Variable 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 variable continuous production of polyethylene terephthalate (PET), preferably recycled PET (rPET), in a plant comprising a plurality of reactors, wherein the process can switch between three operating modes a), b) and c) or can switch between operating modes a) and b) or is according to operating mode b), wherein depending of the operating mode one or more of the following reactant materials are used: a reactant material A) comprising terephthalic acid (TPA) and ethylene glycol (MEG), 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 IPA paste.

Description

[0001] EPC Engineering & Technologies GmbH October 11, 2024 M / EPC-096-PC Meissner Bolte Partnerschaft mbB

[0002] Variable 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 variable continuous production of polyethylene terephthalate (PET), preferably recycled PET (rPET), in a plant comprising a plurality of reactors, wherein the process can switch between three operating modes a), b) and c) or can switch between operating modes a) and b) or is according to operating mode b), wherein depending of the operating mode one or more of the following reactant materials are used : a reactant material A) comprising terephthalic acid (TPA) and ethylene glycol (MEG), a reactant material B) comprising melted bis(2-hydroxyethyl) terephthalate (BHET); and a reactant material C) comprising isophthalic acid (IPA).

[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 M / EPC-096-PC

[0009] 2 final polycondensation unit with process steam condensation system

[0010] • Individual polymer distribution with polymer filter for chip production

[0011] • PET chips production with melt strand casting head, strand guiding device and water-cooling section, granulating unit, drying and screening

[0012] • Solid state polycondensation (SSP) to increase the desired limiting viscosity (intrinsic viscosity) and to diffuse the acetaldehyde content

[0013] • Intermediate storage in silos, quality control and bagging, e.g. in big bags

[0014] In the multi-stage continuous PET process, 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.

[0015] 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.

[0016] 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.

[0017] 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). M / EPC-096-PC

[0018] 3

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

[0020] 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).

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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 M / EPC-096-PC

[0025] 4 structure of the PET chips is also diffused out along the SSP process along with the reaction products, cracked glycol and process water.

[0026] The finished PET chips are fed to the packaging station via silos and silo mixing plants, where they are filled and stored.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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. Specifically, an object of the present invention was to provide a variable process for production of polyethylene terephthalate (PET), preferably at least in part a rPET, wherein, depending on the availability of suitable recycling material, the process can switch between modes in which the PET is prepared from fresh raw material or recycled raw material or a combination of fresh and recycled material, wherein in all modes a high quality PET can be obtained. In addition, the productivity of the PET production plant M / EPC-096-PC

[0031] 5 should be high, in particular it should not be significantly reduced with respect to a conventional PET production plant based on TPA and MEG only.

[0032] The inventors have found that this object can be solved by a modified process for the production of PET in which classic esterification of PET using the raw materials TPA and EG can be replaced with the partial or complete addition of bis(2-hydroxyethyl terephthalate) (BHET). BHET can be obtained by chemical recycling of PET waste, in particular it is a depolymerized PET waste, and hence a recycled material. The end product is then so-called recycled PET (rPET).

[0033] 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 first group of at least one reactor includes at least two reactor stages, wherein the process can switch between three operating modes a), b) and c) or can switch between operating modes a) and b) or is according to operating mode b), wherein depending on the operating mode one or more of the following reactant materials are used: a reactant material A) comprising terephthalic acid (TPA) and ethylene glycol (MEG); 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 in operating mode a) and operating mode b) 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 in operating mode a) the second group of at least one reactor is not operated, wherein in operating mode c) a first part of the first group of at least one reactor including the first reactor stage of the at least two reactor stages is not operated, M / EPC-096-PC

[0034] 6 whereas a remaining second part of the first group of at least one reactor including the last reactor stage of the at least two reactor stages is operated, and the second group of at least one reactor, the remaining second part of 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 operating mode a) comprises i-a) subjecting the reactant material A) to an esterification reaction in the first group of at least one reactor to form a reaction material stream A), wherein the esterification reaction is carried out in at least two reaction stages; ii-a) pre-polycondensing of the reaction material stream A) in the third group of at least one reactor to form a pre-polycondensed reaction material stream; and iii-a) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET; wherein the operating mode b) comprises i-b) subjecting a mixture of the reactant material B) and water 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-b) subjecting the reactant material A) to an esterification reaction in the first group of at least one reactor, wherein the esterification reaction is carried out in at least two reaction stages and wherein the fully or partially hydrolysed reaction material stream obtained in step i-b) is mixed into a reaction material stream obtained after the first reaction stage of step ii-b) and before and / or in the last reaction stage of step ii-b) and continuing esterification of the mixture to form a reaction material stream B); iii-b) pre-polycondensing of the reaction material stream B) in the third group of at least one reactor to form a pre-polycondensed reaction material stream; and iv-b) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET; wherein the operating mode c) comprises M / EPC-096-PC

[0035] 7 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 remaining second part of 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.

[0036] The inventive process enables the use of up to 100% of BHET. Since BHET is available as 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 preferably a rPET.

[0037] According to the present invention, the polyester reaction process and the associated plant technology is designed in such a way that existing PET production plants can also be converted or upgraded efficiently and quickly so that raw BHET can be used (partially or completely) as a replacement for the conventional production route with ethylene glycol (MEG) and terephthalic acid (TPA). It is a specific benefit of the inventive process, that it can be implemented in an existing conventional plant for the production of PET with moderate modifications only.

[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 optionally 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 that has M / EPC-096-PC

[0039] 8 physical and chemical properties that are almost comparable to those of conventional PET, preferably conventional PET suitable for bottle production.

[0040] 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.

[0041] The newly developed technology enables the use of up to 100% 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 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] Existing PET lines can be retrofitted or supplemented with the new technology of the inventive process with just a few new process units, while maintaining the required qualities of PET, e.g. for PET bottles in the beverage and food sector.

[0045] The technology of the inventive process can be used to expand the production capacity of PET at conventional PET plants without increasing the need for additional, conventional raw materials, i.e. TPA and EG. It can be also used for a plant conversion of a conventional PET plant to substitute the conventional raw M / EPC-096-PC

[0046] 9 materials TPA and EG. The technology described is also suitable for the construction of a new PET plant.

[0047] In the following, the invention is described in detail.

[0048] The inventive process is a process for variable continuous production of polyethylene terephthalate (PET) 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.

