain percentage of PET <1> Including G1 <31> PET particles <41> Inactive phase PKon <42> It is provided in a suspended state in PET. <1> Glycolysis can proceed in a controlled manner, avoiding pressure and temperature spikes during the process. [Figure 2] 1 shows a further embodiment of the process according to the invention, which corresponds to the embodiment shown in FIG. 1, with the following differences: PET <1> and P.O. <2> But mixed flow <12> Barrel G1 <31> This embodiment is particularly advantageous in that the process according to the invention is <2> PET coated with polyethylene PE or polypropylene PP. <1> This is relevant when a mixture of glycol and sodium methoxide is used for depolymerization and recycling of the mixed stream. <56> Barrel G2 <32> Sodium methoxide is typically dissolved in glycol as a powder, and the resulting mixture is then poured into a stream. <56> Used as. [Figure 3]1 shows a further embodiment of the process according to the invention, which corresponds to the embodiment shown in FIG. 2, with the following differences: extruder E <3> but additional screw elements <95> With additional barrel G3 <35> A mixture of ethylene glycol and sodium methoxide is <56> Barrel G2 <32> Once supplied to the resulting suspension S1 <7> But barrel G2 <32> From Barrel G3 <35> In this embodiment, the suspension S1 <7> PET inside <1> reacts with glycol and methoxide to form mixture MG2 <8> The majority of the reactions are from the G3 barrel. <35> Part of the reaction takes place in the form of a pre-reaction in barrel G2 <32> Two barrels G2 <32> and G3 <35> Control the reaction within each barrel G2 <32> and G3 <35> This is done by adjusting the appropriate conditions (temperature) within the container. DETAILED DESCRIPTION OF THE INVENTION

[0029] The process according to the invention is a process for the depolymerization of at least one polymer P1.

[0030] The compounds BHET, MHET and TS referred to in the context of the present invention have the following structures: [ka] "MHET" also encompasses the corresponding carboxylate of the structure shown. "TS" also encompasses the corresponding mono- and dicarboxylates of the structure shown.

[0031] 1. Polymer P1 The at least one polymer P1 has n1 units of the following structural formula (I): [ka] The compound comprises interconnected repeating units of a is an integer of 2≦a≦6, in particular a=2 or 4, preferably a=2. b is an integer of 2≦b≦6, in particular b=2 or 4, preferably b=2. c is an integer of 0≦c≦10, in particular c=0 or 1, preferably c=0. n1 is an integer equal to or greater than 50.

[0032] The n1 interconnected repeating units of structural formula (I) contained in polymer P1 may be identical or different, in particular identical.

[0033] The n interconnected repeat units of structural formula (I) are interconnected within polymer P1 such that the bond labeled "(i)" of one repeat unit of structural formula (I) is connected to the bond labeled "(ii)" of an adjacent repeat unit of structural formula (I).

[0034] The process according to the invention is particularly suitable for the depolymerization of polymers P1 which at least partially comprise segments of polyethylene terephthalate (“PET”; option (β) below) or segments of polybutylene terephthalate (“PBT”; option (α) below).

[0035] Therefore, one of the following embodiments (α) and (β) is preferred, with (β) being more preferred. (α) Polymer P1 comprises n1 interconnected repeating units of structural formula (I), where a=4 and c=0. (β) Polymer P1 comprises n1 interconnected repeating units of structural formula (I), where a=2 and c=0.

[0036] The end group of the first repeating unit of the n1 interconnected repeating units of polymer P1 (present for said unit in structural formula (I) at the bond defined in "(i)") and the end group of the n1 th repeating unit of the n1 interconnected repeating units of polymer P1 (present for said unit in structural formula (I) at the bond defined in "(ii)") are not particularly limited and are a result of the method used in the production of polymer P1.

[0037] These end groups may be terminal fragments of the repeating units of structural formula (I) or may be end fragments of one or more repeating units W X W X is different from structural formula (I).

[0038] At least one of these two end groups is -H, -OH, optionally at least one group selected from aliphatic groups containing -OH, -O- (in particular, optionally at least one group selected from alkyl groups containing -OH, -O-), aromatic groups (e.g., in particular the isophthalic acid group of structural formula (VII) below); -heteroaromatic group It is preferably selected from:

[0039] At least one, and more preferably both, of these end groups are -H, -OH, optionally at least one group selected from alkyl groups, including -OH, -O-, - an isophthalic acid group of structural formula (VII) described below It is even more preferred to select from:

[0040] The terminal group connected to the bond labeled "(i)" in structural formula (I) is -H, -(CH2) a* -[O-(CH2) b* ] c* More preferably, it is selected from —OH. a* is an integer of 2≦a*≦6, in particular a*=2 or 4, preferably a*=2. b* is an integer of 2≦b*≦6, in particular b*=2 or 4, preferably b*=2. c* is an integer of 0≦c*≦10, particularly c*=0 or 1, preferably c*=0.

[0041] Notwithstanding this, the terminal group connected to the bond labeled "(ii)" in Structural Formula (I) is preferably selected from the group consisting of -H, -OH, and a group of Structural Formula (IV) or (VII), more preferably from the group consisting of -H, -OH, and a group of Structural Formula (IV), and even more preferably from the group consisting of -OH and a group of Structural Formula (IV), wherein Structural Formulas (IV) and (VII) are as follows: [ka]

[0042] Thus, the process according to the invention involves the addition of n interconnected repeating units of structural formula (I) to further repeating units W Y This is the case, for example, in particular for polymers P1 comprising comonomer units such as repeating units of formula (VI) described below, where a, b, c have the above definitions. [ka]

[0043] Thus, polymer P1 according to the present invention includes any polymer comprising at least one segment A1 consisting of n1 interconnected repeat units of structural formula (I), which may be identical or different, preferably identical, within segment A1, and wherein the n1 interconnected repeat units of structural formula (I) are interconnected within segment A1 such that the bond labeled "(i)" of one repeat unit of structural formula (I) is connected to the bond labeled "(ii)" of an adjacent repeat unit of structural formula (I).

