Process for depolymerizing polyalkylene terephthalate in mixture of low melting point polyolefins

Abstract

The invention relates to a method for depolymerizing at least one polymer P1 in a polymer mixture containing not only at least one polymer P1 but also at least one polyolefin PO having a melting point lower than P1, in particular polyethylene PE or polypropylene PP. Polymer P1 is a polyalkylene terephthalate, i.e. A polymer comprising terephthalic acid units and alkylene glycol units, in particular polyethylene terephthalate PET or polybutylene terephthalate PBT. The method according to the invention comprises two steps in which the polymer P1 is substantially reacted in the first step with a diol compound G, resulting in a cleavage product P2 having a chain length that is longer than P1. In a second step, the cleavage product P2 and any polymer P1 not converted in the first step are reacted with an additionally added diol compound G and at least partially decomposed into monomeric units. The first step is carried out above the melting temperature TPO of the polyolefin PO, and the second step is carried out below the melting temperature TPO of the polyolefin PO. This makes it possible to simply and efficiently separate the solid polyolefin PO from the mixture obtained after the end of the second step.

Description

[0001] The present invention relates to a process for depolymerizing at least one polymer P1 in a polymer mixture comprising not only the at least one polymer P1 but also at least one polyolefin (PO), in particular polyethylene (PE) or polypropylene (PP), having a melting point lower than that of P1. The polymer P1 is a polyalkylene terephthalate, i.e. a polymer comprising terephthalic acid units and alkylene glycol units, in particular polyethylene terephthalate (PET) or polybutylene terephthalate (PBT).

[0002] The process according to the invention comprises two steps, wherein the polymer P1 is reacted in a first step substantially with the diol compound G to give a cleavage product P2 having a shorter chain length than P1. In a second step, the cleavage product P2 and any polymer P1 not converted in the first step are reacted with further added diol compound G and are at least partially decomposed into monomer units. The first step is carried out at a temperature above the melting temperature T of the polyolefin PO. PO The second step is carried out at a temperature lower than the melting temperature T of the polyolefin PO. PO This allows simple and efficient separation of the solid polyolefin PO from the mixture obtained after the second step. Background Art

[0003] Polyethylene terephthalate (= "PET") is one of the most important plastics and is used in textile fibers, as films and as a material for plastic bottles. In 2007 alone, ~10 7 t(W.Caseri,Polyethylenterephthalate,RD-16-03258(2009)in F. B.Dill,G.Eisenbrand,F.Faupel,B.Fugmann,T.Gamse,R.Matissek,G.Pohnert,A.Rühling,S.Schmidt,G.Sprenger, [Online], Stuttgart, Georg Thieme Verlag, January 2022).

[0004] PET-derived waste constitutes one of the greatest environmental challenges today due to its persistence and volume. Similar problems exist for other polyalkylene terephthalates similar to PET, such as polybutylene terephthalate ("PBT").

[0005] The solution to this problem lies in the avoidance of these plastics and their efficient reuse.

[0006] The prior art has proposed a variety of methods for cracking PET.

[0007] GB 784,248A describes the methanolysis of PET.

[0008] JP 2000-309663 A, US Pat. No. 4,355,175 A and T. Yoshioka, N. Okayama, A. Okuwaki, Ind. Eng. Chem. Res. 1998, 37, 336-340 describe hydrolysis methods for the depolymerization of PET.

[0009] The reaction of PET with diol compounds is described in US 3,884,850, EP 0 723 951 A1, US 3,222,299A, WO 2020 / 002999 A2, by SR Shukla, AM Harad in Journal of Applied Polymer Science 2005, 97, 513-517 (hereinafter “Shukla & Harad”) and by ND Pinale, SR Shukla in European Polymer Journal 2008, 44, 4151-4156.

[0010] Shukla & Harad point out that the glycolysis of PET produces bis(2-hydroxyethyl) terephthalate (= "BHET"). This cleavage product can also be used as a reactant for the production of new PET.

[0011] S. KMVan Geem,R.Denolf,M.Roosen,N.Mys,K.Ragaert,S.DeMeester,Green Chem.2020,22,5376-5394(" et al.) studied the hydrolysis of PET waste in alkaline aqueous solution to obtain ethylene glycol and terephthalic acid (=TS), especially the effect of certain reaction parameters such as temperature, ethanol / water ratio, etc. on the depolymerization rate. et al. also discussed the problem of contamination of the PET starting material with another polymer such as a low melting point polyolefin (hereinafter "polyolefin" is abbreviated as "PO").

[0012] In addition to these processes, there are also processes in which PET-containing waste is pyrolyzed in an extruder and then post-processed.

[0013] No. 5,545,746 A describes the depolymerization of PET waste in an extruder to give ethylene glycol and TS.

[0014] L. Biermann, E. Brepohl, C. Eichert, M. Paschetag, M. Watts, S. Scholl, Green Process. Synth. 2021, 10, 361-373 (“Biermann et al.”), related to US 5,545,746 A, and WO 2020 / 053051 A1 describe the hydrolysis of mixed waste (PET / PE) in a twin-screw extruder using solid sodium hydroxide to obtain ethylene glycol and terephthalic acid (= “TS”).

[0015] MA Mohsin, T. Abdulrehman, Y. Haik, Int. J. Chem. Eng. 2017, 5361251 (“Mohsin et al.”) describe the reaction of molten PET with ethylene glycol in an extruder. However, Mohsin et al. do not describe the use of ethylene glycol salts nor the presence of additional polymers in the PET.

[0016] B. Bergmann, W. Becker, J. Diemert, P. Elsner, Macromol. Symp. 2013, 333, 138-141 ("Bergmann et al.") describe the reaction of molten PET with ethylene glycol in an extruder and the analysis of the extruded product by near-infrared spectroscopy. The reaction scheme is identical to that described by Mohsin et al.

[0017] U. Thiele presented a report on methods for alcoholysis of PET diols in extruders, within the context of an overview of various methods for PET depolymerization, at the 5th China International Recycled Polyester Forum, held in Shanghai, China, from September 2 to 4, 2009. The report is available at http: / / www.ccfei.net / upfile / conference / 200909181532368708140.pdf ("Thiele"), last accessed on January 15, 2023.

[0018] JD Patterson, in his paper "Continuous Depolymerization of Poly(ethyleneterephthalate) via Reactive Extrusion" (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 method for the glycolysis of PET in an extruder on pages 60 et seq. This method also uses ethylene glycol, but not glycol salts. Patterson also cites G. Colomines, F. Rivas, M.-L. Lacoste, J.-J. Robin, Macromolecular Materials and Engineering 2005, 290, 710-720 ("Colomines et al."), which describes the glycolysis of PET with diethylene glycol and the use of the reaction product in polyurethane formulations.

[0019] 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.

[0020] US 3,884,850 describes a process for the depolymerization of PET, wherein PET is converted into BHET and low molecular weight oligomers of BHET.

[0021] The cracking of polyesters (eg, polyalkylene terephthalates) in typical polymer processing equipment (eg, extruders) is generally carried out at temperatures above the melting temperature of the polyester in order to plasticize the material.

[0022] It has been observed that during the hydrolysis, in particular the solvolysis, of polyalkylene terephthalates such as PET, PBT and similar polyesters in a melt (the melt also comprising polyolefins having a lower melting point than the polyesters, such as polyethylene PE or polypropylene PP), after the depolymerization has been completed and the reaction mixture has cooled, the corresponding polyolefins agglomerate in such a way that the corresponding agglomerates contaminate the plant and are difficult to separate from the crude product. This is disadvantageous because the depolymerization of the corresponding polyalkylene terephthalates proceeds very slowly at low temperatures, and the corresponding polyolefins are present in the reaction mixture in solid form from the outset, making it economically unfeasible.

[0023] The object of the present invention was therefore to provide an improved process for the depolymerization of polyalkylene terephthalates, such as PET and PBT in particular, in mixtures with polyolefins having a lower melting point than polyalkylene terephthalates, which does not have these problems. The process makes it possible, in particular, to remove the polyolefins efficiently and easily and to avoid sticky deposits in the apparatus used.

[0024] Surprisingly, a solution to the above-mentioned problem has now been found. Summary of the Invention

[0025] It has been found that, surprisingly, the problems of polyolefin aggregation and coagulation can be avoided when the depolymerization of the polyalkylene terephthalate (polymer P1) is carried out in two steps, wherein the first step is carried out at a temperature at which the polyolefin is in molten form. G1 The process is carried out in such a way that the polymer P1 is not completely cleaved into monomer units [corresponding to the compound of the formula (III) below], but rather preferentially into the largest proportion of oligomeric cleavage products P2.

[0026] The reaction solution obtained in the first step is then cooled to a temperature T at which the polyolefin is in a solidified state. b , then add a second portion P of at least one diol compound G G2 , in order to complete the depolymerization of polymer P1, the polyolefin is now in a solid state. The solid polyolefin can then be separated efficiently and with low complexity from the reaction solution obtained after the second step. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawing shows an embodiment of the method according to the invention.

[0028] In this figure, a waste stream at room temperature ("RT") containing PET, polyethylene (=PE) and sand as solid contaminant V is shown. <10> Feed to extruder E <3> In. It is also possible to use a kneader instead of an extruder.

[0029] In the extruder E <3> In the waste stream <10> PET and PE in the first shell <1> The PE / PET melt (corresponding to the mixture M1) was melted in a temperature range of 265°C to 300°C and degassed from the resulting PE / PET melt (corresponding to the mixture M1). <100> Remove volatile components <11> .

[0030] Then in the second shell <2> In the first part of ethylene glycol, P G1<12> Add to mixture M1 <100> In particular, a catalyst K1, such as sodium glycolate or sodium methoxide, is added together with the glycol, preferably in solid form. <2> PET is converted by glycolysis at a temperature of 190°C to 210°C, at which temperature PE is in molten form. <101> Due to the reaction between PET and ethylene glycol, <101> There are also "BHET oligomers" (corresponding to the following cleavage product P2, where a II =2, c II =0, ) and monomer units such as mono(2-hydroxyethyl) terephthalate MHET and bis(2-hydroxyethyl) terephthalate BHET. In addition, the melt <101> Also included is ethylene glycol.

[0031] In the shell <2> After the reaction, a mixture M2 containing not only BHET oligomers and monomer units but also solid pollutants V is obtained. <102> With the help of coarse filter <4> and fine filter <6> Using a pump <5> Remove coarse impurities from <13> and fine impurities <14> (down to 1 μm particle size), such as sand. After passing through the fine filter 6, the mixture M2 <102> In the reaction vessel <7> Cooling to a temperature T in the range of 120°C to 130°C b , which results in the solidification of the PE in the mixture. Add the second portion of ethylene glycol P G2 <15> Obtain mixture M3 <103> , which is further reacted with ethylene glycol in a stirred tank reactor <8> The reaction was further cleaved into the mixture M3 <103> BHET oligomers in this yield a mixture M4 containing monomer units such as BHET and MHET or terephthalic acid ("TS") <104> . Then you can use it in another filter <9> Separate the solidified PE from the mixture M4 <18> , without any great difficulty. Alternatively or additionally, from a stirred tank <8> Skim off the solidified PE <18> .

[0032] The coordinate system shown in the lower half of the figure shows the temperature t of the respective mixture (y-axis) and the process coordinate (process progress; x-axis). DETAILED DESCRIPTION

[0033] The process according to the invention is a process for depolymerizing at least one polymer P1.

[0034] The compounds BHET, MHET and TS mentioned in the context of the present invention have the following structures:

[0035]

[0036] "MHET" also encompasses the corresponding carboxylic acid esters of the shown structure.

[0037] "TS" also encompasses the corresponding mono- and dicarboxylates of the shown structure.

