Recycled polyolefins deodorization process

Abstract

Process for the production of deodorized polyolefins, starting from a post-consumer recycled polyolefins feedstock. The process further comprises the falling strand deodorization technology, which, under specific process parameters, significantly reduces the odoriferous substances and, particularly, the semi-volatile organic compounds (SVOCs) of the feedstock.

Description

[0001]RECYCLED POLYOLEFINS DEODORIZATION PROCESS Cross-Reference to Related Applications This Patent Application claims priority from Italian Patent Application No. 102024000015031 filed on June 28, 2024, the entire disclosure of which is incorporated herein by reference. Technical Field The present invention relates to the process for deodorizing recycled polyolefins. In particular, the present invention relates to a process for the production of polyolefins starting from a recycled polyolefin raw material. For example, the polyolefin raw material is coming from post-consumer user. More in particular, the present invention relates to a process for the production of recycled polyolefins that are odor-free or odor-reduced and, thus, can be used for application requiring low or no smelling. State of the Art It is well known that post-consumer recycled (PCR) materials have the drawback of retaining odorous molecules from, for example, rotting organic material. The emission of these unpleasant odors (in the form of high and / or semi- volatile substances) therefore limits the reintroduction of recycled plastics into the market, thereby hindering the implementation of a circular economy. To date, at least three types of technologies are known to be employed in deodorization processes for plastic materials, in particular for recycled polyolefins. The first technology involves the addition in the post- use recycled plastic of substances that have deodorizing effect. In this regard, E. Garofalo et al. in “Assessment of Melt Compounding with Zeolites as an Effective Deodorization Strategy for Mixed Plastic Wastes and Comparison with Degassing”, Polymers 2023, 15, 1858, describes the technical effects related to the dosing of chemical compounds with deodorizing action during a post-consumer polyolefin extrusion process in order to reduce odorous emissions of polymeric materials. In this work, particular types of zeolites were tested as adsorbents of volatile organic compounds (VOCs) odoriferous substances during the extrusion of recycled plastic. Zeolites are particularly suitable as adsorbents due to their ability to capture and "retain" the adsorbed substances at the high temperatures of the extrusion process. The deodorization strategy, which involves the addition of compounds with a deodorizing action, was compared with traditional deodorization techniques (an extruder equipped with a degassing system). In this article, it is evident the poor efficiency in terms of reduction of volatile organic compounds (VOCs) odoriferous substances when the post-consumer polymeric material is subjected to treatment in an extruder equipped with a degassing system, even when the polymeric material is added with H2O in order to promote the stripping of odorous substances. The addition to the polyethylene polymer of particular zeolites in high concentration (e.g. 4% w / w) allows to obtain better performance in terms of reduction of volatile odorous substances compared to the results obtained using a degassing extruder. However, this article does not provide any indication with reference to the possibility of reducing / removing semi-volatile organic compounds (SVOCs) odoriferous substances from post-consumer polymeric material. The evaluation of the effectiveness of the treatments (standard degassing extruder vs zeolite treated material) were carried out by means of panel tests where trained humans evaluated the strength of the odor present in the treated polymers. In line with this, patent application CN111004425 discloses a method for the reduction of odors present in post-consumer polyolefin materials through the use of an extruder equipped with a degassing system. The invention provides a method for preparing low-volatile resin, which solves the problems of high volatile component content and heavy odor of current polyolefin resin materials, as well as the complexity and high cost of existing technologies. By adding low molecular weight additives and antioxidants, the invention performs melt extrusion and devolatilization of the resin in the extruder. The prepared resin has low volatile gas content, weak odor, and has good impact resistance, strength and toughness. The disclosure provides a method for preparing low-volatile resin, including: 1) Dry and filter screening the polyethylene powder to meet the requirements of the extruder; 2) Preheat and clean the screw extruder; 3) Mixing the raw material polyethylene powder resin with low molecular weight additives and antioxidants; 4) Extrude the mixture under the action of pressure; 5) Cooling and pelletizing. Preferably, a low molecular weight additive with a weight percentage of 0.01-1% is added to the screw extruder. Preferably, the low molecular weight additive is composed by deionized water (60-90 wt%) and surfactant (10-40 wt%). Preferably, the low molecular weight additive and antioxidant are added at the same time, and the raw material composition is as follows (percentages by weight): 1) Polyethylene 97-99.97% 2) Antioxidant 0.02-2% 3) Low molecular weight additive 0.01-1%. However, this patent application does not provide any indication with reference to the possibility of reducing / removing semi-volatile organic compounds (SVOCs) odoriferous substances present in polyethylene material subjected to degassing extruder treatment. The addition of antioxidants and low molecular weight additives, even in significant quantities, in addition to modifying the characteristics of the polymer, makes the process disadvantageous in economic terms. It should also be noted that the degassing manifold fixed to the extruder necessary for the removal of volatile substances is inevitably subject to occlusions and therefore frequent machine downtime is to be expected with consequent production losses. In the same context, patent application CN112606257 discloses a process that makes it possible to produce polyolefin polymeric material, with a reduced content of odorous substances, by adding nucleating agents, antioxidant compounds to the polymeric material to be deodorized and subjecting the material to an extrusion process with an extruder equipped with a degassing system. In order to achieve the purpose, the process of the invention for preparing low-odor and narrow-molecular-weight-distribution high-melt-index polypropylene comprises the following steps: (1) adding 95-99 parts of polypropylene, 0.2-0.5 part of nucleating agent, 0.1-0.5 part of antioxidant and 0.1-0.5 part of processing aid into a double-screw extruder according to the mass parts, and carrying out melt blending;(2) adding 0.6-3.5 parts of a degrading agent in batches to obtain the high-melt-index polypropylene; the degradation agent is added in at least 3 batches; the length-diameter ratio of the double-screw extruder is 56-64, and at least 10 sections of the double-screw extruder are provided with at least 3 feeding ports and at least 2 devolatilization ports. In this patent application it is clear that in order to remove odorous substances it is not enough to use an extruder equipped with a degassing system, but it is necessary to add to the polymer with substances with a deodorizing action capable of promoting the removal of odorous substances. However, the efficiency of this process with regard to the removal of semi-volatile organic compounds (SVOCs) odoriferous substances is not disclosed. Patent application WO2014147106 refers to a thermoplastic formulation containing recycled polyolefins, comprising at least one polypropylene (PP), and at least one polyethylene (PE), in combination with metal oxides and / or hydroxides; preferably with at least one of CaO, MgO, Al2O3, ZnO and / or at least one of their hydroxides. In particular, the application discloses the use of at least one of CaO, MgO, Al2O3, ZnO in the process of recycling polyolefins as a drying agent, as a deodorant and as a biocidal agent. Preferably, the metal oxide to be used as water and smell scavenger, i.e. as a deodorant and as a drying agent, particularly the calcium oxide, is dispersed or in any case inserted in a polymer matrix compatible with the claimed polyolefin formulation, to form a drying compound, generally in the form of granules. The metal oxide drying agent, preferably CaO, represents at least the 20 wt% of the compound formed by the polymer matrix of the compound granule or pellet and the drying agent. The drying compound, made of polymer and metal oxide, preferably calcium oxide, is present in the final mixture, ready to be used in the extrusion or injection molding process, in a range comprised between 0.4% and 20%. Thanks to the use of calcium oxide or at least one of the mentioned drying metal oxides, the production molding process is essentially odorless, as well as the manufactured products, at the end of the cooling process. Thus, CaO and the other oxides prove to be effective as deodorant. However, the addition of metal oxides to the polymer can lead to a deterioration of the properties of the polymer depending on the amount of inorganic fillers added. In addition, no examples are disclosed in this document demonstrating the efficiency of metal oxides as agents capable of effectively reducing the content of semi-volatile organic compounds (SVOCs) odoriferous substances, present in post-consumer polyolefin materials. Patent application WO2020176290 deals with a composition and process to remove odors from olefin-based polymers. The composition includes an olefin-based polymer and from 0.15 wt% to 15 wt% of an odor suppressant. The odor suppressant includes from 0.05 wt% to 2 wt% of a metal oxide having a band gap greater than 5.0 electron volts (eV), and (ii) from 0.1 wt% to 13 wt% of an acid copolymer. The ratio of metal oxide to acid copolymer is from 1:20 to 1:1. The efficacy in odor reduction is measured by evaluating the reduction of the odorous substance propanal (boiling point = 49°C) as a function of the concentrations of CaO and acid copolymer. It should therefore be noted that no information is given whether the process of the disclosed invention is also able to reduce the concentration of semi-volatile organic compounds (SVOCs) odoriferous substances present in PCR polyolefins. Patent application WO2021170599 discloses a polyolefin composition comprising (a) a hindered amine light stabilizer, (b) a hydrotalcite or an inorganic oxide, and (c) a hydroxylamine stabilizer or amine oxide stabilizer, and to the use of components (b) and (c) for reducing odor in a polyolefin composition comprising a component (a). The used polyolefin can be virgin or recycled material or blends. From the examples shown in Table 1 it can be inferred that large quantities of additives are required to significantly reduce the content of an odorous substance such as butyric acid (compound with boiling point 163°C). Moreover, there are no examples in this patent application that show that this process is efficient in the reduction of semi-volatile organic compounds (SVOCs) odoriferous substances. Patent application WO2022260998 deals with a process to reduce odors in PCR polyethylene. It is reported that volatile organic compounds, such as oxygenated compounds and limonene, contribute significantly to poor odor and / or taste properties of PCR materials. The proposed solution involves the use of an extruder equipped with a degassing system and the dosage of particular types of zeolites. It is known that the addition of inorganic fillers (e.g. zeolites) causes a worsening of the properties of the polymer depending on the amount of fillers added. It should be noted that this patent application does not provide information with reference to a reduction in the concentrations of semi-volatile organic compounds (SVOCs) odoriferous substances. In fact, tables 3 and 4 show the reduction of limonene, aldehydes, ketones, THF and oxygenated compounds, but no data is given on semi- volatile organic compounds (SVOCs) odoriferous substances. Moreover, the process discloses in this patent application is complex and requires the purification of the extraction solvent. Patent application WO2021250134 proposes a process to reduce the odors to polymer compositions by adding and dispersing in the polymer to be treated functionalized silicate particles. These silicate particles are a zeolite particle selected from mordenite, clinoptilolite, chabazite, and are functionalized by a grafting compound. Functionalized mordenite was the most effective additive in reducing odor. However, the process disclosed in this patent application is silent about the possibility of reducing the semi-volatile organic compounds (SVOCs) odoriferous substances. Finally, patent US5350788 relates to recycled plastics which exhibit noxious odors. More specifically, the disclosure is directed to a method of reducing unwanted odors in recycled plastics by incorporating a polyalkylene imine ("PAI"), more preferably polyethylene imine ("PEI"). The process involves adding the PAI and recycled polymer in a weight ratio of about 0.001-50:100-100000, more preferably 0.001-30:100 to a compounding extruder, Banbury mixer or the like, followed by blending and pelletizing. Films molded or thermoformed articles produced from such granules are claimed as well. The recycled polymer is preferably a polyolefin such as polyethylene homopolymers, as well as copolymers with vinyl ester monomers such as acetates. Recycled polymer that had rancid odor prior to treatment was analyzed by GC-MS and the results showed acetaldehyde, and trace amounts of propanal, butanal, pentanal and heptanal; the analysis also detected low boiling hydrocarbons (butene, pentane, heptane, octene, octane, decane, tridecane), ethanol and acetic acid. Therefore, it was inferred that not only butyric acid but also the above-mentioned compounds could produce unpleasant odors in plastics. By means of a second technology, the removal of the odorous substances is performed via degassing extruders and other special equipment. In line with this, patent application JP2005116205 relates to a method for producing a polyolefin polymer having reduced odor, excellent heat aging resistance and weather resistance. This process involves the reduction of the content of odorous substances contained in polyolefin materials by adding water to the polymer and treating the polymer in an extruder equipped with a degassing system. No information is available in this patent application about the efficiency of this process and no information is given for the removal of semi-volatile organic compounds (SVOCs) odoriferous substances. Patent application JP2005350619 describes a method for producing a polyolefin resin with less odor in a short time without requiring a large facility, characterized in that water is added from 0.1 to 5 parts by weight, more preferably 0.3 to 3 parts by weight, and particularly preferably 0.5 to 2 parts by weight with respect to 100 parts by weight of the polyolefin. The extruder has at least one vent port to remove inert gases and water. From that port, vacuum is applied (- 760 to -500 mmHg, preferably -760 to -600 mmHg, particularly preferred -760 to -700 mmHg). It is claimed that the treatment of the polymer in an extruder equipped with a degassing system allows to reduce the concentration of volatile organic compounds (VOCs) odoriferous substances. In the examples of the invention, the contents of dodecane (evaluated as an odorous substance) are analyzed. Dodecane is still a VOC as its modified Kovats index (MKI) is lower than 1300. In this patent application it is disclosed that by applying high vacuum degassing extrusion, and by introducing appropriate quantities of water into the polymer mass, it is possible to reduce the concentrations of odorous substances such as dodecane which is a VOC. However, this disclosure is silent about the possibility of reducing semi- volatile organic compounds (SVOCs) odoriferous substances. Patent application EP3981486 relates to a method for the elimination of odors in recycled plastic materials based on the removal of volatile organic compounds by means of steam distillation. In particular, the proposed process is based on the removal of VOCs by means of steam distillation. This invention applies to plastics of varied nature, such as polyethylene (PE), polypropylene (PP), polyester (PET) from plastic waste of industrial or domestic origin. This patent application does not provide any indication of the efficiency of the claimed post-consumer polymer deodorization process and does not show the efficacy in the reduction of the content of semi-volatile organic compounds (SVOCs) odoriferous substances. Patent application WO2021211646 proposes a method to purify a plastic feed, in the bulk and on the surface, which includes the step of liquid / liquid contaminant extraction using an extraction solvent, at an appropriate pressure and at a temperature which is higher than the melting temperature of the polymer to be treated. Example of contaminants are alkyl phenols, bisphenols, dioxins, PCBs, and phthalates. However, this patent application does not disclose the reduction of semi-volatile organic compounds (SVOCs) odoriferous substances. Patent application WO2005080060 discloses a method and an apparatus for treating plastic waste materials, in which the plastic is heated and partially melted while falling by gravity and the vapours are filtered to remove the smell. According to an aspect of this patent application, plasma technology may be used to remove odors and volatile organic compounds that are generated, in particular it is disclosed the use of a