System and method for producing polyolefin food grade recyclates

Abstract

A method for producing polyolefin food grade recyclates, suitable for use in direct contact with food, includes the following steps: shredding the post-consumer polyolefin-based food grade plastic to obtain flakes; washing the flakes at a temperature from 55-95ºC; processing the flakes to obtain the polyolefin food grade recyclates; inspecting the post-consumer plastic to obtain a physical property parameter representative of a melt index of the plastic; separating the post-consumer plastic into a plurality of groups, based on the physical property parameter; introducing a predetermined amount of the polyolefin food grade recyclates into a pack, wherein the polyolefin food grade recyclates of the predetermined amount inserted into the pack are homogenous with respect to the physical property parameter; providing each pack with information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack.

Description

[0001] DESCRIPTION

[0002] SYSTEM AND METHOD FOR PRODUCING POLYOLEFIN FOOD GRADE RECYCLATES

[0003] Technical field

[0004] This invention relates to a method for producing polyolefin food grade recyclates and to a system for treating post-consumer plastic waste to produce polyolefin food grade recyclates.

[0005] Background art

[0006] Polyolefins belong to the family of thermoplastic materials which, thanks to their easy processability, low price and good chemical and physical properties, are widely used in the plastics industry. There are mainly four types of polyolefins: LDPE (low density polyethylene), LLDPE (linear low density polyethylene), HDPE (high density polyethylene) and PP (polypropylene); generally speaking, the most important polyolefins are polyethylene (PE) and polypropylene (PP). Polyolefins may have a variety of applications and are widely used in the packaging industry. In particular, polyolefins are widely used in the food packaging industry: plastic caps, for example, are commonly made of polyethylene or polypropylene.

[0007] On account of their large-scale application in the packaging industry, polyolefins constitute almost two thirds of all post-consumer plastic waste, and it is therefore necessary to create infrastructure suitable for collecting, sorting and recycling the polyolefins in post-consumer plastic.

[0008] Thus, there is a need to recycle post-consumer polyolefins in what is known as closed-loop recycling, whereby the recycled polyolefins are used for packaging (or other) purposes in their subsequent life cycles.

[0009] Traditionally, in plastic waste treatment plants, bales of plastic from different sources and different primary uses are collected and recycled. In these plants, the post-consumer plastic usually undergoes a recycling process to obtain plastic recyclates, which are then divided into different polymer groups; for example, at the end of the recycling process, the PET- based and polyolefin-based recyclates are separated using different methods, for example, using NIR and / or flotation technology.

[0010] One of the problems in the field of polyolefin recycling is, as mentioned above, that the polyolefins in plastic waste come from different sources and, depending on their primary use, may contain different quantities of contaminants; for example, a polyethylene used for detergent bottles can absorb contaminants that might not be removed during the recycling process, making it unsuitable for use in several applications, for example, in the food industry.

[0011] Therefore, polyolefin recyclates obtained by known recycling processes might include impurities and odours which exclude them from being used further in several applications because, in order to be suitable for re-use, the polyolefin recyclates must meet predetermined quality requirements which cannot be achieved by recycling mixed plastic waste. For the polyolefin recyclates to be considered at least potentially suitable for coming into contact with food, at least 95% of the starting material must originally have been food grade material. By the term "polyolefin food grade recyclates" used above is meant materials which have already been used in contact with, or as packaging for, food and which can be shown to conform with current food safety standards of authorities such as the EFSA and USFDA, regarding contact with foodstuffs.

[0012] The recycling process comprises several steps, such as shredding the plastic waste to obtain flakes, washing the flakes and extruding the washed flakes.

[0013] Typical washing processes, however, can remove only the contaminants from the surface of the polymers and are unable to remove the organic substances which have migrated into the polymer. Although the remelting or re-extrusion of the washed flakes could have a further cleaning effect, the level of purity obtained with those methods is usually inadequate for closed-loop recycling; thus, the polyolefin recyclates obtained with those methods might not be suitable for contact with food.

[0014] In this context, patent document EP3509811 B1 describes a method for producing polyolefin recyclates, specifically HDPE recyclates. In particular, that document describes a method for decontaminating the polyolefin recyclates to obtain polyolefin recyclates having an improved purity grade compared to polyolefin recyclates available on the market to date.

[0015] Furthermore, the document “Develop a food grade HDPE 1-5, IN. recycling process” by Frank Welle describes a series of experiments aimed at developing a cost-effective and industrial-scale recycling process for post-consumer HDPE milk bottles suitable for food contact and for the production of new milk bottles. In particular, the described process includes the following main steps:

[0016] - sorting of natural HDPE milk bottles;

[0017] - grinding and washing of the bottles using a conventional plastic bottle recycling process;

[0018] - "super-clean" decontamination using the EREMA process, which employs high temperatures and vacuum.

[0019] The documents “Stephen Lloyd: WRAP - Final Report: Research & development to improve the recyclability of plastic milk bottles” and CH 719121 A1 also provide examples of known methods for recycling polyolefins.

[0020] However, prior art systems and method for treating post-consumer plastic waste to obtain polyolefin food grade recyclates have some disadvantages and can be improved. In effect, there are several needs in this field.

[0021] In particular, there is a need for a post-consumer plastic waste treatment system for producing polyolefin recyclates more efficiently and capable of producing polyolefin food grade recyclates suitable for use in food packaging. Another need in this field is that for a post-consumer plastic treatment system for producing polyolefin food grade recyclates in a particularly reliable manner, which provides the user with information about the property of the polyolefin recyclates and which allows meeting the user's requirements.

[0022] Another need is to provide a post-consumer plastic waste treatment system for producing polyolefin food grade recyclates that reduces energy costs and consumption as much as possible.

[0023] Disclosure of the invention

[0024] The aim of this invention is to provide a system and a method for producing polyolefin food grade recyclates to overcome the above mentioned disadvantages of the prior art.

[0025] This aim is fully achieved by the method and the system of this disclosure as characterized in the appended claims.

[0026] According to an aspect of it, this disclosure provides a method for producing polyolefin food grade recyclates (that is to say, food safe), suitable for use in direct contact with food. The method includes a step of collecting polyolefin-based, food grade post-consumer plastic. The polyolefin-based, food grade plastic is formed of material used for beverage purposes. The polyolefin-based, food grade plastic may be provided by the bales of post-consumer plastic containers. In an example, the bales of post-consumer plastic containers are divided into a first group of material and a second group of material, where the first group is formed of material used for beverage purposes and the second group is formed of material used for non-beverage purposes. The method comprises a step of shredding the food grade, post-consumer plastic to obtain flakes. The method comprises a step of washing the flakes at a temperature which falls within a range of 40-1 10eC, preferably 50-100eC, and more preferably 55-95eC. This is the temperature at which the plastic flakes are washed. In particular, this temperature is the temperature of the washing water used to wash the plastic flakes. The washing water may be water only or it may be other solutions.

