Production of rpet suitable for rpet bottles for the beverage industry by the use of chemical recovered bhet

Abstract

The present invention relates to a process for continuous production of polyethylene terephthalate (PET), preferably recycled PET (rPET), in a plant comprising a first group of at least one reactor, a second group of at least one reactor, a third group of at least one reactor, and a final reactor, wherein a reactant material B) comprising melted bis(2-hydroxyethyl) terephthalate (BHET); and a reactant material C) comprising isophthalic acid (IPA), preferably in form of a paste (IPA paste), are used; wherein the second group of at least one reactor, the first group of at least one reactor, the third group of at least one reactor, and the final reactor are connected in series in this order, the process comprising i-c) subjecting a mixture of the reactant material B), water and the reactant material C) to a hydrolysis reaction in the second group of at least one reactor to form a fully or partially hydrolysed reaction material stream; ii-c) subjecting the fully or partially hydrolysed reaction material stream to further reaction in the first group of at least one reactor including esterification reaction to form a reaction material stream C); iii-c) pre-polycondensing of the reaction material stream C) in the third group of at least one reactor to form a pre-polycondensed reaction material stream; and iv-c) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET.

Description

[0001] EPC Engineering & Technologies GmbH October 11, 2024 M / EPC-105-PC Meissner Bolte Partnerschaft mbB

[0002] Production of rPET suitable for rPET bottles for the beverage industry by the use of chemical recovered BHET

[0003] The present invention relates to a process for continuous production of polyethylene terephthalate (PET), preferably recycled PET (rPET), in a plant comprising a plurality of reactors, wherein a reactant material B) comprising melted bis(2-hydroxyethyl) terephthalate (BHET); and a reactant material C) comprising isophthalic acid (IPA) are used.

[0004] Polyethylene terephthalate (PET) is a thermoplastic polymer from the polyester group, which is widely used in everyday products such as bottles, films and textiles due to its advantageous properties such as lightness, flexibility and impact resistance. PET is typically synthesized by the esterification reaction between terephthalic acid (TPA) and ethylene glycol (MEG).

[0005] The production of PET chips for bottles for the beverage industry essentially consists of the following plant areas:

[0006] • Conveyor systems, additive processing units and dosing systems with paste processing to supply the esterification line

[0007] • 2-stage esterification reaction: stage 1 and 2 with connected process column

[0008] • 1- or 2-stage pre-polycondensation: with adapted pre-polycondenser with process steam condensation system and

[0009] • final polycondensation unit with process steam condensation system

[0010] Individual polymer distribution with polymer filter for chip production M / EPC-105-PC

[0011] 2

[0012] • PET chips production with melt strand casting head, strand guiding device and water-cooling section, granulating unit, drying and screening

[0013] • Solid state polycondensation (SSP) to increase the desired limiting viscosity (intrinsic viscosity) and to diffuse the acetaldehyde content

[0014] • Intermediate storage in silos, quality control and bagging, e.g. in big bags

[0015] In the multi-stage continuous PET process based on TPA and MEG, the raw materials terephthalic acid (TPA) and ethylene glycol (MEG) are converted into a low-molecular compound (monomer) through esterification reactions and then into a high-molecular linear polymer through polycondensation reaction.

[0016] First, the PTA powder and MEG are mixed at ambient temperature to form the so- called "paste" in the 'paste preparation vessel'. Then it is fed to the first esterification reactor.

[0017] The esterification reaction is usually carried out in 2 stages. An additional amount of ethylene glycol above stoichiometric requirements is used to accelerate the reaction rate and achieve the reaction equilibrium phase. The esterified mixture of the first stage is fed to the second stage esterification where the esterification reaction is completed with high conversion rate.

[0018] Polyesterification includes the following reactions: a) free acidic end groups react very quickly with free hydroxyl end groups and form longer macromolecules with elimination of process water (split water); of course, this goes hand in hand with the classic polycondensation, where b) the low-molecular-weight glycol terephthalate units are also formed by catalyst propulsion into longer macromolecules with the splitting off of glycol (split glycol).

[0019] A reaction product (byproduct) of the esterification reaction is water vapor which, due to the chemical-physical equilibrium, is fed to a distillation column together with MEG vapors for separation. The esterification product is then fed M / EPC-105-PC

[0020] 3 continuously to the subsequent pre-polymerization (or pre-polycondensation) stage.

[0021] The second stage of the reaction progresses under a defined vacuum and temperature, first in the pre-polycondensation, followed by the final polycondensation, in which monomer molecules continue to connect and lengthen, releasing ethylene glycol and water (residual esterification).

[0022] The polycondensation reaction is usually carried out in two or three stages: prepolycondensation 1 (or pre-polycondensation 1+2) and at the end the final polycondensation. The glycol released by chain growth is removed from the reactors using a vacuum system consisting of a vapor condensation stage, vacuum jet system and vacuum pumps.

[0023] The final polycondensation can take place in a horizontal reactor equipped with agitator made up of multiple types of disks, where the prepolymer mass is subjected to high temperature and low pressure throughout the process. Due to these extreme conditions, the molecular growth reaction is greatly accelerated, resulting in a linear polymer with high molecular weight and high viscosity. In order to ensure the reaction rate during the polycondensation process, it is usually necessary to add a catalyst, for example, an antimony compound at the proper time.

[0024] Granulating systems with e.g. continuous casting heads and a chips-water circulation and cooling system for transport and solidification are used for further processing of the PET product. The strands are cut to the desired size, cooled and dried. They are then separated from oversized particles using a conventional vibrating conveyor screen.

[0025] In a further process sequence, the PET chips can be transferred to a solid state polycondensation (SSP). There - based on the residence time, process gas (N2) quality and temperature - the required increase up to the desired limiting viscosity (intrinsic viscosity) takes place. The acetaldehyde trapped in the structure of the PET chips is also diffused out along the SSP process along with the reaction products, cracked glycol and process water. M / EPC-105-PC

[0026] 4

[0027] The finished PET chips are fed to the packaging station via silos and silo mixing plants, where they are filled and stored.

[0028] For reasons of sustainability and specifications, it is desired to use a recycled material for the preparation of PET. Since 2019, at European level, the amount of recycled material that must be used in beverage bottles has been determined. A bottle made of PET must therefore consist of at least 25 percent recycled plastics from 2025. From the year 2030, the required proportion in bottles will be increased to 30 percent.

