WO2025083231A1

WO2025083231A1 - Process for separating a polyolefin from a polyolefin containing stream

Info

Publication number: WO2025083231A1
Application number: PCT/EP2024/079541
Authority: WO
Inventors: Andreas Albrecht; Joel FAWAZ; Alexandra Romina ALBUNIA; Yi Liu; Noureddine AJELLAL; Mohammad AL-HAJ ALI; Lukas SOBCZAK; Henry Sleijster; Pablo Ivan AGUAYO ARELLANO; Mubashar SATTAR
Original assignee: Borealis GmbH
Current assignee: Borealis GmbH
Priority date: 2023-10-20
Filing date: 2024-10-18
Publication date: 2025-04-24
Anticipated expiration: 2026-04-20

Abstract

The present invention is concerned with a process for separating a polyolefin from a stream comprising a polyolefin of a solvent based recycling (SbR) process. In particular, the present invention relates to such a process that ensures thermal stability of the recycled polyolefin, in particular during the devolatilization steps for removing the solvent. Furthermore, the present invention is concerned with a polyolefin obtainable from such a process.

Description

Process for separating a polyolefin from a polyolefin containing stream

The present invention is concerned with a process for separating a polyolefin from a stream comprising a polyolefin of a solvent based recycling process (SbR). In particular, the present invention relates to such a process that ensures thermal stability of the recycled polyolefin, in particular during the devolatilization steps for removing the solvent. Furthermore, the present invention is concerned with a polyolefin obtainable from such a process.

Background

The challenge of the disposal of accumulated waste plastics and corresponding environmental issues have received widespread attention from the public and academician. Therefore, besides the concepts of the prevention of plastic waste in general and the prevention of leakage of plastic waste into the environment in particular, recycling of waste plastics material has become an important topic. Waste plastics can be turned into resources for new plastic products. Hence, environmental and economic aspects can be combined in recycling and reusing waste plastics material.

There are different methods of plastic recycling commonly known including mechanical [material recycling], advanced physical or solvent based [solution] and chemical processing [(feedstock recycling, thermochemical such as pyrolysis or gasification, solvolysis]. Among these methods, mechanical recycling and chemical recycling are the most widely practiced.

In the solvent based recycling (SbR)-processing a polymer will be initially dissolved in an appropriate solvent and following, either the solubility of the dissolved polymer will be decreased by the addition of a non-solvent (dissolution/precipitation) and/or a solidification of the polymer will be caused by the preferably complete separation of the solvent from the solidified polymer by thermal unit operations (evaporation, drying etc.).

Therefore in polyolefin recycling technology, in particular in a solvent based polyolefin recycling technology, the downstream processing of the product stream is essential for producing a product with low volatiles content. The downstream processing takes place via a separation step such as gravimetric, i.e. liquid-liquid separation, or pressure flashing, where the solution is heated and depressurized in a flash vessel. For example, WO2022/219091 discloses a solvent based recycling process for recycling waste polymer material, the waste polymer material comprising at least one polyolefin, the process comprising the steps of obtaining the waste polymer material comprising the at least one polyolefin; contacting the waste polymer material with at least one dissolving solvent yielding a slurry stream of polymer solution and undissolved solids; screening the slurry stream yielding the undissolved solids and a stream of the polymer solution; vapor-liquid separating the stream of the polymer solution into a polymer-lean vapor stream and a polymer-rich condensed stream; recovering the at least one polyolefin from the polymer-rich condensed stream; wherein the at least one dissolving solvent has a boiling point temperature at 1 bar of equal to or more than 70 °C

Furthermore, WO 2022/219092 discloses a process for the separation of at least one polyolefin from a product stream originating from a polyolefin recycling process, wherein the product stream comprises the at least one polyolefin and a solvent, the process comprising the steps of separating the product stream into a polyolefin-lean stream and a polyolefin-rich stream; separating the polyolefin-rich stream into a first polyolefin-lean vapor stream and a first condensed polyolefin-rich stream; separating the first condensed polyolefin-rich stream into a last polyolefin-lean vapor stream and a last condensed polyolefin-rich stream.

WO 2015/000681 relates to a solvent-based plastics-recycling method which comprises a) mixing the polymer-containing waste with an organic solvent containing at least one thermal stabilizer for polymers, at least one polymer being dissolved in the organic solvent and an insoluble portion of the waste remaining; b) at least partially separating the solution containing at least one polymer and at least one thermal stabilizer from the insoluble part of the waste; c) at least partially separating the organic solvent from the at least one polymer.

N-alkanes may be used as solvent in a polyolefin recycling process, particularly in a solvent based polyolefin recycling process. However, in devolatilisation comprising separation of polyolefin from solvent a temperature of about 250°C or even higher may be used.

During the devolatisation of such solvent based recycling process, not only the solvent but also any active additives, such as stabilizers which may be present in the waste plastics, are generally removed. This means that the polyolefin is quite unprotected against thermal degradation.

Therefore, there is the need for a process for separating a polyolefin from a product stream of a solvent based polyolefin recycling process that ensures thermal stability of the recycled polyolefin during the devolatilisation steps for removing the solvent from the product stream. There is further the need of a process that allows a homogenous distribution of the antioxidant in the polyolefin stream and addition of antioxidant in an amount sufficient for achieving the required thermal stabilization of the recycled polyolefin during devolatilisation steps performed at high temperatures.

Summary of the invention

It has now surprisingly been found that the above mentioned object can be achieved by a process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, the process comprising the steps of:

A) optionally adding a solution or a dispersion, such as a suspension, (s1 ) comprising an antioxidant and preferably a n-alkane to the product stream (a), thereby providing a stabilized product stream;

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the product stream (a) or, when step A) is carried out, from the stabilized product stream;

C) optionally adding a solution or a dispersion, such as a suspension (s2) comprising an antioxidant and preferably a n-alkane to the first polyolefin- rich stream (c) thereby providing a stabilized polyolefin-rich stream;

D) subsequent of step C) when present separating at a temperature of from 150 to 300 °C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream; wherein the process comprises at least one of step A) or step C).

Therefore, the present invention is directed to a separation process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process. The product stream (a) comprises the at least one polyolefin dissolved in a solvent. The process comprises the steps of separating a first polyolefin-rich stream (c) from the product stream (a) or, if step A) is carried out from a stabilized product stream and/or of separating a second polyolefin-rich stream (c’) from a stabilized polyolefin-rich stream. Antioxidants in solution or dispersion, such as a suspension, are added either to the product stream (a) or to the first polyolefin-rich stream (c) or to both the product stream (a) and to the first polyolefin-rich stream (c). It has been surprisingly found that by feeding antioxidants, such as a sterically hindered phenol, in a solution or dispersion, such as a suspension, to a polyolefin/solvent stream prior to a separation step a sufficient amount of antioxidant can be added to avoid an immediate degradation, preferably thermal degradation, of the polyolefin. A high quality products is therefore ensured.

Further the addition of the antioxidants in a solvent or dispersion, such as a suspension, allows a homogenous distribution of the antioxidants in the polyolefin/solvent stream with a minimum energy input for the mixing.

Further protection towards the final application at the customer can be achieved by addition a specific additive (stabilizer, antioxidant) dissolved in n-alkane at the final pelletizing extruder.

Definitions

The expression ‘volatiles’ or ‘volatile compounds’ as used herein has to be understood as compounds having significantly lower molecular weight in comparison to the polyolefin separated in the process of the invention. Such compounds typically are present in the gaseous form when being exposed to a flash separator. Commonly, the volatile compounds are a mixture of volatile hydrocarbons and include the n-alkane of the method of the invention.

‘Flash separators’ have been known in the prior art for decades (also known as low- pressure separators). As it is well known in the art, a liquid feed is passed to a flash vessel operated at a reduced pressure. Thereby a part of the liquid phase vaporizes and can be withdrawn as an overhead stream (or a vapor stream) from the low pressure separator. The part remaining in liquid phase is then withdrawn as a condensed stream from the flash vessel. Operating the low pressure separator under conditions such that both vapor and liquid phases are present in the flash vessel describes this situation.

‘Gravity separators’ or ‘liquid-liquid separators’ as used herein comprise a vessel in which a two-phase (i.e. liquid/liquid) system can be separated. The liquid phase with the lower relative density (polyolefin-lean phase) is withdrawn from the upper end of the vessel whereas the liquid phase with the higher relative density (in the present case the polyolefin-rich phase) is withdrawn from the bottom end of the vessel.

The term ‘vacuum pressure conditions’ as used herein denotes vacuum pressures between 5 mbar to l OO mbar. Pressures lower than 5 mbar are disadvantageous in view of energy consumption and resulting costs. Pressures higher as 100 mbar result in too high amounts of volatiles in the final polymer. The term “primary antioxidants" denotes compounds that react with chainpropagating radicals such as peroxy, alkoxy, and hydroxy radicals in a chain terminating reaction. These antioxidants donate hydrogen to the alkoxy and hydroxy radicals which converts them into inert alcohols and water respectively. They are also known as free radicals scavengers. Primary antioxidants are, for example, sterically hindered phenols and secondary aromatic amines. These compounds come in a wide range of molecular weights, structures, and functionalities. An example of primary antioxidants are sterically hindered phenols. They are very effective radical scavengers during both processing and long-term thermal aging, and are generally non-discoloring. “Sterically hindered phenols" are a known class of primary antioxidants. These compounds act as a primary antioxidants by converting peroxyl radicals to hydroperoxides. Thus, they inhibit autooxidation of organic polymers by reducing the amount of peroxyl radicals.