[0049] The first group of at least one reactor includes at least two reactor stages. At least two reactor stages enable to carry out the reaction, here the esterification reaction, in at least two reaction stages. Each reactor stage can be represented by a separate reactor. A reactor comprises at least one reactor stage and typically one reactor stage only. Alternatively or additionally, two or more reactor stages can be two or more compartments in a reactor, in which the reaction can be carried out separately in stages (a reaction stage in each compartment). It is generally preferred that each reactor used includes one or two reactor stages, preferably one reactor stage only.

[0050] In a preferred embodiment, the first group of at least one reactor including at least two reactor stages is a first group of at least two reactors. In each of the reactors, one reaction stage can be carried out.

[0051] In a preferred embodiment, the first group of at least one reactor comprises or consist of one reactor including two reactor stages, which are configured as two compartments in the reactor. In a more preferred embodiment, the first group of at least one reactor comprises or consists of two reactors, each representing a reactor stage.

[0052] In a preferred embodiment, the second group of at least one reactor comprises or consists of one reactor.

[0053] 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. M / EPC-096-PC

[0054] 10

[0055] In a particular preferred embodiment, the first group of at least one reactor comprises or consists of two reactors, 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.

[0056] 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.

[0057] 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.

[0058] The inventive process can switch between three operating modes a), b) and c) or can switch between operating modes a) and b) or is according to operating mode b). In each of operating modes a), b) and c), the inventive process is operated differently as described in detail below. Depending on the operating mode in operation, a part of the reactors may be not in operation. Thus, in operating mode a), the second group of at least one reactor is not in operation. In operating mode c), a first part of the first group of at least one reactor including the first reactor stage as explained below is not in operation. In operating mode b), all reactors specified are in operation. In each of operating modes a), b) and c), the inventive process is a continuous process.

[0059] In general, the inventive process is operated in operating mode b) and / or operating mode c) at least temporarily. That is, at least temporarily the process is switched into an operating mode wherein reactant material B) is used as a starting material. In general, the inventive process may be operated in operating mode b) at least temporarily. In general, the inventive process may be operated M / EPC-096-PC

[0060] 11 in operating mode c) at least temporarily. In principle, each of operating modes a), b) and c) can also be operated separately in a process where only operating mode a), operating mode b) or operating c) is carried out. For instance, a process according to operating b) can be carried out autonomously without reference to operating modes a) and c) and reactant material C). Likewise, a process according to operating c) can be carried out autonomously without reference to operating modes a) and b) and reactant material A).

[0061] The following statements apply for each of operating mode a), b) and c), if applicable and unless stated otherwise.

[0062] Depending on the operating mode, specific reactant materials are used as described below. Beforehand, some of the mandatory compounds or optional compounds used in such reactant materials are described in more detail.

[0063] Terephthalic acid, abbreviated as TPA, is a monomer used for the PET production. It has a molar mass of about 166.14 g / mol. TPA has the following chemical formula:

[0064] Ethylene glycol, abbreviated as MEG or EG is one monomer of the 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:

[0065] H H

[0066] HO- C - C -OH i T

[0067] H H

[0068] 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 M / EPC-096-PC

[0069] 12 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 62.07 g / mol. It has a molar mass of about 106.12 g / mol. DEG has the following chemical formula:

[0070] H H H H

[0071] HO— C — C — O— C — C — OH

[0072] H H H H

[0073] 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 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:

[0074] Bis-(2-hydroxyethyl) terephthalate, abbreviated as BHET, 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. BHET is the theoretical module for building the PET polymer chain. BHET has the following chemical formula: M / EPC-096-PC

[0075] 13

[0076] The structural formula will represent the ideal BHET molecule, thus in reality several length and end group modifications are possible.

[0077] Depending on the operating mode one or more of the following reactant materials are used. Thus, in general from the reactant materials A), B) and C) described below, reactant material A) is used in operating mode a), reactant material A) and reactant material B) are used in operating mode b), and reactant material B) and reactant material C) are used in operating mode c).

[0078] The reactant material A) comprises terephthalic acid (TPA) and ethylene glycol (MEG). The following statements regarding reactant material A) applies for both operating mode a) and operating mode b), unless stated otherwise.

[0079] In general, the reactant material A) is in form of a paste (TPA paste). It is generally preferred to prepare the reactant material A), usually in form of a paste, in a mixing vessel, preferably a paste preparation vessel, and feed the reactant material A) formed to the first reactor of the first group of at least one reactor in operating modes a) and b).

[0080] The molar ratio of MEG:TPA in reactant material A) is preferably in the range of 1.05 - 1.30 : 1, preferably 1.08 - 1.25 : 1, still more preferably 1.1 - 1.20 : 1.

[0081] TPA and MEG are the main components in reactant material A). The combined weight of TPA and MEG in reactant material A) is e.g. at least 80% by weight, preferably at least 85% by weight, based on the total weight of the reactant material A).

[0082] In a preferred embodiment, reactant material A) comprises diethylene glycol (DEG). In a further preferred embodiment, reactant material A) comprises at least one polycondensation catalyst. In a further embodiment, reactant material A) comprises isophthalic acid (IPA). The addition of IPA is suitable, if the PET produced shall be suitable for bottle production.

[0083] In particularly preferred embodiments, apart from MEG and TPA, reactant material A) comprises DEG and at least one polycondensation catalyst or comprises DEG, at least one polycondensation catalyst and IPA. M / EPC-096-PC

[0084] 14

[0085] This applies for both operating mode a) and b). With respect to operating mode b), one or more of the further optional components, namely DEG, the at least one polycondensation catalyst and IPA may be alternatively or additionally be contained in reactant material B), but incorporation thereof in reactant material B) is generally not preferred.

[0086] Reactant material A) 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.

[0087] If in operating mode a) the reactant material A) comprises diethylene glycol (DEG), the amount of DEG is preferably 0.1 to 2 wt.%, more preferably 0.2 to 1.5 wt.%, based on the total weight of reactant material A).

[0088] If in operating mode b) the reactant material A) and / or the reactant material B), preferably the reactant material A), comprises diethylene glycol (DEG), the amount of DEG is preferably 0.1 to 2.5 wt.%, more preferably 0.2 to 2.0 wt.%, based on the total weight of reactant material A) and reactant material B).