[0029] More and more companies are therefore committing to use recycling plastics to produce new PET bottles. However, reused PET chips have significantly worse physical and chemical properties. In fact, PET bottles made from them do not meet industry specifications.

[0030] There are existing prior art technology, in which BHET is directly used in the reaction of PET production. However, BHET has an average chain length of "1" with no reactive carboxyl end group. The problem arises for the thermally moderate polycondensation reaction with a downstream solid-state polycondensation that the productivity of such a PET production plant is reduced by approximately 30%. In addition, this PET does not meet the usual PET quality requirements and has different processing properties in subsequent processes.

[0031] Hence, the object of the present invention was to provide a process for production of PET, preferably rPET, in which at least a part of the raw materials used can be replaced by a recycling material, wherein at the same time a high quality PET can be still obtained. In addition, the productivity of the PET production plant should be high, in particular it should not be significantly reduced with respect to a conventional PET production plant based on TPA and MEG.

[0032] The inventors have found that this object can be solved by a modified process for the production of PET in which the raw materials TPA and EG used in classic esterification of PET are replaced by bis(2-hydroxyethyl terephthalate) (BHET), in particular recycled BHET. Recycled BHET can be obtained e.g. by chemical recycling of PET waste, in particular it is a depolymerized PET waste, and hence a M / EPC-105-PC

[0033] 5 recycled material. The end product obtained with using recycled BHET is then so- called recycled PET (rPET).

[0034] Accordingly, the invention relates to a process for variable continuous production of polyethylene terephthalate (PET) in a plant comprising a first group of at least one reactor, a second group of at least one reactor, a third group of at least one reactor, and a final reactor, wherein the following reactant materials are used: a reactant material B) comprising melted bis(2-hydroxyethyl) terephthalate (BHET); a reactant material C) comprising isophthalic acid (IPA), wherein the reactant material C) is preferably in form of a paste (IPA paste); wherein the second group of at least one reactor, the first group of at least one reactor, the third group of at least one reactor, and the final reactor are connected in series in this order, wherein the process comprises i-c) subjecting a mixture of the reactant material B), water and the reactant material C) to a hydrolysis reaction in the second group of at least one reactor to form a fully or partially hydrolysed reaction material stream, preferably a partially hydrolysed reaction material stream; ii-c) subjecting the fully or partially hydrolysed reaction material stream to further reaction in the first group of at least one reactor including esterification reaction to form a reaction material stream C); iii-c) pre-polycondensing of the reaction material stream C) in the third group of at least one reactor to form a pre-polycondensed reaction material stream; and iv-c) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET.

[0035] The identification of features serves for easier reference thereto and is arbitrary. In this regard, the following alternative identifications for certain features may be also suitable: The first group of at least one reactor may be termed the second M / EPC-105-PC

[0036] 6 group of at least reactor (specific reactor ES2 remains reactor ES2) and correspondingly the second group of at least one reactor may be termed the first group of at least reactor (specific reactor ESI.5 could then be termed ESI). Moreover, reactant material B) could be termed reactant material A) and correspondingly reactant material C) could be termed reactant material B). The reactions steps i-c), ii-c), iii-c and iv-c) could be termed i), ii), iii) and iv). The reaction material stream C) may be termed reaction material stream A).

[0037] The inventive process enables the use of BHET as a raw material for PET production instead of PTA and MEG. Since BHET is available as a recycling product BHET, in particular in form of a waste recycling product of PET waste, namely depolymerized PET waste, the process can be operated with raw materials which are in part or completely a recycling material so that a PET obtained is rPET.

[0038] The most important component of the invention is that the inventive process enables processing of the e.g. purchased BHET, beginning with the melting and mixing of the BHET, hydrolyzing BHET and injecting IPA, and feeding it into the esterification reaction stage of the plant. This process ensures that the molecular chain length distribution and the number of required hydroxyl and carboxyl end groups correspond to those of the classic esterification product in the conventional polyester process. This results in a rPET end product, in particular a rPET end product, that has physical and chemical properties that are almost comparable to those of conventional PET, preferably conventional PET suitable for bottle production.

[0039] With the use of BHET, the waste and raw material cycle can be expanded, because today's BHET manufacturing processes can use polyester from different types of waste (e.g. textile polyester waste, polyester packaging material waste and others), and yet still able to produce a homogeneous BHET quality suitable for use in PET polycondensation plants.

[0040] The newly developed technology enables the use of BHET as a raw material, provided that it is based on the special technology for BHET processing and an adaptation in the reaction process of e.g. existing polycondensation plant as defined in the inventive process. The productivity in the entire inventive PET production does not suffer from any restrictions and the quality parameters are M / EPC-105-PC

[0041] 7 on the same level as from the conventional PET plants based on 100% TPA and EG as raw materials.

[0042] The depolymerization of collected PET bottles into BHET enables a recycling process to produce rPET with comparable physical and chemical properties to conventional bottle PET. Furthermore, the produced rPET is not downcycled by mechanical recycling methods and thus can be reused for the same applications as conventional PET. The use of BHET in rPET bottles reduces the amount of PET waste that is landfilled and used for energy, thus protecting the environment.

[0043] Essentially, the invention can be used to significantly increase the proportion of recycled PET material in the area of PET production for a sensible circular economy. This means a reduction in raw materials and protection of the environment.

[0044] The required qualities of PET, e.g. for PET bottles in the beverage and food sector, are maintained and on a similar level as compared to conventional PET production based on TPA and MEG.

[0045] The technology of the inventive process can be used to substitute the conventional raw materials TPA and EG. The technology described is also suitable for the construction of a new PET plant.

[0046] In the following, the invention is described in detail.

[0047] The inventive process is a process for continuous production of polyethylene terephthalate (PET), preferably recycled PET (rPET), carried out in a plant comprising a first group of at least one reactor, a second group of at least one reactor, a third group of at least one reactor, and a final reactor.

[0048] The first group of at least one reactor may be one, two or more reactors. In a preferred embodiment, the first group of at least one reactor comprises or consists of one or two reactors, preferably one reactor. A reactor may include one, two or more reactor stages, preferably one reactor stage. Any single reactor stage enables to carry out the reaction, here the esterification reaction, in one reaction stage. Two or more reactor stages can be two or more compartments in M / EPC-105-PC

[0049] 8 a reactor, in which the reaction can be carried out separately in stages (a reaction stage in each compartment).