[0027] The step of washing allows removing contaminants, residues, volatile compounds (which may cause odours) and other impurities from the plastic flakes, and enhancing the efficiency of decontamination after the hot wash performed when carrying out the method for producing polyolefin food grade recyclates. The washing temperature may significantly affect the efficacy of the decontamination process. This temperature range allows striking a good compromise between obtaining efficient decontamination and energy consumption and preserving quality (too high a temperature could deform or deteriorate the plastic). In particular, the lower value of each of the ranges specified above is the temperature of the water (water and / or other washing solutions), and the upper value is just below boiling point.

[0028] The method comprises a step of processing the flakes through a polyolefin recycler to obtain the polyolefin food grade recyclates. The method comprises a step of inspecting the post-consumer polyolefin-based food grade plastic to obtain a physical property parameter. In an example, the physical property parameter is representative of a melt index of the postconsumer polyolefin-based food grade plastic. The method comprises a step of separating the post-consumer polyolefin-based, food grade plastic based on the physical property parameter. In particular, the post-consumer polyolefin-based, food grade plastic is separated into a plurality of groups. In addition, a respective physical property parameter is assigned to each group of the plurality of groups. The method comprises a step of providing a pack. The method comprises a step of introducing a predetermined amount of the polyolefin food grade recyclates into the pack. The polyolefin food grade recyclates of the predetermined amount of polyolefin food grade recyclates inserted into the pack are homogenous with respect to the physical property parameter. The method comprises a step of providing each pack with information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack.

[0029] It should be noted that the polyolefin flakes are derived from material previously used only for beverages; it does not therefore contain contaminants making it unfit for direct contact with food, and is of a food grade high enough to be used in food packaging; for example, to produce plastic caps. It is therefore possible to obtain polyolefin recyclates with a high food grade and a higher level of efficiency. Moreover, since the postconsumer material used to obtain the polyolefin recyclates was previously in contact only with food, the contaminants can be removed by processes that are less complicated and less expensive and require less energy compared to prior art methods.

[0030] Thus, the polyolefin recyclates obtained with this method are very high quality.

[0031] Moreover, the post-consumer plastic is inspected and divided based on the physical property parameter and the polyolefin food grade recyclates are placed in packs which provide information regarding the physical property parameter of the polyolefin recyclates. This solution allows the user to have information regarding the property of the polyolefin recyclates inside the pack (for example, the melt index of the polyolefin recyclates) which is important for the process in which the polyolefin recyclates will subsequently be used (for example, injection or compression moulding) to obtain a final product. Users can therefore choose the packs of polyolefin recyclates based on their requirements.

[0032] In an example, the physical property parameter is derived through an inspection carried out on the flakes.

[0033] In an example, the flakes are separated based on colour. The flakes may also be divided according to the type of polymer. The physical property parameter may be obtained based on the colour of the flakes.

[0034] In particular, a melt index range may be associated with the postconsumer plastic based on the colour because, in this field of industry, each colour is usually associated with a given melt index range. In an example, the post-consumer polyolefin-based food grade plastic before shredding is separated based on the primary application and the physical property parameter is obtained based on the primary application. It should be noted that in another example, the flakes may be divided based on the primary application. By "primary application" is meant the application of the post-consumer plastic when it was first used (for example, plastic previously used for the caps for carbonated or non-carbonated beverages, or plastic used for milk bottles, etc.). It should be noted that in the plastics industry, every application uses a type of plastic with certain properties (in particular, melt index); thus, knowing the primary application of the postconsumer plastic from which the flakes are obtained allows assigning a range of melt index (or of other properties) to that plastic.

[0035] The flakes may be inspected and divided based both on colour and on primary application or based on only one of these criteria.

[0036] In particular, sorting the flakes based on the colour and / or the primary application of the plastic which provides the flakes allows estimating a melt index range of the polymer, separating the flakes into different groups based on the estimated melt index for each colour and / or primary application and assigning a respective physical property parameter to the flakes of each group. Sorting in this manner is particularly easy, reliable and cost effective.

[0037] The method may comprise a step of separating the flakes into a plurality of subsets based on the physical property parameter. It should be noted that the physical property parameter may be obtained according to any of the above-mentioned criteria. In each subset, the flakes are homogenous with respect to the physical property parameter. In other words, the flakes of each subset have a specific range for the value of the physical property parameter which is the same for all the flakes in that subset.

[0038] The method may comprise a step of processing each subset of the plurality of subsets separately through the polyolefin recycler, to obtain a respective plurality of subsets of polyolefin food grade recyclates.

[0039] In an example, the physical property parameter is obtained by performing a melt index test on the flakes and / or on the polyolefin food grade recyclates. It should be noted that this test is conducted according to the standards known in this field.

[0040] The physical property parameter may be obtained both by inspecting the flakes according to one or more of the methods explained above and by performing a melt index test on the flakes and / or on the polyolefin food grade recyclates, or based on only one of these methods.

[0041] In an example, the information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack includes information on how the physical property parameter is obtained. For example, the information may explain that the physical property parameter used to sort the polyolefin food grade recyclates was obtained by separating the flakes based on colour.

[0042] In an example, the information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack includes operational information representative of the application of the polyolefin food grade recyclates in a moulding process for obtaining a final product from the polyolefin food grade recyclates of each pack. This operational information is defined as a function of the operating conditions of the moulding process.

[0043] In an example, the operational information includes information on a suggested percentage of the polyolefin food grade recyclates to be used in combination with virgin polymer.

[0044] The method may comprise a step of extruding the flakes. The method comprises a step of pelletizing the extruded flakes to obtain polyolefin food grade granules. Thus, in an example, the polyolefin recyclates are granules of polyolefin recyclates.

[0045] In an example, the method comprises a step of decontaminating the flakes through a decontamination unit. In an example, decontamination is carried out after extrusion. Decontamination is carried out after pelletizing the extruded flakes. In this example, there may be a step of vacuuming the flakes during and / or after the step of decontaminating them.

[0046] This solution improves the efficiency of decontamination and removes the by-products of decontamination (for example, acetone).

[0047] In an example, the polyolefin food grade recyclates, before being inserted in the pack, are subjected to a quality control. Moreover, one or more operational conditions of the step of decontaminating them are adjusted in response to the step of the quality control.

[0048] Thus, if the results of the polyolefin quality control carried out after decontamination do not correspond to predetermined standards, one or more of the operational conditions are adjusted.

[0049] The polyolefin quality control may be carried out before or after decontamination.

[0050] After adjusting the operational condition, the polyolefins are subjected to another quality control to ensure that the quality of the polyolefins corresponds to the predetermined values and, if there is still a deviation between the predetermined values and the results of the quality control, another adjustment is performed. Thus, polyolefin quality control may be a feedback control system.

[0051] If the control is carried out after decontamination and the results do not correspond to the predetermined values, the polyolefins undergo another decontamination cycle.

[0052] In an example, the operational conditions include one of more of the following parameters:

[0053] - a flow rate at which the extruded flakes are fed to the decontamination unit;

[0054] - temperature at which the flakes are vacuumed;

[0055] - the period of time for which the flakes are vacuumed.