[0038] 1.Mixture M1

[0039] In step (a) of the process according to the invention, a mixture M1 is used which comprises

[0040] - at least one polymer P1,

[0041] - a melt of at least one polyolefin PO having a lower melting temperature than the at least one polymer P1,

[0042] - optionally at least one cleavage product P2,

[0043] - optionally at least one compound of formula (III).

[0044] Therefore, the method according to the invention is particularly suitable for processing waste materials containing polymer P1 (especially PBT and / or PET, preferably PET) and at least one polyolefin PO (preferably polyethylene PE or polypropylene PP, more preferably polyethylene PE). Such waste materials can be used as mixture M1 in step (a) of the method according to the invention.

[0045] The process according to the invention can therefore be used for processing scrap, in particular scrap comprising polyalkylene terephthalates and polyolefins having a lower melting temperature, preferably scrap comprising corresponding multilayer systems.

[0046] 1.1 Polymer P1

[0047] At least one polymer P1 comprises n1 interconnected repeating units of the following formula (I):

[0048]

[0049] a is an integer where 2≤a≤6, in particular a=2 or 4, preferably a=2.

[0050] b is an integer where 2≤b≤6, in particular b=2 or 4, preferably b=2.

[0051] c is an integer where 0≤c≤10, in particular c=0 or 1, preferably c=0.

[0052] n1 is an integer ≥50;

[0053] The n1 interconnected repeating units of the formula (I) comprised by the polymer P1 are identical or different, in particular identical.

[0054] The n1 interconnected repeating units of formula (I) are interconnected within polymer P1 in such a way that the bond marked "(i)" of one repeating unit of formula (I) is connected to the bond marked "(ii)" of an adjacent repeating unit of formula (I).

[0055] The process according to the invention is particularly suitable for the depolymerization of polymers P1 which at least partially contain segments of polyethylene terephthalate ["PET"; hereinafter option (β)] or portions of polybutylene terephthalate ["PBT"; hereinafter option (α)].

[0056] Therefore, one of the following embodiments (α) and (β) is preferred, with (β) being more preferred:

[0057] (α) The polymer P1 comprises n1 interconnected repeating units of the formula (I) wherein a=4 and c=0.

[0058] (β) The polymer P1 comprises n1 interconnected repeating units of the formula (I) wherein a=2 and c=0.

[0059] The end group of the first repeating unit of the n1 interconnected repeating units of polymer P1 present at the bond defined by “(i)” in structural formula (I) for the n1 interconnected repeating units of polymer P1, and the end group of the n1th repeating unit of the n1 interconnected repeating units of polymer P1 present at the bond defined by “(ii)” in structural formula (I) for the n1 interconnected repeating units of polymer P1 are not particularly limited and are the result of the method used in the production method of polymer P1.

[0060] For example, these end groups may be the terminal segments of the repeating units of formula (I), or may be one or more repeating units W X , where W X Different from structural formula (I).

[0061] Preferably, at least one of the two end groups is selected from:

[0062] -H;

[0063] -OH;

[0064] - optionally at least one group chosen from aliphatic groups containing -OH, -O- (which may in particular be chosen from alkyl groups containing -OH, -O-, optionally at least one such group);

[0065] - aromatic groups [such as, in particular, isophthalic acid groups of formula (VII) below];

[0066] - a heteroaromatic group.

[0067] More preferably, at least one, preferably two, of these end groups are selected from:

[0068] -H;

[0069] -OH;

[0070] - optionally at least one group selected from alkyl groups containing -OH, -O-;

[0071] - an isophthalic acid group of the following structural formula (VII).

[0072] More preferably, the terminal group connected to the bond marked "(i)" in formula (I) is selected from -H, -(CH2) a* -[O-(CH2) b* ] c* -OH.

[0073] a* is an integer where 2≤a*≤6, in particular a*=2 or 4, preferably a*=2.

[0074] b* is an integer where 2≤b*≤6, in particular b*=2 or 4, preferably b*=2.

[0075] c* is an integer, where 0≤c*≤10, in particular c*=0 or 1, preferably c*=0.

[0076] In addition, the terminal group connected to the bond marked as "(ii)" in structural formula (I) is preferably selected from -H, -OH, a group of structural formula (IV) or (VII), more preferably selected from -H, -OH, a group of structural formula (IV), and even more preferably selected from -OH, a group of structural formula (IV), wherein structural formulas (IV) and (VII) are as follows:

[0077]

[0078] The process according to the invention can therefore also be used for the depolymerization of polymers P1 which, in addition to n1 interconnected repeating units of formula (I), also comprise further repeating units W different therefrom. Y This is the case, for example, for polymers P1 comprising comonomer units, in particular recurring units such as those of formula (VI) below, wherein a, b, c have the above definitions:

[0079]

[0080] Thus, the polymer P1 according to the present invention includes any polymer comprising at least one segment A1 consisting of n1 interconnected repeating units of formula (I) which are identical or different, preferably identical, within the segment A1, and wherein the n1 interconnected repeating units of formula (I) are interconnected within the portion A1 in such a way that the bond marked “(i)” of one repeating unit of formula (I) is linked to the bond marked “(ii)” of an adjacent repeating unit of formula (I).

[0081] Besides n1 interconnected repeating units of the formula (I), the polymer P1 may also contain further (preferably organic) groups G F , which is not composed of repeating units of formula (I), for example, is composed of repeating units W different from formula (I) Z The oligomer or polymer part of the composition.

[0082] For example, a moiety A1 consisting of n1 interconnected repeating units of formula (I) can then be bonded to such an organic group G in the polymer P1 via a bond (i) to the first repeating unit of the n1 interconnected repeating units of formula (I) in the moiety A1 and / or via a bond (ii) to the n1th repeating unit of the n1 interconnected repeating units of formula (I) in the moiety A1. F connect.

[0083] Similarly, polymer P1 may also comprise two or more moieties A1, A2, etc., each consisting of n1 interconnected repeating units of formula (I) and connected via an organic group G different from formula (I). F linked to each other, for example by repeating units different from those of formula (I) The oligomer or polymer composed of these organic groups G F It is bonded to the bond (ii) of the n1th repeating unit of the first part A1 and to the bond (i) of the first repeating unit of the following part A2.

[0084] In a preferred embodiment of the present invention, polymer P1 has n1 interconnected repeating units of the formula (I), wherein the proportion of repeating units of the formula (I) in polymer P1, based in each case on the molar amount of polymer P1, is ≥50% by weight, in particular ≥60% by weight, preferably ≥70% by weight, more preferably ≥80% by weight, even more preferably ≥90% by weight, still more preferably ≥95% by weight and most preferably ≥99% by weight.

[0085] In the process according to the invention, the mixture M1 used in step (a) preferably comprises different polymers P1. In this embodiment, the individual polymers P1 generally have different degrees of polymerization, i.e., n1 is different for at least some of the polymers P1 present in the mixture M1 used in step (a).

[0086] In another preferred embodiment of the present invention, the mixture M1 used in step (a) comprises different polymers P1, wherein at least 10%, preferably at least 20%, more preferably at least 30%, even more preferably at least 50%, even more preferably at least 75%, most preferably at least 99% of all polymers P1 present in the mixture M1 used in step (a) comprise at least one part A1 consisting of repeating units of structural formula (I) with n1≥100 interconnected.

[0087] In a particularly preferred embodiment of the process according to the invention, at least one polymer P1 has the formula (I') wherein

[0088]

[0089] a' is an integer, where 2≤a'≤6, in particular a'=2 or 4, preferably a'=2.

[0090] b' is an integer where 2≤b'≤6, in particular b'=2 or 4, preferably b'=2.

[0091] c' is an integer, where 0≤c'≤10, in particular c'=0 or 1, preferably c'=0.

[0092] n'1 is an integer ≥49, preferably ≥50.

[0093] The polymer P1 having the structural formula (I') can also be represented as follows:

[0094] R'-(W'1) n'1 -R".

[0095] Thus, W'1 corresponds to the structure enclosed by a set of brackets with the subscript "n'1" in formula (I'). Thus, unit W'1 has the following structure:

[0096]

[0097] The n′1 units W′1 which are interconnected within the polymer P1 according to formula (I′) are identical to or different from one another within the polymer P1, in particular identical.

[0098] R' is selected from -H,

[0099] is an integer, where in particular or 4, preferably

[0100] is an integer, where in particular or 4, preferably

[0101] is an integer, where in particular or 1, preferably

[0102] R" is selected from -H, -OH, a group of formula (IV) or (VII), preferably selected from -H, -OH, a group of formula (IV), more preferably selected from -OH, a group of formula (IV), wherein formula (IV) and (VII) are as follows:

[0103]

[0104] The process according to the invention is particularly suitable for polyethylene terephthalate ("PET") and polyethylene

[0105] Depolymerization of butylene terephthalate ("PBT"). Thus, in a preferred embodiment, polymer P1 is selected from PET, PBT. Most preferably, polymer P1 is PET.

[0106] PBT corresponds to polymer P1 according to formula (I') wherein a'=4 and c'=0.

[0107] PET corresponds to polymer P1 according to formula (I') where a'=2 and c'=0.

[0108] In the process according to the invention, the mixture M1 used in step (a) preferably comprises different polymers P1 according to formula (I'). In this embodiment, the individual polymers P1 generally have different degrees of polymerization, i.e., n'1 is different for at least some of the polymers P1 according to formula (I') present in the mixture M1 used in step (a).

[0109] In another preferred embodiment of the present invention, the mixture M1 used in step (a) comprises different polymers P1 of structural formula (I'), wherein 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 mixture M1 used in step (a), n'1≥99, even more preferably n'1≥100.

[0110] The at least one polymer P1 contained in the mixture M1 used in step (a) may be in solid or molten form, preferably in solid form, more preferably in granular form. The material state of the at least one polymer P1 in the mixture M1 used in step (a) and in the mixture M1 during step (a) depends on the temperature T at which the mixture M1 is used or at which step (a) of the process according to the invention is carried out. a .

[0111] 1.2 Polyolefin PO

[0112] The mixture M1 used in step (a) comprises not only at least one polymer P1 but also a melt of at least one polyolefin PO.

[0113] Melting temperature T of polyolefin PO PO below the melting temperature T of the at least one polymer P1 comprised by the mixture M1 used in step (a) P1 .

[0114] At least one polyolefin PO is especially chosen from polyethylene ("PE"; PO : 135℃), polypropylene ("PP"; T PO : 160°C), polyisobutylene ("PIB"; T PO :54-56℃)、polybutene("PB";T PO : 135℃).

[0115] The at least one polyolefin PO is preferably selected from PE, PP.

[0116] More preferably, the at least one polyolefin PO is a polyethylene PE.

[0117] In which at least one polymer P1 is PET (T P1 :260℃) or PBT(T P1 : 223 ° C), especially in the embodiment of PET, the polyolefin PO is especially selected from PE, PP, PIB, PB, preferably selected from PE, PP; more preferably, PO = PE.

[0118] The ratio by weight of all polymers P1 comprised by the mixture M1 used in step (a) to the weight of all polyolefins PO comprised by the mixture M1 used in step (a) is not subject to any further restrictions and is in particular in the range from 99:1 to 1:99, preferably in the range from 98:2 to 10:90, more preferably in the range from 97:3 to 25:75, even more preferably in the range from 96:4 to 50:50, yet even more preferably in the range from 95:5 to 60:40, most preferably 95:5.

[0119] The temperature T at which step (a) of the method according to the invention is carried out a Preferably, the melting temperature T of polyolefin PO is PO At least 1°C higher, especially at least 2°C higher, preferably at least 5°C higher, more preferably at least 10°C higher, even more preferably at least 50°C higher.

[0120] Temperature T a Higher than the melting temperature T of polyolefin PO PO , and may also be above or below, preferably below, the melting temperature T of at least one polymer P1 P1 .

[0121] 2. Step (a)

[0122] In step (a) of the process according to the invention, a first portion P of at least one diol compound G is G1 Add to the mixture M1 used in step (a).