[0089] If in operating mode a) the reactant material A) comprises isophthalic acid (IPA), the amount of IPA is preferably 0.1 to 5 wt.%, more preferably 0.2 to 2 wt.%, based on the total weight of reactant material A).

[0090] If in operating mode b) the reactant material A) and / or the reactant material B), preferably the reactant material A), comprises isophthalic acid (IPA), the amount of IPA is preferably 0.1 to 4.5 wt.%, more preferably 0.2 to 1.8 wt.%, based on the total weight of reactant material A) and reactant material B).

[0091] The reactant material B) comprises melted bis(2-hydroxyethyl) terephthalate (BHET). The following statements regarding reactant material B) applies for both operating mode b) and operating mode c), unless stated otherwise.

[0092] 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 M / EPC-096-PC

[0093] 15 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.

[0094] 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.

[0095] The reactant material B) is in form of a melt. It is generally preferred to melt BHET in a melting device. In operating mode b), a mixture of reactant material B comprising melted BHET, and water is formed in the single or first reactor of the second group of at least one reactor or reactant material B) comprising melted BHET and water are mixed, and the mixture is fed to the first reactor of the second group of at least one reactor. In operating mode c), 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.

[0096] In a preferred embodiment for both of operating mode a) and b) the preparation of reactant material A) comprises feeding TPA and MEG into a paste preparation vessel to mix the raw materials to obtain a raw material mixture of PTA and MEG, wherein at least one of IPA and DEG, preferably DEG or DEG and IPA, and optionally the at least one polycondensation catalyst are preferably added to the paste preparation vessel. All components are preferably added to the paste preparation vessel via a separate line. As mentioned before, a preferred reactant material A) comprises DEG and at least one polycondensation catalyst or comprises DEG, at least one polycondensation catalyst and IPA.

[0097] 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). M / EPC-096-PC

[0098] 16

[0099] 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.

[0100] The reactant material C) comprises isophthalic acid (IPA), wherein the reactant material C) is preferably in form of a paste (IPA paste).

[0101] 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.

[0102] 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).

[0103] In a preferred embodiment, reactant material C) comprises monoethylene glycol (MEG) and / or diethylene glycol (DEG), preferably MEG and DEG. In a further preferred embodiment, reactant material A) 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).

[0104] The feed mass ratio of IPA to BHET with respect to operating mode c) is in the range of 0.0015 to 0.04, preferably 0.004 to 0.02, more preferably 0.007 to 0.016.

[0105] 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).

[0106] For instance, the amount of MEG may be in the range of 0 to 40 wt.%, preferably

[0107] 1 to 20 wt.%, based on the weight of reactant material C). The amount of DEG, if M / EPC-096-PC

[0108] 17 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).

[0109] 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.

[0110] The weight ratio of BHET to water (BHET : water) in the mixture of the reactant material B) and water in step i-b) of operating mode b) may be e.g. in the range of 100-140 : 1, preferably 110-130 : 1, more preferably 115-125 : 1.

[0111] 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) of operating mode c) may be e.g. in the range of 100-140 : 1, preferably 110-130 : 1, more preferably 115- 125 : 1.

[0112] In a preferred embodiment, the water used in step i-b) of operating mode b) is at least in part recycled water removed as a byproduct of esterification reaction in step ii-b) of operating mode b). In a preferred embodiment, the water used in step i-c) of operating mode c) is at least in part recycled water removed as a byproduct of esterification reaction in step ii-c) of operating mode c) and / or as a retained byproduct of esterification reaction in step ii-b) of operating mode b). With respect to the retained byproduct of esterification reaction in step ii-b) of operating mode b), this of course requires that operating mode b) was operated before switching to operating mode c).

[0113] In operating mode c) the amount of isophthalic acid (IPA) in the mixture of the reactant material B), water and the reactant material C) may be 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).

[0114] Typically, in each of operating mode a), b) and c) the pre-polycondensing and final polycondensing steps 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. The pre-polycondensing and final M / EPC-096-PC

[0115] 18 polycondensing steps of operating mode a) specifically refer to steps ii-a) and iii- a). The pre-polycondensing and final polycondensing steps of operating mode b) specifically refer to steps iii-b) and iv-b). The pre-polycondensing and final polycondensing steps of operating mode c) specifically refer to steps iii-c) and iv- c).

[0116] 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.

[0117] 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 at least one polycondensation catalyst or a reaction product thereof.

[0118] As discussed above, in operating mode a) and b) it is generally preferred that the reactant material A) comprises the at least one polycondensation catalyst. In operating mode c) it is generally preferred that the reactant material C) comprises the at least one polycondensation catalyst.

[0119] 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 reactant material, in particular the reactant material A) or the reactant material C), or optionally in a suitable reaction material stream.

[0120] It is generally preferred that the BHET used in operating mode b) and / or operating mode c) of the inventive process is recycled BHET, preferably obtained from a chemical recycling of PET waste. The BHET is generally 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-096-PC

[0121] 19

[0122] In preferred embodiments for each of operating modes a), b) and c), DEG and at least one polycondensation catalyst are added as additional components, wherein in operating modes a) and b), these additional components are preferably contained in the reactant material A) and in in operating mode c), these additional components are preferably contained in the reactant material C). In operating modes a) and b) a further additional component is preferably IPA, which is preferably contained in the reactant material A). The addition of IPA is particularly suitable, when a PET of high optical quality, in particular a PET of bottle grade quality, is to be produced. IPA is included in operating mode c) as a mandatory component.

[0123] In operating mode a) and operating mode b) of the inventive process, 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 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. In operating mode a), the second group of at least one reactor is not operated .

[0124] In operating mode b), the second group of at least reactor is configured parallel to at least the first reactor stage, preferably the first reactor, of the first group of at least one reactor. The hydrolysed reaction stream obtained in the second group of at least reactor is combined with an intermediate reaction stream of the first group of at least one reactor, namely to an intermediate reaction stream after the first reactor stage of the first group of at least one reactor and before and / or in, preferably before, the last reactor stage of the first group of at least one reactor.