The term “secondary antioxidant" denotes compounds that decompose hydroperoxides (ROOH) into nonreactive products before they decompose into alkoxy and hydroxy radicals. They are also known as peroxide scavengers. The most common secondary antioxidants are trivalent phosphorus compounds (phosphites). They reduce hydroperoxides to the corresponding alcohols and are themselves transformed into phosphates. Another class of secondary antioxidants are thioethers or organic sulfides. They decompose two molecules of hydroperoxide into the corresponding alcohols and are transformed to sulfoxides and sulfones.

Description of the drawings

Figure 1 shows a schematic layout of the process of the present invention.

Figure 2 shows the Mw of inventive examples IE1 to IE3 and comparative example CE1 vs. the thermal treatment at 270°C under N2 atmosphere.

Figure 3 A) and Figure 3 B) show the molecular weight distribution (MWD) before and after thermal treatment at 250°C for inventive example IE2 and IE3 respectively.

Figure 4 shows the MWD before and after thermal treatment at 250°C for comparative example CE1.

Figure 5 shows the Mw of inventive examples IE2 and IE3 and comparative example CE1 vs. the thermal treatment at 250°C under N2 atmosphere.

Figure 6 shows the MFR2 of the samples IET to IE6’ and CE1 ’ of example 3

Reference signs

(a) product stream (c) first polyolefin-rich stream;

(o’) second polyolefin-rich stream

(s1 ) solution or dispersion, such as a suspension, comprising an antioxidant and preferably and n-alkane, wherein the solution or dispersion is added to the product stream (a)

(s2) solution or dispersion, such as a suspension, comprising an antioxidant and preferably a n-alkane, wherein the solution or dispersion is added to the first polyolefin-rich stream (c)

(c”) third condensed polyolefin-rich stream

Detailed description of the invention

In the most general embodiment of the invention, the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

D) subsequent of step C) when present separating at a temperature of from 150 to 300 °C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream wherein the process comprises at least one of step A) or step C).

Therefore, in one general embodiment the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprises a n-alkane, comprises the steps of: A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising an antioxidant and preferably a n-alkane to the product stream (a), thereby providing a stabilized product stream;

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the stabilized product stream.

Steps C) and step D) are not carried out.

Therefore, in one general embodiment, the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane comprises the steps of:

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the product stream (a);

C) adding a solution or a dispersion, such as a suspension (s2) comprising an antioxidant and preferably a n-alkane to the first polyolefin-rich stream (c) thereby providing a stabilized polyolefin-rich stream;

D) separating at a temperature of from 150 to 300 °C a second polyolefin- rich stream (c’) from the stabilized polyolefin-rich stream.

Step A) is not carried out.

Therefore, in one general embodiment, the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising an antioxidant and preferably a n-alkane to the product stream (a), thereby providing a stabilized product stream;

B) separating at a temperature of from 150 to 300 C a first polyolefin-rich stream (c) from the stabilized product stream;

Both step A) and step C) are carried out. Preferably, the polyolefin in the product stream (a) comprises or consists of polypropylene, or polyethylene or any mixture thereof. Therefore, the polyolefin in the product stream (a) comprises or consists of polypropylene homopolymer(s), polypropylene copolymer(s), polyethylene homopolymer(s), polyethylene copolymer(s) or any mixture thereof. The polyolefin can be, for example, a polymer selected from the list consisting of polyethylene (PE), in particular high density polyethylene (HDPE), low-density polyethylene (LDPE) or linear low- density polyethylene (LLDPE), and polypropylene (PP) or any mixture thereof. Preferably, the polyolefin of the product stream (a) comprises polypropylene homopolymer(s) or polypropylene copolymer(s) or any mixture thereof.

The expression “propylene homopolymer” denotes a propylene polymer that consists of at least 99.0 wt.-%, preferably at least 99.5 wt.-%, more preferably at least 99.8 wt.-% of propylene monomer units, based on the total weight of the propylene polymer, determined by quantitative ¹³C{¹ H} nuclear magnetic resonance (NMR) spectroscopy. In one embodiment, only propylene monomer units are detectable in the propylene homopolymer.

The expression “propylene copolymer” denotes a propylene polymer that generally comprises propylene monomer units and other comonomer units, preferably, ethylene comonomer units and/or one or more alpha-olefin(s) comonomer units having from 4 to 10 carbon atoms, most preferably ethylene comonomer units. Preferably, the content of the propylene monomer units in the propylene copolymer is at least 70 wt.-%, based on the total weight of the propylene copolymer, determined by quantitative ¹³C{¹H}-NMR spectroscopy, or alternatively 70 mol-%, based on the total molar content of the propylene copolymer, determined by quantitative ¹³C{¹ H}-NMR spectroscopy.

More preferably, the polyolefin of the product stream (a) consists of polypropylene.

Therefore, preferably the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the product stream (a) or, when step A) is carried out, from the stabilized product stream; C) optionally adding a solution or a dispersion, such as a suspension (s2) comprising an antioxidant and preferably a n-alkane to the first polyolefin- rich stream (c) thereby providing a stabilized polyolefin-rich stream;

D) subsequent of step C) when present separating at a temperature of from 150 to 300 °C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream, wherein the process comprises at least one of step A) or step C) and wherein the at least one polyolefin comprises or consists of polypropylene..

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the stabilized product stream, wherein the at least one polyolefin comprises or consists of polypropylene.

Steps C) and D) are not carried out.

D) separating at a temperature of from 150 to 300 °C a second polyolefin- rich stream (c’) from the stabilized polyolefin-rich stream, wherein the at least one polyolefin comprises or consists of polypropylene.

Step A) is not carried out.

B) separating at a temperature of from 150 to 300°C a first polyolefin-rich stream (c) from the stabilized product stream;

D) separating at a temperature of from 150 to 300°C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream, wherein the at least one polyolefin comprises or consists of polypropylene..

Step A) and step C) are both carried out.

Solution or dispersion / suspension (s1 ) or solution or dispersion / suspension (s2)

Advantageously, in any embodiment of the invention, a solution or dispersion, such as a suspension, (s1 ) and/or (s2) is added to provide a homogenous distribution of the antioxidant in the streams and prevent degradation, preferably thermal of the polyolefin.

In any embodiment of the invention, the solution or dispersion, such as a suspension, (s1 ) and (s2) comprise an antioxidant. Preferably, the antioxidant comprises or consists of primary antioxidants. Preferred primary antioxidants comprise or consist of a sterically hindered phenol.

With regard to the antioxidants, they preferably comprise or consist of primary antioxidants or secondary antioxidants or combinations thereof. According to the present invention, primary antioxidants alone or in combination with secondary antioxidants are preferred. Preferably the primary antioxidant comprises or consists of a sterically hindered phenol.

Examples of primary antioxidants are disclosed in the below Table 1 .

Table 1

Preferably the primary antioxidant is selected from octadecyl 3-(3’,5’-di-tert. butyl-4- hydroxyphenyl)propionate, 2,2’-thiodiethylenebis-(3,5-di-tert. butyl-4-hydroxyphenyl)- propionate, 2,5,7,8-Tetramethyl-2(4’,8’,12’-trimethyltridecyl)chroman-6-ol or any mixture thereof.

In any embodiments of the invention stabilizers with a better solubility in the n- alkane are preferred. The solubility is determined by a dissolution test.

Preferably the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of: A) optionally adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a n-alkane to the product stream (a), thereby providing a stabilized product stream;

C) optionally adding a solution or a dispersion, such as a suspension (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a n-alkane to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream;

D) subsequent of step C) when present separating at a temperature of from 150 to 300 °C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream, wherein the process comprises at least one of step A) or step C) and wherein preferably the polyolefin comprises or consists of polypropylene. The sterically hindered phenol can be, for example, any of those compounds mentioned above.

Preferably, the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprises a n-alkane, comprises the steps of:

A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a n-alkane to the product stream (a), thereby providing a stabilized product stream;

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the stabilized product stream, wherein preferably the polyolefin comprises or consists of polypropylene.

Step C) and step D) are not carried out. The sterically hindered phenol can be, for example, any of those compounds mentioned above.

Preferably the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of: B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the product stream (a);

C) adding a solution or a dispersion, such as a suspension (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a n-alkane to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream;

D) separating at a temperature of from 150 to 300 °C a second polyolefin- rich stream (c’) from the stabilized polyolefin-rich stream, wherein preferably the polyolefin comprises or consists of polypropylene.

Step A) is not carried out. The sterically hindered phenol can be, for example, any of those compounds mentioned above.

Preferably the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprises a n-alkane, comprises the steps of:

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the stabilized product stream;

C) adding a solution or a dispersion, such as a suspension (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a n-alkane to the first polyolefin-rich stream (c) thereby providing a stabilized polyolefin-rich stream;

Both steps A) and C) are carried out. The sterically hindered phenol can be, for example, any of those compounds mentioned above.

The antioxidant may further comprise a secondary antioxidant. Examples of secondary antioxidant according to the invention are reported in the below Table 2. Table 2

Preferably the secondary antioxidant is selected from tris (2,4-di-f-butylphenyl) phosphite, di-lauryl-thio-di-propionate, di-octadecyl-disulphide or any mixture thereof.

