Method for purifying mono-ethylene glycol

Abstract

The present invention relates to a method for purifying and recovering monoethylene glycol (MEG) from a solution obtained from the depolymerization of at least one polyester having at least one mono-ethylene glycol (MEG) unit. This solution is preferably obtained from the enzymatic depolymerization of polyethylene terephthalate (PET) contained in plastic products under alkaline conditions. The present invention also relates to a method for recycling polymer-containing materials such as plastic products containing at least one polyester having at least one MEG unit, such as PET, and recovering its monomers.

Description

Technical Field

[0001] Technical Field The present invention relates to a method for purifying and recovering monoethylene glycol (MEG) from a solution obtained from the depolymerization of at least one polyester having at least one MEG unit. Preferably, the solution is obtained from the enzymatic depolymerization of polyethylene terephthalate (PET) contained in plastic products under alkaline conditions. In addition, the present invention relates to a method for recycling polymer-containing materials such as plastic products containing at least one polyester having at least one MEG unit, such as PET, and recovering its monomers. The method of the present invention is particularly useful for decomposing plastic products containing polyethylene terephthalate.

Background Art

[0002] Background Plastics are inexpensive and durable materials that can be used to manufacture a variety of products for a wide range of applications (such as food packaging, textile products, etc.). Therefore, the production of plastics has been increasing exponentially for decades. Furthermore, most of them are used for single-use disposable applications, such as packaging, agricultural films, disposable consumer goods, or short-lived products that are discarded within one year of manufacture. Due to the durability of the polymers contained, large amounts of plastics continue to accumulate in landfills and natural habitats around the world, leading to an exacerbation of environmental problems. As an example, in recent years, polyethylene terephthalate (PET), an aromatic polyester produced from terephthalic acid and mono-ethylene glycol, has been widely used in the production of numerous products consumed by humans, such as food and beverage packaging (e.g., bottles, convenient-sized soft drinks, pouches for nutritional supplements) or textile products, fabrics, carpets, rugs, etc.

[0003] To mitigate the environmental and economic impacts associated with the accumulation of plastic waste, various solutions have been studied, from plastic degradation to plastic recycling. Mechanical recycling technology remains the most commonly used technology, but it has some drawbacks. In fact, the technology requires large-scale and costly sorting, leading to a grade-down in applications due to the overall loss of molecular weight during the process and the presence of uncontrolled additives in the recycled products. Also, current recycling technologies are expensive. As a result, recycled plastic products are generally less competitive compared to virgin plastics.

[0004] Also, chemical and enzymatic recycling of plastic products have been developed and described (e.g., WO 2014 / 079844, WO 2015 / 097104, WO 2015 / 173265, WO 2017 / 198786, and WO 2020 / 094646). These technologies enable the recovery of the chemical components of polymers in the form of monomers and / or oligomers. There is a high interest in the development of optimal methods for the hydrolysis of polyester waste, such as PET waste, to recover terephthalic acid (TA) and mono-ethylene glycol (MEG). Several recycling methods have been reported, including chemical recycling or recycling using hydrolytic enzymes of polyesters. Methods for recovering TA have already been described (e.g., WO 2020 / 094661), and the purification of MEG is usually carried out by distillation. Since the recovered monomers / oligomers can then be purified and used to remanufacture plastic products of equivalent quality to virgin plastic products, such methods offer the potential for infinite recycling of plastics.

[0005] However, the drawbacks of the depolymerization of polyesters such as PET, for example, the alkaline depolymerization of PET, are that a large amount of dicarboxylates, by-products (e.g., DEG, TEG) and other inorganic impurities that are not completely removed during the TA purification method are generated in the reaction solution. As a result, at the end of the process, the recovered mono-ethylene glycol (MEG) contains a significant proportion of impurities, preventing its further reuse for the production of high-quality, transparent plastic products.

[0006] An object of the present invention is to recover purified MEG from the depolymerization of polyesters or polyester-containing materials. According to EP1160228, ethylene glycols such as MEG produced from the reaction of ethylene oxide and water are separated from an aqueous mixture with organic acids, salts and unspecified UV light absorbers. This document neither discloses nor suggests whether the method disclosed in EP1160228 is suitable for recovering MEG from the depolymerization solution of polyesters such as PET. In particular, the depolymerization solution of polyesters containing at least one MEG unit contains components different from those of the aqueous solution as disclosed in EP1160228. The depolymerization solution may contain derivatives of other depolymerized polymer units, for example, impurities such as terephthalic acid or its salts when the polyester is PET, and / or heavy impurities.

[0007] By addressing this problem, the inventors have surprisingly demonstrated that by implementing a method involving specific steps in a certain order, it is possible to obtain high-purity MEG from a solution obtained from the depolymerization of at least one polyester having at least one MEG unit. The purity of the obtained MEG can be much higher than that obtained by conventional distillation purification and can be equivalent to the purity required by the existing specifications for petrochemical MEG.

[0008] Summary of the Invention The inventors have discovered that it is possible to construct a purification method that leads from the depolymerization of polyesters having at least one MEG unit to highly purified MEG suitable for repolymerization. More specifically, the inventors have developed a method that enables the recovery of high-purity MEG from the hydrolysis of polyesters having at least one MEG unit. In addition, the inventors have also discovered that this purification method can be implemented to purify MEG from solutions obtained from the chemical and biological depolymerization of at least one polyester having at least one MEG unit.

[0009] The merit of the inventors is that they have determined a specific series of steps for obtaining highly purified MEG from a solution containing ethylene glycol and salts as depolymerization products and for leading to the removal of any undesirable impurities in the final MEG. The method of the present invention enables the recovery of the MEG monomer that formed the original polymer of the polyester, so that the monomer can be reprocessed to synthesize new polymers of the same or different types.

[0010] In this regard, an object of the present invention is to provide a method for purifying MEG from a depolymerization solution of at least one polyester having at least one mono-ethylene glycol (MEG) unit, the method comprising the following steps: a) subjecting the depolymerization solution to at least one evaporation and condensation step to obtain a lower layer fraction and a condensed upper layer fraction; b) contacting the condensed upper layer fraction obtained in step (a) with a resin to obtain a solution; c) subjecting the solution obtained in step (b) to at least one distillation step to obtain a distillate; and d) recovering purified MEG from the distillate obtained in step (c).

[0011] In one embodiment, the polyester having at least one MEG unit is selected from the group consisting of polyethylene terephthalate (PET), polyethylene adipate (PEA), polyethylene-2,5-furanoate (PEF), and polyethylene naphthalate (PEN). In a particular embodiment, the polyester having at least one MEG unit is PET.

[0012] In one embodiment, the depolymerization by which the depolymerization solution to be subjected to the method of the present invention is obtained is either biological or chemical depolymerization. In a preferred embodiment, the biological or chemical depolymerization is hydrolysis, preferably hydrolysis under alkaline conditions (i.e., alkaline enzymatic depolymerization or alkaline chemical depolymerization, such as saponification), and even more preferably alkaline enzymatic depolymerization.

[0013] In a preferred embodiment, the depolymerization solution of at least one polyester having at least one MEG unit contains at least MEG, water, and heavy impurities, and may further contain trace amounts of acid and / or salts.

[0014] In one embodiment, the depolymerization solution of at least one polyester having at least one MEG unit is obtained from the reaction solution of the depolymerization of at least one polyester having at least one MEG unit, which contains dicarboxylate and MEG, and is subjected to one or more of the steps selected from the group consisting of filtration, decolorization, precipitation, and evaporation concentration.

[0015] Advantageously, step (a) includes a first evaporation condensation step, and further includes a step of subjecting the lower layer fraction obtained from the first evaporation condensation step to a second evaporation condensation step, where the condensed upper layer fraction obtained from the second evaporation condensation step is mixed with the condensed upper layer fraction obtained from the first evaporation condensation step, and the mixed condensed upper layer fraction is subjected to step (b).

[0016] In a preferred embodiment, the lower fraction obtained from the first evaporation-condensation step is filtered before being subjected to the second evaporation-condensation step.

[0017] In a preferred embodiment, step (b) is carried out by contacting the condensed upper fraction obtained in step (a) with an ion exchange resin, preferably a strong anion exchange resin.

[0018] In a preferred embodiment, step (c) consists of two distillation steps.

[0019] In a particular embodiment, the depolymerization solution is obtained from the enzymatic depolymerization of PET, wherein the pH of the reaction medium is adjusted between 6.5 and 9 by adding a base into the reaction medium. The TA salt generated from the depolymerization is removed from the solution by precipitation and filtration as described in WO 2020 / 094661 to obtain a reaction solution for use in the method of the present invention.

[0020] The object of the present invention is to provide a method for purifying MEG from a depolymerization solution of at least one polyester having at least one MEG unit, the method comprising or consisting of the following steps: a. subjecting the depolymerization solution to at least one evaporation-condensation step, preferably two evaporation-condensation steps both carried out in a thin-film evaporator, to obtain a mixture of a lower fraction and a condensed upper fraction; b. contacting the condensed upper fraction obtained in step (a) with a strong anion exchange resin to obtain a solution; c. subjecting the solution obtained in step (b) to double distillation; and d. recovering purified MEG from the distillate obtained in step (c).

[0021] Also, the object of the present invention is to provide a method for recycling a polymer-containing material such as a plastic product containing at least one polyester having at least one MEG unit, the method comprising the following steps: a.1) Subjecting a polyester having at least one MEG unit to a depolymerization step to obtain a reaction solution containing a dicarboxylate, MEG, and a solid component; b.1) Subjecting the reaction solution obtained in step (a.1) to filtration to remove the solid component and obtain a filtrate; c.1) Purifying the filtrate obtained in step (b.1) to obtain a purified filtrate; d.1) Precipitating a dicarboxylic acid by acidifying the purified filtrate obtained in step (c.1) to obtain a slurry; e.1) Subjecting the slurry obtained in step (d.1) to filtration to remove the precipitated dicarboxylic acid and obtain a filtrate; f.1) Subjecting the filtrate obtained in step (e.1) to at least one evaporation concentration step to obtain a solution in which MEG is concentrated; g.1) Purifying the MEG in the concentrated solution obtained in step (f.1) by the method according to the present invention to obtain purified MEG.

[0022] Advantageously, in step (a.1), the depolymerization is hydrolysis under alkaline conditions, preferably alkaline enzymatic depolymerization. Advantageously, in step (c.1), the purification of the filtrate obtained in step (b.1) is carried out through one or several steps selected from ultrafiltration, adsorption on activated carbon, feeding to an ion exchange resin, and chromatography.

[0023] In one embodiment, the polymer-containing material containing at least one polyester having at least one MEG unit is a plastic product containing at least one polyester having at least one MEG unit. In a specific embodiment, when the polyester having at least one MEG unit is PET, the dicarboxylic acid is terephthalic acid (TA), and the dicarboxylate is terephthalate.

[0024] Furthermore, an object of the present invention is to use the purified MEG obtained by the method according to the present invention for producing a polyester containing at least one MEG unit.

[0025] These and other objects and embodiments of the present invention will become more apparent after a detailed description of the invention, including its preferred embodiments given in the general terms.

[0026] Detailed Description of the Invention The present invention relates to a method for purifying MEG from a solution obtained from the depolymerization of at least one polyester having at least one mono-ethylene glycol (MEG) unit, enabling the recovery of the MEG monomer that formed the original polyester so that the monomer can be reprocessed to synthesize a new polyester.

[0027] The present invention particularly enables the removal of some or all, preferably all, of the remaining dicarboxylate salts (such as TA salt when the polyester is PET) and other inorganic impurities, as well as by-products such as di-ethylene glycol (DEG) and tri-ethylene glycol (TEG) present in the solution obtained from the depolymerization method.