filter employing atmospheric pressure non- equilibrium plasma (APNEP) to filter odors and VOC. Patent application WO2023148026 discloses an apparatus and method for reprocessing post-consumer plastic waste that is shredded and washed, comprising a “melting extruder” to homogenize the feed and a “degassing extruder” for degassing the plastic melt and a granulating device. An ozone generator is connected so that ozone can be supplied at any point along the path (i.e. in any or both extruders or between them). The process disclosed in this patent application offers an efficient and at the same time environmentally friendly process for processing post-consumer waste. The cleaning efficiency is so high that the produced material is odorless. It should be emphasized that in this process, to remove odorous substances contained in post-consumer polyolefin polymeric materials, an extruder equipped with a degassing system (a device normally used to reduce volatile substances present in polymers) is used in combination with the addition of ozone. Therefore, it can be inferred that a simple degassing extruder is not enough for performing the deodorizing process. However, the use of ozone is harmful, requires very special and expensive materials (especially gaskets) as ozone is extremely oxidizing and makes the whole process complex. Patent application US20210402651 discloses a method and device for recycling plastics, where the recyclable material is melted using a discharge extruder, filtered using a first filter device; degassed; and discharged using an extruder. The degassing device has at least one filter element and a vacuum chamber at 0.5 to 50 mbar to degas. This patent application has the particular advantage that the process steps of filtration and degassing are carried out in one process step. In fact, the filtered plastic melt can be degassed directly by filtration in a vacuum atmosphere. Large-area contact zones between the plastic melt and the vacuum atmosphere can thus be achieved so that the volatile constituents can be released from the plastic melt in a relatively short dwell time, thus minimizing degradation. Moreover, a high degree of purity in the plastic melt can be produced by the multi-stage filtration. It is worth noting that this patent application requires special equipment, such as filter inside the devolatilizer apparatus. In addition, filters are prone to clogging and they are difficult to clean as they are inside the devolatilizer chamber. Moreover, this disclosure does not deal with the efficiency of this process in removing semi- volatile organic compounds (SVOCs) odoriferous substances. In regard to a process which treats a recycled polymer feedstock, EP2419255 discloses a method and apparatus for recycling plastic materials, which includes, preferably in sequence, the following steps: (a) preparation of the raw material, such as optional comminution and degassing of the (solid) polymer mixture, (b) melting, (c) filtering, (d) homogenizing (preferably by intense shear or tensile stress and by acceleration) and (e) degassing the homogenized melt, (f) discharging and / or subsequently processing the polymer melt (such as by granulation). Preferably, the temperature of the polymer entering the degassing step (e) is the highest of all the steps. The description underlines the importance of comminution and homogenization steps, that should be carried out after filtration but before melt degassing, as it makes more efficient the process since the contaminants are more evenly distributed. The given examples report the degassing efficiency only qualitatively; moreover, compared to this patent application, the present invention is simpler, requiring less steps (in particular, not requiring the homogenizing step). The third technology regards the falling strand devolatilization technology. According to this technology, in order to remove undesired volatile compounds, the polymer is heated up and transferred to the top of a degassing vessel, where it is passed through a distributor comprising a large number of very small apertures, positioned vertically on the bottom of the distributor. In such a way, the polymer, exiting such holes, produces strands that slowly fall down in the vessel. The vessel is subjected to a very low pressure, so that the volatile compounds are removed. The strands have a very large surface to volume ratio, making the process quite effective. The strands collect on the bottom of the vessel, where a polymer pool is generally formed. A substantial number of patent and non-patent literature has dealt with the removal of volatile organic compounds (VOCs) from polymers by means of the falling strand devolatilization technology. For example, this technique is used for removing the polymerization solvents and monomers as well as for reducing the content of waxes (i.e., oligomers). In this regard, A. De San Luis et al. in "Removal of volatile organic compounds from bulk and emulsion polymers: a comprehensive survey of the existing techniques" Industrial & Engineering Chemistry Research 58.27 (2019): 11601-11623, evaluates different methods to remove VOCs from polymers such as polystyrene. Among other methods, the falling strand devolatilization is outlined (at pages 11606- 11607). This method is described as suitable for viscous polymers (around 1 Pa·s of viscosity) containing a lower concentration of VOCs compared to others devolatilization methods. According to this review, polystyrene, polyethylene, and polysiloxanes are examples of polymers purified using a falling-strand devolatilizer. However, the only cited example was on a polystyrene having 10-40 wt% of styrene treated at 200-280°C and a pressure between 6700 and 26700 Pa in the first devolatilizer tank and 400 to 2700 Pa in the second devolatilizer tank. In this way, the VOCs content was, in most cases, from 0.01 to 0.05 wt% (i.e. 100- 500 wppm). This review cites also R. J. Albalak et al. in “Polymer Melt Devolatilization Mechanisms” AIChE J. 1990, 36, 1313, who studied the mechanism of falling strand devolatilization of polymer melts, such as polyethylene (LDPE). WO 2023 / 001855 discloses a devolatilization apparatus for removing volatiles from a polymer melt feed, which comprises a nozzle to distribute the polymer, configured to form polymer strands; a collector, configured to receive the polymer strands in the devolatilization vessel; a polymer outlet to remove the degassed polymer from the vessel; and a gas outlet to remove the volatiles. This apparatus is characterized in that the average aperture diameter of the polymer distributor is from 0.5 to 8.0 mm and in that the strand drop height is between 1 and 20 m. This patent application also relates to the process for reducing volatiles in a polymer melt feed. Polyethylene is in the list of the polymers that can be processed according to this patent application. Most of the examples are for polystyrene but there is also one example on polyethylene, which is example 8. In this example, polyethylene having a viscosity at the inlet of devolatilizer of 4100000 cP (4100 Pa.s) at shear rate value of 10 s-1and 260°C, is treated in a falling strand devolatilizer at 5 mbar(a), by passing through holes having an aperture diameter of 1.2mm. The strand height (“drop height”) was 6 meters. However, WO 2023 / 001855 does not deal with the reduction of the semi-volatile organic compounds (SVOCs) odoriferous substances. Parallel application WO 2023 / 001854 discloses a process, as well as the relative devolatilization apparatus, for reducing volatiles in a polymer melt feed. It differs from WO 2023 / 001855 in few details: the introduction of an additional parameter (such as the ratio of strand drop height / average aperture diameter). Also, in WO 2023 / 001854 there is an example with polyethylene (namely example 8) characterized by exactly the same parameters and process conditions of example 8 of WO 2023 / 001855: the results are exactly the same (1350 to 75 wppm). It is worth pointing out that neither WO 2023 / 001855 nor WO 2023 / 001854 deal with recycle or post use polymers, let alone polymers with odoriferous substances and relative method to remove them from recycled polymers. More, no hints are given that the apparatus would be able to reduce the content of compounds that are not volatile. In regard to a process which treats a recycled polymer feedstock, WO 2012 / 119165 discloses a device for removing contaminants from a polymer melt, characterized by one or more chambers where the polymer melt is distributed to a perforated plate having openings less than 1.5 mm and falls down in thin filaments under reduced pressure, more preferably less than 20 mbar, in particular 2-5 mbar, so that impurities diffuse as a result of the temperature and the negative pressure. Such filaments have diameter less than 1.5 mm and fall freely without contact with the wall of the chamber. The teachings of this patent apply to the production of plastic material or the recycling of plastic material (such as PET) containing water as well as other contaminants, which are reduced by means of a vertical strand devolatilization. However, this patent fails to suggest that this technology is useful to produce polymers, starting from post-consumer polymers, with reduced content of semi- volatile organic compounds (SVOCs) odoriferous substances. In light of the prior art analysis, it is thus evident that each of the three technologies employed for deodorizing process in post-consumer recycled polyolefins have some drawbacks. Starting from the first technology, requiring the addition of molecules (e.g. polyalkylene imine, zeolites, functionalized silicates, metal oxides), these molecules may remain in the final polymer alternating mechanical, electrical, and aesthetic properties (e.g., colors), limiting the action of other additives (e.g., antioxidants, flame retardants, etc.), and posing possible toxicological problems. Regarding the second technology, it requires complex and costly equipment, for example it involves the use of special unit operations (such as devolatilizing filters, vacuum mixing, ozone and plasma treatment etc.). On the other hand, the falling strand technology, known in the polystyrene field, has never been applied for the removal of semi-volatile contaminants in polyolefin material. Moreover, in general, none of the known technologies are able to remove or reduce semi-volatile organic compounds (SVOCs) odoriferous substances from post-consumer recycled plastic. Since most recycled plastic are polyolefins, there is a need to find a process that makes recycled polyolefins free of odorous substances and thus employable in high value- added areas. Summary of the Invention To address the deficiencies of the prior art, the present invention provides a new process for the production of deodorized polyolefins usable in high value-added applications. In particular, the present invention combines cost and environmental benefits with improved deodorization efficiency over the known art. This is achieved by a process described in claim 1 and further by the subject-matters of the further independent claims. The invention further relates to deodorized polyolefins obtained according to the process claimed in the present invention, as described in claim 16. The invention further relates to the use of the deodorized polyolefins obtained according to the process claimed in the present invention, as described in claim 17. Further features and advantages of the disclosed subject matter, whether explicitly mentioned or not, will become apparent in view of the disclosure provided below. In brief, a process for the production of deodorized polyolefins is disclosed, whose feeding material has been chosen for promoting sustainability and circular economy, and the deodorization technology has been selected for achieving a level of reduction of odor such that the resulted polyolefins are used for high value-added applications, where, currently, only virgin polymer was used. Indeed, differently to the known processes employing similar deodorization technology, the present invention applies this technology over a different and more contaminated feeding material. Said deodorization technology, therefore, shows high removal efficiency of all the odorous substances, which are present in the feeding material (such as volatile, semi-volatile, very-volatile compounds). Thanks to the combination of the specific feeding material with the deodorization technology, the present process is an environmentally friendly and efficient process. Surprisingly, the present process is not only able to remove very-volatile and volatile organic compounds (VVOCs, VOCs) odoriferous substances, but it also leads to the removal or, at least, to the reduction of semi-volatile organic compounds (SVOCs) odoriferous substances, which are normally present in post-consumer recycled polyolefins. In particular, a part from the very-volatile (VVOCs) and volatile (VOCs) organic compounds, the present process is also able to reduce of at least 50 wt% the semi-volatile organic compounds (SVOCs) odoriferous substances. Other advantages are also achieved by the present process. For example, this process is: - quick: the deodorization step takes place in seconds; this also ensures little or no degradation of the treated polymer, even at elevated treatment temperatures. - simple and easy in terms, for example, of deodorization phase. This means that the present process achieves very good reduction in odours by means of a single deodorization phase, performed in one single deodorization apparatus. Comparable efficiency can be obtained by using more deodorization apparatus in series; - efficient: the reduction of semi-volatile organic compounds (SVOCs) is very high, even though they have a higher modified Kovats index, and typically high boiling point and high molecular weight; - free of fluids: the present process does need neither injection of liquids or gases (such as water, CO2) into the polymer to be deodorized, nor stripping gases inserted in the devolatilization apparatus. - free of deodorizing agents, that would remain in the deodorized material after the treatment, impairing mechanical, electrical and aesthetic properties. - able to remove or reduce a large spectrum of odorous substances: not only high boiling point, but also compounds of different polarity (phenyl acetic acid has a pKa of 4.87 while lauric acid has a pKa of 5.3) are removed from the polymer. Moreover, the proposed process has low energy requirements, requires low maintenance, and can be run very easily. Finally, the equipment used for the process of the present invention can be easily cleaned. Brief Description of the Drawings Further characteristics and advantages of the present invention will become clear from the following description, from practical and comparative non-limiting examples and with reference to the drawings attached, in which: - Figure 1 shows a deodorization device used to carry out some of the process steps according to the present invention; - Figure 2 shows a particular apparatus used to carry out the process according to the present invention and that was used for the Examples, comprising an extruder, a static mixer and a deodorization device according to Figure 1; and - Figure 3 shows a sketch of the equipment for carrying out a sensory panel test over the polyolefins obtained from the process according to the present invention and obtained from comparative processes. Detailed Description In more detailed, the subject-matter of the present invention is a process for the production of deodorized polyolefins, which can be used in high value-added applications. For instance, high value-added applications are packaging and containers for cosmetics, detergents, perfumes, household chemicals, soap, bottles, etc. The deodorized polyolefins, obtained according to the process of the present invention, are used for producing: packaging and containers for cosmetics; bottles and rigid containers, such as containers for detergents, personal care products and household chemicals; pipes, used for example in supply of fluids, gas transport, irrigation; bins and drums, used for example for storing and transporting chemicals, oils, lubricants and other materials; flexible packaging, used for example to pack fragile products; shopping bags and rubbish bags; stretch film, used for example to wrap and protect pallets, boxes and other loads during transport and storage; shrink film, used for example to pack and / or protect books, magazines and containers collation such as bottles, cans, or boxes collations. Preferably, the use of the deodorized polyolefins, obtained according to the process of the present invention, is for producing: packaging and containers for cosmetics, containers for detergents, personal care products and household chemicals. Since the polyolefins, obtained by means of the present process, are used in such specific and sensitive applications, it shows a concentration of odoriferous molecules below specific limits, where the limits are the values that would impart a sensible smell in the polyolefins. Optionally, the polyolefins, produced through the present process, can undergo standard further processing, before being used for the above-mentioned applications. For standard further processing are meant all processes that transform plastic, typically in pellets, into the final product. This can be carried out by means of methods that are already used for virgin plastics, such as extrusion, molding or thermoforming, with or without expanding agents and / or other additives that are added for specific purposes, such as nucleating agents, inks, fillers, athermanous agents, and so on. The present process comprises many steps. It starts from step (a) of providing a feedstock based on post-consumer recycled polyolefins. Preferably, the post- consumer recycled polyolefins are post-consumer recycled polyethylene homopolymer, polyethylene