WO2026013169A2 - Stabilisation de matériau de recyclage de polypropylène contre la dégradation - Google Patents

Stabilisation de matériau de recyclage de polypropylène contre la dégradation

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Publication number
WO2026013169A2
WO2026013169A2 PCT/EP2025/069669 EP2025069669W WO2026013169A2 WO 2026013169 A2 WO2026013169 A2 WO 2026013169A2 EP 2025069669 W EP2025069669 W EP 2025069669W WO 2026013169 A2 WO2026013169 A2 WO 2026013169A2
Authority
WO
WIPO (PCT)
Prior art keywords
polypropylene
recycling material
tert
butyl
antioxidant
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2025/069669
Other languages
English (en)
Other versions
WO2026013169A3 (fr
Inventor
Alexandra Romina ALBUNIA
Yuliia ROMANENKO
Bernadette DUSCHER
Peter Denifl
Paul Baumann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Borealis GmbH
Original Assignee
Borealis GmbH
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Filing date
Publication date
Application filed by Borealis GmbH filed Critical Borealis GmbH
Publication of WO2026013169A2 publication Critical patent/WO2026013169A2/fr
Publication of WO2026013169A3 publication Critical patent/WO2026013169A3/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/06—Recovery or working-up of waste materials of polymers without chemical reactions
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/10—Homopolymers or copolymers of propene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
    • C08K5/005—Stabilisers against oxidation, heat, light, ozone
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2207/00—Properties characterising the ingredient of the composition
    • C08L2207/20—Recycled plastic

Definitions

  • the present invention relates to a process for stabilizing a polypropylene recycling material against degradation, preferably oxidative and/or thermal degradation, as well as to compositions for the stabilization of a polypropylene recycling material.
  • Polyolefins in particular polyethylene and polypropylene, are increasingly consumed in large amounts in a wide range of applications, including packaging for food and other goods, fibers, automotive components, wires and cables, and a great variety of manufactured articles.
  • Recycled polyolefins normally have properties, which are deteriorated compared to those of virgin, i.e., freshly produced, polyolefins.
  • recycled polyolefins often have limited mechanical and optical properties and thus, they do not fulfil customer requirements.
  • Journal of Polymers and the Environment 30, 494-503, (2022) discloses the change of melt flow rate of recycled polypropylene depending on the contaminant content and the recycling process. Further, a much shorter oxidation induction time and a much lower oxidation induction temperature are recorded for contaminated reprocessed polypropylenes.
  • additive compositions for virgin polymers are usually not sufficient to provide stabilization of recycling materials.
  • Contaminations in the polyolefin recycling materials and processing of these materials can reduce or eliminate the effectiveness of certain additives.
  • the compositions of recycling materials are very inhomogeneous, the contents of contaminants vary to high extents. Thus, their effect on polymer degradation and other properties are complex and not easy to predict. Accordingly, additive packages generally used for virgin polymers may not be efficiently stabilizing.
  • stabilizing additives suggested for recycling polyethylene materials may not be suitable for recycling polypropylene materials and vice versa. Therefore, there is a need in the art for stabilizing methods for recycling polyolefin materials in order to prevent degradation thereof and to improve the properties of the recycled polyolefin products. These methods should be cost-efficient and integrable in common recycling processes.
  • the present invention is based on intense studies of the contents of polypropylene recycling material, in particular polypropylene recycling material originating from packaging applications, e.g., from flexible material such as polypropylene films, and the evaluation of required additives for improving stability of the recycled products prepared thereof.
  • the present invention is directed to a process for stabilizing a polypropylene recycling material against degradation, comprising extrusion-blending a polypropylene recycling material with a) from 0.02 to 0.25 wt.-% of one or more primary antioxidant(s), b) from 0.02 to 0.28 wt.-% of one or more secondary antioxidant(s), c) from 0.05 to 0.60 wt.% of one or more metal deactivator(s), and d) from 0.00 to 5.00 wt.-% of further additive(s) and/or additive carrier(s), to form a stabilized polypropylene recycled product, wherein the polypropylene recycling material comprises, based on the total weight of the polypropylene recycling material, from 2 to less than 20,000 ppm of the sum of contents of the transition metals selected from titanium (Ti), zinc (Zn), copper (Cu) and iron (Fe), determined by X-ray fluorescence (XRF) spectroscopy as described herein.
  • XRF X-ray
  • the process according to the present invention enables stabilization of polypropylene recycling material with a wide range of different contaminants and reduces degradation, particularly oxidative and/or thermal degradation, of the final recycled product.
  • the process according to the present invention is particularly suitable for the stabilization of polypropylene recycling material originating from packaging applications.
  • Respective polypropylene recycling material is characterized by typical contents of specific metals (e.g., transition metals), which can be sufficiently bonded by the composition of additives incl. the one or more metal deactivators.
  • packaging materials typically have relatively low contents of copper and relatively high contents titanium.
  • the process according to the present invention can be easily integrated in established polypropylene recycling processes, and when using common additives from the selected classes of additives, the costs can be held relatively low.
  • the present invention is also directed to the stabilized polypropylene recycled product obtainable by the process according to the present invention.
  • the present invention is also directed to a composition for stabilizing a polypropylene recycling material against degradation, comprising a) one or more primary antioxidant(s), b) one or more secondary antioxidant(s), c) one or more metal deactivator(s), and d) optionally further additive(s) and/or additive carrier(s), wherein the polypropylene recycling material comprises, based on the total weight of the polypropylene recycling material, from 2 to less than 20,000 ppm of the sum of contents of the transition metals selected from titanium (Ti), zinc (Zn), copper (Cu) and iron (Fe), determined by X-ray fluorescence (XRF) spectroscopy as described herein.
  • XRF X-ray fluorescence
  • the present invention is directed to the use of this composition for stabilizing said polypropylene recycling material against degradation.
  • the present invention is directed to a process for stabilizing a polypropylene recycling material against degradation, preferably oxidative and/or thermal degradation.
  • the process employs a polypropylene recycling material as the material to be stabilized.
  • polypropylene recycling material denotes a polypropylene material that has completed at least a first use cycle (or life cycle), i.e., has already served its first purpose.
  • waste such as consumer waste.
  • industrial waste is manufacturing scrap, which does normally not reach a consumer.
  • polypropylene recycling material originates from consumer waste, such as waste that may be obtained from conventional collecting systems, e.g., those implemented in the European Union.
  • Such post-consumer waste material may e.g., be characterized by a limonene content of at least 0.1 ppm (determined by solid phase microextraction (HS-SPMEGC-MS) by standard addition), which is usually not present in virgin polymer material, i.e., a polymer material freshly prepared.
  • polypropylene recycling material often contains a mixture of different polypropylene polymers.
  • polyolefins and non-polyolefin polymers e.g., polystyrene, polyethylene terephthalate, polyamide etc.
  • One single polymer article may be composed of only one single kind of polymer or already from different kinds of polymers.
  • other components may be present in the polypropylene recycling material also originating from post-consumer waste, such as wood, paper, limonene, aldehydes, ketones, fatty acids, metals, and/or long-term decomposition products of stabilizers. These components are usually not contained in virgin polymer material.
  • polypropylene denotes a propylene homopolymer and propylene copolymer and combinations (e.g., blends) thereof.
  • Propylene homopolymers generally comprise at least 98 wt.-%, based on the total weight of the homopolymer, of units derived from propylene.
  • Propylene copolymers generally refer to polymers comprising more than 50 wt.-%, based on the total weight of the copolymer, of units derived from propylene and further units derived from other polymer monomers, particularly ethylene and/or alpha-olefin units having from 4 to 12 carbon atoms.
  • the polypropylene recycling material comprises at least 80 wt.-%, preferably at least 85 wt.-%, and more preferably at least 90 wt.-%, based on the total weight of the polypropylene recycling material, of polypropylene, i.e., propylene homopolymers, propylene copolymers and combinations (e.g., blends) thereof.
  • polypropylene i.e., propylene homopolymers, propylene copolymers and combinations (e.g., blends) thereof.
  • nonpolypropylene polymers and other components may be present in the polyolefin in a content of less than 20 wt.-%.
  • the polypropylene content may be in the range of from 80 to 99.7 wt.-%, preferably from 85 to 99.5 wt.-%, such as from 90 to 99 wt.-%.
  • the content of polymers and monomer units can be measured by spectroscopic methods, in particular, by Fourier-transform infrared (FTIR) spectroscopy.
  • FTIR Fourier-transform infrared
  • the polypropylene recycling material used according to the present invention is preferably of sufficient purity to be used as final polypropylene recycled product for a variety of applications. It has been found that polypropylene recycling material with the below described properties is particularly suitable to be used in the process of the present invention, and excellent stabilization of such material can be reached by the process.
  • the polypropylene recycling material has a sum of contents of contaminants selected from polyamide (PA), polyethylene terephthalate (PET) and polystyrene (PS) of less than 2.5 wt.-%, such as less than 2.3 wt.-%, based on the total weight of the polypropylene recycling material and determined by Fourier-transform infrared (FTIR) spectroscopy as described herein below.
  • the sum of contents of these contaminants may be in the range of from 0.0 to less than 2.5 wt.-%, such as from 0.1 to less than 2.3 wt.-%.
  • the polypropylene recycling material has a sum of contents of the transition metals selected from titanium (Ti), zinc (Zn), copper (Cu) and iron (Fe) of less than 20,000 ppm, preferably less than 18,000 ppm, such as less than 10,000 ppm, based on the total weight of the polypropylene recycling material and determined by X-ray fluorescence (XRF) spectroscopy as described herein below.
  • the sum of contents of these contaminants ranges from 2 to less than 20,000 ppm, preferably from 5 to less than 18,000 ppm, such as from 10 to less than 10,000 ppm.
  • the polypropylene recycling material has a sum of contents of the transition metals selected from zinc (Zn), copper (Cu) and iron (Fe) of less than 300 ppm, preferably less than 250 ppm, such as less than 100 ppm, based on the total weight of the polypropylene recycling material and determined by X-ray fluorescence (XRF) spectroscopy as described herein below.