Preferably the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

A) optionally adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and a secondary antioxidant, and preferably a n-alkane to the product stream (a), thereby providing a stabilized product stream;

C) optionally adding a solution or a dispersion, such as a suspension (s2) comprising a primary antioxidant, preferably a sterically hindered phenol and a secondary antioxidant, and preferably a n-alkane to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream;

D) subsequent of step C) when present separating at a temperature of from 150 to 300 °C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream, wherein the process comprises at least one of step A) or step C) and wherein preferably the polyolefin comprises or consists of polypropylene.

Preferably, the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and a secondary antioxidant, and preferably a n-alkane to the product stream (a), thereby providing a stabilized product stream;

Step C) and step D) are not carried out.

C) adding a solution or a dispersion, such as a suspension (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and a secondary antioxidant, and preferably a n-alkane to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream;

Step A) is not carried out. Preferably, the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

Steps A) and C) are both carried out.

Preferably, the solution or dispersion, such as a suspension, (s1 ) of any embodiments of the invention comprises the antioxidant(s) in an amount ranging from 100 ppm to 4000 ppm based on the polyolefin content of product stream (a), more preferably in an amount ranging from 200 to 3000 ppm based on the polyolefin content of product stream (a), more preferably in an amount ranging from 300 to 2500 ppm based on the polyolefin content of product stream (a), more preferably in an amount ranging from 400 to 2000 ppm based on the polyolefin content of product stream (a). Preferably, the solution or dispersion, such as a suspension, (s1 ) of any embodiments of the invention comprises the primary antioxidant in an amount ranging from 100 ppm to 2500 ppm based on the polyolefin content of product stream (a), more preferably in an amount ranging from 200 to 1800 ppm based on the polyolefin content of product stream (a), more preferably in an amount ranging from 300 to 1200 ppm based on the polyolefin content of product stream (a). Preferably, the solution or dispersion, such as a suspension, (s1 ) of any embodiments of the invention comprises the primary antioxidant and the secondary antioxidant in an amount from 100 ppm to 4000 ppm based on the polyolefin content of product stream (a), more preferably in an amount ranging from 200 to 3000 ppm based on the polyolefin content of product stream (a), more preferably in an amount ranging from 300 to 2500 ppm based on the polyolefin content of product stream (a), more preferably in an amount ranging from 400 to 2000 ppm based on the polyolefin content of product stream (a). The solution or dispersion, such as a suspension, (s1 ) of any embodiments of the invention may comprise the secondary antioxidant preferably in an amount ranging from 50 to 1500 ppm based on the polyolefin content of product stream (a).

A lower amount of antioxidants may be required for lower separation step temperature. For example, for separation temperature up to 250° an amount up to 1000 ppm provide protection against thermal degradation. For higher separation temperature a higher amount up to 4000 ppm may be required.

Preferably, the solvent of the solution or dispersion, such as a suspension, (s1 ) of any of the embodiments of the invention comprises or consists of a n-alkane. The n-alkane preferably comprises or consists of a C4, C5, C6, C7, C8, C9, C10, C11 or C12 n-alkane or any mixture thereof, more preferably a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof. Most preferably, the n-alkane comprises or consists of a C6, C7 or C8 n-alkane or any mixture thereof. This means that the n-alkane is selected from n-hexane, n-heptane, n-octane and any mixture thereof. The term “solvent” is used also when referred to a dispersion such as a suspension. In a dispersion, the “solvent” is the dispersion medium (which is generally a solvent) in which the dispersed phase is distributed.

Preferably, the solution or dispersion, such as a suspension, (s2) of any embodiments of the invention comprises the antioxidant(s) in an amount ranging from 100 ppm to 4000 ppm based on the polyolefin content of polyolefin-rich stream (c), more preferably in an amount ranging from 200 to 3000 ppm based on the polyolefin content of polyolefin-rich stream (c), more preferably in an amount ranging from 300 to 2500 ppm based on the polyolefin content of polyolefin-rich stream (c), more preferably in an amount ranging from 400 to 2000 ppm based on the polyolefin content of the polyolefin-rich stream (c) Preferably, the solution or dispersion, such as a suspension, (s2) of any embodiments of the invention comprises the primary antioxidant in an amount ranging from 100 ppm to 2500 ppm based on the polyolefin content of the polyolefin-rich stream (c), more preferably in an amount ranging from 200 to 1800 ppm based on the polyolefin content of the polyolefin-rich stream (c), more preferably in an amount ranging from 300 to 1200 ppm based on the polyolefin content of the polyolefin -rich stream (c). Preferably, the solution or dispersion, such as a suspension, (s2) of any embodiments of the invention comprises the primary antioxidant and the secondary antioxidant. Preferably, the solution or dispersion, such as a suspension, (s2) of any embodiments of the invention comprises the antioxidant(s) in an amount ranging from 100 ppm to 4000 ppm based on the polyolefin content of the polyolefin stream (c), more preferably in an amount ranging from 200 to 3000 ppm based on the polyolefin content of the polyolefin- rich stream (c), more preferably in an amount ranging from 300 to 2500 ppm based on the polyolefin content of the polyolefin-rich stream (c), more preferably in an amount ranging from 400 to 2000 ppm based on the polyolefin content of the polyolefin-rich stream (c). The solution or dispersion, such as a suspension, (s2) of any embodiments of the invention may comprise the secondary antioxidant preferably in an amount ranging from 50 to 1500 ppm based on the polyolefin content of rich stream (c).

Preferably, the solvent of the solution or dispersion, such as a suspension, (s2) of any of the embodiments of the invention comprises or consists of a n-alkane. The n-alkane preferably comprises or consists of a C4, C5, C6, C7, C8, C9, C10, C11 or C12 n-alkane, or any mixture thereof, more preferably a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof. Most preferably, the n-alkane comprises or consists of a C6, C7 or C8 n-alkane or any mixture thereof. This means that the n-alkane is selected from n-hexane, n-heptane, n-octane and any mixture thereof.

A) optionally adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the solution or of the dispersion, such as a suspension, (s1 ) comprises or consists of a n- alkane, preferably a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, most preferably a C6, C7 or C8 n-alkane or any mixture thereof;

C) optionally adding a solution or a dispersion, such as a suspension, (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream, wherein the solvent of the solution or of the dispersion, such as a suspension, (s2) comprises or consists of a n-alkane, preferably a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, most preferably a C6, C7 or C8 n-alkane or any mixture thereof;

A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the solution or of the dispersion, such as a suspension, (s1 ) comprises or consists of a n- alkane, preferably a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, most preferably a C6, C7 or C8 n-alkane or any mixture thereof;

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the stabilized product stream wherein preferably the polyolefin comprises or consists of polypropylene or.

Step C) and step D) are not carried out.

C) adding a solution or a dispersion, such as a suspension, (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream, wherein the solvent of the solution or of the dispersion, such as a suspension, (s2) comprises or consists of a n-alkane, preferably a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, most preferably a C6, C7 or C8 n-alkane or any mixture thereof;

Step A) is not carried out.

D) subsequent of step C) when present separating at a temperature of from 150 to 300 °C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream, wherein preferably the polyolefin comprises or consists of polypropylene.

Steps A) and C) are both carried out.

The solution or dispersion, such as a suspension, (s1 ) and (s2) are prepared according to any method suitable for preparing a solution or dispersion, such as a suspension. Product stream (a)

Product stream (a) is a stream recovered from a solvent-based polyolefin recycling process.

In such a process, waste polyolefin material is dissolved in solvent at elevated temperatures and pressures to remove impurities such as additives, pigments and other unwanted waste material, such as PET, PVC, PA, paper, cardboard, wood, textile, metal(s), glass, sand, etc. originating from the other constituents of the original plastic objects. The solvent is usually introduced by the recycling process.

Preferably, in any of the embodiments of the invention, the solvent of the product stream (a) before the addition of the solution or dispersion, such as a suspension, (s1 ) is an organic solvent. More preferably, the solvent comprises or consists of an alkane, such as one or more cycloalkanes and/or one or more n-alkanes. Examples of suitable cycloalkanes are cyclopropane, cyclobutane, cyclopentane and cyclohexane or any mixture thereof. The solvent of the product stream (a) preferably comprises or consists of one or more n-alkanes. The solvent preferably comprises or consists of a n-alkane selected from a C4, C5, C6, C7, C8, C9, C10, C1 1 , C12 n-alkane and any mixture thereof, more preferably the solvent comprises or consists of a n-alkane selected from a C6, C7, C8, C9, C10 n-alkane and any mixture thereof. Most preferably, the solvent comprises or consists of a n-alkane selected from a C6, C7 and C8 n-alkane and any mixture thereof. This means that the n-alkane is selected from n-hexane, n-heptane, n- octane and any mixture thereof.

Preferably, the solution or dispersion (s1 ), comprises a solvent which is the same solvent as of the product stream (a).

Preferably, in any of the embodiments of the invention, the solvent of the product stream (a) before the addition of the solution or dispersion, such as a suspension (s1 ), the solvent of the solution or dispersion, such as a suspension (s1 ), and the solvent of the solution or dispersion, such as a suspension, (s2) is the same solvent, preferably the solvent comprises or consists of a n-alkane selected from C4, C5, C6, C7, C8, C9, C10, C1 1 , C12 n-alkane and any mixture thereof, more preferably the solvent comprises or consist of a n-alkane selected from a C6, C7, C8, C9, C10 n-alkane and any mixture thereof, most preferably the solvent comprises or consists of a n-alkane selected from a C6, C7,C8 n-alkane and any mixture thereof. This means that the n-alkane is selected from n-hexane, n- heptane, n-octane and any mixture thereof.

