Polyethylene glycol terephthalate degradation catalyst

Abstract

The present invention belongs to the field of plastic / polymer recovery and relates to a process for converting, for example, an end-use / waste PET polymer, a very common polyester, into a commonly used pure monomeric compound, such as BHET, which can be reused in the production of "original" PET, i.e. PET having a similar or the same quality as unrecovered PET. In addition, the invention can also be used to recover BHET and textiles (e.g., cotton) from PET / textile blends.

Description

TECHNICAL FIELD

[0001] The present invention belongs to the field of chemistry, more specifically to the field of plastic / polymer recycling, and relates to a method for converting waste polyethylene terephthalate (PET) polymers into a commonly used monomer compound, such as bis(hydroxyethyl) terephthalate (BHET), which can be reused to produce virgin PET, i.e. PET of similar or identical quality to non-recycled PET. Furthermore, the present invention can be used to recycle BHET and textiles (e.g. cotton) from blended fabrics. BACKGROUND

[0002] Synthetic polymers are one of the biggest pollution sources that hinder the sustainable development of human society. For many years, the global polymer production (about 348 million metric tons in 2017) has been growing exponentially. Polyethylene terephthalate (PET) is one of the highest yielding polymers, with an annual production of about 70 million metric tons, and an expected annual growth rate of more than 4%. PET-based polymers are mainly used for beverage bottles, and one third of the produced PET is blended with cotton-based fibers and viscose fibers for the production of textile fabrics. Therefore, recycling of composites including beverage bottle waste has become an urgent social problem. Chemical upgrading recycling of plastic waste, also known as chemical recycling, monomer production and chemical decomposition, is an attractive option that can produce high value-added products while avoiding additional greenhouse gas emissions and negative environmental impacts of waste incinerator energy recovery.

[0003] Catalytic glycolysis and transesterification of PET bottles is an atom-economical method that can produce the useful intermediate BHET (bis(hydroxyethyl) terephthalate), which can be recycled as a precursor to produce PET through polymerization. Lewis acidic metals have been used as catalysts in these reactions at high reaction temperatures (160-220 °C) to overcome the high reaction energy barrier and accelerate PET dissolution Figure 1 Examples of metal-catalyzed PET glycolysis include catalysts Zn(OAc)2, Ti(IV) phosphate and Mn(OAc)2, which exhibit satisfactory performance (see, for example: M. Ghaemy et al., Polymer Degradation and Stability, Vol. 90, No. 3, December 2005, pp. 570-576). Although these catalytic systems have high efficiency, only a few of them can produce BHET of high purity due to metal contamination, and thus require cumbersome purification steps such as crystallization of BHET, which reduces the compatibility of the produced BHET when used in PET re-polymerization.

[0004] Heavy metal contamination is an important issue for the polymerization of BHET obtained by the above methods in terms of PET polymer yield and appearance. Metal contamination of cotton and the like during PET depolymerization in PET-cotton blended fabrics is also an issue for these methods. Organic catalysis can be one way to solve such problems and research has been conducted in this regard.

[0005] For example, WO2015 / 056377 discloses a method for converting PET to BHET using various organic amine bases such as trimethylamine (TEA), ethylene glycol at 220°C and 20 psi pressure (Example 3, page 21). No CO2 source is used. The ratio of BHET to PET oligomers in the depolymerization product is reported to be high. However, the disadvantages of this method are the use of more toxic and costly amine catalysts and the fact that the reported yield is achieved under more harsh conditions including pressure and / or temperature.

[0006] Therefore, an improved method for converting PET back to its monomeric component BHET or useful derivatives thereof would be advantageous, in particular a more productive, environmentally friendly and simple method for producing BHET monomer from PET, as well as a method for separating PET from other textiles in blended fabrics would be advantageous. SUMMARY

[0007] It is therefore an object of the present invention to provide a method for producing BHET monomer or derivatives thereof from end-of-use / waste PET material, aiming to provide a monomer that can produce recycled PET of comparable quality to non-recycled PET.

[0008] In particular, it is an object of the present invention to provide a method that solves the above-mentioned problems of metal contamination in the prior art and undesirable pigment precipitation of BHET in depolymerized PET and the resulting recycled PET material, while avoiding the use of toxic bases and high pressure and / or high temperature conditions.

[0009] Thus, a first aspect of the present invention is a method for the chemical depolymerization of polyethylene terephthalate (PET) comprising the steps of:

[0010] a) providing a PET-containing material;

[0011] b) mixing the PET-containing material of step a) with a source of carbon dioxide, a source of amine and a compound of formula (I):

[0012]

[0013] c) heating the mixture obtained in step b) to a temperature in the range of 130°C to 220°C;

[0014] d) obtaining a product comprising a compound of formula (II):

[0015]

[0016] wherein:

[0017] R is selected from the group consisting of OH and N(R 1 )2;

[0018] X is selected from the group consisting of O and NR 2 ;

[0019] R 1 and R 2 are each independently selected from the group consisting of H, methyl, ethyl, propyl, isopropyl, butyl, and isobutyl;

[0020] n is any integer in the range of 1-10.

[0021] Another aspect of the present invention is a method of separating polyethylene terephthalate (PET) and a textile from a blended textile containing PET and the textile, comprising the steps of:

[0022] a) providing a blended textile containing a textile and PET;

[0023] b) mixing the blended textile in step a) with a source of carbon dioxide, a source of amine, and a compound of formula (I):

[0024]

[0025] c) heating the mixture resulting from step b) to a temperature in the range of 130 °C to 220 °C;

[0026] d) obtaining a product comprising a compound of formula (II) and the textile:

[0027]

[0028] e) separating the compound of formula (II) and the textile in the product in step d);

[0029] wherein:

[0030] R is selected from the group consisting of OH and N(R 1 )2;

[0031] X is selected from the group consisting of O and NR 2 ;

[0032] R 1 and R 2 are each independently selected from the group consisting of H, methyl, ethyl, propyl, isopropyl, butyl, and isobutyl;

[0033] n is any integer in the range of 1-10.

[0034] The present inventors have surprisingly found that these methods can yield BHET derivatives from starting PET materials in high yield and are tolerant to the presence of a variety of other materials in the reaction mixture, while facilitating isolation of the product from the catalyst and solvent used. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 (A) a schematic of chemical recycling of PET by glycolysis using a metal catalyst in the prior art, and (B) the chemical recycling of CO2 and NH3 catalyzed beverage bottles and textile waste employed in the present invention.

[0036] Figure 2A A comparison of the transesterification of ethyl ester 1 with ethylene glycol 2a to glycol ester 3 catalyzed by NH4HCO3 and the same reaction without catalyst is shown. The black yield is the yield of the NH4HCO3 catalyzed transesterification, and the yield in parentheses is the yield without catalyst. b Methyl benzoate was used as the starting material. c The reaction was performed at 150 °C with 25 mol% catalyst. The catalytic yield of NH4HCO3 was significantly better than without catalyst.

[0037] Figure 2B The transesterification of ethyl ester 1a with ethylene glycol and polyethylene glycol derivatives 2a-k to esters 3a-k catalyzed by NH4HCO3 is shown. The product NMR yields are shown in percent unless otherwise noted. The results show substrate flexibility for compounds of formula (I).

[0038] Figure 3A An exemplary reaction scheme for PET catalytic depolymerization with cotton recovery is shown.

[0039] Figure 3B PET polyester with cotton (75%) is shown catalytically depolymerized with NH4HCO3 * (NH4HCO3) and without catalyst ¤ at 180 °C and 190 °C, respectively. The catalytic reaction proceeds smoothly even at 180-190 °C, while the uncatalyzed reaction has a yield of less than 50% after 6 hours.