[0044] In addition to the n1 interconnected repeating units of structural formula (I), the polymer P1 may also contain additional groups G that are not composed of repeating units of structural formula (I). F , preferably an organic group G F For example, a repeating unit W different from structural formula (I) may be included. Z The polymer may comprise an oligomeric or polymeric segment consisting of:

[0045] For example, a segment A1 composed of n interconnected repeating units of structural formula (I) may then be connected to such an organic group G in polymer P1 via bond (i) of the first repeating unit of the n interconnected repeating units of structural formula (I) of segment A1 and / or via bond (ii) of the nth repeating unit of the n interconnected repeating units of structural formula (I) of segment A1. F can be linked with

[0046] Similarly, polymer P1 may also comprise two or more segments A1, A2, etc., each of which is composed of n1 interconnected repeating units of structural formula (I) and which contain an organic group G different from structural formula (I). F , for example, a repeating unit W different from structural formula (I) A These organic groups G are connected to each other through an oligomer or polymer composed of F binds to bond (ii) of the n1-th repeating unit of the first segment A1 and to bond (i) of the first repeating unit of the following segment A2.

[0047] In a preferred embodiment of the present invention, polymer P1 has n1 interconnected repeating units of structural formula (I), and the proportion of repeating units of structural formula (I) in polymer P1 is 50% by weight or more, in particular 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, even more preferably 95% by weight or more and most preferably 99% by weight or more, based in each case on the molar weight of polymer P1.

[0048] In the process according to the invention, the suspension S1 provided in step (a) preferably comprises different polymers P1, the individual polymers P1 in this embodiment typically having different degrees of polymerization, i.e. at least some of the polymers P1 contained in the suspension S1 provided in step (a) have different n1.

[0049] In a further preferred embodiment of the present invention, the suspension S1 provided in step (a) comprises various polymers P1, and at least 10%, preferably at least 20%, more preferably at least 30%, even more preferably at least 50%, even more preferably at least 75%, and most preferably at least 99% of all polymers P1 contained in the suspension S1 provided in step (a) comprise at least one segment A1 made up of interconnected repeating units of structural formula (I), where n1 is 100 or more.

[0050] In a particularly preferred embodiment of the process according to the invention, the at least one polymer P1 has the structural formula (I'). [ka] a' is an integer of 2≦a'≦6, in particular a'=2 or 4, preferably a'=2. b' is an integer such that 2≦b'≦6, in particular b'=2 or 4, preferably b'=2. c' is an integer of 0≦c'≦10, in particular c'=0 or 1, preferably c'=0. n'1 is an integer of 49 or more, preferably an integer of 50 or more.

[0051] The polymer P1 having the structural formula (I') can also be represented as follows: R'-(W'1) n’1 -R”

[0052] Thus, W'1 corresponds to the structure contained in the brackets indexed "n'1" in structural formula (I'). Thus, unit W'1 has the following structure: [ka]

[0053] The n'1 units W'1 interconnected in the polymer P1 according to structural formula (I') are identical or different to one another in the polymer P1, in particular identical.

[0054] R' is -H, -(CH2) a◆ -[O-(CH2) b◆ ] c◆ -OH. a ◆ is 2≦a ◆ Integers ≦6, especially a ◆ = 2 or 4, preferably a ◆ =2. b ◆ is 2≦b ◆ Integers ≦6, especially b ◆ = 2 or 4, preferably b ◆ =2. c ◆ is 0≦c ◆ Integers ≦10, especially c ◆ = 0 or 1, preferably c ◆ =0.

[0055] R″ is selected from the group consisting of —H, —OH, and a group of structural formula (IV) or (VII), more preferably —H, —OH, and a group of structural formula (IV), more preferably —OH, and a group of structural formula (IV), wherein structural formulas (IV) and (VII) are as follows: [ka]

[0056] The process according to the invention is particularly suitable for the depolymerization of polyethylene terephthalate ("PET") and polybutylene terephthalate ("PBT"). Thus, in a preferred embodiment, the polymer P1 is selected from PET, PBT. The polymer P1 is most preferably PET.

[0057] PBT corresponds to polymer P1 according to structural formula (I') where a'=4, c'=0.

[0058] PET corresponds to polymer P1 according to structural formula (I') where a'=2, c'=0.

[0059] In the process according to the invention, the suspension S1 provided in step (a) preferably comprises various polymers P1 according to structural formula (I'). The individual polymers P1 in this embodiment typically have different degrees of polymerization, i.e., n'1 is different for at least some of the polymers P1 according to structural formula (I') contained in the suspension S1 provided in step (a).

[0060] In a further preferred embodiment of the present invention, the suspension S1 provided in step (a) comprises various polymers P1 of structural formula (I'), and in at least 10%, preferably at least 20%, more preferably at least 30%, even more preferably at least 50%, even more preferably at least 75%, and most preferably at least 99% of all polymer molecules P1 according to structural formula (I') contained in the suspension S1 provided in step (a), n'1 is 99 or greater, even more preferably n'1 is 100 or greater.

[0061] 2. Extruder E The process according to the invention is carried out in extruder E.

[0062] Extruders are well known to those skilled in the art and are described for various chemical reactions and processes, for example in WO 2020 / 053051 A1 and EP 2 455 424 A1. An extruder is generally understood to be a machine that receives solid to liquid molding materials, typically inside the extruder, and extrudes them, primarily continuously, as extrudates through a product outlet (or "opening"), which is in particular a die (according to DIN 24450:1987-02). Bockler F., Dill B., Eisenbrand G., Faupel F., Fugmann B., Gamse T., Matissek R., Pohnert G., Ruhling A., Schmidt S., Sprenger G., Somborn R, Extruder, RD-05-02432(2004), in ROMPP [Online], Stuttgart, Georg Thieme Verlag, [December 2022]; available online at https: / / roempp.thieme.de / lexicon / RD-05-02432, last accessed 14 January 2023.

[0063] The extruder E comprises two barrels G1, G2 and optionally a further barrel G3. In the context of the present invention, a "barrel" should be understood to mean an internal section of the extruder in which the reaction conditions (especially the temperature) can be adjusted independently of the remaining sections of the extruder.

[0064] The extruder additionally comprises conveying means capable of conveying the contents of the extruder from one barrel to the next and finally to the product outlet. In single or multi-screw extruders, this task is assumed, for example, by screw elements.

[0065] In a preferred embodiment of the present invention, the extruder E is selected from the group consisting of piston extruders and multi-screw extruders, with multi-screw extruders being particularly preferred. Preferred multi-screw extruders are planetary roller extruders or multi-screw extruders, in particular multi-screw extruders, more preferably twin-screw extruders.

[0066] In a preferred embodiment of the invention, an inert gas, such as nitrogen, is passed through extruder E during the process according to the invention.

[0067] 3. Process (a) In step (a) of the process according to the invention, a continuous phase P of at least one liquid polyolefin PO is Kon And, P Kon Particles P of at least one polymer P1 suspended in Par A suspension S1 containing the above is provided to barrel G1 and is transported from barrel G1 to barrel G2.

