A method and system for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of pet and method for recycling a sample of polyethylene terephthalate (PET)

Abstract

A method for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET, wherein the first type of PET is defined by comprising a marker additive with a content CM1 higher than a preset limit L: CM1 > L, and the second type of PET is defined by comprising no marker additive or the marker additive in a content CM2 less than or equal the preset limit L: 0 ≤ CM2 ≤ L, and wherein the marker additive is: Calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate], with the steps: a) providing (101) a sample comprising at least one of the two types of PET; b) acquiring (102) at least one spectrum of the sample distinctive for the marker additive using a near-infrared (NIR) spectrometer device; c) determining (103) a content CM of the marker additive in the sample based on an evaluation of at least one part from the at least one spectrum; and d) classifying (104) the sample depending on the determined content CM into the first type of PET when: CM > L or into the second type of PET when 0 ≤ CM ≤ L. (Fig. 1)

Description

[0001] A METHOD AND SYSTEM FOR CLASSIFYING A SAMPLE OF POLYETHYLENE TEREPHTHALATE (PET) INTO A FIRST AND A SECOND TYPE OF PET AND METHOD FOR RECYCLING A SAMPLE OF POLYETHYLENE

[0002] TEREPHTHALATE (PET)

[0003] DESCRIPTION

[0004] FIELD OF THE INVENTION

[0005] The invention relates to a method and a system for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET. The invention further relates to a method for recycling of PET. Further fields of application of the present invention may be feasible.

[0006] PRIOR ART

[0007] The production of plastics continues to increase globally. Plastics applications, ranging from food contact materials (FCM) to automotive, from electrical equipment to consumer products, including flexible films, plastic bags, trays, cups and containers, but also coatings, labels and glues.

[0008] Polyethylene terephthalate (PET) is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fiber for engineering resins.

[0009] In 2022, the global PET (fiber and resins) capacity stood at 81 million tons with PET fiber accounting for over 65% of the total PET market while PET resins accounts for the remaining share. PET resins are widely used in the production of plastic bottles and packaging materials. The beverage and packaging industries heavily rely on PET resins due to their transparency, lightweight nature, and the ease with which they can be molded into various shapes. PET fibers on the other hand, are spun into threads and woven into fabrics for clothing, carpets, and a variety of other textile products. PET consists of repeating (C10H8O4) units. Depending on its processing and thermal history, PET may exist both as an amorphous (transparent) and as a semi-crystalline polymer. The semicrystalline material might appear transparent (particle size less than 500nm) or opaque and white (particle size up to a few micrometers) depending on its crystal structure and particle size.

[0010] There are two types of PET: so-called "virgin PET" (vPET) is made from crude oil, which is a finite raw material. But there is also recycled PET (rPET), which is made from PET material, e.g. PET fibers of used textiles or PET bottles etc. The problem is that recycled PET (rPET) is typically not only more expensive to buy, it is also chemically indistinguishable from virgin PET (vPET). Further, there are also growing regulatory requirements to include a defined quantity of recycled content, or be subject to fees / taxes. The potential for abuse is therefore great: fraudsters can simply label and sell the cheaper vPET as the more environmentally friendly rPET and thus demand more money and / or save taxes. It is therefore in the interest of both manufacturers and purchasers to prove that their products are actually made from recycled PET (rPET).

[0011] Today PET is also recognized as the most circular plastic food contact material (FCM) and even suitable to be recycled back into new primary FCMs almost endlessly, because

[0012] • the rate of diffusion of chemical substances in PET is generally very low, thus the risk of migration of chemical contaminants from the packaging into the food is minimized,

[0013] • its high recyclability potential due to a combination of intrinsic unique material properties that allow it to be mechanically recycled, almost endlessly, and

[0014] • compared to other polymers, its limited need to use chemical additives during its conversion, resulting in a decreased risk of finding cross-contaminants in recycled PET (rPET) if it's appropriately sorted in waste facilities.

[0015] To promote global sustainability in the plastics industry more and more regions / countries are beginning to set legally binding targets for the recycled content in plastics. For example, the EU Green Deal action plan (European Commission, 2019) includes goals, such as the reduction of single use plastic and plastic waste, improved circularity, increase of reuse and recycling.

[0016] Based on those regulatory requirements, the plastic industry is seeking a way to mark and detect the recycled content in plastic applications to allow verification / certification that the sample in use is in fact recycled, and thus contributes positively to a circular economy for plastics, without compromising the quality of the recycled plastics.

[0017] PROBLEM ADDRESSED BY THE INVENTION

[0018] Therefore, a problem addressed by the present invention is that of providing a method and a system for classifying a sample of PET into a first and a second type of PET, especially into already recycled polyethylene terephthalate (rPET) as the first type of PET and virgin polyethylene terephthalate (vPET) as the second type of PET, which also enable an on-site and non-destructive analysis of a PET sample as well as a reliable and robust classification into the two types of PET.

[0019] Another problem addressed by the present invention is that of providing an appropriate substance usable as marker additive in PET for reliably marking and detecting an rPET content in a PET plastic sample without the marker compromising the quality of the rPET and for classifying a PET sample into a first and a second type of PET.