[0040] Figure 4A A chemical process for large scale recovery of PET / textile blended fabrics from clothing and upholstery materials is shown. Glycolysis was performed using fabrics with 47-100% PET, showing optical images and percent yields of recovered cotton / textile materials and BHET. The reactions show excellent textile recovery and good BHET yield.

[0041] Figure 4BThe following images show the solid states of recycled cotton reacted with NH4HCO3 (fourth from the top), recycled cotton without NH4HCO3 reaction (third from the top), commercially available cotton balls (second from the top), and starting materials (first from the top). 13 C NMR analysis showed that the spectrum of recycled cotton was similar to that of commercially available cotton balls.

[0042] Figure 4C The right figure shows the recovered cotton after reacting with NH4HCO3 and with Zn at magnifications of 20x, 40x, and 80x. 2+ An optical microscope image of the recycled cotton reacting (left panel). The superior quality of the recycled cotton from the method of this invention is evident.

[0043] Figure 4D The images show optical microscope images of commercially available cotton balls (top left), starting material (top right), cotton recovered from the reaction without NH4HCO3 (bottom left), and cotton recovered from the reaction with NH4HCO3 (bottom right). It is evident that the reaction of this invention significantly improves the removal efficiency of PET fibers.

[0044] Figure 5A Thermogravimetric analysis (TGA) results of chemically recycled cotton in PET / cotton blends are shown. TGA measurements include commercially available cotton balls (solid line, *), residue after NH4HCO3 catalytic reaction (solid line, ¤), residue after no NH4HCO3 catalytic reaction (solid line, #), and the starting material fabric (solid line, ^); dashed lines represent the corresponding DTG spectra. It can be seen that the spectrum of the catalytically reacted recycled cotton is similar to that of the commercially available cotton balls, while the uncatalyzed textile is more similar to that of the starting material.

[0045] Figure 5B Infrared spectra of recycled cotton (*), commercially available cotton (¤), starting material (75% polyester, 25% cotton) (#), and reaction residue (^) without NH4HCO3 catalyst after depolymerization of blended fabrics are shown. The results indicate that the infrared spectrum of the catalytically reacted recycled cotton is close to that of commercially available cotton.

[0046] Figure 6 Results of catalytic reactions of PET / cotton blends with mixtures of various other plastics / polymers are shown. These reactions provide excellent yields of recycled cotton and BHET, while the remaining plastics do not degrade and can be removed by filtration.

[0047] Figure 7 A shows the yield of BHET produced by glycolysis of PET using bases such as zinc acetate (Zn(OAc)2), sodium hydroxide (NaOH), triethylamine (TEA), and ammonium bicarbonate (NH4HCO3).

[0048] Figure 7 B shows substrates recovered from the glycolysis of PET using bases, such as zinc acetate (Zn(OAc)2), sodium hydroxide (NaOH), triethylamine (TEA), and ammonium bicarbonate (NH4HCO3).

[0049] The application will be described in further detail below. DETAILED DESCRIPTION

[0050] Definitions

[0051] Before discussing the present application in further detail, the following terms and conventions will first be defined:

[0052] Depolymerization

[0053] In this context, depolymerization is the process by which a polymer formed from monomers is caused to yield said monomer units or precursors / derivatives thereof. Since the polymer is insoluble in most solvents, the depolymerization process occurs partly in a heterogeneous mixture of the polymer and the reactants / solvents, which becomes homogenized as the polymer is converted to oligomers and eventually to individual small molecules.

[0054] Polyethylene terephthalate

[0055] In this context, polyethylene terephthalate, commonly abbreviated as PET or PETE, is a polymer having repeating units of formula (a):

[0056]

[0057] PET is the most common polymer in the polyester family. PET is a transparent, strong, lightweight plastic that is widely used for packaging of food and beverages. The basic building blocks of PET are ethylene glycol (HO-CH2CH2-OH) and terephthalic acid, which combine to form the repeating unit of the polymer chain.

[0058] Mixing

[0059] In this context, mixing is the basic process of bringing the starting materials, reactants, catalysts, and any other materials into contact with each other while the mixture is stirred, typically by mechanical stirring, but other types of stirring can also be used. Broadly, the mixture to be mixed can be a solid mixture, a suspension of solids in a liquid, or a solution. In this context, the resulting mixture is typically a suspension of PET in a solvent, with the reactants dissolved or suspended therein. As depolymerization proceeds, the PET is gradually dissolved as oligomers and eventually as monomers.

[0060] PET-containing material

[0061] The PET-containing material herein can be essentially any material containing any amount of PET. The present process separates non-PET material from PET or a PET monomer precursor (or both). The present invention is applicable to materials containing small amounts of PET (such as certain blended fabrics or waste materials containing some PET) as well as nearly pure PET starting materials (such as end-of-use PET separated from municipal waste).

[0062] Carbon dioxide source

[0063] CO2 is a catalyst in the present process. Thus, a carbon dioxide (CO2) source herein refers to any source that is capable of providing CO2 molecules under the reaction conditions of the present process. The CO2 source can be CO2 itself, but preferably the source is a readily used solid or liquid pre-catalyst chemical that releases CO2 under the reaction conditions. The CO2 source can simultaneously serve as a source of another reactant (such as an amine). Ammonium bicarbonate salt (NH4HCO3) is an example of a combined source of amine (NH3) and CO2.

[0064] Amine source

[0065] An amine is a catalyst in the present process. Thus, an amine source herein refers to any source that is capable of providing a suitable amine molecule (such as NH3) under the reaction conditions of the present process. The amine source can be an amine itself, but preferably the source is a readily used solid or liquid pre-catalyst chemical that releases an amine under the reaction conditions. Ammonia derivatives are also suitable as amine sources. The amine source can simultaneously serve as a source of another reactant (such as CO2). Ammonium bicarbonate salt (NH4HCO3) is an example of a combined source of amine (NH3) and CO2.

[0066] Amine

[0067] Herein, an amine refers to any amine species that is capable of catalyzing the depolymerization reaction (transesterification reaction) of the present invention. Nucleophilic and / or basic amines are preferred to catalyze the process.

[0068] Bis(hydroxyethyl) terephthalate (BHET)

[0069] Bis(hydroxyethyl) terephthalate, abbreviated BHET, is an important industrial chemical used as a precursor monomer for PET, among other uses. Bis(hydroxyethyl) terephthalate is a compound of formula (b):

[0070]

[0071] Textile

[0072] Textile herein refers to any textile that can be combined with a polyester fabric, such as a PET fabric. Common textiles include cotton and viscose. The textile can also comprise other materials that are compatible with or do not interfere with the method of the present invention. The textile is typically a natural (cotton, hemp) or synthetic (other polyesters, polyurethane, viscose, etc.) polymer.

[0073] Blended fabric

[0074] Blended fabric herein refers to a fabric comprising two or more fabric types, i.e. PET and one or more of the above-mentioned textiles. Other materials can also be included, such as leather, rubber, metal (zippers, buttons), as long as they do not adversely affect the method of the present invention.

[0075] The inventors have noted that CO2 is a highly active, readily available, inexpensive, traceless and safe organic transformation catalyst. Moreover, without being bound by theory, the presence of a nucleophilic amine under transamidation conditions suggests a role of the amine in the activation of the carbonyl function: the nucleophilic basic amine co-mediates the double catalysis with Lewis and Bronsted acidic CO2 (in the form of carbonic acid). Thus, the inventors report their investigation of the transesterification of esters, PET bottles and PET-cotton blended fabrics to elucidate the advantage of the combination of catalytic CO2 with an amine-based co-catalyst Figure 1 B).