[0056] According to an aspect of it, this disclosure provides a system for treating post-consumer plastic waste to produce polyolefin food grade recyclates, suitable for use in direct contact with food. The system comprises an input unit. The input unit is configured to receive post-consumer polyolefin- based food grade plastic formed of material used for beverage purposes. The system includes a shredder. The shredder is configured to shred the post-consumer polyolefin-based food grade plastic to obtain flakes.

[0057] The system includes a washing unit, located downstream of the shredder and configured to wash the flakes at a temperature which falls within a range of 55 to 95eC.

[0058] The system comprises a polyolefin recycler. The polyolefin recycler is configured for processing the flakes to obtain the polyolefin food grade recyclates.

[0059] The system includes an inspection centre for inspecting the postconsumer polyolefin-based food grade plastic to obtain a physical property parameter. The physical property parameter is representative of a melt index of the post-consumer polyolefin-based food grade plastic. The system includes a separation centre. The separation centre is configured to separate the post-consumer polyolefin-based food grade plastic, based on the physical property parameter, into a plurality of groups, where a respective physical property parameter is assigned to each group of the plurality of groups. The system includes a packaging unit for introducing a predetermined amount of the polyolefin food grade recyclates into the pack. The polyolefin food grade recyclates of the predetermined amount of polyolefin food grade recyclates inserted into the pack are homogenous with respect to the physical property parameter.

[0060] The system includes a labelling unit for providing each pack with information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack.

[0061] In an example, the inspection centre is configured to carry out an inspection on the flakes to obtain the physical property parameter.

[0062] In an example, at least one of the following conditions is verified:

[0063] - the flakes are separated based on colour and the physical property parameter is obtained based on the colour of the flakes,

[0064] - the post-consumer polyolefin-based food grade plastic before shredding is separated based on the primary application and the physical property parameter is obtained based on the primary application. Thus, both of these conditions are verified at the same time or only one and not the other.

[0065] In an example, the separation centre is configured to separate the flakes into a plurality of subsets, based on the physical property parameter. In each subset the flakes are homogenous with respect to the physical property parameter. The polyolefin recycler is configured to process each subset of the plurality of subsets separately to obtain a respective plurality of polyolefin food grade recyclate subsets. In an example, the inspection centre is configured to perform a melt index test on the flakes and / or on the polyolefin food grade recyclates to obtain the physical property parameter.

[0066] In an example, the information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack includes information on how the physical property parameter is obtained.

[0067] In an example, the information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack includes operational information representative of the application of the polyolefin food grade recyclates in a moulding process for obtaining a final product from the polyolefin food grade recyclates of each pack as a function of the operating conditions of the moulding process. The operational information includes information on a suggested percentage of the polyolefin food grade recyclates to be used in combination with virgin polymer. In an example, the polyolefin food grade recyclates are in the form of granules.

[0068] Described below is an aspect not covered by the claims.

[0069] According to an aspect of this disclosure, the method comprises a step of dividing the material provided by the post-consumer plastic bales into a first group and a second group. The first group of material is formed of material used for beverage purposes. The second group of material is formed of material used for non-beverage purposes. Thus, according to an aspect of this disclosure, the first group provides food grade postconsumer plastic formed of material used for beverage purposes. The post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes may include only polyolefin-based plastic or it may be mixed with other food grade post-consumer plastic (not polyolefin based) formed of material used for beverages; in this example, there is a step of separating the post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes from the plastic which is not based on polyolefins.

[0070] The method comprises a step of shredding the first group of material to obtain plastic flakes.

[0071] The method comprises a step of sorting the plastic flakes to derive a first subset and a second subset. The first subset may be formed of PO (polyolefin) flakes. The second subset may be formed of PET (polyethylene terephthalate) flakes. The second subset may also be formed of other plastic materials. The second subset may therefore comprise flakes that do not include PO. It should be noted that in the step of sorting, the plastic flakes may be divided into more than two subsets.

[0072] The method comprises a step of processing the first subset of flakes through the polyolefin recycler. The first subset is processed through the polyolefin recycler to obtain polyolefin food grade recyclates. Thus, according to an aspect of this disclosure, the first subset provides the flakes of polyolefin-based food grade post-consumer plastic formed of material used for beverage purposes.

[0073] Thus, according to an aspect of this disclosure, the post-consumer plastic material collected in the form of bales of post-consumer plastic containers, is divided into materials used for beverage purposes and material used for purposes other than beverages, and the material used for beverage purposes subsequently undergoes a recycling process during which the polyolefin flakes are separated from other plastic flakes and are further recycled in a polyolefin recycler to obtain polyolefin food grade recyclates. It should be noted that the PO flakes are derived from material previously used only for beverages; it does not therefore contain contaminants making it unfit for direct contact with food, and is of a food grade high enough to be used in food packaging; for example, to produce plastic caps. This solution allows obtaining polyolefin recyclates with a high food grade and more efficiently. Moreover, since the post-consumer material used to obtain the polyolefin recyclates was previously in contact only with food, the contaminants can be removed by processes that are less complicated and less expensive and require less energy compared to prior art methods.

[0074] Thus, the polyolefin recyclates obtained with this method are very high quality.

[0075] In an example, the step of processing the first subset of flakes through the polyolefin recycler includes a step of classifying the first subset of flakes. In an example, the first subset of flakes is classified according to polymer type and / or colour. The first subset of flakes might be classified according to other criteria. It is therefore possible to classify different polyolefins, for example, PP (polypropylene) and PE (polyethylene) to use each type of polyolefin recyclates for a specific application. The flakes can also be separated into different groups based on colour, so that the polyolefin recyclates obtained from each group are uniformly coloured or similar in colour.

[0076] The step of processing the first subset of flakes through the polyolefin recycler also includes a step of extruding the first subset of flakes. More specifically, the flakes of the first subset are fed into one or more extruders; the flakes are melted in the extruder and then decontaminated and regranulated. In particular, the extruder must be provided with filters to remove undesirable components from the molten flakes. The molten flakes can therefore be degassed, and / or filtered, and / or purified. On account of the high temperatures used, the step of extruding allows eliminating possible contamination due to volatile substances in the flakes.

[0077] The step of processing the first subset of flakes through the polyolefin recycler also includes a step of decontaminating and purifying the flakes after extrusion.

[0078] The step of processing the first subset of flakes through the polyolefin recycler also includes a step of pelletizing the extruded, purified flakes to obtain polyolefin food grade granules.

[0079] In an example, in the step of processing the first subset of flakes through the polyolefin recycler, additives are added to the extruded flakes in order to enhance the food grade of the granules obtained.

[0080] In an example, the additives may include virgin polyolefins whose viscosity is similar or different to that of the recycled material, antioxidant additives or additives of other kinds, such as lubricants or colouring substances. In another example, the additives may include other materials which enhance the food grade of the granules obtained.

[0081] In an example, the polymer is classified using near-infrared (NIR) spectroscopy systems. In another example, the polymer may be classified using other technologies.