[0050] In a preferred embodiment, the first group of at least one reactor comprises or consist of one reactor.

[0051] The second group of at least one reactor may be one, two or more reactors. In a preferred embodiment, the second group of at least one reactor comprises or consists of one reactor.

[0052] The third group of at least one reactor may be one, two or more reactors. In a preferred embodiment, the third group of at least one reactor comprises or consists of one, two or three reactors, preferably one or two reactors, more preferably two reactors.

[0053] In a particular preferred embodiment, the first group of at least one reactor comprises or consists of one reactor, the second group of at least one reactor comprises or consists of one reactor, and the third group of at least one reactor comprises or consists of one or two reactors, preferably two reactors.

[0054] The reactors of the first group of at least one reactor and the second group of at least one reactor are preferably vertical reactors. The reactor(s) of the third group of at least one reactor can be horizontal reactor(s), vertical reactor(s) or a combination of horizontal reactor(s) and vertical reactor(s). In a preferred embodiment, the reactor(s) of the third group of at least one reactor are at least two reactors, preferably two reactors, wherein the first reactor is a vertical reactor and the last reactor is a horizontal reactor. The final reactor is preferably a horizontal reactor.

[0055] The vertical reactors can be stirred-tank reactors. The vertical reactors, preferably in form of a stirred-tank reactor, are typically configured with internal and / or external heating means such as internal heat coils and / or external jacket heater. The horizontal reactor(s) can be a horizontal agitated reactor or a cage type reactor. The horizontal reactor(s) are preferably horizontal agitated reactor equipped with an agitator made up of multiple types of disks.

[0056] The inventive process is a continuous process. M / EPC-105-PC

[0057] 9

[0058] Some of the mandatory or optional compounds used as raw material as well as possible reaction products possibly generated during the process are described in more detail.

[0059] Terephthalic acid, abbreviated as TPA, is a monomer used for in conventional PET production. It has a molar mass of about 166.14 g / mol. TPA has the following chemical formula:

[0060] Ethylene glycol, abbreviated as MEG or EG is one monomer of the conventional PET production. It is also termed monoethylene glycol, glycol or 1,2-ethanediol. It has a molar mass of about 62.07 g / mol. MEG has the following chemical formula:

[0061] H H

[0062] HO- C - C -OH i T H H

[0063] Diethylene glycol, abbreviated as DEG, is a bi-functional alcohol and can optionally be a co-monomer in PET production. One the one hand, it can be a product of a reaction of 2 EG molecules reacted to 1 DEG molecule during PET production while polycondensation runs and thus as an ether group increment is integrated within the polymer chain. On the other hand, DEG is optionally used by purpose by internal generation and or by addition to the process, as a part of a certain co-monomer recipe for the PET production, thus to realize certain crystallization and glass transition behavior. It has a molar mass of about 106.12 g / mol. DEG has the following chemical formula:

[0064] H H H H

[0065] HO— C — C — O— C — C — OH

[0066] H H H H

[0067] Isophthalic acid, abbreviated as IPA, is another type of possible co-monomer for PET production. On the one hand, the meta phthalic acid group within the M / EPC-105-PC

[0068] 10 structure of a PET molecule affects the polymer morphology and the micro / macro Brownian molecular motion level. On the other hand, this meta phthalic structure suppresses the PET recrystallization behavior, which can be an important factor to realize improved cycle times (operation times) during PET chips re-melting for preforms production. It has a molar mass of about 166.14 g / mol. IPA has the following chemical formula:

[0069] Bis-(2-hydroxyethyl) terephthalate, abbreviated as BHET, used as raw material in the inventive process can be considered as a reaction product, which is a 'theoretical ester molecule' from 2 moles EG + 1 mole PTA and is mainly produced in esterification reaction stage 1 and continued in stage 2 in conventional PET production. BHET is the theoretical module for building the PET polymer chain. BHET has the following chemical formula:

[0070] The structural formula will represent the ideal BHET molecule, thus in reality several length and end group modifications are possible.

[0071] The reactant material B) comprises melted bis(2-hydroxyethyl) terephthalate (BHET). The reactant material B) is in form of a melt. It is generally preferred to melt BHET in a melting device. According to the present invention, a mixture of reactant material B) comprising melted BHET, water and reactant material C) is formed in the single or first reactor of the second group of at least one reactor or a mixture of reactant material B) comprising melted BHET, water and reactant material C) is formed beforehand and the mixture is fed to the single or first reactor of the second group of at least one reactor. M / EPC-105-PC

[0072] 11

[0073] The BHET used as the starting material to be melted may be ideal or pure BHET or may include apart from BHET "esterification products" of BHET with one or more TPA molecules or one or more TPA and MEG molecules and / or "degradation products" of BHET via hydrolysis reaction. As mentioned, the BHET used is usually a recycled BHET, e.g. obtained from recycling of PET by depolymerization, and depending on the quality of the recycled BHET, the quantity and type of side products may vary. If pure BHET is schematically denoted as MEG-TPA-MEG (chain length = 1), examples of esterification products may be denoted e.g. MEG- TPA-MEG-TPA or MEG-TPA-MEG-TPA-MEG or TPA-MEG-TPA-MEG-TPA-MEG. Examples of degradation products may be denoted e.g. TPA-MEG or MEG. In general, the BHET used may have an average chain length of 0.7 to 2 or 1 to 2, preferably 0.8 to 1.5 or 1 to 1.5, more preferably 0.8 to 1.3 or 1 to 1.3. It should be noted that such possible esterification products or degradation products in BHET are included in following indications related to the amount of BHET used, unless explicitly stated otherwise.

[0074] BHET is the main component in reactant material B). The weight of BHET in reactant material B) is e.g. at least 90% by weight, preferably at least 95% by weight, based on the total weight of the reactant material B).

[0075] Reactant material B) may optionally further comprise one or more additives. Such additives may be the common additives used in this technical field. Examples for the additives may be e.g. colouring agents, e.g. blue toner and / or red toner, and heat stabilizers.

[0076] The reactant material C) comprises isophthalic acid (IPA), wherein the reactant material C) is preferably in form of a paste (IPA paste).