[0076] Thus, a first aspect of the present invention is a method for the chemical depolymerization of polyethylene terephthalate (PET) comprising the steps of:

[0077] a) providing a PET-containing material;

[0078] b) mixing the PET-containing material of step a) with a source of carbon dioxide, a source of amine or nitrogen and a compound of formula (I):

[0079]

[0080] c) heating the mixture resulting from step b) to a temperature ranging from 130°C to 220°C;

[0081] d) obtaining a product comprising a compound of formula (II):

[0082]

[0083] wherein:

[0084] R is selected from the group consisting of OH and N(R 1 )2;

[0085] X is selected from the group consisting of O and NR 2 ;

[0086] R 1 and R2 each independently is selected from the group consisting of H, methyl, ethyl, propyl, isopropyl, butyl, and isobutyl;

[0087] n is any integer in the range of 1-10.

[0088] PET-based polymers are mainly used for beverage bottles, while one third of the produced PET is blended with cotton-based fibers and viscose fibers for the production of textile fabrics. Thus, in one embodiment, the PET-containing material of step a) is selected from the group consisting of plastic bottles, plastic packaging, and PET-containing textiles, preferably plastic bottles or PET-containing textiles.

[0089] While the present process is suitable for any amount of PET in the PET-containing material, the starting material has preferably a high PET content for the production of BHET. Thus, in one embodiment, the PET-containing material comprises at least 30% of PET, such as at least 40% of PET, such as at least 60% of PET, such as at least 80% of PET, such as at least 90% of PET, such as at least 95% of PET, and most preferably at least 99% of PET.

[0090] Carbon dioxide and amines are catalysts of the process of the present application. Without being bound by theory, both catalysts interact with the ester groups of the PET polymer and the nucleophiles (alcohols and amines) to activate them for the transesterification or amidation reaction with the compound of formula (I).

[0091] In one embodiment, the amine source or nitrogen source is selected from the group consisting of pyridine, ammonium, ammonia, imidazole, hydrazine, morpholine, 4-dimethylaminopyridine (DMAP), piperazine, ethanolamine (MEA), ethylenediamine (EDA), triethylamine (TEA), n-butylamine, di-n-butylamine, pyrrolidine, triazabicyclodecene (TBD), quinine, N-methylmorpholine, and trimethylglycine (TMG), glycine, lysine, hexamethylenetetramine, asparagine, sodium azide, melamine, 1,4-diazabicyclo[2.2.2]octane (DABCO), urea, 2,3,4,6,7,8,9,10-octahydropyrimido[l,2-a]azepine (DBU), potassium cyanide, sodium cyanide, 2-aminopyridine, and quinuclidine, or any combination thereof.

[0092] In a preferred embodiment, the amine source is selected from the group consisting of pyridine, ammonium, ammonia, imidazole, 4-dimethylaminopyridine (DMAP), piperazine, n-butylamine, pyrrolidine, and trimethylglycine (TMG), or any combination thereof.

[0093] In one embodiment, the amine source is selected from the group consisting of ammonium, ammonia, and 4-dimethylaminopyridine (DMAP), preferably ammonium.

[0094] The use of a source of carbon dioxide is essential for the optimal performance of the present process. The source of carbon dioxide is preferably in the form of a solid pre-catalyst. In one embodiment, the source of carbon dioxide is selected from the group consisting of a carbonate, a bicarbonate and carbon dioxide, preferably a bicarbonate.

[0095] In a preferred embodiment, the source of carbon dioxide and the source of amine are combined into a single source of carbon dioxide and amine. The single source of carbon dioxide and amine can be selected from ammonium bicarbonate or ammonium carbonate, preferably ammonium bicarbonate. Both ammonium carbonate and ammonium bicarbonate were tested in Example 2 and were both effective.

[0096] The inventors have adopted ammonium bicarbonate salt (NH4HCO3) as a cheap pre-catalyst (10-25 mol% loading) which readily decomposes to CO2, ammonia and water above 36°C (Equation 1):

[0097]

[0098] These reaction conditions provide practical and mild conditions for all the waste materials tested and allow the recovery of high purity BHET while selectively retaining cotton fabric in the textile waste.

[0099] A sub-stoichiometric catalyst is sufficient to provide good yields in the process of the present invention and therefore, the single source of carbon dioxide and amine can be added in catalytic amounts, for example 5-40 mol%, preferably 10-40 mol%, more preferably 15-30 mol%, most preferably 20-30 mol%, compared to PET.

[0100] The compound of formula (1) can be polyethylene glycol (n = 2-10, X = O, R = OH), or a hydroxyethyl amine [n = 1, X = O, R = N(R 1 )2] or a diamine [n = 1, X = NR 2 , R = N(R 1 )2]. In a preferred embodiment, the compound of formula (1) is ethylene glycol (n = 1, X = O, R = OH). The excess ethylene glycol added can also act as a solvent and / or suspending agent for the PET and other reactants. The ethylene glycol can be added in 5-40 molar equivalents to the PET, preferably 10-30 molar equivalents, more preferably 15-30 molar equivalents, most preferably 20-30 molar equivalents to the PET.

[0101] In another embodiment, the amine (derived from the source of amine) is NH3. Like carbon dioxide, ammonia becomes gaseous, facilitating its removal from the product, while the use of metal-based catalysts such as ZnCl2results in the final product containing metal impurities.

[0102] In one embodiment, the process is carried out under less than 20 wt% water, such as less than 15 wt% water, preferably less than 10 wt% water, more preferably less than 5 wt% water, most preferably less than 1 wt% water, relative to the total reaction.

[0103] In another embodiment, the process is carried out in the absence of water.

[0104] The temperature range applicable in the glycolysis process of PET-based beverage bottles is broad and can vary depending on the reactants used and other parameters such as heating time. Thus, in one embodiment, the temperature of step c) is in the range of 150 °C to 200 °C, preferably 160 °C to 200 °C, more preferably 170 °C to 200 °C, most preferably 180 °C to 200 °C. Since cotton cellulose, which is a component in the blend of PET-containing fabrics, starts to degrade at 200 °C, one embodiment of the present application relates to a temperature of step c) of not more than 200 °C. In one embodiment, the reaction mixture is kept at the temperature of step c) for at least three hours, such as in the range of 3-24 hours, preferably at least 4 hours, more preferably at least 5 hours, most preferably at least 6 hours. In another embodiment, the reaction mixture is agitated, such as stirred, at least during step c).

[0105] The compound of formula (II) can be the most common PET precursor BHET, but also PEGylated derivatives and amine / amide derivatives according to formula (II) which can have other uses.

[0106] In one embodiment, R is H or methyl, preferably H, and in another embodiment, R is H or methyl, preferably H, and in another embodiment, X is O and / or R is OH. In yet another embodiment, n is 1-8, such as 1-6, 1-4, 1-3, 1-2, preferably 1. In the most preferred embodiment, the compound of formula (II) is bis(hydroxyethyl) terephthalate (BHET). 1 In one embodiment, R is H or methyl, preferably H, and in another embodiment, R is H or methyl, preferably H, and in another embodiment, X is O and / or R is OH. In yet another embodiment, n is 1-8, such as 1-6, 1-4, 1-3, 1-2, preferably 1. In the most preferred embodiment, the compound of formula (II) is bis(hydroxyethyl) terephthalate (BHET). 2 In one embodiment, R is H or methyl, preferably H, and in another embodiment, R is H or methyl, preferably H, and in another embodiment, X is O and / or R is OH. In yet another embodiment, n is 1-8, such as 1-6, 1-4, 1-3, 1-2, preferably 1. In the most preferred embodiment, the compound of formula (II) is bis(hydroxyethyl) terephthalate (BHET).

