Pyrolysis process

Abstract

The present application relates to a process for the pyrolytic production of benzoic acid and / or terephthalic acid from PET-containing materials, in which a melt of a PET-containing material (2) is present at a temperature of 350 to 750°C, in particular 380 to 600°C, most particularly preferably from 400 to 500°C, in a zone "A" in the lower region of a pyrolysis reactor (1), and the resulting pyrolysis gas cools in a zone "C", such that a material containing benzoic acid and / or terephthalic acid is deposited.

Description

[0001] P45576PC00 / XII / XII 10.11.2025

[0002] 1

[0003] Coroplast Fritz Müller GmbH & Co. KG, Wittener Str. 271, 42279 Wuppertal; Bergische Universität Wuppertal, a public corporation, Gaußstr. 20, 42119 Wuppertal

[0004] "Pyrolysis process"

[0005] The invention relates to a process for producing benzoic acid and / or terephthalic acid from polyethylene terephthalate (PET)-containing materials, in particular a process for producing solid benzoic acid-containing materials according to the claims.

[0006] Terephthalic acid is a monomeric component of PET. Annual production of terephthalic acid was 37.3 million tons in 2006 and has increased significantly since then. Besides PET production, terephthalic acid is also used in the production of other technical polyesters, such as polybutylene terephthalate (PBT) for thermally demanding automotive applications in engine compartments and aromatic polyamides of the aramid type (e.g., Kevlar®) for high-tensile fibers.

[0007] Benzoic acid is a raw material with a wide range of industrial applications. It is used as a preservative (E 210) in the cosmetics, food, and tobacco industries. Due to its superior solubility, the salts of benzoic acid, such as sodium benzoate (E 211), potassium benzoate (E 212), and calcium benzoate (E 213), are also widely used. Furthermore, benzoic acid is a starting material for fragrances, plasticizers, and local anesthetics (benzoic acid esters, such as ethyl benzoate), as well as biocides (benzyl esters of benzoic acid).

[0008] In the chemical industry, benzoic acid is produced in large quantities by the oxidation of toluene, and terephthalic acid by the oxidation of p-xylene. The two starting materials, toluene and p-xylene, are primarily obtained through the distillation of crude oil in refineries. P45576PC00 / XI 1 / XI I 10.11.2025

[0009] 2

[0010] They are therefore based on fossil raw materials. There are two major problems associated with fossil raw materials: firstly, their limited availability, and secondly, the release of CO2 during their use.

[0011] Accordingly, there is a need in industry for alternative sources of such raw materials.

[0012] Recently, a number of projects have been launched with the aim of producing raw materials on an industrial scale from existing products. Due to the increasing consumption of plastics in recent decades and the resulting volumes of waste, the recycling of plastics has moved into sharper focus. In addition to traditional recycling, which aims to recover the original raw material from existing products, new processes have recently become established that focus not on recovering the original raw material, but rather on creating a different valuable material.

[0013] An example of such a recycling process is advertised by BASF under the name "ChemCycling", in which a pyrolysis oil is obtained from mixed plastic waste, which, after appropriate purification, can be used again at the beginning of BASF's integrated production process.

[0014] The object of the present invention was therefore to develop an alternative manufacturing process for benzoic acid and / or terephthalic acid, in particular for the production of benzoic acid, which does not rely on the use of new fossil raw materials and is characterized by good yield and high purity of the products. Furthermore, the object of the present invention was to recycle existing plastic resources and to reintroduce the resulting products into the value chain, thus enabling a circular economy. P45576PC00 / XI 1 / XI I 10.11.2025

[0015] 3

[0016] In the course of the work underlying this invention, it was found that benzoic acid and / or terephthalic acid, in particular benzoic acid, can be obtained in good yield and high purity from PET-containing materials using a simple pyrolytic process, whereby, in contrast to the described and known processes, no or very little pyrolysis oil is produced.

[0017] A first preferred embodiment of the present invention relates to a process for the pyrolytic production of benzoic acid and / or terephthalic acid from PET-containing materials, wherein

[0018] - a melt of PET-containing material is located in a zone “A” in the lower region of a pyrolysis reactor at a temperature of 350 to 750 °C, in particular 380 to 600 °C, most preferably 400 to 500 °C, and

[0019] - the resulting pyrolysis gas cools down in a zone “C”, so that a material containing benzoic acid and / or terephthalic acid is deposited.

[0020] The process according to the invention is preferably carried out in a pyrolysis apparatus which may have one or more process engineering components, but must necessarily include at least one so-called "pyrolysis reactor" in which the actual pyrolysis reaction takes place.

[0021] According to the invention, the term "benzoic acid" refers to the basic benzoic acid compound itself, but also to its salts and esters (benzoates). A restriction of this term to the basic benzoic acid compound itself may be preferred according to the invention.

[0022] According to the invention, the term "terephthalic acid" refers to the basic structure of terephthalic acid itself, but also to its salts and esters (terephthalates). A restriction of this term to the basic structure of terephthalic acid itself may be preferred according to the invention. P45576PC00 / XI 1 / XI I 10.11.2025

[0023] 4

[0024] According to the invention, the term "pyrolysis gas" refers to the products formed during pyrolysis that leave the reaction zone in a gaseous state. The invention also includes gases containing solid or liquid suspended particles (aerosols).

[0025] The present invention is not subject to any restrictions with regard to the type of PET used; thus, both virgin PET and PET obtained from recycled materials can be used.

[0026] PETs obtained from recycled materials are categorized as either "post-consumer" material or "post-industrial" material.

[0027] Post-consumer materials are recovered from waste products that are no longer usable – either from households or businesses. Typical source materials include plastic bottles, packaging, and other plastic waste.

[0028] In contrast, post-industrial materials are derived from waste generated during a manufacturing process that cannot be recycled back into production. These PET-containing materials often offer a higher level of quality because they are generated immediately after manufacturing and have not been contaminated by their use, such as daily wear and tear.

[0029] In both cases, however, it is desirable to return as much of the resulting PET-containing plastic waste as possible to the circular economy.

[0030] Another problem with conventional recycling is that PET-containing waste materials often consist of several different materials that cannot be easily separated mechanically and / or chemically, but cannot be recycled together due to their interactions. This is described in P45576PC00 / XI 1 / XI I 10.11.2025

[0031] 5

[0032] PET contained in composite materials is therefore not available for material recycling. This disadvantage is overcome by the use of the pyrolytic process according to the invention.