[0068] According to the general knowledge in the art, in the context of the present invention, a "suspension" refers to a liquid continuous phase ("P Kon ") insoluble solid particles ("P" in the present invention) Par "). See also RD-19-05060 (2002) in Bockler F., Dill B., Eisenbrand G., Faupel F., Fugmann B., Gamse T., Matissek R., Pohnert G., Ruhling A., Schmidt S., Sprenger G., ROMPP [Online], Stuttgart, Georg Thieme Verlag, [December 2022]; available at https: / / roempp.thieme.de / lexicon / RD-19-05060, last accessed January 14, 2023.

[0069] In step (a) of the process according to the invention, the at least one polymer P1 is present as a solid, i.e. as particles P Par that is, in the suspension S1 according to the invention, the at least one polymer P1 is used in the form of particles P Par It is suspended in the form of

[0070] This means that step (a), and preferably also step (b), is carried out at a temperature below the melting temperature of the at least one polymer P1.

[0071] Particles P of at least one polymer P1 used in step (a) Par In a preferred embodiment, at least 50%, in particular at least 90%, of the 90 "), and more preferably has a size of 1 mm to 10 mm.

[0072] According to the invention, the particle size distribution is determined by sieve analysis in accordance with standard DIN 66165-2:2016-08.

[0073] The process according to the invention is particularly suitable for treating waste comprising at least one polymer P1 and a polyolefin PO. In this embodiment, the waste to be post-treated in the process according to the invention can be ground prior to step (a) to obtain particles P1 of suitable size. Par can be used in step (a). This comminution can be achieved, for example, by grinding.

[0074] The suspension S1 provided in step (a) contains particles P of at least one polymer P1. Par The continuous phase P Kon As such, it comprises at least one polyolefin PO which is liquid, ie in the form of a melt.

[0075] The polyolefin PO is at least one polymer P1 having a melting temperature ("T P1 ) below the melting temperature ("T PO ").

[0076] The at least one polyolefin PO is in particular polyethylene ("PE", T PO :135℃), Polypropylene ("PP", T PO :160℃), Polyisobutylene ("PIB", T PO :54~56℃), Polybutylene ("PB", T PO : 135°C), preferably PE and PP. It is particularly preferred that PO=PE.

[0077] At least one polymer P1 is PET(T P1:260℃) or PBT (T P1 : 223°C), in particular in the embodiment where it is PET, the polyolefin PO is in particular selected from PE, PP, PIB, PB, preferably PE, PP, particularly preferably PO=PE.

[0078] Therefore, the ratio by weight of all polymers P1 contained in suspension S1 provided in step (a) to the weight of all polyolefins PO contained in suspension S1 provided in step (a) is not further limited and is in particular within the range of 99:1 to 1:99, preferably 98:2 to 10:90, more preferably 97:3 to 25:75, even more preferably 96:4 to 50:50, even more preferably 95:5 to 60:40, and most preferably 80:20.

[0079] According to the present invention, "temperature T a " is the temperature at which step (a) is carried out.

[0080] The suspension S1 comprises a melt of at least one polyolefin PO. It is at the temperature T at which the suspension S1 is provided in step (a) of the process according to the invention. a means that the melting temperature of the polyolefin PO is higher, in particular at least 1° C., preferably at least 5° C., more preferably at least 10° C. higher.

[0081] Since the at least one polymer P1 in the suspension S1 provided in step (a) and conveyed from barrel G1 to barrel G2 is in particulate form, step (a) of the process according to the invention is carried out at a temperature T 100° C. below the melting temperature T 200° C. of the at least one polymer P1. P1 Lower, temperature T a It goes without saying that this will be done in

[0082] If the at least one polymer P1 is selected from PBT and PET, in particular if P1=PBT, the temperature T ais preferably in the range of 165°C to 220°C, more preferably in the range of 170°C to 220°C, even more preferably in the range of 180°C to 220°C, even more preferably in the range of 190°C to 210°C, and most preferably in the range of 195°C to 202°C.

[0083] In another embodiment, when the at least one polymer P1=PET, the temperature T a is preferably in the range of 130°C to 255°C, more preferably in the range of 165°C to 240°C, even more preferably in the range of 165°C to 220°C, even more preferably in the range of 170°C to 220°C, even more preferably in the range of 180°C to 220°C, even more preferably in the range of 190°C to 210°C, and most preferably in the range of 195°C to 202°C.

[0084] In a further preferred embodiment, the weight proportion of all polyolefin PO in suspension S1 provided in step (a) is in the range of 1% to 99% by weight, preferably in the range of 3% to 75% by weight, preferably in the range of 5% to 50% by weight, more preferably in the range of 10% to 40% by weight, more preferably in the range of 15% to 30% by weight, and the remainder of suspension S1 provided in step (a) is polymer P1.

[0085] After suspension S1 has been provided in barrel G1 of extruder E in step (a) of the process according to the invention, suspension S1 is conveyed from barrel G1 to barrel G2. This can be done using conveying devices known to those skilled in the art and is typically done in an extruder, in particular in a screw element, a piston, preferably in a screw element.

[0086] 4. Process (b) In step (b) of the process according to the invention, at least one glycol compound G is introduced into at least one feeder Z G This is introduced into barrel G2.

[0087] In addition, at least one catalyst K, mixed with at least one glycol compound G or separate, preferably mixed, is introduced into barrel G2.

[0088] In barrel G2, at least one glycol compound G and at least one catalyst K are mixed with suspension S1, and the at least one glycol compound G is at least partially reacted with at least one polymer P1 in suspension S1 to form a mixture M comprising at least one cleavage product P2. G2 Therefore, this reaction is carried out in the presence of catalyst K.

[0089] 4.1 Glycol Compound G The glycol compound G added in step (b) has the structural formula (V). HO-(CH2) d -[O-(CH2) e ] f -OH d is an integer of 2≦d≦6, in particular d=2 or 4, preferably d=2. e is an integer of 2≦e≦6, in particular e=2 or 4, preferably e=2. f is an integer of 0≦f≦10, particularly f=0 or 1, preferably f=0.

[0090] The glycol compound G added in step (b) is -ethylene glycol (= ethane-1,2-diol, CAS number: 107-21-1, structural formula (V) where d=2 and c=0), -butylene glycol (= butane-1,4-diol, CAS number: 110-63-4, structural formula (V) where d=4 and c=0), -Diethylene glycol [=2-(2-hydroxyethoxy)ethanol, CAS number: 111-46-6, structural formula (V), d=2, e=2, f=1] Preferably, the compound is selected from the group consisting of Ethylene glycol is particularly preferred.