[0125] In operating mode c) a first part of the first group of at least one reactor including the first reactor stage of the at least two reactor stages is not operated, whereas the remaining second part of the first group of at least one reactor including the last reactor stage of the at least two reactor stages is operated . The first part of the first group of at least one reactor including the first reactor stage is preferably at least one reactor, more preferably one reactor. The remaining second part of the first group of at least one reactor including the last reactor M / EPC-096-PC

[0126] 20 stage of the at least two reactor stages is preferably at least one reactor, more preferably one reactor.

[0127] In operating mode c), the second group of at least one reactor, the remaining second part of 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.

[0128] The operating mode a) of the inventive process comprises the following steps: i-a) subjecting the reactant material A) to an esterification reaction in the first group of at least one reactor to form a reaction material stream A), wherein the esterification reaction is carried out in at least two reaction stages; ii-a) pre-polycondensing of the reaction material stream A) in the third group of at least one reactor to form a pre-polycondensed reaction material stream; and iii-a) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET.

[0129] In step i-a) of operating mode a), the reactant material A) is formed in or preferably fed to the first reactor stage of the first group of at least one reactor, wherein the reactant material A) is subjected to an esterification reaction (first esterification stage). The reaction material obtained is fed from the first reactor stage to the subsequent reaction stage(s) of the first group of at least one reactor, wherein the esterification reaction is continued (second esterification stage and optionally further esterification stages) to finally form a reaction material stream A) which leaves the last reactor stage of the first group of at least one reactor. As mentioned, the at least two reactor stages are preferably at least two reactors, preferably two reactors.

[0130] In step ii-a) of operating mode a), the reaction material stream A) formed in the first group of at least one reactor is fed to the third group of at least one reactor, wherein the reaction material stream A) is subjected to pre-polycondensation M / EPC-096-PC

[0131] 21 reaction to form a pre-polycondensed reaction material stream. Specifically, the reaction material stream A) formed in the first group of at least one reactor 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 pre-polycondensation 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.

[0132] In step iii-a) of operating mode a), 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.

[0133] The operating mode b) of the inventive process comprises the following steps: i-b) subjecting a mixture of the reactant material B) and water to a hydrolysis reaction in the second group of at least one reactor to form a fully or partially hydrolysed reaction material stream; ii-b) subjecting the reactant material A) to an esterification reaction in the first group of at least one reactor, wherein the esterification reaction is carried out in at least two reaction stages and wherein the fully or partially hydrolysed reaction material stream obtained in step i-b) is mixed into a reaction material stream obtained after the first reaction stage of step ii-b) and before and / or in the last reaction stage of step ii-b) and continuing esterification of the mixture to form a reaction material stream B); iii-b) pre-polycondensing of the reaction material stream B) in the third group of at least one reactor to form a pre-polycondensed reaction material stream; and iv-b) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET;

[0134] In step i-b) of operating mode b), a mixture of the reactant material B) and water 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. M / EPC-096-PC

[0135] 22

[0136] 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 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 combined with an intermediate reaction material stream in the first group of at least one reactor as discussed below in more detail. As mentioned, the second group of at least one reactor preferably comprises or consists of one reactor.

[0137] In step ii-b) of operating mode b), the reactant material A) is formed in or preferably fed to the first reactor stage of the first group of at least one reactor, wherein the reactant material A) is subjected to an esterification reaction (first reaction stage or first esterification stage). The reaction material obtained is fed from the first reactor stage to the subsequent reaction stage(s) of the first group of at least one reactor, wherein the esterification reaction is continued . As mentioned, the at least two reactor stages of the first group of at least one reactor are preferably at least two reactors, preferably two reactors.

[0138] In this regard, step ii-b) of operating mode b) is analogous to step i-a) of operating mode b), but in addition the fully or partially hydrolysed reaction material stream obtained in step i-b) is combined with or mixed into an intermediate reaction material stream obtained after the first reaction stage of step ii-b) and before and / or in the last reaction stage of step ii-b) and esterification of the mixture is continued in at least the last reactor stage, preferably the last reactor, of the first group of at least one reactor to form a reaction material stream B). In other words, when the fully or partially hydrolysed reaction material stream obtained in step i-b) has been mixed into an intermediate reaction material stream obtained after the first reaction stage of step ii-b) and before and / or in the last reaction stage of step ii-b), it is the mixture of said intermediate reaction material stream and the fully or partially M / EPC-096-PC

[0139] 23 hydrolysed reaction material stream which is subjected to further esterification in the reactor stage(s) of the first group following the point of addition of the hydrolysed reaction material stream or, in case of addition of the fully or partially hydrolysed reaction material stream to the intermediate reaction in a reactor stage, in this reactor stage and possible subsequent reactor stage(s).

[0140] In a preferred embodiment, the first group of at least one reactor comprises two reactor stages, preferably two reactors, and the fully or partially hydrolysed reaction material stream obtained from step i-b) is mixed or combined with an intermediate reaction material stream obtained after the first reactor stage, preferably the first reactor, of the first group of at least one reactor, and before and / or in, preferably before, the second or last reactor stage, preferably the second or last reactor, of the first group, so that esterification of the mixture is continued in the second or last reaction stage or second or last reactor, respectively, of the first group.

[0141] The mixing of the fully or partially hydrolysed reaction material stream and the intermediate reaction material stream may be effected in a reaction stage, preferably a reactor, and / or a feeding line connecting two reactor stages, preferably two reactors, of the first group of at least one reactor.

[0142] The formed reaction material stream B) is fed from the last reactor stage, preferably the last reactor, of the first group of the at least one reactor to the single or first reactor of the third group of at least one reactor.

[0143] The reaction material stream B) formed in step ii-b) of operating mode b) can be similar to the reaction material stream A) formed in step i-a) of operating mode a), in particular with respect to the esterification conversion degree, as specified below.

[0144] In step iii-b) of operating mode b), the reaction material stream B) formed in step ii-b) is pre-polycondensed in the third group of at least one reactor to form a pre-polycondensed reaction material stream. In step iv-b) of operating mode b), final polycondensing of the pre-polycondensed reaction material stream is effected in the final reactor to form PET. M / EPC-096-PC

[0145] 24

[0146] Pre-polycondensing step iii-b) and final condensing step iv-b) of operating mode b) are analogous to pre-polycondensing step ii-a) and final condensing step iii-a), respectively, of operating mode a) except that the reaction material stream B) formed in step ii-b) of operating mode b) is fed to the third group of at least one reactor and not the reaction material stream A) formed in step i-a) of operating mode a).