copolymer, polypropylene, and mixture thereof. For the purpose of the present description and the following claims, the expression “post-consumer recycled polyolefin” means a polyolefin obtained from a recycling process carried out on post-consumer polyolefin waste. This expression encompasses packaging for solid and liquid products based on polyolefins, such as cosmetic packaging; bottles and rigid containers, such as containers for detergents, personal care products and household chemicals; pipes, used for example in supply of fluids, gas transport, irrigation; bins and drums, used for example for storing and transporting chemicals, oils, lubricants and other materials; flexible packaging, used for example to pack fragile products; shopping bags and rubbish bags; stretch film, used for example to wrap and protect pallets, boxes and other loads during transport and storage; shrink film, used for example to pack and / or protect books, magazines and containers collation such as bottles, cans, or boxes collations. In a preferred embodiment of the invention, said post- consumer polyolefin waste comes from polyolefin waste materials derived (that is, collected and sorted) from post- consumer household waste. Notably, the feedstock used in step (a) of the present process may or may not be certified as based on recycled material. Certification authorities include the APR in USA and the EuCertPlast in Europe, the latter being recognized by other recycling organizations such as the Italian National Consortium for the Collection and Recycling of Plastic Packaging (COREPLA) and Citeo. Some recycled products may also be labelled, such as “The Blue Angel” ecolabel in Germany. The feedstock based on post-consumer recycled polyolefins is obtained from the waste of end consumers, which includes both household users and also commercial and industrial structures or institutes that are end users of the product. Therefore, pre-consumer materials are not included. For the definition of “pre-consumer”, “post-consumer”, “recycling”, and “waste”, reference is made to “Standard Guide for Waste Reduction, Resource Recovery, and Use of Recycled Polymeric Materials and Products” (ISO 15270:2008(E)). In the present document, the adjective “recycled” refers to a material that had been subjected to recycling. The feedstock of step (a) based on post-consumer recycled polyolefins comprises: (i) polyolefins ranging from 80 wt% to 99.5 wt%, preferably from 90 wt% to 99.0 wt%, more preferably from 95 wt% to 99.0 wt%; (ii) semi-volatile organic compounds (SVOCs) odoriferous substances, as defined here below and ranging from 0.0001 wt% to 1.0 wt%; (iii) optionally, polymeric impurities, as defined here below; (iv) optionally, non-polymeric impurities, as defined here below; and (v) water ranging from 0 wt% to 9.9999 wt%. Notably, the weight percentages are computed with respect to the total mass of the feedstock based on post- consumer recycled polyolefins. Optionally, to improve mechanical properties and / or processability, according to some embodiments, the feedstock of step (a) is mixed with virgin (i.e. not post-consumer recycled) polyolefin polymers, in a mass ratio with respect to the feedstock (a) of up to 85:15. Said mixing can be carried out both in the solid state (mixing granules or flakes of post-consumer recycled material with granules of virgin polyolefin polymers) and / or in the molten state. Preferably, the polyolefins (i) are selected from the group consisting of polyethylene homopolymer, polyethylene copolymer, polypropylene, and mixture thereof. More preferably, the polyolefins (i) are polyethylene homopolymer, polyethylene copolymer, and mixture thereof. Said copolymer is made, for example, from ethylene and at least one α-olefin, having 3 to 12 carbon atoms; or from ethylene and at least one vinyl ester, such as ethylene- vinyl acetate (EVA); or from ethylene and at least one alkyl (meth)acrylate, such as ethylene-butyl acrylate (EBA), ethylene-methyl acrylate (EMA), ethylene-methyl methacrylate (EMMA), ethylene-ethyl acrylate (EEA). Preferably said copolymer is made from ethylene and at least one α-olefin, having 3 to 10 carbon atoms, more preferably 3 to 8 carbon atoms. Still more preferably, the polyolefin (i) is polyethylene homopolymer. The α-olefin comonomer can be linear or branched, and two or more comonomers can be used if desired. Examples of useful comonomers include propylene, butene, 1-pentene; 1- pentene with one or more methyl, ethyl or propyl substituents; 1-hexene; 1-hexene with one or more methyl, ethyl or propyl substituents; 1-heptene; 1-heptene with one or more methyl, ethyl or propyl substituents; 1-octene with one or more methyl, ethyl or propyl substituents; 1-nonene with one or more methyl, ethyl or propyl substituents;; 1- decene with one or more methyl, ethyl substituents; 1- dodecene. Specifically, but without limitation, combinations of ethylene with one or more comonomers may include: ethylene / propylene, ethylene / butene, ethylene / 1-pentene, ethylene / 4-methyl-1-pentene, ethylene / 1-hexene, ethylene / 1-octene, ethylene / decene, ethylene / dodecene, ethylene / 1- hexene / 1-pentene, ethylene / 1-hexene / 4-methyl-1-pentene, ethylene / 1-hexene / 1-octene, ethylene / 1- hexene / decene, ethylene / 1-hexene / dodecene, ethylene / 1-octene / 1-pentene, ethylene / 1-octene / 4-methyl-1-pentene, ethylene / 1-octene / 1-hexene, ethylene / 1- octene / decene, ethylene / 1-octene / dodecene. Semi-volatile organic compounds (sVOCs) odoriferous substances (ii) refer to odor-active compounds falling within the definition of sVOCs, provided below. For the purpose of the present description and the following claims, odoriferous substances refer to compounds present in post- consumer plastic that can be perceived by human nose. For instance, the odors perceived by the human nose can be categorized in the following groups: chemical odor (such as solvent, alkane, aromatic, petrol, gasoline, plastic and phenolic odors); fatty odor; waxy odor; cheesy and sulfur odors; pungent odors: (such as acidic, musk, spicy, fecal, pea-like, malty and rancid odors); pleasant food flavor odor (such as caramel-like, chocolate, coconut, butter-like, bready, popcorn-like, coffee-like and vanilla odors); flowery, fruity and soapy odors (such as berry, balsamic, citrus, herbal and minty odors); earthy-moldy odor an their combination. Such odoriferous substances preferably are substances selected from the group consisting of carboxylic acids; esters (cyclic and linear, such as carboxylic esters, fatty acid methyl / ethyl esters); ethers (such as diphenylether); alcohols (such as linalool); aldehydes (such as formaldehyde, benzaldehyde); ketones (such as acetone); sulfides (such as hydrogen sulfide); thiols; ammines (aliphatic and aromatic; such as ammonia, trimethylamine, indole derivatives); aromatic hydrocarbons; terpenes; alkanes (cyclic and linear) and alkenes; phenols; phthalates; ethers; amides; imides; halogenated substances. More preferably, such odoriferous substances are selected from the group consisting of alcohols, aldehydes, terpenes, ketones, carboxylic acids, esters (cyclic and linear, such as carboxylic esters, fatty acid methyl / ethyl esters), ketones (such as acetone); sulfides (such as hydrogen sulfide); ammines (aliphatic and aromatic; such as ammonia, trimethylamine, indole derivatives); imides sulfides (such as hydrogen sulfide); thiols. Examples of such odoriferous substances are given in Table A.1 of the following article: A. Cabanes, F.J. Valdés, A. Fullana, ”A review on VOCs from recycled plastics”, Sustainable Materials and Technologies, Volume 25, 2020, e00179, ISSN 2214-9937, https: / / doi.org / 10.1016 / j.susmat.2020.e00179. This article will be referenced to as “Cabanes et al.” in the present application. Such odoriferous substances can be associated with microbiological spoilage processes and rests of detergents as well as with substances produced by degradation of plastic polymer itself. In general, the organic compounds can be classified in three groups by their volatility: very volatile organic compounds (VVOCs), volatile organic compounds (VOCs), semi- volatile organic compounds (SVOCs) and non-volatile organic compounds. However, there are different and not unambiguous definitions. Therefore, for the purpose of the present description and the following claims, semi-volatile organic compounds (SVOCs), particularly semi-volatile organic compounds (SVOCs) odoriferous substances (ii), refer to compounds having a modified Kovats index (MKI) comprised between 1300 and 2300. The modified Kovats index (MKI) is a generalisation of the Kovats index as described below. The modified Kovats index of a generic compound "i” (MKIi), such as for a semi-volatile organic compound (SVOC) odoriferous substance (ii), is defined by the following formula: ^^^^^^^^ = 100 Where ^^^^, ^^^^13, ^^^^23are retention times (RT) as defined below. More in particular, ^^^^is the retention time of the generic compound for which the modified Kovats index has to be calculated, such as for the semi-volatile organic compound (SVOCs) odoriferous substance (ii); ^^^^13is the retention time of the normal tridecane (CAS number 629-50-5); and ^^^^23is the retention time of the normal tricosane (CAS number 638- 67-5). The retention time (RT) is the measure of the time taken by the generic compound, such as the semi-volatile organic compound (SVOCs) odoriferous substance (ii), to pass through a chromatography column within the gas chromatography analysis, wherein - the column has a length of 30 m, the inner diameter is 0.32 mm and the thickness is 0.1 ^m, - the stationary phase is mega-lap® produced by Mega, - the gas carrier is He at 1 ml / min, - the detector temperature is 320°C, - the injection volume is 1 ^l; - the heating program is set to the following: start at 80°C, increase to 17°C / min up to 320°C, isotherm at 320°C for 12 minutes. The variations in operating conditions of the gas chromatograph, such as temperature and gas flow, can affect retention times. The use of the modified Kovats index (MKI) compensates for these variations, making the data more reliable. Preferably, to measure the total concentration of (ii), the integral of all peaks ranging from n-C13 (modified Kovats index 1300) to n-C23 (MKI=2300), excluded the added internal standard, is computed as described in the experimental part with gas chromatography in the same conditions specified above, with response factor referred to the external standard (i.e. methyl stearate) equal to 1.0. In such a way, the total amount of SVOCs odoriferous substances (ii) can be overestimated because it is assumed to be equal to the total amount of the SVOCs. However, as most of SVOCs present in recycled polyolefins based feedstocks are odoriferous substances, it is reasonable to assume that the corresponding error is negligeable. Preferably, the molecular weight of the semi-volatile organic compounds (sVOCs) is from 80 to 600 Da, more preferably from 100 to 400 Da, even more preferably from 135 to 335 Da. Preferably, the boiling point of the organic compounds (sVOCs), measured at the pressure of 0.1 bar(a) can be preferably from 80°C to 350°C, more preferably from 105°C to 300°C, even more preferably from 150°C to 285°C. By choosing the boiling point at 0.1 bar(a) substances that do not have boiling point at ambient pressure, as they would degrade, can be included. To detect the presence of semi-volatile organic compounds (SVOCs) odoriferous substances (ii), in some embodiments, gas chromatography plus mass spectroscopy (GC / MS) combined with olfactometry, GC / MS-O, is used following Cabanes et al., to clearly detect the presence of at least one odoriferous semi-volatile organic compound (SVOC). In this case, the compounds leaving the GC capillary column are split into two separated capillary columns: one connected to the mass spectrometer and the other to the sniffing port for the sensory identification of odor active compounds by human evaluators (Strangl, M., Fell, T., Schlummer, M., Maeurer, A., Buettner, A., 2017. Characterization of odorous contaminants in post-consumer plastic packaging waste using multidimensional gas chromatographic separation coupled with olfactometric resolution. J. Sep. Sci. 40, 1500–1507. https: / / doi.org / 10.1002 / jssc.201601077.; M. Strangl et al., 2018; and Strangl, M., Schlummer, M., Maeurer, A., Buettner, A., 2018. Comparison of the odorant composition of post- consumer high-density polyethylene waste with corresponding recycled and virgin pellets by combined instrumental and sensory analysis. J. Clean. Prod. 181, 599–607. https: / / doi.org / 10.1016 / j.jclepro.2018.01.137). As taught by Cabanes et al., olfactometry requires the human nose as the human sense of smell is the most powerful instrument to detect and identify odor qualities, since no analytical instrument, such as electronic noses, can perceive the odors as the olfactory system. For this reason, up to now, electronic noses have not replaced sensory techniques that assess, for instance, the air quality in many industries or the emissions from diverse materials such as furniture and vehicle upholstery. According to some embodiments, the semi-volatile organic compounds (SVOCs) odoriferous substance (ii) are the compounds that are detected by the human nose at the sniffing port of a GC / MS combined with olfactometry (GC / MS-O), and that are characterized by a modified Kovats index (MKI) in the range from 1300 to 2300. Preferably, the molecular weight of the semi-volatile organic compounds (sVOCs) odoriferous substance (ii) can be from 80 to 600 Da, more preferably from 100 to 400 Da, even more preferably from 135 to 335 Da. Preferably, the boiling point of the semi-volatile organic compounds (sVOCs) odoriferous substances (ii), measured at the pressure of 0.1 bar(a) can be preferably from 80°C to 350°C, more preferably from 105°C to 300°C, even more preferably from 150°C to 285°C. For the purpose of the present description and the following claims, “polymeric impurity” (iii) comprises other polymers such as polyamides (PA), vinyl aromatic polymers (such as polystyrene (PS), high impact polystyrene (HIPS), styrene-acrylonitrile (SAN), acrylonitrile butadiene styrene (ABS)), polyacrylates, e.g. polymethyl methacrylate (PMMA), polycarbonate (PC), polyesters, e.g. polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyphenylene ethers (PPE), polyether sulfones (PES), polyether ether ketones (PEEK), or polyether sulphides, cellulose, or a mixture thereof. Polymeric impurities of point (iii), as defined in the present invention, in any case do not include polymers as defined in point (i). The total quantity of polymeric impurities (iii) in the feedstock is at most 10 wt%, preferably in the range from 1 to 5 wt%, even more preferably in the range from 1.5 to 3 wt%. For the purpose of the present description and the following claims, “non-polymeric impurity” (iv) comprises antioxidants, such as tris(2,4-di-tert-butylphenyl) phosphite, anti-UV agents, lubricant agents, coloring agents; inorganic additives such as inorganic carbon, in particular carbon black, graphene, coke, graphite; metal salts such as calcium carbonate, calcium sulphate; perovskites and ilmenites such as metal titanates; metal oxides such as titanium oxide, aluminum oxide, iron oxide; metal dichalcogenides; silicates and especially phyllosilicates such as hydrated magnesium silicate, serpentine, chlorite, micas, clay. The total quantity of non-polymeric impurity (iv) in the feedstock is preferably between 0.005 and 5 wt%, more preferably between 0.05 and 3.5 wt%, even more preferably from 0.1 and 2.5 wt%. Polymeric impurities (iii) and non-polymeric impurities (iv) in any case do not include semi-volatile organic compounds (sVOCs) odoriferous substances (ii), as defined in the present invention. That means, for instance, that for the purpose of the present invention, lauric acid (C12H24O2, Modified Kovats Index MKI 1759, molecular weight 200.3 Da, boiling point 220.5°C at 0.1 bar(a), laurel odor) or phenyl acetic acid (C8H8O2, Modified Kovats Index MKI 1422, molecular weight 136.15 Da, boiling point 191.8°C at 0.1 bar(a), honey odor) shall be considered as semi-volatile organic compounds (sVOCs) odoriferous substances (ii),and not non-polymeric impurities (iv). To be also noticed that both lauric acid and phenyl acetic acid are odoriferous substances listed in Table A.1 of Cabanes et al. The feedstock based on post-consumer recycled polyolefins, provided during step (a) of the present process, has been made throughout not-limited recycling processes. Examples of recycling processes include the sorting process that can separate plastics based on their properties, such as density (e.g. by flotation) and real-time sorting based on optical properties, such as near infrared spectroscopy based techniques. Alternatively, high-polyolefin content feedstocks can be produced from application-specific post- consumer sources that are known to use polyolefin based plastics by a large amount, such as packaging and containers for cosmetics, detergents, perfumes, household chemicals, soap, bottles, and so on. Optionally, the feedstock can be pre-treated before step (a) for concentrating the polyolefins content and / or for removing organic residues that are detrimental for its final use. This pre-treatment step can be carried out by single or multiple washing steps in water, or by adding specific additives (such as hydrogen peroxide, ozone, sodium hypochlorite) that can interact with this raw material. The pre-treatment step can be performed for preliminarily reducing the content of some volatile organic (and inorganic) compounds by means of conventional techniques. Such techniques include, for instance, low (such as in the range of 70 to 150°C) temperature degassing as disclosed in US 9,914,156, or high (such as in the range of 200 to 280°C) temperature melt extrusion degassing. Degassing can include stripping