[0077] The reactant material C) is preferably in form of a paste (IPA paste). It is generally preferred to prepare the reactant material C), usually in form of a paste, in a mixing vessel, preferably a paste preparation vessel.

[0078] The weight of IPA in reactant material C) is e.g. at least 9% by weight, preferably at least 44% by weight, based on the total weight of the reactant material C). M / EPC-105-PC

[0079] 12

[0080] In a preferred embodiment, reactant material C) comprises ethylene glycol (MEG) and / or diethylene glycol (DEG), preferably MEG and DEG. In a further preferred embodiment, reactant material C) comprises at least one polycondensation catalyst. In particularly preferred embodiments, apart from IPA, reactant material C) comprises MEG and / or DEG, preferably MEG and DEG, and at least one polycondensation catalyst. The addition of DEG and / or MEG is suitable to prepare reactant material C) in form of a paste (IPA paste).

[0081] The feed mass ratio of IPA to BHET is in the range of 0.0015 to 0.04, preferably 0.004 to 0.02, more preferably 0.007 to 0.016.

[0082] If monoethylene glycol (MEG) and / or diethylene glycol (DEG) are contained in reactant material C), the amount of MEG and / or DEG is e.g . 25 to 90 wt.%, preferably 30 to 55 wt.%, based on the weight of reactant material C). In a preferred embodiment, DEG or DEG and MEG are contained in reactant material C).

[0083] For instance, the amount of MEG may be in the range of 0 to 40 wt.%, preferably 1 to 20 wt.%, based on the weight of reactant material C). The amount of DEG, if present in reactant material C), may be in the range of 5 to 90 wt.%, preferably 15 to 55 wt.%, based on the weight of reactant material C).

[0084] Reactant material C) may optionally further comprise one or more additives. Such additives may be the common additives used in this technical field. Examples for the additives may be e.g. colouring agents, e.g. blue toner and / or red toner, and heat stabilizers.

[0085] The weight ratio of BHET to water (BHET : water) in the mixture of the reactant material B), water and reactant material C) in step i-c) may be e.g. in the range of 100-140 : 1, preferably 110-130 : 1, more preferably 115-125 : 1.

[0086] The amount of isophthalic acid (IPA) in the mixture of the reactant material B), water and the reactant material C) may be e.g. 0.1 to 5 wt.%, preferably 0.5 to 2.5 wt.%, based on the total weight of the mixture of the reactant material B), water and the reactant material C). M / EPC-105-PC

[0087] 13

[0088] In a preferred embodiment, the water used in step i-c) is at least in part recycled water removed as a byproduct of esterification reaction in step ii-c).

[0089] Typically, the pre-polycondensing and final polycondensing steps (steps iii-c) and iv-c) are carried out in the presence of at least one polycondensation catalyst or a reaction product thereof. The at least one polycondensation catalyst may be one polycondensation catalyst or a combination of two or more polycondensation catalysts.

[0090] Any polycondensation catalyst known by the skilled person for the polycondensation reaction in PET production can be used. The at least one polycondensation catalyst comprises or is e.g. a germanium compound, a titanium compound, a cobalt compound, e.g. cobalt acetate, or a combination thereof. The at least one polycondensation catalyst comprises or is preferably an antimony compound, wherein the antimony compound is preferably selected from antimony acetate, antimony (III) oxide, antimony glycolate or a combination thereof.

[0091] It is sufficient that the at least one polycondensation catalyst is added to a reactant material or any suitable reactor or a reaction material stream so that the pre-polycondensing and final polycondensing steps are carried out in the presence of the at least one polycondensation catalyst or a reaction product thereof. As discussed above, it is generally preferred that the at least one polycondensation catalyst is included in the reactant material C).

[0092] The at least one polycondensation catalyst can be suitable added in form of a solution or dispersion in a solvent such as glycol and continuously metered into a a suitable reaction material stream or preferably into reactant material C).

[0093] It is generally preferred that the BHET used in the inventive process is recycled BHET, preferably obtained from a chemical recycling of PET waste. The BHET is contained in reactant material B). As mentioned before, BHET can be obtained by recycling of PET waste, in particular by depolymerization of PET waste. PET products based on recycled BHET are termed rPET. In a preferred embodiment, the PET produced is rPET. M / EPC-105-PC

[0094] 14

[0095] In preferred embodiments, DEG and at least one polycondensation catalyst are added as additional components, wherein these additional components are preferably contained in the reactant material C). The presence of IPA contained in reactant material C) is suitable to obtain a PET of high optical quality, in particular a PET of bottle grade quality.

[0096] In the inventive process, the second group of at least one reactor, the first group of at least one reactor, the third group of at least one reactor, and the final reactor are connected in series in this order. When a group of at least one reactor comprises two or more reactors, these two or more reactors are also arranged in series. The respective reactant material or reaction material stream enters the first reactor of such group and is subsequently fed to the subsequent reactor(s) of the group and leaves from the last reactor of the group. The same applies mutatis mutandis for reactor stages instead of reactors, when the group includes two or more reactor stages.

[0097] The inventive process comprises the following steps: i-c) subjecting a mixture of the reactant material B), water and the reactant material C) to a hydrolysis reaction in the second group of at least one reactor to form a fully or partially hydrolysed reaction material stream; ii-c) subjecting the fully or partially hydrolysed reaction material stream to further reaction in the first group of at least one reactor including esterification reaction to form a reaction material stream C); iii-c) pre-polycondensing of the reaction material stream C) in the third group of at least one reactor to form a pre-polycondensed reaction material stream; and iv-c) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET.

[0098] In step i-c), a mixture of the reactant material B), water and the reactant material C) is formed in or preferably fed to the single or first reactor of the second group of at least one reactor, wherein the mixture is subjected to a hydrolysis reaction. Depending e.g. on the water amount, the hydrolysis reaction can form a fully or partially hydrolysed reaction material stream, but in general it is preferred to form a partially hydrolysed reaction material stream. In a preferred embodiment, the amount of water is generally substoichometric with respect to the hydrolysis reaction of BHET (BHET + 2 H2O TPA + 2 MEG) so M / EPC-105-PC

[0099] 15 that there is only partial hydrolysis of BHET. Preferably, the molar amount of water is less than 1 mol water per 1 mol BHET in the mixture. If the second group of at least one reactor comprises more than one reactor, the fully or partially hydrolysed reaction material stream obtained in the first reactor is fed to the subsequent reactor(s) in series of the second group to continue hydrolysis. The fully or partially hydrolysed reaction material stream formed in the single or last reactor of the second group is fed to the first group of at least one reactor. As mentioned, the second group of at least one reactor preferably comprises or consists of one reactor.