[0147] In step iii-b) of operating mode b), the reaction material stream B) formed in step ii-b) is fed to the third group of at least one reactor, wherein the reaction material stream B) is subjected to pre-polycondensation reaction to form a prepolycondensed reaction material stream . Specifically, the reaction material stream B) formed in step ii-b) 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 prepolycondensed 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 pre-polycondensation 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.

[0148] In step iv-b) of operating mode b), 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.

[0149] The operating mode c) of 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 remaining second part of 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 M / EPC-096-PC

[0150] 25 iv-c) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET.

[0151] In step i-c) of operating mode 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 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 remaining second part of 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.

[0152] 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 remaining second part of the first group of at least one reactor including esterification to form a reaction material stream C).

[0153] In this regard, the fully or partially hydrolysed reaction material stream obtained from step i-c) is fed to the first reactor stage of the remaining second part of the first group of at least one reactor, where the further reaction takes place. If the remaining second part of the first group of at least reactor comprises more than one reactor stages, the reaction material stream obtained in the first reactor stage is fed to the subsequent reactor stage(s) of remaining second part of the first group of at least one reactor in series of the second group to continue further reaction. As mentioned, the remaining second part of the first group of at least one reactor second group of at least one reactor preferably comprises or consists of one reactor stage, more preferably one reactor. M / EPC-096-PC

[0154] 26

[0155] The reaction material stream C) formed in step ii-c) is fed from the single or last reactor stage of the remaining second part of the first group of at least reactor to the single or first reactor of the third group of at least one reactor.

[0156] The reaction material stream C) formed in step ii-c) of operating mode c) can be similar to the reaction material stream A) formed in step i-a) of operating mode a) or the reaction material stream B) formed in step ii-b) of operating mode b), respectively, in particular with respect to the esterification conversion degree, as specified below.

[0157] In step iii-c) of operating mode c), the reaction material stream C) formed in step ii-c) is pre-polycondensed 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.

[0158] Pre-polycondensing step iii-c) and final condensing step iv-c) of operating mode c) are analogous to pre-polycondensing step ii-a) and final condensing step iii-a), respectively, of operating mode a) except that the reaction material stream C) formed in step ii-c) of operating mode c) is fed to the third group of at least one reactor and not the reaction material stream A) formed in step i-a) of operating mode a).

[0159] In step iii-c) of operating mode 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 prepolycondensed reaction material stream. Specifically, the reaction material stream C) formed in step ii-c) 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 prepolycondensed 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 pre-polycondensation 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. M / EPC-096-PC

[0160] 27

[0161] 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.

[0162] The operation conditions, with which the reactor and reactor stages, respectively, are operated in operating modes a), b) and c) are in principle independent from each other, but essentially within the same ranges for each of operating mode a), b) and c).

[0163] Thus, for both operating mode a) and b) the reactor(s) of the first group of at least one reactor and for operating mode c) the remaining second part of the first group of at least one reactor including the last reactor stage of the at least two reactor stages 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).

[0164] If the first group of at least one reactor includes two or more reactors, preferably two reactors, the first reactor of the first group is preferably operated at a pressure of 1.4 bar(a) to 3.5 bar(a), preferably 1.5 to 3.0 bar(a), and the last reactor of the first group or the last reactor of the remaining second part of the first group is preferably operated at a pressure of 1.0 bar(a) to 1.8 bar(a), preferably 1.05 to 1.4 bar(a), wherein the temperature ranges given above equally apply.

[0165] For each of operating modes a), b) and c) 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).

[0166] 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 M / EPC-096-PC

[0167] 28 mbar(a), preferably 10 to 40 mbar(a), wherein the temperature ranges given above equally apply.

[0168] For each of operating modes a), b) and c) 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).

[0169] For each of operating modes b) and c) 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).

[0170] The suitable / preferred process parameter ranges for the reactors in operation used in operating modes a), b) and c) 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-096-PC

[0171] 29

[0172] 1For operating mode a) and b): the first group of at least one reactor, e.g. ESI and ES2. For operating mode c): the remaining second part of the first group of at least one reactor, e.g. ES2 (the first part of the first group is not operated in operating mode c)).

[0173] 2For operating mode b) and c): the second group of at least one reactor, e.g.

[0174] ESI.5. The second group of at least one reactor is not operated in operating mode a).

[0175] 3For each of operating mode a), b) and c): the third group of at least one reactor, e.g. PPI and PP2.

[0176] 4For each of operating mode a), b) and c): the final reactor, e.g. FIN.

[0177] In a preferred embodiment for all operating modes a), b) and c), 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.

[0178] In each of the reaction material stream A) formed in step i-a) of operating mode a), the reaction material stream B) formed in step ii-b) of operating mode b) and 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. The esterification conversion degree is preferably in the same range in reaction material stream A), reaction material stream B) and reaction material stream C).

[0179] 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 M / EPC-096-PC

[0180] 30 degree of 80% means that 80% of all carboxyl groups are esterified and 20% of all carboxyl groups are in free form (not esterified).

[0181] Thus, in a particular preferred embodiment of the inventive process, the reaction material stream A) formed in step i-a) of operating mode a), 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).

[0182] In a particular preferred embodiment of the inventive process, the reaction material stream B) formed in step ii-b) of operating mode b) 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).

[0183] 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).

[0184] This limited rate of esterification in reaction material stream A), reaction material stream B) or reaction material stream C), respectively, allows for a desired number of carboxyl end groups that are still free, which has an accelerating effect on the further reaction rate of the polycondensation reaction.

[0185] In general, in operating mode b) the feeding rate by weight of reactant material

[0186] A) to reactant material B) (A:B) may be typically in the range of 99: 1 to 1:99, preferably 95:5 to 5:95, more preferably 80:20 to 20:80.

[0187] In general, in operating mode c) the feeding rate by weight of reactant material

[0188] 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.

[0189] 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. M / EPC-096-PC

[0190] 31

[0191] 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.

[0192] 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 or the remaining second part the first group of at least one reactor, respectively, 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 finally reactor generally comprises MEG and optionally water.

[0193] In the following, main reactions which take place during the inventive process are discussed in more detail. The PET production generally comprises esterification and polycondensation reaction. In operating mode a), the esterification takes place in the first 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.