The polyolefin stream (a) may comprise volatile compounds other than the solvent(s) (wherein the solvent(s) include the n-alkane) Polyolefin-rich stream (c)

The polyolefin-rich stream (c) is recovered from the separation step B) of the product stream (a) or of the stabilized product stream. It is therefore richer in the polyolefin and leaner in the volatiles, including the solvent of the product stream (a) and of the solution or dispersion, such as a suspension (s1 ) (the latter provided that step A) is carried out to provide the stabilized product stream).

Therefore, the composition in terms of type of solvents of polyolefin-rich stream (c) depends on product stream (a) and on the solution or dispersion, such as a suspension (s1 ) (the latter provided that step A) is carried out to provide the stabilized product stream).

Preferably, in any of the embodiments of the invention, the solvent of the polyolefin-rich stream (c) before the addition of the solution or dispersion, such as a suspension, (s2) and the solvent of the solution or dispersion, such as a suspension (s2) is the same solvent, wherein the solvent of the solution or dispersion, such as a suspension, (s2) is as defined above.

Advantageously, it has been seen that the antioxidants, preferably the sterically hindered phenol, suitably dissolve in n-alkane and can homogenously be added to product stream (a) and to the polyolefin-rich stream (c).

A) optionally adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the product stream (a) before the addition of the solution or the dispersion, such as a suspension, (s1 ) and of the solution or of the dispersion, such as a suspension, (s1 ) comprise or consist of a n-alkane, preferably the same n-alkane;

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the product stream (a) or, when step A) is carried out, from the stabilized product stream

C) optionally adding a solution or a dispersion, such as a suspension, (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the first polyolefin-rich stream (c), thereby providing a stabilized product stream, wherein the solvent of the solution or of the dispersion, such as a suspension, (s2) comprises or consists of a n-alkane, preferably the same n-alkane of product stream (a) and of the solution or dispersion, such as a suspension (s1 );

A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably, a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the product stream (a) before the addition of the solution or the dispersion, such as a suspension, (s1 ) and the solvent of the solution or the dispersion, such as a suspension, (s1 ) comprises or consists of a n-alkane, preferably the same n-alkane;

Step C) and step D) are not carried out.

Preferably the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of::

C) adding a solution or a dispersion, such as a suspension (s2), comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream, wherein the solvent of the solution or of the dispersion, such as a suspension, (s2) comprises or consists of a n-alkane;

D) separating at a temperature of from 150 to 300 °C a second polyolefin- rich stream (c’) from the stabilized polyolefin-rich stream, wherein the solvent of the product stream (a) comprises or consists of a n-alkane, preferably the same n-alkane of the solution or of the dispersion, such as a suspension, (s2) and wherein preferably the polyolefin comprises or consists of polypropylene.

Step A) is not carried out.

A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the product stream (a) before the addition of the solution or dispersion, such as a suspension, (s1 ) and the solvent of the solution or of the dispersion, such as a suspension, (s1 ) comprise or consist of a n-alkane, preferably the same n-alkane;

C) adding a solution or a dispersion, such as a suspension (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream, wherein the solvent of the solution or dispersion, such as a suspension, (s2) is a n-alkane, preferably the same n-alkane of product stream (a) and of the solution or of the dispersion, such as a suspension (s1 );

Both steps A) and C) are carried out. More preferably the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

A) optionally adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a) thereby providing a stabilized product stream, wherein the solvent of the product stream (a) before the addition of the solution or the dispersion, such as a suspension, (s1 ) and the solvent of the solution or of the dispersion, such as a suspension, (s1 ) comprise or consist of a C6, C7, C8, C9 orC10 n- alkane or any mixture thereof, preferably the same C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, preferably, the solvent of the product stream (a) before the addition of the solution or the dispersion, such as a suspension, (s1 ) and the solvent of the solution or of the dispersion, such as a suspension, (s1 ) comprise or consist of a C6, C7 or C8 n-alkane or any mixture thereof, preferably the same C6, C7 or C8 n-alkane or any mixture thereof;

C) optionally adding a solution or a dispersion, such as a suspension, (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream, wherein the solvent of the solution or of the dispersion, such as a suspension, (s2) comprises or consists of a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, preferably the same C6, C7, C8, C9 orC10 n-alkane or any mixture thereof of product stream (a) and of the solution or dispersion, such as a suspension (s1 ), preferably the solvent of the solution or of the dispersion, such as a suspension, (s2) comprises or consists of a C6, C7 or C8 n- alkane or any mixture thereof, preferably the same C6, C7 or C8 n-alkane or any mixture thereof of product stream (a) and of the solution or dispersion, such as a suspension (s1 );

D) subsequent of step C) when present separating at a temperature of from 150 to 300 °C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream wherein the process comprises at least one of step A) or step C) and wherein preferably the polyolefin comprises or consists of polypropylene.

More preferably, the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the product stream (a) before the addition of the solution or the dispersion, such as a suspension, (s1 ) and the solvent of the solution or the dispersion, such as a suspension, (s1 ) comprise or consist of a C6, C7, C8, C9 or C10 n- alkane or any mixture thereof, and are preferably the same C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, preferably wherein the solvent of the product stream (a) before the addition of the solution or the dispersion, such as a suspension, (s1 ) and the solvent of the solution or the dispersion, such as a suspension, (s1 ) comprise or consist of a C6, C7 or C8 n-alkane or any mixture thereof, and are preferably the same C6, C7 or C8 n-alkane or any mixture thereof;

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the stabilized product stream, wherein preferably the polyolefin comprises or consists of polypropylene or .

Step C) and step D) are not carried out.

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the product stream (a)

C) adding a solution or a dispersion, such as a suspension, (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream, wherein the solvent of the solution or of the dispersion, such as a suspension, (s2) comprises or consists of a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, preferably a C6, C7 or C8 n-alkane or any mixture thereof;

D) subsequent of step C) when present separating at a temperature of from 150 to 300 °C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream wherein the solvent of the product stream (a) comprises or consists of a C6, C7, C8, C9 or C10 n-alkane or any mixture, preferably a C6, C7 or C8 n-alkane or any mixture thereof and is preferably the same n-alkane of the solution or dispersion, such as a suspension (s2); and wherein preferably the polyolefin comprises or consists of polypropylene.

Step A) is not carried out.

More preferably the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the product stream (a) before the addition of the solution or dispersion, such as a suspension, (s1 ) and the solvent of the solution or of the dispersion, such as a suspension, (s1 ) comprise or consist of a C6, C7, C8, C9 or C10 n- alkane or any mixture thereof and are preferably the same C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, preferably wherein the solvent of the product stream (a) before the addition of the solution or dispersion, such as a suspension, (s1 ) and the solvent of the solution or of the dispersion, such as a suspension, (s1 ) comprise or consist of a C6, C7 or C8 n-alkane or any mixture thereof and are preferably the same C6, C7 or C8 n-alkane or any mixture thereof;

C) adding a solution or a dispersion, such as a suspension, (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream, wherein the solvent of the solution or dispersion, such as a suspension, (s2) is a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof and is preferably the same C6, C7, C8, C9 or C10 n-alkane or any mixture thereof of product stream (a) and of the solution or dispersion, such as a suspension (s1 ), preferably wherein the solvent of the solution or dispersion, such as a suspension, (s2) is a C6, C7 or C8 n-alkane or any mixture thereof and is preferably the same C6, C7 or C8 n-alkane or any mixture thereof of product stream (a) and of the solution or dispersion, such as a suspension (s1 );

Both steps A) and C) are carried out.

In one embodiment, the process comprises, before step A) or step B) (when step A) is not carried out) the step of

A⁰) carrying out purification, preferably by a settling and/or filtration and/or adsorption, from impurities on a polymer solution stream (a⁰) to provide the product stream (a).

Step A⁰) is a step of the recycling process aimed to remove any impurities present from the polymer solution stream (a⁰) comprising the recycled polyolefin. Particular examples of the impurities comprised in the plastic feedstock are additives. The additives used in plastics are organic or inorganic compounds, such as fillers, colorants, pigments, plasticizers, property modifiers, combustion retardants, etc. In this step, in addition to undesired impurities also useful additives potentially present may be removed. For example, antioxidants may be removed. The resulting product stream a) therefore does not comprise antioxidants or comprises them in an insufficient amount to achieve an antioxidant effect. The addition of an antioxidant to the resulting product stream (a) and/or stream (c), thereby aims to protect the recycled polyolefin e.g. from decomposition such as thermal decomposition.

According to the invention, it is therefore contemplated that the product stream (a) does not comprise an antioxidant or it comprises an antioxidant in an amount lower than 100 ppm based on the weight of the polyolefin.