[0020] Another problem addressed by the present invention is that of providing a method for recycling of PET samples. SUMMARY OF THE INVENTION

[0021] The problems described above are solved by the present invention, with the features of the independent patent claims. Advantageous embodiments of the invention, which can be implemented individually or in combination, are presented in the dependent claims and / or in the following specification.

[0022] The first aspect of the invention relates to a method for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET, wherein the first type of PET is defined by comprising a marker additive with a content CMI higher than a preset limit L: CMI > L, and the second type of PET is defined by comprising no marker additive or the marker additive in a content CM2 less than or equal the preset limit L: 0 < CM2 L, and wherein the marker additive used is:

[0023] Calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate], with the steps: a) providing a sample comprising at least one of the two types of PET; b) acquiring at least one spectrum of the sample distinctive for the marker additive using a near-infrared spectrometer (NIR) device; c) determining a content CM of the marker additive in the sample based on an evaluation of at least one part from the at least one spectrum; and d) classifying the sample depending on the determined content CM into the first type of PET when: CM > L or into the second type of PET when 0 < CM < L.

[0024] Further, additional steps might be provided which are not listed.

[0025] The proposed method allows a reliable and robust classification of a PET sample into the first type of PET and a second type of PET.

[0026] The proposed method is based on the application of calcium diethyl bis[[[3,5-bis(1 , 1 -dimethylethyl)-4- hydroxyphenyl]methyl]phosphonate] as the marker additive. Well known synonyms of this substance are: Phosphonic acid, [[3,5-bis(1 , 1 -dimethylethyl)-4-hydroxyphenyl]methyl]-, monoethyl ester, calcium salt (2:1) or CAS 65140-91-2 or IRGANOX1425. This substance hereinafter is referred to as "IRGANOX1425” for short.

[0027] The proposed method especially allows a classification of a PET sample into virgin PET (vPET) and into recycled PET (rPET) supposing the marker additive is introduced during the recycling process and the production of rPET and thus leaving an optical fingerprint.

[0028] The use of IRGANOX1425 as marker additive for marking recycled PET (rPET) in the proposed method is specifically based on the following. First, virgin PET contains very few, or no additives, which would interfere with a near infrared spectrum of virgin PET. Second, up to now IRGANOX1425 is not used in any PET application. Third, the calcium / phosphate ions of IRGANOX1425 are highly detectable by NIR infrared spectroscopy. On top of that, inventors found out that IRGANOX1425 suppresses discoloration, supports achievement of desired intrinsic viscosity properties and improves quality consistency and organoleptic properties of recycled PET (rPET). Further IRGANOX1425 supresses the formation of acetaldehyde during recycling, is environmentally friendly and improves the circularity of rPET by increasing the number of times it can be reprocessed before downcycling into fibers. Thus, if IRGANOX1425 is added during recycling of vPET to form rPET, IRGANOX1425 improves the quality of rPET, while also serving as highly reliable and robust tracer, allowing the verification I confirmation of the presence of a recycled rPET content in a sample and thus also allows sample certification as rPET.

[0029] As used herein, the term "providing” refers to an arbitrary step of a method wherein a desired object is made available. Thus, in step a) of the method according to the present invention the sample is made available. Thus, step a) may correspond to a provision step.

[0030] As further used herein, the term "sample” refers to an arbitrary object which, fully or partially, comprises PET. Specifically, the object may have at least one surface, fully or partially, comprising at least one type of PET. The sample may have an arbitrary shape. The samples specifically may be provided as a pellets or flakes.

[0031] As further used herein, the term "polyethylene terephthalate (PET)” refers to an arbitrary PET with repeating (C10H8O4) units. Depending on its processing and thermal history, PET may exist both as an amorphous (transparent) and as a semi-crystalline polymer. The semicrystalline material might appear transparent (particle size less than 500nm) or opaque and white (particle size up to a few micrometers) depending on its crystal structure and particle size.

[0032] As further used herein, the term "virgin PET (vPET)” refers to PET processed from crude oil.

[0033] As further used herein, the term "recycled PET (rPET)” refers to PET, which was at least recycled once.

[0034] As further used herein, the term "content” refers to a mass concentration or a molar concentration or a number concentration or a volume concentration or a mass fraction or molar fraction.

[0035] As outlined above, in step b), the at least one spectrum of the sample is acquired using the at least one near-infrared (NIR) spectrometer device.

[0036] As generally used, the term "spectrum” may refer to the whole electromagnetic spectral range. With a near-infrared (NIR) spectrometer device the near-infrared (NIR) spectral range electromagnetic spectrum may be detected and recorded. Each part of the spectrum may be constituted by an optical signal which may be defined by a signal wavelength or wavenumber or frequency and the corresponding signal intensity / amplitude. As used herein, the term "acquiring” is understood by the skilled person as referring to settling on, concluding on, or ascertaining a fact and / or data. Thus, "acquiring a spectrum” may relate to measuring optical signals, specifically recording, and optionally storing on a suitable storage device, data points representing the optical signal of the nearinfrared spectrometer device. Specifically, the spectrum may be acquired in a NIR-region with a wavelength in the range of 700nm to 2500nm.