[0028] The present invention also relates to a recycling method for recycling polymer-containing materials such as plastic products containing at least one polyester having at least one MEG unit for generating and recovering TA salt together with the purified MEG monomer.

[0029] Definitions In the context of the present invention, "polymer-containing material" or "polymer-containing product" refers to a product, such as a plastic product, that contains at least one polymer in crystalline, semi-crystalline or wholly amorphous form. In certain embodiments, the polymer-containing material is any article, such as a plastic sheet, tube, rod, profile, mold, film, bulk block, fiber, etc., made from at least one plastic material containing at least one polyester having at least one MEG unit and optionally other substances or additives such as plasticizers, minerals or organic fillers. In another particular embodiment, the polymer-containing material refers to a plastic compound or plastic formulation in molten or solid state suitable for manufacturing plastic products. In another particular embodiment, the polymer-containing material refers to a fiber product, fabric or fiber containing at least one polymer. In another particular embodiment, the polymer-containing material refers to plastic waste or fiber waste containing at least one polymer. In particular, the polymer-containing material is a plastic product.

[0030] Within the scope of the context of the present invention, the terms "plastic commodity" or "plastic product" are used to refer to any article or product containing at least one polymer, such as plastic sheets, tubes, rods, profiles, molds, bulk blocks, fibers, etc. Preferably, plastic commodities are manufactured products, such as rigid or soft packaging (bottles, trays, cups, etc.), agricultural films, bags and sacks, disposable articles or the like, carpet scraps, fabrics, fiber products, etc. Plastic commodities may contain additional substances or additives, such as plasticizers, minerals, organic fillers or dyes. In the context of the present invention, plastic commodities may contain mixtures of semi-crystalline and / or amorphous polymers and / or additives.

[0031] "Polymer" refers to a chemical compound or mixture of compounds composed of multiple repeating units (i.e., "monomers") whose structures are linked by covalent chemical bonds. Within the scope of the context of the present invention, the term "polymer" refers to such chemical compounds used in the composition of plastic products.

[0032] The "recycling method" related to plastic products refers to a method of decomposing at least one polyester of the plastic product to produce at least one type of monomer and / or oligomer and extracting them for reuse. Optionally, the monomers and / or oligomers are suitable for further repolymerization. In the context of the present invention, the plastic product contains at least one polyester having at least one MEG unit, is subjected to depolymerization, and produces at least MEG monomers.

[0033] The term "polyester" refers to a polymer containing an ester functional group in its main chain. The ester functional group is characterized by a carbon bond to three other atoms: a single bond to carbon, a double bond to oxygen, and a single bond to oxygen. The singly bonded oxygen is bonded to another carbon. Depending on the composition of their main chains, polyesters can be aliphatic, aromatic or semi-aromatic. Polyesters can be homopolymers or copolymers.

[0034] The term "polyester having at least one MEG unit" refers to a polyester formed from MEG and a dicarboxylic acid monomer. Examples of polyesters having at least one MEG unit include polyethylene terephthalate (PET), polyethylene adipate, polyethylene - 2,5 - furanoate, and polyethylene naphthalate. Polyethylene terephthalate is a semi - aromatic copolymer composed of two monomers: terephthalic acid and ethylene glycol. Polyethylene adipate is an aliphatic copolymer composed of adipic acid and ethylene glycol monomers. Polyethylene - 2,5 - furanoate is a semi - aromatic copolymer composed of 2,5 - furandicarboxylic acid and ethylene glycol monomers. Polyethylene naphthalate is a semi - aromatic copolymer composed of naphthalene - 2,6 - dicarboxylic acid and ethylene glycol monomers.

[0035] As used in this application, the terms "solubilized" or "in solubilized form" refer to a compound that is dissolved in a liquid, as distinct from a solid form that is not dissolved.

[0036] The term "depolymerization" in relation to a solution obtained from the depolymerization of at least one polyester having at least one MEG unit refers to a process by which a polyester having at least one MEG unit is depolymerized and / or decomposed into smaller molecules, such as monomers and / or oligomers and / or any degradation products. Depolymerization methods include chemical depolymerization methods and biological depolymerization methods.

[0037] "Solution obtained from the depolymerization of at least one polyester having at least one MEG unit", or "Depolymerization solution of at least one polyester having at least one MEG unit", or "Solution of the depolymerization of at least one polyester having at least one MEG unit", or even the expression "depolymerization solution" refers to a solution that has occurred or been obtained directly at the end of the depolymerization step of the polyester, or alternatively, a solution that has occurred or been obtained after one or several treatment steps of a solution that has occurred or been obtained directly at the end of the depolymerization step of the polyester. The depolymerization solution according to the present invention contains components and / or impurities specific to the depolymerization method and is thus different from any MEG-containing solution obtained by a method different from depolymerization. The solution contains MEG and other decomposition products. Among the decomposition products, examples include other monomers, oligomers, and / or their salts. The treatment step may be carried out to remove some of the decomposition products.

[0038] According to the present invention, "oligomer" refers to a molecule containing from 2 to about 20 monomer units. As examples, oligomers that can be extracted from PET include mono-2-hydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl) terephthalate (BHET), 1-(2-hydroxyethyl) 4-methyl terephthalate (HEMT), dimethyl terephthalate (DMT), di-ethylene-glycol (DEG) and / or tri-ethylene-glycol (TEG).

[0039] The term "salt", in the case of acidic salts, refers to any compound formed when the hydrogen ions of an acid are partially or completely replaced by cations such as sodium, potassium, ammonium or metal ions.

[0040] The term "dicarboxylic acid" refers to a compound containing two carboxyl functional groups -COOH. Dicarboxylic acids are represented by the formula HO2C-R-CO2H, where R can be aliphatic and / or aromatic, preferably aromatic. Examples include terephthalic acid, isophthalic acid, adipic acid, 2,5-furandicarboxylic acid, and naphthalene 2,6-dicarboxylic acid, which are dicarboxylic acids. Dicarboxylic acids usually result from units other than MEG in polyesters. Dicarboxylic acids preferably have a molecular weight of 100 g / mol or more. In certain embodiments, the dicarboxylic acid is different from oxalic acid.

[0041] "Dicarboxylate" is formed when the replaceable hydrogen ions in a dicarboxylic acid are partially or completely replaced by cations such as sodium, potassium, ammonium, or metal ions. "TA salt" or "terephthalate" is included in this definition. In the context of the present invention, TA salts can include disodium terephthalate C8H4Na2O4, dipotassium terephthalate C8H4K2O4, diammonium terephthalate C8H 12 N2O4, monosodium terephthalate C8H5NaO4, monopotassium terephthalate C8H5KO4, and / or monoammonium terephthalate C8H 10 NO4.

[0042] The term "mono-ethylene glycol" or "MEG" refers to the molecule represented by the formula C2H6O2 (HO-CH2-CH2-OH), which is recovered at the end of the purification process according to the present invention.

[0043] The term "purification method", when referring to a compound, refers to a method by which the purity of said compound is increased. As an example, the purity of the compound before the purification method may be lower than 70% by weight, lower than 50% by weight, or even lower than 30% by weight, relative to the total weight of the sample containing the compound to be purified. As an example, the purity of the compound after the purification method may be higher than 80% by weight, preferably higher than 90% by weight, more preferably higher than 95% by weight, and even more preferably higher than 99% by weight, relative to the total weight of the sample containing the purified compound.

[0044] "Heating temperature", as used in the present invention, corresponds to the temperature of the heating medium used to transfer heat from a heat source (such as steam), either directly or through a suitable heating device, to the process medium used in the subsequent process. The terms "process temperature" or "bottom temperature" correspond to the temperature of the lower fraction inside the process medium (i.e., a solution obtained from the depolymerization of at least one polyester having at least one monoethylene glycol (MEG) unit or a solution to be distilled). Due to heat conduction, the heating temperature of the heating medium is generally higher than the process temperature inside the process medium. Further, when measuring the temperature, the allowable error can be in the range of + / -5°C, + / -4°C, + / -3°C, + / -2°C, or + / -1°C.

[0045] "Ambient temperature" or "room temperature" means a temperature between 10°C and 30°C, particularly between 20°C and 25°C.

[0046] The expression "contained in X to Y" includes the boundaries, unless otherwise specified. This expression means that the target range includes the values of X and Y and all values between X and Y.

[0047] Method for the purification of MEG according to the present invention The object of the present invention is to provide a method for purifying MEG from a depolymerization solution of at least one polyester having at least one monoethylene glycol (MEG) unit, the method comprising the following steps: a) subjecting the depolymerization solution to at least one evaporation condensation step to obtain a lower layer fraction and a condensed upper layer fraction; b) contacting the condensed upper layer fraction obtained in step (a) with a resin to obtain a solution; and c) subjecting the solution obtained in step (b) to at least one distillation step to obtain a distillate; and d) recovering purified MEG from the distillate obtained in step (c).

[0048] This method can provide highly purified MEG from a solution obtained from the depolymerization of at least one polyester having at least one MEG unit.

[0049] In fact, the inventors have surprisingly discovered that the purity of MEG recovered from the solution obtained from the depolymerization of polyester has been significantly improved to near the purity of petrochemical-derived MEG thanks to the method of the present invention. More specifically, this purification method enables the monomers of the recovered MEG to be reused suitable for repolymerization into the polyester chain.

[0050] In addition, the obtained MEG exhibits a low color number according to the APHA scale, in particular, a low APHA index and / or a low APHA boiling value. The APHA boiling value can be obtained as the APHA index according to ASTM-5386 after heating the sample at 198 °C for 4 hours. The APHA index of the obtained MEG is preferably lower than 5, and / or the APHA boiling value is preferably lower than 200, more preferably lower than 160, even more preferably lower than 50, particularly lower than 20.

[0051] Step (a) of evaporation condensation A method for purifying MEG comprises step (a) of subjecting a solution obtained from the depolymerization of at least one polyester having at least one MEG unit to at least one evaporation-condensation step to obtain a lower fraction and a condensed upper fraction. According to the present invention, the evaporation-condensation step means an evaporation step followed by a condensation step. In certain embodiments, the evaporation-condensation of step (a) consists of one evaporation step and one condensation step.

[0052] The condensed upper fraction corresponds to the fraction that evaporates during the evaporation step, which is recovered at the top of the evaporator and condensed during the condensation step. The condensed upper fraction conventionally contains MEG as well as other volatile molecules (such as water, DEG, and TEG).

[0053] The lower fraction corresponds to the fraction that remains at the bottom of the evaporator during the evaporation-condensation step.

[0054] Advantageously, the process enables the removal of salts from the condensed upper fraction. More specifically, the process enables the recovery of heavy impurities, mainly salts and solid impurities, at the bottom of the evaporator. In certain embodiments, when the polyester subjected to depolymerization is PET, the depolymerization method is alkaline hydrolysis, preferably enzymatic or chemical alkaline hydrolysis using NaOH. In such cases, the process enables the recovery of mainly TA salts and other salts (such as Na2SO4) at the bottom of the evaporator.

[0055] The evaporation step enables the separation and removal of one or more dissolved salts contained in the solution obtained from the depolymerization of at least one polyester having at least one MEG unit. This step is carried out by heating the solution under vacuum until the desired evaporation rate is reached. The evaporation rate is the ratio between the evaporated amount and the supplied amount. Those skilled in the art know how to adapt the desired evaporation rate so that the bottom of the evaporator is not clogged with precipitated salts. The salts remain in the lower fraction, and MEG as well as other volatile molecules (such as water, DEG, and TEG) evaporate. Their vapor enters the condensation step and an upper fraction is produced.