agents such as nitrogen, nitrous oxide or carbon dioxide, directly added or produced in-situ by decomposition of carbonic compounds such as sodium hydrogen carbonate or azodicarbonamide. Alternatively, the pre-treatment step can be carried out in a degassing extruder. Such pre-treatment may be useful in particular when high quantities of volatile organic compounds are present in the feedstock; however, it is not mandatory as the present process is very effective even without other conventional VOC-reduction treatments. Optionally, the pre-treatment step is followed by a mixer for homogenizing the pre-treated feedstock. In regard to step (a) of the present process, there are no particular limitations. Therefore, any process known in the art can be used to this scope. For example, the feedstock can be provided in solid state, for instance, in form of granules, or already in the melt state. The latter case (melt state) is typical when the feedstock is pre- treated in the melt state, e.g. by extrusion, for instance for preliminary reduction of volatiles. Following step (a), the present process optionally includes the step of melting the feedstock and, thus, obtaining a polymer melt feed. Obviously, this step is omitted when the feedstock, provided in step (a), is already in a melt state, for example, as a result of the previous pre-treatment step by means of the devolatilizing extruder. The temperature T of the feedstock at the inlet of the deodorization device is ranging from 180°C to 280°C, preferably from 200°C to 250°C, more preferably from 205°C to 240°C, even more preferably from 210°C to 230°C. To bring the feedstock to said temperature T, there are not no particular limitations. For example, it can be carried out by employing conventional means, for instance heat exchangers or extruders. The latter means is particularly effective in melting feedstock based on post- consumer recycled polyolefins. Other means include heating by heating jackets where suitable thermal oil flows, gas heating by means of flow of suitable inert gases such as carbon dioxide, nitrogen, argon; or optical heating such as infrared or microwave heating. Regardless of the presence or absence of the optionally step of melting the feedstock, the feedstock in the form of a polymer melt feed, is brought to the deodorization device, step (b) of the present process, where the polymer melt feed is passed through at least one aperture (step (c)), thus forming at least one polymer strand that falls by gravity in a closed vessel (step (d)) and will continue in the subsequent steps of the present process. With reference to figure 1, an example of the deodorization device 1 is depicted, which is used for performing the falling strand deodorization steps according to the present invention, starting with step (b). The deodorization device 1 comprises at least one inlet section 3 for receiving the polymer melt feed at a target temperature T, at least one distributor 5 with at least one aperture 6, a closed vessel 10, which is connected to the distributor 5 and is provided with at least one polymer outlet 12 and at least one vapor outlet 8. Preferably, the deodorization device 1 receives the polymer melt feed, via the inlet section 3, at the target temperature T, i.e. at the temperature ranging from 180°C to 280°C, preferably from 200°C to 250°C, more preferably from 205°C to 240°C, even more preferably from 210°C to 230°C. If not yet at that temperature, the polymer melt feed can be brought to said target temperature T, for instance by means of a heat exchanger driven by a flow of athermanous fluid. The inlet section 3 can be a duct with one aperture or several apertures from which the polymer melt feed is brought into the deodorization device 1 in step (b). Once the polymer melt feed has brought into the deodorization device 1 within the step (b) of the present process, this polymer melt feed is then passed through the at least one aperture 6 in step (c) of the present process, thereby forming polymer strand(s). In details, the inlet section 3 is in communication with at least one distributor5. However, the deodorization device 1 can also comprise multiple distributions 5: a first distributor may split the polymer melt feed in few polymer channels, a second distributor may distribute the polymer melt feed inside each polymer channel into the apertures 6 of step (c). The shape of the at least one distributor 5 is not limited to the linear one. In particular, circular, ellipsoid or polygonal shapes can be used. The length of each polymer channel is not restricted to be the same for all polymer channels. For instance, the distributor 5 can be in the shape of a spider net, where, for example, a first distributor 5 distributes the polymer melt feed to a second concentrical distributor 5, resulting in annuli having different radiuses and, thus, different circumferences. Alternatively, the single distributor 5 may be not linear but circular or with circular hollow profile, for instance forming an annulus. Hollowed or non-hollowed polyhedral, such as rectangular, hexagonal or square-shaped distributors are also possible. There are no particular limitations to the material of the distributor 5. Typically, the distributor 5 is made in metal, in particular in steel, inconel, incoloy, brass, bronze or titanium alloys. To ensure a good distribution of the polymer melt feed (that is, almost the same flow rate for each aperture 6), the pressure drop of the polymer melt feed from the inlet section 3 to the distribution aperture 6 should be as low as possible. In particular, it may be advantageous that the pressure drop of the polymer melt feed from the inlet section 3 to the distribution aperture 6 is no more than 1 / 10th of the pressure drop of the polymer melt feed passing through the apertures 6 in step (c). That typically means that the equivalent diameter of the distributor 5 and possibly of its polymer channels is much larger than the equivalent diameter of the apertures 6, for instance the ratio of said equivalent diameters is at least 10, more preferably from 2 to 400, even more preferably from 30 to 300. The number of apertures 6 is at least one. When the number of apertures is more than one, the number of apertures per the internal sectional area of the closed vessel 10 is preferably from 10000 [m-2] to 100000 [m-2], even more preferably from 20000 [m-2] to 50000 [m-2], where the sectional area is the area of the internal section of closed vessel which is perpendicular to the vertical direction. When the number of apertures is more than one, the distance between the apertures 6, one another, is preferably between 1.1 and 10 times the equivalent diameter of the apertures at the exit Dex, more preferably between 2 and 5 times. An optional booster polymer pump can be used between step (a) and (b), when the feedstock is in the melt state. Such pump can be useful to increase the polymer pressure up to the value required for the polymer melt feed to pass through the apertures 6 of step (c). Optionally the pump speed can be regulated so as to ensure that the mass flow rates of the polymer melt feed through these apertures 6 in step (c) are within specified ranges. In case such a pump is not foreseen, the same result can be obtained by an upstream pressurizing unit (such as the above mentioned degassing extruder for pre-treatment step). However, in such case there is generally less flexibility, in particular if it is required to vary the mass flow of the polymer melt to ensure that the mass flow per aperture of step (c) stays within the specified ranges. Regardless the shape and the number of distributors 5, each distributor 5 has a number of apertures 6, which can be carried out in any way known in the art. For instance, the distribution apertures 6 can be produced by means of drilling. To obtain apertures 6 of specific shape, or for low diameter holes, or, for non-circular apertures, such as slots, when the minor size of the aperture is small (that is, less than about 1 mm), or to increase the accuracy of the aperture dimensions, other methods can be used. For instance, water cutting or electroerosion cutting (electrical discharge machining). Alternatively, the distributor 5 itself can be produced with the apertures 6. For instance, it can be produced by molding, for instance by lost wax technique, or with additive manufacturing, such as metal 3D printers. The aperture 6 are substantially vertically oriented with respect to the closed vessel 10. By substantially vertically oriented apertures 6 is meant that the angle between the axes of the aperture and the direction of gravity is low, preferably no more than 60°, more preferably no more than 45°, even more preferably no more than 30°, and even more preferably no more than 15°. The apertures 6 of step (c) can be of any shape. In particular, they can be tapered or not-tapered bores or slots. For slots, the section can be rectangular or polyhedral, and in the section, the major dimension is at least 5 times the minor dimension, preferably from 10 to 1000 times. For bores, the section can be for instance polyhedral, circular or elliptical or star-shaped. Preferably it is circular or elliptical, even more preferably circular. The tapering can increase or reduce the sectional area of the aperture 6 from inlet to outlet. Typically, the tapering reduces the sectional area as the polymer melt flows from the inlet to the outlet. If tapering is present, the angle between the axis of the aperture and the lateral wall of the bore is no more than 60°, preferably between 1° and 45°, even more preferably between 2° and 30°, where for angles “°” denotes the sexagesimal degree. Preferably, the bores have circular symmetry. Preferably, the bores are not tapered. For the present process, it is essential that the apertures 6 have an equivalent diameter at their exit (Dex) that is ranging from 0.4·10-3m to 10·10-3m, preferably from 0.8·10-3m to 5·10-3m, even more preferably from 0.9·10-3m to 3·10-3m, still more preferably from 1·10-3m to 2.5·10-3m. In the present disclosure, the equivalent diameter is meant as the ratio of the area of the aperture by its perimeter, multiplied by four. For instance, for a circular aperture, its equivalent diameter is equal to the diameter of the circle. The equivalent diameter at the aperture exit, defined as Dex, is the equivalent diameter of the apertures 6 at the aperture exit. In case the apertures 6 have different equivalent diameters, Dex is computed as the number-averaged equivalent diameter of the apertures 6 at the aperture exit. Beside Dex, the apertures 6 are also defined based on another parameter, namely the aperture ratio (Dr), which is the ratio between Dex and the critical diameter Dcrit. Notably, for the computation of Dr, the equivalent diameter of the apertures 6 at the exit (Dex) of the aperture towards the closed vessel 10 shall be considered (in fact, for tapered apertures, said diameter is not constant along the axis of the aperture). Specifically, in case of apertures 6 having different diameters, as disclosed before, the equivalent diameter (Dex) to be considered for the computation of the aperture ratio Dris the number-averaged equivalent diameter of the apertures. Critical diameter (Dcrit) of the distributor aperture 6 corresponds to the maximum diameter of the aperture 6 which, when the polymer melt feed passes through it, does lead to the formation of stable polymer strands within step (c). Therefore, Dcrit is linked with the formation of a stable polymer strand. Preferably, to ensure the production of deodorized recycled polyolefins according to the present process, Dr should be at most 1.0, preferably at most 0.8, even more preferably at most 0.7. In fact, it was found that when the Dex, as well as Dr of the apertures 6 was too large, polymer strands are hardly formed, as dripping or intermittent jetting can be observed instead. It was found that the dripping and intermittent jetting regimes are not as efficient as the melt strand regime in removing the odorous substances and, particularly, SVOCs, as it will be shown below in the examples. In detail, Dcrit is defined according to following equation (2) ^^^^^^^^^^ = 5.8 (2) wherein: - ^^ (kg / s) is the mass flow of the polymer melt feed flowing out of the apertures 6 divided by the number of apertures 6 (i.e. it is the average mass flow per aperture), - ^^ (kg / m3) is the density of polymer melt feed, calculated according to the following equation (3) ^^ =1073 exp(3) -= 9.8 is gravitational acceleration on Earth, - μ (Pa·s) is the dynamic viscosity, assumed to be the viscosity of the polymer melt feed at the temperature T (see below) at the inlet section 3 at shear rate of 15 s-1, - ^^ (kg / s2) is the surface tension of the polymer melt feed, calculated according to the following equation (4) ^^ = 0.0552 − 0.0000683 [^^−1] ∙ ^^ (4)- ^^ (K) is the temperature of the polymer melt feed at the inlet section 3. The dynamic viscosity μ can be measured, for instance with a capillary rheometer, or can be computed if a suitable model to compute dynamic viscosity is known (for instance, for a Cross-WLF model, see e.g. Peydró M.A., Parres F., Crespo J.E., Varón D.J. Study of rheological behavior during the recovery process of high impact polystyrene using cross-WLF model. J. Appl. Polym. Sci. 2010;120:2400–2410. doi: 10.1002 / app.33444.) In case the dynamic viscosity is measured with said capillary rheometer, as in the following Examples, the capillary measurements are performed using a Göttfert Rheograph 2002 with a 12 mm diameter barrel using a tungsten carbide capillary with length L=30 mm and diameter D=1mm (entry angle=90°). The attainment of a real steady state of the stress at each imposed shear rate was carefully checked. No thermal degradation at the temperatures investigated was observed inside the rheometer. Following step (c), the at least one formed polymer strand is let it drop into the closed vessel 10 within step (d) of the present process, thereby obtaining a deodorized polyolefins in closed vessel 10 and the removed vapours comprising, particularly, semi-volatile organic compounds (SVOCs) odoriferous substances. Indeed, the at least one aperture 6 is above the closed vessel 10 in such a way that passing through these apertures 6 within step (d), the polymer melt feed flows from the distributor 5 into the closed vessel 10 in the downward direction and in the form of polymer strands. Therefore, in step (d), the polymer strands drop by gravity inside the closed vessel 10. Optionally, the polymers strands, dropped into the closed vessel 10, form a polymer strand pool. In such a case the height of the polymer strands is lower, since the closed vessel 10 is filled with the deodorized polyolefins making the drop in step (d) from the aperture 6 to the closed vessel 10 shorter. This reduction of the height of the polymer strands, generally, reduces the efficacy of the decontamination / deodorization. With reference to Figure 2, it is shown a particular embodiment of an apparatus 20 used to carry out the process steps of the present invention, and that was used for the Examples. The apparatus 20 comprises elements, related to the melting of the recycled polyolefins feedstock prior to step (a) of the present process, and a specific deodorization device according to the deodorification device 1 of Figure 1. More in detail, polymer in solid state is fed to a hopper 14 of an extruder 15. The extruder comprises 4 zones (Z1, Z2, Z3 and Z4) of thermoregulation. An outlet 16 of the extruder 15 is flanged to a vertical SMX static mixer 17, heated at the target temperature by a thermal fluid regulation, that is aimed to homogenize the polymer temperature. The static mixer 17 is connected to the inlet section 3 of deodorization device 1. A temperature transmitter 4 located at the exit of the static mixer 17 measures the polymer melt temperature T. The polymer melt coming from the static mixer 17 is fed to the deodorization device 1. As shown in Figure 1, the deodorization device 1 comprises: - one inlet section 3, for receiving the polymer melt feed at a target temperature T; - one distributor 5 with one aperture 6. The distributor is connected to a closed vessel 10. The closed vessel 10 consists of two parts, a top part 18 and a bottom part 13, that are flanged each other. The closed vessel 10 is provided with: - a polymer outlet 12’; - at least one vapour outlet 8, where the pressure of the closed vessel 10 is measured by the pressure transmitter 2. In addition, the deodorization device 1 of Figure 2 further comprises: - a heating jacket 7 to ensure that the temperature of the deodorization device 1 is kept to the temperature T measured by temperature transmitter 4; - a polymer outlet 12’, located in the bottom part 13, corresponding to the polymer outlet 12 of Figure 1, and consisting in the receiving portion of the retractable spoon 11, which is able to collect the falling polymer strand; and - a sight glass 9, which allows the visual inspection of the falling polymer strand. According to the present invention, increasing the height of the strands does not always increase the efficacy of the treatment. This is because, depending on the viscosity and mass flow rate per aperture, the melt polymer strands become unstable and break. In particular, it was found that the minimum mass flow ratio ^^^^^^^^^^, defined as the ratio between the mass flow ^^ and the critical minimum mass flow rate ^^^^^^^^, prevents the polymer strand break up when its value is at least 1.0, preferably at least 1.2, even more preferably at least 1.3. Regarding to the mass flow (m), it was already defined in equation (2) as the mass flow of the polymer melt feed flowing out of the apertures 6 divided by the number of apertures 6. Specifically, the critical minimum mass flow ^^^^^^^^corresponds to the mass flow value below which the polymer strand breaks (due to excessive thinning and growth of capillary instability) and takes into