[0100] In step ii-c) of operating mode c) the fully or partially hydrolysed reaction material stream obtained from step i-c) is subjected to further reaction in the first group of at least one reactor including esterification to form a reaction material stream C).

[0101] In this regard, the fully or partially hydrolysed reaction material stream obtained from step i-c) is fed to the first reactor of the first group of at least one reactor, where the further reaction takes place. If the first group of at least reactor comprises more than one reactor, the reaction material stream obtained in the first reactor is fed to the subsequent reactor(s) of the first group of at least one reactor in series to continue further reaction. As mentioned, the first group of at least one reactor preferably comprises or consists of one reactor.

[0102] The reaction material stream C) formed in step ii-c) is fed from the single or last reactor of the first group of at least reactor to the single or first reactor of the third group of at least one reactor.

[0103] In step iii-c), the reaction material stream C) formed in step ii-c) is prepolycondensed in the third group of at least one reactor to form a prepolycondensed reaction material stream. In step iv-c) of operating mode c), final polycondensing of the pre-polycondensed reaction material stream is effected in the final reactor to form PET.

[0104] In step iii-c), the reaction material stream C) formed in step ii-c) is fed to the third group of at least one reactor, wherein the reaction material stream C) is subjected to pre-polycondensation reaction to form a pre-polycondensed reaction material stream. Specifically, the reaction material stream C) formed in step ii-c) M / EPC-105-PC

[0105] 16 is fed to the single or first reactor of the third group of at least one reactor, wherein it is subjected to a pre-polycondensation reaction. If the third group of at least one reactor comprises two or more reactors, the pre-polycondensed reaction material stream obtained from the first reactor of the third group is fed to the subsequent reactor(s) of the third group, wherein the prepolycondensation reaction is continued. The formed pre-polycondensed reaction material stream is fed from the single or last reactor of the third group of at least one reactor to the final reactor. As mentioned, the third group of at least one reactor preferably comprises or consist of one, two or three reactors, preferably one or two reactors, more preferably two reactors.

[0106] In step iv-c) of operating mode c), the polycondensed reaction material stream fed from the single or last reactor of the third group of at least one reactor is subjected to final polycondensing in the final reactor to form PET.

[0107] In the following suitable and preferred operation conditions for the reactions in each of the groups of reactors are indicated .

[0108] Thus, the reactor(s) of the first group of at least one reactor are each independently operated e.g. at a temperature in a range of 250 to 280 °C and a pressure of 1.0 to 3.5 bar(a), preferably at a temperature in a range of 255 to 275 °C, and a pressure of 1.05 to 3.3 bar(a). In a particularly preferred embodiment, the temperature is in a range of 258 to 270 °C and the pressure is in a range of 1.1 to 3.0 bar(a).

[0109] The reactor(s) of the second group of at least one reactor are each independently operated e.g. at a temperature in a range of 250 to 280 °C and a pressure of 1.0 to 3.0 bar(a), preferably at a temperature in a range of 255 to 270 °C, and a pressure of 1.2 to 2.5 bar(a). In a particularly preferred embodiment, the temperature is in a range of 259 to 265 °C, and a pressure of 1.3 to 1.8 bar (a).

[0110] The reactor(s) of the third group of at least one reactor are e.g. each independently operated at a temperature in a range of 260 to 290 °C and a pressure of 5 to 300 mbar(a), preferably at a temperature in a range of 265 to 285 °C and a pressure of 10 to 250 mbar(a). In a particularly preferred embodiment, the temperature is in a range of 268 to 280 °C and the pressure is in a range of 15 to 200 mbar(a). M / EPC-105-PC

[0111] 17

[0112] If the third group of at least one reactor includes two or more reactors, preferably two reactors, the first reactor of the third group is preferably operated at a pressure of 100 mbar(a) to 300 mbar(a), preferably 120 to 250 mbar(a), and the last reactor of the third group is preferably operated at a pressure of 5 to 60 mbar(a), preferably 10 to 40 mbar(a), wherein the temperature ranges given above equally apply.

[0113] The final reactor is operated e.g. at a temperature in a range of 270 to 300 °C and a pressure of 0.2 to 3 mbar(a), preferably at a temperature in a range of 275 to 290 °C, and a pressure of 0.5 to 2 mbar(a), such as about 1 mbar(a). In a particularly preferred embodiment, the temperature is in a range of 280 to 288 °C and the pressure is in a range of 0.7 to 1.5 mbar(a). The suitable / preferred process parameter ranges for the reactors in operation are summarized in the following table, wherein also particular preferred ranges are indicated. The indication in parenthesis in the head column refer to the illustrative reactors as designated in the figures discussed below. M / EPC-105-PC

[0114] 18

[0115] 1the first group of at least one reactor, e.g. ES2.

[0116] 2the second group of at least one reactor, e.g. ESI.5.

[0117] 3the third group of at least one reactor, e.g. PPI and PP2.

[0118] 4the final reactor, e.g. FIN.

[0119] In a preferred embodiment, with respect to the reactors connected in series the temperature in each reactor is equal to or higher than in the previous reactor, and / or the pressure in each reactor is equal to or lower than in the previous reactor.

[0120] In the reaction material stream C) formed in step ii-c) the carboxylic groups contained therein are preferably esterified to a large degree but not completely so that the reaction material still includes free carboxyl end groups.

[0121] The esterification conversion degree refers to the amount of carboxylic groups in the respective reaction material stream, which are esterified, based on the total amount of carboxylic groups present in the reaction material stream in free or esterified form. The carboxyl groups may be part of a monomer or of an oligomer formed during esterification reaction. For instance, an esterification conversion degree of 80% means that 80% of all carboxyl groups are esterified and 20% of all carboxyl groups are in free form (not esterified).