[0082] In an example, the method comprises a step of preselecting. The step of preselecting is applied to the first subset of flakes. In an example, the step of preselecting is applied to the first subset of flakes prior to the step of processing the first subset of flakes. In other words, preselection can be applied to the first subset of flakes before the flakes are conveyed to the polyolefin recycler. In another example, the first subset of flakes may first be conveyed to the polyolefin recycler and then subjected to the step of preselecting. The step of preselecting includes inspecting the first subset to identify undesired items and / or possible contaminations in the first subset of flakes. In an example, the step of preselecting is carried out though an artificial intelligence visual control system, and / or olfactory sensors for identifying contaminants. In another example, the visual inspection may be carried out by an operator. Therefore, the step of preselecting may be automatic or manual. In an example, the step of preselecting is a batch process. Preselection ensures that undesired or contaminated items do not enter the polyolefin recycler. In an example, the method comprises a step of inspecting the food grade of the polyolefin recyclates, after the step of processing so as to verify that the food grade corresponds to a predetermined grade.

[0083] In an example, the method comprises a step of collecting the plastic caps for reusable or refillable beverage bottles. The method may also comprise a step of shredding the plastic caps to obtain plastic cap flakes. The plastic cap flakes are classified in the first subset of flakes.

[0084] The first subset of flakes processed through the polyolefin recycler also includes the plastic cap flakes. In an example, therefore, the first subset of post-consumer material derived from the bales of post-consumer plastic containers and the flakes derived from the plastic caps are processed to obtain the polyolefin food grade recyclates. It should be noted that both the plastic cap flakes and the first subset of post-consumer material derived from the bales of post-consumer plastic containers are polyolefins previously used only for beverages and thus have a high food grade. The plastic cap flakes and the first subset of post-consumer material derived from the bales of post-consumer plastic containers can be processed through the polyolefin recycler together or separately. It should be noted that the plastic caps are made from polyolefins.

[0085] In an example, the division of the material into the first group and the second group is applied to the post-consumer plastic container bales collected, so that each post-consumer plastic container bale collected belongs either to the first group or to the second group. In this example, the bales formed of post-consumer plastic containers used for beverage purposes are collected separately from those formed of post-consumer plastic containers used for non-beverage purposes, hence each bale belongs either to the first group or to the second group. In another example, each post-consumer plastic container bale may include material used for beverage purposes, as well as material used for non-beverage purposes; in this example, for each bale, the material used for beverage purposes and the material used for non-beverage purposes are divided into the first group and the second group, respectively.

[0086] In an example, the step of processing the first subset of flakes through the polyolefin recycler comprises a step of further grinding the first subset of flakes to obtain homogenized flakes.

[0087] The step of processing the first subset of flakes through the polyolefin recycler may comprise a step of demetallizing the first subset of flakes.

[0088] The step of processing the first subset of flakes through the polyolefin recycler may comprise a step of washing the first subset of flakes.

[0089] The step of processing the first subset of flakes through the polyolefin recycler may comprise a step of deodorizing. Deodorization may be performed on the first subset of flakes after the step of shredding or on the polyolefin granules obtained after the step of pelletizing. It should be noted that deodorization is performed on the unmelted (hence solid) flakes. During deodorization, the flakes are heated (for example, to 60°C). Some volatile compounds which can cause undesirable odours can be removed during the step of decontaminating, carried out on the flakes after extrusion; the purpose of decontamination, however, is also to remove contaminants other than volatile compounds.

[0090] In this disclosure, therefore, the term "deodorization" is used to denote the process carried out before extrusion and the term "decontamination" to denote the process carried out after extrusion.

[0091] According to another aspect, not claimed in this disclosure, the postconsumer plastic waste treatment system for producing polyolefin food grade recyclates (called "the system" for short) comprises an input stage. The input stage receives post-consumer plastic container bales. The system comprises a division centre. The division centre is configured to divide the material provided by the post-consumer plastic bales into a first group and a second group. The first group of material is formed of material used for beverage purposes. The second group of material is formed of material used for non-beverage purposes.

[0092] The system comprises a shredder. The shredder is configured to shred the first group of material to obtain plastic flakes.

[0093] The system comprises a sorting unit. The sorting unit is configured for sorting the plastic flakes to derive a first subset and a second subset. In an example, the first subset is formed of PO flakes. The second subset may be formed of PET flakes. Thus, according to an aspect of this disclosure, the first subset provides the flakes of polyolefin-based food grade postconsumer plastic formed of material used for beverage purposes.

[0094] The system includes the polyolefin recycler. The polyolefin recycler is configured for processing the first subset of flakes to obtain the polyolefin food grade recyclates.

[0095] In an example, the input stage of the system receives plastic caps used in reusable or refillable beverage bottles. The shredder may also be configured for shredding the plastic caps to obtain plastic cap flakes. The plastic cap flakes are classified in the first subset of flakes. The first subset of flakes processed through the polyolefin recycler also includes the plastic cap flakes. The system may also comprise a preselection unit. In an example, the preselection unit is configured to receive the first subset of flakes upstream of the polyolefin recycler. The preselection unit is configured to inspect the first subset of flakes to identify undesired items and / or possible contaminants in the first subset of flakes.

[0096] The system may comprise a final inspection unit. The final inspection unit is configured to inspect the food grade of the polyolefin recyclates, downstream of the polyolefin recycler to verify that the food grade corresponds to a predetermined grade. the polyolefin recycler comprises a polyolefin shredder. The polyolefin shredder of the polyolefin recycler is configured for further grinding the first subset of flakes to obtain homogenized flakes.

[0097] The polyolefin recycler may include a demetallization unit. The demetallization unit is configured for demetallizing the first subset of flakes.

[0098] The polyolefin recycler includes a washing unit. The washing unit is configured for washing the first subset of flakes.

[0099] The system may also include a sieving unit to eliminate dust and pieces of plastic which are too small to be effectively separated; for example, the mesh size of the sieve is less than 5 mm, or less than 3 mm or less than 2 mm.

[0100] The system may also include an elutriation unit in which the remains of bottle labels and dust are removed by an air flow. Preferably, the sieving unit and the elutriation unit are located upstream of the preselection unit. Alternatively, the sieving unit and the elutriation unit may form part of the preselection unit.

[0101] The polyolefin recycler includes a classification unit. The classification unit is configured for classifying the first subset of flakes. In an example, the classification unit is configured for classifying the first subset of flakes based on polymer type and / or colour.

[0102] The polyolefin recycler includes an extruder. The extruder is configured for extruding the first subset of flakes.

[0103] The polyolefin recycler includes a decontamination unit. The decontamination unit is configured for decontaminating and purifying the extruded flakes.

[0104] The polyolefin recycler includes an enhancement unit. The enhancement unit is configured for adding additives to the extruded flakes in order to enhance the food grade of the granules obtained.