account the height of the polymer strand. Therefore, the minimum mass flow ratio ^^^^^^^^^^is another parameter representing the deodorization efficiency, which needs to be considered for obtaining free- odor polyolefins within the present process. The critical minimum mass flow ^^^^^^^^is calculated according to the following equation 5: ) wherein: 4 - ^^ is a numeric constant having value equal to 3, - ^^ (kg / m3) is the density of polymer melt feed, calculated with equation (3) -^^ = 9.8^^ is the gravitational acceleration on Earth, - ^^ (Pa·s) is the dynamic viscosity, assumed to be the viscosity of the polymer melt feed at the temperature T at the inlet section 3 and at shear rate of 15 s-1, - ^^ (kg / s2) is the surface tension of the polymer melt feed, calculated with equation (4), - ^^ (m) is essentially the maximum length of the polymer strand. In regard to ^^ within equation (5), when there is the polymer strand pool inside the closed vessel 10, it is the maximum vertical-axis-projected distance (that is, the distance measured along the axis of gravity) between the exit of the apertures 6 and the underlying polymer strand pool. Therefore, in this case ^^ is the maximum difference between the height of the exit of the apertures 6 and the height of the polymer melt pool. However, when no polymer strand pool is present, or it is of unknown height (for instance, if the polymer strand pool height is not measured or its height cannot be estimated otherwise), ^^ is computed as the maximum vertical-axis-projected distance (that is, the distance measured along the axis of gravity) between the exit of the apertures 6 and polymer outlet 12 on the bottom of the closed vessel 10. This is a safe criterium as the allowed polymer mass flow range narrows. In some embodiments, the essentially maximum length of the polymer strand, H, is at most 5 m, preferably between 0.5 m and 4 m. Together with the ^^^^^^^^^^parameter, another parameter should be taken into account for improving the deodorization efficiency. This parameter is the maximum mass flow ratio ^^^^^^^^^^, defined as the ratio between the mass flow ^^ (as defined above, in equation (2)) and the critical maximum mass flow rate ^^^^^^^^. Specifically, the critical maximum mass flow ^^^^^^^^corresponds to the mass flow value above which the residence time, for the process conditions employed, is insufficient for removing the SVOCs odoriferous substances to values below the limits, where the limits are the values that would impart a sensible smell in the olefinic polymer. It turns out that also ^^^^^^^^^^is a parameter representing the decontamination efficiency of the present process, which preferably is at most 1.0, more preferably at most 0.8, even more preferably at most 0.7. The critical maximum mass flow ^^^^^^^^is calculated according to the following equation (6): ^^ −18 9.366 −75.4764 ^^^^^^ = 2 ∙ 10 ∙ ^^ ∙ ^^ ∙ exp [(0.088 − 2.945 ∙ 10 ∙ ^^^^2 −√^^^^ )−1] (6) wherein: - ^^ is essentially the maximum length of the polymer strand. All the above-reported considerations on ^^ regarding the presence or absence of the polymer strand pool are still valid; - ^^ (°C) is the polymer melt temperature at the inlet section 3; - ^^^^ (Da) is the value of the molecular weight of the SVOC odoriferous substance (ii) and, particularly, of the one having the highest molecular weight. In absence of specific information, the ^^^^ is set to the default value of 400 Da. Together with ^^^^^^and ^^^^^^^^^^, another essential parameter is the pressure inside the closed vessel 10, which needs to range from 1 to 8000 Pa (abs), preferably from 10 to 6000 Pa (abs), more preferably from 50 to 3500 Pa (abs), even more preferably from 100 to 2000 Pa (abs), still more preferably from 200 to 1500 Pa (abs). In regard to the closed vessel 10, where step (d) of the present process has occurred, it can be any apparatus, equipment or device that is able to contain a polymer strands and free-odor polyolefins, at the specified conditions of temperature and pressure. For instance, such closed vessel 10 can be made of metal, such as steel, especially stainless steels such as austenitic or duplex steels, aluminum, titanium, bronze and so on. The distributor 5 and the closed vessel 10 can be a single and integrated unit or can be two separated units. In any case, the apertures 6 of the distributor 5, where the polymer melt feed exits to form strands, shall reside in the closed vessel 10. If the distributor 5 is separated from the closed vessel 10, it can be fluidly located on the top of the closed vessel 10. Advantageously, in this way it is possible to produce the apertures 6 directly in the shell that closes the closed vessel 10 on the top. If the distributor 5 is integrated into the closed vessel 10, typically the closed vessel 10 has just at least one inlet for the polymer that is fluidly connected with said distributor, that typically resides completely at the interior of the closed vessel 10, in its top part. The shape of the closed vessel 10 is not particularly limited. For instance, it can be a cylindrical shaped shell, with flat or dished heads on the top or bottom. The ratio between the height and the closed vessel equivalent diameter ^^^^^^^^^^^^^^is not particularly limited to any range. For instance, it can be between 0.1 and 8, preferably between 0.2 and 5. The closed vessel 10 can be provided with devices and equipment, shown in Figure 2, which facilitate a smooth and efficient running such as sensors, such as sensor for measuring the polymer melt temperature 4, vessel pressure 2 and vessel level transmitters, and sight glasses 9 or cameras for inspection. Vessel pressure transmitter can be located also outside the closed vessel 10, for instance in the vapor outlet 8 or even in the condenser (if present) which recovers the condensable vapours, as long as the pressure drop is negligeable, and they are fluidly connected to the closed vessel 10. Vessel level transmitter can be of any type, such as differential ones (DP-cell type), radar-based, ultrasound- based or radiometric-based ones. Following step (d), the obtained deodorized polyolefins are recovered in step (e) of the present process by means of the at least one polymer outlet 12. For example, the at least one polymer outlet is an exit nozzle positioned at the bottom of the closed vessel 10. Alternatively, the deodorized polyolefins can be recovered by the retractable spoon 11 made, for example, in copper. This spoon can be inserted laterally on the bottom of the closed vessel 10. For example, the deodorized polyolefins are recovered in step (e) by means of a suitable device, such as a gear pump. Optionally, the recovered deodorized polyolefins can then be pelletized. Together with the recovering of the deodorized polyolefins within step (e), the removed vapours (comprising particularly semi-volatile organic compounds (SVOCs) odoriferous substances, but also water vapour and other gases) are also recovered in step (f) of the present process by means of the at least one vapor outlet 8, which is kept under vacuum by means, for example, of vacuum pumps or ejectors. The at least one vapor outlet 8 is also in communication with the closed vessel 10. Optionally, the recovered volatiles are condensed prior to pass through vacuum pump. There are no particular limitations on the condenser that can be used. For instance, the condenser can be a reflux condenser. When the condenser is used, the vacuum pump can be positioned on the duct removing the uncondensed gases. With or without condenser, there are no particular limitations on the type of vacuum pump that can be used. Both wet and dry vacuum pumps can be used. Example of vacuum pumps that can be used to the purpose include ejectors, liquid ring vacuum pump, rotary claw vacuum pump, rotary screw pumps, side channel blowers. Although a single polymer outlet 12 and vapor outlet 8 are drown in figure 1, it is intended that more vapour and polymer outlets can be provided. EXEMPLARY MODES OF CARRYING OUT THE TEACHING OF THE PRESENT DISCLOSURE Inventive and comparative examples are reported here by way of illustration and are not intended to limit the invention. COMPONENTS OF THE FEEDSTOCK The feedstock used for the Examples is not based on post-consumer recycled polyolefins, instead it has been prepared a surrogates-on-virgin polymer, following the Welle’s approach in Welle, F., Recycling 2023, 8, 26. https: / / doi.org / 10.3390 / recycling8010026. This approach has been adopted for the following reason: the feedstock based on post-consumer recycled polyolefins is very variable and, thus, the content of odorous substances is not constant. A first advantage of using a virgin polymer is that the resulting feedstock is homogeneous, therefore allowing high reproducibility and reliability of results. Secondly, using a virgin polymer it is possible to evaluate the performances of the deodorization of the selected SVOCs odoriferous substances. An extensive search was run to find the ideal surrogates, i.e. compounds that represent the semi-volatile organic compounds (SVOCs) odoriferous substances, and that, thus, will be called “surrogates” in the here below. Following this approach, instead of using actual feedstock based on post-consumer recycled polyolefins, deodorization tests were carried out on a virgin polyolefin based feedstock comprising a defined choice of SVOCs odoriferous substances in a defined quantity, that are used as model compounds. The selected surrogates have to satisfy the following criteria: - odoriferous compounds - extremely low odor detection threshold - Modified Kovats Index (MKI) comprised between 1300 and 2300 - found in post-consumer recycled (PCR) polyolefin-based feedstocks - not dangerous to handle (relatively good HSE profile). Lauric acid and phenyl acetic acid are indeed the selected surrogates. Lauric acid has molecular weight of 200.3 Da, a boiling temperature of 297.9°C, an olfactory threshold (from Daikoku et al., «Measuring odor threshold using a simplified olfactory measurement method», J. Human-Environment System, Vol. 21, No.1, 1-8, 2019) of 0.042 ppb, and a characteristic smell of laurel oil. Phenylacetic acid has molecular weight of 136 Da, a boiling temperature of 265.5°, an olfactory threshold (from Daikoku et al. as before) of 2.4·10-6ppb (that is, 2.4 parts per quadrillion, or 2.4 ppq), and a characteristic smell that makes it like honey. Both lauric acid and phenylacetic acid have a modified Kovats index (MKI) in the range from 1300 to 2300. In fact, the retention time, measured according to the same procedure done for n-C13 and n-C23 (see below), was found to be 5.7 minutes for phenyl acetic acid and 7.4 minutes for lauric acid. Therefore, MKIphenyl acetic acid=1422 and MKIlauric acid=1759. The presence of lauric acid and phenylacetic acid within the post-consumer polyolefin polymers is confirmed by Cabanes et al. The lauric acid and phenyl acetic acid were bought both from Merck (code W261416-1KG-K and code W287806-1KG-K respectively). POLYETHYLENE POLYMERS USED IN EXAMPLES (COMPARATIVE AND INVENTIVE) The virgin polyolefin based feedstocks that were chosen for this purpose were commercial polyethylene grades produced by Versalis, which are LDPE (low density polyethylene) having different MFR and densities: Table 1 MFR (190°C, Density Polymer grade 2.16kg) (@23°C) [’ / 10'] [kg / m3] Riblene FC 30 0.25 922 Riblene FL 30 I 2.3 923 Riblene GP 20 R 7 921 Riblene MR 10 R 22 919 ANALYTICAL TECHNIQUES USED FOR ANALYSING THE EXAMPLES Gas chromatography used to quantify the total concentration of semi-volatile organic compounds (SVOCs): Part A: determination of retention times of n-C13 and n-C23 Initially, the determination of the retention time of normal tridecane (n-C13, CAS number 629-50-5) and normal tricosane (n-C23, CAS number 638-67-5) was carried out as follows, by gas chromatography. A cyclohexane / isopropanol solution is prepared, in a 50 / 50 w / w mixture, containing 100 ppm of the additive (n- C13 / n-C23) and 100 ppm of methyl stearate. The solution thus obtained is analyzed through the GC TRACE GC ULTRA (THERMO) equipment, equipped with "on column" injector, flame ionization detector (FID detector), TRIPLUS- RSH (THERMO) autosampler. The following are the instrumental parameters used for the analysis: Capillary column: Stationary phase: Mega-lap® by Mega, length 30 m, inner diameter 0.32 mm, thickness 0.1 μm; Carrier gas: He, 1 ml / min, "constant flow" mode; Injector type: on column; Detector temperature: 320°C; Heating program: start at 80°C, increase to 17°C / min up to 320°C, isotherm at 320°C for 12 minutes; Injection volume: 1 μl. The retention time was found to be 5.177 minutes for n-C13 and 11.370 minutes for n-C23. Part B: determination of the total concentration of semi-volatile organic compounds (SVOCs) To measure the total concentration of semi-volatile organic compounds (SVOCs), about 3 grams of the sample are molded by die-casting in the form of a film with a thickness of about 500 microns and cut out in the form of squares of about 1 cm2of area. Approximately 1.5 grams of the sample (Ws) thus obtained are weighed and placed in contact with 15 mL of a 50 / 50 W / w cyclohexane / isopropyl alcohol mixture and 1 mL of an "internal standard solution". This "internal standard solution" consists of 100 mL of a 50 / 50 w / w cyclohexane / isopropyl alcohol solution and approximately 0.1 g of methyl stearate. Weight of internal standard (Wis) is defined as the weight in μg of the methyl stearate used. The resulting mixture is placed in a "Green Chem" container agitated for extraction using the MARS 6 (CEM) microwave extractor. The vessel is subjected to a thermal cycle consisting of a ramp from T0=25°C to T1=85°C in 5 minutes, subsequent isothermal step at T1 for 35 minutes and subsequent cooling to T0 in 15 minutes. The power provided by the extractor is 250 W. The sample thus obtained is filtered to separate traces of solid from the liquid phase and the latter is also analyzed through the GC TRACE GC ULTRA (THERMO) equipment, equipped with "on column" injector, flame ionization detector (FID detector), TRIPLUS RSH (THERMO) autosampler, according to the same instrumental parameters defined above. The total concentration x of semi-volatile organic compounds (SVOCs) in the sample, expressed in ppm, is then calculated by the following equation (7): (7) where: ^^^^ is the total area from the retention time of n-C13 to the retention time of n-C23 (i.e. from 5.177 minutes to 11.370 minutes), ^^^^^^^^^^is methyl stearate peak area (retention time 10.690 min), ^^^^^^ is the weight in μg of the methyl stearate used, ^^ is the response factor for the semi-volatile organic compounds (SVOCs) odoriferous substances, that was set to 1.0^^^^ is the weight in g of the sample. To be noted that ^^^^ −^^^^^^^^^^is therefore the total area from compounds having modified Kovats index (MKI) from 1300 to 2300, after subtraction of the contribute of the added internal standard. Sensory panel test The material obtained from the Inventive Examples was a solid skein similar to a yarn ball produced by a very thin polymer filament. To evaluate the material produced in the Inventive Examples with the sensory panel test, the same surface to volume ratio of the granules obtained with the Comparative Examples and the untreated FC30 granules should be produced. To this task, said solid skeins were cooled in liquid nitrogen and milled with a commercial rotary blade miller (Retschmühle model SM1 nr 59300, power 1.5kW, 380V 50hz), using a mesh classifier having square apertures of 4 by 4 mm. The granules obtained in the reference, Comparative and Inventive Examples were evaluated by means of sensory panel test. The test was inspired by the "Guidelines for the Selection and Training of Sensory Panel Members," ASTM Publication No. 758, and "Manual on Sensory Testing Methods", ASTM Special Technical Publication No. 434; American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103. The sensory apparatus comprised a sensory evaluation room, that was a room equipped with a table and comfortable chairs, free of noise and odors. The samples were the polyolefin-based granules obtained by all the references, Comparative and Inventive Examples, contained in Schott jars of 250 ml capacity, capped with odor-free lids. Each jar was labelled with a number, that was randomly associated with the Examples, this number having three digits (i.e., number 183 could be associated to the material of Example 18, number 752 with the material of Example 3 etc.). Associations were not known to the members of the panel. A sheet was provided, where each member of the panel wrote, for each jar, the jar label number and the evaluation of the odor, expressed with an integer number from 0 to 5, expressing the intensity of the odor. The Rosenberg scale was chosen, with the following values: 0 = no odor; 1 = barely perceptible smell; 2 = light odor; 3 = moderate odor; 4 = strong odor; 5 = very strong odor. Several measures were adopted to minimize the intrinsic subjectivity of the method, in particular: - All the panel members were screened to have good and comparable sensitivity by n-butanol screening (using a simplified EN13725 sensitivity test). - All the people were non-smokers. - All jars were filled with the same quantity of material (100g) and kept closed in the refrigerator. The jar preparation procedure was as follows: 6 hours before the test, samples are taken from the refrigerator. The full cap is removed and replaced by a pad in PTFE (Teflon®) which has a hole of the same diameter of the straw that was used for the odor sampling. The jar is therefore closed again with the full cap. The transparent part of the bottle is then lined with aluminum foil so as not to affect the evaluator with the appearance of the jar content. The samples are numbered according to the randomized three digit numbers previously described. The jars are left at ambient temperature till the