[0194] 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 stoichiometric requirements is preferably used to accelerate the reaction rate and achieve the reaction equilibrium phase.

[0195] (I) Formation of glycol terephthalate (esterification)

[0196] 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 M / EPC-096-PC

[0197] 32 following reaction schemes. It should be noted that one of the reaction products formed is BHET.

[0198] (II) Processing of chain length (poly-esterification)

[0199] 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 = 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-096-PC

[0200] 33

[0201] (III) Formation of di-ethylene glycol (DEG)

[0202] 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

[0203] Thus, in the esterification reaction carried out in at least two stages, preferably two stages, a high esterification conversion rate but not a complete esterification conversion rate can be achieved. This limited rate of esterification allows for a desired number of acidic end groups (carboxyl end groups) that are still free, which has an accelerating effect on the further reaction speed of the polycondensation reaction.

[0204] In the subsequent pre-polycondensation and final polycondensation reaction in the third group of at least one reactor and the 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. M / EPC-096-PC

[0205] 34

[0206] 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.

[0207] In operating mode b) and c), BHET is used. In operating mode b) it is used in addition to MEG and TPA. In operating mode c) it replaces MEG and TPA. The BHET mixed with water is subjected to hydrolysis reaction in the second group of at least one reactor in operating mode b) and c). 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 operating mode a). Thus, components present in the esterification reaction of operating mode a) are also present based on BHET in operating modes b) and c). Accordingly, similar reactions of esterification discussed above for operating mode a), also take place in operating mode b) and c).

[0208] In each of operating mode a), b) and c), the esterification product obtained (reaction material stream A) in operating mode a), reaction material stream B) in operating mode b), reaction material stream C) in operating mode c)), is then fed continuously to the subsequent pre-polycondensation in the third group of at least one reactor and the final reactor.

[0209] In each of operating modes a), b) and c), the second stage of the reaction progresses under a defined vacuum and temperature, first in the prepolycondensation 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 pre-polycondensation process and final polycondensation process, it is usually necessary to add a condensation catalyst at a proper time.

[0210] 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.

[0211] 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 M / EPC-096-PC

[0212] 35 volatile byproducts, which is preferably a vacuum system comprising a vapor condensation stage, vacuum jet system and vacuum pumps.

[0213] The final polycondensation typically takes place in an agitated horizontal reactor, in particular a horizontal reactor equipped with agitator made up of multiple 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.

[0214] The PET formed in the final reactor can be subjected to further refinement. Thus, the inventive process may comprise the following steps for each of operating mode a), b) and c): 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.

[0215] 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.

[0216] 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. M / EPC-096-PC

[0217] 36

[0218] The finished PET chips can be fed to the packaging station via silos and silo mixing plants, where they are filled and stored.

[0219] The invention is also directed to a plant for variable continuous production of polyethylene terephthalate (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 the inventive process as described above.

[0220] 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.

[0221] 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 two reactors; 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.

[0222] If the first group of at least one reactor consists of one reactor, the reactor includes at least two reactor stages, preferably two reactor stages.

[0223] In a preferred embodiment, the inventive plant further comprises

[0224] - a paste preparation vessel for mixing TPA and MEG and optionally one or more polycondensation catalysts and / or additives such as IPA and / or DEG to obtain reactant material A);

[0225] - transporting means for feeding reactant material A) to the first reactor of the first group of at least one reactor;

[0226] - 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;

[0227] - 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 M / EPC-096-PC

[0228] 37

[0229] - 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).

[0230] Inventive process for continuous production of polyethylene terephthalate (PET)

[0231] The inventive process of variable continuous production of PET described above can switch between three operating modes a), b) and c) or can switch between operating modes a) and b) or is according to operating mode b) only. With respect to operating mode c), it is also possible to carry out the process without the possibility to switch to the other operating modes. In other words, the invention is also directed to a process of continuous production of PET according to operating mode c) only.

[0232] Accordingly, the invention is also directed to the following items.

[0233] Item 1. 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 M / EPC-096-PC

[0234] 38 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.

[0235] The inventive process for continuous production of PET according to item 1 (in the following also designated second inventive process) corresponds to the inventive process for variable continuous production of PET (in the following also designated first inventive process) in operating mode c) without reference to operating modes a) and b). Accordingly, the first group of at least one reactor of the inventive process for continuous production of PET according to item 1 corresponds to the remaining second part of the first group of at least one reactor including the last reactor stage of the at least two reactor stages used in operating mode c) of the inventive process for variable continuous production of PET. Considering that all disclosure related to operating mode c) of the first inventive process equally apply to the second inventive process so that reference is made thereto.

[0236] Item 2. The process according to item 1, 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.

[0237] Item 3. The process according to any one of the preceding items, 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 M / EPC-096-PC

[0238] 39 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).

[0239] Item 4. The process according to any one of the preceding items, 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).

[0240] Item 5. The process according to any one of the preceding items, 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.

[0241] Item 6. The process according to any one of the preceding items, 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 2.5 wt.%, based on the total weight of the mixture of the reactant material B), water and the reactant material C).

[0242] Item 7. The process according to any one of the preceding items, wherein the reactant material C) is in form of a paste (IPA paste) comprising isophthalic acid (IPA) and at least one of monoethylene 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. M / EPC-096-PC

[0243] 40

[0244] Item 8. The process according to any one of the preceding items, 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.

[0245] Item 9. The process according to any one of the preceding items, 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.

[0246] Item 10. The process according to any one of the preceding items, wherein the BHET used in the process is recycled BHET, preferably obtained from a chemical recycling of PET waste.

[0247] Item 11. The process according to any one of the preceding items, 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.

[0248] Item 12. The process according to any one of the preceding items, 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, 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.

[0249] Item 13. The process according to any one of the preceding items, 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 M / EPC-096-PC

[0250] 41 the solid PET material with increased intrinsic viscosity, preferably in chip form, is preferably bottle grade PET.

[0251] Item 14. 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 items 1 to 13.

[0252] Item 15. The plant of item 14, 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.

[0253] Item 16. The plant of item 14 or item 15, further comprising

[0254] - 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;

[0255] - 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

[0256] - 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).