[0107] The process of the present application can achieve a high yield of the compound of formula (II). Thus, in one embodiment, the yield of the compound of formula (II) is at least 60% relative to PET, preferably at least 70%, more preferably at least 80%, most preferably at least 90%.

[0108] The use of metal salts as catalysts can result in metal impurities in the final product, which is not the case for the process of the present application. Thus, in one embodiment, the content of trace metals or salts thereof in the product comprising the compound of formula (II) is less than 1000 ppm, such as 500 ppm, 200 ppm, 100 ppm, such as 80 ppm, 50 ppm, 30 ppm, preferably 10 ppm.

[0109] After catalysis according to the present depolymerization method, CO2 is easily evaporated and the amine catalyst is easily removed by various methods. Since the method has no catalyst residue and also works well below 200 °C, the inventors envision that amine / CO2 catalyzed PET glycolysis can become a practical and scalable method, especially for selectively depolymerizing PET from cotton and other blended fabrics. Cotton-based materials face a major challenge in chemical recycling due to the instability of glycosidic bonds.

[0110] Accordingly, another aspect of the present invention is a method of separating polyethylene terephthalate (PET) and a textile from a blended fabric containing PET and a textile, the method comprising the steps of:

[0111] a) providing a blended fabric containing a textile and PET;

[0112] b) mixing the blended fabric of step a) with a source of carbon dioxide, a source of an amine, and a compound of formula (I):

[0113]

[0114] c) heating the mixture resulting from step b) to a temperature in the range of 130 °C to 220 °C;

[0115] d) obtaining a product comprising a compound of formula (II) and the textile:

[0116]

[0117] e) separating the compound of formula (II) and the textile in the product of step d);

[0118] wherein:

[0119] R is selected from the group consisting of OH and N(R 1 )2;

[0120] X is selected from the group consisting of O and NR 2 ;

[0121] R 1 and R 2 are each independently selected from the group consisting of H, methyl, ethyl, propyl, isopropyl, butyl, and isobutyl;

[0122] n is any integer in the range of 1-10.

[0123] The blended fabric can originate from multiple industries such as clothing and upholstery. Therefore, in one embodiment the blended fabric is selected from the group consisting of clothing, upholstery, carpets and curtains. The PET containing blended fabric can contain a variety of other textiles. Therefore, in one embodiment the textile of step a) is selected from the group consisting of cotton, viscose, lyocell, polyurethane or mixtures thereof. The process of the present invention is capable of depolymerizing PET while leaving the cotton fibers intact, therefore it is preferred that the textile is cotton. In another embodiment the ratio of textile to PET is in the range of 10:1 to 1 :10, such as for example 3:1 to 1 :3, 2:1 to 1 :2, preferably 3:1 to 1 :1, most preferably 2:1 to 1 :1. The process of the present invention is highly selective and it is possible that other components are present in addition to the textile and PET. That is, the separation of BHET and the textile is generally easier in the absence of other components, therefore in one embodiment the blended fabric consists of PET and the textile, i.e. substantially no other components.

[0124] Since cotton cellulose, which is a component of the PET containing blended fabric, starts to degrade at 200 °C, one embodiment of the present invention relates to a temperature of step c) of not more than 200 °C.

[0125] Due to the relatively mild reaction conditions, the process of the present invention is good in optimized yield of the textile. Therefore, in a preferred embodiment the yield of the textile is at least 60%, preferably at least 70%, more preferably at least 80%, most preferably at least 90%. Another advantage of the process of the present invention is the absence of metal catalysts, which are typically present in processed textiles and PET. Therefore, in the product containing the compound of formula (II) and / or the textile, the content of trace metals or salts thereof is preferably below 1000 ppm, such as 500 ppm, 200 ppm, 100 ppm, such as for example 80 ppm, 50 ppm, 30 ppm, such as preferably 10 ppm.

[0126] According to the process of the present invention, a variety of methods are known to the person skilled in the art to separate the textile and the compound of formula (II). These methods can be adjusted and optimized depending on the presence of other components and the physical properties of the compound of formula (II). Typically the compound of formula (II) is dissolved in the solvent used (such as the compound of formula (I)), therefore it can be separated by filtration. Therefore, in one embodiment the compound of formula (II) and the textile are separated using filtration, preferably hot filtration.

[0127] The textile can be further purified by various methods known or improved by those skilled in the art. In one embodiment, the textile is further purified by washing using a composition selected from the group consisting of water, organic solvents, surfactants and any mixture thereof. More specifically, the cotton residue obtained by the process of the present application is washed with water, ethanol and diethyl ether. Thus, in one embodiment, the textile is washed with water, ethanol and diethyl ether. The compound of formula (II) can be further isolated and purified by standard methods for small molecules, for example, BHET can be purified by crystallization. Thus, in one embodiment, the compound of formula (II) is further purified using a method selected from the group consisting of crystallization and column chromatography, preferably crystallization. In another embodiment, the blended textile is added to the reaction as part of a composition containing other polymers.

[0128] It is noted that embodiments and features described in relation to one aspect of the present application are equally applicable to the other aspects of the present application. In particular, embodiments described in relation to the first aspect of the present application relating to a method for chemical depolymerization of PET are equally applicable to the separation of (PET) and textile from blended textiles with necessary modifications.

[0129] All patents and non-patent literature cited herein are incorporated by reference in their entirety.

[0130] The present application will be described in more detail below by way of non-limiting examples.

[0131] Examples

[0132] Example 1: NH4HCO3 catalyzed transesterification of ethylene glycol and its derivatives

[0133] Study Objectives

[0134] The present study aims to establish a metal-free transesterification protocol by investigating the yield of products obtained using different transesterification reactions of ethylene glycol ( Figure 2A ) and its derivatives ( Figure 2B ). The reactions were carried out under catalysis by NH4HCO3 or without a catalyst under N2atmosphere to verify whether NH4HCO3 is suitable as a catalyst for transesterification reactions.

[0135] Materials and Methods

[0136] The ester (1.0 mmol), alcohol (10.0 mmol, 10 equiv.) and ammonium bicarbonate (12-25 mol%) were added to a vial (8 ml) with a magnetic stirrer. The vial was stirred at 130-150 °C and the conversion was monitored by 1 The conversion was monitored by H NMR spectroscopic analysis of an aliquot of the reaction mixture. After complete conversion, the reaction mixture was directly purified by silica gel chromatography to isolate the target product.

[0137] Results

[0138] The applicability of this method to depolymerization was confirmed by testing the glycolysis of vinyl sugars using model substrates (methyl ester and ethyl ester, 1). Figure 2A Under mild reaction conditions (80-150℃), a catalytic amount of NH4HCO3 (12-25 mol%) can cause methyl or ethyl ester (1) to undergo transesterification with ethylene glycol (2a, 10 equivalents) to obtain the target glycolysis product (3). The tested transesterification substrates were unreactive under catalyst-free conditions. Figure 2A (Medium gray percentage); only trace amounts of the product were detected under a nitrogen atmosphere (for the reaction mixture). 1 ¹H NMR spectroscopy analysis detected conversions as high as 28%. Under catalytic conditions, regardless of the electronic properties of the substrate, good to high yields of ethylene glycol esters ranging from 19% to 91% were obtained. Figure 2A (Percentage of black in the middle). Using diethyl terephthalate (1m) as a model substrate for PET depolymerization, a reasonable separation yield of BHET (3m) (57%) was provided under catalytic conditions of 80°C, while simultaneously generating a monosubstituted product (36%) (3m'), indicating that substrate 1m is close to quantitative conversion (via 1 HNMR analysis showed complete conversion. Encouraged by this result, the inventors further investigated whether the NH4HCO3 catalyst was suitable for the transesterification of other ethylene glycol derivatives (i.e., oligomers (ethylene glycol) 2a-2k), which could produce thermoresponsive polymers. Figure 2B Under conditions of increased temperature and higher catalyst loading (25 mol%, 150 °C), this method yields selective monoesterification products with moderate separation yields (up to 55% separation yield (2c)). 2-(dimethylamino)ethanol (2h) yields transesterification products in moderate yields. Conversely, the conversion of monomethyl ether analogs (2e-2g) does not decrease significantly, demonstrating the importance of diol functional groups in catalytic transesterification: polarity, hydrogen bond donor capability, and dipole moment are crucial for carbonyl activation.