[0123] 2.1 Diol compound G

[0124] As the first part G1 The added diol compound G has the structural formula (V):

[0125] HO-(CH2) d -[O-(CH2) e ] f -OH.

[0126] d is an integer, where 2≤d≤6, in particular d=2 or 4, preferably d=2.

[0127] e is an integer where 2≤e≤6, in particular e=2 or 4, preferably e=2.

[0128] f is an integer, where 0≤f≤10, in particular f=0 or 1, preferably f=0.

[0129] As the first part G1 The added diol compound G is preferably selected from:

[0130] - ethylene glycol (=ethane-1,2-diol; CAS No.: 107-21-1; structural formula (V), where d=2, c=0);

[0131] -Butanediol (=butane-1,4-diol; CAS No.: 110-63-4; structural formula (V), where d=4, c=0);

[0132] -Diethylene glycol [= 2-(2-hydroxyethoxy)ethanol; CAS No.: 111-46-6; structural formula (V), wherein d = 2, e = 2, f = 1];

[0133] Ethylene glycol is particularly preferred.

[0134] In a preferred embodiment of the present invention, as the first part P G1 The diol compound G added is at least one of the products of depolymerization of the polymer P1 of the present invention.

[0135] Thus, when the polymer P1 at least partially comprises segments of polyethylene terephthalate PET, and more preferably still when the polymer P1 is PET, as the first part P G1 The diol compound G to be added is preferably ethylene glycol.

[0136] Thus, when the polymer P1 at least partially comprises segments of polybutylene terephthalate PBT, and more preferably still when the polymer P1 is PBT, as the first part P G1 The diol compound G to be added is preferably butanediol.

[0137] 2.2 Reaction conditions in step (a)

[0138] In step (a) of the process according to the invention, a first portion P of at least one diol compound G is G1 is added to the mixture M1. In the mixture M1, the diol compound G then at least partially reacts with at least a portion of the polymer P1 to obtain at least one cleavage product P2, and after step (a) the mixture M2 is obtained.

[0139] In particular, the reaction according to step (a) of the process according to the invention is carried out until the weight of all polymers P1 in the mixture M2 obtained after the end of step (a), based in each case on the weight of all polymers P1 in the mixture M1 used in step (a), has fallen 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, still more preferably at least 60% by weight, still more preferably at least 70% by weight, still more preferably at least 80% by weight, still more preferably at least 90% by weight and most preferably at least 98% by weight.

[0140] Preferably, the water content in the mixture M1 during the reaction according to step (a) and in the mixture M2 obtained after the end of step (a) is at a minimum, so that in the reaction of the diol compound G with the polymer P1, the proportion of solvolytic transesterification is at a maximum and the proportion of hydrolytic ester cleavage is at a minimum. These two different reactions are shown in the following Scheme 1.

[0141] As is apparent from Scheme 1, polymer P1 (represented in the middle by a segment from formula (I')) undergoes solvolytic transesterification upon reaction with a diol compound G to give two cleavage products P2 (lower half of Scheme 1). The terminal carboxylic acid groups of the two cleavage products obtained are esterified with G (last row of Scheme 1, cleavage product P2, left side) or with the alkylene glycol units present in P1 (last row of Scheme 1, cleavage product P2, right side). If cleavage product P2 or the compound of formula (III) produced therefrom after the conversion in step (c) is polymerized again to give polymer P1, these ester groups can be more readily converted into polymer P1, and are therefore advantageous cleavage products P2.

[0142] Route 1

[0143]

[0144] For example, in the glycolysis of PET with ethylene glycol, the desired bis(2-hydroxyethyl)terephthalate, BHET, diester is formed.

[0145] In contrast, the presence of water in the mixture M1 during the reaction according to step (a) leads to hydrolytic cleavage of the polymer P1 and formation of unfavorable cleavage products P2.

[0146] This is shown in the upper half of Scheme 1. This produces two cleavage products P2, one of which carries a free (i.e., unesterified) carboxylic acid group at the end (first line of Scheme 1, cleavage product P2, left side). Converting such cleavage products P2 into new polymers P1 is expensive and inconvenient, and therefore disadvantageous. The hydrolysis of PET forms the main product TS, as well as 2-hydroxyethyl terephthalate MHET monoester.

[0147] It is therefore advantageous to keep the water content in the mixture M1 as low as possible during the reaction according to step (a).

[0148] In a preferred embodiment of the present invention, during the reaction according to step (a), the water content in the mixture M1 is therefore <10% by weight, more preferably <5% by weight, even more preferably <1% by weight, even more preferably <0.1% by weight and most preferably <0.01% by weight, based in each case on the total weight of the mixture M1.

[0149] As the first part G1 The proportion of the at least one diol compound G added to the mixture M1 is not subject to any further restrictions. It is advantageous to cleave the polymer P1 in step (a) to a maximum proportion of cleavage products P2 and then only in step (c) to further convert these cleavage products P2 into compounds of the formula (III). This is advantageously done via the first part P1. G1The amount of at least one diol compound G added to the mixture M1 is controlled.

[0150] In a preferred embodiment of the process according to the invention, the first part P in step (a) is preferably methyl ... G1 The molar amount of all diol compounds G added to the mixture M1 is ≥0.01 molar equivalents, more preferably in the range of 0.01 to 25 molar equivalents, even more preferably in the range of 0.01 to 5 molar equivalents, even more preferably in the range of 0.01 to 3 molar equivalents, even more preferably in the range of 0.01 to 1 molar equivalents, even more preferably in the range of 0.02 to 0.9 molar equivalents, even more preferably in the range of 0.03 to 0.8 molar equivalents, even more preferably in the range of 0.04 to 0.7 molar equivalents, still more preferably in the range of 0.05 to 0.6 molar equivalents, still more preferably in the range of 0.06 to 0.5 molar equivalents, still more preferably in the range of 0.07 to 0.4 molar equivalents, still more preferably in the range of 0.08 to 0.3 molar equivalents, still more preferably in the range of 0.09 to 0.2 molar equivalents, and most preferably in the range of 0.09 to 0.1 molar equivalents.

[0151] The process according to the invention is preferably carried out as a solvolysis in order to minimize as much as possible the proportion of undesirable products (such as TS or MHET in the case of PET hydrolysis) in the reaction products and to maximize the proportion of desired products (such as BHET in the case of PET and ethylene glycol solvolysis) in the reaction products.

[0152] Therefore, preferably, based on the first part P in step (a) G1 The first part P of at least one diol compound G added in step (a) is based on the total weight of all diol compounds G added. G1 The water content is <10 wt.-%, more preferably <5 wt.-%, even more preferably <1 wt.-%, still more preferably <0.1 wt.-%, most preferably <0.01 wt.-%.

[0153] Step (a) at temperature T a The temperature T a higher than the melting temperature T of the at least one polyolefin PO contained in the mixture M1 used in step (a) POThus, the polyolefin PO during step (a) is in the form of a melt, in which the reaction according to step (a) can advantageously be carried out. Under the reaction conditions of step (a) or step (c), the polyolefin PO is inert in the mixture M1 or in the mixture M3, i.e. it does not react substantially with the diol compound G. The temperature T can also be selected a , so that the temperature is lower or higher than the melting temperature T of at least one polymer P1 during step (a) P1 The temperature T during step (a) is preferably selected to be a , so that at the beginning of step (a), the temperature is higher than T at the beginning of the addition of G P1 , and decreases to below T during the reaction of step (a) P1 (but of course higher than T PO ) value.

[0154] If the temperature T a below the melting temperature T of at least one polymer P1 P1 , which means that T a At the melting temperature T of polyolefin PO PO and the melting temperature T of at least one polymer P1 P1 The at least one polymer P1 is then at least partially, preferably completely, a substance in the solid state in the mixture M1.

[0155] If the temperature T a Above the melting temperature T of at least one polymer P1 P1 , which means that T a Higher than the melting temperature T of polyolefin PO PO and above the melting temperature T of at least one polymer P1 P1 Both the at least one polymer P1 and the polyolefin PO are then in the form of a melt in the mixture M1.

[0156] When the at least one polymer P1 is selected from PBT and PET, the temperature T a Preferably, the temperature is in the range of 165°C to 270°C, more preferably in the range of 170°C to 265°C, still more preferably in the range of 180°C to 220°C, and most preferably in the range of 190°C to 210°C. This is particularly true when the polyolefin PO is selected from polyethylene ("PE"; T PO : 135℃), polypropylene ("PP"; T PO : 160°C), polyisobutylene ("PIB"; T PO :54-56℃)、polybutene("PB";T PO : 135 ° C), more preferably when the polyolefin PO is selected from PE and PP.

[0157] When PO=PE and at least one polymer P1 is selected from PBT and PET, preferably, P1=PET; in another embodiment, the temperature T a It is preferably in the range of 140°C to 270°C, more preferably in the range of 165°C to 270°C, more preferably in the range of 170°C to 265°C, still more preferably in the range of 180°C to 220°C, and most preferably in the range of 190°C to 210°C.

[0158] Step (a) of the process according to the invention is preferably carried out at least partially in a kneader or an extruder E, preferably in an extruder E.

[0159] Extruders are familiar 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 mean a machine which receives a solid to liquid molding compound (usually inside the extruder) and extrude this molding compound primarily continuously from a product outlet (or "opening"), in particular a die (according to DIN 24450: 1987-02); see Somborn R, Extruder, RD-05-02432 (2004) in F.,Dill B.,Eisenbrand G.,Faupel F.,Fugmann B.,Gamse T.,Matissek R.,Pohnert G.,Rühling A.,Schmidt S.,Sprenger G., [Online], Stuttgart, Georg Thieme Verlag, [December 2022]; available online at https: / / roempp.thieme.de / lexicon / RD-05-02432, last accessed 22 December 2022.

[0160] The extruder E used in a preferred embodiment is a piston extruder or a multi-shaft extruder, particularly preferably a multi-shaft extruder.

[0161] Preferred multi-shaft extruders are planetary roller extruders or multi-screw extruders. The multi-screw extruder is especially a twin-screw extruder.

[0162] 2.3 Pyrolysis product P2

[0163] In step (a) of the process according to the invention, at least a portion of the polymer P1 in the mixture M1 is at least partially reacted with the diol compound G to obtain at least one cleavage product P2. The cleavage product P2 has the structural formula (II):

[0164]

[0165] a II is an integer where 2≤a II ≤6, especially a II =2 or 4, preferably a II =2.

[0166] b II is an integer where 2≤b II ≤6, especially b II =2 or 4, preferably b II =2.

[0167] c II is an integer where 0≤c II ≤10, especially c II =0 or 1, preferably c II =0.

[0168] n2 is an integer, where 2≤n2≤48.

[0169] Structural formula (II) can also be expressed as "R II1 -(W2) n2 -R II2 ”. Therefore, W2 corresponds to the structure enclosed by a set of brackets with the subscript “n2” in structural formula (II):

[0170]

[0171] The n2 repeating units W2 interconnected in the cleavage product P2 can be identical or different in the cleavage product P2. This means that the molecules P2 can have identical or different groups W2 (i.e., for example, with different a II 、b II and / or c II value).

[0172] R II1 Selected from -H,

[0173] is an integer, where in particular or 4, preferably

[0174] is an integer, where in particular or 4, preferably

[0175] is an integer, where in particular or 1, preferably

[0176] R II2 A group selected from -H, -OH, and a group of formula (IV), preferably a group selected from -OH and a group of formula (IV), wherein the formula (IV) is as follows:

[0177]

[0178] According to the present invention, the cleavage product P2 of formula (II) (wherein a II =2;c II =0; ) are also referred to as "BHET oligomers" or "oligomers of BHET".