[0037] Specifically, step b) may comprise determining, and optionally storing on a storage medium, data points representing an absorption signal, specifically over a wavenumber or wavelength. The acquired at least one spectrum of the sample may especially be provided in digital form, i.e. as digital data, for further use / analysis / evaluation.

[0038] As further used herein, the term acquiring a spectrum "distinctive for the marker additive” refers to acquiring at least one NIR spectrum of the sample, which qualitatively allows an identification of the optical “fingerprint(s)”, i.e. the absorption wavenumber or wavelength which are characteristic for the marker additive.

[0039] The term "absorption” may refer to a common logarithm of a ratio of incident to transmitted radiant power through a material. Specifically, the absorption may refer to a spectral absorption corresponding to a common logarithm of the ratio of incident to transmitted or reflected spectral radiant power through a material.

[0040] As used herein, the term "NIR spectrometer device” may refer to an apparatus which can record the signal intensity with respect to the corresponding wavelength of a NIR spectrum or a partition thereof, such as a wavelength interval, wherein the signal intensity may, preferably, be provided as an electrical signal which may be used for further evaluation. NIR-Light used for the typical purposes of the present invention is light in the NIR spectral range, more preferred having a wavelength of 760nm to 2.5pm, specifically a wavelength in the range of 1400nm to 1600nm.

[0041] As outlined above, in step c), a content CM of the marker additive in the sample is determined based on an evaluation of at least one part from the at least one spectrum distinctive for the marker additive. Step c) may comprise a qualitative and a quantitative analysis of at least one part from the at least one NIR spectrum. The qualitive analysis of the spectrum answers the question, whether the sample comprises the marker additive or not. The quantitative analysis of the spectrum answers the question of how much marker additive is in the sample.

[0042] The qualitative analysis of the at least one NIR spectrum may be based on the fact, that each chemical species - such as the marker additive - has characteristic and unique absorption spectrum specifics ("optical fingerprint”), that can be used for its identification. More precisely, the position of specific absorption peaks and, to some extent, the profile of the peaks of the absorption spectrum allow specific compounds to be qualitatively identified in the sample.

[0043] In particular, the qualitative identification of the marker additive in the sample may be achieved by determining absorption peaks which are characteristic for the marker additive in the absorption spectrum of the sample and comparing the absorption spectrum of the sample with a known spectrum of a PET sample not comprising the marker additive.

[0044] As used herein, the term "peak” refers to at least one local maximum or its derivative of a spectrum. Furthermore, also minima in between the maxima, i.e., the maxima of a negative spectrum, may be fitted. As used herein, the term "determining a peak” refers to an arbitrary process including one or more of a peak detection, a peak finding, a peak identification, a peak fitting, a peak evaluation. Specifically, the term may refer to a qualitative determination of the peak such as a determination of a presence or an absence of the peak and / or to a quantitative determination of the peak such as determining a position of the peak. The peak determination may be an automatic peak determination, i.e. a peak determination performed by at least one computer and / or computer network and / or machine. Specifically, the automatic peak determination may be performed without manual action or interaction with a user. Specifically, in step c) a fitting procedure of at least a part of the spectrum may be performed. Specifically, the fitting procedure may be performed by using at least one mathematical operation and / or mathematical algorithm for determining the peak. Specifically, the fitting procedure may include an application of a second-order polynomial and, specifically, an employing of a zero-crossing point of its first derivative. Specifically, in step c), a peak in a wavelength region between 1400nm to 1600nm, preferred in the region between 1450nm to 1550nm, especially in the region between 1490nm to 1530nm may be determined.

[0045] The quantitative analysis of the at least one spectrum may include determining the amount of NIR radiant flux and its wavelength absorbed by the sample, because the amount of absorbed NIR radiant flux is related to the content of NIR absorbing species, e.g. the content of the marker additive, in the sample.

[0046] The NIR-spectrometer device may by measuring the intensity of Ni R-light passing through the PET sample and comparing it to the intensity of the NI R-light before it passes through the sample. Such a NIR-spectrophotometer device measures transmittance T, which is the ratio of the radiant flux f* transmitted through the sample to the radiant flux frreceived by the sample of NIR-light: T=fr / f*. An important derived (calculated) variable also reported by the instrument is the absorption A which is defined as A= -log (T).

[0047] Generally, a NIR-spectrum may be graphically represented as absorption as a function of wavelength, The advantage of this representation is obvious; the height of the peaks is directly proportional to the content of the absorbing species (i.e. the marker additive) in the sample, The evaluation of the absorbing species content in the sample is governed by the Lambert-Beer Law:

[0048] C = A / ed where:

[0049] C:= content of the absorbing species

[0050] A:= -iog(T) T:= Transmittance d:= thickness of the sample through which NIR light travels

[0051] E:= sample specific constant (describing how much the sample absorbs at a given wavelength).

[0052] In a preferred embodiment of the disclosed method the at least one part from the spectrum is selected such, that this one part is indicative of the marker additive. More specifically, especially because IRGANOX1425 is used as marker additive, the at least one part from the spectrum is selected such, that the wavelength of the at least one part of the spectrum covers the interval of 1400 m to 1600nm or 1450nm to 1550nm.