[0139] Conclusions

[0140] When using NH4HCO3 as a catalyst, the transesterification reactions of methyl and ethyl esters with ethylene glycol are more efficient, with higher yields (19-91%) of different model substrates than those under N2 atmosphere without a catalyst (<1-28%). Furthermore, transesterification reactions can also be carried out using ethylene glycol derivatives, particularly oligomeric (ethylene glycol) and 2-(dimethylamino)ethanol.

[0141] Example 2: Optimization of glycolysis reaction conditions for PET-based beverage bottles

[0142] Study Objectives

[0143] Having established a metal-free transesterification protocol, the inventors turned their attention to PET substrates to generate the monomer BHET. The glycolysis of PET beverage bottles needs to be further optimized to provide practical reaction conditions to obtain high purity BHET. It is worth noting that small amounts of metal impurities generated during the catalyst and pre-treatment processes can decrease the quality of the recovered PET, thus affecting the value of the entire recycling process. Therefore, the present study aimed to optimize the reaction conditions for the glycolysis of PET beverage bottles by varying the equivalents of ethylene glycol and CO2, the catalyst used, and the reaction temperature.

[0144] Materials and Methods

[0145] PET substrate (2.0 mmol), ethylene glycol (25 equivalents), and catalyst were added to a vial (8 mL, or a 250 mL round bottom flask for scaled-up reactions) with a magnetic stir bar. The vial was stirred at 150-200 °C for 6-24 h. An aliquot of the reaction mixture was analyzed by1H NMR in DMSO-d6 using 1,3,5-trimethoxybenzene as an internal standard. 1 H NMR yield. To determine the conversion and yield of BHET, the reaction mixture was filtered to remove oligomers, unreacted, and residual PET substrate. The filtrate was added to cold water, and BHET was precipitated at 4 °C. The crystallized BHET was washed with cold water and diethyl ether to remove excess ethylene glycol, and the isolated yield of BHET was determined after drying.

[0146] Results

[0147] The inventors utilized various catalytic systems to further optimize the glycolysis reaction conditions of beverage bottles as a depolymerization substrate with and without CO2(Table 1). The inventors first confirmed that no background glycolysis occurred without a catalyst (150-200 °C; Table 1; entry 1). The use of catalytic amounts of CO2(15-30 mol%) and a reaction atmosphere (1 atm) did not have any effect without a catalyst (Table 1; entry 2). The addition of the catalyst DMAP (30 mol%) resulted in a higher yield of BHET (44%, Table 1; entry 4) than when DMAP was used without CO2(24%; Table 1; entry 3). This set of experiments confirmed the positive effect of CO2on PET depolymerization when DMAP was used as a catalyst (30 mol%).

[0148] Table 1:

[0149]

[0150] a1H NMR in DMSO-d6 using 1,3,5-trimethoxybenzene as an internal standard 1HNMR spectroscopy was used to determine the yield of BHET. bThe reaction time was extended to 24 hours.

[0151] The inventors further optimized the equivalents of ethylene glycol (EG) used in the reaction: 40% yield of BHET was obtained using 10 equivalents of EG (Table 1; entry 5). Next, the inventors further optimized the conditions with the aim of increasing the conversion of BHET, assuming that the recovery of EG would be negligible due to its higher boiling point. When the inventors replaced the DMAP / CO2 combination with NH4HCO3, higher yields were obtained with 10-25 equivalents of EG (Table 1; entries 6-7). The optimization resulted in a BHET yield of 84% after 6 hours of reaction at 180 °C, highlighting its unique selectivity towards the monomer. The reaction was further tested at a larger scale (50 mmol, 9.6 g of a waste PET bottle, Table 1; entry 8), resulting in a high selectivity and isolated yield of BHET (>70%, HPLC purity up to 99.8%) without the need for any complex purification steps, as all catalytically active species were evaporated. The advantage of this protocol is that the BHET product crystallizes upon the addition of cold deionized water (6% V / V) to the filtrate after hot filtration, which demonstrates the energy economic advantage of carbon dioxide catalyzed glycolysis, considering the need for vacuum distillation after the methanolysis of PET. Also, the conversion of the same reaction without a catalyst was negligible (by HPLC analysis of the reaction mixture) and the BHET product was not isolated. 1 HNMR spectroscopy analysis was 7%, highlighting the role of CO2 and amine in catalytic glycolysis. Ammonium bicarbonate (NH4HCO3) was previously used as a catalyst for Knoevenagel condensation reactions, which decomposes at high temperatures and generates NH3 and CO2 in situ to act as acid and base catalysts, respectively (see equation 1 above).

[0152] Since metal catalysts were used for PET glycolysis, a representative Zn-based Lewis acid catalyst was tested herein. Zn(OAc)2(Table 1; entries 10 and 11) showed lower to better BHET yields, but elemental analysis of the isolated BHET showed significant metal impurities (data not shown), likely due to residual zinc. Ammonium carbonate ((NH4)2CO3, Table 1; entry 12) gave comparable results to the ammonium bicarbonate catalyst, with better BHET yields (87% yield, Table 1; entry 12), while strong inorganic bases (KOH, Na2CO3, NaOH) resulted in BHET contamination with hydrolysis products terephthalic acid (TPA) (data not shown).

[0153] The reactions were scaled up to larger scales (2-50 g of PET) using the catalysts listed in Table 2, with fixed equivalents of ethylene glycol (25 equivalents), at 180 °C for 6 hours (unless otherwise stated). The isolated yield of BHET was determined simultaneously.

[0154] Table 2:

[0155]

[0156]

[0157] aReaction conditions: PET bottle bottoms (0.2-50 g); catalyst and ethylene glycol were added with a magnetic stir bar and the vial was heated for 6 h; conversion (%) = (W 低聚物+BHET / W PET瓶 ) x 100, W = weight. The reaction mixture was diluted with water to precipitate the oligomers and BHET, which was crystallized to determine the isolated BHET yield.bReaction time was extended to 24 h.

[0158] Without catalyst, even with a longer reaction time (up to 24 h, temperature 150-200 °C), there was no background glycolysis. Catalytic amounts of CO2(15-30 mol%) and reaction atmosphere (1 atm) did not show any effect (Table 2; entry 1). Zn-based Lewis acidic catalysts known for glycolysis, such as Zn(OAc)2and ZnCl2(Table 2; entries 2 and 3), showed low to good BHET conversion (44% and 75%, respectively). However, isolated BHETs using the same purification sequence (hot filtration and crystallization) generally showed varying degrees of metal impurities (data not shown) likely due to residual zinc ions. Using the organic catalyst DMAP (30 mol%) under N2conditions gave 63% conversion and 46% isolated BHET yield (Table 2; entry 4). Addition of catalytic amounts of CO2(30 mol%) gave higher conversion and BHET yield compared to DMAP alone (Table 2; entry 5), confirming the positive role of CO2in glycolysis.