[0122] Thus, in a particular preferred embodiment of the inventive process, the reaction material stream C) formed in step ii-c) of operating mode c) has an esterification conversion rate of 94 to 99%, preferably 95 to 97%, more preferably 95.5 to 96.5%, so that the reaction material still includes carboxyl end groups (not esterified carboxyl end groups).

[0123] This limited rate of esterification in reaction material stream C), respectively, allows for a desired number of carboxyl end groups that are still free, which has M / EPC-105-PC

[0124] 19 an accelerating effect on the further reaction rate of the polycondensation reaction.

[0125] In general, the feeding rate by weight of reactant material B) to the total weight of reactant material C) and water (B:(C+H2O)) may be typically in the range of 2.5: 1 to 35: 1, preferably 4: 1 to 25: 1, more preferably 6: 1 to 20: 1.

[0126] Feeding lines are generally provided between the reactors to connect them and to feed a reaction material stream from one reactor to the subsequent reactor.

[0127] It is generally preferred that each reactor of the first group of at least one reactor, the second group of at least one reactor, the third group of at least one reactor and the final reactor is provided with means for removing volatile byproducts. The means for removing volatile by-products from the reactors of the reactors of the first group and the second group are preferably common or separate process columns. The means for removing volatile by-products of the reactor(s) of the third group and the final reactor are preferably common or separate vacuum condenser systems.

[0128] Thus, volatile by-products from the reaction or other components are typically removed from each of the reactors at least in part. The volatile by-products or components removed from the first group of at least one reactor and the second group of at least one reactor generally comprises water and MEG. The volatile byproducts or components removed from the third group of at least one reactor and the final reactor generally comprises MEG and optionally water.

[0129] In the following, main reactions which take place during a conventional process for PET production based on PTA and MEG are discussed. The conventional PET production generally comprises esterification and polycondensation reaction. The esterification takes place in a group of at least one reactor including at least two reactor stages. The esterification reaction will be processed in at least two stages, preferably in two stages, e.g. in a reactor including two reactor stages also called reaction spaces or in two reactors each including a reactor stage.

[0130] During the esterification of TPA and MEG, the following three main reactions (I), (II) and (III) will take place. These three main reactions (I), (II) and (III) apply at defined reaction conditions. An additional amount of ethylene glycol above M / EPC-105-PC

[0131] 20 stoichiometric requirements is preferably used to accelerate the reaction rate and achieve the reaction equilibrium phase.

[0132] (I) Formation of glycol terephthalate (esterification) Ethylene glycol (MEG) and terephthalic acid (TPA) will react together, forming glycol-terephthalate (GT) i.e. the ester group, and water. This is illustrated in the following reaction schemes. It should be noted that one of the reaction products formed is BHET.

[0133] (II) Processing of chain length (poly-esterification)

[0134] Glycol terephthalate molecules start to react with each other, i.e. the polycondensation process will be initiated and progressed in esterification stages. The condensation degree may e.g. be up to an average chain length of approximate n

[0135] = 4-5 repeating units in esterification section. The polycondensation split-glycol may split-off or react as a 'new raw material partner' within the esterification product mixture. This is illustrated in the following reaction scheme for a formation of condensation product with chain length of 2 as an example. M / EPC-105-PC

[0136] 21

[0137] (Ill) Formation of di-ethylene glycol (DEG)

[0138] The ethylene glycol does not only react with terephthalic acid, but also with each other forming DEG, wherein water is formed and split-off. This is illustrated in the following reaction scheme

[0139] Thus, in the esterification reaction carried out in at least two stages, preferably two stages, a high esterification conversion rate can be achieved.

[0140] In the subsequent pre-polycondensation and final polycondensation reaction in a further group of at least one reactor and a final reactor, the esterification reaction will be continued. That ongoing esterification reaction via carboxylic end groups (-COOH) even provides qualitative advantages along the whole polycondensation process.

[0141] A reaction product (byproduct) of the esterification reaction is water vapor, which, due to the chemical-physical equilibrium, is removed via means for volatile byproducts such as a distillation column together with MEG vapors for separation.

[0142] In the inventive process, BHET is used as starting material replacing MEG and TPA as starting materials of conventional production. The BHET mixed with water is subjected to hydrolysis reaction in the second group of at least one reactor. M / EPC-105-PC

[0143] 22

[0144] Due to hydrolysis reaction, part of the BHET is hydrolysed generating monoester of TPA and / or TPA as well as MEG. Generally, a part of BHET is not hydrolysed. As mentioned before, BHET as well as monoester of TPA are also reaction products in the esterification reaction in conventional PET production based on TPA and MEG. Thus, components present in the esterification reaction of conventional PET production based on TPA and MEG can be also present in the inventive process where BHET is fully or partially hydrolysed in the second group of at least one reactor and subjected to further reaction including esterification in the first group of at least one reactor. As a result, the reaction material stream C) obtained in step ii-c) of the invention can be similar in composition to the reaction material obtained in the (two-stage) esterification in the conventional PET production based on TPA and MEG.

[0145] The reaction material stream C) obtained in step ii-c) is then fed continuously from the single or last reactor of the first group of at least one reactor to the subsequent pre-polycondensation in the third group of at least one reactor and the final reactor.

[0146] In the inventive process, the second stage of the reaction progresses under a defined vacuum and temperature, first in the pre-polycondensation step, followed by the final polycondensation step, in which monomer or oligomer molecules continue to connect and lengthen, releasing ethylene glycol and water (residual esterification). In order to ensure the reaction rate during the prepolycondensation process and final polycondensation process, it is usually necessary to add a condensation catalyst at a proper time.

[0147] The polycondensation reaction is preferably carried out in two or three stages, one or two pre-polycondensation stages and at the end the final polycondensation.

[0148] The glycol released by chain growth and optionally water is removed from the reactor(s) of the third group and the final reactor using a means for removing volatile byproducts, which is preferably a vacuum system comprising a vapor condensation stage, vacuum jet system and vacuum pumps.

[0149] The final polycondensation typically takes place in an agitated horizontal reactor, in particular a horizontal reactor equipped with agitator made up of multiple M / EPC-105-PC

[0150] 23 types of disks. In the final reactor, the pre-polycondensed mass is subjected to high temperature and low pressure throughout the process. Due to these extreme conditions, the molecular growth reaction is greatly accelerated, resulting in a linear PET polymer with high molecular weight and high viscosity.