[0053] In a preferred embodiment of the disclosed method the limit L is set such, that the second type of PET correlates with virgin polyethylene terephthalate (vPET), and the first type of PET correlates with recycled polyethylene terephthalate (rPET).

[0054] The marker additive may be added during a recycling process to convert vPET to rPET with the rPET having a marker additive content CONT2. The limit L to differentiate a first type of PET sample (rPET) and a second type of PET sample (vPET) with the proposed method is preset such that: L < CONT2.

[0055] The method may specifically be a computer-implemented method. The term "computer implemented method” as used herein may refer, without limitation, to a method involving at least one computer and / or at least one computer network. The computer and / or computer network may comprise at least one processor which may be configured for performing at least one of the method steps, specifically at least one of steps b), c) and d), of the method according to the present invention. The method may be performed completely automatically, specifically without user interaction. The term "automatically” as used herein may refer, without limitation, to a process which is performed completely by means of at least one computer and / or computer network and / or machine, in particular without manual action and / or interaction with a user.

[0056] In a further aspect of the invention, a computer program including computer-executable instructions for performing the method according to any one of the embodiments as described herein is disclosed, specifically method steps b) to d), when the program is executed on a computer or computer network, specifically a processor of the device for multiple transition monitoring.

[0057] Thus, generally speaking, disclosed and proposed herein is a computer program including computer-executable instructions for performing the method according to the present invention in one or more of the embodiments enclosed herein when the program is executed on a computer or computer network. Specifically, the computer program may be stored on a computer-readable data carrier. Thus, specifically, one, more than one or even all of the method steps as indicated above may be performed by using a computer or a computer network, preferably by using a computer program. The computer specifically may be fully or partially integrated into the device for multiple transition monitoring, and the computer programs specifically may be embodied as a software. Alternatively, however, at least part of the computer may also be located outside the device for multiple transition monitoring.

[0058] Further disclosed and proposed herein is a computer program product having program code means to perform the method according to the present invention in one or more of the embodiments disclosed herein, when the program is executed on a computer or computer network, e.g. one or more of the method steps mentioned above. Specifically, the program code means may be stored on a storage medium such as a computer-readable data carrier.

[0059] Further disclosed and proposed herein is a data carrier having a data structure stored thereon, which, after loading into a computer or computer network, such as into a working memory or main memory of the computer or computer network, may execute the method according to one or more of the embodiments disclosed herein, specifically one or more of the method steps mentioned above.

[0060] Further disclosed and proposed herein is a computer program product with program code means stored on a machine-readable carrier to perform the method according to one or more of the embodiments disclosed herein, when the program is executed on a computer or computer network, specifically one or more of the method steps mentioned above. As used herein, a computer program product refers to the program as a tradable product. The product may generally exist in an arbitrary format, such as in a paper format, or on a computer-readable data carrier. Specifically, the computer program product may be distributed over a data network.

[0061] Further disclosed and proposed herein is a modulated data signal which contains instructions readable by a computer system or computer network, for performing the method according to one or more of the embodiments disclosed herein, specifically one or more of the method steps mentioned above.

[0062] Further disclosed and proposed herein is a storage medium, wherein a data structure is stored on the storage medium and wherein the data structure is adapted to perform at least steps b), c) and d) of the method according to one or more of the embodiments disclosed herein after having been loaded into a main and / or working storage of a computer or of a computer network.

[0063] Specifically, further disclosed herein are:

[0064] - a computer or computer network comprising at least one processor, wherein the processor is adapted to perform at least steps b), c) and d) of the method according to one of the embodiments described in this description, and

[0065] - a computer loadable data structure that is adapted to perform at least steps b), c) and d) of the method according to one of the embodiments described in this description while the data structure is being executed on a computer. A further aspect of the invention relates to a system for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET, wherein the first type of PET is defined by comprising a marker additive with a content CMI higher than a preset limit L: CMI > L, and the second type of PET is defined by comprising no marker additive or the marker additive in a content CM2 less than or equal the preset limit L: 0 < CM2 L, wherein the marker additive is:

[0066] Calcium diethyl bis[[[3,5-bis(1 ,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate],

[0067] (well known synonyms of this substance are: Phosphonic acid, [[3,5-bis(1 , 1 -dimethylethyl)-4-hydroxyphenyl]methyl]-, monoethyl ester, calcium salt (2:1) or CAS 65140-91-2 or IRGANOX1425), and wherein the system comprises: at least one near-infrared (NIR) spectrometer device, wherein the near-infrared (NIR) spectrometer device is configured for acquiring at least one spectrum of the sample distinctive for the marker additive; and at least one evaluation device, wherein the evaluation device is configured for determining a content CM of the marker additive in the sample based on an evaluation of at least one part from that at least one spectrum, and classifying the sample depending on the determined content CM of the marker additive into the first type of PET when: CM > L or into the second type of PET when 0 < CM L.