The product stream (a) may essentially lack substantial amounts of undissolved material. Preferably, the product stream (a) may comprise less than 1 wt%, such as less than 0.5 wt%, of undissolved material based on the weight of the product stream (a). Therefore, preferably the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

A⁰) carrying out a purification, preferably, by a settling and/or filtration and/or adsorption, from impurities on a polymer solution stream (a⁰) to provide the product stream (a);

A) optionally adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the product stream (a) before the addition of the solution or the dispersion, such as a suspension, (s1 ) and the solvent of the solution or the dispersion, such as a suspension, (s1 ) comprises or consists of a n-alkane, preferably the same n-alkane;

C) optionally adding a solution or a dispersion, such as a suspension, (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream, wherein the solvent of the solution or the dispersion, such as a suspension, (s2) comprises or consists of a n-alkane, preferably the same n-alkane of product stream (a) and of the solution or dispersion, such as a suspension (s1 );

D) subsequent of step C) when present separating at a temperature of from 150 to 300 °C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream), wherein the process comprises at least one of step A) or step C) and wherein preferably the polyolefin comprises or consists of polypropylene.

Preferably the process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of: A⁰) carrying out a purification, preferably, by settling and/or filtration and/or adsorption, from impurities on a polymer solution stream (a⁰) to provide the product stream (a);

A) adding a solution or a dispersion, such as a suspension (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the product stream (a) before the addition of the solution or the dispersion, such as a suspension, (s1 ) and the solvent of the solution or the dispersion, such as a suspension, (s1 ) comprises or consists of a n-alkane, preferably the same n-alkane;

Step C) and step D) are not carried out.

A⁰) carrying out a purification, preferably by settling and/or filtration and/or adsorption, from impurities on a polymer solution stream (a⁰) to provide the product stream (a);

C) adding a solution or a dispersion, such as a suspension, (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream, wherein the solvent of the solution or the dispersion, such as a suspension, (s2) comprises or consists of a n-alkane;

D) separating at a temperature of from 150 to 300 °C a second polyolefin- rich stream (c’) from the stabilized polyolefin-rich stream, wherein the solvent of the product stream (a) comprises or consists of a n-alkane, preferably the same n-alkane of the solution or dispersion, such as a suspension, (s2) and wherein preferably the polyolefin comprises or consists of polypropylene. Step A) is not carried out.

Preferably, the process for the separation of at least one polyolefin from a product stream (a) originating from solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the product stream (a) before the addition of the solution or dispersion, such as a suspension, (s1 ) and the solvent of the solution or dispersion, such as a suspension, (s1 ) comprises or consists of a n-alkane, preferably the same n-alkane;

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the stabilized product stream,

C) adding a solution or a dispersion, such as a suspension, (s2) comprising a primary antioxidant, preferably a sterically hindered phenol, and preferably a secondary antioxidant to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream, wherein the solvent of the solution or dispersion, such as a suspension, (s2) is a n- alkane, preferably the same n-alkane of product stream (a) and solution or dispersion, such as a suspension (s2);

Both steps A) and C) are carried out.

More preferably, the process for the separation of polypropylene from a product stream (a) originating from a solvent based polypropylene recycling process, wherein the product stream (a) comprises polypropylene dissolved in a solvent preferably comprising a n-alkane, comprises the steps of:

A⁰) carrying out a purification, preferably by settling and/or filtration and/or adsorption, from impurities on a polypropylene solution stream (a⁰) to provide the product stream (a); A) optionally adding a solution or a dispersion, such as a suspension, (s1 ) comprising a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the solution or of the dispersion, such as a suspension, (s1 ) comprises or consists of a n-alkane;

B) separating at a temperature of from 150 to 300 °C a first polypropylene- rich stream (c) from the product stream (a) or, when step A) is carried out, from the stabilized product stream;

C) optionally adding a solution or a dispersion, such as a suspension, (s2) comprising a sterically hindered phenol, and optionally a secondary to the first polypropylene-rich stream (c), thereby providing a stabilized polypropylene-rich stream, wherein the solvent of the solution or the dispersion, such as a suspension, (s2) comprises or consists of a n- alkane;

D) subsequent of step C) when present separating at a temperature of from 150 to 300 °C a second polypropylene-rich stream (c’) from the stabilized polypropylene-rich stream); wherein the process comprises at least one of step A) or step C) and wherein the n-alkane comprises or consists of a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, preferably a C6, C7 or C8 n-alkane or any mixture thereof, and wherein preferably the n-alkane of the solutions or dispersions, such as a suspensions, (s1 ) and (s2) is the same n-alkane of product stream (a).

A⁰) carrying out a purification, preferably, by settling and/or filtration and/or adsorption, from impurities on a polypropylene solution stream (a⁰) to provide the product stream (a);

A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the solution or the dispersion, such as a suspension, (s1 ) comprises or consists of a n-alkane;

B) separating at a temperature of from 150 to 300 °C a first polypropylene- rich stream (c) from the stabilized product stream, wherein the n-alkane comprises or consists of a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, preferably a C6, C7 or C8 n-alkane or any mixture thereof, and wherein preferably the n-alkane of the solution or dispersion, such as a suspension, (s1 ) is the same n-alkane of product stream (a).

Steps C) and D are not carried out.

A⁰) carrying out a purification, preferably by settling and/or filtration and/or adsorption from impurities on a polypropylene solution stream (a⁰) to provide the product stream (a);

B) separating at a temperature of from 150 to 300 °C a first polypropylene- rich stream (c) from the product stream (a);

C) adding a solution or a dispersion, such as a suspension, (s2) comprising a sterically hindered phenol, and preferably a secondary antioxidant to the polypropylene-rich stream (c) thereby providing a stabilized polypropylene-rich stream, wherein the solvent of the solution or the dispersion, such as a suspension, (s2) comprises or consists of a n-alkane;

D) separating at a temperature of from 150 to 300 °C a second polypropylene -rich stream (c’) from the stabilized polyolefin-rich stream, wherein the n-alkane comprises or consists of a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, preferably a C6, C7 or C8 n-alkane or any mixture thereof, and wherein preferably the n-alkane of the solution or dispersion, such as a suspension, (s2) is the same n-alkane of product stream (a)

Step A) is not carried out.

A⁰) carrying out a purification, preferably by settling and/or filtration and/or adsorption, from impurities on a polypropylene solution stream (a⁰) to provide the product stream (a); A) adding a solution or a dispersion, such as a suspension, (s1 ) comprising a sterically hindered phenol, and preferably a secondary antioxidant to the product stream (a), thereby providing a stabilized product stream, wherein the solvent of the solution or dispersion, such as a suspension, (s1 ) comprises or consists of a n-alkane;

C) adding a solution or a dispersion, such as a suspension, (s2) comprising sterically hindered phenol, and preferably a secondary antioxidant to the polypropylene-rich stream (c), thereby providing a stabilized polypropylene-rich stream, wherein the solvent of the solution or dispersion, such as a suspension, (s2) is a n-alkane;

D) separating at a temperature of from 150 to 300 °C a second polyolefin- rich stream (c’) from the stabilized polypropylene-rich stream), wherein the n-alkane comprises or consists of a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof, preferably a C6, C7 or C8 n-alkane or any mixture thereof, and wherein preferably the n-alkane of the solutions or dispersions, such as suspensions, (s1 ) and (s2) is the same n-alkane of product stream (a).

Methods to carry out purification e.g. by settling, filtration and adsorption of impurities in a solvent based recycling process are, for example, described in EP 3 339 361 (A1). .

Step A)

In step A) a solution or a dispersion, such as a suspension, (s1 ) as disclosed above is added to the product stream (a). Any method to add the solution or dispersion, such as a suspension, (s1 ) to the product stream (a) is suitable. For example, the solution or dispersion, such as a suspension, may be added by injection, such as via positive displacement devices like pumps or simply by using a pressure difference (e.g. using higher gas pressure on any dosing vessel).

Following the addition of the solution or the dispersion, such as a suspension, (s1 ), step A) may optionally comprise a mixing step that may help obtaining a homogenous dispersion/solution of the antioxidant in the product stream a). Advantageously, the mixing requires a lower amount of energy vis a vis e.g. the addition of antioxidants as solids due to the good miscibility of n-alkane with the polyolefin and the polyolefin solution. Mixing may, for example, be performed via the use of static mixers or dynamic mixers.

Step A) provides a stabilized product stream. Step B)

Step B) can be carried out, for example, as a vapor-liquid separation step or as a liquid-liquid separation step. Preferably, step B) is carried out as a vapor-liquid separation step, more preferably as a flash separation step. Preferably, the product stream (a) is separated in a first polyolefin-rich stream (c) and a first polyolefin-lean stream (b), wherein the polyolefin first lean stream (b) is rich in the solvent. The polyolefin-lean stream (b) is preferably returned to the polymer recycling process upon adjusting pressure and temperature to the requirements of the recycling process. Most preferably, the first polyolefin-lean stream (b) is returned to the recycling process without any further purification.

If step B) is a vapor-liquid separation step, more preferably as a flash separation step, it is preferably carried out at a temperature of 150 to 300 C, preferably 175 to 275 °C, and most preferably 200 to 250 °C. Moreover, in such case, step B) is preferably carried out at a pressure of 1 to 15 bar, more preferably 2 to 12 bar, and most preferably 2.5 to 10 bar. Most preferably, in such case, step B) is carried out at a temperature of 200 to 250 °C and at a pressure of 2.5 to 10 bar.