[0151] The PET formed in the final reactor can be subjected to further refinement. Thus, the inventive process may comprise the following further steps: processing the PET material stream withdrawn from the final reactor to prepare a solid PET material, preferably in form of PET chips, increasing the intrinsic viscosity of the solid PET material, preferably PET chips, by subjecting it to a solid state polycondensation, wherein the solid PET material with increased intrinsic viscosity, preferably in chip form, is preferably bottle grade PET.

[0152] With respect to processing the PET material stream withdrawn from the final reactor to prepare a solid PET material, preferably in form of PET chips, granulating systems with e.g. continuous casting heads and a chips-water circulation and cooling system for transport and solidification may be used. The strands formed are e.g. cut to the desired size, cooled and dried. They can then be separated from oversized particles using a conventional vibrating conveyor screen.

[0153] In a further process sequence, the solid PET material, preferably PET chips, can be transferred to a solid state polycondensation (SSP). There - based on the residence time, process gas (N2) quality and temperature - the required increase up to the desired limiting viscosity (intrinsic viscosity) takes place. The acetaldehyde trapped in the structure of the PET chips is also diffused out along the SSP process along with the reaction products, cracked glycol and process water.

[0154] The finished PET chips can be fed to the packaging station via silos and silo mixing plants, where they are filled and stored.

[0155] The invention is also directed to a plant for continuous production of polyethylene terephthalate (PET), preferably rPET, comprising a first group of at least one reactor, a second group of at least one reactor, a third group of at least one M / EPC-105-PC

[0156] 24 reactor, and a final reactor, which reactors are configured to carry out the inventive process as described above.

[0157] The entire disclosure related to the inventive process including disclosure with respect to the configuration of the plant equally applies to the inventive plant so that reference is made thereto. The following disclosure with respect to the inventive plant equally applies to the inventive process.

[0158] In a preferred embodiment of the inventive plant, the first group of at least one reactor comprises or consists of one or two reactors, preferably one reactor; the second group of at least one reactor comprises or consists of one reactor, and / or the third group of at least one reactor comprises or consists of one, two or three reactors, preferably one or two reactors, more preferably two reactors.

[0159] In a preferred embodiment, the inventive plant further comprises

[0160] - a melting device for melting BHET to which water and optionally one or more polycondensation catalysts and / or additives can be admixed in the melting device and / or thereafter;

[0161] - transporting means for feeding reactant material B), water and reactant material C) to the first reactor of the second group of at least one reactor; and

[0162] - a paste preparation vessel for mixing IPA and at least one of MEG and DEG and optionally the at least one polycondensation catalyst and / or additives to obtain reactant material C) in form of a paste (IPA paste).

[0163] The invention in all its aspects is further described in the following drawing related to a specific embodiment of the invention, which however is in no way intended to limit the scope of the invention. The accompanying drawing shows in:

[0164] Fig. 1 a block flow diagram for an exemplary and preferred embodiment of the inventive process for continuous production of PET

[0165] In Fig. 1, a preferred embodiment is shown, wherein the first group of at least one reactor consists of one reactor (ES2), the second group of at least one reactor consists of one reactor (ESI.5), and the third group of at least one M / EPC-105-PC

[0166] 25 reactor consists of two reactors (PPI and PP2), but the number of reactors for each group is not limited thereto and may vary.

[0167] Fig. 1 shows a block flow diagram for an exemplary and preferred embodiment of the inventive process for continuous production of PET, wherein a single reactor of the second group of at least one reactor (ESI.5), a single reactor of the first group of at least one reactor (ES2), a first reactor of the third group of at least one reactor (PPI), a second reactor of the third group of at least one reactor (ES2) and a final reactor (FIN) are connected in series in this order.

[0168] According to Fig. 1, a reactant material B) is prepared by melting BHET in a melting device (BHET Melt). A reactant material C) in form of an IPA paste comprising isophthalic acid (IPA) is prepared in a paste preparation vessel. In a preferred embodiment, at least one of ethylene glycol (MEG) and diethylene glycol (DEG) as well as at least one polycondensation catalyst (Catalysts) and optionally one or more additives are also added to the IPA paste.

[0169] The melted BHET (reactant material B) is combined with water and the IPA paste (reactant material C) and the mixture is fed to reactor ESI.5, wherein it is subjected to a hydrolysis reaction to form a fully or partially hydrolysed reaction material stream, preferably a partially hydrolysed reaction material stream, in reactor ESI.5. The fully or partially hydrolysed reaction material stream is fed to reactor ES2, wherein it is subjected to further reaction including esterification reaction to obtain a reaction material C) leaving reactor ES2.

[0170] The resulting reaction material stream C) is fed from ES2 to the first reactor of the third group (PPI) and subsequently to the second reactor of the third group (PP2), wherein the reaction material stream A) is pre-polycondensed in reactors PPI and PP2. The pre-polycondensed reaction material stream formed is fed from PP2 to the final reactor (FIN) wherein final polycondensing of the prepolycondensed reaction material stream is effected to form PET leaving the reactor in form of a melt.

[0171] The reactors ESI.5, ES2, and PPI are preferably vertical stirred-tank reactors. The reactors PP2 and FIN are preferably horizontal reactor(s), preferably horizontal agitated reactor equipped with an agitator made up of multiple types of disks. Each of the reactors can be operated with the operating conditions M / EPC-105-PC

[0172] 26 described above. In general, volatiles are removed from ESI.5 and ES2, and further processed, e.g. in a common process column. The reactors PPI, PP2 and FIN may be connected with a vacuum condenser system to remove volatiles from the reaction material stream. List of reference signs

[0173] ES2 single reactor of first group of at least one reactor

[0174] ESI.5 single reactor of second group of at least one reactor

[0175] PPI first reactor of third group of at least one reactor

[0176] PP2 second reactor of third group of at least one reactor FIN final reactor

Claims

M / EPC-105-PC27Claims1. A process for continuous production of polyethylene terephthalate (PET), preferably recycled PET (rPET), in a plant comprising a first group of at least one reactor, a second group of at least one reactor, a third group of at least one reactor, and a final reactor, wherein the following reactant materials are used: a reactant material B) comprising melted bis(2-hydroxyethyl) terephthalate (BHET); a reactant material C) comprising isophthalic acid (IPA), wherein the reactant material C) is preferably in form of a paste (IPA paste); wherein the second group of at least one reactor, the first group of at least one reactor, the third group of at least one reactor, and the final reactor are connected in series in this order, wherein the process comprises i-c) subjecting a mixture of the reactant material B), water and the reactant material C) to a hydrolysis reaction in the second group of at least one reactor to form a fully or partially hydrolysed reaction material stream; ii-c) subjecting the fully or partially hydrolysed reaction material stream to further reaction in the first group of at least one reactor including esterification reaction to form a reaction material stream C); iii-c) pre-polycondensing of the reaction material stream C) in the third group of at least one reactor to form a pre-polycondensed reaction material stream; and iv-c) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET.