[0179] The molar amounts of the cleavage products P2 and polymer P1 in a given mixture, in particular in one of the mixtures M1, M2, M3 and M4, can be determined by test methods known to those skilled in the art. According to the invention, the molecular weight distribution (and therefore the average degree of polymerization p) of polymer P1 and cleavage products P2 is determined by gel permeation chromatography ("GPC") according to Method 1 (see Examples). According to the invention, this method is also used to determine the distribution of the average degree of polymerization p over all polymers P1 or all cleavage products P2 in a given mixture, in particular in one of the mixtures M1, M2, M3 and M4.

[0180] The content of compound (III) in a given mixture, in particular in one of the mixtures M1, M2, M3 and M4, can be determined by test methods known to those skilled in the art, preferably via nuclear magnetic resonance ("NMR") or chromatography.

[0181] Consequently, after step (a) has concluded, a mixture M2 is obtained which comprises a melt of at least one cleavage product P2 and at least one polyolefin PO.

[0182] 2.4 Catalyst K1

[0183] Advantageously, the reaction of the diol compound G with the polymer P1 in the mixture M1 in step (a) is carried out in the presence of at least one catalyst K1.

[0184] The catalyst K1 can already be present in the mixture M1 before the addition of the at least one diol compound G, be added to the mixture M1 after the addition of the at least one diol compound G, and / or be added together with the at least one diol compound G to the mixture M1.

[0185] The catalyst K1 can be selected by those skilled in the art on the basis of their knowledge in the field.

[0186] Catalyst K1 is preferably selected from carbonates, bicarbonates, metal halides, amines, alkoxides, acetates, phosphates, dibutyltin oxide, more preferably selected from amines, alkoxides, acetates; still more preferably, catalyst K1 is an alkoxide, still more preferably an alkali metal alkoxide.

[0187] Preferred acetates are selected from lead acetate and zinc acetate, with zinc acetate being more preferred.

[0188] Preferred phosphates are the alkali metal phosphates, especially sodium phosphate.

[0189] The preferred metal halide is zinc chloride.

[0190] Preferred carbonates are alkali metal carbonates or alkaline earth metal carbonates, especially alkali metal carbonates, preferably sodium carbonate.

[0191] Preferred bicarbonates are alkali metal bicarbonates or alkaline earth metal bicarbonates, especially alkali metal bicarbonates, preferably sodium bicarbonate.

[0192] The amines used are preferably trialkylamines, for example trimethylamine, triethylamine, dimethylethylamine, di(isopropyl)ethylamine ("DIPEA") or cyclic amines, such as, in particular, 1,5,7-triazabicyclo[4.4.0]dec-5-ene ("TBD") or 1,8-diazabicyclo[5.4.0]undec-7-ene ("DBU"). These have the following structural formula:

[0193]

[0194] TBD is described in K. Fukushima, O. Coulembier, JMLecuyer, HA Almegren, AMA Labdulrahman, FDAlsewailem, MA McNeil, P. Dubois, RM Waymouth, HW Horn, JERice, JL Hedrick, Journal of Polymer Science Part A: Polymer Chemistry 2011, 49, 1273-1281.

[0195] B. Allen, G. Breyta, J. Garcia, G. Jones, and J. Hedrick presented trialkylamines DBU and TBD at the conference “Polyester Digestion: VOLCAT. Summit on Realizing the Circular Carbon Economy,” held in San Jose, California, USA, on July 24, 2018 (slides available at https: / / www.energy.gov / sites / prod / files / 2018 / 10 / f56 / Robert_Allen_CCE_Panel Day1_0.pdf; last accessed January 15, 2023).

[0196] If the catalyst K1 used is an alkoxide, in particular an alkali metal alkoxide, it is preferably used in solid form, for example in the form of a powder or granules.

[0197] Preferred alkoxides are alkali metal alkoxides wherein the alcohol is a monohydric or dihydric alcohol having 1 to 6 carbon atoms.

[0198] Still more preferred alkali metal alkoxides are those wherein the alkoxide is selected from the group consisting of:

[0199] - methoxide;

[0200] - ethanol salts;

[0201] -Propanolate, meaning n-propoxide or isopropoxide;

[0202] - butoxides, in particular n-butoxide;

[0203] -pentanolates, in particular n-pentanolate;

[0204] - hexanolates, in particular n-hexanolate;

[0205] - glycol salts;

[0206] More preferably, it is selected from methoxide, ethanolate, and glycolate, still more preferably, it is selected from methoxide and ethanolate, and most preferably, it is selected from methoxide.

[0207] In the context of the present invention, "glycol salts" are understood to mean the corresponding salts of ethylene glycol. A -ethylene glycol salt" (where M A is an alkali metal) including 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 MA O-CH2-CH2-OH and M A O-CH2-CH2-OM A .

[0208] Preferred alkali metals here are lithium, sodium, potassium, more preferably sodium, potassium, still more preferably sodium.

[0209] In a particularly preferred embodiment, the catalyst K1 is selected from sodium ethylene glycol, potassium ethylene glycol, potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, more preferably selected from potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, and even more preferably selected from sodium methoxide, potassium ethoxide, sodium ethoxide; particularly preferably, K1 = sodium methoxide.

[0210] The alkali metal alkoxides which can be used as catalysts K1 and K2 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, for example, in EP 1997 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.

[0211] The alkali metal alkoxides usable as catalysts K1 and K2 in the process according to the invention can alternatively be prepared by transalcoholization of the corresponding alcohol with another alkoxide. For example, CS 213119 B1, GB 490,388 A, DE 689 03 186 T2 and EP 0 776 995 A1 describe the corresponding preparation of alkali metal alkoxides.

[0212] WO 2021 / 122702 A1, DE 27 26 491 A1, DE 1 254 612 B describe alcohol transhydration reactions by reactive distillation, which likewise give alkoxides, in particular alkali metal alkoxides, which can be used as catalyst K1 (or as catalyst K2) in the process according to the invention.

[0213] The alkoxides usable according to the invention as catalysts K1 and K2 can also be prepared 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, WO 2023 / 274794 A1.

[0214] The amount of catalyst K1 used in step (a) can be selected by those skilled in the art based on their knowledge in the art. G1 The molar amount of all catalysts K1 used in step (a), based on the molar amount of all diol compounds G added, is in particular in the range from 0.01% to 10%, preferably in the range from 0.1 to 5%, more preferably in the range from 1 to 4%, still more preferably in the range from 2.5 to 3.5%, and particularly preferably 3%.

[0215] 2.5 Mixture M2

[0216] After step (a) of the process according to the invention is completed, a mixture M2 is obtained. It comprises at least one pyrolysis product P2 and a melt of at least one polyolefin PO. Since the mixture M2 comprises a melt of at least one polyolefin PO, the mixture M2 will be at a temperature above the melting temperature T of the polyolefin PO. PO The exact temperature at which the mixture M2 is obtained after step (a) is completed may be, but is not necessarily, the temperature T at which the reaction in step (a) occurs. a It is important for the present invention that the mixture M2 is above the melting temperature T of the polyolefin PO. PO In a preferred embodiment, the mixture M2 after step (a) is at a temperature T at which the reaction in step (a) is carried out. a Down.

[0217] The mixture M2 may also comprise at least one polymer P1. This is the case, for example, when not all of the polymer P1 comprised in the mixture M1 used in step (a) of the process according to the invention is reacted with the diol compound G, in particular when the diol compound G is used in step (a) in a molar deficit, based on the repeating units of the formula (I) comprised in the polymer P1 in the mixture M1 used in step (a).

[0218] The mixture M2 may also contain at least one compound of the formula (III). This is the case, for example, when at least one polymer P1 is reacted with at least one diol compound G in the reaction in step (a) to give cleavage products P2 and a compound of the formula (III).

[0219] The mixture M2 may also comprise at least one diol compound G.

[0220] This is the case at least if the molar amount of all cleavage products P2 in the mixture M2 after step (a) is greater than the molar amount of all cleavage products P2 in the mixture M1 used in step (a). This is the case regardless of whether the mixture M1 used in step (a) contains cleavage products P2 or not.

[0221] This is simply because, in step (a) of the process according to the invention, at least a portion of the polymer P1 in the mixture M1 reacts with at least one diol compound G to give at least one cleavage product P2. G1 The amount of diol compound G added or the reaction time), a person skilled in the art can also set the conditions so as to obtain the maximum amount of cleavage product P2 in M2, for example by preventing P2 from further reacting with G in step (a) to obtain the compound of formula (III). This further reaction preferably occurs essentially only in step (c).

[0222] In a preferred embodiment of the present invention, the ratio of the molar amount of all cleavage products P2 of the formula (II) in the mixture M1 used in step (a) to the molar amount of all polymers P1 in the mixture M1 used in step (a) is therefore <1:99 [which also includes the case where no cleavage products P2 of the formula (II) are present in the mixture M1 used in step (a)], and in step (b) a second portion P of at least one diol compound G is added. G2 In the case of all the cracking products P2 of the formula (II) in the mixture M2 and the second part P of at least one diol compound G added in step (b) G2 The molar ratio of all polymers P1 in the mixture M2 is ≥1:99, preferably ≥1:9, more preferably ≥1:4, more preferably ≥2:3, more preferably ≥1:1, more preferably ≥3:2, more preferably ≥4:1, more preferably ≥9:1, more preferably ≥99:1 (which in each case also includes the absence of polymer P1 in the mixture M2).

[0223] In another preferred embodiment of the present invention, the ratio of the molar amount of all cleavage products P2 of the formula (II) in the mixture M1 used in step (a) to the molar amount of all polymers P1 in the mixture M1 used in step (a) is <1:9 [which also includes the case where no cleavage product P2 of the formula (II) is present in the mixture M1 used in step (a)], and a second portion P of at least one diol compound G is added in step (b). G2 In the case of all the cracking products P2 of the formula (II) in the mixture M2 and the second part P of at least one diol compound G added in step (b) G2 The ratio of the molar amounts of all polymers P1 in the mixture M2 is ≥1:9, more preferably ≥1:4, more preferably ≥2:3, more preferably ≥1:1, more preferably ≥3:2, more preferably ≥4:1, more preferably ≥9:1, more preferably ≥99:1 (which in each case also includes the absence of polymer P1 in the mixture M2).

[0224] In another preferred embodiment of the present invention, the ratio of the molar amount of all cleavage products P2 of the formula (II) in the mixture M1 used in step (a) to the molar amount of all polymers P1 in the mixture M1 used in step (a) is <1:4 [which also includes the case where no cleavage product P2 of the formula (II) is present in the mixture M1 used in step (a)], and a second portion P of at least one diol compound G is added in step (b). G2 In the case of all the cracking products P2 of the formula (II) in the mixture M2 and the second part P of at least one diol compound G added in step (b) G2 The molar ratio of all polymers P1 in the mixture M2 is ≥1:4, more preferably ≥2:3, more preferably ≥1:1, more preferably ≥3:2, more preferably ≥4:1, more preferably ≥9:1, more preferably ≥99:1 (which in each case also includes the absence of polymer P1 in the mixture M2).

[0225] In another preferred embodiment of the present invention, the ratio of the molar amount of all cleavage products P2 of the formula (II) in the mixture M1 used in step (a) to the molar amount of all polymers P1 in the mixture M1 used in step (a) is <2:3 [which also includes the case where no cleavage product P2 of the formula (II) is present in the mixture M1 used in step (a)], and a second portion P of at least one diol compound G is added in step (b). G2 In the case of all the cracking products P2 of the formula (II) in the mixture M2 and the second part P of at least one diol compound G added in step (b) G2 The molar ratio of all polymers P1 in the mixture M2 is ≥2:3, more preferably ≥1:1, more preferably ≥3:2, more preferably ≥4:1, more preferably ≥9:1, more preferably ≥99:1 (which in each case also includes the absence of polymer P1 in the mixture M2).