[0105] The polyolefin recycler includes a pelletizing unit. The pelletizing unit is configured to obtain polyolefin food grade granules from the extruded flakes. The polyolefin recycler may include a deodorization unit. In an example, the deodorization unit is located upstream of the extruder. The deodorization unit is configured for deodorizing the first subset of flakes. In another example, the deodorization unit may be located downstream of the extruder. In this example, the deodorization unit is located downstream of the pelletizing unit and is configured for deodorizing the polyolefin granules. Brief description of drawings

[0106] These and other features will become more apparent from the following description of a preferred embodiment, illustrated by way of non-limiting example in the accompanying drawings, in which:

[0107] - Figures 1A and 1 B illustrate the steps of producing and separating the polyolefin recyclates according to one or more aspects of this disclosure;

[0108] - Figures 2A, 2B and 3 represent a process for closed-loop recycling of post-consumer plastic waste through a post-consumer plastic waste treatment system according to one or more aspects of this disclosure, for producing polyolefin food grade recyclates, suitable for use in direct contact with food;

[0109] - Figures 4A and 4B illustrate the polyolefin recycler used in the postconsumer plastic waste treatment system;

[0110] - Figure 5 illustrates the post-consumer plastic waste treatment system for producing polyolefin food grade recyclates;

[0111] - Figure 6 illustrates the viscosity of the HDPE after several process cycles;

[0112] - Figures 7 and 8 illustrate the results of experiments conducted on the caps;

[0113] - Figure 9 shows a flow diagram of the polyolefin production line;

[0114] - Figure 10 shows a cross section of the polyolefin production line.

[0115] Detailed description of preferred embodiments of the invention

[0116] With reference to the accompanying drawings, the numeral 1 denotes a post-consumer plastic waste treatment system for producing polyolefin food grade recyclates. The polyolefin food grade recyclates are suitable for use in direct contact with food. The post-consumer plastic waste treatment system for producing polyolefin food grade recyclates suitable for use in direct contact with food ("the system" for short) 1 includes an input stage I for receiving post-consumer plastic container bales B. The post-consumer plastic container bales B ("the bales" for short) include plastic containers and caps. In particular, the bales may include both plastic used for beverage purposes (or food packaging generally) and plastic used for other purposes. In an example, the post-consumer plastic used for beverage purposes is received at the input stage I separately from the plastic used for non-beverage purposes; thus, in an example, each bale B received at the input stage I contains either plastic used for beverage purposes or plastic used for non-beverage purposes. The plastic used for beverage purposes may be collected in smart waste bins (that is, reverse vending machines) which collect empty beverage bottles (or bottles used to contain food products generally) or at points of sale where consumers pay a small deposit which is returned to them when they bring the empty container back after using its contents). The plastic used for beverage purposes may also be collected at other points, as long as it is guaranteed that the plastic containers have been used only for food products. The post-consumer plastic used for other purposes may be collected together with urban waste. This plastic is mixed plastic, hence post-consumer plastic which has been used for different purposes and has come into contact with different materials (both food and non-food). Generally speaking, the bales B are formed by a post consumer material collection centre POC, where empty plastic containers CO are collected after being used by users U. In an example, the input stage I of the system 1 also receives post-consumer plastic caps C. In an example, these plastic caps are used in refillable beverage bottles. These plastic caps may also include caps that are separate from the bodies of the plastic beverage bottles. The plastic caps C, after being used by users U, are collected in a post consumer material collection centre POC. These plastic caps are mainly made from polyolefins. Preferably, the plastic caps are collected separately from the bales B. As explained above, the bales provide postconsumer plastic material. This material is divided into a first group P1 , formed of material used for beverage purposes, and a second group P2, formed of material used for non-beverage purposes. The first group P1 constitutes post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes. The post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes is collected in an input unit e. If the first group contains plastic which is not polyolefin-based, there is a step of separating only the post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes. This plastic is then shredded. Subdividing the material into the first and the second group is carried out at a division centre 2 of the system 1 . When the system receives the plastic caps C in addition to the bales B, the step of dividing the material is carried out only on the bales, since the plastic caps collected are from beverage bottles and are made only from material used for beverage purposes. Thus, the first group of material includes the plastic caps and the material used for beverage purposes provided by the bales B. The division of the material into the first group R1 and the second group P2 is applied to the post-consumer plastic container bales B collected, so that each post-consumer plastic container bale B collected belongs either to the first group P1 or to the second group P2. The first group P1 includes only material used for beverage purposes (or for packaging food generally), hence is less contaminated than the second group P2; the first group P1 , therefore, is more suitable for use in the recycling of polyolefins. After leaving the division centre 2, the first group of material enters a plastic recycler R. In particular, in the plastic recycler R, the first group undergoes several processes. For example, the plastic recycler R has a shredder 3 for shredding the first group of material to obtain plastic flakes. In particular, the shredder 3 shreds the postconsumer polyolefin-based food grade plastic to obtain flakes. The plastic flakes are washed in a washing stage (washing unit) 604. The washing stage reaches high temperatures to remove contaminants from the postconsumer plastic flakes. In particular, the flakes are hot washed at a temperature between 55 and 95°C, preferably 80°C. Further, washing may be carried out in a 0.3-0.5% w / w concentrated solution of NaOH. Preferably, the flakes are hot washed straight after being shredded.

[0117] In an example, the second group of material may be processed separately from the first group of material P1 , in a plastic recycler similar to the one used to process the first group of material. In this example, the washed flakes of the second group of material P2 are collected for use in applications where food grade polyolefins are not required.

[0118] On leaving the plastic recycler R, the washed flakes of the first group P1 are conveyed to a sorting unit 4, where the plastic flakes are divided into a first subset S1 , formed of polyolefin flakes, and a second subset S2, formed of PET flakes. It should be noted that besides PET, the second subset may include flakes of other plastic materials. Preferably, the step of sorting the plastic flakes to derive the first and the second subset of flakes is carried out by flotation separation and is based on specific gravity. In this method, the plastic flakes of the first group P1 , after being washed, are separated by flotation in water (or other liquid); since the PET (the second subset) is denser than water, while the polyolefins (the first subset) are less dense than water, the second subset S2 sinks and the first subset floats. The flakes are then dried. The step of sorting the plastic flakes to derive the first and the second subset of flakes may be carried out by other methods.