[0033] An example of the generation of PET-containing "post-industrial" materials can be observed in the production of adhesive tapes. In current adhesive tape production, wide carrier webs made of woven fabrics, nonwovens, or films are typically coated with adhesive and, after the adhesive has dried or cross-linked, are initially wound onto large rolls, known as master rolls. Slitting processes are then used to produce significantly smaller adhesive tape rolls from these wide master rolls, resulting in a manageable size for end users. Since the adhesive tape is not always homogeneous at the edges of the master roll, this process generates material at the edges that is unsuitable for sale. Because the carrier material and the adhesive cannot be separated after coating, conventional mechanical recycling is not possible.In contrast, the inventive method based on complete pyrolysis enables the use of the entire material without prior cleaning, separation or other processing.

[0034] According to the invention, the temperature of the melt located in zone “A” is preferably measured in the center of the melt (both horizontally and vertically). In any case, however, the temperature must be determined in an area sufficiently far from the heated walls of the pyrolysis reactor to avoid distortions caused by the temperature gradient resulting from the heating. Measuring the temperature outside the thermal boundary layer is particularly preferred according to the invention.

[0035] According to the invention, it is preferred if the heating power of the pyrolysis reactor is controlled such that, in the course of the progressive pyrolysis, the temperature of the PET-containing melt remains within the range of 350 to 750 °C according to the invention, P45576PC00 / XII / XII 10.11.2025

[0036] 6

[0037] especially from 380 to 600 °C, most preferably from 400 to 500 °C, in particular that a temperature plateau is formed, i.e. the temperature during the reaction only fluctuates within a range of ± 20 °C, in particular ± 10 °C.

[0038] It is further preferred according to the invention that the pyrolysis process according to the invention is terminated as soon as an increase in the temperature of the PET-containing melt is observed at constant heating power, in particular as soon as the temperature of the PET-containing melt leaves the set temperature plateau, and / or when the development of the pyrolysis gas decreases, recognizable by the reduction of bubble formation within the PET-containing melt.

[0039] Within the framework of the inventive method, it has proven advantageous if

[0040] - the resulting pyrolysis gas first flows through a zone "D" before reaching zone "C", in which at least part of the resulting pyrolysis gas condenses, and the remaining pyrolysis gas flows into zone "C" of the pyrolysis apparatus, and

[0041] - at least part of the condensate is returned to the incoming pyrolysis gas within the pyrolysis reactor and fed back into the pyrolysis process, and any remaining condensate flows into zone “C” of the pyrolysis apparatus.

[0042] According to the invention, the process is such that the two aspects occur largely simultaneously during the ongoing pyrolysis reaction; that is, as soon as a sufficient quantity of condensate has been formed according to the first feature, at least a portion of the condensate according to the second feature is returned to the pyrolysis reactor, while at the same time further condensate is formed according to the first feature. P45576PC00 / XII / XII 10.11.2025

[0043] 7

[0044] The zone "D", in which the at least partial condensation of the resulting pyrolysis gas takes place, can be part of the pyrolysis reactor, in particular a cooler part of the pyrolysis reactor. However, according to the invention, it is also preferred if the condensation of the resulting pyrolysis gas takes place in a separate component of the pyrolysis apparatus, such as a downstream dephlegmator or a downstream condenser. It is further preferred according to the invention if the at least partial condensation of the resulting pyrolysis gas takes place both within the pyrolysis reactor and in a separate component of the pyrolysis apparatus. It is particularly preferred according to the invention if the zone "D", in which the at least partial condensation of the resulting pyrolysis gas takes place, is a downstream dephlegmator.

[0045] Regardless of the design of the inventive zone “D” of the pyrolysis apparatus, it is preferred if it has a temperature in the range of 125 to 250 °C, in particular in the range of 130 to 200 °C.

[0046] Furthermore, it has proven advantageous if zone "D" has a volume that is at least as large as the volume of the melt of the PET-containing material. A volume of zone "D" that is larger than the volume of the melt of the PET-containing material is particularly preferred.

[0047] In cases where zone "D" is designed as a separate component of the pyrolysis apparatus, it has proven preferable for the resulting pyrolysis gas to flow from the pyrolysis reactor into the separate component, in particular the dephlegmator, via heated transfer channels. These transfer channels are preferably located at the top of the pyrolysis reactor (in the upper region), but an outlet for the benzoic acid-containing pyrolysis gas in another section of the pyrolysis reactor is also included according to the invention.

[0048] Since in this embodiment of the process according to the invention the pyrolysis and the thermal separation of the pyrolysis gas occur simultaneously within the P45576PC00 / XI 1 / XI I 10.11.2025

[0049] 8

[0050] If the process takes place in a pyrolysis reactor or when using a separate component within the pyrolysis apparatus, it can also be called "reactive rectification".

[0051] Although the presence of mechanical separating plates, which is frequently suggested in the literature for reactive rectifications, can in principle be provided within the pyrolysis reactor according to the invention, it has proven to be particularly advantageous if there is no mechanical separating plate within the pyrolysis reactor, since the process according to the invention enables an excellent yield of benzoic acid in high purity even without the presence of mechanical separating plates.

[0052] In comparison to the process according to the invention, prior art pyrolysis processes often remove the pyrolysis gas generated too quickly from the pyrolysis zone, resulting in insufficient decarboxylation of the PET-containing material and the formation of larger quantities of terephthalic acid and other undesirable byproducts. Excessively rapid cooling of the benzoic acid generated is also frequently observed in prior art pyrolysis processes, which is disadvantageous because the benzoic acid contained in the condensate makes a significant contribution to the further decarboxylation of the terephthalic acid components.

[0053] Within the scope of the present invention, it is preferred if a portion of the resulting pyrolysis gas condenses in zone "D", and the remaining portion of the resulting pyrolysis gas flows from zone "D" into zone "C" of the pyrolysis apparatus. According to the invention, it is preferred if the remaining portion of the resulting pyrolysis gas, which flows in gaseous form into zone "C" of the pyrolysis apparatus, contains at least 25 wt% benzoic acid. A benzoic acid content of at least 40 wt% is particularly preferred.

[0054] According to the invention, it can be particularly advantageous if the entire condensate is returned as a reflux to the incoming pyrolysis gas within the pyrolysis reactor P45576PC00 / XII / XII 10.11.2025

[0055] 9

[0056] The condensate is either directed back towards the incoming pyrolysis gas and fed back into the pyrolysis process. However, according to the invention, it can also be preferred – particularly when a downstream dephlegmator is used – if only part of the condensate is directed back towards the incoming pyrolysis gas within the pyrolysis reactor and fed back into the pyrolysis process, with the remaining portion flowing directly into zone "C" of the pyrolysis apparatus. The condensate can preferably be divided by a valve, in particular a splitter valve. According to the invention, it is preferred if the remaining portion of the condensate, which flows directly into zone "C" of the pyrolysis apparatus, contains at least 25 wt% benzoic acid, preferably at least 40 wt% benzoic acid.