[0257] Drawings

[0258] The invention in all its aspects is further described in the following drawings related to specific embodiments of the invention, which however are in no way intended to limit the scope of the invention. The accompanying drawings show block flow diagrams for each of operating modes a), b) and c) to which the first inventive process can switch. In particular, the accompanying drawings show in:

[0259] Fig. 1 a block flow diagram for an exemplary and preferred operating mode a) of the first inventive process for variable continuous production of PET M / EPC-096-PC

[0260] 42

[0261] Fig. 2 a block flow diagram for an exemplary and preferred operating mode b) of the first inventive process for variable continuous production of PET

[0262] Fig. 3 a block flow diagram for an exemplary and preferred operating mode c) of the first inventive process for variable continuous production of PET or for the second inventive process

[0263] In the drawings, a preferred embodiment is shown, wherein the first group of at least one reactor consists of two reactors (ESI and ES2), the second group of at least one reactor consists of one reactor (ESI.5), and the third group of at least one reactor consists of two reactors (PPI and PP2), but the number of reactors for each group is not limited thereto and may vary.

[0264] Fig. 1 is a block flow diagram schematically showing a preferred example of operating mode a) of the first inventive process for variable continuous production of PET. It shows a first reactor of the first group of at least one reactor (ESI), a second 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) which are connected in series in this order. In operating mode a), the second group of at least one reactor is not operated.

[0265] As a starting material (reactant material A), a TPA paste comprising terephthalic acid (TPA) and ethylene glycol (MEG) is prepared in a paste preparation vessel. In a preferred embodiment diethylene glycol (DEG), isophthalic acid (IPA) and at least one polycondensation catalyst (Catalysts) and optionally one or more additives are also added to the TPA paste. The TPA paste is fed to the first reactor of the first group (ESI) and subjected to an esterification reaction (first esterification stage), the reaction material stream obtain is fed from ESI to the second reactor of the first group (ES2), wherein esterification reaction is continued (second esterification stage). The resulting reaction material stream A) 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 pre-polycondensed reaction material stream is effected to form PET leaving the reactor in form of a melt. M / EPC-096-PC

[0266] 43

[0267] Fig. 2 shows a block flow diagram for schematically showing a preferred example of an exemplary and preferred operating mode b) of the first inventive process for variable continuous production of PET. As for operating mode a) shown in Fig. 1, it shows a first reactor of the first group of at least one reactor (ESI), a second 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) which are connected in series in this order. In addition, there is a single reactor of the second group of at least one reactor (ESI.5), which work in parallel with ESI.

[0268] The operation according to operating mode a) described above, is effected analogously in operating mode b), except that a fully or partially hydrolysed reaction material stream obtained from the single reactor of the second group (ESI.5) is combined and mixed with the reaction material stream leaving the first reactor of the first group (ESI) in the feeding line between reactor ESI and reactor ES2. Accordingly, the reaction material fed to reactor ES2 is a mixtu re of the reaction material stream leaving the first reactor ESI and the fully or partially hydrolysed reaction material stream produced in reactor ESI.5. Hence, the first esterification stage in reactor ESI is the same as in operating mode a), whereas in the second esterification stage in reactor ES2, it is the mixture of the reaction material stream from ESI and the fully or partially hydrolysed reaction material stream from ESI.5. which is subjected to further esterification reaction. As a result, a reaction material stream B) is leaving reactor ES2. The further operation of reaction material stream B) in reactors PPI, PP2 and FIN is the same as the operation of reaction material stream A) in operating mode a) described for Fig. 1.

[0269] According to operating mode b), BHET is melted in a melting device (BHET Melt). The melted BHET (reactant material B) is combined with water and the mixture is fed to reactor ESI.5, wherein it is subjected to a hydrolysis reaction, i n order to obtain the fully or partially hydrolysed reaction material stream, preferably the partially hydrolysed reaction material stream, in reactor ESI.5, which is combined with the reaction material stream, leaving reactor ESI as discussed above.

[0270] Fig. 3 shows a block flow diagram for an exemplary and preferred operating mode c) of the first inventive process for variable continuous production of PET or for the second inventive process for continuous production of PET. The M / EPC-096-PC

[0271] 44 following description refers to operating mode c), but as indicated, the second inventive process corresponds to operating mode c) of the first inventive process so that the description equally applies to the second inventive process.

[0272] Fig. 3 shows 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), which are connected in series in this order. In operating mode c), the single reactor of the first group of at least one reactor (ES2) represents the remaining second part of the first group of at least one reactor (i.e. ESI is not operated).

[0273] 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.

[0274] 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.

[0275] The further operation of reaction material stream C) in reactors PPI, PP2 and FIN is the same as the operation of reaction material stream A) in operating mode a) described for Fig. 1.

[0276] In all of operating modes a), b) and c), the reactors ESI, ES2, ESI.5 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. M / EPC-096-PC

[0277] 45

[0278] In all of operating modes a), b) and c), the reactors can be operated with the operating conditions described above. Of course, this does not apply for the reactors which are not in operation depending on the operating mode.

[0279] In all of operating modes a), b) and c), volatiles are generally removed from ESI, ESI.5 and ES2, if in operation, 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. The PET formed in FIN is discharged from FIN in form of a PET melt.

[0280] List of reference signs ESI first reactor of first group of at least one reactor

[0281] ES2 second reactor of first group of at least one reactor

[0282] ESI.5 single reactor of second group of at least one reactor

[0283] PPI first reactor of third group of at least one reactor

[0284] PP2 second reactor of third group of at least one reactor FIN final reactor