[0056] The separated salts can be selected from the group consisting of, for example, dicarboxylate salts such as terephthalate salts, and salts of other decomposition products of the polyester. Among the decomposition products of the polyester, examples of salts that can be separated in the evaporation condensation step (a) include salts of methyl-2-hydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl) terephthalate (BHET), and isophthalic acid (IPA).

[0057] The evaporation of the evaporation concentration in step (a) can be carried out in any suitable evaporator, for example, a thin-film evaporator, a batch evaporator, a forced circulation evaporator, or a flash evaporator, preferably in a thin-film evaporator. Thereafter, the condensation of the volatilized upper fraction can be carried out by passing the upper fraction through a heat exchanger, preferably a tube-type heat exchanger or a plate-type heat exchanger containing a cooling medium at a temperature below 50°C. Preferably, the heat exchanger is a condensation unit, more preferably a water-cooled condensation unit.

[0058] Step (a) can include or consist of one or several evaporation condensation steps, depending on the content of the solution subjected to step (a), its volume, and / or the type of evaporator used.

[0059] Those skilled in the art can adjust evaporation conditions such as temperature, pressure, and / or evaporation rate, especially depending on the sample to be evaporated and the evaporator used. As an example, when evaporation is carried out in a thin-film evaporator, the evaporation rate is preferably limited to 90% by controlling the heating or method temperature during evaporation so that no dry area is formed on the exchanger surface.

[0060] According to the present invention, the evaporation condensation step is operated by controlling the method pressure (inside the method medium) simultaneously with either the heating temperature or the method temperature.

[0061] When the temperature of the heating medium is controlled, the heating temperature during evaporation is less than 200 °C, less than 195 °C, less than 193 °C, less than 190 °C, less than 185 °C, less than 180 °C, less than 170 °C, preferably less than 195 °C, and the pressure is 15 mbar abs or more, for example 20 mbar abs or more, for example 30 mbar abs or more, for example 40 mbar abs or more, for example 50 mbar abs or more, for example 60 mbar abs or more, for example 70 mbar abs or more, for example 80 mbar abs or more, for example 85 mbar abs or more, for example 90 mbar abs or more, for example 95 mbar abs or more, for example 98 mbar abs or more, for example 99 mbar abs or more, for example 100 mbar abs or more. The pressure may be 1000 mbar abs or less, for example 500 mbar abs or less, for example 300 mbar abs or less, for example 200 mbar abs or less. In some embodiments, the heating temperature during evaporation is less than 200 °C, less than 195 °C, less than 193 °C, less than 190 °C, less than 185 °C, less than 180 °C, less than 170 °C, preferably less than 195 °C, and the pressure is included in 50 mbar abs to 1000 mbar abs, preferably 50 mbar abs to 500 mbar abs, more preferably 50 to 300 mbar abs, even more preferably 50 to 200 mbar abs.In some embodiments, the evaporation in step (a) is operated at a heating temperature included in 80°C to 200°C, preferably 100°C to 195°C, more preferably 120°C to 193°C, even more preferably 140°C to 193°C, and the pressure is 15 mbar abs or more, for example 20 mbar abs or more, for example 30 mbar abs or more, for example 40 mbar abs or more, for example 50 mbar abs or more, for example 60 mbar abs or more, for example 70 mbar abs or more, for example 80 mbar abs or more, for example 85 mbar abs or more, for example 90 mbar abs or more, for example 95 mbar abs or more, for example 98 mbar abs or more, for example 99 mbar abs or more, for example 100 mbar abs or more. The pressure may be 1000 mbar abs or less, for example 500 mbar abs or less, for example 300 mbar abs or less, for example 200 mbar abs or less. In some embodiments, the evaporation in step (a) is operated at a heating temperature included in 80°C to 200°C, preferably 100°C to 195°C, more preferably 120°C to 193°C, even more preferably 140°C to 193°C, and the pressure is included in 50 mbar abs to 1000 mbar abs, preferably included in 50 mbar abs to 500 mbar abs, more preferably included in 5 to 300 mbar abs, even more preferably included in 50 to 200 mbar abs.

[0062] Alternatively, when the temperature inside the process medium is controlled, the process temperature during evaporation is less than 195°C, less than 190°C, less than 180°C, preferably less than 170°C, more preferably included in the range of 80°C to 200°C, more preferably 100°C to 175°C, and the pressure is 15 mbar abs or more, for example 20 mbar abs or more, for example 30 mbar abs or more, for example 40 mbar abs or more, for example 50 mbar abs or more, for example 60 mbar abs or more, for example 70 mbar abs or more, for example 80 mbar abs or more, for example 85 mbar abs or more, for example 90 mbar abs or more, for example 95 mbar abs or more, for example 98 mbar abs or more, for example 99 mbar abs or more, for example 100 mbar abs or more. The pressure may be 1000 mbar abs or less, for example 500 mbar abs or less, for example 300 mbar abs or less, for example 200 mbar abs or less, for example 100 mbar abs or less. In certain embodiments, the process temperature during evaporation is less than 195°C, less than 190°C, less than 180°C, preferably less than 170°C, more preferably included in the range of 80°C to 200°C, more preferably 100°C to 175°C, and the pressure is included in the range of 50 mbar abs to 1000 mbar abs, preferably 50 mbar abs to 500 mbar abs, more preferably 50 to 300 mbar abs, even more preferably 50 to 200 mbar abs.

[0063] In certain embodiments, the evaporation in the first and / or second evaporative condensation step of step (a) is carried out under vacuum conditions, preferably at a pressure of 15 mbar abs or more, preferably in the range of 15 to 500 mbar abs, for example 50 to 500 mbar abs, more preferably 100 mbar abs.

[0064] In some embodiments, step (a) includes 1, 2, 3, 4 or 5 evaporation condensation steps. Preferably, step (a) includes 1, 2, 3 or 4 evaporation condensation steps, more preferably 2 evaporation condensation steps.

[0065] In some embodiments, step (a) comprises or consists of 1 evaporation condensation step. In some embodiments, step (a) comprises or consists of 1 evaporation condensation step carried out in a forced circulation evaporator.

[0066] If step (a) includes more than 1 evaporation condensation step, each evaporation condensation step is carried out on the lower fraction of the previous evaporation condensation step. The condensed upper fractions obtained after each condensation step are preferably mixed before being fed to step (b).

[0067] If step (a) includes more than 1 evaporation condensation step, the last evaporation condensation step is preferably carried out in a thin-film evaporator. In some embodiments, the first evaporation condensation step is carried out in a forced circulation evaporator and the second one is carried out in a thin-film evaporator. In some embodiments, the first and / or second evaporation condensation steps are carried out in a batch evaporator.

[0068] In another embodiment, in addition to the first evaporation condensation step of step (a), step (a) includes 1 additional evaporation condensation step of feeding the lower fraction obtained from the first evaporation condensation step to a second evaporation condensation step, and the condensed upper fractions obtained from the first and second evaporation condensation steps are mixed before being fed to step (b). This additional evaporation condensation step increases the yield of recovered MEG.

[0069] In certain embodiments, the lower fraction obtained from the first evaporation condensation step is filtered before being fed to the second evaporation condensation step. In particular, the evaporation of the second evaporation condensation step is carried out in a thin-film evaporator.

[0070] In one embodiment, the first and second evaporation condensation steps are carried out in a thin-film evaporator. In particular, the temperature of the additional evaporation is higher than the temperature of the first evaporation, and the two evaporations are carried out at the same pressure.

[0071] In a particular embodiment, step (a) consists of two evaporation condensation steps in which the lower layer fraction obtained from the first evaporation condensation step is fed to the second evaporation condensation step, and the condensed upper layer fractions obtained from the first and second evaporation condensation steps are mixed before being fed to step (b).

[0072] In particular, the evaporation in the first evaporation condensation step is carried out at a process temperature of 90 °C to 180 °C, 100 °C to 170 °C, 120 °C to 170 °C, 90 °C to 150 °C, 100 °C to 155 °C, 110 °C to 140 °C, 110 °C to 125 °C, preferably 115 °C to 120 °C, at a pressure of 15 mbar abs or more, for example, included in 15 to 500 mbar abs, for example, included in 50 to 500 mbar abs, 50 to 300 mbar abs, preferably 100 mbar abs, and the evaporation in the second evaporation condensation step is carried out at a process temperature of 120 °C to 150 °C, 120 °C to 155 °C, 130 °C to 155 °C, 130 °C to 150 °C, 135 °C to 150 °C, 135 °C to 145 °C, at a pressure of 15 mbar abs or more, for example, included in 15 to 500 mbar abs, for example, included in 50 to 500 mbar abs, preferably 100 mbar abs.

[0073] In a particular embodiment, step (a) consists of the following two evaporation condensation steps: (1) The evaporation in the first evaporation condensation step is operated at a pressure included in 100 °C to 180 °C, for example 110 °C to 135 °C, preferably 110 °C to 125 °C, more preferably 118 °C, at a process temperature, at a pressure of 15 mbar abs or more, for example, included in 15 to 500 mbar abs, preferably included in 50 to 500 mbar abs, more preferably included in 50 to 120 mbar abs, for example 80 to 120 mbar abs. (2) The evaporation of the second evaporation condensation is carried out at a method temperature of 130°C to 150°C, preferably 144°C, at a pressure of 15 mbar abs or more, for example, 15 to 500 mbar abs, preferably 50 to 500 mbar abs, more preferably 50 to 120 mbar abs, for example 80 to 120 mbar abs.

[0074] In a preferred embodiment, the evaporation step is carried out at 100 mbar abs. In a particular embodiment, both evaporations are carried out at the same pressure, preferably 100 mbar abs.

[0075] In particular, the evaporation of the first evaporation condensation step is carried out at a heating temperature of 150°C to 180°C, 155°C to 170°C, 160°C to 170°C, at a pressure of 5 mbar abs or more, for example, 5 to 500 mbar abs, for example, 50 to 500 mbar abs, 50 to 300 mbar abs, preferably 100 mbar abs; the evaporation of the second evaporation condensation step is carried out at a heating temperature of 150°C to 200°C, 155°C to 195°C, preferably 165°C to 195°C, at a pressure of 5 mbar abs or more, for example, 5 to 500 mbar abs, for example, 50 to 500 mbar abs, preferably 100 mbar abs. Preferably, the two evaporation steps are carried out at the same 100 mbar abs.

[0076] In a particular embodiment, step (a) consists of the following two evaporation condensation steps: (1) The evaporation of the first evaporation condensation step is carried out at a heating temperature of 155 to 170°C, preferably 160°C to 170°C, at a pressure of 5 mbar abs or more, for example, 5 to 500 mbar abs, for example, 50 to 500 mbar abs, preferably 50 to 120 mbar abs, for example 80 to 120 mbar abs. (2) The evaporation of the second evaporation condensation is carried out at a heating temperature included in the range of 155°C to 195°C, preferably 165°C to 195°C, and at a pressure included in 5 mbar abs or more, for example, 5 to 500 mbar abs, for example, 50 to 500 mbar abs, preferably 50 to 120 mbar abs, for example, 80 to 120 mbar abs.

[0077] Advantageously, the condensed upper layer fraction recovered from step (a) contains at least 60% MEG, preferably at least 70% MEG, more preferably at least 80% MEG.

[0078] Step (b) of bringing the condensed upper layer fraction obtained in step (a) into contact with a resin In this step, the condensed upper layer fraction or the mixed condensed upper layer fraction of the previous step (a) is brought into contact with the resin, preferably passed through the resin, to obtain a solution.