[0226] In another preferred embodiment of the present invention, the ratio of the molar amount of all cleavage products P2 of the formula (II) in the mixture M1 used in step (a) to the molar amount of all polymers P1 in the mixture M1 used in step (a) is <1:1 [which also includes the case where no cleavage product P2 of the formula (II) is present in the mixture M1 used in step (a)], and a second portion P of at least one diol compound G is added in step (b). G2 In the case of all the cracking products P2 of the formula (II) in the mixture M2 and the second part P of at least one diol compound G added in step (b) G2The molar ratio of all polymers P1 in the mixture M2 is ≥1:1, more preferably ≥3:2, more preferably ≥4:1, more preferably ≥9:1, more preferably ≥99:1 (which in each case also includes the absence of polymer P1 in the mixture M2).

[0227] In another preferred embodiment of the present invention, a second portion P of at least one diol compound G is added in step (b). G2 When the mixture M2 comprises a mixture of cleavage products P2. In step (b), a second portion P of at least one diol compound G is added. G2 When the mixture M2 contains all polymer molecules P2, the average degree of polymerization ρ is in the range of 2 to 30, more preferably 3 to 20, even more preferably 4 to 10.

[0228] In an optional embodiment of the present invention, in which the mixture M2 obtained after step (a) further comprises at least one polymer P1, at least one of the following two conditions (α*), (β*) is preferably satisfied, more preferably at least the condition (β*) is satisfied, and preferably both the conditions (α*) and (β*) are satisfied:

[0229] (α*) adding a second portion P of at least one diol compound G in step (b) G2 The average degree of polymerization of all polymers P1 contained in the mixture M2 is ρ 12 Lower than the average degree of polymerization ρ of all polymers P1 contained in the mixture M1 used in step (a) 11 ;

[0230] (β*) adding a second portion P of at least one diol compound G in step (b) G2 The molar amount of all polymers P1 contained in the mixture M2 is less than the molar amount of all polymers P1 contained in the mixture M1 used in step (a).

[0231] 2.6 Degree of polymerization π, average degree of polymerization ρ

[0232] In the context of the present invention, the term "degree of polymerisation π" refers to a single molecule of the polymer P1 or a single molecule of the cleavage product P2.

[0233] In the case of polymer P1, the degree of polymerization π gives the number of repeating units of the following structural formula W3 within the molecule P1 in question, wherein the repeating units of structural formula W3 are linked to each other such that the bond identified by "($)" of one repeating unit of structural formula W3 is linked to the bond identified by "($$)" in the adjacent repeating unit of structural formula W3.

[0234]

[0235] Here, a” is an integer, 2≤a”≤6.

[0236] Here, b” is an integer, 2≤b”≤6.

[0237] Here c” is an integer, 0≤c”≤10.

[0238] In other words: To determine the degree of polymerization π of a polymer molecule P1 according to the invention, all repeating units of the formula W3 in the polymer molecule P1 in question are counted in the sections in which at least two repeating units of the formula (I) are interconnected. The sum of the repeating units W3 contained in all sections then gives the degree of polymerization π of the polymer molecule P1.

[0239] In the preferred embodiment in which the polymer P1 has the formula (I'), the degree of polymerization π gives the number of recurring units of the formula W3 in the polymer P1.

[0240] In the case of the cleavage product P2, the degree of polymerization π denotes the number of repeating units of the formula W3 within the cleavage product P2.

[0241] The "average degree of polymerization p" relates to the polymer molecules P1 contained in a composition (e.g., the respective mixture M1, M2, M3, or M4) or to all cleavage products P2 contained in a composition (e.g., the respective mixture M1, M2, M3, or M4). The size distribution of the polymers P1 or cleavage products P2, from which the average degree of polymerization p can be calculated, is determined according to the invention by method 1 described in the examples.

[0242] Given a mixture M X The average degree of polymerization ρ1 of all polymer molecules P1 in P1 )] / n P1 , where “Σ(π P1 )" is a mixture M X The sum of the degrees of polymerization π of all polymer molecules P1 in the P1 It's M X The molar amount of all polymer molecules P1 contained.

[0243] Given a mixture M X The average degree of polymerization ρ2 of all the pyrolysis products P2 is the quotient [Σ(π P2 )] / n P2 , where “Σ(π P2 )" is a mixture M X The sum of the polymerization degrees π of all the cleavage product molecules P2, and n P2 It's M X The molar amount of all cleavage product molecules P2 contained.

[0244] 3. Step (b)

[0245] In step (b) of the process according to the invention, the mixture M2 obtained after step (a) is cooled to a temperature T below the melting temperature of the at least one polyolefin PO. b ,

[0246] Wherein, the mixture M2 is cooled to a temperature T b During and / or after, the second part P of at least one diol compound G of formula (V) G2 Add to mixture M2.

[0247] After completion of step (b), this gives a mixture M3 comprising:

[0248] - at least one cleavage product P2,

[0249] - at least one polyolefin PO in the solid state,

[0250] - at least one diol compound G,

[0251] - Optionally at least one polymer P1.

[0252] The mixture M3 obtained after step (b) is then further converted in step (c). It has been found that, surprisingly, in the process according to the invention, the second reaction [in step (c)] of converting the cleavage product P2 into a compound of formula (III) is advantageously carried out in a reaction mixture in which the polyolefin PO is in a solid state. This means that step (c) according to the invention is carried out at a temperature below the melting temperature T of the polyolefin PO. PO Temperature T c The temperature here is T c Can be compared with temperature T b Same, but can also be higher or lower, provided that T c Below the melting temperature of PO.

[0253] The solid polyolefin PO can then be separated more easily and efficiently from the mixture M4 obtained after the end of step (c) compared to the comparative process in which the solid polyolefin PO is continuously added to the mixture M4 at a temperature always > T PO The invention relates to the conversion of at least one polymer P1 into a compound of formula (III) by adding one or two portions of at least one diol compound G to a reaction mixture at a temperature of 100°C (100°F), i.e., in a reaction mixture in which PO is always in molten form, and cooling the reaction mixture to a temperature below the melting temperature of PO only after the reaction is complete. These conditions, which are not in accordance with the invention, result in a crude product in which the polyolefin PO is in solid form, but in the form of sticky masses that are difficult to separate from other desired components of the crude product (e.g., the compound of formula (III)) and from the plant itself.

[0254] The process according to the invention is advantageously controlled here so that step (a) consists essentially of mixing the polymer P1 comprised by the mixture M1 used in step (a) with the polymer P1 as a first part P G1 The at least one diol compound G added is reacted to obtain a cleavage product P2, and then step (c) essentially comprises reacting the cleavage product P2 present in the mixture M3 with the cleavage product P2 obtained as the second part P in step (b). G2 The at least one diol compound G added is reacted to give at least one compound of formula (III). In the context of the present invention, this distribution of the co-reactants of the separately added diol compound G can be controlled by a person skilled in the art, for example, by G1 or the second part P G2 The amount of the at least one diol compound G added (based on the repeating units of the formula W3 comprised by all polymers P1 in M1 or all cleavage products P2 in M2) or via the reaction time in step (a).

[0255] Therefore, it is advantageous and preferred to control the process according to the invention in such a way that the reaction of the cleavage product P2 with the at least one diol compound G does not take place substantially until step (c) in the presence of solid PO. This can be achieved, for example, by cooling to a temperature T b During this period, only when the mixture M2 is below the melting temperature T of the polyolefin PO PO Then the second portion P of at least one diol compound G is G2 Add to the mixture M2 in step (b) for control.

[0256] As described above, after step (a) of the method according to the present invention is completed, at a temperature above the melting temperature T PO In step (b), M2 is cooled to a temperature T below the melting temperature of the polyolefin PO. b It is therefore obvious that the mixture M2 during step (b) will at some point have the melting point T of the polyolefin PO. PO (Then it will be below the melting point).

[0257] In the context of the present invention, "cooling the mixture M2 to a temperature below the melting temperature T PO Temperature T b " also includes first cooling the mixture M2 to a temperature T b* <T b , then from T b* Heating to T b implementation plan.

[0258] After step (b) of the process according to the invention has concluded, the temperature of the mixture M3 is below the melting temperature TPO (since this is a prerequisite for at least one polyolefin PO to be in the solid state), and may be equal to or different from the temperature T b .

[0259] In step (b), the mixture M2 is cooled to a temperature T b During and / or after, the second portion P of at least one diol compound G G2 Add to mixture M2.

[0260] In particular, in step (b), after the mixture M2 has been cooled to a temperature T b Then, the second portion P of the at least one diol compound G is G2 This is the most advantageous way of ensuring that the reaction of step (c) proceeds completely in the mixture M2 in which the at least one polyolefin PO is in the solid state.

[0261] "The mixture M2 is cooled to a temperature below the melting temperature T of at least one polyolefin PO PO Temperature T b , while cooling the mixture M2 to a temperature T b period , the second part P of at least one diol compound G G2 Addition to the mixture M2) (abbreviated as "embodiment Ω") encompasses the following embodiments / options i., ii.:

[0262] i. Cooling the mixture M2 to a temperature T b During this period, the second portion P of at least one diol compound G is added G2 Add completely to the mixture M2, provided that the temperature of the mixture M2 is higher than the melting temperature T of the polyolefin PO PO ;

[0263] ii. Cooling the mixture M2 to a temperature T b During this period, the second portion P of at least one diol compound G is added G2 A portion of (= option ii.-A) or the entire second portion P of at least one diol compound G G2 (=option ii.-B) is added to the mixture M2, provided that the mixture M2 is below the melting temperature T of the at least one polyolefin PO PO at a temperature of 100°C.

[0264] Option ii. is more preferred than option i. because option ii. ensures that in step (c) as part of P G2 The entirety of the at least one diol compound G added is converted more completely, ie completely in the mixture in which the polyolefin PO is in solid form.

[0265] In option (ii), option (ii-B) is more preferable than option (ii-A) for the same reasons.

[0266] Option i. and option ii-A of embodiment "Ω" are preferably carried out when the mixture M2 used in step (b) still has a relatively high proportion of polymer P1 that was not converted in step (a), preferably when ψ ≥ 40%, more preferably when ψ ≥ 50%, even more preferably when ψ ≥ 60%, even more preferably when ψ ≥ 70%, even more preferably when ψ ≥ 80%. In all these embodiments, ψ < 1, since otherwise no conversion would occur in step (a).

[0267] ψ represents the second portion P of at least one diol compound G added in step (b) G2 The quotient of the molar amount of all polymers P1 in the mixture M2 and the molar amount of all polymers P1 in the mixture M1 used in step (a) is denoted by

[0268] When M2 is below the melting temperature T PO The second portion P of at least one diol compound G is previously G2 This preferred embodiment, in which at least part of the polymer P1 is added to the mixture M2, is advantageous in particular when the mixture M2 still comprises a considerable residual proportion of polymer P1.

[0269] In the embodiment Ω option ii.-A, as the second part P G2 The molar amount of all diol compounds G added to M2 (provided that the temperature of the mixture M2 is higher than T PO ) and as the second part P G2 The molar amount of the diol compound G added to M2 (provided that the temperature of the mixture M2 is lower than T PO ) is in the range of 99:1 to 1:99, especially in the range of 9:1 to 1:99, preferably in the range of 4:1 to 1:99, more preferably in the range of 3:2 to 1:99, still more preferably in the range of 1:1 to 1:99, still more preferably in the range of 2:3 to 1:99, still more preferably in the range of 1:4 to 1:99, still more preferably in the range of 1:90 to 1:99.

[0270] After completion of step (b), mixture M3 is then obtained.

[0271] For the reasons stated above, it is recommended that the mixture M2 be cooled to a temperature T b is lower than the melting temperature T of at least one polyolefin PO When the cleavage product P2 is reacted with at least one diol compound G.