If step B) is carried out as a liquid-liquid separation step, the separation temperature is preferably 100 to 400°C, more preferably 1 10 to 380 °C and most preferably 120 to 370°C. Moreover, in such case, step B) is preferably carried out at a pressure of 10 to 70 barg, more preferably a 15 to 65 barg, and most preferably at 20 to 60 barg. Most preferably, in such case, step Bl) is preferably carried out at a temperature of 120 to 370 °C and at a pressure of 20 to 60 barg.

Step C)

In step C) a solution or a dispersion, such as a suspension, (s2) as disclosed above is added to the first polyolefin-rich stream (c) thereby a stabilized polyolefin- rich stream is provided.

Any method to add the solution or dispersion, such as a suspension, (s2) to the first polyolefin stream (c) is suitable. For example, the solution or dispersion, such as a suspension, may be added by injection, such as via positive displacement devices like pumps or simply by using a pressure difference (e.g. using higher gas pressure on any dosing vessel).

Following the addition of the solution or the dispersion, such as a suspension, (s2), step C) may optionally comprise a mixing step that may help obtaining a homogenous dispersion/solution of the antioxidant in the polyolefin-rich stream a). Advantageously, the mixing requires a lower amount of energy vis a vis e.g. the addition of antioxidants as solids due to the good miscibility of n-alkane with the polyolefin and the polyolefin solution. Mixing may, for example, be performed via the use of static mixers or dynamic mixers.

Step D)

Step D) is carried out following step C) on the stabilized polyolefin-rich stream produced in step C). Step D) can be carried out, for example, as a vapor-liquid separation step or as a liquid-liquid separation step. Preferably, step D) is carried out as a vapor-liquid separation step, most preferably as a flash separation step. Preferably, the stabilized polyolefin-rich stream is separated into a second polyolefin-rich stream (c’) and second polyolefin-lean vapor stream (b’), wherein second polyolefin-lean vapor stream (b’) is rich in the solvent. The second polyolefin-lean vapor stream (b’) is preferably returned to the polymer recycling process upon adjusting pressure and temperature to the requirements of the recycling process. Most preferably, the second polyolefin-lean vapor stream (b’) is returned to the recycling process without any further purification.

Preferably, step D) is carried out as a flash separation step. In such case, preferably, step D) is carried out at a temperature of 150 to 300 °C, more preferably 175 to 275 °C, and most preferably 200 to 250 °C. Moreover, in such case, step D) is preferably carried out at a pressure of 1 to 15 bar, more preferably 2 to 12 bar, and most preferably 2.5 to 10 bar. If flash separation steps are carried out several times in a row, the pressure is lowered step after step and the temperature of the polyolefin is usually increased step after step. Thus, the pressure in step D) has to be lower than in step B), if step B) is carried out as a flash separation step. Furthermore, the temperature in step D) has to be higher than in step B), if step B) is carried out as a flash separation step. Most preferably, in such case, step D) is carried out at a temperature of 200 to 250 °C and at a pressure of 2.5 to 10 barg.

Step E)

The process according to the invention as described above may further comprises the step of

E) separating a third polyolefin-rich stream (c”) from the second polyolefin- rich stream (c’).

Step E comprises separating a condensed polyolefin-rich stream (c”) from the second polyolefin-rich stream (c’). Preferably, the second polyolefin-rich stream (c’) is separated in a third polyolefin-rich stream (c”) and a third polyolefin-lean stream (b”) wherein the third polyolefin lean stream (b”) is rich in the solvent. The third polyolefin-lean stream (b”) is preferably returned to the polymer recycling process upon adjusting pressure and temperature to the requirements of the recycling process. Most preferably, the third polyolefin-lean stream (b”) is returned to the recycling process without any further purification.

In a preferred embodiment of the invention step E) is a flash separation step preferably with preceding addition of a stripping agent into the second polyolefin- rich stream (c’) or an extruding/degassing step.

If step E) is a flash separation step, a stripping agent is preferably added to the second polyolefin-rich stream (c’) before being fed to the flash separator. More preferably, the stripping agent is fed in an amount of 2 to 4 wt.-% with respect to the total weight of the second polyolefin-rich stream (c’). Preferably, the stripping agent is added as a solution or a dispersion, such as a suspension, (s3) comprising said stripping agent. Preferably, the solvent of the solution or dispersion, such as a suspension, (s3) comprising the stripping agent is a n- alkane. The solvent preferably comprises, or consists of a C4, C5, C6, C7, C8, C9, C10, C11 , C12 n-alkane, or any mixture thereof, preferably the solvent comprises or consists of a C6, C7, C8, C9 or C10 n-alkane or any mixture thereof. Most preferably, the solvent comprises or consists of a C6, C7 or C8 n-alkane or any mixture thereof. This means that the n-alkane is selected from n-hexane, n- heptane, n-octane and any mixture thereof. The solution or dispersion, such as a suspension, (s3) may comprise antioxidant as disclosed above.

The flash separation steps are carried out several times in a row, the pressure is lowered step after step and the temperature is usually increased step after step. Thus, in this case the pressure in step E) has to be lower than in step D), if step E) is carried out as a flash separation step. Furthermore, the temperature in step E) has to be higher than in step D), if step D) is carried out as a flash separation step. Preferably, in case step E) is a flash separation step, step E) is carried out at a temperature of 150 to 300 °C, preferably 175 to 275 °C, and most preferably 200 to 250 °C. Moreover, in such case, step E) is preferably carried out at vacuum pressure conditions. Hence, most preferably, in case step E) is a flash separation step, the stripping agent is fed in an amount of 2 to 4 wt.-% with respect to the total weight of the second polyolefin-rich stream (c’) before the second polyolefin-rich stream (c’) enters the flash separator, and step E) is carried out at a temperature of 200 to 250 °C and at vacuum pressure conditions. Preferably, the stripping agent is fed a solution or dispersion, such as a suspension, (s3) as disclosed above. The third polyolefin-lean vapor stream (b”) may be purified in a recovery section and subsequently returned to the initial feed stream (a’).

If step C) is an extruding/degassing step, the second polyolefin-rich stream (c’) is preferably fed to a devolatilisation extruder. Preferably, the extruder has a backward degassing at a pressure in the range of 0.5 bar above atmospheric pressure to 0.5 bar below atmospheric pressure, preferably at atmospheric pressure, whereby atmospheric pressure denotes the natural atmospheric pressure of the earth’s atmosphere varying at about 1 atm, and forward degassing domes at vacuum conditions.

The stripping agent is preferably selected from the list consisting of carbon dioxide, nitrogen, and water. Most preferably, the stripping agent is water.

In a preferred embodiment of the invention, in step B) 55 to 90 wt.-%, preferably 60 to 70 wt.-%, based on the weight of the product stream (a), of the volatiles (including the solvent(s)) are removed from the product stream (a). Likewise, in a preferred embodiment of the invention, in step D) 10 to 40 wt.-%, preferably 25 to 30 wt.-%, based on the weight of the first polyolefin-rich stream (c), of the volatiles (including the solvent(s)) are removed from the first polyolefin-rich stream (c). Moreover, in a preferred embodiment of the invention, in step E) up to 5 wt.-%, preferably 0.2 to 5 wt.-%, based on the weight of the polyolefin-rich stream (c’), of the volatile (including the solvent(s)) are removed from the second polyolefin-rich stream (c‘). Hence, mostly preferred, in step B) 60 to 70 wt.-%, based on the weight of the polyolefin-rich stream (a), of the volatiles (including the solvent(s)) are removed from the product stream (a), in step D) 25 to 30 wt.-% of volatiles (including the solvent(s)) are removed from the first polyolefin-rich stream (c), and in step E) 0.2 to 5 wt.-%, based on the weight of the condensed polyolefin-rich stream (c’), of volatiles (including the solvent(s)) are removed from the condensed polyolefin-rich stream (c‘)

An aspect of the invention is directed to a polyolefin obtainable by process for the separation of at least one polyolefin from a product stream (a) originating from a polyolefin recycling process, particularly a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin and a solvent as disclosed above. The obtained olefin preferably comprises less than 500 ppm volatiles, preferably less than 200 ppm volatiles, most preferably equal to or less than 150 ppm.

Step E) is carried out after step D). When steps C) and D) are not carried out step E is carried out after step B). In this case the first polyolefin-rich stream (c) is separated in a second* polyolefin-rich stream (c*) and a second* polyolefin lean stream (b*).

Test methods

Volatile content & n-alkane content The volatile content of the polyolefin is determined by using static head space analysis similar to VDA 277:1995 using a gas chromatograph equipped with a flame ionization detector. Headspace extraction is performed on pellets (about 2 g in 20 ml headspace vial) using 120 °C (PP) and 100 °C (PE) incubation for 5 hours prior to the GC measurement. The gas chromatographic separation is performed with a WCOT- capillary column (wax type) or a PLOT column, respectively. The total emission is measured on the basis of the sum of all values provided by the emitted substances after gas chromatography analysis and flame ionization detection with acetone as the calibration standard. The total emission value is reported in the unit of microgram carbon per gram of sample and refers to the carbon content in the acetone standard.

The amount of the added C4, C5, C6, C7 or C8 n-alkane is also determined similar to VDA 277:1995 but using the single component approach. Therefore, the emission is determined on the basis of the corresponding n-alkane calibration. In case a calibration standard is not available, the semi-quantitation of the individual n-alkane is done by using the response factor of n-hexane.