panel test measurements, to achieve thermal equilibrium with the environment and thus homogenize smell development. Half an hour before the start of the panel test in each of the bottles, a 15 cm long straw is inserted through the hole of the Teflon disk, so that the straw penetrates up to half of the product level. This is because the protruding part is marked at 4 cm from the end that is brought to the level of a Teflon disk. The whole bottle is then blocked with a perforated cap. For each evaluator, the bottles were placed on the table in a randomized order. A 35 ml syringe is then placed in front of each bottle, bearing a label with the same initials of the sample, and a 3-4 cm piece of "disposable" tube. The syringes are then "screwed": for each syringe and each jar, the syringe was inserted into the protruding piece of the tube, then a technician sucks and blows back from the jar three times by means of the syringe. Figure 3 shows a sketch of the bottle with the straw and syringe. Execution of the panel test assessment: each panel member (evaluator) received a sheet with the ordered list of the samples that they will use to express their evaluations. The sheet contained a grid with 4 boxes per sample, 3 for immediate evaluations and one for the final evaluation. Each evaluator, accompanied only by a tutor explaining the procedure, evaluated the samples according to the order in which they are placed on the table, from left to right, the same order in which they are listed on the form that has been given to her / him. For each sample, the procedure was as follows: A) The evaluator had to insert the syringe into the tube protruding from the cap and withdraw 30 cm3of gas; then the evaluator had to detach the syringe from the tube, take the disposable tube and insert it into the syringe. B) The evaluator had to hold the disposable tube close to her / his nose, press the plunger of the syringe at roughly constant speed and smell the gas. C) The evaluator had to put the disposable tube back next to the bottle and make a note on the sheet with the "immediate" assessment. D) The evaluator had to place the syringe near the corresponding bottle for optional subsequent re-evaluations and then had to move on to the next sample. In the event that the evaluator deemed necessary to re- evaluate one or more samples, the corresponding syringe and the same disposable tube were reused, for a maximum of three tests per sample. If the evaluator had the impression of having olfactory saturation, i.e. the smell of the sample was kept in the nostrils, he / she was asked to do an "olfactory reset" by sniffing, with the same procedure, coffee powder. At the end of all evaluations, each evaluator reported her / his final evaluation in the last column of the evaluation sheet and delivered the evaluation form to the tutor who collected the evaluations for subsequent data analysis. CONSIDERATION ABOUT THE CONCENTRATION OF SVOCS ODORIFEROUS SUBSTANCES In order to determine precisely the concentration of SVOC odoriferous substances and the effectiveness of the deodorization process, the granules of commercial polyethylene grades of Table 1 were subjected to extensive degassing process (ventilated oven, 30 days at 70°C) in order to limit as much as possible, the quantity of SVOCs present in the virgin polymer. By using the analytical technique to measure the total concentration of semi-volatile organic compounds (SVOCs) by Gas Chromatography, it has been verified that the concentration of the SVOCs in the treated virgin polymer is below the detection limit (<50 wppm). As a result, when the compositions of virgin polymer and the surrogates (phenyl acetic acid and lauric acid) are prepared (see below) it can be assumed that the total concentration of semi-volatile organic compounds (SVOCs) corresponds to the total concentration of semi-volatile organic compounds (SVOCs) odoriferous substances. EXAMPLES 1-4: PREPARATION OF THE SURROGATED-SPIKED POLYMERS – CONCENTRATED AND DILUTED BASES The chosen surrogates have relatively low melting point (the highest is phenyl acetic acid, having melting point of 76.5°C). Therefore, it was chosen to mix the surrogates in the liquid state. It was also chosen to prepare surrogated-spiked polymers having only one surrogate at a time. Two types of surrogated-spiked polymers have been prepared: concentrated bases (Examples 1 and 2) and diluted bases (Examples 3 and 4), which are listed in Table 2. The concentrated bases were used for two tasks: - to carry out experiments on deodorization treatment according to the present invention, in comparison with the standard treatment known in the art for this task (degassing extruder), and - to prepare diluted bases for further comparison of the deodorization treatment according to the present invention compared with the degassing extruder. On the other hand, the diluted bases were prepared to test the effectiveness of the process of the present invention also for diluted quantities. Tests carried out at high concentration of surrogates can be considered more challenging as the final concentration is higher, and therefore the odor issues are more critical. However, as the theory involves very complex physical phenomena, it was decided to verify the efficacy of the process also at lower concentration of surrogates. In regard to the concentrated bases, 8600 parts of lauric acid (Examples 1) and 6100 parts of phenylacetic acid (Example 2) were put in a container, and then brought to 85°C by heating while mixing with a magnetic bar. The chosen parts of extensively degassed (ventilated oven, 30 days at 70°C) polyethylene LDPE (see Table 2) were brought to 85°C in a ventilated oven for at least 4 hours. A 4 liters rotary evaporator (Rotavapor® by Buchi), that has a thermal control unit that can be set precisely to the required temperature and that ensures that the content of the rotary flask is kept at the same temperature was used to mix the polymer to the surrogates. The thermal control unit of the Rotavapor was pre-heated at 85°C, while the rotation speed was set to 20 rpm. The vapor outlet was closed so as to try to avoid loss of surrogates by evaporation. The rotary evaporator flask was loaded up to about 60% of its volume with the polyethylene LDPE and then the surrogate was added. Care was taken to preserve the temperature of both polymer and surrogate before the loading to the evaporator flask. Therefore, both polymer and surrogate were taken immediately from the oven and the heated container respectively to preserve the temperature. After 2 hours, the thermal control unit was cooled and waited till the temperature reduced to 30°C. For each base, the above-mentioned operations were repeated 4 times to prepare enough material for subsequent operations. Following Welle (Welle, F., Recycling 2023, 8, 26. https: / / doi.org / 10.3390 / recycling8010026), extrusion was carried out to mix the surrogate to the polymer in the melt state, so as to homogenize it (instead of having the surrogate only on the surface). To this task, the composition prepared in the Rotavapor was fed to the hopper of a twin-screw extruder (Baker Perkins, model MPC / V30, 1985). The screw diameter D was 30mm and the length to diameter ratio (L / D) was 16. The degassing vent was located at about 11 diameters from the hopper. The extruder was operated with the degassing vent closed speed 200 rpm, and with a temperature profile of 175°C in the first heating zone, 185°C in the second and 190°C in the third and fourth heating zones, flow rate 5 kg / hr. The extruder was connected with a die having a single 3 mm diameter hole. The polymer melt coming out from the die was immediately cooled by immersion in cold water and granulated. Then, the collected granules were put in a dry mixer for further homogenization, for 20 minutes, followed by a new extrusion in the same twin-screw extruder with the same conditions. The material coming out of the extruder was then collected in an airtight sealed glass container and placed in a refrigerated environment for 24 hours at 5°C. A gas chromatography analysis (as detailed above) was carried out over concentrated bases and the results are listed in Table 2. It can be seen that the lost quantity of surrogates was negligible. Phenyl acetic acid can be lost more easily both because of the higher vapor pressure and higher melting point (a small part of the surrogate could be crystallized on the hopper of the extruder, dry blender, and in general on relatively cold surfaces). Once the concentrated bases (Examples 1 and 2) have been prepared, a part of these materials was used to prepare the diluted bases (Examples 3 and 4). Indeed, since it is difficult to add and mix thoroughly very low quantities of an additive in a large quantity of polymer, it was decided that the method of dilution was more effective. The dilution ratio was defined to be 1:0.075 (see Table 2) so that the quantity of the surrogate in the diluted bases was 7.5wt% of the quantity of the corresponding surrogate in the concentrated base. 925000 parts of FC30 were carefully mixed to 75000 parts of the material obtained from Example 1 (for Example 3) and 2 (for Example 4) in a dry blender. The so-obtained mixture was fed to a twin-screw extruder, Baker Perkins, model MPC / V30 (1985) and processed as per Examples 1 and 2 (without degassing, speed 200 rpm, temperature 175-185-190- 190°C, flow rate 5 kg / hr, die hole 3mm). The polymer melt coming out from the die was immediately cooled by immersion in cold water and granulated, collected, refrigerated, homogenized in dry-blend, re-extruded in the same condition, and again collected and refrigerated, following exactly the same procedure already used for Example 1 and 2 (except for the initial preparation). As for the concentrated bases, also diluted bases were analysed by GC and the results, in terms of total concentration of SVOCs odoriferous substances as determined by the method disclosed before, are reported in Table 2. Again, analytical results closely approach the computed ones. Table 2 Lauric Ph.ac. Conc. Conc. Ex. Type FC30 a. a. Ex.1 Ex.2 (computed) (analysis) [parts] [parts] [parts] [parts] [parts] [wppm] [wppm] Ex.1 Concen. 991400 8600 - - - 8600 8602 Ex. 2 Concen. 993900 - 6100 - - 6100 6004 Ex.3 Diluted 925000 - - 75000 - 645.2 649 Ex.4 Diluted 925000 - - - 75000 450.3 436 Lauric a. = lauric acid Ph.ac a. = phenylacetic acid Concen. = concentrated base Notably, the viscosity of the polymer of Examples 1 to 4 and the one of the virgin FC 30 polymer resulted to be substantially the same. In particular, it resulted to be 2934 Pa.s at 15 [s-1] and 210°C, and 2370 Pa.s at 15 [s-1] and 230°C. INVENTIVE EXAMPLES 5-20: PREPARATION OF THE DEODORIZED POLYOLEFIN ACCORDING TO THE INVENTION The apparatus used for the Inventive Examples 5-20 is depicted in Figure 2. The surrogates-on-virgin polymer feedstocks, prepared as described in Examples 1-4, were provided as required by step (a) of the present process. The surrogates-on-virgin polymer feedstock underwent pre-treatments steps. Firstly, it was fed to a single-screw extruder (model TR12 / 240M, 1992), having screw diameter 12 mm and L / D=24, produced by Gimac at Castronno (Italy), and mounted vertically (the material flowing from top to bottom). The temperature profile on the extruder was 170° on the first zone (Z1) while the other three zones (Z2, Z3, Z4) were set to the target temperature as per the following table. The revolutions per minute, RPM, were modulated so as to ensure a constant mass flow as per the following table. The extruder was equipped with a pressure transmitter and a valve that could be used to regulate the die pressure. The extruder outlet was flanged to a vertical SMX static mixer, heated at the target temperature by a thermal fluid regulation, that was aimed to homogenize the polymer temperature. The static mixer was connected to the inlet section 3 of deodorization device 1. A temperature transmitter located at the exit of the static mixer measured the polymer melt temperature to ensure that the actual polymer melt temperature corresponded to said target temperature + / - 3°C. According to step (b), the melt surrogates-on-virgin polymer was fed to the deodorization device 1, which was a AISI 304L steel thick circular tube (3’’ MPS80 sch.80S, length 95cm). The deodorization device 1 comprised vertical positioned sight glass, which allowed the visual inspection of the falling polymer strand over almost the entire length of the closed vessel 10. In particular, a flashlight illuminated the sight glass so that the breakup events of the polymer strand could be detected and tracked. The deodorization device 1 comprised a heating jacket where silicon oil thermal fluid was flowing to ensure that the temperature of the deodorization device 1 was kept to the same target temperature used in the extruder. On the top of the deodorization device 1, an inlet section 3, in the form of a threaded tube, was connected with the static mixing for receiving the melt surrogates-on- virgin polymer. Further, the deodorization device 1 comprised a distributor 5, which was connected with the inlet section 3. The distributor 5 has one aperture 6. According to step (c), the melt surrogates-on-virgin polymer was passed through this aperture 6, and, thus, a polymer strand was formed. This polymer strand was then let drop into the closed vessel 10 (step (d)), obtaining a deodorized polymer. According to step (e), the deodorized polymer is recovered with the retractable spoon made in copper, positioned in correspondence with the bottom of the closed vessel 10. The vertical distance between the receiving portion 12’ of the retractable spoon 11 and the surrogates- on-virgin polymer exiting from the distributor aperture 6 was 83 cm. Such retractable spoon 11, when fully inserted in the closed vessel 10, was located centrally and aligned to the distributor 5, and therefore received the polymer strand which was falling from the aperture 6. At the start and at the end of the test, the spoon was fully retracted, so that the polymer strands dropping from the aperture were not recovered on the spoon but on the bottom 13 of the closed vessel 10. In such a way, the spoon was fully inserted only when operating conditions were stable and to the set values. After recovering the sample (few grams) on 12’, the spoon was immediately fully retracted. Before collecting the sample, the spoon was retracted and kept cold by applying ice on the part of the spoon which stayed outside the closed vessel 10. Copper ensured good thermal transmission to the part of the spoon used for the collection of the polymer strand 12’, so as to quickly cool the polymer strand (when collecting it), ensuring that deodorization could not continue once the polymer strand reached the spoon. In such a way, the deodorization was carried out only on the melt polymer dropping from the aperture 6 to the receiving part 12’ of the spoon 11. In parallel to the recovery of the deodorized polymer, the removed vapors (SVOCs odoriferous substances and other gases) were also recovered through the vapor output 8. To this task, the vacuum system connected to vapor output consisted in: - a two-staged vacuum pump, Edwards model E2M18, which had volumetric flow rate of 18 m3 / h. The maximum attainable pressure was 1 mBar (abs) in the closed vessel 10. - a piezoelectric vacuum meter, MKS model BARATRON 127A, measuring pressures from 0.1 to 1000 mBar(abs), with absolute error of 0.15%, read on the digital indicator MKS model PR-2000, located in close proximity of the closed vessel 10. - a butterfly valve located on the vacuum pump inlet, controlled by the regulator MKS model 252A. - a condenser to condense condensable gases, required to reduce the contamination of the oil of the pump, operated at -30°C by means of thermoregulating control unit HAAKE model 001-0385. A specifically built gasket ensured full tightness so that full vacuum could be applied to the closed vessel 10. After collection of sample, the extruder and vacuum pump were stopped, the flange between an upper part 18 and bottom part 13 of the closed vessel 10, shown in figure 2, was opened and the material collected on the receiving part 12’ of the spoon 11 was immediately recovered and refrigerated at 5°C. Mass flow rate was computed by dividing the polymer mass recovered on the spoon by the time the spoon was inserted. To summarize, the main operating conditions were: - Closed vessel pressure: 10 mBar(a), - Mass flow rate of the polymer per aperture (single aperture, therefore it was equal to the mass flow rate of the polymer in the extruder. Computed by mass balance): 40 and 90 g / h, - Aperture: 1.0 mm diameter cylindrical hole, hole thickness: 4mm, - Polyolefin melt temperature (at the inlet of the distributor in the closed vessel): 210 and 230°C. COMPARATIVE EXAMPLES 21-28: PREPARATION OF THE DEODORIZED POLYOLEFINS ACCORDING TO A COMPARATIVE PROCESS To evaluate the efficacy of the process of the present invention compared with the processes known in the art, it was carried out experimentation on the same inlet materials (from Examples 1 to 4), treated at the same temperature (210- 230°C) in a degassing twin-screw extruder. In fact, twin- screw extrusion is more effective than single screw extrusion; moreover, it was considered that the degassing extruder would be the process that the expert of the art would consider to deodorize the polyolefin-based PCR feedstocks, as most processes in the art propose setups based on degassing extruders. Materials from Example 1 to 4 were processed in the same twin-screw extruder already used to prepare the reference materials 1 to 4 (Baker Perkins, model MPC / V30 (1985)) and same die plate (single hole, 3mm diameter). Mass flow rate was 4 kg / h, speed 180 rpm, temperature profile 175°C in the first zone (hopper) and the target temperature (210 or 230°C) in all other heating zones. For these Examples, the degassing vent was opened. The degassing