[0091] In a preferred embodiment of the invention, the glycol compound G added in step (b) is at least one product of the depolymerization of the polymer P1 according to the invention.

[0092] Thus, the glycol compound G added in step (b) is preferably ethylene glycol when the polymer P1 at least partially comprises segments of polyethylene terephthalate PET, and even more preferably when the polymer P1 is PET.

[0093] Therefore, the glycol compound G added in step (b) is preferably butylene glycol when the polymer P1 at least partially comprises segments of polybutylene terephthalate (= "PBT"), and even more preferably when the polymer P1 is PBT.

[0094] a feeder Z for introducing at least one glycol compound G into the barrel; G can be selected according to the knowledge of the person skilled in the art and may for example be in the form of a valve.

[0095] 4.2 Catalyst K The reaction of at least a portion of the polymer P1 in suspension S1 with at least one glycol compound G in step (b) of the process according to the invention is carried out in the presence of at least one catalyst K. The catalyst K is selected from the group consisting of M A Ethylene glycolate, ROM A M A is an alkali metal, and R is an alkyl group having 1 to 6 carbon atoms.

[0096] Therefore, M A Ethylene glycolate and ROM A is an "alkali metal alkoxide."

[0097] Preferably, catalyst K is introduced into barrel G2 in step (b) mixed with at least one glycol compound G, i.e., together with at least one glycol compound G. Alternatively, catalyst K may be introduced into barrel G2 in step (b) separately from at least one glycol compound G.

[0098] In the context of the present invention, "M A "Ethylene glycolate" is a compound of ethylene glycol and M A "M" is understood to mean the corresponding salts of A The term "ethylene glycolate" refers to M A O-CH2-CH2-OH and M A O-CH2-CH2-OM A At least one of, preferably at least M A O-CH2-CH2-OH, Most preferably M A O-CH2-CH2-OH and M A O-CH2-CH2-OM A Includes:

[0099] M A is in particular selected from the group consisting of lithium, potassium and sodium. A is preferably selected from the group consisting of potassium and sodium. A It is very particularly preferred if is sodium.

[0100] Alkali metal alkoxide ROM A wherein R is an alkyl group having 1 to 6 carbon atoms, and R is in particular selected from the group consisting of methyl, ethyl, propyl (relating to n-propyl or isopropyl), butyl, in particular n-butyl, pentyl, in particular n-pentyl, hexyl, in particular n-hexyl.

[0101] In a particularly preferred embodiment, the catalyst K is selected from the group consisting of sodium ethylene glycolate, potassium ethylene glycolate, potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, more preferably selected from the group consisting of potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, even more preferably selected from the group consisting of sodium methoxide, potassium ethoxide, sodium ethoxide, and particularly preferably K=sodium methoxide.

[0102] The alkali metal alkoxides which can be used as catalyst K in the process according to the invention can be prepared according to the knowledge of a person skilled in the art, for example by reactive distillation from the corresponding alcohol and the corresponding alkali metal hydroxide, as described in EP 1 997 794 (A1), WO 01 / 42178 (A1), WO 2021 / 148174 (A1), WO 2021 / 148175 (A1), WO 2022 / 117803 (A1), WO 2022 / 167311 (A1), WO 2022 / 263032 (A1), EP 4 074 684 (A1), EP 4 074 685 (A1).

[0103] Alternatively, alkali metal alkoxides which can be used as catalyst K in the process according to the invention can be produced by alcohol exchange from the corresponding alcohol and another alkoxide. The corresponding preparation of alkali metal alkoxides is described, for example, in Czechoslovak Patent Application Publication No. 213 119 (B1), British Patent Application Publication No. 490,388 (A), German Patent No. 689 03 186 (T2) and European Patent No. 0 776 995 (A1).

[0104] Similarly, alcohol exchange by reactive distillation to provide alkoxides, in particular alkali metal alkoxides, which can be used as catalysts K in the process according to the invention are described in WO 2021 / 122702 A1, DE 27 26 491 A1 and DE 1 254 612 B.

[0105] The alkoxides which can be used as catalysts K according to the invention can also be generated electrochemically, as described, for example, in EP 3 885 470 A1, EP 3 885 471 A1, EP 4 043 616 A1, EP 4 112 778 A1, WO 2023 / 274796 A1 and WO 2023 / 274794 A1.

[0106] The amount of catalyst K used in step (b) can be selected by a person skilled in the art according to the knowledge in the art. The molar amount of all catalysts K used in step (b) is in particular in the range of 0.01% to 10%, preferably in the range of 0.1% to 5%, more preferably in the range of 1% to 4%, and even more preferably in the range of 2.5% to 3.5%, based on the molar amount of all glycol compounds G used in step (b).

[0107] The catalyst K is preferably used in solid form, for example in the form of a powder or granules.

[0108] 4.3 Reaction conditions in step (b) The reaction according to step (b) of the process according to the present invention is carried out in particular by the reaction of the product outlet E X The mixture M extracted G2This is carried out until the weight of all polymers P1 in the suspension S1 is reduced by at least 10% by weight, preferably at least 20% by weight, more preferably at least 30% by weight, more preferably at least 40% by weight, more preferably at least 50% by weight, even more preferably at least 60% by weight, even more preferably at least 70% by weight, even more preferably at least 80% by weight, even more preferably at least 90% by weight and most preferably at least 98% by weight, in each case based on the weight of all polymers P1 in the suspension S1 provided in step (a).

[0109] The mixture S1 during the reaction in step (b) and the mixture M obtained after the completion of step (b) G2 The water content of the glycol compound G is preferably as low as possible so that the rate of solvolytic transesterification is as high as possible and the rate of hydrolytic ester cleavage is as low as possible in the reaction of the glycol compound G with the polymer P1 in step (b). These two different reactions are shown in Scheme 1 below.

[0110] As is evident from Scheme 1, polymer P1 [represented in the center by the segment from structural formula (I')], when reacted with G, undergoes a solvolytic transesterification reaction to give two cleavage products P2 (bottom half of Scheme 1). This transesterification reaction optionally proceeds via an intermediate esterification with catalyst K. For example, the use of an alkali metal methoxide results in the intermediate formation of a methyl ester of the terephthalic acid group, which is then transesterified with glycol compound G to give the ester of glycol compound G. This catalytic mechanism is not taken into account in Scheme 1.