[0119] The first subset of flakes is then processed through a polyolefin recycler 6 to obtain the polyolefin food grade recyclates. In particular, the polyolefin recyclates obtained from the polyolefin recycler 6 are in the form of granules. Furthermore, the plastic caps are also shredded in the shredder 3 to obtain plastic cap flakes. The plastic cap flakes may be washed in the washing stage. The plastic cap flakes C may be processed in the plastic recycler R separately from, or together with, the first material P1 . It should be noted that the plastic cap flakes are classified in the first subset of flakes, so the first subset of flakes processed through the polyolefin recycler 6 also includes the plastic cap flakes. In another example, the plastic caps C may be fed directly to the polyolefin recycler 6 without undergoing any other processes in the plastic recycler R before entering the polyolefin recycler 6. The system 1 includes a preselection unit 5, where a step of preselecting is applied to the first subset of flakes S1 before it is conveyed to the polyolefin recycler 6. During the step of preselecting, the first subset of flakes is inspected to identify undesired items and / or possible contaminations in the first subset of flakes. The step of preselecting may comprise a visual inspection carried out by an operator or by an artificial intelligence system. Contaminations or unpleasant odours are identified using olfactory sensors or gas chromatography. Other methods can be used in the step of preselecting. After being inspected in the preselection unit 5, the first subset is conveyed to an entrance 601 of the polyolefin recycler 6. Thus, the first subset of flakes, which includes the plastic cap flakes and the flakes derived from the first group of material R1 , is fed to the polyolefin recycler 6. The polyolefin recycler 6 includes a polyolefin shredder 602. In particular, the first subset of flakes may be further shredded in the polyolefin shredder 602 to obtain homogenized flakes.

[0120] The polyolefin recycler 6 includes a demetallization unit 603, where the first subset of flakes is demetallized. The demetallization of the first subset of flakes is carried out by magnetic means or through eddy currents.

[0121] The first subset of flakes is washed in a washing unit 604 of the polyolefin recycler 6. The washed flakes of the first subset are classified on the basis of polymer type and / or colour of the flakes. This classification occurs in a classification unit 605 of the polyolefin recycler 6 and may be carried out through NIR systems, optical systems, by flotation separation or by centrifuge. The classification unit 605 includes a polymer separator 605A, where the flakes are classified on the basis of polymer type. The classification unit 605 includes a colour separator 605B, where the flakes are classified on the basis of their colour.

[0122] The flakes which have been classified are then purified in a refining stage 606 of the polyolefin recycler 6. The refining stage includes an extruder 606A in which the first subset is extruded. The refining stage includes a decontamination unit 606B, where the extruded flakes are filtered and purified to remove volatile substances and other contaminants.

[0123] The refining stage 606 may also include an enhancement unit 606C. In particular, in the enhancement unit, additives are added to the extruded flakes in order to enhance the food grade of the granules obtained. The additives include virgin polyolefins and / or anti-oxidants.

[0124] The polyolefin recycler 6 includes a pelletizing unit 607, where the extruded flakes are transformed into polyolefin food grade granules in the pelletizing unit 607. The polyolefin recycler 6 may comprise a deodorization unit D. The deodorization unit D may be located before the refining stage 606, hence before the extruder 606A. In an example, therefore, the first subset of flakes is deodorized before being extruded. In an example, the deodorization unit is located after the washing unit. In other examples, the deodorization unit may be located downstream of the entrance 601 of the polyolefin recycler, or downstream of the polyolefin shredder 602, or downstream of the demetallization unit 603, or downstream of the classification unit 605. In another example, the deodorization unit may be located upstream of the polyolefin recycler 6. In another example, the deodorization unit D may be located downstream of the pelletizing unit 607 and deodorizes the polyolefin granules (Figure 2B). The system 1 comprises a final inspection unit 7. The final inspection unit 7 receives the polyolefin recyclates at an exit 608 of the polyolefin recycler 6. The final inspection unit 7 inspects the polyolefin recyclates to verify that the food grade corresponds to a predetermined grade. The final inspection unit 7 is located at an exit O of the system. The granules obtained at the exit O of the system are then conveyed to a production unit M, where they are used for new products, for example, new containers and / or plastic caps made from the granules of polyolefin recyclates.

[0125] Described below is the process for producing food grade polyolefins according to Figure 9.

[0126] Post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes is collected and shredded in a shredder 3.

[0127] In particular, after being shredded, the flakes are hot washed at a temperature between 55 and 95°C, preferably 80°C. Further, washing may be carried out in a 0.3-0.5% w / w concentrated solution of NaOH.

[0128] Preferably, the flakes are hot washed straight after being shredded. After hot washing, the flakes undergo a control step, which measures different flake parameters such as, for example, moisture, polymer type, presence of foreign matter, volatile substances, etc.

[0129] After this control, the flakes can be stored and are ready for subsequent processing. Next, there is a step of sieving, during which the flakes are sieved. Preferably, in this step, sieves with a mesh size of 3 mm are used to remove material having a smaller particle size. Next, polymers and foreign matter are eliminated by automatic selection systems (for example, optical, NIR, laser systems, etc.).

[0130] The flakes may be separated according to colour (white, neutral, red, green blue hues etc.).

[0131] The flakes are then fed into a deodorization unit D and flushed with hot air to remove a first quantity of volatile substances. Preferably, during deodorization, a vacuum is also applied to accelerate the removal of volatile substances. There may be a feedback control system for the step of deodorization to check whether the volatile substances have been removed so that, if volatile substances are still present in a quantity greater than a predetermined threshold, another deodorization cycle is carried out. Moreover, some of the operating conditions of the deodorization unit could be regulated as a function of the feedback control. After being deodorized, the flakes are fed into the extruder 606A, where they are melted. The extruder may comprise a degassing section. The melted polyolefins are continuously filtered to remove extraneous matter, low melting polymers. Downstream of the extruder there is a prefiltering unit PF. Downstream of the prefiltering unit, there may be a melt pump MP. The molten flakes are decontaminated in a decontamination unit 606B. Decontamination occurs preferably in a vacuum. A vacuum system V is provided to extract contaminants. During decontamination, the molten flakes are agitated at high temperature, for example, 200-240°C in a vacuum, for example, 2-4 mbar, for long enough to devolatilize even relatively high molecular weights. During and / or after decontamination inside the decontamination unit, a quality control may be carried out on the flakes to check them for contaminants. Moreover, one or more operational conditions of the step of decontaminating them are adjusted in response to the step of the quality control.

[0132] In an example, the operational conditions include one of more of the following parameters:

[0133] - a flow rate at which the extruded flakes are fed to the decontamination unit;

[0134] - temperature at which the flakes are vacuumed;

[0135] - the period of time for which the flakes are vacuumed.

[0136] Downstream of the decontamination unit, there may be another melt pump MP. A viscometer VI may be provided downstream of the decontamination unit to measure the viscosity of the decontaminated, molten flakes. The molten polyolefins are then fed into a pelletizing unit 607, where they are pushed through a die and, as they exit the die, are cut in water to form granules of polyolefins of the desired size.

[0137] After the pelletizing unit there may be a deodorization and degassing unit, where the granules are fed into a closed apparatus and flushed with hot air to remove any volatile substances that may have formed during decontamination. This step also serves to dry the granules. If necessary, a vacuum may also be applied during this step to accelerate the removal of the volatile substances.

[0138] The granules are then transferred to a packaging unit PA. The granules may undergo a quality control. The granules are packaged in sealed bags or containers. At the same time, samples of the granules are taken and sent to quality control. It should be noted that in the process according to Figure 9, described above, the post-consumer polyolefin-based food grade plastic is inspected to obtain a physical property parameter representative of a melt index of the post-consumer polyolefin-based food grade plastic and is separated based on the physical property parameter, into a plurality of groups, where a respective physical property parameter is assigned to each group of the plurality of groups.