[0159] Catalytic NH4HCO3showed comparable activity to metal catalysts (Table 2; entries 6 and 7) achieving >50% BHET separation yield in a single crystallization step. High purity BHET (HPLC purity up to 99.8%) was obtained after hot filtration followed by a single crystallization operation with the addition of cold DI water (6% V / V) as all catalytic species and ethylene glycol were easily removed (data not shown). The effect of ammonia as the sole catalyst (in water or methanol) and in the absence of CO2was inferior to NH4HCO3(Table 2; entry 8), confirming the importance of the dual catalysis of CO2and ammonia for the performance optimization of the glycolysis of PET. Under the optimized conditions, the quantitative conversion of PET was achieved in a larger scale (260 mmol, 50 g of waste PET bottle substrate) with a selectivity to BHET of 51% and a separation yield of 64% (Table 2; entry 9). It is worth noting that under the catalytic conditions tested, no cyclic carbonates or ureas were formed from the catalytic species and ethylene glycol.

[0160] Conclusions

[0161] The dual catalysis of ammonia or ammonium with CO2is crucial for the performance optimization of the catalytic glycolysis of PET-based beverage bottles. ZnCl2catalyst, although effective for PET depolymerization, significant metal impurities were observed by elemental analysis of the isolated BHET, which can be due to the presence of residual zinc. Therefore, ammonia or ammonium with a source of CO2is a highly efficient catalyst for PET depolymerization, which allows the production of “virgin” PET with similar or identical quality to that of non-recycled PET.

[0162] Example 3: Glycolysis of PET in a blended fabric

[0163] Study Objectives

[0164] After successfully applying the process to the chemical recycling of PET waste bottles (Example 2), the inventors attempted to test the reaction conditions for a blended fabric. Therefore, the objective of this study was to explore different reaction conditions for the depolymerization of PET in a blended fabric, as well as the corresponding recovery of cotton in a PET:cotton blended fabric.

[0165] Materials and Methods

[0166] Textile substrate (2.0 g of polyester), ethylene glycol (25 equivalents, 15.8 mL) and ammonium bicarbonate (25 mol%) were added to a vial (40 ml) with a cross magnetic stir bar. The vial was stirred at 160-190 °C for 6-24 hours. Control experiments were performed without ammonium bicarbonate but under N2atmosphere. The aliquot in DMSO-d6was analyzed with 1,3,5-trimethoxybenzene as internal standard 1HNMR yield. The reaction mixture was filtered hot to remove solid residues and insoluble oligomers, then washed with 5 mL of water. The combined filtrate was cooled to 4 °C to crystallize BHET. The purity of BHET was confirmed by HPLC (conditions: column: Kromasil 5-AmyCoat (4.6 x 250 mm); isopropanol / n-heptane (60 / 40, v / v), 0.5 mL / min, 8.9 MPa; detector A: 220 nm; detector B: 254 nm).

[0167] Results

[0168] The inventors determined that NH4HCO3was the optimal catalyst to obtain high 1 HNMR yield of BHET (62%) and quantitative yield of recovered cotton Figure 3A ) from a blended textile (62% polyester, 33% viscose, 5% spandex, based on weight percentage of commercial labels). A time-yield curve of BHET was plotted over 6 hours of the reaction, illustrating the positive effect of catalysis Figure 3B ) under N2atmosphere. Higher reaction temperature (190 °C, solid circle) showed higher BHET yield under both catalytic and non-catalytic conditions compared to lower temperature (180 °C), while the use of catalyst (25 mol%) achieved higher BHET yield compared to the reaction without catalyst Figure 3B

[0169] Cotton recovery from PET / cotton blended textiles was subsequently investigated. The instability of glycosidic bonds of cotton material should be considered when selective PET depolymerization is an ideal parallel process. To avoid acid and base-mediated hydrolysis of cotton material, it is important to mediate depolymerization under mild, neutral conditions in order to provide recovered cotton for the textile and other industries. The inventors analyzed the reaction mixture under catalytic conditions to detect the extent of polymer degradation over time. In addition, recovered cotton residues were analyzed by optical microscopy, thermogravimetric analysis (TGA), infrared spectroscopy, solid 13 state NMR spectroscopy, and elemental analysis. BHET and cotton were recovered Figure 4A ) during large-scale glycerolysis of PET / cotton blended textiles. When a T-shirt containing 75% PET with 71% conversion was glycerolyzed, 47% BHET and 92% cotton and viscose were recovered. When a sofa cover (213 g of textile with 47% polyester and 53% cotton) was glycerolyzed, 62% BHET and 94% cotton were recovered. In the absence of catalyst, the residues recovered from the reaction showed the same signals as the starting material, which is consistent with 1 HNMR yield detected by NMR spectroscopy Figure 4B ​On the other hand, residual samples obtained from the reaction mixture containing the catalyst showed signals similar to those of commercially available cotton balls, at 130-163 ppm (aromatic signals and carbonyl compounds of PET), indicating complete degradation of PET, while also showing the characteristics of cotton. 13 C signal ( Figure 4B ).from Figure 4C The optical microscope images clearly show that, compared with those using Zn 2+ Compared to cotton recovered via glycolysis, cotton recovered using an NH4HCO3 catalyst (right) is more comparable to the substrate image; that is, the cotton recovered by this invention is more efficient than that recovered using Zn. 2+ Cotton recovered through glycolysis is more "original" ( Figure 4C Considering the further utilization of cotton and BHET, the inventors demonstrated that, compared to heavy metal catalysis (such as ZnCl2), traceless NH4HCO3 is more practical for large-scale applications due to catalyst residue, as detected by elemental analysis of the recovered cotton and BHET (data not shown). Furthermore, the inventors noted that selective depolymerization can be achieved by using NH4HCO3, while heavy metal catalysts lead to cotton degradation. 80x microscopic observation showed that the residue recovered after reaction with the catalyst only exhibited cotton fibers similar to commercially available cotton balls. Figure 4D ).

[0170] Thermogravimetric analysis showed that commercially available cotton balls (solid line, *) and the residue separated after the catalytic reaction (solid line, ¤) had the same one-step mass loss. Figure 5A This indicates that polyester selectively degrades from textiles. Similar two-step mass losses were observed in the starting material (solid line, ^) and the residue recovered after glycolysis without NH4HCO3 catalyst (solid line, #). The corresponding DTG spectra are shown as dashed lines. The first-step mass loss (25% and 30%, respectively) can be attributed to the decomposition of cotton (15% viscose and 10% cotton). The infrared spectrum of the recovered cotton (*) is close to that of commercially available cotton balls (¤), while the IR spectrum of the residue recovery without NH4HCO3 catalyst (^) is similar to that of the starting material (#). Figure 5B ).

[0171] Conclusions

[0172] The method of the present invention can be used to efficiently recover BHET and cotton from PET / cotton blended fabrics, with no trace metals in the product and a high yield.

[0173] Example 4: Depolymerization of PET in PET-containing blended fabrics in the presence of other components

[0174] Study Objectives

[0175] To explore the selectivity of the reaction towards PET in the presence of multiple other components and to see if BHET and textiles can be isolated from the resulting mixture.

[0176] Materials and Methods

[0177] A waste mimicking glycolysis reaction was performed using 42.7 g of blended fabric (PET: Cotton = 75:25, based on weight percentage from the product label) with ethylene glycol (25 equivalents) following the procedure described in Example 3, and the following components were further added to the reaction mixture: polypropylene, lego, polyurethane, polystyrene, acrylonitrile butadiene rubber (NBR), acrylonitrile-butadiene-styrene (ABS), hair, polyamide (PA), polyethylene (PE), styrene-ethylene-butylene-styrene (SEBS), polyoxymethylene (POM), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), and polyurethane (PU).