[0111] Scheme 1 [ka]

[0112] The terminal carboxylic acid groups of the two resulting cleavage products are esterified with G (last line of Scheme 1, cleavage product P2, left side) or with the alkylene glycol unit present in P1 (last line of Scheme 1, cleavage product P2, right side). When cleavage product P2 is repolymerized to obtain polymer P1, these ester groups are more readily converted to polymer P1, and therefore are the preferred cleavage product P2. The glycolysis of PET with ethylene glycol, for example, results in the formation of the desired diester bis(2-hydroxyethyl) terephthalic acid BHET.

[0113] In contrast, the presence of water in suspension S1 during the reaction according to step (b) causes the polymer P1 to hydrolytically cleave, forming unfavourable cleavage products P2.

[0114] This is shown in the top half of Scheme 1. This results in two cleavage products P2, one of which has a free, i.e., unesterified, carboxylic acid group at its end (Scheme 1, first row, cleavage product P2, left side). Conversion of such cleavage product P2 to a new polymer P1 is costly, inconvenient, and therefore unfavorable. In the hydrolysis of PET, for example, TS is formed as the main product, and the monoester of 2-hydroxyethyl terephthalic acid, MHET, is also formed.

[0115] It is therefore advantageous to keep the water content in mixture S1 as low as possible during the reaction according to step (b).

[0116] Thus, in a preferred embodiment of the present invention, the water content in suspension S1 during the reaction according to step (b) is less than 10% by weight, more preferably less than 5% by weight, even more preferably less than 1% by weight, even more preferably less than 0.1% by weight and most preferably less than 0.01% by weight, in each case based on the total weight of suspension S1.

[0117] The proportion of the at least one glycol compound G added to suspension S1 in barrel G2 in step (b) is not further limited. In step (b), it is advantageous to cleave polymer P1 into as high a proportion of cleavage products P2 as possible. This is advantageously controlled by the amount of at least one glycol compound G added to suspension S1 in step (b).

[0118] In a preferred embodiment of the process according to the invention, the molar amount of all glycol compounds G introduced into barrel G2 in step (b) is at least 0.01 molar equivalents, more preferably in the range of 0.1 to 50 molar equivalents, more preferably in the range of 0.3 to 40 molar equivalents, more preferably in the range of 0.5 to 20 molar equivalents, even more preferably in the range of 1.0 to 15 molar equivalents, even more preferably in the range of 2.0 to 10 molar equivalents, and even more preferably in the range of 3.0 to 5.0 molar equivalents, in each case based on the molar amount of all repeating units of structural formula (I) contained in polymer P1 in suspension S1 provided in step (a).

[0119] The process according to the invention is preferably carried out solvolytically in order to minimize the proportion of undesired products (such as TS or MHET in the case of hydrolysis of PET) in the reaction product as much as possible and to maximize the proportion of desired products (such as BHET in the case of solvolysis of PET with ethylene glycol) in the reaction product. Thus, it is preferred if the water content of the glycol compound G added in step (b) is less than 10% by weight, more preferably less than 5% by weight, even more preferably less than 1% by weight, even more preferably less than 0.1% by weight, and most preferably less than 0.01% by weight, based on the total weight of all glycol compounds G added in step (b).

[0120] In the suspension S1, the polyolefin PO is inert to the reaction conditions according to step (b), ie it does not react substantially with the glycol compound G.

[0121] "T b" should be understood to mean the temperature during the reaction according to step (b).

[0122] The reaction in step (b) of the process according to the invention is carried out in particular at a temperature above the melting temperature T PO higher than the temperature T b The polyolefin PO is therefore present as a melt in step (b) and already in step (a), and the reaction according to step (b) can advantageously be carried out in said melt.

[0123] temperature T b Also, during step (b), the melting temperature T of the at least one polymer P1 P1 In step (b), the temperature T b is the melting temperature T of at least one polymer P1 P1 Preferably, the at least one polymer P1 is then present in particulate form during step (b).

[0124] Therefore, the reaction in step (b) of the process according to the invention preferably takes place at a temperature above the melting temperature T PO and the melting temperature T P1 Lower than temperature T b It is held at.

[0125] If the at least one polymer P1 is selected from PBT, PET, preferably P1=PBT, the temperature T b The temperature is preferably in the range of 165°C to 220°C, more preferably in the range of 170°C to 215°C, even more preferably in the range of 180°C to 210°C, and most preferably in the range of 190°C to 200°C. This is especially true when the polyolefin PO is polyethylene ("PE", T PO :135℃), Polypropylene ("PP", T PO :160℃), Polyisobutylene ("PIB", T PO :54~56℃), Polybutylene ("PB", T POIt is advantageous when the polyolefin PO is selected from the group consisting of PE and PP.

[0126] P1=PET, temperature T b is preferably in the range of 165° C. to 255° C., more preferably in the range of 170° C. to 240° C., even more preferably in the range of 180° C. to 210° C., and most preferably in the range of 190° C. to 200° C. This is particularly advantageous when the polyolefin PO is selected from PE, PP, PIB, and PB, and more preferably when the polyolefin PO is selected from PE and PP.

[0127] If P1=PET and PO=PE, then at temperature T b is preferably in the range of 140°C to 255°C, more preferably in the range of 150°C to 240°C, even more preferably in the range of 165°C to 230°C, even more preferably in the range of 180°C to 210°C, and most preferably in the range of 190°C to 200°C.

[0128] 4.4 Cleavage product P2 In step (b) of the process according to the invention, in barrel G2, at least a portion of the polymer P1 contained in suspension S1 is reacted with at least one glycol compound G and at least one catalyst K to obtain at least one cleavage product P2. Thus, in step (b), a mixture M containing at least one cleavage product P2 is obtained. G2 get.

[0129] The cleavage product P2 has the structural formula (II). [ka] a II is 2≦a II Integers ≦6, especially a II = 2 or 4, preferably a II =2. b II is 2≦b II Integers ≦6, especially b II = 2 or 4, preferably bII =2. c II is 0≦c II Integers ≦10, especially c II = 0 or 1, preferably c II =0. n2 is an integer in the range of 1≦n2≦48.

[0130] Structural formula (II) is "R II1 -(W2) n2 -R II2 " Thus, W2 corresponds to the structure contained in the brackets indexed "n2" in structural formula (II). [ka]

[0131] The repeating units W2 interconnected with 2≦n2≦48 in the cleavage product P2 may be identical or different within the cleavage product P2. This results in molecules P2 that may contain identical or different groups W2 (i.e., for example, different values ​​of a II , b II and / or c II (having).

[0132] R II1 -H, -(CH2) a△ -[O-(CH2) b△ ] c△ —OH. a △ is 2≦a △ Integers ≦6, especially a △ = 2 or 4, preferably a △ =2. b △ is 2≦b △ Integers ≦6, especially b △ = 2 or 4, preferably b △ =2. c △ is 0≦c △ Integers ≦10, especially c △ = 0 or 1, preferably c △=0.