  • the sum of contents of these contaminants may be in the range of from 0 to less than 300 ppm, preferably from 0 to less than 250 ppm, such as from 1 to less than 100 ppm.
  • the polypropylene recycling material has a copper (Cu) content of less than 150 ppm, preferably less than 100 ppm, such as less than 50 ppm, based on the total weight of the polypropylene recycling material and determined by X-ray fluorescence (XRF) spectroscopy as described herein below.
  • the copper content may be in the range of from 0 to less than 150 ppm, preferably from 0 to less than 100 ppm.
  • the polypropylene recycling material comprises, based on the total weight of the polypropylene recycling material, a calcium (Ca) content of from 100 to less than 30,000 ppm, based on the total weight of the polypropylene recycling material and determined by X-ray fluorescence (XRF) spectroscopy as described herein below.
  • a calcium (Ca) content of from 100 to less than 30,000 ppm, based on the total weight of the polypropylene recycling material and determined by X-ray fluorescence (XRF) spectroscopy as described herein below.
  • the polypropylene recycling material comprises, based on the total weight of the polypropylene recycling material, an aluminum (Al) content of from 10 to 1 ,000 ppm, preferably from 20 to less than 800 ppm, based on the total weight of the polypropylene recycling material and determined by X-ray fluorescence (XRF) spectroscopy as described herein below.
  • Al aluminum
  • XRF X-ray fluorescence
  • the polypropylene recycling material is characterized by at least one, preferably all of the following metal contents, based on the total weight of the polypropylene recycling material and determined by X-ray fluorescence (XRF) spectroscopy as described herein below: a) a content of calcium (Ca) of less than 30,000 ppm, preferably less than 20,000 ppm, such as in the range of from 100 to less than 30,000 ppm; b) a content of titanium (Ti) of less than 20,000 ppm, preferably less than 16,000 ppm, such as in the range of from 50 to less than 20,000 ppm; c) a content of iron (Fe) of less than 400 ppm, preferably less than 300 ppm, such as less than 150 ppm or in the range of from 2 to less than 400 ppm; d) a content of zinc (Zn) of less than 150 ppm, preferably less than 100 ppm, such as in the range of from 2 to less than less than X
  • the polypropylene recycling material is further characterized by a content of aluminum (Al) of less than 1 ,000 ppm, preferably less than 800 ppm, such as in the range of from 10 to less than 1 ,000 ppm.
  • Al aluminum
  • polypropylene recycling material used according to the present invention is preferably characterized by the properties described in the following. It has been found that polypropylene recycling material with the below described properties is particularly suitable to be used in the process of the present invention.
  • the polypropylene recycling material has from 1 to 15 wt.-% of ethylene units (C2), based on the total weight of the polypropylene recycling material and determined by Fourier- transform infrared (FTIR) spectroscopy as described herein below.
  • C2 ethylene units
  • FTIR Fourier- transform infrared
  • the polypropylene recycling material has a melt flow rate MFR2 in the range of from 3 to 12 g/10 min, preferably from 4 to 10 g/10 min, such as from 5 to 9 g/10 min, determined according to ISO 1133, 230 °C, 2.16 kg.
  • the polypropylene recycling material is characterized by at least one, more preferably all, of the following properties, determined by CRYSTEX QC analysis as described herein below: i) an intrinsic viscosity (IV) in the range of from 1.5 to 2.2 dl/g, such as from 1.6 to 2.1 dl/g; ii) an ethylene content (C2) in the range of from 2.0 to 10.0 wt.-%, preferably from 2.5 to 9.0 wt.-%, relative to the total weight of the polypropylene recycling material; iii) a content of soluble fraction (SF) in the range of from 3.0 to 15.0 wt.-%, preferably from 3.5 to 13.0 wt.-%, more preferably from 4.0 to 11.0 wt.-%, relative to the total weight of the polypropylene recycling material; iv) an intrinsic viscosity (IV(SF)) of the soluble fraction (SF) in the range of from 0.5 to 2.0 dl/g
  • the polypropylene recycling material can be employed in the process in the form obtained from a provider (e.g., a waste collection system) if it already has the required polypropylene content and preferably other properties (e.g., sufficient purity) to be used as a recycled product. It may also be presorted to obtain a concentrated content of polypropylene material.
  • a provider e.g., a waste collection system
  • other properties e.g., sufficient purity
  • the polypropylene recycling material originates from packaging polypropylene recycling material, particularly from flexible polypropylene recycling articles.
  • flexible polymer articles or “flexible polymer material” (such as flexible polypropylene recycling articles/material) is well known in the art of polymer technology and is contrasted to the wording “rigid polymer articles” or “rigid polymer material” .
  • a distinction may be made based on the thickness of these articles or material, i.e. , typically, flexible polymer articles/material are objects that are thinner than 120 pm. The thickness can be measured on a sample of flexible polymer articles/material by a micrometer gauge.
  • flexible polymer articles/material are objects made from thin continuous plastic materials, i.e., plastic films, fibers, and all plastic fabrics (e.g., woven and melt-blown fibers).
  • the flexible polypropylene recycling material comprises objects, wherein at least 70 wt.-% of the objects are of flexible material, i.e., are thinner than 120 pm.
  • a suitable mechanical recycling process for the preparation of the polypropylene recycling material to be used in the process according to the present invention may comprise any, preferably all, of the following steps: a) providing a precursor polyolefin recycling material stream (A) that contains polypropylene recycling material, preferably flexible polypropylene recycling material; b) sieving the precursor polyolefin recycling stream (A) to create a sieved polyolefin recycling stream (B) having only articles with a longest dimension in the range of from 30 to 400 mm; c) removing metal articles from the sieved polyolefin recycling material stream (B) to obtain a purer polyolefin recycling stream (C); d) sorting the polyolefin recycling material stream (C) by means of one or more optical sorters at least by polymer type, transparency and color, and
  • any of the polypropylene recycling material streams (G) and (H) represent suitable material for stabilization for the process according to the present invention.
  • the process preferably comprises additional steps of controlling the quality obtained after one or more of the above-described steps, such as after the sorting step d) and/or directly before an optional pre-extrusion step h) or before the extrusion-blending of the process according to the present invention.
  • steps are generally carried out on a sample drawn from the polymer stream.
  • the polypropylene recycling material may be in a (physical) form suitable for the extrusion-blending.
  • the polypropylene recycling material may be in the form of flakes obtained by a size-reducing, e.g., shredding step.
  • Suitable flakes preferably have a surface area in the range of from 50 to 2500 mm 2 , more preferably from 100 to 1600 mm 2 and most preferably from 150 to 900 mm 2 .
  • the flake surface area is defined as the surface area of one of the faces of a flake. This surface area is approximately half of the total surface area of the flake, which has two such faces in addition to a very small amount of surface area coming from the edges of the flake. Accordingly, the total surface area of the flake can range to more than 5000 mm 2 .
  • the polypropylene recycling material is already present as a preextruded material, i.e., it has passed an extrusion step without addition of any additives. Dosing of additives is facilitated if the polypropylene recycling material is in a pre-extruded form.
  • the process according to the present invention comprises extrusion-blending a polypropylene recycling material with specific additives. This means that the polypropylene recycling material is blended, i.e., mixed, with specific additives during an extrusion step.
  • the polypropylene recycling material is placed in an extrusion device and the additives are added.
  • the additives may be added to the polypropylene recycling material as single components, as compositions of some of these additives or as a composition of all additives (i.e., “onepack”), possibly further comprising a carrier (e.g., in the form of a masterbatch).
  • a carrier e.g., in the form of a masterbatch.
  • the extrusion step may be carried out by a conventional compounding or blending apparatus or an extruder, e.g., a single or a twin-screw extruder, such as a co-rotating twin-screw extruder.
  • a conventional compounding or blending apparatus or an extruder e.g., a single or a twin-screw extruder, such as a co-rotating twin-screw extruder.
  • the extrusion is a melt-extrusion and it preferably includes a melt- filtration step, wherein larger gels and other particles are reduced in size by filtration. This notably reduces the content of respective inclusions of larger sizes (such as >50 pm) and improves the quality of the polypropylene recycled product.
  • the melt- filtration step may include one or more filtration sub-steps, which may optionally be separated by a degassing and/or vacuumizing sub-steps.
  • filters may be employed such as in the form of filter discs (preferably continuous laser filter discs).
  • the average pore sizes of the filters may be the same or different.
  • the average pore sizes of the filters decrease with the sequence of the filtration sub-steps. This enables efficient filtration with less contamination and blocking of the filters, as the particles are separated by the filters in the sequence of reduced sizes.
  • the first filter may comprise a perforated metal plate or drum, and the second filter may comprise a fiber mesh, for example, a metal fiber mesh.
  • the second filter may be a screen changer or a belt filter.
  • the first filter may have a mesh size of 70 to 150 pm, preferably 75 to 130 pm, more preferably 80 to 110 pm.
  • the second filter may have a mesh size of 40 to 130 pm, preferably 45 to 110 pm, more preferably 50 to 100 pm.
  • the second filter may have a mesh size smaller than that of the first filter.
  • Perforations in the first filter may be formed by laser (laser filter).
  • a cascade of filters may be used, for example, a cascade of more than two filters is used, such as three, four or five filters. Where a cascade of two or more filters is used, the second or subsequent filter may have a mesh size that is smaller than the mesh size of the filter that immediately precedes it in the cascade.
  • the first filter may have perforations that are not uniform in cross-section.
  • the perforations may be frustoconical in cross section, such that each perforation has a minor and major diameter.
  • the second filter may have a mesh size that is smaller than at least the major diameter of the first filter, preferably smaller than both the major and minor diameter of the first filter.