[0272] In the case of option i. and option ii-A of embodiment "Ω", it is therefore preferred to control the process according to the invention so that χ ≥ 40%, more preferably χ ≥ 50%, even more preferably χ ≥ 60%, even more preferably χ ≥ 75%, even more preferably χ ≥ 85%, most preferably χ ≥ 90%.

[0273] χ is the quotient (n Z1 / n Z2 ).

[0274] Here n Z1 When the temperature of the mixture M2 is cooled to T b The melting temperature of polyolefin PO is T PO At time Z1 ("time Z1"), the molar amount of all cleavage products P2 contained in the mixture M2.

[0275] Here n Z2 is to add a second portion P of at least one diol compound G in step (b) G2 At time Z2 ("time Z2"), the molar amount of all cleavage products P2 contained in the mixture M2.

[0276] It is obvious that in options i. and ii-A. of implementation “Ω”, time Z2 is before Z1.

[0277] In this preferred embodiment, it is ensured that in options i. and ii-A. of embodiment "Ω", the reaction mixture is heated at a temperature below the melting temperature T of the polyolefin PO in step (b). PO Before that, first make a very small proportion of the cleavage product P2 and as the second part P G2 The added diol compound G reacts.

[0278] In a further preferred embodiment, based on the addition of the second portion P of at least one diol compound G in step (b) G2 When the mixture M2 is used, the molar ratio of all cleavage products P2 having no more than 20 repeating units of the structural formula W3 contained in the mixture M2 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%.

[0279] As the second part G2 The added diol compound G has the above-mentioned structural formula (V).

[0280] Preferably, as the first part P G1 Add the diol compound G and as the second part P G2The added diol compounds G are the same, more preferably all selected from ethylene glycol, butanediol, diethylene glycol, and even more preferably all selected from ethylene glycol, butanediol. Most preferably, as the first part P G1 Add and as the second part P G2 The added diol compound G is ethylene glycol.

[0281] In a preferred embodiment of the process according to the invention, in step (b) as second part P G2 The molar amount of all diol compounds G added to the mixture M2 is ≥0.01 molar equivalents, more preferably ≥0.1 molar equivalents, more preferably in the range of 0.1 to 25 molar equivalents, more preferably in the range of 0.2 to 10 molar equivalents, more preferably in the range of 0.3 to 8 molar equivalents, even more preferably in the range of 0.4 to 7 molar equivalents, still more preferably in the range of 0.5 to 6 molar equivalents, still more preferably in the range of 0.6 to 5 molar equivalents, still more preferably in the range of 0.7 to 4 molar equivalents, still more preferably in the range of 0.8 to 3 molar equivalents, still more preferably in the range of 0.9 to 2 molar equivalents, and most preferably in the range of 1 to 1.5 molar equivalents.

[0282] In a preferred embodiment, at least one diol compound G is used as solvent for compound (III) in the mixture M4 obtained after step (c).

[0283] The process according to the invention is preferably carried out as a solvolysis in order to minimize as much as possible the proportion of undesirable products (such as TS or MHET in the case of PET hydrolysis) in the reaction products and to maximize the proportion of desired products (such as BHET in the case of PET and ethylene glycol solvolysis) in the reaction products.

[0284] Therefore, preferably, the second portion P of the at least one diol compound G added in step (b) is based on the total weight of all diol compounds G added in step (b). G2 The water content is <10 wt.-%, more preferably <5 wt.-%, even more preferably <1 wt.-%, even more preferably <0.1 wt.-%, most preferably <0.01 wt.-%.

[0285] After step (b) is completed, the temperature below the melting temperature T of the polyolefin PO is PO This ensures that the polyolefin PO is used in solid form in step (c).

[0286] When the polyolefin PO is selected from PE and PP, the temperature T bIt is preferably in the range of 80°C to 134°C, more preferably in the range of 90°C to 130°C, still more preferably in the range of 100°C to 130°C, and most preferably in the range of 120°C to 130°C.

[0287] When the at least one polymer P1 is selected from PBT and PET and PO=PE, in another embodiment, the temperature T b It is preferably in the range of 80°C to 134°C, more preferably in the range of 90°C to 130°C, still more preferably in the range of 100°C to 130°C, and most preferably in the range of 120°C to 130°C.

[0288] When the at least one polymer P1 is selected from PBT and PET and PO=PP, in another embodiment, the temperature T b It is preferably in the range of 80°C to 159°C, more preferably in the range of 90°C to 150°C, still more preferably in the range of 100°C to 140°C, and most preferably in the range of 120°C to 130°C.

[0289] 4. Step (c)

[0290] In step (c) of the process according to the invention, the diol compound G is at least partially reacted with at least a portion of the cleavage product P2 in the mixture M3 to obtain at least one compound of formula (III). Formula (III) is as follows:

[0291]

[0292] In structural formula (III), R 1 and R 2 are independently selected from -H, -(CH2) p -[O-(CH2) q ] r -OH, wherein preferably, R 1 and R 2 At least one, more preferably two, of which are independently of each other, are of the structural formula -(CH2) p -[O-(CH2) q ] r -OH group.

[0293] Still more preferably, the group R 1 and R 2 Each has the structural formula -(CH2) p -[O(CH2) q ] r The same group as -OH.

[0294] p is an integer, where 2≤p≤6, in particular p=2 or 4, preferably p=2.

[0295] q is an integer, where 2≤q≤6, in particular q=2 or 4, preferably q=2.

[0296] r is an integer, where 0≤r≤10, in particular r=0 or 1, preferably r=0.

[0297] This gave a mixture M4 comprising:

[0298] - at least one polyolefin PO in the solid state,

[0299] - at least one compound of formula (III),

[0300] - optionally at least one cleavage product P2 of formula (II),

[0301] - optionally at least one polymer P1,

[0302] The molar amount of all compounds of formula (III) in M4 is greater than the molar amount of all compounds of formula (III) in the mixture M1 used in step (a).

[0303] 4.1 Reaction conditions in step (c)

[0304] The reaction of step (c) is carried out at a temperature T c The temperature T c below the melting temperature T of the at least one polyolefin PO contained in the mixture M3 PO .

[0305] Temperature T c may be equal to or different from the temperature T established in step (b) b .

[0306] Temperature T c It may be equal to or different from the temperature of the mixture M2 obtained after the end of step (b).

[0307] In step (c) of the process according to the invention, the second portion P of the at least one diol compound G added to the mixture M2 in step (b) is G2 And from the first part P G1 And any at least one diol compound G which has not reacted in the conversion of step (a) reacts with the cleavage product P2 comprised by M3 and any polymer P1 comprised by M3 in the mixture M3, which gives at least one compound of formula (III).

[0308] The reaction in step (c) of the process according to the invention is therefore carried out, in particular until the second portion P, based in each case on the addition of the at least one diol compound G in step (b), is obtained. G2The weight of all cleavage products P2 and polymer P1 in mixture M3 and therefore in mixture M4 obtained after step (c) is reduced by at least 10 wt.-%, preferably by at least 20 wt.-%, more preferably by at least 30 wt.-%, more preferably by at least 40 wt.-%, more preferably by at least 50 wt.-%, still more preferably by at least 60 wt.-%, still more preferably by at least 70 wt.-%, still more preferably by at least 80 wt.-%, still more preferably by at least 90 wt.-%, and most preferably by at least 98 wt.-%.

[0309] According to the present invention, "in step (b), a second portion P of at least one diol compound G is added G2 When "is especially the second part P of at least one diol compound G G2 When the mixture M2 is first contacted. In order to determine the weight of the polymer P1 or the cleavage product P2 [or the compound of formula (III)] in the mixture M2 at this time, the second part P of the at least one diol compound G can be G2 A sample of the mixture M2 is collected five seconds before the first contact with the mixture M2 and can be used to determine the respective proportions of the polymer P1 or the cleavage product P2 or the compound of formula (III) in the mixture M2. Alternatively, the second portion P of the at least one diol compound G can also be used to determine the respective proportions of the polymer P1 or the cleavage product P2 or the compound of formula (III). G2 Samples are taken from the mixture M2 at various times (sixty seconds, forty-five seconds, thirty seconds, fifteen seconds, five seconds) before the first contact with the mixture M2 to determine the content of the polymer P1 or the cleavage product P2 or the compound of formula (III) in these samples, which is then extrapolated to the second portion P of the at least one diol compound G. G2 Time of addition to mixture M2.

[0310] As explained with reference to Scheme 1 for the end of the cleavage product P2, in step (c) it is also preferred that the water content in the mixture M3 during the reaction in step (c) and in particular also in the mixture M4 obtained after the end of step (c) is at a minimum, so that in the reaction of the diol compound G with the polymer P1 and the cleavage product P2, a mixture is produced in which R 1 、R 2 The solvolysis transesterification ratio of the compound of formula (III) in which all groups are ≠H is at a maximum, and produces 1 、R 2 The hydrolysis ester cleavage ratio of the compound of formula (III) in which at least one of the groups is =H is at a minimum. This is because R 1 、R 2Compounds of the formula (III) with ≠H can be more easily polymerized back into the polymer P1. If the process according to the invention is used in the reprocessing of the polymer P1, it is advantageous to make the R 1 、R 2 ≠H of the compound of formula (III) is maximized, and R in the resulting mixture M4 is 1 、R 2 The proportion of compounds of formula (III) having at least one, preferably two, =H in the formula (III) is minimized.

[0311] It is therefore advantageous to keep the water content in mixture M3 as low as possible during the reaction in step (c).

[0312] In a preferred embodiment of the present invention, the water content in the mixture M3 during the reaction in step (c) is therefore <10% by weight, more preferably <5% by weight, even more preferably <1% by weight, even more preferably <0.1% by weight and most preferably <0.01% by weight, based in each case on the total weight of the mixture M3.

[0313] In step (c) of the process according to the invention, the reaction of the mixture M3 takes place at a temperature T c The temperature T c below the melting temperature T of the at least one polyolefin PO contained in the mixture M3 PO Thus, during the reaction according to step (c), the polyolefin PO is in solid form in the mixture M3. This prevents the formation of sticky lumps of PO that are difficult to separate.

[0314] When the polyolefin PO is selected from PE and PP, the temperature T c It is preferably in the range of 80°C to 134°C, more preferably in the range of 90°C to 130°C, still more preferably in the range of 100°C to 130°C, and most preferably in the range of 120°C to 130°C.

[0315] When the at least one polymer P1 is selected from PBT and PET and PO=PE, in another embodiment, the temperature T c It is preferably in the range of 80°C to 134°C, more preferably in the range of 90°C to 130°C, still more preferably in the range of 100°C to 130°C, and most preferably in the range of 120°C to 130°C.

[0316] When the at least one polymer P1 is selected from PBT and PET and PO=PP, in another embodiment, the temperature T c It is preferably in the range of 80°C to 159°C, more preferably in the range of 90°C to 150°C, still more preferably in the range of 100°C to 140°C, and most preferably in the range of 120°C to 130°C.

[0317] Step (c) of the process according to the invention can be carried out in any reaction vessel known to the person skilled in the art, preferably in a reactor (eg an autoclave), preferably in a stirred tank reactor.

[0318] Alternatively, step (c) can also be carried out in a kneader or an extruder E, preferably in an extruder E.

[0319] The extruder E used in a preferred embodiment is a piston extruder or a multi-shaft extruder, particularly preferably a multi-shaft extruder.

[0320] Preferred multi-screw extruders are planetary roller extruders or multi-screw extruders, in particular twin-screw extruders.

[0321] In a further preferred embodiment, step (c) is carried out at least partly in a reactor, in particular a stirred tank reactor.

[0322] If step (a) is carried out in an extruder E, in a preferred embodiment at least a part of step (b) and the entirety of step (c) is carried out in a reactor, in particular a stirred tank reactor.

[0323] Alternatively, steps (a) to (c) of the process according to the invention can also be carried out in an extruder E.