[0079] The inventors have demonstrated that by contacting the upper layer fraction obtained in step (a) with a resin, a solution containing MEG with a lower acidity can be provided even if the solution subjected to step (a) contains an acidic compound and / or a trace amount of acid. In a preferred embodiment, the condensed upper layer fraction of step (a) is contacted with an ion exchange resin, preferably a strong anion exchange resin, preferably by passing it through the resin. Those skilled in the art can select an ion exchange resin suitable for implementation and adapt the flow rate according to the content of the upper layer fraction obtained in step (a). Among anion exchange resins, mention can be made of anion exchange resins sold under the trade name Purolite® containing a quaternary ammonium group, for example, resins such as Purolite® A500MBPlusOH or Purolite® A860. Preferably, the ion exchange resin is the resin called Purolite® A860. The anion exchange resin can be, for example, polyacrylic acid crosslinked with a divinylbenzene anion exchange resin, or polystyrene crosslinked with a divinylbenzene anion exchange resin. The use of an anion exchange resin enables higher purity and improves the UV transmittance of the purified MEG.

[0080] According to the present invention, this step is preferably carried out in continuous mode at room temperature.

[0081] Step (c) of distillation According to the present invention, the solution obtained in step (b) is subjected to at least one distillation step (c) to obtain a distillate. Step (c) aims to separate the monomer of MEG from oligomers such as DEG and TEG present in the solution. Furthermore, this step makes it possible to reduce the water content of the solution.

[0082] Similar to the evaporation condensation step, this step is operated by controlling the process pressure (inside the process medium) simultaneously with either the heating temperature or the process temperature.

[0083] Step (c) may include or consist of one or several distillation steps. In some embodiments, step (c) includes 1, 2, 3 or 4 distillation steps.

[0084] One skilled in the art will know how to adapt the temperature and / or pressure to perform distillation. In particular, depending on the number of distillation steps to be carried out in step (c), one skilled in the art will know how to adapt the temperature and pressure of each distillation step such that the distillate contains MEG.

[0085] When the temperature of the heating medium is controlled, the heating temperature during the distillation process is less than 250°C, less than 220°C, less than 200°C, preferably less than 190°C, and the pressure is 15 mbar abs or more, for example 20 mbar abs or more, for example 22 mbar abs or more, for example 25 mbar abs or more, for example 27 mbar abs or more, for example 40 mbar abs or more, for example 50 mbar abs or more, for example 80 mbar abs or more, for example 90 mbar abs or more, for example 100 mbar abs or more, for example 120 mbar abs or more, for example 150 mbar abs or more, for example 170 mbar abs or more, for example 180 mbar abs or more, for example 195 mbar abs or more, for example 200 mbar abs or more, for example 205 mbar abs. The pressure may be 1000 mbar abs or less, for example 500 mbar abs or less, for example 300 mbar abs or less, for example 220 mbar abs or less, for example 210 mbar abs or less, for example 205 mbar abs or less, for example 200 mbar abs or less. Preferably, the pressure is 15 - 300 mbar abs, for example, 20 - 250 mbar abs. In some embodiments, the heating temperature during the distillation process is less than 250°C, less than 220°C, less than 200°C, preferably less than 190°C, and the pressure is included in 50 - 300 mbar abs, preferably 100 - 250 mbar abs. In some embodiments, the distillation process is operated at a heating temperature included in 140°C - 250°C, 150°C - 250°C, 155°C - 220°C, 160°C - 250°C, 170°C - 250°C, 160°C - 220°C, preferably 170°C - 210°C.

[0086] Alternatively, when the temperature inside the method medium is controlled, the method temperature (bottom temperature) is included in 110°C to 200°C, 125°C to 180°C, 130°C to 180°C, 135°C to 175°C, and the pressure is 15 mbar abs or more, for example 20 mbar abs or more, for example 22 mbar abs or more, for example 25 mbar abs or more, for example 27 mbar abs or more, for example 40 mbar abs or more, for example 50 mbar abs or more, for example 80 mbar abs or more, for example 90 mbar abs or more, for example 100 mbar abs or more, for example 120 mbar abs or more, for example 150 mbar abs or more, for example 170 mbar abs or more, for example 180 mbar abs or more, for example 195 mbar abs or more, for example 200 mbar abs or more, for example 205 mbar abs. The pressure may be 1000 mbar abs or less, for example 500 mbar abs or less, for example 300 mbar abs or less, for example 220 mbar abs or less, for example 210 mbar abs or less, for example 205 mbar abs or less, for example 200 mbar abs or less. Preferably, the pressure is 15 to 300 mbar abs, for example, 20 to 250 mbar abs. Preferably, the pressure is 15 to 300 mbar abs. In some embodiments, the method temperature (bottom temperature) is included in 110°C to 200°C, 125°C to 180°C, 130°C to 180°C, 135°C to 175°C, and the pressure is included in 50 to 300 mbar abs, preferably 100 to 250 mbar abs.

[0087] In one embodiment, step (c) consists of one distillation step. In a particular embodiment, step (c) consists of one distillation step in which MEG is directly recovered via side stream withdrawal. Thus, when the temperature inside the process medium is controlled, the distillation is carried out at a process temperature (bottom temperature) included in 120°C to 190°C, preferably 130°C to 180°C, more preferably 140°C to 180°C, at a pressure of 15 to 300 mbar abs, for example 50 to 300 mbar abs, preferably 90 to 210 mbar abs, more preferably 100 mbar abs. Those skilled in the art know how to adapt the side stream withdrawal to recover MEG.

[0088] In another embodiment, the solution obtained in step (b) is subjected to at least two distillation steps each. In a particular embodiment, step (c) consists of two distillation steps, preferably where the pressure of the second distillation is lower than the pressure of the first distillation.

[0089] As an example, when two distillation steps are carried out: (1) The first distillation is carried out at a temperature (bottom temperature) included in 120°C to 170°C, preferably 130°C to 160°C, at a pressure of 100 to 300 mbar abs, preferably 140 to 230 mbar abs; (2) The second distillation is carried out at a temperature (bottom temperature) included in 130°C to 220°C, preferably 130°C to 180°C, at a pressure of 50 to 300 mbar abs, preferably 90 to 210 mbar abs.

[0090] According to this particular embodiment of the present invention: The first distillation enables the removal of water and light components in the upper fraction, while MEG, DEG and TEG remain in the lower fraction, The second distillation carried out on the lower fraction obtained from the first distillation enables the separation of MEG in the upper fraction (distillate), while heavier components such as DEG and TEG remain in the lower fraction. In such a conventional distillation, the distillate containing MEG is recovered at the top of the column.

[0091] In a preferred embodiment, step (c) comprises or consists of two distillation steps, where the first distillation is carried out under the same conditions as shown above, and the second distillation is a distillation with two sections, where MEG is recovered at the upper part of the column by side stream withdrawal. "Distillation with two sections" means a special arrangement of the distillation column by adding an auxiliary upper section onto the second distillation column, where the distillate containing MEG is recovered at the upper part of the column rather than at the top of the column. In this case, the last light species, if present, is preferably pushed out at the top of the column.

[0092] In such an embodiment, the first distillation enables the removal of water and light components in the upper layer fraction, while MEG, DEG and TEG remain in the lower layer fraction, and the second distillation leaves DEG, TEG and heavy components at the bottom, where MEG is extracted and recovered by side stream withdrawal located in the first upper part of the column, and the last light species, if present, is pushed out at the top of the column.

[0093] Generally, when the second distillation is a distillation with two sections, it is carried out at a process temperature included in 130 °C to 200 °C, preferably 150 °C to 180 °C, and at a pressure of 15 to 100 mbar abs, preferably 20 to 90 mbar abs.

[0094] As an example: (1) The first distillation is carried out at a process temperature included in 120 °C to 195 °C, preferably 150 °C to 185 °C, and at a pressure of 15 to 300 mbar abs, preferably 100 to 230 mbar abs; (2) The second distillation, which is a distillation with two sections, is carried out at a process temperature included in 130 °C to 200 °C, preferably 150 °C to 180 °C, and at a pressure of 15 to 100 mbar abs, preferably 20 to 90 mbar abs.

[0095] In another embodiment, step (c) comprises or consists of three distillation steps, where the first and third distillations are carried out under the same conditions as shown above, and the second distillation is a distillation with two sections as defined above.

[0096] In one embodiment, the distillation step of step (c) is carried out under vacuum conditions, preferably at a pressure of 50 - 500 mbar abs.

[0097] The distillate containing MEG may be recovered from the distillation column used to carry out step (c) by any suitable means. By way of example, the distillation may include a side stream withdrawal suitable for recovering MEG.

[0098] In a preferred embodiment, the purification method is carried out in the order of a) to d), and MEG is recovered after distillation.

[0099] Further step (c') of the process In one embodiment, the method of the present invention further includes step (c'), where the distillate obtained in step c) is subjected to one or more steps selected from the group consisting of distillation, hydrogenation, dehydration, and decolorization, preferably a distillation step and / or a decolorization step, before the recovery step (d), and where the decolorization step is preferably carried out by activated carbon adsorption.

[0100] This step (c') is optional and can be carried out on the distillate obtained in step (c) before carrying out the recovery step (d). This enables the improvement of the UV transmittance of the purified MEG.

[0101] According to the present invention, the distillate obtained in step c) may be further subjected to one or more steps selected from the group consisting of distillation, hydrogenation, dehydration, or decolorization, preferably a distillation step and / or a decolorization step.

[0102] In one embodiment, the distillate obtained in step c) may be further subjected to a decolorization step of passing the distillate through an adsorbent. The adsorbent may be any adsorbent known to those skilled in the art, for example, activated carbon, macroporous resin, preferably activated carbon. In particular, the step is preferably carried out at room temperature. Preferably, the method further comprises a step in which the decolorization step is carried out by activated carbon adsorption.

[0103] In another embodiment, the distillate obtained in step c) may be further subjected to a distillation step. The distillation is carried out under the same conditions (heating temperature or method temperature - pressure) as those shown in the distillation of step (c).

[0104] In a particular embodiment, the distillate obtained in step c) may be further subjected to a distillation followed by a decolorization step.

[0105] According to the present invention, an object of the present invention is to provide a method for purifying MEG from a solution obtained from the depolymerization of at least one MEG unit, the method comprising or consisting of the following steps: a. subjecting the solution to two evaporation condensation steps (preferably, the second evaporation condensation step is carried out in a thin-film evaporator, more preferably, the two evaporation condensation steps are carried out in a thin-film evaporator) to obtain a mixture of a lower layer fraction and a condensed upper layer fraction; b. contacting the condensed upper layer fraction obtained in step (a) with an anion exchange resin to obtain a solution; c. subjecting the solution obtained in step (b) to double distillation to obtain a distillate, preferably, the second distillation is a distillation involving two sections; and d. recovering purified MEG from the distillate obtained in step (c).

[0106] According to the present invention, further, an object of the present invention is to provide a method for purifying MEG from a solution obtained from the depolymerization of at least one MEG unit, the method comprising or consisting of the following steps: a. Subjecting the solution to two evaporation and condensation steps (preferably, the second evaporation and condensation step is carried out in a thin-film evaporator, and more preferably, both evaporation and condensation steps are carried out in a thin-film evaporator) to obtain a mixture of a lower fraction and a condensed upper fraction; b. Contacting the condensed upper fraction obtained in step (a) with an anion exchange resin to obtain a solution; c. Subjecting the solution obtained in step (b) to double distillation to obtain a distillate, preferably, the second distillation is a distillation involving two sections; c’. Optionally, subjecting the distillate obtained in step (c) to one or more further steps selected from the group consisting of distillation, hydrogenation, dehydration, or decolorization, preferably, a step of distillation and / or a step of decolorization to obtain a solution, and d. Recovering purified MEG from the solution obtained in step (c’) or step (c).