  • the process according to the present invention may also comprise the above-discussed steps of mechanical recycling as integral parts of the process. Accordingly, in some embodiments, the process according to the present invention comprises the steps a) to h) as described above, and further comprises: i) extrusion-blending the polypropylene recycling material stream (G) or (H) with one or more primary antioxidant(s), one or more secondary antioxidant(s), one or more metal deactivator(s), and optionally further additives and/or additive carriers, to form a stabilized polypropylene recycled product (I); j) preferably pelletizing, the stabilized polypropylene recycled product (I) to form a pelletized stabilized polypropylene recycled product (J); and k) optionally aerating the stabilized polypropylene recycled product (I) or (J) to remove volatile organic compounds, thereby generating an aerated, preferably pelletized, stabilized polypropylene recycled product (K). Stabilized polypropylene recycled product
  • a “recycled’ polymer material or product denotes a polymer material that has been prepared from a respective polymer recycling material by a recycling process and can be used in the general application of polymers.
  • polymer recycled product is prepared from polymer recycling materials by purification (and optional pre-extrusion without additive addition) and subsequent extrusion in the presence of additives.
  • the stabilized polypropylene recycled product is characterized by a very similar content of polymers and metals as described above for the polypropylene recycling material. Thus, the above-described ranges are the same for the stabilized polypropylene recycled product.
  • the stabilized polypropylene recycled product comprises the additives added as well as degradation products (of additives) which occur during the blendextrusion.
  • the stabilized polypropylene recycled product is stabilized against degradation, preferably oxidative and/or thermal degradation. Accordingly, the degradation of the stabilized polypropylene recycled product is decelerated and/or minimized. This can be seen in the change of the oxidation induction time (OIT) at 200 °C and enhanced temperature of the oxidation induction, as well as on the lower contents of other typical polypropylene degradation products (e.g., acetic acid etc.) and/or volatile compounds.
  • OIT oxidation induction time
  • a polypropylene recycling material is extrusion-blended with a) from 0.02 to 0.25 wt.-% of one or more primary antioxidant(s), b) from 0.02 to 0.28 wt.-% of one or more secondary antioxidant(s), c) from 0.05 to 0.60 wt.% of one or more metal deactivator(s), and d) from 0.00 to 5.00 wt.-% of further additive(s) and/or additive carrier(s).
  • Oxidation can occur at every stage of the life cycle of a polymer, i.e. , during manufacturing and storage of the material or during processing and end-use.
  • Typical manifestations of oxidation of polymers can be change of viscosity during processing, appearance, and loss of mechanical properties such as elongation, impact strength, tensile strength, and flexibility. It is generally known that antioxidants protect polymers against oxidation by controlling molecular weight changes that lead to a loss of physical, mechanical, and optical properties.
  • antioxidants are divided into three main groups: primary antioxidants, secondary antioxidants and alkyl radical scavengers.
  • alkyl radical scavengers are allocated to the group of primary antioxidants.
  • alkyl radical scavengers are considered as a third group of antioxidants, in addition to the primary antioxidants and secondary antioxidants.
  • Primary antioxidants are known to prevent polymer degradation by trapping free radicals. In a typical reaction, primary antioxidants donate hydrogen to the peroxy (ROO*), hydroxy (*OH) or alkoxy (RO*) radicals that transfer them into inert species.
  • ROO* peroxy
  • hydroxy *OH
  • RO* alkoxy
  • Scheme 1 Mechanism of peroxy radical quenching with a phenolic primary antioxidant.
  • the one or more primary antioxidant(s) comprise(s) a phenolic antioxidant. It has been found that phenolic antioxidants provide less discoloration of the polymer than aromatic amine antioxidants. Thus, phenolic antioxidants are particularly useful for light-colored polymers, for example for polymers obtained from transparent fractions of polyolefin recycling material.
  • the one or more primary antioxidant(s) is/are preferably selected from the group consisting of 2,6-di-tert-butyl-4-methyl phenol, pentaerythrityl-tetrakis(3-(3’,5’-di-tert-butyl-4- hydroxyphenyl)propionate, octadecyl 3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate, 1 ,3,5- tri-methyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxyphenyl)benzene, 2,2’-thiodiethylenebis-(3,5-di- tert-butyl-4-hydroxyphenyl)propionate, calcium (3,5-di-tert-butyl-4-hydroxy benzyl monoethyl- phosphonate), 1 ,3,5-tris(3’,5’-di-tert-butyl
  • some primary antioxidants are particularly suitable for stabilization of polypropylene recycling material, and the one or more primary antioxidant(s) is/are more preferably selected from the group consisting of pentaerythrityl-tetrakis(3-(3’,5’-di- tert-butyl-4-hydroxyphenyl)propionate (e.g., Irganox 1010®, BASF), 1 ,3,5-tri-methyl-2,4,6-tris- (3,5-di-tert-butyl-4-hydroxyphenyl)benzene (e.g., Irganox 1330 FF®, BASF), 2, 5,7,8- tetramethyl-2(4’,8’,12’-trimethyltridecyl)chroman-6-ol (e.g., Irganox E201®, BASF) and any combination thereof.
  • the one or more primary antioxidant(s) is/are more preferably selected from the group consisting of pentaerythrityl
  • the most preferred antioxidant is pentaerythrityl-tetrakis(3-(3’,5’-di-tert- butyl-4-hydroxyphenyl)propionate (e.g., Irganox 1010®, BASF).
  • the polypropylene recycling material is extrusion-blended, based on the total weight of the stabilized polypropylene recycled product, with from 0.02 to 0.25 wt.-%, preferably from 0.03 to 0.15 wt.-%, more preferably from 0.03 to 0.12 wt.-%, such as from 0.04 to 0.08 wt.-%, of the one or more primary antioxidant(s).
  • the polypropylene recycling material is preferably extrusion-blended with one to three, more preferably with one or two and most preferably with one primary antioxidant, wherein the primary antioxidants are preferably selected from the compounds depicted above.
  • Primary antioxidants are preferably selected from the compounds depicted above.
  • Secondary antioxidants are known to act as hydroperoxide decomposer. Basically, they decompose hydroperoxides into non-reactive products before they start decomposing with formation of alkoxy and hydroxy radicals. Secondary antioxidants do not react with radicals.
  • a typical reaction with a secondary antioxidant (a phosphite antioxidant) is depicted in the following scheme: Scheme 2: Main mechanism of peroxide decomposition by a phosphite secondary antioxidant.
  • Typical secondary antioxidants are organic phosphorous compounds (e.g., phosphites and phosphonites) and thioethers.
  • the one or more secondary antioxidant(s) is/are preferably selected from the group consisting of tris(2,4-di-tert-butylphenyl)phosphite, tetrakis-(2,4-di-tert-butylphenyl)-4,4’-biphenylen-di- phosphonite, di-stearyl-pentaerythrityl-di-phosphite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, 2-(1 ,1-dimethylethyl)-6-methyl-4-[3-[[2, 4,8,10-tetrakis(1 , 1 -dimethylethyl)di- benzo[d,f][1 ,3,2]dioxaphosphepin-6-yl]oxy]propyl]phenol, di-stearyl-thio-di-propionate, di- lauryl-thi
  • the one or more secondary antioxidant(s) is/are organic phosphorous secondary antioxidant(s), preferably selected from the group consisting of tris(2,4-di-tert- butylphenyl)phosphite, tetrakis-(2,4-di-tert-butylphenyl)-4,4’-biphenylen-di-phosphonite, di- stearyl-pentaerythrityl-di-phosphite, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, 2-(1 , 1- dimethylethyl)-6-methyl-4-[3-[[2,4,8,10-tetrakis(1 ,1-dimethylethyl)di- benzo[d,f][1 ,3,2]dioxaphosphepin-6-yl]oxy]propyl]phenol, and any combination thereof. It has been found that organic phosphorous secondary antioxidant(
  • the one or more secondary antioxidant(s) is/are organic phosphorous secondary antioxidant(s), selected from the group of consisting of tris(2,4-di-tert- butylphenyl)phosphite (e.g., Irgafos 168 (FF)®, BASF), bis(2,4-dicumylphenyl)pentaerythritol diphosphite (e.g., Doverphos S-9228 CT®, Dover Chemical), 2-(1 ,1-dimethylethyl)-6-methyl- 4-[3-[[2,4,8,10-tetrakis(1 ,1-dimethylethyl)di-benzo[d,f][1 ,3,2]dioxaphosphepin-6- yl]oxy]propyl]phenol (e.g., Sumilizer GP®, Sumitomo Chemical) and any combination thereof; with tris(2,4-di-tert-butyl
  • the polypropylene recycling material is extrusion-blended at least with 2-(1 ,1-dimethylethyl)-6-methyl-4-[3-[[2,4,8,10-tetrakis(1 ,1-dimethylethyl)di- benzo[d,f][1 ,3,2]dioxaphosphepin-6-yl]oxy]propyl]phenol (e.g., Sumilizer GP®, Sumitomo Chemical).
  • 2-(1 ,1-dimethylethyl)-6-methyl-4-[3-[[2,4,8,10-tetrakis(1 ,1-dimethylethyl)di- benzo[d,f][1 ,3,2]dioxaphosphepin-6-yl]oxy]propyl]phenol e.g., Sumilizer GP®, Sumitomo Chemical
  • the polypropylene recycling material is extrusion-blended at least with tris(2,4-di-t-butylphenyl)phosphite (e.g., Irgafos 168 (FF)®, BASF).
  • the polypropylene recycling material is extrusion-blended, based on the total weight of the stabilized polypropylene recycled product, with from 0.02 to 0.28 wt.-%, preferably from 0.03 to 0.20 wt.-%, more preferably from 0.04 to 0.18 wt.-%, such as from 0.05 to 0.10 wt.-%, of the one or more secondary antioxidant(s).
  • the polypropylene recycling material is preferably extrusion-blended with one to three, more preferably with one or two and most preferably with one secondary antioxidant, wherein the secondary antioxidants are preferably selected from the compounds depicted above.
  • metal deactivators trap metals that may generate radicals.