2. The process according to claim 1, wherein the water used in step i-c) is at least in part recycled water removed as a byproduct of esterification reaction in step ii-c).M / EPC-105-PC283. The process according to any one of the preceding claims, wherein the pre- polycondensing and final polycondensing steps are carried out in the presence of at least one polycondensation catalyst or a reaction product thereof, wherein the at least one polycondensation catalyst preferably comprises or is an antimony compound, wherein the antimony compound is preferably selected from antimony acetate, antimony (III) oxide, antimony glycolate or a combination thereof.

4. The process according to any one of the preceding claims, wherein the reactor(s) of the first group of at least one reactor are each independently operated at a temperature in a range of 250 to 280 °C and a pressure of 1.0 to 3.5 bar(a), preferably at a temperature in a range of 255 to 275 °C, and a pressure of 1.05 to 3.3 bar(a), and / or the reactor(s) of the third group of at least one reactor are each independently operated at a temperature in a range of 260 to 290 °C and a pressure of 5 to 300 mbar(a), preferably at a temperature in a range of 265 to 285 °C and a pressure of 10 to 250 mbar(a); and / or the final reactor is operated at a temperature in a range of 270 to 300 °C and a pressure of 0.2 to 3 mbar(a), preferably at a temperature in a range of 275 to 290 °C, and a pressure of 0.5 to 2 mbar(a), such as about 1 mbar(a).

5. The process according to any one of the preceding claims, wherein the reactor(s) of the second group of at least one reactor are each independently operated at a temperature in a range of 250 to 280 °C and a pressure of 1.0 to 3.0 bar(a), preferably at a temperature in a range of 255 to 270 °C, and a pressure of 1.2 to 2.5 bar(a).

6. The process according to any one of the preceding claims, wherein with respect to the reactors connected in series the temperature in each reactor is equal to or higher than in the previous reactor, and / or the pressure in each reactor is equal to or lower than in the previous reactor.

7. The process according to any one of the preceding claims, wherein the amount of isophthalic acid (IPA) in the mixture of the reactant material B), water and the reactant material C) is 0.1 to 5 wt.%, preferably 0.5 to 2.5M / EPC-105-PC29 wt.%, based on the total weight of the mixture of the reactant material B), water and the reactant material C).

8. The process according to any one of the preceding claims, wherein the reactant material C) is in form of a paste (IPA paste) comprising isophthalic acid (IPA) and at least one of ethylene glycol (MEG) and / or diethylene glycol (DEG) and optionally the at least one polycondensation catalyst, wherein the amount of MEG and / or DEG is preferably 25 to 90 wt.%, more preferably 30 to 55 wt.%, based on the weight of reactant material C), and / or wherein the feed mass ratio of IPA to BHET is in the range of 0.0015 to 0.04, preferably 0.004 to 0.02, more preferably 0.007 to 0.016.

9. The process according to any one of the preceding claims, wherein the weight ratio of BHET to water (BHET : water) in the mixture of the reactant material B), water and reactant material C) in step i-c) is in the range of 100-140 : 1, preferably 110-130 : 1, more preferably 115-125 : 1.

10. The process according to any one of the preceding claims, wherein the reaction material stream C) formed in step ii-c) has an esterification conversion rate of 94 to 99%, preferably 95 to 97%, more preferably 95.5 to 96.5%, so that the reaction material still includes carboxyl end groups.

11. The process according to any one of the preceding claims, wherein the BHET used in the process is recycled BHET, preferably obtained from a chemical recycling of PET waste.

12. The process according to any one of the preceding claims, wherein the feeding rate by weight of reactant material B) to the total weight of reactant material C) and water (B:(C+H2O)) is in the range of 2.5: 1 to 35: 1, preferably 4.1 to 25: 1, more preferably 6: 1 to 20: 1.

13. The process according to any one of the preceding claims, wherein each reactor of the first group of at least one reactor, the second group of at least one reactor, the third group of at least one reactor and the final reactor is provided with means for removing volatile by-products,M / EPC-105-PC30 wherein the means for removing volatile by-products from the reactors of the reactors of the first group and the second group are preferably common or separate process columns, and / or wherein the means for removing volatile by-products of the reactor(s) of the third group and the final reactor are preferably common or separate vacuum condenser systems.

14. The process according to any one of the preceding claims, further comprising the following steps: processing the PET material stream withdrawn from the final reactor to prepare a solid PET material, preferably in form of PET chips, increasing the intrinsic viscosity of the solid PET material, preferably PET chips, by subjecting it to a solid state polycondensation, wherein the solid PET material with increased intrinsic viscosity, preferably in chip form, is preferably bottle grade PET.

15. A plant for continuous production of polyethylene terephthalate (PET), preferably recycled PET, comprising a first group of at least one reactor, a second group of at least one reactor, a third group of at least one reactor, and a final reactor, which reactors are configured to carry out a process according to any one of claims 1 to 14.

16. The plant of claim 15, wherein the first group of at least one reactor consists of one or two reactors, preferably one reactor; the second group of at least one reactor consists of one reactor, the third group of at least one reactor consists of one, two or three reactors, preferably one or two reactors, more preferably two reactors.

17. The plant of claim 15 or claim 16, further comprising- a melting device for melting BHET to which water and optionally one or more polycondensation catalysts and / or additives can be admixed in the melting device and / or thereafter;- transporting means for feeding reactant material B), water and reactant material C) to the first reactor of the second group of at least one reactor; andM / EPC-105-PC31- a paste preparation vessel for mixing IPA and at least one of MEG and DEG and optionally the at least one polycondensation catalyst and / or additives to obtain reactant material C) in form of a paste (IPA paste).

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