[0107] When the second distillation is a distillation involving two sections, step (c’) of the further step preferably does not exist. The step of distillation involving two sections helps to obtain the same MEG purity without the need for the further step of step (c’).

[0108] According to the present invention, the method can be continuously carried out from step a) to c), more preferably, from step a) to d) in a discontinuous mode, i.e., under batch conditions, or in a continuous mode. The continuous mode is preferred.

[0109] Step (d) of recovering MEG According to the present invention, recovering MEG means recovering the distillate obtained in step (c) containing purified MEG or the solution obtained in step (c’). In other words, purified MEG is contained in liquid form in the distillate or solution obtained at the end of step (c) or (c’). Alternatively, the recovery of MEG is continuously carried out by using side-stream withdrawal during the distillation step of step (c) or (c’).

[0110] The method for MEG purification according to the present invention enables the recovery of highly purified MEG. In certain embodiments, the obtained MEG has a purity of at least 95%, preferably at least 99%, more preferably at least 99.9%.

[0111] Solution obtained from depolymerization or depolymerization solution According to the present invention, a solution obtained from the depolymerization of at least one polyester containing at least one MEG unit refers to a solution obtained or produced from the chemical or biological depolymerization, preferably via hydrolysis, of at least one polyester containing at least one MEG unit.

[0112] Composition of the solution obtained from depolymerization (depolymerization solution) This solution may contain depolymerized and / or decomposed molecules, such as monomers and / or oligomers and / or any decomposition products and / or heavy impurities and / or trace acids and / or salts and / or water. More specifically, this solution may contain monomeric MEG, and / or dicarboxylates, such as terephthalates, isophthalic acid (IPA) salts and / or salts, and / or oligomers, such as DEG and TEG, and / or mono-2-hydroxyethyl terephthalate (MHET) and / or bis(2-hydroxyethyl) terephthalate (BHET), derivatives thereof including dimethyl terephthalate (DMT), and / or heavy impurities, and / or trace acids, and / or water. The content of the depolymerization solution depends on the depolymerization method, such as hydrolysis, glycolysis, methanolysis, etc.

[0113] In a preferred embodiment, the solution is a homogeneous solution from which any residual solids have been removed.

[0114] The term "heavy impurities" mainly refers to dissolved non-volatile impurities, such as heavy metals, antimony, copper, and depolymerizing agents, such as catalysts or enzymes.

[0115] "Trace acid" means the total acid content titrated with an aqueous base solution (KOH or NaOH) in a sample of ethylene glycol. The acidity is calculated in mg / kg units as acetic acid equivalent. The test method is described in ASTM E 2679, which is particularly useful for determining low levels of acidity. In the context of this invention, the concentration of trace acid is equivalent to a concentration of less than 2 g KOH / kg, preferably less than 1100 mg KOH / kg, more preferably less than 700 mg KOH / kg measured according to ASTM E 2679.

[0116] In one embodiment, a solution obtained from the depolymerization of at least one polyester containing at least one MEG unit comprises at least one monomer selected from the group consisting of MEG, dicarboxylic acids such as terephthalic acid (TPA) or isophthalic acid (IPA), at least one salt of such a monomer, and / or a salt such as Na2SO4, and / or an oligomer such as mono-2-hydroxyethyl terephthalate (MHET).

[0117] In certain embodiments, a solution obtained from the depolymerization of at least one polyester having at least one MEG unit comprises MEG, water, heavy impurities, and optionally further comprises trace acid and / or salts.

[0118] In certain embodiments, a solution obtained from the depolymerization of at least one polyester having at least one MEG unit comprises MEG, water, heavy impurities, and salts such as sodium sulfate salt, dicarboxylate salts, and / or trace acid.

[0119] In certain embodiments, the solution is obtained from the alkaline hydrolysis of at least one polyester containing at least one MEG unit and comprises MEG and / or heavy impurities and / or water and / or trace acid and / or soluble salts such as sodium sulfate salt, dicarboxylate salts.

[0120] In a preferred embodiment, the solution obtained from the depolymerization of at least one polyester containing at least one MEG unit is an aqueous concentrated solution of MEG as defined below.

[0121] In a particular embodiment, the solution obtained from the depolymerization of at least one polyester containing at least one MEG unit contains at least one MEG and heavy impurities.

[0122] In one embodiment, the solution obtained from the depolymerization of PET contains MEG, heavy impurities and terephthalate, and finally contains sodium sulfate salt and / or trace acid.

[0123] In a preferred embodiment, the solution obtained from the depolymerization of at least one polyester containing at least one MEG unit contains at least 400 g / kg of MEG, at least 500 g / kg, at least 600 g / kg, at least 700 g / kg of MEG, or at least 800 g / kg of MEG, based on the total weight of the solution. Preferably, the solution contains at least 600 g / kg of MEG, preferably 700 g / kg of MEG.

[0124] The salts that may be present in the solution can be one or more of the group consisting of sodium, potassium or ammonium salts or mixtures thereof. For example, the salts can be selected from the group consisting of Na2SO4, K2SO4, (NH4)2SO4, NaCl, KCl, NH4Cl, Na2PO4, K2PO4, (NH4)2PO4, NaNO3, KNO3, NH4NO3 or mixtures thereof, and / or dicarboxylates.

[0125] In one embodiment, the dicarboxylate is selected from the group consisting of terephthalate, adipate, 2,5-furandicarboxylate and naphthalene-2,6-dicarboxylate. Preferably, the dicarboxylate is the TA salt.

[0126] In certain embodiments, the solution contains at least 5 g / kg of salt, preferably at least 10 g / kg, more preferably 20 g / kg of salt, based on the total weight of the aqueous solution. In certain embodiments, the initial solution contains at most 80 g / kg of salt, preferably at most 50 g / kg, more preferably at most 30 g / kg of salt, based on the total weight of the aqueous solution. In particular, the initial solution contains 5 g / kg to 80 g / kg of salt, 10 g / kg to 80 g / kg of salt, 10 g / kg to 50 g / kg of salt.

[0127] Chemical or biological depolymerization step The depolymerization step from which the solution to be subjected to the purification method of the present invention is obtained targets at least one polyester having at least one MEG unit. In certain embodiments, the method of the present invention is carried out on a plastic product that is a polymer-containing material, preferably resulting from plastic waste collections and / or post-industrial waste and containing at least one polyester having at least one MEG unit. More specifically, the method of the present invention can be used to decompose household plastic waste including plastic bottles, plastic trays, plastic bags, plastic packaging, soft plastics and / or hard plastics, even if contaminated with food residues, detergents, etc. Alternatively, or additionally, the method of the present invention may be used to decompose used fibers, such as fibers derived from fabrics, textile products, tires and / or industrial waste. More specifically, the method of the present invention may be used with PET plastic waste and / or PET fiber waste.

[0128] In certain embodiments, the polyester having at least one MEG unit is selected from the group consisting of polyethylene terephthalate (PET), polyethylene adipate (PEA), polyethylene furanoate (PEF), and polyethylene naphthalate (PEN). In a preferred embodiment, the polyester having at least one MEG unit is PET.

[0129] In particular, the depolymerization step is either chemical depolymerization or biological depolymerization. In a preferred embodiment, the depolymerization that yields the solution to be subjected to the method of the present invention is hydrolysis, preferably hydrolysis under alkaline conditions, more preferably alkaline enzymatic depolymerization or alkaline chemical depolymerization, such as saponification, and even more preferably alkaline enzymatic depolymerization.

[0130] Within the context of the present invention, "hydrolysis" refers to the cleavage of an ester bond by OH ions in the presence of water, regardless of whether the reaction is biological depolymerization or chemical depolymerization. For example, the hydrolysis of PET produces terephthalic acid (TA) and ethylene glycol (MEG). In a preferred embodiment, hydrolysis is alkaline hydrolysis in which an alkali (or base) is used as a reactant for decomposing the polyester in an aqueous medium. Such an alkali can be selected from NaOH, KOH, NH4OH, or LiOH. By way of example, the alkaline hydrolysis of PET produces terephthalic acid (TA) salt and ethylene glycol (MEG).

[0131] In one embodiment, the depolymerization step comprises contacting at least one polyester having at least one MEG unit with a depolymerizing agent, i.e., a chemical and / or biological depolymerizing agent.

[0132] Advantageously, the depolymerization step involving the depolymerizing agent is carried out in a liquid medium, more advantageously in an aqueous medium, as the starting reaction medium.

[0133] In one embodiment, the depolymerization of the polyester having at least one MEG unit is chemical depolymerization, preferably hydrolysis. Preferably, the chemical depolymerization is alkaline chemical hydrolysis such as saponification.

[0134] Within the context of the present invention, the term "chemical depolymerization" refers to a process in which the depolymerization of at least one polyester having at least one MEG unit is carried out by contacting the polymer with a reactant, such as methanol or water, optionally in the presence of one or more chemical agents, such as a catalyst. These processes are known as methanolysis and chemical hydrolysis, respectively. Other processes include glycolysis, aminolysis, and ammonolysis. The methanolysis of PET produces dimethyl terephthalate (DMT) and mono-ethylene glycol (MEG).

[0135] In one embodiment, the chemical depolymerization is carried out by hydrolysis. As an example, the chemical alkaline hydrolysis of PET, also called saponification, produces terephthalate and ethylene glycol (MEG). During the saponification reaction, the polyester reacts with a strong base of an alkali metal, such as NaOH or KOH, in the presence of water.

[0136] In a particular embodiment, the depolymerization step comprises contacting at least one polyester having at least one MEG unit with a chemical agent in an alkaline medium as a starting reaction medium containing an alkali such as KOH, NaOH, NH4OH or LiOH.

[0137] In a particular embodiment, the depolymerizing agent is a chemical depolymerizing agent. In particular, the chemical agent is a metal catalyst, a stable and non-toxic hydrosilane (PMHS, TMDS), and commercially available B(C6F5)3 and [Ph3C + ,B(C6F5)4 -It is a catalyst selected from other catalysts such as a catalyst. In particular, the catalyst is selected from alkoxides, carbonates, acetates, hydroxides, alkali metal oxides, alkaline earth metals, calcium oxide, calcium hydroxide, calcium carbonate, sodium carbonate, iron oxide, zinc acetate, zeolites. In some embodiments, the catalyst used in the depolymerization method of the present invention comprises at least one of a germanium compound, a titanium compound, an antimony compound, a zinc compound, a cadmium compound, a manganese compound, a magnesium compound, a cobalt compound, a silicon compound, a tin compound, a lead compound, and an aluminum compound.In particular, the catalyst comprises at least one of germanium dioxide, cobalt acetate, titanium tetrachloride, titanium phosphate, titanium tetrabutoxide, titanium tetraisopropoxide, titanium tetra-n-propoxide, titanium tetraethoxide, titanium tetramethoxide, tetrakis(acetylacetonato)titanium complex, tetrakis(2,4-hexanedionato)titanium complex, tetrakis(3,5-heptanedionato)titanium complex, dimethoxybis(acetylacetonato)titanium complex, diethoxybis(acetylacetonato)titanium complex, diisopropoxybis(acetylacetonato)titanium complex, di-n-propoxybis(acetylacetonato)titanium complex, dibutoxybis(acetylacetonato)titanium complex, titanium dihydroxybisglycolate, titanium dihydroxybisglycolate, titanium dihydroxybislactate, titanium dihydroxybis(2-hydroxypropionate), titanium lactate, titanium octanedioate, titanium dimethoxybistriethanolamineate, titanium diethoxybistriethanolamineate, titanium dibutoxybistriethanolamineate, hexamethyl dititanate, hexaethyl dititanate, hexapropyl dititanate, hexabutyl dititanate, hexaphenyl dititanate, octamethyl trititanate, octaethyl trititanate, octapropyl trititanate, octabutyl trititanate, octaphenyl trititanate, hexaalkoxy dititanate, zinc acetate, manganese acetate, methyl silicate, zinc chloride, lead acetate, sodium carbonate, sodium bicarbonate, acetic acid, sodium sulfate, potassium sulfate, zeolite, lithium chloride, magnesium chloride, iron chloride, zinc oxide, magnesium oxide, calcium oxide, barium oxide, antimony trioxide, and antimony triacetate. Alternatively, the catalyst is selected from nanoparticles. The chemical agent can be selected from any catalyst known to those skilled in the art having the ability to decompose and / or depolymerize the target polymer.