[0057] According to the invention, it is particularly preferred if the mixture of the remaining part of the resulting pyrolysis gas, which flows gaseily into zone “C” of the pyrolysis apparatus, and the remaining part of the condensate, which flows directly into zone “C” of the pyrolysis apparatus, contains at least 25 wt.% benzoic acid, preferably at least 40 wt.% benzoic acid.

[0058] However, the benzoic acid content in the resulting pyrolysis gas can vary during the process according to the invention, particularly during batch operation of the pyrolysis reactor. Especially at the beginning of the pyrolysis, volatile components are typically released, which escape as part of the resulting pyrolysis gas. Therefore, the benzoic acid content, particularly when determined in the gaseous component, is preferably determined as the average of the amount of benzoic acid present in each of the middle thirds of the pyrolysis process. Furthermore, the benzoic acid content is influenced by the purity of the pyrolyzed PET-containing material; the lower the PET content of the input material, the lower the proportion of benzoic acid in the resulting gas.

[0059] Pyrolysis gas. P45576PC00 / XI 1 / XI I 11 / 10 / 2025

[0060] 10

[0061] Furthermore, it has proven advantageous if, during the pyrolysis reaction, the reflux rate of the benzoic acid contained in the resulting pyrolysis gas is in a mass ratio of 1 : 1 to 1 : 10 (wt% benzoic acid that is transferred directly from zone “D” as part of the gas and / or, if applicable, the condensate to zone “C” : wt% benzoic acid that is returned to the pyrolysis area from zone “D” as part of the condensate).

[0062] According to the invention, the mass of benzoic acid that flows back into the pyrolysis reactor as reflux in the condensate is preferably determined in the area of ​​the head of the pyrolysis reactor and / or at the corresponding condensate outlet of the dephlegmator.

[0063] In this context, it can be advantageous – particularly in batch-operated pyrolysis reactors – according to the invention for the reflux rate of the benzoic acid formed to vary during the process. While at the beginning of the pyrolysis reaction the majority of the benzoic acid produced is refluxed as condensate (reflux rate of the benzoic acid produced in a mass ratio of 1:5 to 1:10), it can be advantageous if towards the end of the reaction half of the benzoic acid produced, or even a higher proportion, flows directly into zone "C" (preferred reflux rate of the benzoic acid produced in a mass ratio of 2:1 to 1:2).

[0064] In this embodiment, it is particularly preferred according to the invention if the returning condensate picks up any solid intermediate products that may have formed and precipitated within the pyrolysis reactor, and returns them to the pyrolysis process. The pick-up of the precipitated intermediate products can preferably be achieved by dissolving / dispersing the intermediate products in the condensate, by remelting the intermediate products, and / or by rinsing the precipitated intermediate products with the condensate. P45576PC00 / XI 1 / XI I 10.11.2025

[0065] 11

[0066] Preferably, the returned condensate contains at least 1 wt% terephthalic acid, and in particular at least 5 wt% terephthalic acid. According to the invention, the terephthalic acid content returning in the condensate is preferably determined in the region of the head of the pyrolysis reactor and / or at the corresponding condensate outlet of the dephlegmator.

[0067] Another essential component of the reflux condensate is benzoic acid. The ratios of terephthalic acid and benzoic acid in the reflux condensate vary during the course of the process according to the invention. While a higher proportion of terephthalic acid is observed at the beginning of the reaction, this decreases significantly towards the end of the reaction, particularly in the case of batch experiments.

[0068] Without being bound to this theory, it can be assumed that, according to the invention, the recycling of the benzoic acid-containing condensate makes it possible to feed the terephthalic acid formed back into the pyrolysis process, so that further benzoic acid is produced from it by decarboxylation; thus, the yield and purity of the recovered benzoic acid are increased. Although the decarboxylation of the terephthalic acid-containing material can, in principle, also take place in the appropriately hot gas phase directly above the melt of the PET-containing material, it is preferred according to the invention if the recycled condensate combines with the melt of the PET-containing material.

[0069] To increase the yield of pure benzoic acid, it has also proven advantageous to mechanically recycle any solid intermediates that may have formed and precipitated within the pyrolysis reactor. To achieve this, mechanical recycling must take place during the ongoing pyrolysis reaction. Mechanical recycling can be accomplished, for example, by scraping the solid intermediates from the reactor walls. This scraping can be done using special, high-temperature-resistant scrapers and / or brushes. But P45576PC00 / XI 1 / XI I 10.11.2025

[0070] 12

[0071] The invention also includes the removal of solid intermediate products by vibration, ultrasound treatment or other suitable measures.

[0072] A combination of recycling the solid intermediate products by means of the returning condensate and by means of mechanical removal may be particularly preferred according to the invention.

[0073] The proportion of the resulting pyrolysis gas that flows directly in gaseous form from zone “D” to zone “C” can be influenced in particular by increasing the pressure inside the pyrolysis reactor, by applying a negative pressure in the parts of the pyrolysis apparatus outside the pyrolysis reactor or by adjusting a support gas flow.

[0074] According to the invention, it is particularly advantageous, especially when using a dephlegmator, if a suitable sensor system determines the proportion of benzoic acid in the condensate formed, and the reflux rate is adjusted based on this. Suitable analytical methods for such a sensor system include, for example, NIR, online gas chromatography, or ultrasound. The condensate formed is preferably divided by a valve, in particular a controlled valve, and most preferably a controlled splitting valve. As described above, the analytical determination of the proportion of benzoic acid flowing back in the condensate is preferably carried out, according to the invention, in the region of the head of the pyrolysis reactor and / or at the corresponding condensate outlet of the dephlegmator.

[0075] When using such sensor systems, it is preferred according to the invention to vary the proportion of returned condensate depending on the proportion of benzoic acid in the condensate formed; thus, it may be preferred according to the invention to continuously reduce the proportion of condensate that is returned to the pyrolysis reactor towards the end of the pyrolysis reaction or when a desired benzoic acid concentration in the condensate is reached, and P45576PC00 / XII / XII 10.11.2025

[0076] 13

[0077] finally to reduce it to 0%, thus transferring all the condensate to zone “C”.