[0139] Furthermore, the polyolefin food grade recyclates placed in the pack are homogenous with respect to the physical property parameter, and each pack is provided with information relating to the physical property parameter of the polyolefin food grade recyclates contained in the pack.

[0140] Thus, the process described above and represented in Figure 9 may be combined with one or more aspects of this disclosure.

[0141] Usually, plastic caps are made from high-density polyethylene (HDPE).

[0142] HDPE can be processed several times without losing its essential properties and can therefore be recycled several times.

[0143] This has been confirmed experimentally. In this context, the Applicant has conducted experiments on HDPE (virgin HDPE) in order to assess the properties of HDPE after 1 or more process cycles.

[0144] In these experiments, the virgin HDPE was subjected to a circular process which comprises: a step of extruding virgin HDPE, a step of compression moulding the extruded HDPE to obtain plastic caps, a step of shredding the plastic caps to obtain plastic flakes from the caps and a step of feeding the plastic cap flakes to the extruder. This cycle is repeated several times. The cycle was repeated between 7 and 20 times. The extruder is fed preferably with 100% flakes. It is also possible, however, to use another percentage of flakes (for example, 50%).

[0145] As may be noted in Figure 4, the viscosity of the HDPE after several process cycles is effectively similar to that of the virgin HDPE. In particular, the graph of Figure 4 shows the viscosity as a function of the shear rate for virgin HDPE and HDPE after 2, 4 and 7 process cycles.

[0146] It may be noted that the lines for different samples of HDPE (virgin, processed 2, 4 and 7 times) are almost overlaid on one another, showing that the viscosity of the HDPE after the aforesaid process cycle does not change.

[0147] The dimensions of the caps were also measured, in particular, the ovality and diameter of caps made from the virgin HDPE and the processed HDPE (1 -7 cycles) and the results (shown in the tables of Figure 5) show that these parameters too remain almost the same throughout the processing of the HDPE.

[0148] It may therefore be concluded that HDPE can be processed many times without losing its main properties (viscosity and dimensions and, in particular, the properties fundamental for the production of plastic caps).

[0149] In another experiment, HDPE flakes were obtained from post-consumer caps belonging to beverage bottles. The caps were collected in Italy and from mixed municipal waste. The caps belonged to beverage bottles (of all kinds). The caps were also collected from cap-only collection points.

[0150] The flakes were then sorted by colour. 100% of the flakes were used in a moulding process to obtain caps from the flakes.

[0151] Environmental stress cracking (ESC) of the caps in CO2 was the measured. For this purpose, the caps were placed on bottles filled with carbonated beverages and the bottles were then placed in storage at 50°C. The results are shown in Figure 6. It may be noted that the caps made from white transparent flakes proved less resistant over time than the red hue flakes.

[0152] The white plastic flakes were mainly from caps used for bottles of water. The red hue plastic flakes were mainly from caps used for bottles of carbonated beverages. Caps for carbonated beverages are made using plastic with high stress cracking resistance properties.

[0153] In an example, the thickness of the cap walls whose stress cracking resistance was measured is increased by approximately 10-20%. In particular, the thickness of the lower (bottom) wall was increased.

[0154] Thus, the experiment showed that the post-consumer plastic keeps its initial properties to a large extent and in this case, the red hue caps provide the post-consumer plastic that is the most promising for the production of beverage caps (and in particular for carbonated beverages).

[0155] It was concluded that HDPE (both virgin and post-consumer) has the potential to be used in a circular process and recycled many times.

[0156] There are, however, factors which may have a significant negative impact on the recycling of HDPE.

[0157] For example, the presence of impurities such as paper and fibres may cause undesirable odours in the HDPE recyclate.

[0158] The impurities may also initiate stress cracking in the caps made from post-consumer HDPE. Moreover, the type of virgin HDPE used to make the caps and the additives used in the cap production process may have an impact on the quality of the caps subsequently made from postconsumer HDPE.

[0159] According to an aspect of this disclosure, the post-consumer polyolefin- based food grade plastic is inspected in an inspection centre IP to obtain a physical property parameter representative of a melt index of the postconsumer polyolefin-based food grade plastic. Preferably, the physical property parameter includes a range for the value of the melt index of the post-consumer polyolefin-based food grade plastic or the exact value of the melt index.

[0160] The melt index of a polymer is a measure of the ease of flow of the molten polymer; it is measured by filling the molten polymer at a given temperature into a heated cylinder to which a smaller cylinder is connected (2.095 mm in diameter and 8 mm in length) which applies a constant force and makes the polymer flow through a capillary; the mass (expressed in grammes) of polymer which flows out in 10 minutes corresponds to the value of the Melt Flow Index. The greater the mass of material that flows out, the higher the Melt Flow Index and the lower the viscosity.

[0161] Furthermore, different groups of the melt index ranges can be provided based on the magnitude of stress cracking, since the magnitude of stress cracking of a polymer is linked to the value of the melt index.

[0162] Stress cracking for thermoplastic polymers is defined as "an external or internal crack in a plastic caused by tensile stresses less than its shortterm mechanical strength".

[0163] For example, a subdivision of the melt index value might be as follows:

[0164] Type 1

[0165] • melt index (2.16 kg 90°C): 0.4-0.85 g / 10 minutes

[0166] • density: 0.95-0.965 g / cmA3

[0167] Tvpe 2

[0168] • melt index (2.16 kg 90°C): 1 .4 - 3.3 g / 10 minutes

[0169] • density: 0.95-0.962 g / cmA3

[0170] Type 3

[0171] • melt index (2.16 kg 90°C): 3.3 - 8.5 g / 10 minutes

[0172] • density: 0.95-0.962 g / cmA3

[0173] A magnitude of stress cracking can be estimated for each of the above- mentioned groups of melt index values. After obtaining the physical property parameter, the post-consumer polyolefin-based food grade plastic is separated into a plurality of groups in a separation centre SP, based on the physical property parameter, where a respective physical property parameter is assigned to each group of the plurality of groups. Each group therefore has a respective melt index range or the same melt index value, and the physical property parameter of each group is different from that of the other groups. The post-consumer polyolefin-based food grade plastic is shredded and then processed in the polyolefin recycler 6. Inspection may be carried out after shredding, hence on the flakes, or after processing the flakes on the polyolefin recyclates (preferably granules), or before shredding. More than one inspection is also possible, before or after shredding and before or after processing the flakes.

[0174] In an example, the physical property parameter is derived through an inspection carried out on the flakes. In an example, the flakes are separated based on colour and the physical property parameter is obtained based on the colour of the flakes.

[0175] In particular, in the plastics industry, it is common practice to associate a colour with a specific application. For example, red is used for plastic used to make caps for carbonated drinks. This application requires high stress cracking resistance and a specific melt index range. In another example, the neutral plastic (HDPE) is used for milk bottles. When possible, therefore, an estimated melt index value (or range) is associated with the post-consumer plastic divided according to colour.