[0138] At the end of the alkaline chemical depolymerization step, a "reaction solution" is obtained, which contains the monomers MEG and dicarboxylates such as terephthalate.

[0139] In another embodiment, the depolymerization of the polyester having at least one MEG unit is biological depolymerization, preferably hydrolysis, more preferably enzymatic depolymerization. Preferably, the biological depolymerization is alkaline enzymatic depolymerization.

[0140] The term "biological depolymerization" refers to a method in which the depolymerization of at least one polyester having at least one MEG unit is carried out by contacting at least one polyester having at least one MEG unit with a biological agent capable of decomposing the polyester. Biological depolymerization is carried out by hydrolysis. In a preferred embodiment, the hydrolysis is alkaline hydrolysis. As an example, the biological alkaline hydrolysis of PET produces terephthalic acid (TA) salts and ethylene glycol (MEG).

[0141] In a particular embodiment, the depolymerizing agent is a biological depolymerizing agent. In particular, the biological depolymerizing agent is an enzyme (i.e., depolymerase). In this case, the biological depolymerization is called enzymatic depolymerization. Alternatively, and / or additionally, the biological depolymerizing agent is a microorganism that expresses and secretes the depolymerase. Preferably, the enzyme can decompose a polyester, more preferably the polyester object of the present invention having at least one MEG unit. As an example, the depolymerase can decompose PET into monomeric forms, i.e., TA, MEG, mono-2-hydroxyethyl terephthalate (MHET), and / or bis(2-hydroxyethyl) terephthalate (BHET), as an enzyme.

[0142] In one embodiment, the enzyme is selected from esterases. In a preferred embodiment, the enzyme is selected from lipases or cutinases. In a particular embodiment, the plastic product is contacted with at least two different depolymerases.

[0143] In certain embodiments, when the target polyester is PET, the depolymerase is an esterase. In particular, the depolymerase is a cutinase, preferably a cutinase produced by a microorganism selected from Thermobifida cellulosityca, Thermobifida halotolerans, Thermobifida fusca, Thermobifida alba, Bacillus subtilis, Fusarium solani pisi, Humicola insolens, Sirococcus conigenus, Pseudomonas mendocina, Thielavia terrestris, Saccharomonospora viridis, and Thermomonospora curvata, or any functional variant thereof. In another embodiment, the cutinase is selected from a metagenomic library, such as the LC-cutinase described in Sulaiman et al., 2012 or the esterase described in EP3517608, or any functional variant thereof comprising the depolymerases listed in WO 2018 / 011284, WO 2018 / 011281, WO 2020 / 021116, WO 2020 / 021117, WO 2020 / 021118, and WO2021005198. In another particular embodiment, the depolymerase is a lipase, preferably a lipase produced by Ideonella sakaiensis, or any functional variant thereof comprising the depolymerases listed in WO2021005199. In another particular embodiment, the depolymerase is a cutinase produced by Humicola insolens, such as that referred to as A0A075B5G4 in Uniprot or any functional variant thereof. In another embodiment, the depolymerase is selected from commercially available enzymes, such as Novozym 51032 or any functional variant thereof. In one embodiment, the enzyme is selected from an enzyme having PET-degrading activity (PETase) and / or an enzyme having MHET-degrading activity (MHETase).

[0144] In another embodiment, the depolymerizing agent is a microorganism that expresses and secretes depolymerase. In the context of the present invention, the enzyme may be secreted into the culture medium or secreted towards the cell membrane of the microorganism to which the enzyme can be immobilized. The microorganism may naturally synthesize the depolymerase or the microorganism may be a recombinant microorganism into which a recombinant nucleotide sequence encoding the depolymerase has been inserted, for example using a vector. For example, the nucleotide molecule encoding the depolymerase of interest is inserted into a vector such as a plasmid, recombinant virus, phage, episome, artificial chromosome, etc. Transformation of host cells and culture conditions suitable for the host are well known to those skilled in the art. According to the present invention, several microorganisms and / or several enzymes may be used together or sequentially to depolymerize different types of polymers contained in the same plastic article or different plastic articles.

[0145] In a particular embodiment, when the target polyester is PET, the depolymerization step is carried out at a temperature comprised between 20 °C and 90 °C, preferably between 30 °C and 80 °C, more preferably between 40 °C and 75 °C, more preferably between 50 °C and 75 °C, even more preferably between 60 °C and 75 °C. Furthermore, the depolymerization step is preferably carried out at a pH of 5 - 11, preferably 7 - 9, more preferably 7 - 8.5, even more preferably 7 - 8. In one embodiment, the depolymerization step is carried out at a pH of 6.5 - 9, preferably 6.5 - 8.5, more preferably 7 - 8, even more preferably 7.5 - 8.5. Alternatively, the depolymerization step may be carried out under industrial conditions and / or composting conditions.

[0146] In one embodiment, the depolymerization of a polyester having at least one MEG unit is obtained from biological depolymerization in which the pH of the reaction medium is adjusted between 6.5 and 9 by the addition of a base into the reaction medium. Any base known to those skilled in the art may be used. In particular, the base is selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH), or ammonia (NH4OH). Advantageously, the base is sodium hydroxide (NaOH). The time required for the depolymerization step can vary depending on the polyester itself (i.e., origin, its composition, etc.), the type and amount of the depolymerizing agent used, as well as various process parameters (i.e., temperature, pH, additional agents, etc.). Those skilled in the art can easily adapt the parameters of the depolymerization process step. Examples of said methods are described in WO 2014 / 079844, WO 2015 / 097104, WO 2015 / 173265, WO 2017 / 198786, WO 2020 / 094661, and WO 2020 / 094646.

[0147] At the end of the alkaline biological depolymerization process, a "reaction solution" is obtained, which contains monomeric MEG, and / or dicarboxylate salts, such as terephthalate salts, and / or oligomers, such as DEG or TEG, and / or derivatives thereof including mono-2-hydroxyethyl terephthalate (MHET) and / or dimethyl terephthalate (DMT), and / or colorants, and / or water. In certain embodiments, the reaction solution of the depolymerization of at least one polyester having at least one MEG unit contains dicarboxylate salts and MEG, as well as undepolymerized polyesters such as PET. In a preferred embodiment, the reaction solution of the depolymerization of at least PET contains terephthalate salts, MEG, and undepolymerized PET.

[0148] In some embodiments, the reaction solution obtained at the end of the depolymerization step is used as the solution obtained from the depolymerization of at least one polyester having at least one MEG unit in the purification method according to the present invention. In an alternative embodiment, the reaction solution obtained at the end of the depolymerization step is subjected to one or several preliminary steps of the purification method as disclosed in the following paragraphs to obtain a solution obtained from the depolymerization of at least one polyester having at least one MEG unit for use in the purification method according to the present invention.

[0149] Any preliminary step of the purification method The reaction solution obtained at the end of the depolymerization step can be subjected to one or more steps before being subjected to the purification method according to the present invention. For example, said steps enable the removal of any solid residues, the purification of the dicarboxylate salts and / or the decolorization of the reaction solution. Specific examples of said preliminary steps can be found in WO 2020 / 094661.

[0150] In one embodiment, the "reaction solution" can be subjected to one or more of the steps selected from the group consisting of filtration, purification of the filtrate, precipitation and evaporation concentration before entering the MEG purification method of the present invention. Preferably, the reaction solution can be subjected to one or more of the steps selected from the group consisting of filtration, decolorization, precipitation and evaporation concentration.

[0151] In one embodiment, the solution obtained from the depolymerization of at least one polyester having at least one MEG unit is obtained from the reaction solution of the depolymerization of at least one polyester having at least one MEG unit and containing dicarboxylate salts and MEG, and is subjected to one or more of the steps selected from the group consisting of filtration, decolorization, precipitation and evaporation concentration.

[0152] Filtration Filtration means separating undepolymerized polyester solids, such as PET, from the liquid phase of the reaction medium (including dissolved dicarboxylate salts such as TA salts and MEG). The filtration threshold and other filtration conditions, such as the optional presence of filter aids, can be adapted by those skilled in the art. Alternatively, the separation of undepolymerized polyester can also be carried out by centrifugation or any other method known to those skilled in the art.

[0153] The filtrate containing dissolved dicarboxylate salts such as TA salts and the desired MEG is retained.

[0154] Purification of filtrate The filtrate may be purified by subjecting it to one or several steps selected from ultrafiltration, decolorization, passage through ion exchangers and chromatography. Preferably, the filtrate is subjected to decolorization by adsorption on activated carbon. Any other equivalent method known to those skilled in the art can be used.

[0155] Precipitation of dicarboxylic acid by acidification of the solution and subsequent filtration Precipitation by acidification means the precipitation of dicarboxylic acids such as TA by adding acid to the reaction solution to form a slurry. The acid can be selected from the group consisting of mineral acids such as sulfuric acid, hydrochloric acid, phosphoric acid or nitric acid, organic acids such as acetic acid and mixtures thereof. Alternatively, precipitation by acidification can be carried out by an overpressure of CO2. Following this operation, filtration is carried out to remove the precipitated dicarboxylic acid. Finally, the filtrate contains MEG and MEG containing soluble residual salts (such as sodium sulfate). Any other method for removing salts can be easily implemented by those skilled in the art.

[0156] For example, a filtrate containing a dicarboxylate salt such as TA salt can be subjected to all or part of the following steps: 1. Purification of the filtrate by subjecting the solution to one or several steps selected from ultrafiltration, carbon adsorption, feeding to ion exchange resins and chromatography; and / or 2. Precipitation by acidification of dicarboxylic acids such as TA contained in the refined filtrate using a mineral acid (selectable from the following: sulfuric acid, chloric acid, phosphoric acid or nitric acid) or an organic acid (such as acetic acid) or a mixture thereof. The solution can also be acidified by an overpressure of CO2. This step also includes solubilization and precipitation of salts formed simultaneously with dicarboxylic acids such as TA; and / or 3. Filtration to recover a filtrate containing MEG containing soluble residual salts (such as sodium sulfate) and dicarboxylic acids in solid form such as TA from a solution containing precipitated dicarboxylic acids such as TA. Therefore, prior to the method of the present invention, at least 80%, preferably at least 90%, more preferably 95%, even more preferably more than 98% or equivalent of dicarboxylic acids such as TA is removed from the reaction medium.

[0157] Evaporation concentration process to obtain a concentrated MEG solution The purpose of this step is to remove most of the dissolved salts such as sodium sulfate from the above solution and to obtain a concentrated solution of MEG.