[0324] 4.2 Catalyst K2

[0325] Advantageously, the reaction of the diol compound G with the cleavage product P2 in the mixture M3 in step (c) is carried out in the presence of at least one catalyst K2.

[0326] The catalyst K2 can already be present in the mixture M3 before the addition of the at least one diol compound G [for example in the form of residues of the catalyst K1 used in the preferred embodiment of step (a)], added to the mixture M3 after the addition of the at least one diol compound G and / or added together with the at least one diol compound G to the mixture M3.

[0327] The catalyst K2 can be selected by those skilled in the art on the basis of their knowledge in the field.

[0328] Catalyst K2 is preferably selected from carbonates, bicarbonates, metal halides, amines, alkoxides, acetates, phosphates, dibutyltin oxide, more preferably selected from amines, alkoxides, acetates; still more preferably, catalyst K2 is an alkoxide, still more preferably an alkali metal alkoxide.

[0329] Preferred acetates are selected from lead acetate and zinc acetate, with zinc acetate being more preferred.

[0330] Preferred phosphates are the alkali metal phosphates, especially sodium phosphate.

[0331] The preferred metal halide is zinc chloride.

[0332] Preferred carbonates are alkali metal carbonates or alkaline earth metal carbonates, especially alkali metal carbonates, preferably sodium carbonate.

[0333] Preferred bicarbonates are alkali metal bicarbonates or alkaline earth metal bicarbonates, especially alkali metal bicarbonates, preferably sodium bicarbonate.

[0334] The amine used is preferably a trialkylamine, such as trimethylamine, triethylamine, dimethylethylamine, di(isopropyl)ethylamine ("DIPEA"), or a cyclic amine, such as 1,5,7-triazabicyclo[4.4.0]dec-5-ene ("TBD") or 1,8-diazabicyclo[5.4.0]undec-7-ene ("DBU").

[0335] If the catalyst K2 used is an alkoxide, in particular an alkali metal alkoxide, it is preferably used in solid form, for example in the form of a powder or granules.

[0336] Preferred alkoxides are alkali metal alkoxides wherein the alcohol is a monohydric or dihydric alcohol having 1 to 6 carbon atoms.

[0337] Still more preferred alkali metal alkoxides are those wherein the alkoxide is selected from the group consisting of:

[0338] - methoxide;

[0339] - ethanol salts;

[0340] -Propanolate, meaning n-propoxide or isopropoxide;

[0341] - butoxides, in particular n-butoxide;

[0342] -pentanolates, in particular n-pentanolate;

[0343] - hexanolates, in particular n-hexanolate;

[0344] - glycol salts;

[0345] More preferably, it is selected from methoxide, ethanolate, and glycolate, still more preferably, it is selected from methoxide and ethanolate, and most preferably, it is selected from methoxide.

[0346] Preferred alkali metals here are lithium, sodium, potassium, more preferably sodium, potassium, still more preferably sodium.

[0347] In a particularly preferred embodiment, the catalyst K2 is selected from sodium ethylene glycol, potassium ethylene glycol, potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, more preferably selected from potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, and even more preferably selected from sodium methoxide, potassium ethoxide, sodium ethoxide; particularly preferably, K2 = sodium methoxide.

[0348] The amount of catalyst K2 used in step (c) can be selected by those skilled in the art according to their knowledge in the art. G2 The molar amount of all catalysts K2 used in step (c), based on the molar amount of all diol compounds G added, is in particular in the range from 0.01% to 10%, preferably in the range from 0.1 to 5%, more preferably in the range from 1 to 4%, still more preferably in the range from 2.5 to 3.5%, and particularly preferably 3%.

[0349] 4.3 Mixture M4

[0350] After step (c) of the process according to the invention, a mixture M4 is obtained comprising at least one compound of formula (III) and at least one polyolefin PO in the solid state, with or without at least one cleavage product P2, and with or without at least one polymer P1.

[0351] The mixture M4 after step (c) is at a temperature below the melting temperature of the polyolefin PO. The exact temperature at which the mixture M4 is obtained after step (c) may be, but is not necessarily, the temperature T at which the reaction in step (c) occurs. c It is important for the present invention that the mixture M4 after step (c) is obtained at a temperature below the melting temperature of the polyolefin PO. In a preferred embodiment, the mixture M4 after step (c) is at a temperature T at which the reaction in step (c) is carried out. c Down.

[0352] The mixture M4 may also contain at least one cleavage product P2, and the mixture M4 may also contain at least one polymer P1. For example, when not all of the cleavage products P2 or polymer P1 contained in the mixture M3 have reacted with at least one diol compound G in step (c) of the process according to the invention, for example, when a second portion P of the diol compound G, based on the repeating units W3 contained in the polymer P1 and cleavage products P2 in the mixture M3, G2 This is the case when used in molar deficiency in step (c) (described in Section 2.6).

[0353] In a preferred embodiment, the mixture M4 comprises at least one cleavage product P2 and, even more preferably, additionally at least one polymer P1.

[0354] The mixture M4 may also comprise at least one diol compound G.

[0355] In a still more preferred embodiment, the mixture M4 comprises at least one cleavage product P2, at least one polymer P1 and at least one diol compound G.

[0356] This is the case at least when the molar amount of all compounds of formula (III) in the mixture M4 obtained after step (c) is greater than the molar amount of all compounds of formula (III) in the mixture M1 used in step (a).

[0357] This is simply because, in step (c) of the process according to the invention, at least a portion of the cleavage product P2 in the mixture M3 and at least a portion of the polymer P1 (if present in the mixture M3) are reacted with at least one diol compound G to give at least one compound of the formula (III). G1 The amount of the at least one diol compound G added, the reaction time), those skilled in the art can also set the conditions so as to obtain the maximum molar amount of the compound of structural formula (III) in M4.

[0358] In the context of the present invention, "mixture M1 used in step (a)" means more particularly "the first part P of the mixture to which at least one diol compound G is added in step (a)". G1 The mixture M1".

[0359] According to the present invention, "a first portion P of at least one diol compound G is added in step (a) G1 When "is especially at least one first part P of diol compound G G1 When the mixture M1 is first contacted. In order to determine the weight of the polymer P1 or the cleavage product P2 [or the compound of formula (III)] in the mixture M1 at this time, the first part P of the at least one diol compound G can be G1 A sample of the mixture M1 is collected five seconds before the first contact with the mixture M1 and can be used to determine the respective proportions of the polymer P1 or the cleavage product P2 or the compound of formula (III) in the mixture M1. Alternatively, the first portion P of the at least one diol compound G can also be used to determine the respective proportions of the polymer P1 or the cleavage product P2 or the compound of formula (III) in the mixture M1. G1 Samples are taken from the mixture M1 at various times (sixty seconds, forty-five seconds, thirty seconds, fifteen seconds, five seconds) before the first contact with the mixture M1 to determine the content of the polymer P1 or the cleavage product P2 or the compound of formula (III) in these samples, which is then extrapolated to the first portion P of the at least one diol compound G. G1 Time of addition to mixture M1.

[0360] In an optional embodiment of the present invention, in which the mixture M4 obtained after step (c) further comprises at least one cleavage product P2, it is preferred that at least one of the following conditions (α**) and (β**) is satisfied, more preferably at least the condition (β**) is satisfied, and preferably both the conditions (α**) and (β**) are satisfied:

[0361] (α**) Average degree of polymerization of all pyrolysis products P2 contained in the mixture M4 after step (c) 24 Lower than the second portion P of at least one diol compound G added in step (b) G2 The average degree of polymerization of all pyrolysis products P2 contained in the mixture M2 is ρ 22 ;

[0362] (β**) The molar amount of all cleavage products P2 contained in the mixture M4 after step (c) is less than the molar amount of the second part P of the at least one diol compound G added in step (b). G2 The molar amount of all cleavage products P2 contained in the mixture M2.

[0363] In an optional embodiment of the present invention, in which the mixture M4 obtained after step (c) further comprises at least one polymer P1, it is preferred that at least one of the following conditions (α***), (β***) is satisfied, more preferably at least the condition (β***) is satisfied, and preferably both the conditions (α***) and (β***) are satisfied:

[0364] (α***) Average degree of polymerization of all polymers P1 contained in the mixture M4 after step (c) 14 Less than the average degree of polymerization ρ of all polymers P1 contained in the mixture M1 used in step (a) 11 ;

[0365] (β***) The molar amount of all polymers P1 contained in the mixture M4 after step (c) is less than the molar amount of all polymers P1 contained in the mixture M1 used in step (a).

[0366] 4. Step (d)

[0367] In step (d) of the process according to the invention, the solid polyolefin PO is at least partially separated from the mixture M4.

[0368] The separation can be carried out by methods familiar to those skilled in the art, preferably by gravity or by filtration, more preferably by filtration.

[0369] Gravity separation methods are, for example, decantation or centrifugation.

[0370] In step (d), the advantage of the process according to the invention is achieved in that the polyolefin PO present in the starting mixture M1 can be easily and efficiently separated from the mixture M4 obtained after completion of step (c) of the process according to the invention.

[0371] 5. Pollutants V

[0372] In a preferred embodiment, the mixture M2 comprises not only a melt of at least one cleavage product P2 and at least one polyolefin PO, but also at least one solid contaminant V. The solid contaminant V can be organic or inorganic.

[0373] Solid pollutants V are preferably selected from paper, metals, metal oxides, fibers (especially textile fibers), ash, sand, debris, soil, plastics P other than P1 and PO F , more preferably selected from plastic P F , ash, sand.

[0374] Plastic P F In particular, a plastic having a higher melting temperature than the at least one PO (and in particular also a higher melting temperature than the at least one polymer P1). Alternatively, in particular, the plastic P F It does not have a melting temperature, but rather a glass transition temperature.

[0375] More preferably, the plastic P F Selected from polycarbonate.

[0376] In this embodiment, the at least one solid pollutant V contained in the mixture M2 is generally derived from the corresponding pollutant in the mixture M1 used in step (a). Therefore, in a preferred embodiment of the present invention, the mixture M1 and the mixture M2 used in step (a) contain at least one solid pollutant V.

[0377] The method according to the invention is particularly suitable for the depolymerization of polymers P1, in particular PET or PBT, which, in the case of waste materials, are present not only as a mixture with PO but also in a mixture with other solid contaminants V. Such solid contaminants V then reappear at least partially in the mixture M2 obtained after step (a). In principle, they can be separated from the mixtures M1, M2, M3, or M4 during or after the method according to the invention (for example, by filtration or gravity).

[0378] In a preferred embodiment of the present invention, the mixture M2 comprises not only a melt of at least one cleavage product P2 and at least one polyolefin PO, but also at least one solid contaminant V, wherein the solid contaminant V is at least partially separated from the mixture M2 before the mixture M2 is cooled in step (b) to a temperature below the melting temperature of the at least one polyolefin PO ("preferred embodiment Θ").

[0379] The separation can be carried out by methods familiar to those skilled in the art, preferably by gravity or by filtration, more preferably by filtration.

[0380] Gravity separation methods are, for example, decantation or centrifugation.

[0381] This embodiment further contributes to the surprising effect on which the present invention is based. As described for step (b) (point 3), in the comparative process, at least one polymer P1 is combined with at least one diol compound G at all times > T PO When the reaction is carried out at a low temperature, i.e., in a reaction mixture in which the PO is always molten, and the reaction mixture is cooled to a temperature below the melting temperature of the PO only after the reaction is complete, there is the problem that the solidified polyolefin PO can only be separated inefficiently and in a complex manner from the remainder of the crude product. This problem is exacerbated when the starting mixture includes other solid contaminants V. If these other solid contaminants V are present in the resulting reaction mixture when the PO solidifies after the depolymerization is complete, separation of the solidified PO can be further difficult because they can form inclusions with the PO during solidification, causing the PO to form inhomogeneous aggregates.