[0068] As used herein, the term "system for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of polyethylene terephthalate (PET)” refers to an apparatus which comprises a NIR spectrometer device and an evaluation device. The near-infrared NIR spectrometer device is configured for acquiring at least one spectrum of the sample distinctive for the marker additive. The acquired spectrum may be made available for further analysis / evaluation as digital electronic data. For further details on the near-infrared spectrometer device, reference to the description above is made.

[0069] The system also comprises at least one evaluation device. The acquired NIR spectrum of the sample may be made available to the evaluation device for further analysis / evaluation preferably as digital electronic data. The evaluation device is configured for determining a content CM of the marker additive in the sample, especially based on a qualitative and quantitative evaluation / analysis of the least one part from that at least one spectrum. Further, the evaluation device is configured for classifying the sample depending on the determined content CM of the marker additive in relation to the limit L into the first or the second type of PET. For further details on the determination of the content CM and the classification, reference to the description above is made.

[0070] Specifically, the system may be configured for performing the method for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of polyethylene terephthalate (PET), as described above.

[0071] Specifically the system is configured such, that the limit L is set such, that the first type of PET correlates with recycled polyethylene terephthalate (rPET) and the second type of PET correlates with virgin polyethylene terephthalate (vPET).

[0072] A further aspect of the invention relates to a method for recycling of polyethylene terephthalate (PET) samples, wherein a first type of PET is defined by comprising a marker additive with a content Ci higher than a given limit L: Ci > L, and a second type of PET is defined by comprising no marker additive or the marker additive in a content C2 less than or equal the given limit L: 0 < C2 L, and wherein the marker additive is:

[0073] Calcium diethyl bis[[[3,5-bis(1 ,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] with the steps: a) providing a PET sample comprising at least one of the two types of PET; b) acquiring at least one spectrum of the sample distinctive for the marker additive using a near-infrared (NIR) spectrometer device; c) determining a content CM of the marker additive in the sample based on an evaluation of at least one part from that at least one spectrum; d) classifying the sample depending on the determined content CM of the marker additive into the first type of PET when: CM > L or into the second type of PET when 0 < CM L; e) separating classified first type PET sample and classified second type PET samples; f) blending the separated classified second type PET samples and the marker additive to form an intermixture M2 with a preset content CONT2 of the marker additive, g) reforming / extruding the intermixture M2 into a recycled PET product.

[0074] For details on the steps a), b), c) and d) reference to the description above is made.

[0075] As used herein, the term "separating” refers to physically separating classified first type PET samples and classified second type PET samples.

[0076] As used herein, the term "blending” may refer to adding I compounding I mixing the classified second type PET samples and the marker additive to form an intermixture. The term "mixing” may refer to a manipulation of an initially heterogeneous physical system with the intent to make it more homogeneous.

[0077] Preferably the addition of the marker additive (IRGANOX1425) to the classified second type PET samples in step f) is preferably conducted before reforming / extruding the intermixture into a rPET product, e.g. at a re-pelleting step.

[0078] Preferably the preset content CONT2 of the blending component (maker additive) in the intermixture is within a range of 0.2Vol% to 5Vol% or of 200ppm - 5000ppm.

[0079] Preferably the method for recycling of polyethylene terephthalate (PET) samples comprises the following additional steps: blending the separated first type PET samples and the marker additive to form an intermixture M1 with a preset content CONT 1 of the marker additive, and reforming / extruding the intermixture M1 or a combination of the intermixtures M1 and M2 into a recycled PET product.

[0080] Preferably the content CONT 1 is preset depending on a determined content of the marker additive in the separated first type polyethylene terephthalate (PET) samples before blending and / or is depending on an intrinsic viscosity value (IV- value) of the separated first type polyethylene terephthalate (PET) samples before blending.

[0081] Preferably separated first type polyethylene terephthalate (PET) samples (rPET samples) with intrinsic viscosity values of <0.8 are recommended to have IRGANOX1425 added in order to restore / maintain the functional and aesthetic properties (including organoleptic) needed for high value bottle "blowmolding” applications.

[0082] A last aspect of the invention relates to a use of

[0083] Calcium diethyl bis[[[3,5-bis(1 ,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate]

[0084] (synonyms of this substance are: Phosphonic acid, [[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-, monoethyl ester, calcium salt (2:1) or CAS 65140-91-2 or IRGANOX1425), as marker additive for polyethylene terephthalate (PET).

[0085] For further details on the use of this substance as marker additive for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET, reference to the description above is made.

[0086] Summarizing in the context of the present invention, the following embodiments are regarded as particularly preferred:

[0087] Embodiment 1 : A Method for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET, wherein the first type of PET is defined by comprising a marker additive with a content CMI higher than a preset limit L: CMI > L, and the second type of PET is defined by comprising no marker additive or the marker additive in a content CM2 less than or equal the preset limit L: 0 < CM2 L, and wherein the marker additive is: Calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate], with the steps: a) providing a sample comprising at least one of the two types of PET; b) acquiring at least one spectrum of the sample distinctive for the marker additive using a near-infrared (NIR) spectrometer device; c) determining a content CM of the marker additive in the sample based on an evaluation of at least one part from the at least one spectrum; and d) classifying the sample depending on the determined content CM into the first type of PET when: CM > L or into the second type of PET when: 0 < CM L.