[0178] Results

[0179] The inventors mixed multiple plastics (PVC, PP, PE, polyamide, PS, ABS, POM, and SEBS, PU) to mimic real-life plastic waste and verified the selective glycolysis of PET Figure 7 ) under standard reaction conditions. A 23% yield of BHET and 75% recovered cotton were obtained after recrystallization, and the other plastics had some deformation upon collection but no clear signs of chemical depolymerization. It was confirmed that the pre-catalyst NH4HCO3 was formed during the reaction and the catalyst could be recovered by simple sublimation.

[0180] Conclusions

[0181] The method of the invention can be used selectively in the presence of multiple other waste and chemicals and textiles and BHET can be isolated.

[0182] Example 5: Depolymerization using different base catalysts: PET

[0183] Study Objectives

[0184] The aim of this study was to investigate if other base catalysts or other amine sources could be used to depolymerize PET in PET-based beverage bottles.

[0185] Materials and Methods

[0186] PET substrate (1.0 mmol), ethylene glycol (25 equivalents), base additive and carbon dioxide were added to a vial (8 mL) containing a magnetic stir bar. The vials were sealed with nitrogen or vacuum and then CO2 was added to some of the vials (see Table 3 for details).

[0187] NMR yields were determined with aliquots in DMSO-d6 using 1,3,5-trimethoxybenzene as an internal standard. 1 HNMR yields. To determine the conversion and yield of BHET, the reaction mixture was filtered to remove oligomers, unreacted and remaining PET substrate. Water was added to the filtrate and BHET was precipitated at 4°C. The crystallized BHET was washed with cold water and diethyl ether to remove excess ethylene glycol and dried to determine the isolated yield of BHET.

[0188] Results

[0189] Studies with a variety of organic and inorganic bases showed that the conversion of PET to BHET was related to the pKa of the base catalyst (Table 3). The highest conversion was obtained with weak bases (pKa ~ 6) in the presence of 25 mol% CO2.

[0190] These results show that the glycolytic reaction mechanism follows general base catalysis and highlights the key catalytic role of catalytic carbon dioxide in reactions involving weak bases, especially ammonia obtained by thermal decomposition from NH4HCO3. These results also show that a variety of different amine sources can be used to depolymerize the PET described in the present invention.

[0191] Table 3:

[0192]

[0193]

[0194]

[0195]

[0196] NMR yields were determined with aliquots in DMSO-d6 using 1,3,5-trimethoxybenzene as an internal standard.

[0197] Conclusions

[0198] This example shows that several different sources of amine can be used in combination with carbon dioxide to depolymerize PET.

[0199] Example 6: Base screening of different Lewis bases for PET-blend textile glycolysis

[0200] Study Objectives

[0201] This study aims to investigate whether other base catalysts or other amine sources can be used to depolymerize PET in PET-blend textiles.

[0202] Materials and Methods

[0203] PET-blend textiles (1 g) with 65% PET and 35% cotton, ethylene glycol (25 equivalents, 6.65 mL), and various bases (25 mol%) were added to two vials (40 mL) fitted with a cross-magnetic stir bar. The first vial was sealed with N2, and the second vial was vacuum sealed before 25 mol% CO2 was added and stirred at 180 °C for 6 h.

[0204] The reaction mixture was filtered hot to remove solid residues and insoluble oligomers, and the remaining fabric was isolated. It was then washed with an appropriate amount of water to remove residual product and ethylene glycol. The filtered recovered substrate was dried overnight to remove residual ethylene glycol. The combined filtrate was cooled in ice water to crystallize BHET. The crystallized BHET was collected by filtering again. The BHET and recovered substrate were weighed to obtain the yield.

[0205] Results

[0206] Based on the base screening results of PET bottles in Example 5, the base with the highest BHET yield was chosen for the screening of PET-blend textiles. Some were under N2 conditions, some were under 25 mol% CO2 conditions, and some were under both conditions. Various criteria were considered, such as high yield of BHET, color of the recovered substrate, and condition of the recovered substrate (Table 4). It was found that some of the recovered substrates had a yield higher than 100%, but this could be due to incomplete evaporation of ethylene glycol or incomplete conversion of PET in the textile.

[0207] Bases such as sodium hydroxide and sodium cyanide caused severe decolorization of the fabric, which was undesirable. The best BHET yield (66%) and color of the recovered substrate were obtained using di-n-butylamine. The reaction using zinc chloride showed an overall best yield of BHET of 78%, but it only degraded the cotton to the extent of a recovered white flake. The reaction using NH4HCO3 showed a yield of 27%. The relatively low yield compared to what was observed in Example 3 can be explained by the fact that this reaction was only run for 6 hours. In previous work, when the reaction was run overnight, a yield of 70% was observed, and the quality of the recovered substrate was good. Figure 7 Figures 7A and 7B show example pictures of BHET yield and recovered substrate for zinc acetate, sodium hydroxide, triethylamine, and ammonium bicarbonate bases, respectively.

[0208] Table 4: Base screening of different Lewis bases for PET-blend textile glycolysis

[0209]

[0210]

[0211]

[0212] Conclusions

[0213] This example shows that several different amine sources can be used in combination with carbon dioxide to depolymerize PET and recover BHET and textile in PET-blended textiles.

[0214] Example 7: Glycolysis of PET bottles in the presence of water

[0215] Study Objectives

[0216] The aim of this study was to investigate the tolerance of the glycolysis reaction to water.

[0217] Materials and Methods

[0218] In four vials (8 mL) equipped with a magnetic stirrer, 1 mmol of PET, 25 equivalents of ethylene glycol and 25 mol% of catalyst were added. Then, 1, 5 or 10 wt% of H2O was added in the different vials and the reaction was carried out at 180 °C for 6 hours. The yield was determined by analyzing an aliquot in DMSO-d6 with 1,3,5-trimethoxybenzene as internal standard. 1 H NMR yield.

[0219] Results

[0220] To test the tolerance of the reaction to water, different weight percentages of H2O were added to the reaction. As it can be clearly seen in Table 5, the reaction works best with little or no water. As more water is added, the yield changes drastically, but even with up to 10 wt% of water added, the yield is still moderate to good.

[0221] Table 5: Glycolysis of PET bottles in the presence of different weight percentages of water

[0222]

[0223]

[0224] Conclusions

[0225] This example shows that the glycolysis of PET bottles according to the present application can be carried out in the presence of water, preferably with a water content of less than 10 wt%.

[0226] References

[0227] M. Ghaemy et al., Polymer Degradation and Stability, Vol. 90, Issue 3, December 2005, pages 570-576

[0228] WO 2015 / 056377

[0229] Item

[0230] 1. A method for chemical depolymerization of polyethylene terephthalate (PET) comprising the steps of:

[0231] a) providing a PET-containing material;

[0232] b) mixing the PET-containing material of step a) with a source of carbon dioxide, a source of amine and a compound of formula (I):

[0233]

[0234] c) heating the resulting mixture of step b) to a temperature range of 130 °C to 220 °C;

[0235] d) obtaining a product comprising a compound of formula (II):

[0236]

[0237] wherein:

[0238] R is selected from the group consisting of OH and N(R 1 )2;

[0239] X is selected from the group consisting of O and NR 2 ; and

[0240] R 1 and R 2 are each independently selected from the group consisting of H, methyl, ethyl, propyl, isopropyl, butyl and isobutyl;

[0241] n is an arbitrary integer in the range of 1-10.

[0242] 2. The method according to item 1, wherein the source of amine is selected from the group consisting of ammonium, ammonia and 4-dimethylaminopyridine (DMAP), preferably ammonium.