  • transition metals e.g., Ti, Fe, Cu, Mn and Co
  • ROOH hydroperoxides
  • a typical mechanism of hydroperoxide degradation is depicted in the following scheme:
  • Metal deactivators are usually chelating agents that form stable complexes with transition metals to prevent the reaction of transition metals with peroxides.
  • metal deactivators In contrast to primary antioxidants containing phenolic groups, which cannot form stable complexes with the transition metals, metal deactivators contain multiple atoms with lone pair of electrons (e.g., O, N, S and P) that could be given to the transition metal ion, thus forming covalent bonds.
  • phenolic antioxidants such as pentaerythrityl- tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate, do not form stable complexes with transition metals to prevent the reaction of transition metals with peroxides, and thus are not metal deactivators.
  • Metal deactivators can form complexes with transition metals comprising the range from hard cations (e.g., Ti 4+ and Fe 3+ ) to soft cations (e.g., Cu + ).
  • Metal deactivators usually act as chelating agents that form stable complexes, for example also with hard cations of the main group metals, such as Ca 2+ and Al 3+ . It has been found that besides the transition metals, also metals of the main groups may facilitate degradation of polypropylene.
  • the one or more metal deactivator(s) is/are preferably selected from the group consisting of
  • the one or more metal deactivator(s) is/are phenolic chelating agent(s), preferably selected from the group consisting of N,N’-bis (3(3’,5’-di-tert-butyl-4’- hydroxyphenyl)propionyl)hydrazine (e.g., Irganox MD 1024®, BASF), 2,2’-oxamido bis-(ethyl- 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (e.g., Palmarole MDA. P. 11 G2®), and the combination thereof.
  • phenolic chelating agent(s) preferably selected from the group consisting of N,N’-bis (3(3’,5’-di-tert-butyl-4’- hydroxyphenyl)propionyl)hydrazine (e.g., Irganox MD 1024®, BASF), 2,2’-oxamido bis-(e
  • At least two metal deactivator(s) are used, wherein the metal deactivators mainly target at least two different metals or groups of metals.
  • the polypropylene recycling material is extrusion-blended, based on the total weight of the stabilized polypropylene recycled product, with from 0.05 to
  • O.60 wt.-% preferably from 0.08 to 0.40 wt.-%, more preferably from 0.10 to 0.25 wt.-%, such as from 0.12 to 0.18 wt.-% of the one or more metal deactivator(s).
  • the polypropylene recycling material is preferably extrusion-blended with one to four, more preferably with one to three and most preferably with one or two metal deactivators, wherein the metal deactivators are preferably selected from the compounds depicted above.
  • the polypropylene recycling material is extrusion-blended with one metal deactivator.
  • the polypropylene recycling material is extrusion-blended with two metal deactivators. Using two metal deactivators may allow targeting at least two different metals or groups of metals.
  • metal deactivator(s) polypropylene recycling material can be sufficiently stabilized from degradation (particularly oxidative/heat degradation).
  • the presence of metal deactivator(s) in polypropylene recycling material resulted in further stabilization from degradation.
  • the use of metal deactivators even allowed a reduction of the content of the primary and secondary antioxidants, while obtaining an even better stabilizing effect.
  • the polypropylene recycling material is extrusion-blended with less than 1 ,500 ppm (i.e., 0.15 wt.-%) of the sum of amounts of the one or more primary antioxidant(s) and the one or more secondary antioxidant(s), based on the total weight of the stabilized polypropylene recycled product.
  • the polypropylene recycling material is extrusion-blended, based on the total weight of the stabilized polypropylene recycled product, with a) from 0.02 to 0.25 wt.-% of the one or more primary antioxidant(s), b) from 0.02 to 0.28 wt.-% of the one or more secondary antioxidant(s), c) from 0.05 to 0.60 wt.% of the one or more metal deactivator(s), and d) from 0.00 to 5.00 wt.-% of further additive(s) and/or carrier(s), e.g., from 0.01 to 0.05 wt.-% of one or more acid scavengers.
  • the polypropylene recycling material can be extrusion-blended, based on the total weight of the stabilized polypropylene recycled product, with a) from 0.03 to 0.15 wt.-% of the one or more primary antioxidant(s), b) from 0.03 to 0.20 wt.-% of the one or more secondary antioxidant(s), c) from 0.08 to 0.40 wt.% of the one or more metal deactivator(s), and d) from 0.00 to 5.00 wt.-% of further additive(s) and/or carrier(s), e.g., from 0.01 to 0.05 wt.-% of one or more acid scavengers.
  • the polypropylene recycling material can be extrusion-blended, based on the total weight of the stabilized polypropylene recycled product, with a) from 0.03 to 0.12 wt.-% of the one or more primary antioxidant(s), b) from 0.04 to 0.18 wt.-% of the one or more secondary antioxidant(s), c) from 0.10 to 0.25 wt.% of the one or more metal deactivator(s), and d) from 0.00 to 5.00 wt.-% of further additive(s) and/or carrier(s), e.g., from 0.01 to 0.05 wt.-% of one or more acid scavengers.
  • the polypropylene recycling material can be extrusion-blended, based on the total weight of the stabilized polypropylene recycled product, with a) from 0.04 to 0.08 wt.-% of the one or more primary antioxidant(s), b) from 0.05 to 0.10 wt.-% of the one or more secondary antioxidant(s), c) from 0.12 to 0.18 wt.% of the one or more metal deactivator(s), and d) from 0.00 to 5.00 wt.-% of further additive(s) and/or carrier(s), e.g., from 0.01 to 0.05 wt.-% of one or more acid scavengers.
  • a polypropylene recycling material is extrusion-blended with a) one or more primary antioxidant(s), comprising at least one phenolic antioxidant, b) one or more secondary antioxidant(s), comprising at least one organic phosphorus antioxidant, c) one or more metal deactivator(s), comprising at least one, preferably at least two, phenolic chelating agent (s), and d) optionally further additive(s) and/or additive carrier(s).
  • a polypropylene recycling material is extrusion-blended with a) one or more primary antioxidant(s), selected from the group consisting of pentaerythrityl- tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate (e.g., Irganox 1010®, BASF), 1 ,3, 5-tri-methyl-2 ,4,6-tris-(3, 5-di-tert.
  • primary antioxidant(s) selected from the group consisting of pentaerythrityl- tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate (e.g., Irganox 1010®, BASF), 1 ,3, 5-tri-methyl-2 ,4,6-tris-(3, 5-di-tert.
  • butyl-4-hydroxyphenyl)benzene e.g., Irganox 1330 FF®, BASF
  • 2,5,7,8-tetramethyl-2(4’,8’,12’-trimethyltridecyl)chroman-6-ol e.g., Irganox E201®, BASF
  • one or more secondary antioxidant(s) selected from the group of consisting of tris(2 ,4- di-tert-butylphenyl)phosphite (e.g., Irgafos 168 (FF)®, BASF), bis(2,4- dicumylphenyl)pentaerythritol diphosphite (e.g., Doverphos S-9228 CT®, Dover Chemical), 2-(1 ,1-dimethylethyl)-6-methyl-4-[3-[[2,4,8,10-tetrakis(1 ,1-dimethylethyl)
  • a polypropylene recycling material is extrusion-blended with a) one or more primary antioxidant(s), comprising at least pentaerythrityl-tetrakis(3-(3’,5’- di-tert-butyl-4-hydroxyphenyl)propionate (e.g., Irganox 1010®, BASF), b) one or more secondary antioxidant(s), comprising at least tris(2,4-di-tert- butylphenyl)phosphite (e.g., Irgafos 168 (FF)®, BASF), c) one or more metal deactivator(s), comprising at least N,N’-bis (3(3’,5’-di-tert-butyl-4
  • Palmarole MDA. P. 11 G2® Palmarole MDA. P. 11 G2®
  • optionally further additive(s) and/or additive carrier(s) optionally further additive(s) and/or additive carrier(s).
  • a polypropylene recycling material is extrusion-blended with a) pentaerythrityl-tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate (e.g.,
  • Irganox 1010®, BASF b) tris(2,4-di-tert-butylphenyl)phosphite (e.g., Irgafos 168 (FF)®, BASF), c) N,N’-bis (3(3’,5’-di-tert. butyl-4’-hydroxyphenyl)propionyl)hydrazine (e.g., Irganox MD 1024®, BASF) and 2,2’-oxamido bis-(ethyl-3-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate) (e.g., Palmarole MDA. P. 11 G2®), and d) optionally further additive(s) and/or additive carrier(s).
  • FF FF
  • N,N’-bis (3(3’,5’-di-tert. butyl-4’-hydroxyphenyl)propionyl)hydrazine
  • a polypropylene recycling material is extrusion-blended with a) one or more primary antioxidant(s), comprising at least pentaerythrityl-tetrakis(3-(3’,5’- di-tert-butyl-4-hydroxyphenyl)propionate (e.g., Irganox 1010®, BASF), b) one or more secondary antioxidant(s), comprising at least 2-(1 ,1-dimethylethyl)-6- methyl-4-[3-[[2,4,8,10-tetrakis(1 ,1-dimethylethyl)di-benzo[d,f][1 ,3,2]dioxaphosphepin-6- yl]oxy]propyl]phenol (e.g., Sumilizer GP®, Sumitomo Chemical), c) one or more metal deactivator(s), comprising at least N,N
  • Palmarole MDA. P. 11 G2® Palmarole MDA. P. 11 G2®
  • optionally further additive(s) and/or additive carrier(s) optionally further additive(s) and/or additive carrier(s).
  • a polypropylene recycling material is extrusion-blended with a) pentaerythrityl-tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate (e.g.,
  • additives a) to c further additives and carriers may be used in the process according to the present invention.
  • one or more acid scavenger(s) and/or one or more alkyl radical scavenger(s) may be further used in the process according to the present invention.
  • a polypropylene recycling material is extrusion-blended with a) one or more primary antioxidant(s), b) one or more secondary antioxidant(s), c) one or more metal deactivator(s), and d) one or more acid scavenger(s) and/or one or more alkyl radical scavenger(s), and optionally further additive(s) and/or additive carrier(s).