[0088] Embodiment 2: The method according to the preceding embodiment, wherein step b) comprises determining, and optionally storing on a storage medium, data points representing an absorbance signal, specifically over a wavenumber or a wavelength.

[0089] Embodiment 3: The method according to any one of the preceding embodiments, wherein step d) comprises classifying the sample into virgin PET (vPET) and recycled PET (rPET).

[0090] Embodiment 4: The method according to any one of the preceding embodiments, wherein step d) comprises classifying the sample depending on a position of the at least one peak determined from the spectrum.

[0091] Embodiment 5: The method according to any one of the preceding embodiments, wherein the spectrum is acquired in a region between 1400nm to 1600nm.

[0092] Embodiment 6: The method according to any one of the preceding embodiments, wherein the spectrum is acquired in a region between 1450nm to 1550nm.

[0093] Embodiment 7: The method according to any one of the preceding embodiments, wherein in step c) a peak in a region between 1400nm and 1600nm, specifically in a region between 1450nm and 1550nm, is determined.

[0094] Embodiment 8: The method according to any one of the preceding embodiments, wherein in step c) a fitting procedure of at least a part of the spectrum is performed.

[0095] Embodiment 9: The method according to any one of the preceding embodiments, wherein the limit L is set such, that the first type of PET correlates with recycled polyethylene terephthalate (rPET) and the second type of PET correlates with virgin polyethylene terephthalate (vPET).

[0096] Embodiment 10: A system for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET, wherein the first type of PET is defined by comprising a marker additive with a content CMI higher than a preset limit L: CMI > L, and the second type of PET is defined by comprising no marker additive or the marker additive in a content CM2 less than or equal the preset limit L: 0 < CM2 L, wherein the marker additive is: Calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate], and wherein the system comprises: at least one near-infrared (NIR) spectrometer device, wherein the near-infrared (NIR) spectrometer device is configured for acquiring at least one spectrum of the sample distinctive for the marker additive; and at least one evaluation device, wherein the evaluation device is configured for o determining a content CM of the marker additive in the sample based on an evaluation of at least one part from that at least one spectrum, and o classifying the sample depending on the determined content CM of the marker additive into the first type of PET when: CM > L or into the second type of PET when 0 < CM L.

[0097] Embodiment 11: The system according to the preceding embodiment, wherein the system is configured for performing the method for classifying a sample into one of at least two types of PET according to any one of the preceding claims referring to a method for classifying a sample into one of at least two types of PET.

[0098] Embodiment 12: The system according to any one of the preceding embodiments, wherein t near-infrared (NIR) spectrometer device is configured such that the acquired at least one spectrum covers a wavelength interval of 1400nm to 1600nm or 1450nm to 1550nm.

[0099] Embodiment 13: The system according to any one of the preceding embodiments, wherein the limit L is set such, that the second type of PET correlates with virgin polyethylene terephthalate (vPET), and the first type of PET correlates with recycled polyethylene terephthalate (rPET).

[0100] Embodiment 14: A computer or computer network comprising at least one processor, wherein the processor is adapted to perform at least steps b), c) and d) of the method for classifying a sample into one of at least two types of PET according to any one of the preceding embodiments referring to a method for classifying a sample into one of at least two types of PET.

[0101] Embodiment 15: A computer loadable data structure that is adapted to perform at least steps b), c) and d) of the method for classifying a sample into one of at least two types of PET according to any one of the preceding embodiments referring to a method for classifying a sample into one of at least two types of PET while the data structure is being executed on a computer.

[0102] Embodiment 16: A computer program, wherein the computer program is adapted to perform at least steps b), c) and d) of the method for classifying a sample into one of at least two types of PET according to any one of the preceding embodiments referring to a method for classifying a sample into one of at least two types of PET while the program is being executed on a computer.

[0103] Embodiment 17: A computer program comprising program means for performing at least steps b), c) and d) of the method for classifying a sample into one of at least two types of PET according to any one of the preceding embodiments referring to a method for classifying a sample into one of at least two types of PET while the computer program is being executed on a computer or on a computer network.

[0104] Embodiment 18: A computer program comprising program means according to the preceding embodiment, wherein the program means are stored on a storage medium readable to a computer. Embodiment 19: A storage medium, wherein a data structure is stored on the storage medium and wherein the data structure is adapted to perform at least steps b), c) and d) of the method for classifying a sample into one of at least two types of PET according to any one of the preceding embodiments referring to a method for classifying a sample into one of at least two types of PET after having been loaded into a main and / or working storage of a computer or of a computer network.

[0105] Embodiment 20: A computer program product having program code means, wherein the program code means can be stored or are stored on a storage medium, for performing at least steps b), c) and d) of the method for classifying a sample into one of at least two types of PET according to any one of the preceding embodiments referring to a method for classifying a sample into one of at least two types of PET when the program code means are executed on a computer or on a computer network.