[0133] R II2 is selected from the group consisting of -H, -OH, and a group of structural formula (IV), preferably from the group consisting of -OH, and a group of structural formula (IV), wherein structural formula (IV) is: [ka]

[0134] a II =2, c II =0, a △ =2, c △ The cleavage product P2 of structural formula (II), where n = 0 and 2 ≤ n2 ≤ 48, is also called "BHET oligomer" or "oligomer of BHET" according to the present invention.

[0135] In certain mixtures, in particular suspension S1 or mixture M G2 The amount of cleavage product P2 and polymer P1 in the polymer P1 can be determined by measurement methods known to those skilled in the art. According to the present invention, the molecular weight distribution (and therefore the average degree of polymerization ρ) of polymer P1 and cleavage product P2 is determined by gel permeation chromatography ("GPC") according to Method 1 (see Examples section).

[0136] In certain mixtures, in particular suspension S1 or mixture M G2 The content of Compound (III) in the sol can be determined by measurement methods known to those skilled in the art, preferably by nuclear magnetic resonance ("NMR") or chromatography.

[0137] Thus, after step (b) is completed, a mixture M containing at least one cleavage product P2 is obtained. G2 is obtained.

[0138] In a further preferred embodiment, the mixture M G2 Based on the molar amount of all cleavage products P2 contained in the product outlet E X Mixture M in G2and the molar proportion of all cleavage products P2 containing 20 or fewer repeating units of structural formula W2 is at least 25%, preferably at least 40%, more preferably at least 50%, even more preferably at least 70%, and even more preferably at least 85%.

[0139] In another preferred embodiment, the product outlet E X Mixture M in G2 Based on the molar amount of all cleavage products P2 contained in the product outlet E X Mixture M in G2 is at least 10%, more preferably at least 25%, even more preferably at least 30%, and even more preferably at least 50%, and wherein structural formula (III) is: [ka]

[0140] In structural formula (III), R 1 and R 2 are, independently of each other, -H, -(CH2) p -[O-(CH2) q ] r -OH, preferably R 1 Groups and R 2 At least one, and even more preferably both, of the groups independently of one another have the structural formula -(CH) p -[O-(CH2) q ] r It is a -OH group.

[0141] R 1 Groups and R 2 Each group has the structural formula -(CH2) p -[O(CH2) q ] r Even more preferred are the same groups of -OH. p is an integer of 2≦p≦6, in particular p=2 or 4, preferably p=2. q is an integer such that 2≦q≦6, in particular q=2 or 4, preferably q=2. r is an integer of 0≦r≦10, in particular r=0 or 1, preferably r=0.

[0142] 5.Process (c) In the reaction in step (b), a mixture M containing at least one cleavage product P2 is G2 This mixture M G2 is the product outlet E in step (c). X Mixture M G2 is the product outlet E X It is extracted with.

[0143] Suitable product outlet E X In the extruder E, the mixture M G2 This includes any opening through which the product can be removed. X is typically located at the end of the extruder E. In embodiments where the extruder E comprises only two barrels G1 and G2, the product outlet E X Typically, the mixture M is passed through barrel G2 so as to obtain the mixture immediately after passing through barrel G2. In an embodiment in which extruder E comprises, in addition to the two barrels G1 and G2, a further barrel G3, the mixture M is passed through barrel G1. G2 is typically removed after passing through barrel G3.

[0144] The reaction in step (b) of the process according to the invention advantageously proceeds in such a way that the cleavage product P2 is released into the product outlet E X The mixture M extracted G2 In a preferred embodiment of the present invention, the product outlet E X The mixture M extracted G2 The proportion of all cleavage products P2 in the product outlet E X The mixture M extracted G2 based on the total weight of at least 50% by weight, more preferably at least 60% by weight, even more preferably at least 70% by weight, even more preferably at least 80% by weight, and even more preferably at least 90% by weight.

[0145] Product outlet E X A mixture M different from the cleavage product P2 is taken out by G2 are chosen in particular from glycol compounds G, unconverted polymers P1, preferably glycol compounds G.

[0146] In a further preferred embodiment, the product outlet E X The mixture M extracted G2 The weight (grams) of all cleavage products P2 in the product outlet E X The mixture M extracted G2 The ratio of the weight (grams) of all polymers P1 in the polymer P1 to the weight (grams) of all polymers P1 in the polymer P1 is greater than 1:1, more preferably greater than 2:1, even more preferably greater than 3:1, even more preferably greater than 4:1, even more preferably greater than 10:1, even more preferably greater than 30:1, even more preferably greater than 100:1, even more preferably greater than 1000:1.

[0147] In an optional embodiment of the process according to the invention, extruder E may be configured to extrude from barrel G2 to product outlet E X During transport to the G2 In this embodiment, if the reaction does not proceed sufficiently in barrel G2, a product outlet E X For example, a post-reaction treatment can then optionally be carried out in barrel G3 at an elevated or reduced temperature relative to the temperature of G2, or mixture M G2 may be cooled in barrel G3.

[0148] The process according to the invention is carried out in such a manner that the PET to be subjected to depolymerization is in a continuous phase P Kon It is characterized in that it is used as suspension S1 in step (a) together with a polyolefin as the base.

[0149] Surprisingly, it has been found that this minimizes pressure spikes and non-uniform process modes.

[0150] A contributing factor to this effect is that in step (a), suspension S1 is provided in barrel G1 and glycol compound G is introduced only in barrel G2.

[0151] In a preferred embodiment, at least one feeder Z supplies at least one glycol compound G to barrel G2. G Further upstream, the volume of suspension S1 in the extruder E and at least one feeder Z which feeds at least one glycol compound G into barrel G2 G From product exit E X Suspension S1 and mixture M G2 The ratio of the total volume of the components to the total volume of the components is in the range of 1:99 to 99:1, more preferably in the range of 1:9 to 9:1, even more preferably in the range of 1:4 to 4:1, even more preferably in the range of 2:3 to 3:2, and even more preferably 1:1.

[0152] The corresponding volume, i.e., - "at least one feeder Z for feeding at least one glycol compound G into barrel G2" G The volume of the suspension S1 in the extruder E (abbreviated as "U up ") and - "at least one feeder Z for feeding at least one glycol compound G into barrel G2" G From product exit E X Suspension S1 and mixture M G2 The sum of the volumes of down ") can be determined according to the invention by the following test.

[0153] 1. Extruder E, product outlet E X Orient it so that it is at its lowest point.