  • a polypropylene recycling material is extrusion-blended with at least a) one or more primary antioxidant(s), b) one or more secondary antioxidant(s), c) one or more metal deactivator(s), and d) one or more acid scavenger(s), and optionally one or more alkyl radical scavenger(s).
  • the contents of additives may be used as defined above.
  • Acid scavengers are often used to protect the equipment against corrosion as well as to protect the polymer.
  • hydrochloric acid generated from the chlorine content originating in polyolefins from catalyst residues may be neutralized by acid scavengers. It has been found that acid containing polymers may suffer from discoloration or deterioration during its use.
  • acid scavengers can be divided into the three classes of compounds: metallic soaps, basic metal oxides and hydroxides and mineral agents.
  • the one or more acid scavenger(s) can be selected from the group consisting of a metal oxide and a metal hydroxide such as CaO, MgO, AI2O3, ZnO, Mg(OH)2, Ca(OH)2, and a mineral agent such as hydrotalcite, e.g., Mg4,3Al2(OH)i2.3(CO3).mH2O, and any combination thereof.
  • a metal oxide and a metal hydroxide such as CaO, MgO, AI2O3, ZnO, Mg(OH)2, Ca(OH)2, and a mineral agent such as hydrotalcite, e.g., Mg4,3Al2(OH)i2.3(CO3).mH2O, and any combination thereof.
  • the one or more acid scavenger(s) is/are selected from metal oxides.
  • Metal oxides are preferably used if adhesion issues are important (e.g., in some film applications) and the potential lubricating activity of other acid scavengers should be avoided.
  • the acid scavenger is MgO.
  • the polypropylene recycling material is preferably extrusion-blended, based on the total weight of the stabilized polypropylene recycled product, with from 0.01 to 0.05 wt.-%, more preferably from 0.01 to 0.04 wt.-%, such as from 0.01 to 0.02 wt.-% of the one or more acid scavenger(s).
  • the polypropylene recycling material is preferably extrusion-blended with one or two, preferably one acid scavenger, wherein the acid scavengers are preferably selected from the compounds depicted above.
  • a polypropylene recycling material is extrusion-blended with at least a) pentaerythrityl-tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate (e.g.,
  • Irganox 1010®, BASF b) tris(2,4-di-tert-butylphenyl)phosphite (e.g., Irgafos 168 (FF)®, BASF) and/or 2-(1 ,1- dimethylethyl)-6-methyl-4-[3-[[2,4,8,10-tetrakis(1 ,1-dimethylethyl)di- benzo[d,f][1 ,3,2]dioxaphosphepin-6-yl]oxy]propyl]phenol (e.g., Sumilizer GP®, Sumitomo Chemical), c) N,N’-bis (3(3’,5’-di-tert-butyl-4’-hydroxyphenyl)propionyl)hydrazine (e.g., Irganox MD 1024®, BASF) and 2,2’-oxamido bis-(ethyl-3-(3,
  • alkyl radical scavengers are the third class of antioxidants.
  • the one or more alkyl radical scavenger(s) is/are selected from a lactone alkyl radical scavenger, hydroxylamine and the combination thereof.
  • the one or more alkyl radical scavenger(s) are selected from the group consisting of [4-tert-butyl-2-(5-tert-butyl-2-oxo-3H-1-benzofuran-3-yl)phenyl]-3,5-di-tert-butyl- 4-hydroxybenzoate, hydroxylamine and the combination thereof.
  • hydroxylamine can react with radicals in non-stochiometric manner, thus only a small amount of this additive is needed to achieve excellent performance.
  • hydroxylamine is particularly suitable for polymer applications sensitive to discoloration as hydroxylamine does not contribute to color formation.
  • the polypropylene recycling material is preferably extrusion-blended, based on the total weight of the stabilized polypropylene recycled product, with from 0.002 to 0.02 wt.-%, more preferably from 0.003 to 0.01 wt.-%, such as from 0.004 to 0.008 wt.-% of the one or more alkyl radical scavenger(s).
  • the polypropylene recycling material is preferably extrusion-blended with one or two, preferably one alkyl radical scavenger, wherein the alkyl radical scavengers are preferably selected from the compounds depicted above.
  • a polypropylene recycling material is extrusion-blended with at least a) pentaerythrityl-tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate (e.g.,
  • Irganox 1010®, BASF b) tris(2,4-di-tert-butylphenyl)phosphite (e.g., Irgafos 168 (FF)®, BASF) and/or 2-(1 ,1- dimethylethyl)-6-methyl-4-[3-[[2,4,8,10-tetrakis(1,1-dimethylethyl)di- benzo[d,f][1 ,3,2]dioxaphosphepin-6-yl]oxy]propyl]phenol (e.g., Sumilizer GP®, Sumitomo Chemical), c) N,N’-bis (3(3’,5’-di-tert-butyl-4’-hydroxyphenyl)propionyl)hydrazine (e.g., Irganox MD 1024®, BASF) and 2,2’-oxamido bis-(ethyl-3-(3,5-
  • butyl-4- hydroxyphenyl)propionate (e.g., Palmarole MDA. P. 11 G2®), d) MgO, and e) a lactone alkyl radical scavenger, such as [4-tert-butyl-2-(5-tert-butyl-2-oxo-3H-1- benzofuran-3-yl)phenyl]-3,5-di-tert-butyl-4-hydroxybenzoate or hydroxylamine.
  • a lactone alkyl radical scavenger such as [4-tert-butyl-2-(5-tert-butyl-2-oxo-3H-1- benzofuran-3-yl)phenyl]-3,5-di-tert-butyl-4-hydroxybenzoate or hydroxylamine.
  • additives may be used in the process according to the present invention. These additives may be further stabilizers (i.e. , compounds precluding degradation), modifiers (i.e. , compounds improving polymer performance and processing), fillers, flame retardants, compatibilizers, crosslinkers, colorants and others.
  • stabilizers i.e. , compounds precluding degradation
  • modifiers i.e. , compounds improving polymer performance and processing
  • fillers i.e. , flame retardants, compatibilizers, crosslinkers, colorants and others.
  • UV-absorbers e.g., HALS (Hindered amines light stabilizers) compounds.
  • modifying agents are antistatic - and anti-fogging agents, blowing agents, cling agents, lubricants & resins, nucleating agents and slip - and anti-blocking agents.
  • Particularly preferred modifying agents for use for polypropylene recycled products in film application are lubricants, nucleating agents and slip - and anti-blocking agents.
  • the further additives can be selected from additives known in the art, and can preferably be selected from the group consisting of stabilizers, fillers, colorants, nucleating agents, antistatic agents, and mixtures thereof.
  • additives are generally commercially available and are described, for example, in “Plastic Additives Handbook”, pages 871 to 873, 5 th edition, 2001 of Hans Zweifel.
  • the additives may be added to the polypropylene recycling material as single components, as compositions of some of these additives or as a composition of all additives (i.e., “onepack”), possibly further comprising a carrier (e.g., in the form of a masterbatch).
  • a carrier e.g., in the form of a masterbatch.
  • one additive acts as a “carrier” for the respective other additives.
  • the compositions are further described herein below.
  • additives falling into the definition of additives a) to d) may be regarded to belong to more than one of the described additive classes.
  • at least one compound must be added.
  • a metal deactivator c) can also function as a primary antioxidant a) (e.g., due to its phenolic groups), it is only considered a metal deactivator c), and a further compound must be added as the primary antioxidant a).
  • at least one compound is used for each of the compounds a) to c).
  • the polypropylene recycling material may be extrusion-blended in the presence of additive carriers.
  • Additive carriers are generally known in the art.
  • a masterbatch is a concentrated mixture obtained by the distribution of additives into a polymer carrier, preferably a polyolefin resin such as a polypropylene and/or polyethylene resin.
  • Polyolefin resin can be semi-crystalline or can have cross-linkable silicon-containing groups, e.g., as described in EP 2657284 B1 and US 11 ,186,711 B2.
  • the carrier comprises a C3-C5 alpha-olefin homo- or copolymer.
  • the comonomer content is preferably at least 2.0 wt.%, more preferably at least 5.0 wt.%, and preferably not more than 25 wt.-%, based on the total weight of the copolymer.
  • the comonomer is preferably selected from C2-C8 alpha-olefins, more preferably from C2-C4 alpha-olefins and most preferably the comonomer is ethylene.
  • the present invention also relates to a composition for stabilizing a polypropylene recycling material against degradation, preferably oxidative and/or thermal degradation, comprising, preferably consisting of: a) one or more primary antioxidant(s), b) one or more secondary antioxidant(s), c) one or more metal deactivator(s), and d) optionally further additive(s) and/or additive carrier(s).
  • the polypropylene recycling material intended for stabilization comprises, based on the total weight of the polypropylene recycling material, from 2 to less than 20,000 ppm of the sum of contents of the transition metals selected from titanium (Ti), zinc (Zn), copper (Cu) and iron (Fe), determined by X-ray fluorescence (XRF) spectroscopy as described herein.
  • the composition comprises, preferably consists of a) one or more primary antioxidant(s), comprising at least one phenolic antioxidant, b) one or more secondary antioxidant(s), comprising at least one organic phosphorus antioxidant, c) one or more metal deactivator(s), comprising at least one, preferably at least two, phenolic chelating agent (s), and d) optionally further additive(s) and/or additive carrier(s).
  • the compounds a) to d) can generally by as defined above in the context of the process according to the present invention.
  • a preferred further additive is one or more acid scavengers, such as a metal oxide, e.g., MgO.