Antioxidant content

Antioxidant (chemicals like Irganox® 1010 and Irgfos® 168, i.e., Pentaerythrityl- tetrakis(3-(3’,5’-di-tert. butyl-4-hydroxyphenyl)-propionate) and Tris (2,4-di-t- butylphenyl) phosphite) content was determined via high performance liquid chromatography (HPLC) after extraction with ethyl acetate. Therefore, about 10 g of the sample were cryo-milled with the aid of liquid nitrogen. 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 filtered 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.

Molecular weight

Molecular weight averages (Mz, Mw and Mn), Molecular weight distribution (MWD) and its broadness, described by polydispersity index, PDI= Mw/Mn (wherein Mn is the number average molecular weight and Mw is the weight average molecular weight) were determined by Gel Permeation Chromatography (GPC) according to ASTM D 6474-12 using the following formulas:

_w ~ _VN _A (Z)

For a constant elution volume interval AV, where A, and Mi are the chromatographic peak slice area and polyolefin molecular weight (MW), respectively associated with the elution volume, Vi, where N is equal to the number of data points obtained from the chromatogram between the integration limits.

A high temperature GPC instrument, equipped with an IR5 from PolymerChar (Valencia, Spain) and with 3 x Agilent-PLgel Olexis and 1x Agilent-PLgel Olexis Guard columns was used. As solvent and mobile phase 1 ,2,4-trichlorobenzene (TCB) stabilized with 250 mg/L 2,6-Di tert butyl-4-methyl-phenol) was used. The chromatographic system was operated at 160 °C and at a constant flow rate of 1 mL/min. 200 pL of sample solution was injected per analysis. Data collection was performed using PolymerChar GPC-IR control software.

The column set was calibrated using universal calibration with 19 narrow MWD polystyrene (PS) standards in the range of 0,5 kg/mol to 11 500 kg/mol. The PS standards were dissolved at 160°C for 30 min. The conversion of the polystyrene peak molecular weight to polypropylene molecular weights is accomplished by using the Mark Houwink equation and the following Mark Houwink constants:

KPS = 19 x 10’³ mL/g, aps = 0.655

KPP = 19 x 10’³ mL/g, a_PP = 0.725

A third order polynomial fit was used to fit the calibration data.

All samples were prepared in the concentration range of 0,5 -1 mg/ml and dissolved at 160 °C for 2.5 hours for PP or 3 hours for PE under continuous gentle shaking.

Melt Flow Rate

The melt flow rate (MFR) was determined according to ISO 1133 and is indicated in g/10 min. The MFR is an indication of the flowability and hence the processability of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer. Here, the MFR2 was determined at a temperature of 230 °C and under a load of 2.16 kg.

Crystex analysis

The crystalline (CF) and soluble fractions (SF) of the PCR polypropylene resins as well as the ethylene contents and intrinsic viscosities of the respective fractions were analyzed by use of the CRYSTEX instrument, Polymer Char (Valencia, Spain) in line with ISO 6427 Annex B. Details of the technique and the method can be found in literature (Ljiljana Jeremie, Andreas Albrecht, Martina Sandholzer & Markus Gahleitner (2020) 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, 25:8, 581 -596).

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 ¹³C-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:

Cone = a + b*Abs(CH) + c*(Abs(CH))² + d*Abs(CH₃) + e*(Abs(CH₃)² + f*Abs(CH)*Abs(CH₃) (equation 1 )

CH3/1000C = a + b*Abs(CH) + c* Abs(CH₃) + d * (Abs(CH₃)/Abs(CH)) + e * (Abs(CH₃)/Abs(CH))² (equation 2)

The constants a to e for equation 1 and a to f for equation 2 were determined by using least square regression analysis.

The CH₃/1000C is converted to the ethylene content in wt.-% using following relationship: wt.-% (ethylene in EP copolymers) = 100 - CH₃/1000TC * 0.3

Intrinsic viscosity (IV) of the PCR polypropylene resin and its soluble and crystalline fractions are determined with a use of an online 2-capillary viscometer and are correlated to corresponding IV’s determined by standard method in decalin according to ISO 1628-3. Calibration is achieved with various EP PP copolymers with IV = 2-4 dL/g. The determined calibration curve is linear: IV (dL/g) = a* Vsp/c

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.

After automated filling of the vial with 1 ,2,4-TCB containing 250 mg/l 2,6-tert-butyl-4- methylphenol (BHT) as antioxidant, the sample is dissolved at 170 °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.

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. During the second injection the soluble fraction (at low temperature) and the crystalline fraction (at high temperature) with the crystallization cycle are measured (wt.-% SF, wt.-% CF, wt.-% C2, wt.-% C2(SF), wt.-% C2(CF), IV(SF), IV(CF)), where the wt.-% CF is calculated in the following way: wt.-% CF = 100 - wt.-% SF.

Examples

Solvent based recycling (SbR) process

When reference hereinafter is made in the Examples to a solvent based recycling process, the following process was used.

A pre-purified feedstock obtained from plastic waste and comprising 95% by weight polypropylene (PP) was introduced in flake form into an extruder which was heated to 200°C. At the outlet of the extruder, the feedstock was at least partly in melt form and was mixed with n-heptane pre-heated at 200°C with a weight ratio of solvent : feedstock of 4: 1 .

The mixture comprising the solvent and the feedstock was introduced into a stirred reactor which is heated to 200°C and was maintained at 2.0 MPa absolute for a residence time of 1 hour. A polymer solution is thus obtained.

The polymer solution was continuously drawn off from the stirred reactor and introduced in a static settler. The settling was operated at 200°C and 2.0 MPa.

A cleared polymer solution was continuously drawn off from the settler and passed through two filters in series, maintained at 200°C and having cut diameter equal to 10 pm and 1 pm, respectively (in this order). At the outlet of the filter’s series, the pre-purified polymer solution was then passed through an adsorption section comprising an adsorbent bed comprising activated carbon or bleaching earth. This adsorption step was carried out at 200°C and 2.0 MPa with an adsorbent to polymer ratio as further specified below and for an adsorption time as further specified below.

The purified solution at the outlet of the adsorption section was then submitted to solvent-polymer separation by vaporizing n-heptane to obtain a post-consumer recycled polypropylene resin.

Reference Examples 1 and 2 (RE1 to RE2)

Two samples, each containing about 95 wt% polypropylene (PP), in form of flakes, obtained from PP post-consumer feedstock were used. Characteristics of these two PP based samples, RE1 and RE2, after mechanical sorting and washing, but prior to the SbR process, are summarized in below Table 1 .

Table 1

The PP flakes were introduced into an extruder which was heated to 200°C. During the extrusion step at 1500 ppm, the antioxidants Irgafos 168 and 1500 ppm Irganox 1010 were added in the form of flakes.

The active antioxidant content of the PP flakes prior to the above described extrusion step (including addition of extra antioxidant) as well as the active antioxidant content of the resulting PP pellets after the above described extrusion step were determined via HPLC.

The resulting PP pellets (with the extra antioxidants added) were treated in the above described solvent based recycling (SbR) process and the active antioxidant content of the recyclate obtained after the SbR process were determined via HPLC. Table 2

‘activated carbon (AC) as adsorbant in the SbR process

“bleaching earth (BE) as adsorbant in the SbR process

LOQ = limit of quantification

ND = not determined

When treating RE1 sample in the SbR process, an adsorbent (activated carbon) amount of 3.2 wt% based on weight of the polymer and an adsorption time of 25 min were used.

A first sample of RE2 (RE2-1 ) was treated in the SbR process using an adsorbent (bleaching earth) amount of 4.7 w% based on weight of the polymer and an adsorption time of 14 min were used. A weight ratio of solventfeedstock of 9:1 was used in this trial.

A second sample of RE2 (RE2-2) was treated in the SbR process using an adsorbent (bleaching earth) amount of 21.1 w% based on weight of the polymer and an adsorption time of 43 min were used.

A significant reduction of more than 60 % of the active antioxidant content is obtained by the SbR process, meaning that even when adding extra antioxidant prior the SbR process the majority of the added amount is lost during the process. When using a highly effective adsorbant, such as bleaching earth, which may be needed to remove polar organic substances, the content of the active antioxidant after adsorption is very low or below the limit of quantification, even when adding a high amount of antioxidant prior the SbR process.

Example 1 : Effect of antioxidants at temperature of 270°C

The thermal stability of polypropylene in samples containing various antioxidant contents were evaluated.

The amount of the active antioxidants as well as the weight average molar mass before the thermal treatment are summarized in Table 3.

Table 3: Compositions of CE1 , IE1 , IE2 and IE3

Comparative sample 1 (CE1 ):

A sample comprising polypropylene as a reactor powder was provided.

Sample 1 (IE1 ):

A sample of RE1 pellets (with extra AO addition) prepared as described above for Reference Example 1 (i.e. prior to solvent based recycling process).

Sample 2 (IE2):

A sample of PP pellets (with extra AO addition) prepared in the same manner as described for Reference Examples 1 -2 but using a PP reactor powder (instead of PP from a post-consumer feedstock) and 250 ppm Irganox 1010, 600 ppm Irgafos 168 and 2000 ppm Erucamide added during the extrusion (instead 1500 ppm Irgafos 168 and 1500 ppm Irganox 1010). Erucamide is a slipping agent derived from the condensation of erucic acid and ammonia.

Sample 3 (IE3): A sample of RE1 pellets (with extra AO addition) prepared as described for Reference Example 1 by adding 1500 ppm Irganox 1010 and 1500 ppm Irgafos during the above described extrusion step was feed to the SbR process using activated carbon as adsorption media.