[0078] According to the invention, zone "C", in which the resulting pyrolysis gas cools down so that a benzoic acid- and / or terephthalic acid-containing material is deposited, can either be part of the pyrolysis reactor itself or a separate component of the pyrolysis apparatus. However, it is preferred according to the invention that zone "C", in which the resulting pyrolysis gas cools down so that a benzoic acid- and / or terephthalic acid-containing material is deposited, begins within the pyrolysis reactor but continues in a separate component of the pyrolysis apparatus.

[0079] In the first case, where the pyrolysis reactor has two zones, the two zones can in principle be separated from each other in the interior of the reactor by a wall or some other measure; however, according to the invention, it may also be preferred if the two zones “A” and “C” are directly adjacent to each other without physical separation.

[0080] According to the invention, it is particularly preferred if zone "C" is a completely separate component of the pyrolysis apparatus. Preferred examples of such a separate component according to the invention are an air cooler or an active cooling device, in particular a cold trap. If the pyrolysis apparatus includes a dephlegmator as zone "D" as a separate component, it is essential that zone "C" is arranged downstream of the dephlegmator (zone "D") in the gas stream. The pyrolysis gas formed in the melt of the PET-containing material (lower region of the pyrolysis reactor in zone "A") thus flows first through zone "D" and only then into zone "C".

[0081] It has proven to be preferable according to the invention if zone “C” has a temperature of 120 to 170 °C. P45576PC00 / XII / XII 10.11.2025

[0082] 14

[0083] According to the invention, the temperature of zones “A”, “D”, and “C” is preferably measured in the center of each zone. In any case, however, the temperature must be determined in an area sufficiently far from any heating and / or cooling elements present in the respective zones to avoid distortions caused by the temperature gradient resulting from the heating / cooling.

[0084] In cases where zone “D” and / or zone “C” are completely or at least partially separate components of the pyrolysis apparatus, it is essential that the transfers between the pyrolysis reactor and the separate component are heated accordingly, so that premature cooling of the pyrolysis gas and / or the condensate and thus separation of the benzoic acid and / or terephthalic acid-containing material is avoided.

[0085] In this context, it may be preferred according to the invention if the transitions between the pyrolysis reactor and the optional zone “D” or between the pyrolysis reactor and zone “C” are tempered to temperatures of at least 400 °C; when using a support gas stream, it may be preferred if the transitions between the pyrolysis reactor and the optional zone “D” or between the pyrolysis reactor and zone “C” are tempered such that the saturation vapor pressure of benzoic acid is not undershot.

[0086] In this context, it may be further preferred according to the invention if the transition between the optional zone “D” and zone “C” is tempered to temperatures of at least 200 °C; when using a support gas stream, it may be preferred if the transition between the optional zone “D” and zone “C” is tempered such that the saturation vapor pressure of benzoic acid is not undershot. P45576PC00 / XI 1 / XI I 10.11.2025

[0087] 15

[0088] In addition to the two or three zones essential according to the invention, further zones can be provided both in the actual pyrolysis reactor itself and in the pyrolysis apparatus.

[0089] According to the invention, a PET-containing material is understood to be a material containing at least 30 wt.% PET, in particular at least 40 wt.% PET, and most preferably 50 to 100 wt.% PET. However, materials with a PET content in the range of 40 to 80 wt.%, in particular 45 to 60 wt.%, can also be used preferentially according to the invention.

[0090] One particularly preferred PET-containing material is an adhesive tape comprising a PET-containing carrier that is provided with an adhesive layer on at least one side.

[0091] Although such adhesive tapes are not subject to any restrictions in principle, according to the invention, adhesive tapes with a PET-containing carrier with a basis weight of up to 300 g / m² may be preferred. 2 , especially from 70 to 130 g / m² 2 , and an adhesive layer with a basis weight of up to 300 g / m² 2 , especially from 80 to 100 g / m² 2exhibit.

[0092] The adhesive layer is preferably a pressure-sensitive adhesive (PSA). Although the pressure-sensitive adhesive can in principle be formed from many different materials, according to the invention it has proven advantageous if the pressure-sensitive adhesive is based on acrylates and / or natural and / or synthetic rubber resins.

[0093] The acrylates used in the adhesive layers according to the invention are preferably copolymers of (meth)acrylic acid and its esters with 1 to 25 carbon atoms, maleic, fumaric and / or itaconic acid and / or their esters, substituted (meth)acrylamides, maleic anhydride and other vinyl compounds, such as vinyl esters, in particular vinyl acetate, vinyl alcohol and / or vinyl ethers. P45576PC00 / XI 1 / XI I 10.11.2025

[0094] 16

[0095] Depending on the application, the acrylates are preferably used as acrylate acetate polymers and / or as UV-crosslinkable hot melt acrylates and / or as dispersion acrylates and / or as solvent medium acrylates, whereby radiation-induced crosslinking can take place in all cases.

[0096] In an acrylate mass polymer, acrylate monomers and / or oligomers are applied and subsequently polymerized by UV initiation. It has proven advantageous to crosslink the acrylate mass polymers to form the pressure-sensitive adhesive according to the invention. Conventional crosslinking methods can be employed, for example, by thermal activation, by irradiation, for example, by UV radiation or electron beam radiation (E-beam). Crosslinking by UV radiation is particularly preferred according to the invention.

[0097] According to the invention, UV-curable hot-melt acrylates are understood to be UV-curable low-molecular-weight acrylate polymers that are applied as a melt and cross-linked by means of UV radiation. It has proven advantageous if the UV-curable acrylate polymers either already contain an incorporated photoinitiator or if a photoinitiator is added separately to the melt. Corresponding UV-curable low-molecular-weight acrylate polymers, which have proven particularly suitable, are commercially available, for example, under the name acResin® UV from BASF.

[0098] Preferably, pressure-sensitive adhesives based on acrylate hot melts may be used, optionally incorporating benzoin derivatives such as benzoin acrylate or benzoin methacrylate, as well as corresponding acrylic acid or methacrylic acid esters. Such benzoin derivatives are described in EP 0578 151 A. The acrylate hot melt-based adhesive can be UV-cured. However, other curing methods are also possible, for example...

[0099] Electron beam crosslinking. P45576PC00 / XI 1 / XI I 10.11.2025

[0100] 17

[0101] Dispersion acrylates, particularly aqueous dispersion acrylates, have also proven suitable. In this process, acrylate polymers are applied from a dispersion, and the dispersion medium is then removed. Crosslinking of dispersion acrylates can also be achieved, for example, by adding thermally activated initiators such as carbodiimide crosslinkers. Such dispersion acrylates are commercially marketed, for example, under the trade name Acronal® by BASF.