[0382] This problem is solved by another embodiment Θ. This is because, in this embodiment, the solid contaminants V are removed when the polyolefin PO is in molten form in the mixture M2, i.e., when it is a liquid substance, which simplifies the separation and prevents the formation of inclusions, for example, when PO solidifies in the presence of at least one contaminant V.

[0383] Example

[0384] Embodiments of the Invention

[0385] The reduction takes place in a twin-screw extruder (length-to-diameter ratio = 33; screw diameter 30 mm) with a housing section whose wall temperature can be set at various levels. At the extruder inlet, 3.8 kg / h of PET flakes and 0.2 kg / h of polyethylene pellets are metered gravimetrically into the processing chamber at a housing temperature of 70°C. Downstream of the housing (housing temperature: 265°C), the metered polymer fraction is melted. A 4 wt% solution of sodium glycolate in ethylene glycol is injected into the melt. The mass flow ratio of sodium glycolate solution to PET is 1. The housing temperature immediately downstream of the injection point is also 265°C and decreases to 130°C toward the extruder outlet. At the extruder outlet, a pasty mixture of BHET and BHET oligomers (i.e., cracking products P2 with n<49, predominantly with n<20) in ethylene glycol, along with polyethylene agglomerates, is discharged.

[0386] The extruder output is collected and, in a subsequent step, reacted with further ethylene glycol in a stirred tank reactor. The weight ratio of ethylene glycol is 5:1, based on the extruder output used. The initial charge of ethylene glycol in the reactor is heated to 100°C, and the now solidified reactor output is added. While stirring, a light grey suspension is formed. The temperature is raised to 130°C, thus below the melting point of PE (135°C). 3% by weight of sodium methoxide (solution in methanol), based on the extruder output used, is added. Within 15 minutes, a clear solution having ethylene glycol and BHET as the main components is formed. The polyethylene lumps present in the extruder output do not change in morphology, do not float, i.e. do not settle on the agitator shaft, and can be easily filtered out.

[0387] Comparative Example

[0388] Inventive Example 1 was repeated except that the extruder output was heated in a stirred tank reactor to 160° C. instead of 130° C. before the addition of the sodium methoxide solution (in methanol). The result was a clear solution in which the PE lumps did not float but formed a sticky polyethylene coagulum that was coiled around the axis and was difficult to remove.

[0389] result

[0390] The glycolysis of PET in a PET / PE mixture in a two-stage process at different temperature levels (step 1 at a temperature above the melting temperature of the polyolefin (in this case polyethylene); step 2 at a temperature below the melting temperature of polyethylene) allows the decomposition of the PE-contaminated PET fraction by solvolysis within an economically feasible reaction time and the efficient separation of the polyolefin contaminants from the resulting crude product.

[0391] The method according to the invention thus makes it possible to depolymerize waste materials containing polymers P1 (such as PET and PBT) contaminated with polyolefins (e.g., PE). Thus, the first reaction step achieves partial conversion within a relatively short reaction time. Then, in the second reaction stage, the depolymerized material obtained in the first step can be further decomposed at low temperatures within a short period of time, in particular to give monomers such as BHET. Thus, the temperature regulation according to the invention in both steps, which is carried out according to the melting temperature of the contaminated polyolefin, has the effect that the molten and resolidified polyolefin contaminants can be easily separated from the final product, thus not impairing the method.

[0392] analyze

[0393] According to the present invention, the molecular weight distribution of polymer P1 and cleavage product P2 (and therefore the average degree of polymerization p in a given mixture) is determined by gel permeation chromatography ("GPC") as follows: Method 1. Method 1 is based on the method of MR Milana, M. Denaro, L. Arrivabene, A. Maggio, L. Gramiccioni, Food Additives and Contaminants, 1998, 15, 355-361, page 356.

[0394] Method 1

[0395] 1. A sample of the mixture to be tested was diluted in 1,1,1,3,3,3-hexafluoro-2-propanol ("HFIP") at a weight ratio of 1:333 and dissolved at room temperature for 24 hours.

[0396] 2. The solution was filtered through a 1 μm disposable polytetrafluoroethylene filter and injected using an autosampler for analysis.

[0397] 3. Use the following size exclusion chromatography ("GPC") system:

[0398] Eluent: HFIP / 0.05M KTFAc (=potassium trifluoroacetate)

[0399] Precolumn: PSS PFG, 7 μm, guard column, ID 8.00 mm x 50.00 mm

[0400] Column: PSS PFG, 7 μm, ID 8.00mm x 300.00mm

[0401] PSS PFG, 7μm, ID 8.00mm x 300.00mm

[0402] PSS PFG, 7μm, ID 8.00mm x 300.00mm

[0403] Pump: PSS-SECurity 1260HPLC pump

[0404] Flow rate: 1.0ml / min

[0405] Injection system: PSS-SECcurity 1260 automatic sampler

[0406] Injection volume: 50 μl

[0407] Sample concentration: 3.0g / L

[0408] Temperature: 30℃

[0409] Detector: SECcurity 2 Differential Refractometer Detector (RI)

[0410] Review: PSS-WinGPC UniChrom Version 8.4

[0411] 4. Calibration in the separation region of the column combination with the aid of PMMA standards (PMMA = polymethyl methacrylate). Based on the PMMA calibration using the strip method, the molar mass mean and its distribution are calculated with the aid of a computer, giving the average degree of polymerization p in a given mixture.

Claims

1. A process for depolymerizing at least one polymer P1, wherein the at least one polymer P1 comprises n1 interconnected repeating units of the following formula (I): Where a is an integer, 2≤a≤6, Where b is an integer, 2≤b≤6, Where c is an integer, 0≤c≤10, Where n1 is an integer ≥ 50, wherein the n1 interconnected repeating units of structural formula (I) contained in the polymer P1 are the same or different, and wherein the n1 interconnected repeating units of formula (I) are interconnected within the polymer P1 in such a manner that the bond marked “(i)” of one repeating unit of formula (I) is linked to the bond marked “(ii)” of an adjacent repeating unit of formula (I), The method comprises the following steps: (a) adding at least one compound having the structural formula (V): HO-(CH2) d -[O-(CH2) e ] f The first part P of the diol compound G containing -OH G1 Where d is an integer, 2≤d≤6, Where e is an integer, 2≤e≤6, Where f is an integer, 0≤f≤10, A mixture M1 is obtained, comprising: - said at least one polymer P1, - a melt of at least one polyolefin PO having a melting temperature T PO below the melting temperature T of the at least one polymer P1 P1 , and reacting the diol compound G with at least a portion of the polymer P1 in the mixture M1 at least partially to obtain at least one cleavage product P2, The cleavage product P2 has the structural formula (II): where a II is an integer, 2≤a II ≤6, where b II is an integer, 2≤b II ≤6, where c II is an integer, 0≤c II ≤10, Where n2 is an integer, 2≤n2≤48, wherein the n2 interconnected W2 units in the cleavage product P2 are the same or different in the cleavage product P2, wherein each W2 unit conforms to the structure enclosed by a set of brackets with a "n2" subscript in the structural formula (II), where R II1 Selected from -H, in is an integer, in is an integer, in is an integer, where R II2 A group selected from -H, -OH, a group of formula (IV): and wherein step (a) is carried out at a temperature above the melting temperature T of the at least one polyolefin PO PO Temperature T a Next, so as to obtain a mixture M2 comprising: - at least one cleavage product P2, - a melt of at least one polyolefin PO, wherein the molar amount of all cleavage products P2 in the mixture M2 is greater than the molar amount of all cleavage products P2 in the mixture M1 used in step (a); (b) cooling the mixture M2 to a temperature below the melting temperature T of the at least one polyolefin PO PO Temperature T b , Wherein, the mixture M2 is cooled to the temperature T b During and / or after, the second part P of at least one diol compound G of formula (V) G2 Added to the mixture M2, so as to obtain a mixture M3 comprising: - at least one cleavage product P2, - said at least one polyolefin PO in solid state, - at least one diol compound G, (c) at least partially reacting the diol compound G with at least a portion of the cleavage product P2 in the mixture M3 to obtain at least one compound of formula (III): where R 1 and R 2 Independently selected from H, -(CH2) p -[O-(CH2) q ] r -OH, Where p is an integer, 2≤p≤6, Where q is an integer, 2≤q≤6, Where r is an integer, 0≤r≤10, The reaction in step (c) is carried out at a temperature T c The temperature T c below the melting temperature T of the at least one polyolefin PO PO , This gave a mixture M4 comprising: - said at least one polyolefin PO in solid state, - at least one compound of formula (III), wherein the molar amount of all compounds of formula (III) in M4 is greater than the molar amount of all compounds of formula (III) in the mixture M1 used in step (a), (d) at least partially separating the solid polyolefin PO from the mixture M4.

2. The method according to claim 1 , wherein the mixture M2 comprises not only the melt of the at least one pyrolysis product P2 and the at least one polyolefin PO, but also at least one solid contaminant V, wherein the solid contaminant V is at least partially separated from the mixture M2 before the mixture M2 is cooled in step (b) to a temperature below the melting temperature of the at least one polyolefin PO.

3. The process according to claim 1 or 2, wherein the reaction of step (a) is carried out until the weight of all polymers P1 in the mixture M2 has decreased by at least 10% by weight, based on the weight of all polymers P1 in the mixture M1 used in step (a).

4. The method according to claim 1 , wherein the amount of the first part P1 in step (a) is based on the molar amount of all repeating units of formula (I) contained in the polymer P1 in the mixture M1 used in step (a). G1 The molar amount of all diol compounds G added to the mixture M1 is ≥0.01 molar equivalents.

5. The method according to any one of claims 1 to 4, wherein the reaction of the diol compound G with the cleavage product P2 in the mixture M3 in step (c) is carried out in the presence of at least one catalyst K2.

6. The method according to claim 5, wherein the catalyst K2 is selected from carbonates, bicarbonates, metal halides, amines, alkoxides, acetates, phosphates, and dibutyltin oxide. 7 . The process according to claim 1 , wherein the reaction of the diol compound G with the polymer P1 in the mixture M1 in step (a) is carried out in the presence of at least one catalyst K1.

8. The method according to claim 7, wherein the catalyst K1 is selected from carbonates, bicarbonates, metal halides, amines, alkoxides, acetates, phosphates, and dibutyltin oxide. 9 . The process according to claim 1 , wherein during the reaction in step (a), the water content in the mixture M1 is <10% by weight, based on the total weight of the mixture M1. 10 . The process according to claim 1 , wherein during the reaction in step (c), the water content in the mixture M3 is <10% by weight, based on the total weight of the mixture M3.

11. The process according to any one of claims 1 to 10, wherein the at least one polyolefin PO is selected from the group consisting of polyethylene, polypropylene, polyisobutylene, polybutene. 12 . The process according to claim 1 , wherein the at least one polymer P1 is selected from polyethylene terephthalate, polybutylene terephthalate. 13 . The process according to claim 1 , wherein step (a) is carried out at least partially in a kneader or extruder (E).

14. The process according to any one of claims 1 to 13, wherein step (c) is at least partially carried out in a stirred tank reactor.

15. The method according to any one of claims 1 to 14, wherein in step (b), the mixture M2 has been cooled to the temperature T b Thereafter, the second portion P of the at least one diol compound G is G2 Add to the mixture M2.

16. The method according to any one of claims 1 to 15, wherein the ratio of the molar amount of all cleavage products P2 of formula (II) in the mixture M1 used in step (a) to the molar amount of all polymers P1 in the mixture M1 used in step (a) is <1:1, and the second portion P of the at least one diol compound G is added in step (b). G2 When all the cracking products P2 of the structural formula (II) in the mixture M2 are added to the second part P of the at least one diol compound G in step (b) G2 The molar ratio of all polymers P1 in the mixture M2 is ≥1:1.

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