All samples were heated at 270°C for 120 minutes at ambient pressure and in nitrogen atmosphere. Samples for measuring the Mw values were taken at 30min, 60min and 120min. The results are shown in Figure 2.

The results clearly show that at 270°C a high amount of additives is needed to prevent degradation of the polymer. IE1 sample containing a recycled PP with more than 1500 ppm Irganox 1010 was not showing any change in the Mw value.

Example 2: Effect of antioxidants at temperature of 250°C

The same thermal treatment as disclosed for Example 1 was carried for samples CE1 , IE2 and IE3 with the difference that a temperature of 250°C was used.

Samples for measuring the Mw values were recovered at 0 min, 15 min, 30 min and 60 min. Figure 3 A) and Figure 3 B) show the MWD before and after thermal treatment for samples IE2 and IE3 respectively.

Figure 4 shows the MWD before and after thermal treatment for comparative sample CE1. At a temperature of 250°C, a small amount of antioxidant is demonstrated sufficient to avoid thermal degradation.

Figure 5 shows the protective effect of the antioxidants of samples IE2 and IE3 as compared to sample CE1 in a thermal treatment at 250 °C under nitrogen atmosphere. Comparative sample CE1 shows a clear thermal degradation.

Thus, absence or low content of antioxidants in the polypropylene recyclate obtained from the SbR process is expected to have a significant impact on the thermal stability during the subsequent separation steps at temperatures within the range of from 150 to 300 °C. Thermal degradation can be avoided by the addition of a solution or dispersion comprising antioxidant(s) prior to separation at high temperatures, such as 250-270°C.

Example 3

A first solution comprising 10 weight% of the primary antioxidant Irganox 1076 in n- heptane was prepared. The solubility of Irganox 1076 in n-heptane at room temperature is > 10 weight%.

A second solution comprising both the primary antioxidant Irganox 1076 (2.5 weight%) and the secondary antioxidant Irgafos 168 (5 weight%) in n-heptane was prepared. The solubility at room temperature for the latter it is only ~ 5 weight%. The solutions were injected into a melt of non-stabilized (with no antioxidant) polypropylene (PP) homopolymer powder in a lab scale twin screw extruder. The polypropylene was a homopolymer with a weight average molecular weight (M_w) of 440 kg/mol. The respective formulations and antioxidant (AO) target concentrations are given in Table 4. Antioxidant (AO) target concentrations in Table 4 are given in weight ppm based on the total weight of the composition of PP, n-heptane and antioxidant(s).

Table 4: Target concentrations of the AOs in PP

The extrusion conditions were always kept constant at 400 rpm screw speed and 5 kg/h throughput. The set temperature profile was 195°C, and the melt temperature was about 200°C for all runs. The first compounding step providing sample 1 was followed by two further re-compounding passages providing sample 2 and sample 3 under the same conditions to simulate the thermo-mechanical stress of subsequent process steps (e.g. conversion operations).

The MFR2 was measured for all samples prepared. The results are shown in Figures 6.

Without stabilizer (CE1 ), the MFR2 of the homo PP reaches ~13 dg/min after the first processing, and it climbs to over 40 dg/min after two further extruder passages (Figure 6). With the maximum stabilization package (IE6) used, i.e. 1000 ppm Irganox 1076 and 2000 ppm Irgafos 168, a MFR of ~2 dg/min was reached, which increased only slightly over the two following extruder passages.

The results show that adding an antioxidant in a solution of n-heptane provides stabilization of the polyolefin.

Example 4

A first solution comprising 10 weight% of the primary antioxidant Irganox 1076 in n- heptane is prepared. The solubility of Irganox 1076 in n-heptane at room temperature is > 10 weight%.

The solutions are injected into a purified solution of SbR polypropylene dissolved in n- heptane obtained at the outlet of the adsorption section of the above described solventbased recycling process (SbR).

Antioxidant (AO) target concentrations in weight ppm based on the total weight of the polypropylene are 1000 ppm Irganox 1076.

The n-heptane is then vaporized at 60°C under vacuum over night from the resulting stabilized polymer solution to retrieve stabilized polypropylene in solid form.

The stabilized polypropylene is then heated at 270°C at for 120 minutes at ambient pressure and in nitrogen atmosphere to simulate the thermal conditions to which polypropylene in a product stream originating from a solvent based polyolefin recycling process would be exposed to in the subsequent separation steps. Samples for measuring the Mw values are taken at 30min, 60min and 120min.

As a comparative example, a non-stabilized solution of polypropylene dissolved in n- heptane is exposed to the same treatment.

Example 5

A solution comprising 10 weight% of the primary antioxidant Irganox 1076 in n-heptane is prepared. The solubility of Irganox 1076 in n-heptane at room temperature is > 10 weight%.

The resulting stabilized polymer solution is then subjected to separation at a temperature within the range of from 150 to 300 °C to retrieve a PP recyclate. As a comparative example, a non-stabilized purified solution of SbR polypropylene dissolved in n-heptane is exposed to the same treatment.

The MFR2, which is indicate of PP molecular weight, is then measured for the retrieved polypropylene samples.

Claims

1 . A process for the separation of at least one polyolefin from a product stream (a) originating from a solvent based polyolefin recycling process, wherein the product stream (a) comprises the at least one polyolefin dissolved in a solvent preferably comprising a n-alkane, the process comprising the steps of:

A) optionally adding a solution or a dispersion (s1 ) comprising an antioxidant and preferably a n-alkane to the product stream (a), thereby providing a stabilized product stream;

B) separating at a temperature of from 150 to 300 °C a first polyolefin-rich stream (c) from the product stream a) or, when step A) is carried out, from the stabilized product stream;

C) optionally adding a solution or a dispersion (s2) comprising an antioxidant and preferably a n-alkane to the first polyolefin-rich stream (c), thereby providing a stabilized polyolefin-rich stream;

D) subsequent of step C) when present, separating at a temperature of from 150 to 300 °C a second polyolefin-rich stream (c’) from the stabilized polyolefin-rich stream ; wherein the process comprises at least one of step A) or step C).

2. The process according to claim 1 , wherein the polyolefin is a polypropylene polymer or a polyethylene polymer.

3. The process according to claim 1 or 2, wherein the antioxidant comprises or consists of primary antioxidants preferably comprising, or consisting of, a sterically hindered phenol wherein the sterically hindered phenol is preferably selected from Octadecyl 3-(3',5'-di-tert. butyl-4- hydroxyphenyl)propionate] , 2,2’-thiodiethylenebis-(3,5-di-tert. butyl-4- hydroxyphenyl)-propionate, 2,5,7,8-Tetramethyl-2(4’,8’, 12’- trimethyltridecyl)chroman-6-ol or combination thereof.

4. The process according to any of claims 1 to 3, wherein the antioxidant further comprises a secondary antioxidant, preferably comprising or consisting of phosphites or phosphonites.

5. The process according to any of the proceeding claims, wherein in step A) the antioxidant is added in an amount ranging from 100 ppm to 4000ppm based on the polyolefin content of product stream (a).

6. The process according to any of the proceeding claims, wherein in step C), the antioxidant is added in an amount ranging from 100 ppm to 4000ppm based on the polyolefin content of first polyolefin-rich stream (c).

7. The process according to any of the proceeding claims, wherein the process comprises all of steps A), B), C) and D).

8. The process according to any one of the proceeding claims, wherein the solvent of the product stream (a) comprises or consists of a n-alkane, wherein the n-alkane is preferably selected from C4, C5, C6, C7, C8, C9, C10, C11 , C12 n-alkanes and any mixtures thereof, more preferably C4, C5, C6, C7, C8 n-alkanes and any mixtures thereof, most preferably the n- alkane is selected from a C6, C7, C8 n-alkane and any mixtures thereof.

9. The process according to any one of the proceeding claims, wherein the solution or of the dispersion (s1 ) of step A) and/or the solution or dispersion (s2) of step C) comprises a n-alkane selected from a C4, C5, C6, C7, C8, C9, C10, C1 1 , C12 n-alkane and any mixtures thereof, preferably the n- alkane is selected from a C4, C5, C6, C7, C8 n-alkane and any mixtures thereof, most preferably the n-alkane is selected from a C6, C7, C8 n-alkane and any mixtures thereof.

10. The process according to any one of the proceeding claims, wherein the solution or dispersion (s1 ) of step A) and/or the solution or dispersion (s2) of step C) comprises a solvent which is the same solvent as of the product stream (a), preferably selected from a C6, C7, C8 n-alkane and any mixtures thereof.

1 1 . The process according to any one of the proceeding claims, wherein, before step B) or before step A) if present, the process further comprises

A⁰) carrying out a purification, preferably by settling and/or a filtration and/or an adsorption, from impurities on a polymer solution stream (a⁰) comprising the at least one polyolefin dissolved in the solvent to provide the product stream (a).

12. The process according to any one of the proceeding claims, wherein the product stream (a) comprises less than 1 wt% of undissolved material based on the weight of the product stream (a).

13. The process according to any one of the proceeding claims, wherein the process further comprises

14. The process according to any one of the proceeding claims, wherein the separation of step B), and preferably each separation of step D) and step E), is a vapor-liquid separation.

15. A polyolefin separated from a solvent obtainable by a process according to any of the preceding claims.