  • the composition comprises, preferably consists of a) one or more primary antioxidant(s), selected from the group consisting of pentaerythrityl- tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate (e.g., Irganox 1010®, BASF), 1 ,3,5-tri-methyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxyphenyl)benzene (e.g.,
  • Irganox 1330 FF®, BASF 2,5,7,8-tetramethyl-2(4’,8’,12’-trimethyltridecyl)chroman-6-ol
  • b) one or more secondary antioxidant(s) selected from the group of consisting of tris(2 ,4- di-tert-butylphenyl)phosphite (e.g., Irgafos 168 (FF)®, BASF), bis(2,4- dicumylphenyl)pentaerythritol diphosphite (e.g., Doverphos S-9228 CT®, Dover Chemical), 2-(1 ,1-dimethylethyl)-6-methyl-4-[3-[[2,4,8,10-tetrakis(1 ,1-dimethylethyl)di- benzo[d,f][1 ,3,2]di
  • secondary antioxidant(s) selected from the group of consisting of tris(2 ,
  • Palmarole MDA. P. 11 G2® and the combination thereof, preferably the combination thereof, and d) optionally further additive(s) and/or additive carrier(s).
  • the composition comprises, preferably consists of a) one or more primary antioxidant(s), comprising at least pentaerythrityl-tetrakis(3-(3’,5’- di-tert-butyl-4-hydroxyphenyl)propionate (e.g., Irganox 1010®, BASF), b) one or more secondary antioxidant(s), comprising at least tris(2,4-di-tert- butylphenyl)phosphite (e.g., Irgafos 168 (FF)®, BASF), c) one or more metal deactivator(s), comprising at least N,N’-bis (3(3’,5’-di-tert-butyl-4’- hydroxyphenyl)propionyl)hydrazine (e.g., Irganox MD 1024®, BASF) and 2,2’-oxamido bis-(ethyl-3-(3,5-di
  • Palmarole MDA. P. 11 G2® Palmarole MDA. P. 11 G2®
  • optionally further additive(s) and/or additive carrier(s) optionally further additive(s) and/or additive carrier(s).
  • the composition comprises, preferably consists of a) pentaerythrityl-tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate (e.g.,
  • Irganox 1010®, BASF b) tris(2,4-di-tert-butylphenyl)phosphite (e.g., Irgafos 168 (FF)®, BASF), c) N,N’-bis (3(3’,5’-di-tert-butyl-4’-hydroxyphenyl)propionyl)hydrazine (e.g., Irganox MD 1024®, BASF) and 2,2’-oxamido bis-(ethyl-3-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate) (e.g., Palmarole MDA. P. 11 G2®), and d) optionally further additive(s) and/or additive carrier(s).
  • FF FF
  • N,N’-bis (3(3’,5’-di-tert-butyl-4’-hydroxyphenyl)propionyl)hydrazine
  • the composition comprises, preferably consists of a) one or more primary antioxidant(s), comprising at least pentaerythrityl-tetrakis(3-(3’,5’- di-tert-butyl-4-hydroxyphenyl)propionate (e.g., Irganox 1010®, BASF), b) one or more secondary antioxidant(s), comprising at least 2-(1 ,1-dimethylethyl)-6- methyl-4-[3-[[2,4,8,10-tetrakis(1 ,1-dimethylethyl)di-benzo[d,f][1 ,3,2]dioxaphosphepin-6- yl]oxy]propyl]phenol (e.g., Sumilizer GP®, Sumitomo Chemical), c) one or more metal deactivator(s), comprising at least N,N’-bis (3(3’,5’-di-tert-
  • Palmarole MDA. P. 11 G2® and d) optionally further additive(s) and/or additive carrier(s), e.g., one or more acid scavengers such as MgO.
  • additive(s) and/or additive carrier(s) e.g., one or more acid scavengers such as MgO.
  • the composition comprises, preferably consists of a) pentaerythrityl-tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)propionate (e.g.,
  • the composition may further comprise one or more acid scavenger(s), and optionally one or more alkyl radical scavenger(s), wherein these compounds are preferably as described above in the context of the process.
  • Further additives and additive carriers may be present in the composition as also described above.
  • the composition comprises, based on the total weight of the composition: a) from 4.0 to 40.0 wt.-% of the one or more primary antioxidant(s), b) from 6.5 to 80.0 wt.-% of the one or more secondary antioxidant(s), c) from 13.5 to 75.0 wt.-% of the one or more metal deactivator(s), and d1) from 0.0 to 75.0 wt.-% of further additive(s), e.g., from 1.0 to 40.0 wt.-% of one or more acid scavengers, wherein the components a) to d1) add up to 100%.
  • further additive(s) e.g., from 1.0 to 40.0 wt.-% of one or more acid scavengers, wherein the components a) to d1) add up to 100%.
  • the composition comprises, based on the total weight of the composition: a) from 10.0 to 30.0 wt.-% of the one or more primary antioxidant(s), b) from 15.0 to 60.0 wt.-% of the one or more secondary antioxidant(s), c) from 20.0 to 65.0 wt.-% of the one or more metal deactivator(s), and d1) from 0.0 to 65.0 wt.-% of further additive(s) e.g., from 1.0 to 30.0 wt.-% of one or more acid scavengers, wherein the components a) to d1) add up to 100%.
  • further additive(s) e.g., from 1.0 to 30.0 wt.-% of one or more acid scavengers, wherein the components a) to d1) add up to 100%.
  • the composition comprises, based on the total weight of the composition: a) from 15.0 to 20.0 wt.-% of the one or more primary antioxidant(s), b) from 20.0 to 40.0 wt.-% of the one or more secondary antioxidant(s), c) from 30.0 to 60.0 wt.-% of the one or more metal deactivator(s), and d1) from 0.0 to 60.0 wt.-% of further additive(s) e.g., from 1.0 to 20.0 wt.-% of one or more acid scavengers, wherein the components a) to d1) add up to 100%.
  • further additive(s) e.g., from 1.0 to 20.0 wt.-% of one or more acid scavengers, wherein the components a) to d1) add up to 100%.
  • the composition comprises, based on the total weight of the composition: a) from 15.0 to 20.0 wt.-% of the one or more primary antioxidant(s), b) from 20.0 to 40.0 wt.-% of the one or more secondary antioxidant(s), c) from 30.0 to 60.0 wt.-% of the one or more metal deactivator(s), and d1) from 0.0 to 10.0 wt.-% of further additive(s) e.g., from 1.0 to 10.0 wt.-% of one or more acid scavengers, wherein the components a) to d1) add up to 100%.
  • further additive(s) e.g., from 1.0 to 10.0 wt.-% of one or more acid scavengers, wherein the components a) to d1) add up to 100%.
  • the composition may be combined with an additive carrier preferably selected from the carriers described above.
  • the additive carrier is a polyolefin resulting in a masterbatch composition.
  • the composition (1) is combined with an additive carrier in a weight ratio of composition to additive carrier of from 5 : 95 to 70 : 30.
  • the additive carrier may be present in the final composition in 30 to 95 wt.-%, based on the total weight of the so formed composition (2) comprising the additive carrier.
  • the composition (2) comprises, based on the total weight of the composition: a) from 0.2 to 20.0 wt.-% of the one or more primary antioxidant(s), b) from 0.3 to 30.0 wt.-% of one or more secondary antioxidant(s), c) from 0.5 to 45.0 wt.-% of one or more metal deactivator(s), d1) from 0.0 to 10.0 wt.-% of further additive(s), e.g., from 0.1 to 10.0 wt.-% of one or more acid scavengers, and d2) from 30.0 to 95.0 wt.-% of additive carrier(s), wherein the components a) to d2) add up to 100%.
  • the composition (2) comprises, based on the total weight of the composition: a) from 0.3 to 15.0 wt.-% of the one or more primary antioxidant(s), b) from 0.4 to 25.0 wt.-% of one or more secondary antioxidant(s), c) from 0.8 to 40.0 wt.-% of one or more metal deactivator(s), d1) from 0.0 to 5.0 wt.-% of further additive(s), e.g., from 0.1 to 5.0 wt.-% of one or more acid scavengers, and d2) from 30.0 to 95.0 wt.-% of additive carrier(s), wherein the components a) to d2) add up to 100%.
  • the present invention is further directed to a stabilized polypropylene recycled product obtainable by the process according to any of the above-described embodiments.
  • the stabilized polypropylene recycled product is stabilized against degradation, preferably oxidative and/or thermal degradation. Accordingly, the degradation of the stabilized polypropylene recycled product is decelerated and/or minimized. This can be seen in the change of the oxidation induction time (OIT) at 200 °C and enhanced oxidation induction temperature, as well as on the presence of other degradation products (e.g., acetic acid etc.) and/or volatile compounds, as shown in the examples herein below.
  • OIT oxidation induction time
  • the present invention also relates to the use of the composition according to any one of the above-described embodiments for stabilizing a polypropylene recycling material against degradation, preferably oxidative and/or thermal degradation.
  • melt flow rates were measured with a load of 2.16 kg (MFR 2 ) at 230 °C as indicated.
  • the melt flow rate is that quantity of polymer in grams which the test apparatus standardized to ISO 1133 extrudes within 10 minutes at a temperature of 230 °C under a load of 2.16 kg.
  • All calibration samples and samples to be analyzed were prepared in similar way, on molten pressed plates. About 2 to 3 g of compounds to be analyzed were melted at 190°C. Subsequently, for 20 seconds, 60 to 80 bar pressure was applied in a hydraulic heating press. Next, the samples were cooled to room temperature in 40 seconds in a cold press under the same pressure, in order to control the morphology of the compound. The thickness of the plates was controlled by metallic calibrated frame plates 2.5 cm by 2.5 cm, 100 to 200 pm thick (depending MFR from the sample); two plates were produced in parallel at the same time and in the same conditions. The thickness of each plate was measured before any FTIR measurements were performed; all plates were between 100 to 200 pm thick.
  • the pressing process was repeated three times to increase homogeneity by pressing and cutting the sample in the same conditions as described before.
  • Standard transmission FTIR spectroscope such as Bruker Vertex 70 FTIR spectrometer was used with the following set-up: o a spectral range of 4000-400 cm' 1 , o an aperture of 6 mm, o a spectral resolution of 2 cm' 1 , o with 16 background scans, 16 spectrum scans, o an interferogram zero filling factor of 32 o Norton Beer strong anodization.