system comprised the same two-staged vacuum pump, Edwards model E2M18 and the piezoelectric vacuum meter MKS model BARATRON 127A, both already previously described. The pressure that was measured was 10 mbar(a). The polymer melt coming out from the die was immediately cooled by immersion in cold water and granulated, collected, refrigerated, homogenized in dry-blend and again refrigerated. Refrigeration was the same of previous Examples 1-4. In this way, Comparative Examples 21-28 have been prepared and analysed. EVALUATION OF THE CRITICAL PARAMETERS OF THE DEODORIZED POLYMERS ACCORDING TO THE INVENTION Table 3 shows the process parameters (polymer melt temperature T, mass flow per aperture m, pressure of the closed vessel, the viscosity of the polymer, aperture equivalent diameter Dex) and the computation of specific parameters (mrmin, mrmax and Dr) and whether the computed parameters fall in the defined ranges. The selection of the process parameters led to the definition of 4 process conditions (condition A, condition B, condition C and condition D). Cautiously, mrmax has been computed using the molecular weight MW=400 (the value to be used in absence of specific information, see definition of mmax) Table 3 CONDITION A CONDITION B CONDITION C CONDITION D Polymer grade [-] FC 30 FC 30 FC 30 FC 30 H [m] 0.8 0.8 0.8 0.8 Dex [mm] 1 1 1 1 [Pa.s] ^^ @ 15 [s-1] 2934 2934 2370 2370 T [°C] 210 210 230 230 M [g / h / apert] 40 90 40 90 Dcrit [mm] 6.20E+00 1.22E+01 6.28E+00 1.23E+01 mmin[g / h / apert] 4.72E+00 4.72E+00 6.28E+00 6.28E+00 mmax [g / h / apert] 1.23E+02 1.23E+02 2.88E+02 2.88E+02 Dr[-] 1.61E-01 8.20E-02 1.59E-01 8.11E-02 mrmin [-] 8.47E+00 1.91E+01 6.37E+00 1.43E+01 mrmax[-] 3.25E-01 7.32E-01 1.39E-01 3.12E-01 Dr <= 1 ? [+ / -] + + + + mrmin>= 1 ? [+ / -] + + + + mrmax <= 1 ? [+ / -] + + + + TESTS FOR EVALUATION OF SVOCS REMOVAL EFFICIENCY The Inventive examples and the Comparative examples were analysed by means of two techniques: gas chromatography and sensory panel test (see the section “ANALYTICAL TECHNIQUES USED FOR ANALYSING THE EXAMPLES” above). Table 4 shows the results for the Inventive Examples (5-20) and for the Comparative Examples (21-28), wherein the total initial concentration and the total final concentration of the semi-volatile organic compounds (SVOCs) odoriferous substances were obtained via gas chromatography. Notably, Examples and Comparative Examples are grouped by same material treated (Examples 1 to 4) and same polymer melt temperature (210 and 230°C). The SVOCs odoriferous substances (that corresponds to SVOCs, as explained before) removal efficiency is given by the following equation (10): Since the detection limit was about 50 wppm for both surrogates, for the Inventive Examples where the concentration of the surrogates within deodorized polymers was under the detection limits, the final concentration is reported “< 50” wppm. It follows that equation (11) (11) Table 4 Flow rate per SVOC Inlet aperture Initial removal Example material T (*) Surrogate conc. Final conc. efficiency [°C] [g / h] [wppm] [wppm] [%] Inv.5 Ex.1 210 40 Lauric a. 8602 815 90.53% Inv.6 Ex.1 210 90 Lauric a. 8602 1354 84.26% Comp. 21 Ex.1 210 - Lauric a. 8602 6981 18.84% Inv.7 Ex.1 230 40 Lauric a. 8602 360 95.81% Inv.8 Ex.1 230 90 Lauric a. 8602 803 90.66% Comp. 22 Ex.1 230 - Lauric a. 8602 6019 30.03% Inv.9 Ex.3 210 40 Lauric a. 649 <50 >92.3% Inv.10 Ex.3 210 90 Lauric a. 649 <50 >92.3% Comp. 23 Ex.3 210 - Lauric a. 649 413 36.36% Inv.11 Ex.3 230 40 Lauric a. 649 <50 >92.3% Inv.12 Ex.3 230 90 Lauric a. 649 <50 >92.3% Comp. 24 Ex.3 230 - Lauric a. 649 378 41.76% Inv.13 Ex.2 210 40 Ph.ac. a. 6004 <50 >99.17% Inv.14 Ex.2 210 90 Ph.ac. a. 6004 <50 >99.17% Comp. 25 Ex.2 210 - Ph.ac. a. 6004 3267 45.59% Inv.15 Ex.2 230 40 Ph.ac. a. 6004 <50 >99.17% Inv.16 Ex.2 230 90 Ph.ac. a. 6004 <50 >99.17% Comp. 26 Ex.2 230 - Ph.ac. a. 6004 3093 48.48% Flow rate per SVOC Inlet aperture Initial removal Example material T (*) Surrogate conc. Final conc. efficiency Inv.17 Ex.4 210 40 Ph.ac. a. 436 <50 >88.53% Inv.18 Ex.4 210 90 Ph.ac. a. 436 <50 >88.53% Comp. 27 Ex.4 210 - Ph.ac. a. 436 319 26.83% Inv.19 Ex.4 230 40 Ph.ac. a. 436 <50 >88.53% Inv.20 Ex.4 230 90 Ph.ac. a. 436 <50 >88.53% Comp. 28 Ex.4 230 - Ph.ac. a. 436 308 29.36% (*) parameter not defined for degassing extruder (Examples 21-28). None of the Inventive Examples from 5 to 20 showed the break-up of the polymer strand (as detected by means of the sight glass and tracked by the operator) EXAMPLE 29-31 Example 1 was repeated but using the polymers as in the following table 5: Table 5 Polymer Lauric Ph.ac. Conc. Conc. Ex. grade LDPE a. a. (computed) (analysis) [parts] [parts] [parts] [wppm] [wppm] Ex.29 FL 30 I 991400 8600 - 8600 8620 Ex.30 GP 20 R 991400 8600 - 8600 8550 Ex.31 MR 10 R 991400 8600 - 8600 8650 Notably, the viscosity of the polymers of Examples 29 to 31 and the one of the corresponding virgin polymers resulted to be substantially the same. In particular, it resulted to be 1150 Pa.s at 15 [s-1] and 210°C for Example 29, 640 Pa.s at 15 [s-1] and 210°C for Example 30, 110 Pa.s at 15 [s-1] and 210°C for Example 31. EVALUATION OF THE CRITICAL PARAMETERS OF THE DEODORIZED POLYEMRS ACCORDING TO THE INVENTION Table 6 shows the process parameters and the computation of specific parameters (mrmin, mrmax and Dr) and whether the computed parameters fall in the required range. The selection of the process parameters led to the definition of 3 process conditions (condition E, condition F, condition Table 6 CONDITION E CONDITION F CONDITION G Polymer grade[-]FL 30 I GP 20 R MR 10 R H [m] 0.8 0.8 0.8 Dex[mm]1 1 1[Pa.s] ^^ @ 15 [s-1] 1150 640 110 T[°C]210 210 210 m[g / h / apert]40 90 90Dcrit[mm]5.31E+00 9.46E+00 7.05E+00 mmin[g / h / apert]3.07E+01 9.92E+01 3.36E+03 mmax[g / h / apert]1.23E+02 1.23E+02 1.23E+02 Dr[-]1.88E-01 1.06E-01 1.42E-01 mrmin[-]1.30E+00 9.07E-01 2.68E-02 mrmax[-]3.25E-01 7.32E-01 7.32E-01 Dr≤1 ?[+ / -]+ + + mrmin≥1 ?[+ / -]+ - - mrmax≥1 ?[+ / -]+ + + TESTS FOR EVALUATION OF SVOCS REMOVAL EFFICIENCY Inventive and comparative Examples 32-34 were prepared following the conditions from E to G on the materials prepared with Examples 29-31. Table 7 shows the corresponding results. Table 7 SVOC Inlet Flow Initial removal Example material T rate Surrogate conc. Final conc. efficiency [°C] [g / h] [wppm] [wppm] [%] Inv.32 Ex.29 210 40 Lauric a. 8650 863 90.02% Comp.33 Ex.30 210 90 Lauric a. 8550 Untestable - Comp.34 Ex.31 210 90 Lauric a. 8620 Untestable - Comparative Examples 33 and 34 showed extensive break- up of the polymer strand (as detected by means of the sight glass and tracked by the operator), resulting in not homogeneous material. Therefore, the analysis of lauric acid concentration was not undertaken as it would be meaningless. GENERAL REMARKS ON ALL THE EXAMPLES It can be seen that, in any condition and for any inlet material, the process according to the present invention is quite more efficient in removing the added surrogate. Both lauric acid and phenyl acetic acid are removed far more efficiently, even though the improvement on phenylacetic acid is particularly remarkable (from a little more than 40% to over 99%). In all the Inventive Examples, which are according to the present invention, the SVOCs removal efficiency is very high (more than 80%-90% for lauric acid, even more for phenylacetic acid). The efficiency was higher at lower mass flow rate per aperture. However, surprisingly the process according to the invention keeps very efficient even at very high flow rates (90 g / h per aperture). As expected, the efficiency of removal of lauric acid is higher when the initial content of the surrogate was lower, at the point that in all Examples 9-12 treating diluted lauric acid (from Example 3), the value of lauric acid was below detection limit, therefore having a SVOC removal efficiency higher than 100%-50 / 649=92.3%. The efficiency in the removal of phenylacetic acid was even higher. As all Inventive Examples fed with phenylacetic surrogate resulted in a residual value of the surrogate below the detection limit, even starting at 6004 wppm, it is reasonable to assume that the real quantity of phenyl acetic acid was quite lower than the detection limit, especially for Examples from 17 to 20 that started from Example 4 having surrogate concentration of 436 wppm, as it can be inferred that, as per the lauric acid, the SVOCs removal efficiency is higher at lower initial surrogate concentration. Therefore, the true SVOCs removal efficiency for phenyl acetic acid can be assumed to be larger than 99% in all conditions. Comparative Examples 33 and 34, compared with the Examples of the invention (in particular Inventive Example 32) show that the polymer strand produced with the process conditions according to the invention exhibited stability and therefore a homogeneous final product with high SVOC removal, while stability was not obtained when working outside of said process conditions. TESTS FOR EVALUATION OF DEODORIZATION EFFECTIVENESS As above-mentioned, the effectiveness of the process according to the invention has been validated also with the olfactometry panel test, whose results are reported in Table 8. Table 8 also reports the results of the Comparative Examples (21-28) for being compared with the Inventive Examples (5-20 and 31). Table 8 Inlet Flow Odor Example material T rate Surrogate strength std.dev. [°C] [g / h] [wppm] [wppm] FC 30 - - - 1.5 0.8 FL 30 I - - - 1.3 0.8 GP 20 R - - - 1.5 1.0 MR 10 R - - - 1.6 0.7 e.d. (*) FC 30 + 1 (RIF) lauric a. - - Lauric a. 4.4 0.5 e.d. FC 30 + 2 (RIF) Ph.ac. a. - - Ph.ac. a. 5.0 0.0 e.d. FC 30 + 3 (RIF) lauric a. - - Lauric a. 3.4 0.7 e.d. FC 30 + 4 (RIF) Ph.ac. a. - - Ph.ac. a. 4.9 0.3 5 Ex.1 210 40 Lauric a. 3.7 0.8 6 Ex.1 210 90 Lauric a. 3.9 0.6 21 (*) Ex.1 210 - Lauric a. 4.2 0.6 7 Ex.1 230 40 Lauric a. 3.1 0.7 8 Ex.1 230 90 Lauric a. 3.4 0.7 22 (*) Ex.1 230 - Lauric a. 4.1 0.6 9 Ex.3 210 40 Lauric a. 1.8 0.6 10 Ex.3 210 90 Lauric a. 2.1 1.2 Inlet Flow Odor Example material T rate Surrogate strength std.dev. 23 (*) Ex.3 210 - Lauric a. 3.1 0.8 11 Ex.3 230 40 Lauric a. 1.4 1.0 12 Ex.3 230 90 Lauric a. 1.6 0.7 24 (*) Ex.3 230 - Lauric a. 3.0 0.7 13 Ex.2 210 40 Ph.ac. a. 2.0 0.8 14 Ex.2 210 90 Ph.ac. a. 2.1 0.6 25 (*) Ex.2 210 - Ph.ac. a. 4.8 0.4 15 Ex.2 230 40 Ph.ac. a. 2.1 0.6 16 Ex.2 230 90 Ph.ac. a. 1.9 0.7 26 (*) Ex.2 230 - Ph.ac. a. 4.7 0.5 17 Ex.4 210 40 Ph.ac. a. 1.7 0.7 18 Ex.4 210 90 Ph.ac. a. 1.9 0.7 27 (*) Ex.4 210 - Ph.ac. a. 4.4 0.5 19 Ex.4 230 40 Ph.ac. a. 1.8 0.8 20 Ex.4 230 90 Ph.ac. a. 1.8 0.6 28 (*) Ex.4 230 - Ph.ac. a. 4.3 0.7 e.d. FL 30 I + lauric 29 (RIF) a. - - Lauric a. 4.4 0.7 e.d. GP 20 R + 30 (RIF) lauric a. - - Lauric a. 4.3 0.7 e.d. MR 10R + 31 (RIF) lauric a. - - Lauric a. 4.5 0.5 Inv.32 Ex.29 210 40 Lauric a. 3.5 1.0 Comp.33 Ex.30 210 90 Lauric a. Untestable Untestable Comp.34 Ex.31 210 90 Lauric a. Untestable Untestable (*) by “e.d.” is meant “extensively degassed”, 30 days at 70°C, as described before. The following observations can be made: 1) Phenyl acetic acid was reported to impart a very persistent and unpleasant odor, despite it was reported in scientific literature that it had a honey smell. 2) Even at relatively low concentration (e.g. even the diluted reference, Example 4, as well as all the Comparative Examples produced by the degassing extruder) the samples with phenylacetic acid were reported to have a very strong smell, to the point that in some cases the test had to be interrupted because the odor filled the nostrils. 3) Surprisingly, the materials treated with the process of the present invention (namely Inventive Examples) showed a so lower value of phenylacetic acid (maybe well below detection limit) that the odor reduced drastically, to a point that showed almost the same odor intensity of the uncontaminated FC30. 4) Lauric acid treated material was reported to have a pleasant, “soap bar” odor, less strong than phenylacetic acid treated material. Differently from phenylacetic acid, the materials having a dilute quantity of lauric acid show progressively a slighter odor. 5) With reference to lauric acid, as per phenylacetic acid, while the corresponding Comparative Examples showed to keep a significant odor, the ones treated with the process according to the present invention (namely Inventive Examples) showed reduced odor down to only light / negligible odor for the diluted samples. 6) Polyolefins with higher MFR than FC30 can be processed according to the present invention, obtaining stable strands and good deodorization. Oppositely, polyolefins with even higher MFR, if treated with process conditions outside the ranges of the present invention, cannot be processed forming stable strands. 7) As the actual polyolefin-based PCR feedstocks generally contains much lower quantities of odoriferous SVOCs than the quantities used in the present Examples (1, 2, 3, 4 and 29), it can be concluded that the process of the present invention would be as effective in removing odors for such PCR feedstock as it was in such Inventive Examples, to the point that in some cases the reported odor strength is indistinguishable from the virgin polyolefins (FC30). COMPARATIVE EXAMPLE 35 Comparative Example 35 corresponds to Example 8 of the international patent applications WO 2023 / 001854 and WO 2023 / 001855. According to this Example 8, "residual styrene” is removed from a stream of polyethylene. It is unclear how this can be possible, since polyethylene production does not include styrene either as a monomer or solvent. Therefore, its reproducibility is also doubtful. However, in Comparative Example 35 it was supposed that polyethylene of Example 8 was mixed with some “residual styrene” and tested in a devolatilization apparatus having strands drop height 6 meters. In details, the data of Comparison Example 35 are the following: Material: polyethylene, high density Mass flow per aperture: 20 g / h / aperture Viscosity at the inlet part at 10 s-1: 4100 Pa.s Equivalent diameter at the exit: 1.2mm Temperature at the inlet part: 260°C Drop height: 6 m Inlet residual styrene: 1350 wppm Outlet residual styrene: 75 wppm Modified Kovats Index (MKI) of styrene: 844.8 (so according to the definition given in the present Invention, it is not a SVOC) Molecular weight of styrene: 104 kg / kmolBoiling point of styrene at 0.1 bar(a): 75°C According to equation (10), the styrene removal efficiency Regarding the viscosity, viscosity at a shear rate of 15 s-1is not given within the Example 8 of WO 2023 / 001854 and WO 2023 / 001855. However, it is well known that for thermoplastic polymers like polyethylene the viscosity always decreases when shear rate increases. Therefore, viscosity at 15 s-1 shall be less than 4100 Pa·s. Generally, it should be easier removing volatile organic compounds like styrene (boiling point 75°C at 0.1 bar(a)) than SVOCs. Moreover, the molecular weight of styrene is just 104 kg / kmol, lower than phenyl acetic acid (136 kg / kmol) and almost half of lauric acid (200.3 kg / kmol). Therefore, diffusion is expected to be much higher. At first sight, therefore it could be surprising that the removal efficiency was as low as 94.4%, with a residual styrene of 75 wppm: for instance, Inventive Examples from 13 to 16 show that a removal efficiency over 99% and residual phenyl acetic acid below detection limit (50 wppm) was attained at much milder conditions: melt temperature 210 – 230°C versus 260°C and lower residence time as the strand height is 0.8 meters instead of 6 meters, the mass flow rate is up to 90 g / h / aperture vs 20 g / h / aperture, and the aperture diameter is 1.0mm vs 1.2mm. However, the modest result obtained in Comparative Example 35 could be explained by the likely low stability of the strand. In fact, the criterion of the minimum flow rate was not satisfied by this Comparative Example 35. According to equation (5), the ^^^^^^^^for Comparative Example 35 results to be: 5 ^ 10 4 ^ 73 2+ ^^^^^^ = 134.0 ∙ ∙ 63 exp(0.00075 ∙ (260 + 273))5∙4 1−24 3 ∙ −0.0000683 ∙ (260 + 273)3 4 4 ∙ 2+ )3 ∙ 9.82+ 3 = 4100 134.0 ∙1073∙ 61.5 ∙ ∙ 9.8−0.5 = 9.52 −6^^^^ ^^ 1.49 53 ∙ 10 [^^] = 34.3 [ℎ] The Comparative Example 35 had a flow rate per aperture of 20 g / h. Therefore the ^^^^^^^^^^, given by the ratio between the flow rate of 20 g / h and the ^^^^^^^^of 34.3 g / h, is 0.58 which is below the value of 1 required by the process according to the present invention. Additionally, as the value of viscosity of the Comparative Example 35 at 15 [s-1] is expected to be lower than 4100 [Pa·s], and ^^^^^^^^being inversely proportional to the square of viscosity, the actual value of ^^^^^^^^of the Comparative Example 35 shall be higher than 34.3 g / h and ^^^^^^^^^^lower than 0.58. This lower value of ^^^^^^^^^^can explain the modest removal VOC of the Comparative Example 35. In the present invention, odoriferous SVOCs, which are heavier than the styrene of Comparative Example 35 and therefore quite more difficult to remove by deodorization, were removed with even higher efficiency. Based on the above- reported analysis, the deodorization process of Comparative Example 35 is not able to reach this goal. The above working Examples show that the Invention allow to deodorize polyolefins to such extent that can be used for high value-added applications where absence or reduction of odor is mandatory. Since the concentrations of lauric acid and phenyl acetic acid in the polyethylene material of the Examples, before the deodorization process, were higher than the concentration of SVOCs odoriferous substances typically found in recycled polyolefins, treating the latter with the process disclosed in the present invention would impart an even lower level of odor or make the recycled polymer odor- free. In addition, the present process has been shown to satisfy all the aims such as, that it is simple, environmentally friendly and highly efficient for removing a large spectrum of odoriferous substances and, particularly, SVOCs odoriferous substances.