[0158] The evaporation concentration step means an operation of dehydrating the filtrate by heating under vacuum. When the desired pressure (vacuum) is reached, water evaporates and residual salts such as sodium sulfate crystallize. Thereafter, the crystallized salts are filtered off to obtain a concentrated solution (filtrate) of MEG and a cake of crystallized salts. This cake can be washed with water, and the washing water is combined with the filtrate and then returned to the evaporator. This washing operation can be repeated several times by washing the filtered cake again, and the washing liquid can be combined with the filtrate and the mixture can be subjected to the evaporation concentration step again. Advantageously, the washing operation is repeated 3 times to extract the salts to the maximum while minimizing the loss of MEG.

[0159] Finally, an aqueous concentrated solution of MEG is obtained.

[0160] For the following steps, this aqueous concentrated solution of MEG is referred to as the solution obtained from depolymerization.

[0161] Method for recycling a polymer-containing material comprising at least one polyester having at least one MEG unit Also, an object of the present invention is to provide a method for recycling a polymer-containing material such as a plastic product comprising at least one polyester having at least one MEG unit, the method comprising the following steps: a.1) Subjecting the polyester to a depolymerization step to obtain a reaction solution containing a dicarboxylate, MEG and a solid component; b.1) Filtering the reaction solution obtained in step (a.1) to remove the solid component and obtaining a filtrate; c.1) Purifying the filtrate obtained in step (b.1) through one or several steps preferably selected from ultrafiltration, adsorption on activated carbon, feeding to an ion exchange resin and chromatography to obtain a purified filtrate; d.1) Precipitating a dicarboxylic acid by acidifying the purified filtrate obtained in step (c.1) to obtain a slurry; e.1) Filtering the slurry obtained in step (d.1) to remove the precipitated dicarboxylic acid and obtaining a filtrate; f.1) Subjecting the filtrate obtained in step (e.1) to at least one evaporation concentration step to obtain a solution in which MEG is concentrated; g.1) Purifying the MEG of the concentrated solution obtained in step (f.1) by the method of the present invention described above and recovering the purified MEG.

[0162] In particular, step (g.1) comprises the following steps: a) Subjecting the solution obtained in step (f.1) to at least one evaporation condensation step to obtain a lower layer fraction and a condensed upper layer fraction; b) Contacting the condensed upper layer fraction obtained in step (a) with a resin to obtain a solution; c) Subjecting the solution obtained in step (b) to at least one distillation step to obtain a distillate; and d) Recovering purified MEG from the distillate obtained in step (c).

[0163] Steps d.1) and e.1) are particularly important steps for obtaining a MEG concentrated solution that contains a small amount of a salt such as the TA salt produced from the depolymerization, preferably substantially free of salt, in order to obtain MEG having the desired properties. Here, "substantially free of" means that the MEG concentrated solution obtained in step f.1) contains 3 wt.% or less, for example 1 wt.% or less, for example 0.8 wt.% or less, for example 0.7 wt.% or less, for example 0.6 wt.% or less, for example 0.5 wt.% or less of salt based on the total weight of the solution.

[0164] In one embodiment, the MEG concentrated solution obtained in step f.1) contains 65 wt.% or more, for example 68 wt.% or more, for example 70 wt.% or more, for example 75 wt.% or more, for example 80 wt.% or more of MEG based on the total weight of the solution.

[0165] In one embodiment, the MEG concentrated solution obtained in step f.1) contains 65 wt.% or more, for example 68 wt.% or more, for example 70 wt.% or more, for example 75 wt.% or more, for example 80 wt.% or more of MEG and DEG based on the total weight of the solution.

[0166] All of the embodiments disclosed in connection with a method for purifying MEG from a solution obtained from the depolymerization of at least one polyester having at least one MEG unit are also applicable to step (g.1) of a method for recycling a polymer-containing material comprising at least one polyester having at least one MEG unit. In a preferred embodiment, the polyester having at least one MEG unit is PET. In some embodiments, in step c), the solution obtained from step (b) is subjected to a double distillation in which the second distillation is a distillation involving two sections.

[0167] The depolymerization step of step a.1) is carried out, as described in the above paragraph, i.e., by a chemical or biological depolymerization step. Preferably, the depolymerization step a.1) is carried out by chemical or biological depolymerization under alkaline conditions.

[0168] In a preferred embodiment, the depolymerization step a.1) is hydrolysis under alkaline conditions. In another preferred embodiment, the step is a biological depolymerization step, i.e., enzymatic depolymerization. Alternatively, the depolymerization step a.1) is chemical hydrolysis under alkaline conditions such as saponification.

[0169] In one embodiment, the polymer-containing material comprising at least one polyester having at least one MEG unit is a plastic product.

[0170] In a particular embodiment, when the polyester having at least one MEG unit is PET, the dicarboxylic acid is terephthalic acid (TA) and the dicarboxylate is terephthalate. In such a case, the solid component removed in step (b.1) contains undepolymerized PET.

[0171] According to the present invention, the filtration of steps b.1) and e.1), the purification of the filtrate of step c.1), the precipitation by acidification of step d.1) and / or the evaporation concentration of step f.1) are carried out, as described in the above paragraph, i.e., in the preliminary steps of the purification method of the present invention. In a preferred embodiment, the method for recycling a polymer-containing material comprising at least one polyester having at least one MEG unit is carried out in the order of a.1) to g.1).

[0172] Use and Application of Purified MEG According to the present invention, the recovered MEG may be reused for synthesizing polymers, particularly polyesters containing at least one MEG unit as described above. Those skilled in the art can easily adapt the method parameters for synthesizing monomers / oligomers and polymers.

[0173] Another object of the present invention is to provide a polyester, preferably PET, containing at least one MEG unit polymerized from MEG purified by the method of the present invention.

[0174] In certain embodiments, the recovered MEG may be reused as an antifreeze.

[0175] In certain embodiments, the recovered MEG may be used as a desiccant in the gas industry.

[0176] The present invention also relates to the use of purified MEG obtained by the method according to the present invention for producing a polyester containing at least one MEG unit.

[0177] Polyester containing at least one MEG unit Another object of the present invention is to provide a polyester containing at least one MEG unit, wherein the MEG is purified MEG obtained by the method according to the present invention.

[0178] The following examples are intended to illustrate, but not to limit, the disclosed embodiments.

Examples

[0179] Example A: Method for Recycling a Plastic Product Containing the Polyester According to the Present Invention Experimental part: A - Preliminary step: Preparation and processing of PET waste In Example A1, crushed PET trays containing >98% PET were used. These were dry-mixed with 1% by weight of powdered citric acid (Orgater exp 141 / 183 manufactured by Adeka) based on the total weight of the composition, and then extruded using a twin-screw extruder Leistritz ZSE 18 MAXX including nine continuous heating zones (Z1 to Z9) and a head (Z10) (where the temperature can be independently controlled and adjusted in each zone to guide the extrusion foamed composition). The screw speed was set at 110 rpm and the total flow rate was set at 4 kg / h. When the molten polymer reached the screw head (Z10) including one die plate with a 3.5 mm hole, it was immediately immersed in a 2 m long cold water bath (10 °C). The resulting extrudate was granulated into solid pellets of 2 to 3 mm.

[0180] Thereafter, the pellets were subjected to steps B to D.

[0181] In Examples A2 and A3, washed and colored flakes from PET bottle waste containing >98% PET were atomized to fine powder with a size of <500 μm using an Ultra Centrifugal Mill ZM 200 system.

[0182] Thereafter, the powder was subjected to steps B to D.

[0183] Enzymatic depolymerization method of B-PET waste (step a1) The decomposition method was carried out using a mutant of LC-cutinase in a 1000 L reactor (usable volume 800 L) (Sulaiman et al., Appl Environ Microbiol. 2012 Mar). Such a mutant (hereinafter referred to as "LCC-ICCIG" in this specification) corresponds to the enzyme of SEQ ID NO: 1 having the following mutations F208I + D203C + S248C + V170I + Y92G and was expressed in Trichoderma reesei.

[0184] First, in the decomposition method, the processed PET waste was added at a concentration of 150 g / kg based on the total weight of the reaction medium, and LCC-ICCIG was added at a concentration of 1 mg / g PET. During all the depolymerization steps, the stirring speed was adjusted to 130 rpm, the temperature was adjusted to 60 °C, and the pH of the reaction medium was adjusted to pH 8 ± 0.05 by adding 25% NaOH solution.

[0185] The depolymerization rate was monitored by measuring the amount of NaOH added to the reaction medium to neutralize the terephthalic acid (TA) produced by depolymerization.

[0186] The depolymerization rate after 48 hours was 98%.

[0187] At the end of depolymerization, the reaction solution contains TA salt as dicarboxylate, MEG, and un-depolymerized PET in the form of solid components.

[0188] Preliminary steps of the C-MEG purification method: Removal of un-depolymerized PET and terephthalic acid (TA) salt and sodium sulfate salt Filtration (step b1) Subsequently, the reaction solution was filtered to separate the solid phase of the reaction solution in the reactor (mainly the remaining un-depolymerized PET waste) from the liquid phase of the reaction solution (containing solubilized TA salt and MEG).

[0189] The solid components removed from the fluid were removed. The filtrate containing solubilized TA salt and the desired MEG was retained.

[0190] Purification of the filtrate by adsorption on activated carbon (step c1) The filtrate containing dissolved TA salt and MEG was purified by passing it through a 1 L column of activated carbon at room temperature.

[0191] Precipitation of TA by acidification of the solution (step d1) followed by filtration (step e1) Subsequently, the purified filtrate was acidified by adding 98% sulfuric acid until the final pH reached 2.7 - 3 to precipitate TA in the solution.

[0192] As a result, TA precipitate was formed and then filtered from the slurry.

[0193] Finally, the filtrate contains MEG together with dissolved residual salts such as sodium sulfate.

[0194] Evaporation concentration step (step f1) for obtaining a concentrated MEG solution In the first evaporation stage, the product was heated to 80 °C with stirring and gradually evacuated to a pressure of approximately 300 mbar abs in the evaporator until crystals appeared.

[0195] The resulting slurry was cooled overnight to crystallize the remaining dissolved sodium sulfate. The resulting sodium sulfate crystals were filtered and then washed. The filtrate containing the wash water and MEG was then returned to the evaporator for the next stage.

[0196] These operations (evaporation / filtration / washing of sodium sulfate crystals) were repeated three times to extract the dissolved salts to the maximum extent.

[0197] Method for purifying D-MEG (step g1) Method for purifying MEG produced by enzymatic depolymerization of Example A1 - PET trays The "concentrated solution of MEG" obtained after the evaporation concentration step is hereinafter referred to as "solution" in this specification as described in the previous paragraph.

[0198] Table 1 shows the composition of the solution for proceeding with the method according to the present invention.

[0199] [Table 1]

[0200] The solution was subjected to the method of the present invention including the following steps:

[0201] (a) Evaporation condensation step The evaporation process was carried out in a continuous glass wiped film evaporator. The evaporator is heated with hot oil circulating in a double jacket. The product is continuously fed into the evaporator.

[0202] The evaporation of the solution was carried out in two stages with different conditions as described in Table 2 for example. The upper layer fraction resulting from the first evaporation stage was condensed to obtain the first condensate, while the lower layer fraction was fed to the second evaporation stage. The upper layer fraction obtained from the second evaporation process was also condensed to obtain the second condensate.

[0203] Finally, the first and second condensates were combined.

[0204]

Table 2

[0205] The heating temperature corresponds to the temperature of the hot oil circulating in the double jacket.