[0154] 2.Product outlet E X , and product outlet E X and in the process according to the invention, the supply device Z G All feeders and outputs of extruder E between the most upstream feeder used as the feeder and the output are sealed off watertight.

[0155] 3. Extruder E is filled with water, and feeding device Z is unblocked. G Then, determine the volume of water in the extruder E. This volume is U. down is.

[0156] 4. Here, product outlet E X , and product outlet E X and the most upstream supply device Z O All feeders and outputs of extruder E between the

[0157] In the process according to the invention, P1 and polyolefin PO are mixed in a mixture M X When added to G1 as Z O This mixture M X It is the most upstream supply device.

[0158] In the process according to the invention, P1 is connected to at least one supply device Z P1 G1 by the polyolefin PO is added to at least one feeder Z PK If it is added separately to G1 by Z O All supply equipment Z P1 , Z PK It is the most upstream supply device.

[0159] 5. Extruder E is filled with water and unblocked feeder Z. O Then, determine the volume of water in the extruder E. This volume is U. up +U down This value and U down The difference is U up Give.

[0160] The following examples are intended to illustrate the invention.

[0161] Example Comparative Example 1 The ground PET flakes are weighed gravimetrically and drawn at 70° C. into barrel G0 (process space) of an extruder having multiple barrels (ie sections whose wall temperatures can be adjusted separately).

[0162] PET flakes are conveyed from barrel G0 into barrel G1, where the temperature is raised to 265°C, thus melting the metered PET flakes. From barrel G1, the PET melt is conveyed to barrel G2, where a 4 wt. % solution of sodium ethylene glycolate in ethylene glycol is injected. The mass flow ratio between the sodium ethylene glycolate solution and the PET is 0.5. The barrel temperature immediately downstream of the injection point is also 265°C and decreases to 130°C toward the extruder exit. At the extruder exit, a mixture containing the main component BHET, BHET oligomers (corresponding to polymer P2, where n2 = 2 to 48), and ethylene glycol is discharged. Pulsating emissions of ethylene glycol vapor are observed at irregular intervals.

[0163] Comparative Example 2 In the extruder from Comparative Example 1, polyethylene granules (PE) in addition to PET flakes are weighed in at the extruder inlet. The proportion of PE based on the total polymer stream is 20% by weight. The temperature profile and the metered addition of the sodium ethylene glycolate solution in ethylene glycol are realized as in Comparative Example 1. The mass flow ratio between the sodium ethylene glycolate solution and the PET is 0.5. At the extruder outlet, a mixture containing the main components BHET, BHET oligomers, PE aggregates, and ethylene glycol is discharged. Pulsating emissions of ethylene glycol vapor are observed at irregular intervals.

[0164] Comparative Example 3 The ground PET flakes are weighed gravimetrically and drawn into barrel G0 (process space) of the extruder used in Comparative Example 1 at 70°C.

[0165] The PET flakes are conveyed from barrel G0 into barrel G1, where the temperature is increased to 195° C. From there, the PET flakes are conveyed to the extruder outlet at a barrel temperature of 195° C. without the addition of ethylene glycol or sodium ethylene glycolate.

[0166] Although the barrel temperature of the extruder does not exceed 195°C and is therefore below the melting temperature of PET, the PET flakes are heated by friction, melting and consequently exiting the extruder as agglomerates.

[0167] Comparative Example 4 Comparative Example 4 is carried out in the same manner as Comparative Example 3, but in addition to the PET flakes, polyethylene granules (PE) are weighed out gravimetrically. The proportion of PE based on the total polymer stream is 20% by weight. A suspension of unmelted PET flakes in the PE melt is discharged at the extruder outlet.

[0168] Examples of the present invention The inventive example was carried out using the equipment of Comparative Example 2. However, in contrast to Comparative Example 2, the barrel temperature of barrel G1 was set at 195°C instead of 265°C, i.e., lower than the melting temperature of PET but higher than the melting temperature of PE. This resulted in the formation of a suspension of PET flakes in the PE melt. This suspension was conveyed to barrel G2, where a 4 wt. % solution of sodium ethylene glycolate in ethylene glycol was injected. The mass flow ratio of the sodium ethylene glycolate solution to the PET was 0.5. The barrel temperature immediately downstream of the injection point was also 195°C and decreased to 130°C toward the extruder exit. At the extruder exit, a mixture containing the main components BHET, BHET oligomers, PE aggregates, and ethylene glycol was discharged. No pulsating emissions of ethylene glycol vapor were observed.

[0169] result The use of a suspension of PET in PE at the extruder inlet allows for a lower process temperature, thus enabling stable and efficient depolymerization of PET. The pulsation that occurs in conventional processes, which is questionable from a safety standpoint, is eliminated. This provides an efficient and safe process for the depolymerization of polyalkylene terephthalates, particularly PET and PBT.

[0170] analysis According to the present invention, the molecular weight distribution of the polymer P1 and the cleavage products P2 (and therefore the average degree of polymerization ρ in a given mixture) is determined by gel permeation chromatography (GPC) according to the following method 1. Method 1 is based on the methodology of page 356 of the article by M.R. Milana, M. Denaro, L. Arrivabene, A. Maggio, L. Gramiccioni, Food Additives and Contaminants, 1998, 15, 355-361.

[0171] Method 1 1. A sample of the mixture to be tested is diluted in 1,1,1,3,3,3-hexafluoro-2-propanol ("HFIP") in a 1:333 weight ratio and allowed to dissolve at room temperature for 24 hours.

[0172] 2. Filter the solution through a 1 μm disposable polytetrafluoroethylene filter and inject with an autosampler for analysis.

[0173] 3. The following system for size exclusion chromatography ("GPC") was used: Eluent: HFIP / 0.05M KTFAc (potassium trifluoroacetate) Precolumn: PSS PFG, 7 μm, guard, ID 8.00 mm x 50.00 mm Column: PSS PFG, 7 μm, 100 Å, ID 8.00 mm x 300.00 mm PSS PFG, 7μm, 100Å, ID 8.00mm x 300.00mm PSS PFG, 7μm, 300Å, ID 8.00mm x 300.00mm Pump: PSS-SECcurity 1260 HPLC pump Flow rate: 1.0ml / min Injection system: PSS-SECurity 1260 autosampler Injection volume: 50 μl Sample concentration: 3.0g / L Temperature: 30℃ Detector: SECcurity 2 Differential Refractometer Detector (RI) Evaluation: PSS-WinGPC UniChrom version 8.4

[0174] 4. Calibration is carried out with PMMA standards (PMMA = polymethyl methacrylate) in the separation area of ​​the column combination. The molar mass averages and their distributions, giving the average degree of polymerization ρ in a given mixture, are calculated using computer aids and are based on PMMA calibration by the strip method.