Claims

CLAIMS 1. Process for the production of deodorized polyolefins, comprising the steps of: (a) providing a feedstock based on post-consumer recycled polyolefins comprising in weight percentage (wt%) with respect to the total mass of feedstock based on post-consumer recycled polyolefins: (i) polyolefins ranging from 80 wt% to 99.5 wt%, preferably from 90 wt% to 99.0 wt%, even more preferably from 95 wt% to 99.0 wt%; (ii) semi-volatile organic compounds (SVOCs) odoriferous substances, ranging from 0.0001 wt% to 1.0 wt%; (iii) optionally, polymeric impurities; (iv) optionally, non-polymeric impurities; and (v) water ranging from 0 wt% to 9.9999 wt%; wherein the semi-volatile organic compounds (SVOCs) odoriferous substances (ii) are selected from carboxylic acids, esters, ethers, alcohols, aldehydes, ketones, sulfides, thiols, ammines, aromatic hydrocarbons, terpenes, alkanes, alkenes, phenols, phthalates, ethers, amides, imides, halogenated substances and combination thereof; and having a modified Kovats index (MKI) ranging from 1300 to 2300, wherein the modified Kovats index (MKI) of a generic compound i is defined by equation (1) ^^^^^^^^ = 100(1)where: ^^^^is the retention time (RT) of the generic compound for which the modified Kovats index has to be calculated; ^^^^13is the retention time (RT) of the normal tridecane (CAS number 629-50-5); and ^^^^23is the retention time of the normal tricosane (CAS number 638-67-5);where the retention time (RT) is the measure of the time taken by the generic compound to pass through a chromatography column within the gas chromatography analysis, wherein - the column has a length of 30 m, the inner diameter is 0.32 mm and the thickness is 0.1 ^m, - the stationary phase is mega-lap® produced by Mega, - the gas carrier is He at 1 ml / min, - the detector temperature is 320°C, - the injection volume is 1 ^l; - the heating program is set to the following: start at 80°C, increase to 17°C / min up to 320°C, isotherm at 320°C for 12 minutes; (b) bringing the feedstock to a deodorization device (1) in the form of a polymer melt feed, the deodorization device (1) comprising at least an inlet section (3) receiving the polymer melt feed at a temperature T, at least one distributor (5) with at least one aperture (6), said distributor (5) is connected to a closed vessel (10) provided with at least one polymer outlet (12) and at least one vapor outlet (8); (c) passing the polymer melt feed through said at least one aperture (6), thereby forming at least one polymer strand; (d) letting the at least one polymer strand drop into the closed vessel (10), thereby obtaining deodorized polyolefins in the closed vessel (10) and the removed vapours comprising, particularly, semi-volatile organic compounds (SVOCs) odoriferous substances (ii); (e) recovering and optionally pelletizing the deodorized polyolefins through the at least one polymer outlet (12); and (f) recovering and optionally condensing the removed vapours comprising, particularly, semi-volatile organic compounds (SVOCs) odoriferous substances (ii) through the at least onevapor outlet (8); wherein: - said at least one aperture (6) has an equivalent diameter (Dex) at the exit that is ranging from 0.4·10-3m to 10·10-3m, preferably from 0.8·10-3m to 5·10-3m, even more preferably from 0.9·10-3m to 3·10-3m, still more preferably from 1·10-3m to 2.5·10-3m, - the pressure in the closed vessel (10) is ranging from 1 to 8000 Pa (abs), preferably from 10 to 6000 Pa (abs), more preferably from 50 to 3500 Pa (abs), even more preferably from 100 to 2000 Pa (abs), still more preferably from 200 to 1500 Pa (abs), - the minimum flow ratio (mrmin), defined as the ratio between the mass flow (m), wherein (m) is the mass flow of the polymer melt feed flowing out of the apertures (6) divided by the number of apertures (6), and the critical minimum mass flow rate (mmin), is at least 1.0, preferably at least 1.2, even more preferably at least 1.3, wherein mmin is calculated according to the following equation (5) ^^^^^^^^ = 134.0where: 4 - ^^ is a numeric constant having value equals to 3, -^^ = 9.8^^is gravitational acceleration on Earth, - ^^ (Pa·s) is the dynamic viscosity, assumed to be the viscosity of the polymer melt feed at the temperature T at the inlet section (3) and at shear rate of 15 s-1, - ^^ (kg / s2) is the surface tension of the polymer melt feed, calculated with equation (4) ^^ = 0.0552 − 0.0000683 [^^−1] ∙ ^^ (4)- ^^ (m) is essentially the maximum length of the polymer strand,- - ^^ (kg / m3) is the density of the polymer melt feed, calculated with equation (3): ^^ = exp(3)- ^^ (K) is the temperature of the polymer melt feed at the inlet section 3.

2. Process according to claim 1, wherein the post-consumer recycled polyolefins are selected from the group consisting of polyethylene homopolymer, polyethylene copolymer, polypropylene, and mixture thereof.

3. Process according to claim 2, wherein the post-consumer recycled polyolefins are polyethylene homopolymer, polyethylene copolymer, and mixture thereof.

4. Process according to any one of the previous claims, wherein the molecular weight of the semi-volatile organic compounds (SVOCs) odoriferous substances (ii) is ranging from 80 to 600 Da, preferably from 100 to 400 Da, more preferably from 135 to 335 Da.

5. Process according to any one of the previous claims, wherein the boiling point of the semi-volatile organic compounds (SVOCs) odoriferous substances (ii), measured at the pressure of 0.1 bar(a), is ranging from 80°C to 350°C, preferably from 105°C to 300°C, more preferably from 150°C to 285°C.

6. Process according to any one of the previous claims, wherein the (iii) polymeric impurities are selected from the group consisting of polyamides, vinyl aromatic polymers (such as polystyrene, high impact polystyrene, styrene- acrylonitrile, acrylonitrile butadiene styrene), polyacrylates, (such as polymethyl methacrylate), polycarbonate, polyesters (such as polyethylene terephthalate, polybutylene terephthalate), polyphenylene ethers, polyether sulfones, polyether ketones, polyether sulphides and mixture thereof.

7. Process according to any one of the previous claims, wherein the (iii) polymeric impurities are at most 10 wt%,preferably in the range from 1 to 5 wt%, even more preferably in the range from 1.5 to 3 wt%.

8. Process according to any one of the previous claims, wherein the (iv) non-polymeric impurities are selected from the group consisting of antioxidants (such as tris(2,4-di- tert-butylphenyl) phosphite), anti-UV agents, lubricant agents, colouring agents, inorganic additives (such as inorganic carbon, in particular carbon black, graphene, coke, graphite), metal salts (such as calcium carbonate, calcium sulphate), perovskites, ilmenites (such as metal titanates), metal oxides (such as titanium oxide, aluminum oxide, iron oxide), metal dichalcogenides, silicates and especially phyllosilicates (such as hydrated magnesium silicate, serpentine, chlorite, micas, clay) and mixture thereof.

9. Process according to any one of the previous claims, wherein (iv) non-polymeric impurities are ranging from 0.005 to 5 wt%, more preferably from 0.05 to 3.5 wt%, even more preferably from 0.1 to 2.5 wt%.

10. Process according to any one of the previous claims, wherein the at least one aperture (6) is configured to have an aperture ratio (Dr), defined as the ratio between the equivalent diameter at the exit (Dex) and the critical diameter (Dcrit), at most 1.0, preferably at most 0.8, even more preferably at most 0.7, wherein Dcrit is defined according to the following equation (2) 5 1 Dcrit = 5.8 ∙ ^^ ∙ ^^−1 3∙ (g ∙ μ)6 ∙ ^^−2 63(2) where: - ^^ (kg / s) is the mass flow of the polymer melt feed flowing out of the apertures (6) divided by the number of apertures (6), - ^^ (kg / m3) is the density of the polymer melt feed, calculated according to the following equation (3)) -= 9.8is gravitational acceleration on Earth, - μ (Pa·s) is the dynamic viscosity, assumed to be the viscosity of the polymer melt feed at the temperature T at the inlet section (3) at shear rate of 15 s-1, - ^^ (kg / s2) is the surface tension of the polymer melt feed, calculated according to the following equation (4) ^^ = 0.0552 − 0.0000683 ∙ ([^^−1] ∙ ^^) (4)where ^^ (K) is the temperature of the polymer melt feed at the inlet section (3).

11. Process according to any one of the previous claims, wherein the polymer melt feed of step (c) is configured to have a maximum flow ratio (mrmax), defined as the ratio between the mass flow (m) and the critical maximum mass flow rate (mmax), is at most 1.0, preferably at most 0.8, even more preferably at most 0.7, wherein mmaxis calculated according to the following equation (6): ^^ −18 9.366 −5.4764 ^^^^^^ = 2 ∙ 10 ∙ ^^ ∙ ^^ ∙ exp [(0.088 − 2.945 ∙ 10 7 ∙ ^^^^2 −−1√^^^^) ] (6) where: - ^^ is essentially the maximum length of the polymer strand, - ^^ (°C) is the temperature of the polymer melt feed at the inlet section (3), - ^^^^ (Da) is the value of the molecular weight of the of the semi-volatile organic compounds (SVOCs) odoriferous substances (ii) having the highest molecular weight.

12. Process according to any one of the previous claims, wherein a pre-treatment step is carried out prior to step (a).

13. Process according to any one of the previous claims, wherein the temperature T in step (b) is ranging from 180°C to 280°C, preferably from 200°C to 250°C, more preferably from 205°C to 240°C, even more preferably from 210°C to 230°C.

14. Process according to any one of the previous claims, wherein the essentially maximum length H of the polymer strand is at most 5 meters, preferably between 0.5 and 4.0 meters.

15. Process according to any one of the previous claims, wherein the feedstock of step (a) is mixed with virgin polyolefin polymers, preferably in a mass ratio with respect to the feedstock (a) of up to 85:

15.

16. The deodorized polyolefins obtained according to any one of claims from 1 to 15.

17. Use of the deodorized polyolefins according to claim 16, for producing packaging and containers for cosmetics; bottles and rigid containers, such as containers for detergents, personal care products and household chemicals; pipes, used for example in supply of fluids, gas transport, irrigation; bins and drums, used for example for storing and transporting chemicals, oils, lubricants and other materials; flexible packaging, used for example to pack fragile products; shopping bags and rubbish bags; stretch film, used for example to wrap and protect pallets, boxes and other loads during transport and storage; shrink film, used for example to pack and / or protect books, magazines and containers collation such as bottles, cans, or boxes collations.

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