[0102] Medium acrylates have also proven advantageous as solvents. In this process, acrylate polymers dissolved in a solvent, particularly an organic solvent, are applied, and the solvent is then removed. Crosslinking can also occur with medium acrylate solvents.

[0103] According to the invention, UV-crosslinkable hot melt acrylates and / or aqueous dispersion acrylates are particularly preferred.

[0104] For synthetic rubber resins, it has proven advantageous to select them from ABA-type block copolymers, wherein block A is a derivative of a styrene monomer and block B is a derivative of an isoprene or butadiene monomer or their hydrogenated variants.

[0105] Furthermore, isobutene-isoprene block copolymers (butyl rubbers) have proven to be a preferred adhesive layer. Natural rubbers can also be used as adhesives in the adhesive tape rolls according to the invention.

[0106] In the context of the present invention, it is particularly advantageous if the adhesive layer

[0107] - an acrylate adhesive, in particular a UV-curable hot melt acrylate, a dispersion acrylate, in particular an aqueous dispersion acrylate, a solvent medium acrylate and / or an acrylate mass polymer,

[0108] - a styrene-isoprene-styrene block copolymer (SIS), P45576PC00 / XI 1 / XI I 11 / 10 / 2025

[0109] 18

[0110] - a styrene-butadiene-styrene block copolymer (SBS) and / or

[0111] - an isobutene-isoprene block copolymer (butyl rubber)

[0112] contains.

[0113] Other preferred PET-containing materials that can be used as starting materials in the process according to the invention are, preferably according to the invention, PET bottles, PET-containing packaging, PET-containing textiles, PET-containing compounds (films), PET-containing foams, and other PET-containing waste. PET-containing foams coated with layers of other plastics, for example, with end-group esterified polyethylene glycols, can also preferably be used in the process according to the invention.

[0114] Within the framework of the process according to the invention, depending on the reactants used, material containing benzoic acid and / or terephthalic acid can be obtained with a high yield and purity. Particularly preferably, upon cooling of the pyrolysis gas, the material containing benzoic acid and / or terephthalic acid is deposited in zone "C" as a solid, in particular as a partially or completely crystalline solid.

[0115] According to the invention, it is preferred if the benzoic acid and / or terephthalic acid-containing material has a benzoic acid content of at least 20 wt.%, in particular at least 55 wt.%, more preferably at least 70 wt.%, and most preferably at least 85 wt.%, in each case based on the mass of the entire benzoic acid and / or terephthalic acid-containing material. With high purity of the PET-containing material used, it is also possible according to the invention to obtain benzoic acid and / or terephthalic acid-containing material with a benzoic acid content of more than 90 wt.% based on the mass of the entire benzoic acid and / or terephthalic acid-containing material.

[0116] Although the recovered benzoic acid and / or terephthalic acid-containing material is already characterized by good purity, it can be further processed according to the invention P45576PC00 / XI 1 / XI I 10.11.2025

[0117] 19

[0118] It would be preferable to separate the benzoic acid and / or terephthalic acid-containing material in a subsequent step using conventional methods and to purify the resulting products so that benzoic acid and terephthalic acid are each present separately in sufficient purity to be used as raw materials in further industrial processes.

[0119] The process according to the invention is characterized in particular by its broad applicability and simplicity, and it is possible according to the invention to successfully recycle PET-containing material regardless of the presence and nature of other accompanying substances. Thus, it is preferably possible to dispense with complex cleaning or mechanical separation of other components of the PET-containing material used. For example, it is not necessary to remove labels and screw caps from PET bottles or layers of other plastics from composite materials. PET-containing materials reinforced with fibers made of other materials can also preferably be used in the process according to the invention without prior processing.

[0120] In the process according to the invention, it may be preferred if the PET-containing material is mechanically comminuted in a preliminary step before melting. According to the invention, it is not essential whether the PET-containing material is subsequently added to the pyrolysis reactor in an already molten state or whether it is melted only in the pyrolysis reactor itself.

[0121] While in the prior art processes for the pyrolytic processing of PET, specially selected catalysts are often added, according to the invention it has proven preferable if the melt of the PET-containing material is largely free of added catalysts.

[0122] According to the invention, "largely free of added catalysts" means a content of less than 0.1 wt.% of added catalyst, based on P45576PC00 / XI 1 / XI I 10.11.2025

[0123] 20

[0124] The mass of PET-containing material used is to be understood as the total mass. A process in which less than 0.01 wt% catalyst is added, based on the mass of PET-containing material used, is particularly preferred. A process in which the amount of added catalyst is less than 0.001 wt%, based on the mass of PET-containing material used, is especially preferred. However, a process in which no effective amount of catalyst is added, or even in which the melt is completely free of added catalysts (0.0 wt%), is particularly preferred.

[0125] In addition to the use of catalysts, fluidized bed reactors have frequently been proposed in the past for the pyrolysis of PET-containing materials. In contrast, the process according to the invention allows high yields of benzoic acid and / or terephthalic acid-containing material to be achieved without the use of the solid particle beds characteristic of fluidized bed reactors, in particular without the use of solid particle beds that are fluidized by means of an upward gas flow.

[0126] The same applies to the addition of solvents. For example, prior art describes pyrolysis processes in which the PET-containing material is mixed with solvents and introduced into the pyrolysis reactor; it has even been described to place pure high-boiling oils in the pyrolysis furnace and then gradually add the PET-containing material to be pyrolyzed.

[0127] In contrast to these prior art methods, it has proven to be preferred according to the invention if the melt of the PET-containing material in the pyrolysis reactor is largely free of added solvents, in particular largely free of added organic solvents.

[0128] According to the invention, "largely free of added solvents" means a solvent content of less than 5% by weight, based on the mass of PET-containing material used. A process in which less than 1% by weight of solvent is used is particularly preferred. P45576PC00 / XI 1 / XI I 10.11.2025

[0129] 21

[0130] a solvent is added to the PET-containing material used. A process in which the content of added solvent is less than 0.1 wt%, based on the mass of PET-containing material used, is particularly preferred. However, a process in which no effective amount of solvent is added or even the melt is completely free of added solvents (0.0 wt%) is especially preferred.

[0131] Furthermore, it has proven advantageous if the melt of the PET-containing material is largely free of added additives. Additives are defined as all components added to the PET-containing material to influence the pyrolysis process.