[0106] Embodiment 21 : A method for recycling of polyethylene terephthalate (PET) samples, wherein a first type of PET is defined by comprising a marker additive with a content Ci higher than a given limit L: Ci > L, and a second type of PET is defined by comprising no marker additive or the marker additive in a content C2 less than or equal the given limit L: 0 < C2 L, and wherein the marker additive is:

[0107] Calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] with the steps: providing a PET sample comprising at least one of the two types of PET; acquiring at least one spectrum of the sample distinctive for the marker additive using a near-infrared (NIR) spectrometer device; determining a content CM of the marker additive in the sample based on an evaluation of at least one part from that at least one spectrum; classifying the sample depending on the determined content CM of the marker additive into the first type of PET when: CM > L or into the second type of PET when 0 < CM L; separating classified first type PET sample and classified second type PET samples; blending the separated classified second type PET samples and the marker additive to form an intermixture M2 with a preset content CONT2 of the marker additive, reforming / extruding the mixture M2 into a recycled PET product.

[0108] Embodiment 22: The method according to the preceding embodiment, wherein the content CONT2 of the blending component (maker additive) in the intermixture is within a range of 0.2Vol% to 5Vol% or of 200ppm - 5000ppm.

[0109] Embodiment 23: The method according to any one of the preceding embodiments, with the steps: blending the separated first type PET samples and the marker additive to form a mixture M1 with a preset content CONT 1 of the marker additive, and reforming / extruding the mixture M1 or a combination of the mixtures M1 and M2 into a recycled PET product.

[0110] Embodiment 24: The method according to the preceding embodiment, wherein the content CONT1 is preset depending on a determined content of the marker additive in the separated first type polyethylene terephthalate (PET) samples before blending and / or is depending on a determined intrinsic viscosity value of the separated first type polyethylene terephthalate (PET) samples before blending.

[0111] Embodiment 25: Use of

[0112] Calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] as marker additive for polyethylene terephthalate (PET).

[0113] BRIEF DESCRIPTION OF THE FIGURES

[0114] Further optional details and features of the invention are evident from the description of the preferred exemplary embodiments, which follows in conjunction with the dependent claims. In this context, the particular features may be implemented alone, or with features in combination. The invention is not restricted to the exemplary embodiments. The exemplary embodiments are shown schematically in the figures. Identical reference numerals in the individual figures refer to identical elements or elements with identical function, or elements which correspond to one another with regard to their functions.

[0115] FIG. 1 shows a schematic representation of an exemplary embodiment of a method for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET, wherein the first type of PET is defined by comprising a marker additive with a content CMI higher than a preset limit L: CMI > L, and the second type of PET is defined by comprising no marker additive or the marker additive in a content CM2 less than or equal the preset limit L: 0 < CM2 L, wherein the limit L is set such, that the second type of PET correlates with virgin polyethylene terephthalate (vPET), and the first type of PET correlates with recycled polyethylene terephthalate (rPET), and wherein the marker additive is:

[0116] Calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] (IRGANOX1425).

[0117] Step 101 represents providing a sample comprising at least one of the two types of PET.

[0118] Step 102 represents acquiring at least one spectrum of the sample distinctive for the marker additive using a near-infrared (NIR) spectrometer device.

[0119] Step 103 represents determining a content CM of the marker additive in the sample based on an evaluation of at least one part from the at least one spectrum.

[0120] Step 104 represents classifying the sample depending on the determined content CM into the first type of PET when: CM > L or into the second type of PET when 0 < CM < L.

[0121] FIG. 2 shows a schematic representation of an exemplary embodiment of a system for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET, wherein the first type of PET is defined by comprising a marker additive with a content CMI higher than a preset limit L: CMI > L, and the second type of PET is defined by comprising no marker additive or the marker additive in a content CM2 less than or equal the preset limit L:

[0122] 0 < CM2 L, wherein the marker additive is:

[0123] Calcium diethyl bis[[[3,5-bis(1 ,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] (IRGANOX1425).

[0124] The system comprises: one near-infrared (NIR) spectrometer device 201, wherein the near-infrared (NIR) spectrometer device is configured for acquiring at least one spectrum of the sample distinctive for the marker additive; and one evaluation device 202, wherein the evaluation device is configured for o determining a content CM of the marker additive in the sample based on an evaluation of at least one part from that at least one spectrum, and o classifying the sample depending on the determined content CM of the marker additive into the first type of PET when: CM > L or into the second type of PET when 0 < CM L.

[0125] FIG. 3 shows a schematic representation of an exemplary embodiment of a method for recycling of polyethylene terephthalate (PET) samples, wherein a first type of PET is defined by comprising a marker additive with a content Ci higher than a given limit L: Ci > L, and a second type of PET is defined by comprising no marker additive or the marker additive in a content C2 less than or equal the given limit L: 0 < C2 L, and wherein the marker additive is: Calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] (IRGANOX1425).

[0126] Step 101 represents providing a PET sample comprising at least one of the two types of PET.

[0127] Step 102 represents acquiring at least one spectrum of the sample distinctive for the marker additive using a nearinfrared (NIR) spectrometer device.

[0128] Step 103 represents determining a content CM of the marker additive in the sample based on an evaluation of at least one part from that at least one spectrum.