  • FTIR is a secondary method
  • several calibration standards were compounded to cover the targeted analysis range, typically from: o 0.2 wt.-% to 2.5 wt.-% for PA o 0.1 wt.-% to 5 wt.-% for PS o 0.2 wt.-% to 2.5 wt.-% for PET o 0.1 wt.-% to 4 wt.-% for PVC
  • Borealis HC600TF as iPP
  • Borealis FB3450 as HDPE
  • RAMAPET N1S Indorama Polymer
  • Ultramid® B36LN BASF
  • Styrolution PS 486N Ineos
  • HIPS High Impact Polystyrene
  • PVC Inovyn PVC 263B under powder form
  • Additional antioxidant such as Irgafos 168 (3000 ppm) was added to minimize the degradation.
  • the FTIR calibration principle was the same for all the components: the intensity of a specific FTI R band divided by the plate thickness is correlated to the amount of component determined by 1 H or 13 C solution state NMR on the same plate.
  • Each specific FTIR absorption band was chosen due to its intensity increase with the amount of the component concentration and due to its isolation from the rest of the peaks, whatever the composition of the calibration standard and real samples.
  • the wavelength for each calibration band was: o 3300 cm' 1 for PA, o 1601 cm' 1 for PS, o 1410 cm' 1 for PET, o 615 cm- 1 for PVC, o 1167 cm' 1 for iPP.
  • Ei is the absorbance intensity of the specific band related to the polymer component i (in a.u. absorbance unit, values see above), d is the thickness of the sample plate,
  • Ai and Bi are two coefficients of correlation determined for each calibration curve. No specific isolated band can be found for C2-rich fraction and as a consequence the C2-rich fraction is estimated indirectly,
  • X C2 rich 100 — (x ipp + X PA + X ps + X PET + X EVA + X pvc + X cflalk + ta(c )
  • the content of inorganic elements was determined by X-ray fluorescence (XRF).
  • XRF X-ray fluorescence
  • the instrument used for the XRF measurements was a wavelength dispersive Zetium (2,4kW) from Malvern Panalytical.
  • the instrument was calibrated with Adpol, RoHs, Toxel standards from Malvern Panalytical and from a custom set of calibration standards (referred to in the following as “Custom”) also from Malvern Panalytical according to the following table:
  • the analyses are done under vacuum on a plaque with a diameter of 40mm and a thickness of 2mm.
  • the method is generally used to determine the quantitative content of Na, Mg, Al, Si, P, S, Ca, Ti, Zn, Cu, Br, Cl, K, Sr, Fe in polyolefin matrix within defined ranges of these standards.
  • the pellet samples were air-tightly stored and kept until analysis.
  • the samples were analysed by HS/GC/MS in order to determine acetic acid as the relevant marker substance. Therefore, about 10 g of the polymer sample were cryo-milled with the aid of liquid nitrogen and a rotor mill (ring sieve, aperture size: 1 mm). Directly after milling an aliquot of 2.000 ⁇ 0.100 g of the cryo-milled portion was weighed in a 20 ml HS vial and tightly sealed with a PTFE cap. The samples were analysed by HS/GC/MS at 100 °C / 2 h isothermal headspace conditions.
  • Oven temperature 200 °C (standard), 100 °C (sample)
  • T ransfer line temperature 210 °C
  • Carrier gas Helium 5.0
  • EICs extracted ion chromatograms
  • the standard concentration of a marker substance in the HS vial was calculated according equation 1 , where the marker substance concentration in the liquid standard ⁇ c standard ⁇ was mu
  • a HS volume of 20 ml is used by default.
  • Equation 1 For each marker compound in the standard a response factor (Rf ) was calculated according equation 2. Equation 2
  • the marker compound concentration is divided by the integrated peak area of the corresponding marker compound in the EIC (Peak area standard ).
  • Equation 3 In order to estimate the respective marker compound concentration in the headspace of a sample (Cg ample ), equation 3, was used. Therefore, the obtained response factor from equation 2 is multiplied by the peak area of the corresponding marker compound in the EIC of the sample run (Peak area Sample ). Equation 3
  • TD GC-FID for the screening of low-boiling substances (LBS) and high-boiling substances (HBS)
  • This method describes the semi-quantitative determination of organic compounds emitting from polyolefins. It is similar to the VDA 278 (October 2011) but includes specific adjustments.
  • the pellet samples were air-tightly stored and kept until analysis.
  • An aliquot of 60 ⁇ 5 mg was prepared from the stored sample. Trimming the aliquot aimed for a maximum coherent area. It was not the aim to create the largest possible surface area by cutting the aliquot into smaller pieces.
  • the diameter of the sample injection tube was used first. Length and thickness were chosen accordingly, considering the specified aliquot weight.
  • the aliquot was directly desorbed using heat and a flow of helium gas. Volatile and semi-volatile organic compounds were extracted into the gas stream and cryo-focused prior to the injection into a gas chromatographic (GC) system for analysis.
  • GC gas chromatographic
  • the method comprised two extraction stages: In the analysis of low-boiling substances (LBS) the aliquot was desorbed at 90 °C for 30 min to determine volatile organic compounds in the boiling I elution range up to n-C25 (n- pentacosane). The analysis of high-boiling substances (HBS) involved a further desorption step of the same aliquot at 120 °C for 60 min to determine semi-volatile compounds in the boiling I elution range from n-C14 (n-tetradecane) to n-C32 (n-dotriacontane).
  • LBS low-boiling substances
  • HBS high-boiling substances
  • the LBS is calculated as toluene equivalent (TE) and the HBS is calculated as hexadecane equivalent (HE) applying a semi-quantitation and a respective calibration.
  • the result is expressed in “pg/g”. Integration parameters for the LBS and HBS evaluation were chosen in such way that theticianarea reject" corresponds to the area of 1 pg/g (TE and HE, respectively). Thus, smaller peaks did not add to the semi-quantitative result.
  • the GC oven program was kept the same, no matter if a calibration run, an LBS run or an HBS run had been performed.
  • N-Methyl-N-trimethylsilyl- trifluoroacetamide (MSTFA, CAS no. 24589-78-4) were added to one of the extract portions for derivatisation and kept at 100 °C for 20 min. The other extract portion was not derivatised. Both solutions were tested by GC using a flame ionisation detector (FID) and a DB-1 type column. Helium was used as carrier gas. “Stearate” content was determined as the sum of myristic acid (CAS-no. 544-63-8), palmitic acid (CAS-no. 57-10-3), stearic acid (CAS-no. 57- 11-4) and arachidic acid (506-30-9).
  • Sumilizer GP refers to (6-3-(3-tert-butyl-4-hydroxy-5- methylphenyl) propoxy)-2,4,8,10-tetra-tert. butyldibenz (d,t)(1.3.2) dioxaphosphepin) (CAS- no. 203255-81-6).
  • Antioxidant content was determined via high performance liquid chromatography (HPLC) after extraction with ethyl acetate. Therefore, about 10 g of the polymer sample were cryo-milled with the aid of liquid nitrogen and a rotor mill (ring sieve, aperture size: 1 mm). After that, a portion of approximately 0.5 g of the milled sample was extracted using ethyl acetate as a solvent. Extraction was performed at 95 °C for 90 min under constant stirring. After letting the mixture cool down to room temperature again it was filtrated and put to the HPLC test for the quantification of antioxidants. The HPLC system was equipped with a C18 column for the separation and a diode array detector (DAD) for detection.
  • DAD diode array detector
  • the detection wavelength was set to 276 nm and the quantitation was performed with respective calibration standards for N,N’- bis(3(3’,5’-di-tert-butyl-4’-hydroxyphenyl)propionyl)hydrazine (CAS no. 32687-78-8), Pentaerythrityl-tetrakis(3-(3’,5’-di-tert.-butyl-4-hydroxyphenyl)-propionate (CAS no. 6683-19- 8), Tris(2,4-di-tert-butylphenyl)phosphite (CAS no. 31570-04-4) and Tris (2,4-di-tert- butylphenyl)phosphate (CAS no. 95906-11-9). Further HPLC parameters are listed below: c) Oxidation induction (01) time and oxidation induction temperature measurement
  • the oxidation induction time (01 time) at 200 °C was determined with a TA Instrument Q20 according to ISO11357-6. Calibration of the instrument was performed with indium (In), zinc (Zn), and tin (Sn). Each polymer sample (cylindrical geometry with a diameter of 4 mm and thickness of 650pm ⁇ 100pm) was placed in an open aluminum crucible, heated from 20 °C to 200 °C at a rate of 20 °C min -1 in nitrogen (>99.95 vol.% N2) with a gas flow rate of 50 mL min -1 , and allowed to rest for 5 min before the atmosphere was switched to pure oxygen (>99.95 vol.% O2), also at a flow rate of 50 mL min -1 . The samples were maintained at constant temperature, and the exothermal heat associated with oxidation was recorded. The oxidation induction time was the time interval between the initiation of oxygen flow and the onset of the oxidative reaction. Each presented data point was the average of two independent measurements.
  • the oxidation induction temperature was determined with a TA Instrument Q20 according to ISO11357-6. Calibration of the instrument was performed with indium (In), zinc (Zn), and tin (Sn). Each polymer sample (cylindrical geometry with a diameter of 4 mm and thickness of 650pm ⁇ 100pm) was placed in an open aluminum crucible, immediately heated to 350 °C with a gas flow rate of 50 mL min -1 under pure oxygen (>99.95 vol.% O2). The exothermal heat associated with oxidation was recorded. The oxidation induction temperature is the onset of the oxidative reaction. The oxidation induction temperature was evaluated according to ISO11357-6. d) Crystex analysis, crystalline fraction (CF) and soluble fraction (SF)
  • the crystalline and amorphous fractions are separated through temperature cycles of dissolution at 160 °C, crystallization at 40 °C and re-dissolution in 1 ,2,4-trichlorobenzene at 160 °C.