[0132] According to the invention, "largely free of added additives" means a content of less than 10 wt.% of added additives, based on the mass of PET-containing material used. A process in which less than 4 wt.% additives are added, based on the mass of PET-containing material used, is particularly preferred. A process in which the content of added additives is less than 0.1 wt.%, based on the mass of PET-containing material used, is especially preferred. However, a process in which no effective amount of an additive is added or in which the melt is completely free of added additives (0.0 wt.%) is particularly preferred.

[0133] Within the scope of the present invention, it has proven advantageous that the PET-containing material is converted almost completely into pyrolysis gases and pyrolysis coke. Depending on the specific conditions, however, it is also possible that small amounts of a liquid phase, the so-called pyrolysis oil, are formed. According to the invention, it is preferred if less than 30 wt% pyrolysis oil, based on the mass of the PET-containing material used, is formed, in particular less than 10 wt% pyrolysis oil, based on the mass of the PET-containing material used, and most preferably less than 5 wt% pyrolysis oil, based on the mass of the PET-containing material used. P45576PC00 / XII / XII 10.11.2025

[0134] 22

[0135] containing material. The pyrolysis oil remains at the bottom of the pyrolysis reactor.

[0136] Although the pyrolysis process according to the invention can, in principle, proceed completely independently if the temperature is controlled accordingly, it may also be preferred if the residence time of the pyrolysis gas produced in zone “A” in the pyrolysis reactor and / or in zone “D” is adjusted by means of an inert support gas stream, in particular a nitrogen and / or steam stream.

[0137] An "inert support gas stream" refers to the introduction of an inert gas into the pyrolysis reactor, ensuring gas exchange within the reactor so that the resulting pyrolysis gas is at least partially displaced. The residence time of the resulting pyrolysis gas in the pyrolysis reactor can be controlled by adjusting the volume flow rate of inert support gas, measured in liters of support gas introduced per minute.

[0138] In a preferred form, the residence time of the pyrolysis gas generated in zone “A” can refer to the entire pyrolysis reactor; in another, equally preferred form, the residence time of the pyrolysis gas generated in zone “A” can also describe the time during which the pyrolysis gas generated in zone “A” resides in the zones of the pyrolysis reactor and / or the pyrolysis apparatus where temperatures of at least 300 °C prevail.

[0139] It may be preferred to set a residence time of at least 3 seconds for the pyrolysis gas generated in zone "A" in the pyrolysis reactor or in the zones of the pyrolysis reactor and / or the pyrolysis apparatus where temperatures of at least 300 °C prevail. In this case, according to the invention, benzoic acid-containing material can be obtained with high yield and purity, containing only minor amounts of terephthalic acid. P45576PC00 / XI 1 / XI I 10.11.2025

[0140] 23

[0141] exhibits. However, it may also be preferable to deliberately set shorter residence times (less than 3 see) of the pyrolysis gas generated in zone "A" in the pyrolysis reactor or in the zones of the pyrolysis reactor and / or the pyrolysis apparatus where temperatures of at least 300 °C prevail. In this case, higher yields of terephthalic acid and only negligible amounts of benzoic acid are achieved.

[0142] Furthermore, according to the invention, it may also be preferred to modify the process for producing a benzoic acid and / or terephthalic acid-containing material more towards benzoic acid production or towards terephthalic acid production by means of an inert support gas stream. It may also be preferred to use a change in the volume flow rate of the inert support gas to switch from a process for producing benzoic acid-containing material to a process for producing terephthalic acid-containing material and vice versa.

[0143] A second preferred embodiment of the present invention relates to a process for the pyrolytic production of benzoic acid from PET-containing materials, in which

[0144] - a melt of PET-containing material is located in a zone “A” in the lower region of a pyrolysis reactor at a temperature of 350 to 750 °C, in particular 380 to 600 °C, most preferably 400 to 500 °C, and

[0145] - the resulting pyrolysis gas cools down in a zone “C”, so that a solid benzoic acid-containing material is deposited, whereby

[0146] - the resulting pyrolysis gas first flows through a zone "D" before reaching zone "C", in which at least part of the resulting pyrolysis gas condenses, and the remaining pyrolysis gas flows into zone "C" of the pyrolysis apparatus, and

[0147] - at least part of the condensate is returned to the flowing pyrolysis gas within pyrolysis reactor 1 and again P45576PC00 / XI 1 / XI I 10.11.2025

[0148] 24

[0149] is fed to the pyrolysis process, and any remaining condensate flows into zone “C” of the pyrolysis apparatus.

[0150] Regarding the further details of this second preferred embodiment of the present invention, the descriptions of the other embodiments of the present invention apply mutatis mutandis, as far as applicable.

[0151] In a third preferred embodiment of the present invention, the pyrolytic production of benzoic acid from PET-containing materials takes place in a pyrolysis apparatus having at least three zones, wherein

[0152] - a zone “A” containing a melt of the PET-containing material at a temperature of 350 to 750 °C, in particular of 380 to 600 °C, most preferably of 400 to 500 °C, and located in the lower region of a pyrolysis reactor,

[0153] - a zone “B” has a temperature of 300 to 350 °C and is directly adjacent to the surface of the melt in the pyrolysis reactor, and - a zone “C” of the pyrolysis apparatus has a lower temperature than zone “B”,

[0154] and wherein the pyrolysis gas formed in zone “A” remains in zone “B” for at least 3 seconds and then flows into zone “C”, depositing a benzoic acid-containing material in zone “C”.

[0155] In this embodiment, at least two zones are defined that are located within the pyrolysis reactor.

[0156] Firstly, the pyrolysis reactor has a zone "A" containing the PET-containing melt. This zone is located in the lower part of the pyrolysis reactor and preferably occupies a volume of no more than 80%, particularly no more than 70%, and most especially no more than 65%. P45576PC00 / XII / XII 10.11.2025

[0157] 25

[0158] Furthermore, the pyrolysis reactor has a zone "B" located directly above zone "A" and adjacent to the surface of the melt. During the pyrolysis reaction, this zone contains a gas phase at a temperature of 300 to 350 °C, wherein the gas is preferably essentially pyrolysis gas, additionally containing smaller amounts of gaseous pyrolysis oil and optionally support gas. According to the invention, a content of at least 50 wt.% pyrolysis gas, in particular at least 75 wt.% pyrolysis gas, and most preferably at least 85 wt.% pyrolysis gas, in each case based on the mass of the total gas phase in zone "B", is particularly preferred.