[0129] Step 104 represents classifying the sample depending on the determined content CM of the marker additive into the first type of PET when: CM > L or into the second type of PET when 0 < CM L.

[0130] Step 105 represents physically separating classified first type PET samples and classified second type PET samples. Step 106 represents blending the separated classified second type PET samples with the marker additive to form an intermixture M2 with a preset content CONT2 of the marker additive, wherein the content CONT2 of the marker additive is within a range of 0.2Vol% to 5Vol% or of 200ppm - 5000ppm.

[0131] Step 107 represents reforming / extruding the mixture M2 into a recycled PET product. LIST OF REFERENCE NUMBERS

[0132] 101 - 109 method steps

[0133] 201 NIR spectrometer device 202 evaluation device

Claims

CLAIMS1 . A method for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET, wherein the first type of PET is defined by comprising a marker additive with a content CMI higher than a preset limit L: CMI > L, and the second type of PET is defined by comprising no marker additive or the marker additive in a content CM2 less than or equal the preset limit L: 0 < CM2 L, and wherein the marker additive is: Calcium diethyl bis[[[3,5-bis(1 ,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate], with the steps: a) providing (101) a sample comprising at least one of the two types of PET; b) acquiring (102) at least one spectrum of the sample distinctive for the marker additive using a nearinfrared (NIR) spectrometer device; c) determining (103) a content CM of the marker additive in the sample based on an evaluation of at least one part from the at least one spectrum; and d) classifying (104) the sample depending on the determined content CM into the first type of PET when: CM > L or into the second type of PET when 0 < CM L.

2. The method according to claim 1 , wherein the at least one part from the spectrum covers the wavelength interval of 1400nm to 1600nm or 1450nm to 1550nm.

3. The method according to claim 1 or 2, wherein the limit L is set such, that the first type of PET correlates with recycled polyethylene terephthalate (rPET) and the second type of PET correlates with virgin polyethylene terephthalate (vPET).

4. A system for classifying a sample of polyethylene terephthalate (PET) into a first and a second type of PET, wherein the first type of PET is defined by comprising a marker additive with a content CMI higher than a preset limit L: CMI > L, and the second type of PET is defined by comprising no marker additive or the marker additive in a content CM2 less than or equal the preset limit L: 0 < CM2 L, wherein the marker additive is: Calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate], and wherein the system comprises: at least one near-infrared (NIR) spectrometer device (201), wherein the near-infrared (NIR) spectrometer device is configured for acquiring at least one spectrum of the sample distinctive for the marker additive; and at least one evaluation device (202), wherein the evaluation device is configured for o determining a content CM of the marker additive in the sample based on an evaluation of at least one part from that at least one spectrum, and o classifying the sample depending on the determined content CM of the marker additive into the first type of PET when: CM > L or into the second type of PET when 0 < CM L.

5. The system according to claim 4, wherein the at least one part from the at least one spectrum acquired by the near-infrared (NIR) spectrometer device (201) covers a wavelength interval of 1400nm to 1600nm or 1450nm to 1550nm.

6. The system according to claims 4 or 5, wherein the limit L is set such, that the second type of PET correlates with virgin polyethylene terephthalate (vPET), and the first type of PET correlates with recycled polyethylene terephthalate (rPET).

7. A method for recycling of polyethylene terephthalate (PET) samples, wherein a first type of PET is defined by comprising a marker additive with a content Ci higher than a given limit L: Ci > L, and a second type of PET is defined by comprising no marker additive or the marker additive in a content C2 less than or equal the given limit L: 0 < C2 L, and wherein the marker additive is:Calcium diethyl bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] with the steps: a) providing (101 ) a PET sample comprising at least one of the two types of PET; b) acquiring (102) at least one spectrum of the samples distinctive for the marker additive using a nearinfrared (NIR) spectrometer device; c) determining (103) a content CM of the marker additive in the sample based on an evaluation of at least one part from that at least one spectrum; d) classifying (104) the sample depending on the determined content CM of the marker additive into the first type of PET when: CM > L or into the second type of PET when 0 < CM L; e) separating (105) classified first type PET sample and classified second type PET samples; f) blending (106) the separated classified second type PET samples and the marker additive to form an intermixture M2 with a preset content CONT2 of the marker additive, g) reforming / extruding (107) the mixture M2 into a recycled PET product.

8. The method according to claim 7, wherein the preset content CONT2 is within a range of 0, 2Vol% to 5Vol% or of 200ppm - 5000ppm.

9. The method according to claims 7 or 8, with the steps: blending (108) the separated first type PET samples and the marker additive to form a mixture M1 with a preset content CONT 1 of the marker additive, and reforming / extruding (109) the mixture M1 or a combination of the mixtures M1 and M2 into a recycled PET product.

10. The method according to claim 9, wherein the content CONT 1 is preset depending on a determined content of the marker additive in the separated first type Polyethylene terephthalate (PET) samples before blending and / or is depending on a determined intrinsic viscosity value of the separated first type Polyethylene terephthalate (PET) samples before blending.

11. A use ofCalcium diethyl bis[[[3,5-bis(1 ,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate] as marker additive for polyethylene terephthalate (PET).

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