  • Quantification of SF and CF and determination of ethylene content (C2) are achieved by means of an integrated infrared detector (IR4) and for the determination of the intrinsic viscosity (IV) an online 2-capillary viscometer is used.
  • the IR4 detector is a multiple wavelength detector measuring IR absorbance at two different bands (CH3 stretching vibration (centered at app. 2960 cm' 1 ) and the CH stretching vibration (2700-3000 cm' 1 ) that are serving for the determination of the concentration and the ethylene content in ethylene-propylene copolymers.
  • the IR4 detector is calibrated with series of 8 EP copolymers with known ethylene content in the range of 2 wt.-% to 69 wt.-% (determined by 13 C-NMR) and each at various concentrations, in the range of 2 and 13 mg/ml. To encounter for both features, concentration and ethylene content at the same time for various polymer concentrations expected during Crystex analyses the following calibration equations were applied:
  • the CH 3 /1000C is converted to the ethylene content in wt.-% using following relationship:
  • the samples to be analyzed are weighed out in concentrations of 10 mg/ml to 20 mg/ml. To avoid injecting possible gels and/or polymers which do not dissolve in TCB at 160 °C, like PET and PA, the weighed out sample was packed into a stainless steel mesh MW 0, 077/D 0.05 mm.
  • the sample is dissolved at 160 °C until complete dissolution is achieved, usually for 60 min, with constant stirring of 400 rpm. To avoid sample degradation, the polymer solution is blanketed with the N2 atmosphere during dissolution.
  • BHT 2,6-tert-butyl-4- methylphenol
  • a defined volume of the sample solution is injected into the column filled with inert support where the crystallization of the sample and separation of the soluble fraction from the crystalline part is taking place. This process is repeated two times. During the first injection the whole sample is measured at high temperature, determining the IV [dl/g] and the C2 [wt.- %] of the PP composition.
  • a polypropylene fraction from a German post-consumer plastic trash fulfilling the specification DSD323-2 was used as the precursor mixed-plastic recycling stream.
  • the content of flexible polymer articles was 71.1 wt.-% (with a PP:PE ratio of 0.3:1).
  • Example IE9 a German post-consumer plastic trash was used that was enriched in post-consumer flexible polypropylene articles having a content of flexible polymer articles of 81.4 wt.-% (with a PP:PE ratio of 23.8:1).
  • the feedstock comprised labels obtained as a by-product from container recycling, such as PET bottles.
  • the process was conducted by the sequence of steps: a) providing the polyolefin recycling streams described above; b) separating via sieving; c) removing metal particles; d) sorting according to polymer type, transparency, coIor and reflectance via optical sorters; e) selecting the polypropylene transparent (only Comparative Example CE4 and Inventive Examples IE8 and IE9) or colored (all other examples) fraction; f) size-reducing via wet grinding; g) washing by cold alkaline wash, hot alkaline wash and rinsing (sub-steps g1a) to g3)); h) mechanical drying followed by thermal drying; i) separating via air sifter and selecting the flexible flake fraction.
  • Examples CE6-8 and IE12-14 originated from labels. Thus, as this feedstock was already pre-sorted and relatively homogeneous, no sorting step was required.
  • the extruder barrel temperatures were set to 20/190/250/220/205/230/220/185/200°C.
  • the screw speed was 80 rpm and the throughput rate was about 10 kg/h.
  • a strand pelletizer with 2 holes having 3 mm in diameter was used to pelletize the polymer.
  • the contents and properties of the polypropylene recycling material are depicted in Tables 4A to 4E below, e.g., in Comparative Examples CE1 and CE5-7 no additives were added.
  • CE1 , CE5 and CE6 were not extruded a second time. Due to the use of different sorting and/or batches of post-consumer plastic waste as well as to the variation in the small-scale pre-compacted samples, the contents and properties may vary between the examples.
  • the pelletized flakes and additives (as listed in Table 3 below) were compounded on a standard co-rotating twin-screw extruder Prism TSE 24 by Thermo Fisher Scientific.
  • the extruder had a diameter of 23.6 mm, a length to diameter ratio (L/D) of 40 and a diameter ratio (Do/Di) of 1.77.
  • the extruder barrel temperatures were set to
  • MB1 to MB12 were prepared, as depicted in Table 2 below.
  • MB1 and MB2 correspond to a basic stabilizer for virgin polymers, which were used in the comparative examples and were mixed with further additives to prepare the inventive examples.
  • the secondary antioxidant 1 was replaced by either a mixture of secondary antioxidant 1 and hydroxylamine (FS301) or by secondary antioxidant 2, respectively.
  • Table 3 Additive addition (in ppm).
  • Table 4B Results (continued).
  • Table 4C Results (continued).
  • SA1-ox denotes the oxidated (inactive) form of SA1.
  • FOG and VOC indicate low- and high-boiling substances (LBS and HBS), as described in the measurement methods.
  • Example CE4 # The amount of additives added in Example CE4 was 1650 ppm of PrA and 1650 ppm of SA1.
  • LOD limit of detection
  • LOQ limit of quantification
  • Examples IE8 and IE9, and CE4 the transparent fraction of the sorting process was selected.
  • the feedstock comprised labels obtained from containers such as PET bottles.
  • Examples CE6-8 and I E12 were prepared from the same batch (with CE6 as the as the starting material for all of these Examples). All samples of the lEs could be sufficiently stabilized.
  • the OIT temperature was measured on the washed flakes, before extrusions. For all three examples, the OIT temperature was 199°C.
  • the improved stabilization in the Inventive Examples over to the Comparative Examples can be seen in the enhanced OIT temperature.
  • the oxidation induction time at 200°C also increased. Further, the degradation products are mostly reduced as depicted by the usually lower contents of volatile organic compounds (VOC) and semi-volatile organic compounds (FOG), as well as of acetic acid.
  • VOC volatile organic compounds
  • FOG semi-volatile organic compounds
  • the stabilization results do not strongly vary based on the kind of the secondary antioxidant used (examples IE2/IE3 vs. IE7).
  • the stabilization effect was independent on the waste samples used (presorted vs. nonpresorted trash; examples IE8 vs. IE9).
  • melt flow rate was lower in the Inventive Examples vs. the Comparative Examples (comparing IE8 and IE9 vs. CE4; or IE12-14 vs. CE6-8).
  • rheological properties could also be improved by the suggested additivation.
  • This also indicates the improved stabilization of the Inventive Examples.
  • Examples CE6-8 and IE12-14 were carried out with a different kind of waste material and they show similar improvements.
  • the suggested additivation is advantageous for different kinds of polypropylene waste materials.
  • IE10 vs.
  • the content of acetic acid can be reduced by the addition of MgO as acid scavenger, by maintaining the high OIT temperature - even at reduced content of metal deactivator.
  • Inventive Examples IE15 and IE16 show that stabilization is reached by the use of only one kind of metal deactivator compound.
  • the recycled products obtained were also measured for their properties via the Crystex method and the results are depicted in Table 5 below.

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Abstract

La présente invention concerne un procédé de stabilisation d'un matériau de recyclage de polypropylène contre la dégradation, de préférence la dégradation oxydative et/ou thermique, ainsi que des compositions pour la stabilisation d'un matériau de recyclage de polypropylène.
PCT/EP2025/069669 2024-07-11 2025-07-10 Stabilisation de matériau de recyclage de polypropylène contre la dégradation Pending WO2026013169A2 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2657284B1 (fr) 2012-04-27 2014-10-29 Borealis AG Mélange maître additif avec homo- ou copolymère alpha-oléfine C3-C5 compris dans le support
US11186711B2 (en) 2016-11-02 2021-11-30 Dow Global Technologies Llc Semi-crystalline polyolefin-based additive masterbatch composition
WO2023118421A1 (fr) 2021-12-22 2023-06-29 Borealis Ag Procédé de recyclage mécanique de polyoléfines
WO2023180222A1 (fr) 2022-03-22 2023-09-28 Borealis Ag Procédé mécanique de recyclage de polyoléfines
WO2023209075A1 (fr) 2022-04-29 2023-11-02 Borealis Ag Mélange de polypropylène mixte souple-plastique (pp-flex)

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2657284B1 (fr) 2012-04-27 2014-10-29 Borealis AG Mélange maître additif avec homo- ou copolymère alpha-oléfine C3-C5 compris dans le support
US11186711B2 (en) 2016-11-02 2021-11-30 Dow Global Technologies Llc Semi-crystalline polyolefin-based additive masterbatch composition
WO2023118421A1 (fr) 2021-12-22 2023-06-29 Borealis Ag Procédé de recyclage mécanique de polyoléfines
WO2023180222A1 (fr) 2022-03-22 2023-09-28 Borealis Ag Procédé mécanique de recyclage de polyoléfines
WO2023209075A1 (fr) 2022-04-29 2023-11-02 Borealis Ag Mélange de polypropylène mixte souple-plastique (pp-flex)

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Title
"Plastic Additives Handbook", 2001, HANS ZWEIFEL, pages: 871 - 873
ANDREAS ALBRECHTMARTINA SANDHOLZERMARKUS GAHLEITNER: "Rapid characterization of high-impact ethylene-propylene copolymer composition by crystallization extraction separation: comparability to standard separation methods", INTERNATIONAL JOURNAL OF POLYMER ANALYSIS AND CHARACTERIZATION, vol. 25, no. 203255-81-6, 2020, pages 581 - 596, XP093295167, DOI: 10.1080/1023666X.2020.1821151
JOURNAL OF POLYMERS AND THE ENVIRONMENT, vol. 30, 2022, pages 494 - 503
SIGNORET: "Alterations of plastic spectra in MIR and the potential impacts on identification towards recycling", RESOURCES, CONSERVATION AND RECYCLING JOURNAL, vol. 161, 2020, XP086249790, DOI: 10.1016/j.resconrec.2020.104980

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