[0159] Zone “C” of the pyrolysis apparatus used in the process according to the invention, in which the benzoic acid-containing material is deposited, can either be part of the pyrolysis reactor itself or a separate component of the pyrolysis apparatus. However, according to the invention, it is also possible for zone “C”, in which the benzoic acid-containing material is deposited, to begin within the pyrolysis reactor itself and continue in a separate component of the pyrolysis apparatus. Preferred examples of such a separate component according to the invention are a condenser or a dephlegmator.

[0160] In the event that zone “C” is located wholly or partially in a separate component of the pyrolysis apparatus, it is essential according to the invention that the transfers between the pyrolysis reactor and the separate component are heated accordingly, so that premature cooling of the pyrolysis gas and thus separation of the benzoic acid-containing material is avoided.

[0161] It has proven to be preferred according to the invention if this zone “C” has a temperature of 120 to 170 °C.

[0162] According to the invention, the temperature of zones “A”, “B”, and “C” is preferably measured in the center of each zone. In any case, however, the temperature must be determined in an area sufficiently far from any potentially heated areas. P45576PC00 / XI 1 / XI I 10.11.2025

[0163] 26

[0164] walls of the pyrolysis reactor are removed to avoid adulteration caused by the temperature gradient resulting from the heating.

[0165] In this embodiment, in addition to the three essential zones, further zones can be provided both in the actual pyrolysis reactor itself and in the pyrolysis apparatus.

[0166] Without wishing to be bound by this theory, the invention assumes that pyrolytic reactions also take place in zone "B". Therefore, according to the invention, it is preferred if the pyrolysis gas formed in zone "A" remains in zone "B" for at least 3 seconds and then flows into zone "C", where a benzoic acid-containing material is deposited.

[0167] Residence times of at least 5 seas, particularly at least 10 seas, may still be preferred. A residence time in the range of 3 to 50 seas is particularly preferred, especially 5 to 30 seas, and most particularly preferably 10 to 15 seas.

[0168] Although the pyrolysis process according to the invention can, in principle, proceed completely independently if the temperature is controlled accordingly, it may be preferred in this embodiment if the residence time of the pyrolysis gas produced in zone “A” in zone “B” is adjusted by means of an inert support gas stream, in particular a nitrogen and / or hydrogen stream.

[0169] By appropriately controlling the residence time, benzoic acid-containing material with high yield and purity can be obtained according to the invention, exhibiting only negligible amounts of terephthalic acid. Conversely, higher terephthalic acid yields are achieved with shorter residence times (less than 3 sec).

[0170] Particularly preferably, upon cooling of the pyrolysis gas, the benzoic acid-containing material is deposited as a solid, especially as a crystalline solid. A deposit of the benzoic acid in the form of colorless, shiny flakes and especially in the form of needle-shaped crystals is particularly preferred. P45576PC00 / XI 1 / XI I 10.11.2025

[0171] 27

[0172] What has been said about the first embodiment applies mutatis mutandis to this embodiment.

[0173] Regardless of the chosen embodiment of the present invention, the pyrolysis reactor used in the process according to the invention can be operated both discontinuously (batch process) and continuously.

[0174] In a batch-operated pyrolysis reactor, it has proven advantageous to homogenize the PET-containing melt in zone "A" during the pyrolysis process. This can preferably be achieved using a stirrer.

[0175] In the case of a continuously operated pyrolysis reactor, it has also proven advantageous to mix the PET-containing melt in zone "A". To further ensure a continuous feed and conveyance of the PET-containing melt, the use of a screw conveyor in zone "A" of the continuously operated reactor has proven beneficial.

[0176] Further advantageous embodiments of the invention will become apparent from the following description of the figures and the dependent subclaims.

[0177] They show:

[0178] Fig. 1 is a schematic sketch of a batch reactor according to the invention,

[0179] Fig. 2 is a schematic sketch of the side view of a continuously operated reactor according to the invention, and

[0180] Fig. 3 is a schematic sketch of the front view of a continuously operated reactor according to the invention. P45576PC00 / XI 1 / XI I 10.11.2025

[0181] 28

[0182] In the various figures of the drawing, identical parts are always labelled with the same reference symbols.

[0183] The following description claims that the invention is not limited to the exemplary embodiments and not to all or several features of the described combinations of features; rather, each individual partial feature of the exemplary embodiment(s) is also significant for the subject matter of the invention, independent of all other partial features described in connection therewith, both on its own and in combination with any features of another exemplary embodiment.

[0184] Figure 1 shows a side view of a reactor 1a during operation, which is suitable for the batch version of the process according to the invention. The reactor 1a has a heated outlet 4, from which the pyrolysis gas escapes during operation and is directed to a cooler 6. In zone “A” in the lower part of the reactor 1a is the melt of the PET-containing material 2, preferably PET-containing adhesive tape residues. This is preferably homogenized by means of an agitator 3. Above the melt 2, the reactor 1a has a space in which the pyrolysis gases collect.

[0185] Figure 2 shows a side view of a reactor 1b suitable for the continuous version of the process according to the invention. A screw conveyor 5 is located in the lower part of the reactor 1b, continuously conveying the melt of the PET-containing material 2 from the sluice 7 into the heated section of the reactor 1b. The reactor 1b has a heated outlet 4, from which the pyrolysis gas escapes during operation and is directed to a cooler 6. Furthermore, the reactor 1b has a discharge opening 8 through which the resulting pyrolysis coke and any high-boiling pyrolysis oil produced are removed from the reaction zone. As can be seen from the front view of a continuously operated reactor 1b according to the invention in Figure 3, the screw conveyor 5 is located in zone P45576PC00 / XI 1 / XI I 10.11.2025

[0186] 29

[0187] “A” is located in the lower section of reactor 1b, while above screw conveyor 5 there is an area where the pyrolysis gases collect. P45576PC00 / XI 1 / XI I 10.11.2025

[0188] 30

[0189] Examples of implementation

[0190] Unless otherwise stated, the following information is given in wt.%.

[0191] Experiment 1: Pyrolysis of pure PET (laboratory scale)

[0192] Three grams of pure PET granules (at room temperature) were added to a pyrolysis reactor preheated to 450 °C with a volume of 0.39 liters (the height of the interior was approximately 15.5 cm). The granules accumulated in the lower part of the reactor (Zone A).

[0193] After a drop in the reactor's internal temperature in zone "A", a stable temperature plateau was established in the range of 370 °C to 410 °C (temperature measured using a temperature sensor approximately 6.5 cm above the bottom of the pyrolysis reactor). During this period, the release of pyrolysis gas from the molten PET granules was observed.