[0243] 3. The method according to any one of the preceding items, wherein the source of carbon dioxide is selected from the group consisting of carbonate, bicarbonate and carbon dioxide, preferably bicarbonate.

[0244] 4. The method according to any one of the preceding items, wherein the source of carbon dioxide and the source of amine are combined into a single source of carbon dioxide and amine.

[0245] 5. The method according to any one of the preceding, wherein the single source of carbon dioxide and amine is ammonium bicarbonate or ammonium carbonate, preferably ammonium bicarbonate.

[0246] 6. The method according to any one of the preceding, wherein the temperature range of step c) is 150 °C to 200 °C, preferably 160 °C to 200 °C, more preferably 170 °C to 200 °C, most preferably 180 °C to 200 °C.

[0247] 7. The method according to any one of the preceding, wherein X is O.

[0248] 8. The method according to any one of the preceding, wherein R is OH.

[0249] 9. The method according to any one of the preceding, wherein n is 1-8, such as 1-6, 1-4, 1-3, 1-2, preferably 1.

[0250] 10. The method according to any one of the preceding, wherein the compound of formula (II) is bis(hydroxyethyl) terephthalate (BHET).

[0251] 11. The method according to any one of the preceding, wherein the content of trace metals or salts thereof in the product comprising the compound of formula (II) is below 1000 ppm, such as 500 ppm, 200 ppm, 100 ppm, such as 80 ppm, 50 ppm, 30 ppm, such as preferably 10 ppm.

[0252] 12. A method of separating polyethylene terephthalate (PET) and textile from a blended textile comprising textile and PET, the method comprising the steps of:

[0253] a) providing a blended textile comprising textile and PET;

[0254] b) mixing the blended textile in step a) with a source of carbon dioxide, a source of amine and a compound of formula (I):

[0255]

[0256] c) heating the resulting mixture in step b) to a temperature in the range of 130 °C to 220 °C;

[0257] d) obtaining a product comprising a compound of formula (II) and textile:

[0258]

[0259] e) separating the compound of formula (II) and textile in the product in step d);

[0260] wherein:

[0261] R is selected from the group consisting of OH and N(R 1 )2;

[0262] X is selected from the group consisting of O and NR 2 ;

[0263] R 1 and R 2 are each independently selected from the group consisting of H, methyl, ethyl, propyl, isopropyl, butyl and isobutyl;

[0264] n is any integer in the range of 1-10.

[0265] 13. The method according to item 12, wherein the textile of step a) is selected from cotton, viscose, lyocell, polyurethane or mixtures thereof, preferably cotton.

[0266] 14. The method according to any one of items 12-13, wherein the ratio of the textile to PET is in the range of 10:1 to 1 :10, such as 3:1 to 1 :3, 2:1 to 1 :2, preferably 3:1 to 1 :1, most preferably 2:1 to 1 :1.

[0267] 15. The method according to any one of items 12-14, wherein the content of trace metals or salts thereof in the product comprising the compound of formula (II) and the textile is less than 1000 ppm, such as 500 ppm, 200 ppm, 100 ppm, such as 80 ppm, 50 ppm, 30 ppm, such as preferably 10 ppm.

Claims

1. A method for chemical depolymerization of polyethylene terephthalate (PET) comprising the steps of: a) providing a PET-containing material; b) mixing the PET-containing material of step a) with a source of carbon dioxide, a source of amine and a compound of formula (I): c) heating the resulting mixture of step b) to a temperature in the range of 130 °C to 220 °C; d) obtaining a product comprising a compound of formula (II): wherein: n is any integer in the range of 1-10, and the source of amine is selected from the group consisting of pyridine, ammonium, ammonia, imidazole, hydrazine, morpholine, 4-dimethylaminopyridine (DMAP), piperazine, ethanolamine (MEA), ethylenediamine (EDA), triethylamine (TEA), n-butylamine, di-n-butylamine, pyrrolidine, triazabicyclodecene (TBD), quinine, N-methylmorpholine, trimethylglycine (TMG), glycine, lysine, hexamethylenetetramine, asparagine, sodium azide, melamine, 1,4-diazabicyclo[2.2.2]octane (DABCO), urea, 2,3,4,6,7,8,9,10-octahydropyrimido[l,2-a]azepine (DBU), potassium cyanide, sodium cyanide, 2-aminopyridine and quinuclidine, or any combination thereof.

2. The method according to claim 1, wherein the source of amine is selected from the group consisting of ammonium, ammonia and 4-dimethylaminopyridine (DMAP), preferably ammonium.

3. The method according to any one of the preceding claims, wherein the source of carbon dioxide is selected from the group consisting of carbonates, bicarbonates and carbon dioxide, preferably bicarbonates.

4. The method according to any one of the preceding claims, wherein the source of carbon dioxide and the source of amine are combined into a single source of carbon dioxide and amine.

5. The method according to any one of the preceding claims, wherein the single source of carbon dioxide and amine is ammonium bicarbonate, ammonium carbonate or ethylenediamine carbon dioxide adduct, preferably ammonium bicarbonate.

6. The method according to any one of the preceding claims, wherein the temperature range of step c) is in the range of 150 °C to 200 °C, preferably 160 °C to 200 °C, more preferably 170 °C to 200 °C, most preferably 180 °C to 200 °C. R is selected from the group consisting of OH and N(R 1 )2; X is selected from the group consisting of O and NR 2 consisting of: R 1 and R 2 each independently is selected from the group consisting of H, methyl, ethyl, propyl, isopropyl, butyl, and isobutyl; 7. The method according to any one of the preceding claims, wherein X is O.

8. The method according to any one of the preceding claims, wherein R is OH.

9. The method according to any one of the preceding claims, wherein n is 1-8, such as 1-6, 1-4, 1-3, 1-2, preferably 1.

10. The method according to any one of the preceding claims, wherein the compound of formula (II) is bis(hydroxyethyl) terephthalate (BHET).

11. The method according to any one of the preceding claims, wherein the product comprising the compound of formula (II) has a content of trace metals or salts thereof below 1000 ppm, such as 500 ppm, 200 ppm, 100 ppm, such as 80 ppm, 50 ppm, 30 ppm, such as preferably 10 ppm.

12. A method for separating polyethylene terephthalate (PET) and textile from a blended textile comprising PET and textile, the method comprising the steps of: ​ ​ ​ ​ ​ ​ ​ a) providing a blend textile comprising a textile and PET; b) mixing the blend textile in step a) with a source of carbon dioxide, a source of amine and a compound of formula (I): c) heating the mixture obtained in step b) to a temperature in the range of 130 °C to 220 °C; d) obtaining a product comprising a compound of formula (II) and a textile: e) isolating the compound of formula (II) and the textile in the product in step d); wherein: R is selected from the group consisting of OH and N(R 1 )2; X is selected from the group consisting of O and NR 2 consisting of: R 1 and R 2 each independently is selected from the group consisting of H, methyl, ethyl, propyl, isopropyl, butyl, and isobutyl; n is any integer in the range of 1-10.

13. The method according to claim 12, wherein the textile of step a) is selected from the group consisting of cotton, viscose, lyocell, polyurethane or mixtures thereof, preferably cotton.

14. The method according to any one of claims 12-13, wherein the ratio of the textile to PET is in the range of 10:1 to 1:10, such as 3:1 to 1:3, 2:1 to 1:2, preferably 3:1 to 1:1, most preferably 2:1 to 1:

1.

15. The method according to any one of claims 12-14, wherein the product comprising the compound of formula (II) and the textile has a content of trace metals or salts thereof of less than 1000 ppm, such as 500 ppm, 200 ppm, 100 ppm, such as 80 ppm, 50 ppm, 30 ppm, such as preferably 10 ppm.

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