Claims

M / EPC-096-PC46Claims1. 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 first group of at least one reactor includes at least two reactor stages, wherein the process can switch between three operating modes a), b) and c) or can switch between operating modes a) and b) or is according to operating mode b), wherein depending on the operating mode one or more of the following reactant materials are used : a reactant material A) comprising terephthalic acid (TPA) and ethylene glycol (MEG); 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 in operating mode a) and operating mode b) 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 in operating mode a) the second group of at least one reactor is not operated, wherein in operating mode c) a first part of the first group of at least one reactor including the first reactor stage of the at least two reactor stages is not operated, whereas a remaining second part of the first group of at least one reactor including the last reactor stage of the at least two reactor stages is operated, and the second group of at least one reactor, the remaining second part of 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 operating mode a) comprisesM / EPC-096-PC47 i-a) subjecting the reactant material A) to an esterification reaction in the first group of at least one reactor to form a reaction material stream A), wherein the esterification reaction is carried out in at least two reaction stages; ii-a) pre-polycondensing of the reaction material stream A) in the third group of at least one reactor to form a pre-polycondensed reaction material stream; and iii-a) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET; wherein the operating mode b) comprises i-b) subjecting a mixture of the reactant material B) and water to a hydrolysis reaction in the second group of at least one reactor to form a fully or partially hydrolysed reaction material stream; ii-b) subjecting the reactant material A) to an esterification reaction in the first group of at least one reactor, wherein the esterification reaction is carried out in at least two reaction stages and wherein the fully or partially hydrolysed reaction material stream obtained in step i-b) is mixed into a reaction material stream obtained after the first reaction stage of step ii-b) and / or before or in the last reaction stage of step ii- b) and continuing esterification of the mixture to form a reaction material stream B); iii-b) pre-polycondensing of the reaction material stream B) in the third group of at least one reactor to form a pre-polycondensed reaction material stream; and iv-b) final polycondensing of the pre-polycondensed reaction material stream in the final reactor to form PET; wherein the operating mode c) 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;M / EPC-096-PC48 ii-c) subjecting the fully or partially hydrolysed reaction material stream to further reaction in the remaining second part of 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-b) of operating mode b) is at least in part recycled water removed as a byproduct of esterification reaction in step ii-b) of operating mode b), and / or the water used in step i-c) of operating mode c) is at least in part recycled water removed as a byproduct of esterification reaction in step ii-c) of operating mode c) and / or as a retained byproduct of esterification reaction in step ii- b) of operating mode b).

3. The process according to claim 1 or claim 2, wherein in each of operating modes a), b) and c) 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 for both operating mode a) and b) the reactor(s) of the first group of at least one reactor and for operating mode c) the remaining second part of the first group of at least one reactor including the last reactor stage of the at least two reactor stages 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 for each of operating modes a), b) and c) 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 atM / EPC-096-PC49 a temperature in a range of 265 to 285 °C and a pressure of 10 to 250 mbar(a); and / or for each of operating modes a), b) and c) 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 for each of operating modes b) and c) 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 in operating mode a): the reactant material A) comprises isophthalic acid (IPA), wherein the amount of IPA is preferably 0.1 to 5 wt.%, more preferably 0.2 to 2 wt.%, based on the total weight of reactant material A); in operating mode b): the reactant material A) and / or the reactant material B), preferably the reactant material A), comprises isophthalic acid (IPA), wherein the amount of IPA is preferably 0.1 to 4.5 wt.%, more preferably 0.2 to 1.8 wt.%, based on the total weight of reactant material A) and reactant material B); in operating mode c): 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 2.5 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 in operating mode a): the reactant material A) comprises diethylene glycol (DEG), wherein the amount of DEG is preferably 0.1 to 2 wt.%, moreM / EPC-096-PC50 preferably 0.2 to 1.5 wt.%, based on the total weight of reactant materialA); in operating mode b): the reactant material A) and / or the reactant materialB), preferably the reactant material A), comprises diethylene glycol (DEG), wherein the amount of DEG is preferably 0.1 to 2.5 wt.%, more preferably 0.2 to 2.0 wt.%, based on the total weight of reactant material A) and reactant material B).

9. The process according to any one of the preceding claims, wherein in operating mode c) the reactant material C) is in form of a paste (IPA paste) comprising isophthalic acid (IPA) and at least one of monoethylene glycol (MEG) and / or diethylene glycol (DEG) and optionally the at least one polycondensation catalyst, wherein the total 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 in operating mode c), 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.

10. The process according to any one of the preceding claims, wherein the molar ratio of MEG:TPA in reactant material A) is in the range of 1.05 - 1.30 : 1, preferably 1.08 - 1.25 : 1, more preferably 1.1 - 1.20 : 1, and / or wherein the weight ratio of BHET to water (BHET : water) in the mixture of the reactant material B) and water in step i-b) of operating mode b) and / or in the mixture of the reactant material B), water and reactant material C) in step i-c) of operating mode c) is in the range of 100-140 : 1, preferably 110-130 : 1, more preferably 115-125 : 1.

11. The process according to any one of the preceding claims, wherein the reaction material stream B) formed in step ii-b) of operating mode b) and / or the reaction material stream A) formed in step i-a) of operating mode a) and / or the reaction material stream C) formed in step ii-c) of operating mode c) have an esterification conversion rate of 94 to 99%, preferably 95M / EPC-096-PC51 to 97%, more preferably 95.5 to 96.5%, so that the reaction material still includes carboxyl end groups.

12. The process according to any one of the preceding claims, wherein the BHET used in operating mode b) and / or operating mode c) of the process is recycled BHET, preferably obtained from a chemical recycling of PET waste.

13. The process according to any one of the preceding claims, wherein in operating mode b) the feeding rate by weight of reactant material A) to reactant material B) (A:B) is in the range of 99: 1 to 1:99, preferably 95:5 to 5:95, more preferably 80:20 to 20:80.

14. 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, 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.

15. The process according to any one of the preceding claims, wherein for both operating mode a) and b) the preparation of reactant material A) comprises feeding TPA and MEG into a paste preparation vessel to mix the raw materials to obtain a raw material mixture of PTA and MEG, wherein at least one of IPA and DEG and optionally the at least one polycondensation catalyst are preferably added to the paste preparation vessel, wherein all components are preferably added to the paste preparation vessel via a separate line.

16. The process according to any one of the preceding claims, further comprising the following steps for each of operating mode a), b) and c): processing the PET material stream withdrawn from the final reactor to prepare a solid PET material, preferably in form of PET chips,M / EPC-096-PC52 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.

17. A plant for variable continuous production of polyethylene terephthalate (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 17.

18. The plant of claim 17, wherein the first group of at least one reactor consists of one or two reactors, preferably two reactors; the second group of at least one reactor consists of one reactor, and / or the third group of at least one reactor consists of one, two or three reactors, preferably one or two reactors, more preferably two reactors.

19. The plant of claim 17 or claim 18, further comprising- a paste preparation vessel for mixing TPA and MEG and optionally one or more polycondensation catalysts and / or additives such as IPA and / or DEG to obtain reactant material A);- transporting means for feeding reactant material A) to the first reactor of the first group of at least one reactor;- 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; and- 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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