[0194] After the pyrolysis reaction ended, the temperature in zone “A” of the reactor rose sharply, with small amounts of carbon being formed.

[0195] Accordingly, in a further, otherwise identical attempt, the process was aborted as soon as the temperature in zone “A” of the reactor had left the plateau level (after approximately 9.5 minutes).

[0196] The escaping pyrolysis gas was directed through a gas outlet into a cooler, where a benzoic acid-containing solid was deposited, containing large quantities of benzoic acid as well as terephthalic acid. The formation of a liquid phase (pyrolysis oil) was not observed. The remaining pyrolysis coke was removed from the batch reactor after the reaction was complete.

[0197] Based on the PET granules used, a 43 wt% yield of benzoic acid-containing solid was achieved, comprising 89 wt% benzoic acid and 6 wt% P45576PC00 / XI 1 / XI I 10.11.2025

[0198] 31

[0199] Terephthalic acid was detected (measured by gas chromatography-mass spectrometry coupling (GCxMS); for quantitative estimation, the method was transferred to gas chromatography with flame ionization detection (GCxFID)).

[0200] Experiment 2: Pyrolysis of a commercially available adhesive tape with a PET backing (laboratory scale)

[0201] Using the same apparatus as in Experiment 1, 120 g of Coroplast adhesive tape (837X) were pyrolyzed. This tape consists of a PET fabric, a solvent-free acrylate adhesive, and a cardboard core. Before being placed in the reactor, the PET-containing tape was first crushed (resulting particle size in the range of 1 to 2 cm). 2 ) to reduce the volume.

[0202] In this experiment as well, the formation of a temperature plateau in the range of 370 to 410 °C and a strong development of smoke (benzoic acid-containing pyrolysis gas) were observed, and the experiment was terminated as soon as the temperature left the plateau range.

[0203] The invention is not limited to the embodiments shown and described, but also includes all embodiments that have the same effect within the meaning of the invention. It is expressly emphasized that the embodiments are not limited to all features in combination; rather, each individual feature can also have inventive significance independently of all other features. Furthermore, the invention is not yet limited to the combination of features defined in claim 1, but can also be defined by any other combination of specific features from all disclosed individual features. This means that, in principle, virtually any individual feature of claim 1 can be omitted or replaced by at least one individual feature disclosed elsewhere in the application. P45576PC00 / XI 1 / XI I 10.11.2025

[0204] 32

[0205] List of reference signs

[0206] 1 a Reactor for the batch process according to the invention 1 b Reactor for the continuous process according to the invention 2 Melt of the PET-containing material

[0207] 3 Agitator

[0208] 4 heated outlets

[0209] 5 screw conveyors

[0210] 6 coolers

[0211] 7 Lock

[0212] 8 Discharge opening

Claims

P45576PC00 / XII / XII 10.11.2025 33 Claims 1. Process for the pyrolytic production of benzoic acid and / or terephthalic acid from PET-containing materials, characterized by the fact that - a melt of a PET-containing material 2 is located in a zone “A” in the lower region of a pyrolysis reactor 1 at a temperature of 350 to 750 °C, in particular of 380 to 600 °C, most preferably of 400 to 500 °C, and - the resulting pyrolysis gas cools down in a zone “C”, so that a material containing benzoic acid and / or terephthalic acid is deposited.

2. Method according to claim 1 , characterized by the fact that - the resulting pyrolysis gas first flows through a zone "D" before reaching zone "C", in which at least part of the resulting pyrolysis gas condenses, and the remaining pyrolysis gas flows into zone "C" of the pyrolysis apparatus, and - at least part of the condensate is returned to the flowing pyrolysis gas within the pyrolysis reactor 1 and fed back into the pyrolysis process, and any remaining condensate flows into zone “C” of the pyrolysis apparatus.

3. Method according to claim 2, characterized in that the zone “D” is located in a cooler zone of the pyrolysis reactor 1 and / or in a separate component, in particular in a downstream dephlegmator.

4. Method according to one of claims 2 or 3, characterized in that zone “D” has a temperature in the range of 125 to 250 °C, in particular in the range of 130 to 200 °C. P45576PC00 / XI 1 / XI I 11 / 10 / 2025 34 5. Method according to any one of claims 2 to 4, characterized in that zone “D” has a volume that is larger than the volume of the melt of the PET-containing material.

6. Method according to any one of claims 2 to 5, characterized in that the part of the resulting pyrolysis gas which flows in gaseous form from zone “D” into zone “C” of the pyrolysis apparatus contains at least 25 wt% benzoic acid.

7. Method according to claim 6, characterized in that the reflux rate of the benzoic acid contained in the resulting pyrolysis gas is in a mass ratio of 1 : 1 to 1 : 10 (wt% benzoic acid that is transferred directly from zone “D” as part of the gas and / or optionally the condensate to zone “C” : wt% benzoic acid that is returned to the pyrolysis area from zone “D” as part of the condensate).

8. Method according to any one of claims 2 to 7, characterized in that the returning condensate within the pyrolysis reactor 1 picks up precipitated, solid intermediate products and feeds them back into the pyrolysis process.

9. Method according to any one of claims 2 to 8, characterized in that the returning condensate contains at least 1 wt.% terephthalic acid, in particular at least 5 wt.% terephthalic acid.

10. Method according to any one of claims 1 to 9, characterized in that solid intermediate products deposited within the pyrolysis reactor 1 are mechanically fed back into the pyrolysis process. P45576PC00 / XI 1 / XI I 11 / 10 / 2025 35 11. Method according to any one of claims 1 to 10, characterized in that the PET-containing material contains at least 30 wt.% PET, in particular at least 40 wt.% PET, most preferably 50 to 100 wt.% PET.

12. Method according to any one of claims 1 to 11, characterized in that the PET-containing material is an adhesive tape comprising a PET-containing carrier which is provided with an adhesive layer on at least one side.

13. Method according to any one of claims 1 to 12, characterized in that the benzoic acid and / or terephthalic acid-containing material deposited in zone “C” contains at least 55 wt.% benzoic acid, in particular at least 70 wt.% benzoic acid, and most preferably at least 85 wt.% benzoic acid.

14. Method according to any one of claims 1 to 13, characterized by the fact that the melt of the PET-containing material is largely free of added catalysts.

15. Method according to any one of claims 1 to 14, characterized by the fact that the melt of the PET-containing material is largely free of added solvents.

16. Method according to any one of claims 1 to 15, characterized by the fact that the melt of the PET-containing material is largely free of added additives.

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