Claims

1. Product outlet E Ｘ And two barrel G １ , G ２ , and optionally further barrel G ３ At least one polymer P in an extruder E comprising １ 1. A process for the depolymerization of said at least one polymer P １ But, n １ The following structural formula (I): 【Chemistry 1】 (Wherein, a is an integer of 2≦a≦6, b is an integer of 2≦b≦6; c is an integer of 0≦c≦10; n １ is an integer equal to or greater than 50) and The polymer P １ The n included in １ the interconnected repeat units of structural formula (I) are the same or different; The n repeat units of structural formula (I) are linked such that the bond labeled "(i)" of one repeat unit of structural formula (I) is connected to the bond labeled "(ii)" of an adjacent repeat unit of structural formula (I). １ The interconnected repeating units of structural formula (I) form the polymer P １ are interconnected within (a) a continuous phase P of at least one liquid polyolefin PO Ｋｏｎ And, P Ｋｏｎ the at least one polymer P suspended in １ Particle P Ｐａｒ A suspension S containing １ The barrel G １ and the barrel G １ to the barrel G ２ and conveying the (b) Structural formula (V): HO-(CH ２ ) ｄ - [O-(CH)] ２ ) ｅ ] ｆ -OH (Wherein, d is an integer of 2≦d≦6, e is an integer in the range of 2≦e≦6; f is an integer of 0≦f≦10. at least one glycol compound G having Ｇ The barrel G ２ Introduced into M, mixed with said at least one glycol compound G or separately Ａ Ethylene glycolate, ROM Ａ (In the formula, M Ａ is an alkali metal, and R is an alkyl group having 1 to 6 carbon atoms), ２ Introduced into The barrel G ２ wherein the at least one glycol compound G and the at least one catalyst K are added to the suspension S １ and mixing the at least one glycol compound G with the suspension S １ The at least one polymer P １ to at least partially react with at least one cleavage product P ２ A mixture M containing Ｇ２ A process for obtaining The cleavage product P ２ is represented by structural formula (II): 【Chemistry 2】 (In the formula, a ＩＩ is 2≦a ＩＩ is an integer ≦6, b ＩＩ is 2≦b ＩＩ is an integer ≦6, c ＩＩ is 0≦c ＩＩ is an integer ≦10, n ２ is 1≦n ２ is an integer ≦48 and The cleavage product P ２ Within, 2≦n ２ ≦48 interconnected units W ２ (Each unit W ２ is "n" in structural formula (II). ２ ") corresponds to the structure contained in the brackets indexed "," ２ are identical or different within R ＩＩ１ -H, -(CH ２ ) ａ△ -[O-(CH ２ ) ｂ△ ] ｃ△ -OH (In the formula, a △ is 2≦a △ is an integer ≦6, b △ is 2≦b △ is an integer ≦6, c △ is 0≦c △ is an integer ≦10) is selected from the group consisting of R ＩＩ２ is —H, —OH, structural formula (IV) 【Transformation 3】 and (c) The mixture M Ｇ２ The product outlet E Ｘ and the mixture is optionally conveyed to a further barrel G ３ and passes through the product outlet E Ｘ The process of extracting The process includes:

2. The suspension S during the reaction according to step (b) １ The water content in the suspension S １ 2. The process of claim 1, wherein the total weight of the

3. The at least one glycol compound G is added to the barrel G ２ the at least one supply device Z Ｇ Further upstream, the suspension S in the extruder E １ and the at least one glycol compound G is introduced into the barrel G ２ the at least one supply device Z Ｇ From the product outlet E Ｘ The suspension S １ and said mixture M Ｇ２ 3. The process of claim 1 or 2, wherein the ratio of the total volume of the saturates to the total volume of the saturates is in the range of 1:99 to 99:

1.

4. The product outlet E Ｘ The mixture M taken out Ｇ２ All cleavage products P ２ The ratio of the product outlet E Ｘ The mixture M taken out Ｇ２ 4. The process of claim 1, wherein the total weight of the catalyst is at least 50% by weight.

5. The suspension S provided in step (a) １ All polymers P contained in １ and the weight of the suspension S provided in step (a). １ The process according to any one of claims 1 to 4, wherein the weight ratio of all polyolefins PO contained in the polyolefin PO is in the range of 99:1 to 1:

99.

6. The catalyst K is added to the barrel G separately from the at least one glycol compound G in step (b). ２ 6. The process of claim 1, wherein the

7. The catalyst K is mixed with the at least one glycol compound G in step (b) to form the barrel G ２ 6. The process of claim 1, wherein the

8. In step (b), the barrel G ２ The molar amount of all glycol compounds G introduced into the suspension S provided in step (a) １ The polymer P １ 8. The process of claim 1, wherein the molar amount of all repeat units of structural formula (I) encompassed by the formula (I) is 0.01 molar equivalents or more.

9. 9. The process of any one of claims 1 to 8, wherein the molar amount of all catalysts K used in step (b) is in the range of 0.01% to 10%, based on the molar amount of all glycol compounds G used in step (b).

10. The product outlet E Ｘ The mixture M taken out Ｇ２ All cleavage products P ２ and the weight of the product outlet E Ｘ The mixture M taken out Ｇ２ All polymers P １ 10. The process of claim 1, wherein the weight ratio of

11. The product outlet E Ｘ The mixture M Ｇ２ All cleavage products P contained in ２ The product outlet E based on the molar amount of Ｘ The mixture M Ｇ２ The molar proportion of all compounds of structural formula (III) contained in the compound (III) is at least 10%, and structural formula (III) is as follows: 【Chemistry 4】 (In the formula, R １ and R ２ are each independently -H, -(CH ２ ) ｐ -[O(CH ２ ) ｑ ] ｒ -OH; p is an integer in the range of 2≦p≦6; q is an integer of 2≦q≦6, r is an integer of 0≦r≦10), 11. The process according to any one of claims 1 to 10.

12. M Ａ 12. The process of claim 1, wherein is selected from the group consisting of lithium, potassium, and sodium.

13. 13. The process of any one of claims 1 to 12, wherein the catalyst K is selected from the group consisting of sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide.

14. said at least one polymer P １ 14. The process according to any one of claims 1 to 13, wherein = polyethylene terephthalate (PET).

15. 15. The process according to any one of claims 1 to 14, wherein the polyolefin PO is selected from polyethylene PE, polypropylene PP.

Images