[0206] Condensation was carried out using a water-cooled condensation unit.

[0207] (b) Contact with resin Thereafter, the condensate obtained from step (a) was passed at room temperature through a glass column with a diameter of 50 mm and a height of 500 mm filled with 375 g of PUROLITE A860 in its OH-form. The flow rate was set so that the velocity inside the column was 1 m / h.

[0208] (c) Distillation Glass column distillation, that is, two consecutive distillation processes were carried out on the solution obtained from step (b) using 0.16-inch Pro-pak distillation packing with a height of 1200 mm (3 * 400 mm).

[0209] The column boiler is heated with hot oil circulating in the double jacket of the boiler.

[0210] The conditions of the two distillation processes are described in Table 3.

[0211] It was supplied to the column at 1.3 kg / h.

[0212]

Table 3

[0213] The heating temperature corresponds to the temperature of the hot oil circulating in the double jacket.

[0214] (d) Recovery of purified MEG The distillate containing purified MEG recovered from the method of the present invention has the properties described in Table 4. The results are compared with the desired specification values of MEG used to produce PET and plastic bottles. These specification values can be confirmed in the material data sheet of commercially available mono-ethylene glycol polyester grade.

[0215]

Table 4

[0216] In conclusion, the method according to the present invention provides a purity exceeding 99.9%, which is similar to the purity of petrochemical-derived MEG commercially available for producing PET and plastic bottles. In addition, the method of the present invention can also meet other specified specification values as illustrated in Table 4.

[0217] Method for purifying MEG produced by enzymatic depolymerization of Example A2 - PET bottle For this example, the composition of the solution to proceed to the purification section is shown in Table 5.

[0218]

Table 5

[0219] The said solution was subjected to the method of the present invention including the following steps:

[0220] (a) Evaporation and condensation process The evaporation process was carried out in a batch-type stainless-steel evaporator. The 100 L evaporator is equipped with stirring and heated by hot oil circulating in a double jacket.

[0221] Evaporation was carried out under the conditions disclosed in Table 6 below and as described in Example A1.

[0222] [Table 6]

[0223] The heating temperature corresponds to the temperature of the hot oil circulating in the double jacket.

[0224] Condensation was carried out using a water-cooled tube condenser.

[0225] (b) Contact with resin The deacidification process was carried out in an 8 L glass column filled with 3.5 l of OH-form PUROLITE A860. The condensate obtained during step (a) was continuously fed to the column at room temperature at a flow rate set so that the velocity inside the column was 0.8 m / h.

[0226] (c) Distillation Two distillation operations were carried out using glass column distillation. The columns used for these experiments had the following characteristics: · Diameter: 50 mm · Packing: Sulzer packing BX · Useful packing height: 1000 mm / section

[0227] The column boiler is heated by hot oil circulating in the shell of a falling-film evaporator.

[0228] The conditions for the two distillation steps are described in Table 7.

[0229] [Table 7]

[0230] The heating temperature corresponds to the temperature of the hot oil circulating in the double jacket.

[0231] (c’) Polishing step The distillate obtained from the previous step (c) was subjected to an additional polishing step. The step was carried out in a 2.5 cm diameter glass column filled with activated carbon. The distillate was continuously fed to the column at room temperature. The flow rate was set to 0.6 l / h so that the velocity in the column was 1.2 m / h.

[0232] (d) Recovery of purified MEG When the purified MEG recovered from the method of the present invention was analyzed, it had the characteristics listed in Table 8. Similar to Example A1, the results were compared with the desired specification values of petrochemical-derived MEG conventionally used for producing PET and plastic bottles.

[0233]

Table 8

[0234] In conclusion, the method for purifying MEG according to the present invention provides a purity exceeding 99.9%, which is similar to petrochemical-derived MEG conventionally used for producing PET and plastic bottles. In addition, the method of the present invention can also meet other specified specification values as illustrated in Table 8.

[0235] Furthermore, using the MEG purified according to the present invention and TA purified from a depolymerization method as described in WO 2014 / 079844, WO 2015 / 097104, WO 2015 / 173265, WO 2017 / 198786, WO 2020 / 094661 and WO 2020 / 094646, we successfully produced transparent bottles.

[0236] Method for purifying MEG produced by enzymatic depolymerization of PET bottle flakes, including distillation with two sections, Example A3 Table 9 shows the composition of the solution for proceeding with the method according to the present invention.

[0237] [Table 9]

[0238] The said solution was subjected to the method of the present invention including the following steps:

[0239] (a) Evaporation and condensation step The evaporation step was carried out in a continuous 0.5 m 2 stainless steel wiped film evaporator. The evaporator was heated with steam circulating in the double jacket. The product was continuously fed to the evaporator.

[0240] The evaporation of the solution was carried out in two stages with different conditions as described in Table 10, for example. The upper layer fraction resulting from the first evaporation stage was condensed to obtain the first condensate, while the lower layer fraction was fed to the second evaporation stage. The upper layer fraction obtained from the second evaporation step was also condensed to obtain the second condensate.

[0241] Finally, the first and second condensates were combined.

[0242] [Table 10]

[0243] The heating temperature corresponds to the steam temperature circulating in the double jacket.

[0244] The condensation was carried out using a water-cooled condensation unit.

[0245] (b) Contact with resin Thereafter, the condensate obtained from step (a) was passed through a high glass column filled with its OH-form of PUROLITE A860 at room temperature. The flow rate was set so that the velocity in the column was 1 m / h.

[0246] (c) Distillation The setup used for the two consecutive distillations is based on Example A2, introducing an auxiliary upper section to the second distillation so that MEG is collected by side stream withdrawal.

[0247] The column boiler is heated with hot oil or steam circulating within a double jacket.

[0248] The conditions for the two distillation steps are described in Table 11.

[0249] [Table 11]

[0250] (d) Recovery of purified MEG The distillate containing purified MEG recovered from the method of the present invention has the properties described in Table 12. The results are compared with the desired specification values of MEG used for producing PET and plastic bottles. These specification values can be confirmed in the material data sheet of commercially available mono-ethylene glycol polyester grade materials.

[0251] [Table 12]

[0252] In addition, the recovered purified MEG exhibits an α-boiling number of less than 20. Such a specification can be easily measured by those skilled in the art. As an example, the α-boiling can be measured according to the ASTM D-5386 method after heating the sample at 198 °C for 4 hours.

[0253] In conclusion, the method according to the present invention provides a purity exceeding 99.9%, which is similar to the purity of commercially available petrochemical-derived MEG for producing PET and plastic bottles. In addition, the method of the present invention can also meet other specified standard values as illustrated in Table 12.

Claims

1. A method for purifying MEG from a depolymerization solution of at least one polyester having at least one monoethylene glycol (MEG) unit, comprising the following steps: a) A step of subjecting the depolymerization solution to at least one evaporation condensation step to obtain a lower layer fraction and a condensed upper layer fraction, b) A step of bringing the condensed upper layer fraction obtained in step (a) into contact with a resin to obtain a solution. c) A step of subjecting the solution obtained in step (b) to at least one distillation step to obtain a distillate, and d) A step to recover purified MEG from the distillate obtained in step (c).

2. The method according to claim 1, further comprising step (c'), which involves subjecting the distillate obtained in step (c) to one or more steps selected from the group consisting of distillation, hydrogenation, dehydration, and decolorization, preferably a distillation step and / or a decolorization step, before the recovery step (d), wherein the decolorization step is preferably carried out by activated carbon adsorption.

3. The method according to claim 1 or 2, wherein the polyester having at least one MEG unit is selected from the group consisting of polyethylene terephthalate (PET), polyethylene adipate (PEA), polyethylene-2,5-furanoleate (PEF), and polyethylene naphthalate (PEN), and preferably the polyester is PET.

4. The method according to claim 1 or 2, wherein the depolymerization is biological depolymerization, preferably hydrolysis, more preferably enzymatic depolymerization, and even more preferably alkaline enzymatic depolymerization.

5. The method according to claim 1 or 2, wherein the depolymerization is chemical depolymerization, preferably hydrolysis, more preferably alkaline chemical hydrolysis such as saponification.

6. The method according to claim 1 or 2, wherein the depolymerization solution is a reaction solution for the depolymerization of at least one polyester having at least one MEG unit, comprising a dicarboxylate and MEG, and subjected to one or more steps selected from the group consisting of filtration, decolorization, precipitation and evaporation concentration.

7. The method according to claim 1 or 2, wherein the evaporation of the evaporative condensation in step (a) is carried out in a thin-film evaporator, a batch evaporator, a forced-circulation evaporator, or a flash evaporator, preferably in a thin-film evaporator.

8. The method according to claim 1 or 2, wherein step (a) includes one additional evaporation condensation step of subjecting the lower fraction obtained from a first evaporation condensation step to a second evaporation condensation step, and the condensed upper fractions obtained from the first and second evaporation condensation steps are mixed before being subjected to step (b).

9. The method according to claim 8, wherein the lower fraction obtained from the first evaporative condensation step is filtered before being subjected to the second evaporative condensation step, and / or the evaporation in the second evaporative condensation step is carried out in a thin-film evaporator.

10. The method according to claim 1 or 2, wherein step (b) is performed by passing the condensed upper fraction obtained in step (a) through an ion exchange resin, preferably a strong anion exchange resin.

11. The method according to claim 1 or 2, wherein the evaporation of the first and / or second evaporative condensation step of step (a) and / or the distillation step of step (c) are carried out under vacuum conditions, preferably at a pressure of 15 to 500 mbar abs, more preferably at 100 mbar abs.

12. The method according to claim 1 or 2, comprising or consisting of the following steps: a. A step of subjecting the depolymerization solution to at least one evaporative condensation step, preferably two evaporative condensation steps, both performed in a thin-film evaporator, to obtain a mixture of a lower layer fraction and a condensed upper layer fraction. b. A step of contacting the condensed upper fraction obtained in step (a) with a strong anion exchange resin to obtain a solution. c. A step of subjecting the solution obtained in step (b) to double distillation, wherein the second distillation is optionally a distillation involving two sections, and d. A step to recover purified MEG from the distillate obtained in step (c).

13. A method for recycling a polymer-containing material comprising at least one polyester having at least one MEG unit, the method comprising the following steps: a. 1) A step of subjecting a polyester having at least one MEG unit to a depolymerization step, preferably hydrolysis under alkaline conditions, preferably enzymatic depolymerization, to obtain a reaction solution containing a dicarboxylate salt, MEG, and a solid component. b. 1) The reaction solution obtained in step (a.1) is subjected to filtration to remove solid components and obtain a filtrate. c. 1) Purifying the filtrate obtained in step (b.1) through one or more steps selected from ultrafiltration, adsorption on activated carbon, transfer to an ion exchange resin, and chromatography to obtain a purified filtrate. d. 1) A step to obtain a slurry by acidifying the purified filtrate obtained in step (c.1) to precipitate the dicarboxylic acid. e. 1) The slurry obtained in step (d.1) is subjected to filtration to remove the precipitated dicarboxylic acid and obtain a filtrate. f. 1) A step of subjecting the filtrate obtained in step (e.1) to at least one evaporation concentration step to obtain a solution in which MEG is concentrated, g. 1) A step of purifying the MEG of the concentrated solution obtained in step (f.1) by the method of claim 1 or 2, and recovering the purified MEG.

14. The method according to claim 13, wherein the polyester having at least one MEG unit is PET, the dicarboxylic acid is terephthalic acid (TA), and the dicarboxylate salt is a terephthalate salt.

15. Use of purified MEG obtained by the method of claim 1 or 2 for producing a polyester containing at least one MEG unit.