[0176] Accordingly, in one example, the post-consumer polyolefin-based food grade plastic is subjected to an inspection aimed at determining the physical property parameter representative of the melt index. It should be noted that this parameter is not obtained simply based on the color of the plastic, but through an evaluation that, in one example, may also include a correlation between color and physical properties, where such correlation is technically established. As explained above, in certain industrial contexts, a correspondence may exist between color and melt index range, and therefore, in such cases, color may be used as an indicator for estimating the melt index; however, during the step of separating the postconsumer polyolefin-based food grade plastic into a plurality of groups based on the physical property parameter, the plastic is not selected or separated solely based on its color, but rather based on said parameter (melt index).

[0177] The inspection, therefore, is aimed at acquiring a measurable parameter that is representative of the rheological characteristics of the material (in particular, the melt index), which is useful for ensuring a consistent and reliable management of the recycled material. It is specified that the inspection carried out to obtain the physical property parameter representative of the melt index is distinct from any sorting or classification steps that may be performed solely based on the color of the material (either before or after the step of "inspecting the post-consumer polyolefin-based food grade plastic to obtain a physical property parameter representative of a melt index" and "separating the post-consumer polyolefin-based food grade plastic into a plurality of groups based on the physical property parameter, wherein a respective physical property parameter is assigned to each group of the plurality of groups"). In certain applications or process stages, it may indeed be useful or appropriate to carry out a color-based separation of the material, but such operation is independent of and conceptually different from the inspection aimed at obtaining the physical property parameter representative of the melt index of the post-consumer polyolefin-based food grade plastic.

[0178] It is therefore important not to confuse the use of color as an auxiliary indicator for inferring a physical parameter (in cases where a known correlation between color and melt index range exists), with a separation performed directly and solely on the basis of color, without any link to measured or inferred physical parameters.

[0179] Following the inspection, the material is divided into distinct groups, each characterized by a specific value of the physical property parameter. The material selected in this way can be packaged in predetermined quantities, ensuring that, within each container or bag, the granules are homogeneous with respect to the physical property parameter. Such homogeneity is functional to the standardization of the material’s behavior during transformation processes.

[0180] In another example, the post-consumer polyolefin-based food grade plastic before shredding is separated based on the primary application and the physical property parameter is obtained based on the primary application. In other words, when the primary use of the post-consumer plastic is known, a range of the melt index value can be estimated for that plastic, since it is known that each use requires a certain melt index value. Thus, the flakes (or the plastic prior to shredding) are divided into groups based on colour and / or type of polymer and a melt index value (or range of values), for example, medium, high or low, is associated with each group. A stress cracking value may also be associated with a group: for example, the group with the neutral plastic previously used for milk bottles may have a melt index range of between 0.4-0.85 g / 10 minutes and a high stress cracking resistance. Thus, the post-consumer polyolefin-based food grade plastic may be divided according to the colour and / or the source of the plastic.

[0181] In another example, the melt index value of the plastic can be measured before or after shredding or before or after processing in the recycler 6 by conducting a test according to ISO standard 1133-1 .

[0182] Furthermore, after inspection, the flakes are separated in the separation centre SP based on the physical property parameter, into a plurality of subsets, where in each subset the flakes are homogenous with respect to the physical property parameter. The flakes of one subset therefore have the same melt index range, which is different from that of another subset. Moreover, in this example, each subset of the plurality of subsets is processed separately through the polyolefin recycler 6, to obtain a respective plurality of polyolefin food grade recyclate subsets.

[0183] Caps and bottles having the same physical property parameter may be separated and processed together.

[0184] Further, the polyolefin food grade recyclates may be sent to the final inspection unit 7.

[0185] Figures 1A and 1 B illustrate two distinct embodiments in which inspection and separation are carried out on the granules and on the flakes, respectively.

[0186] Also, the flakes are extruded and pelletized to form granules of a food grade polyolefin. A predetermined quantity of food grade polyolefin granules is placed in a pack in a packaging unit. The polyolefin food grade recyclates of the predetermined amount of polyolefin food grade recyclates placed in the pack are homogenous with respect to the physical property parameter. Thus, each pack contains granules having the same melt index range.

[0187] Moreover, a labelling unit provides each pack with information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack.

[0188] This information may be provided in the form of a label or a QR code on the pack.

[0189] The information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack may include information on how the physical property parameter is obtained. For example, the information related to the physical property parameter of the polyolefin food grade recyclates may specify that inspection was based on colour, the source of the plastic, by means of a melt index test, and so on, or that the caps and the bottles were divided and processed separately. The information related to the physical property parameter of the polyolefin food grade recyclates may specify the range or exact value of the melt index of the granules in the bag and an estimate of the stress cracking resistance. Furthermore, the information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack may include operational information representative of the application of the polyolefin food grade recyclates in a moulding process for obtaining a final product from the polyolefin food grade recyclates of each pack as a function of the operating conditions of the moulding process. For example, this information may specify a suggested percentage of the polyolefin food grade recyclates to be used in combination with a virgin polymer. This information may also specify a suggested percentage of the polyolefin food grade recyclates to be used in combination with a virgin polymer for a specific process with specific operating conditions. For example, a pack may provide information (recipes) on the suggested percentage of polyolefin recyclates inside that pack to be combined with a virgin polymer in an injection or compression moulding process for the production of plastic caps having a specific thickness and for carbonated beverages, based on the melt index range associated with that pack. Some example of such recipes are shown in the table below. For each melt index range and as a function of the desired thickness for the cap and the type of beverage, suggested and optimum values of the granules (of recycled HDPE) having that melt index range are provided. Ml is the melt index.

Claims

CLAIMS1. A method for producing polyolefin food grade recyclates, suitable for use in direct contact with food, the method including the following steps:- collecting post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes;- shredding the post-consumer polyolefin-based food grade plastic to obtain flakes;- washing the flakes at a temperature which falls within a range of 55-95eC;- processing the flakes through a polyolefin recycler (6), to obtain the polyolefin food grade recyclates;- inspecting the post-consumer polyolefin-based food grade plastic to obtain a physical property parameter representative of a melt index of the post-consumer polyolefin-based food grade plastic;- separating the post-consumer polyolefin-based food grade plastic, based on the physical property parameter, into a plurality of groups, wherein a respective physical property parameter is assigned to each group of the plurality of groups;- providing a pack and introducing a predetermined amount of the polyolefin food grade recyclates into the pack, wherein the polyolefin food grade recyclates of the predetermined amount of the polyolefin food grade recyclates inserted into the pack are homogenous with respect to the physical property parameter;- providing each pack with information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack.

2. The method according to claim 1 , wherein the physical property parameter is derived through an inspection carried out on the flakes.

3. The method according to claim 2, wherein the flakes are separated based on colour and the physical property parameter is obtained based on the colour of the flakes.

4. The method according to claim 2 or 3, wherein the post-consumerpolyolefin-based food grade plastic before shredding is separated based on the primary application and the physical property parameter is obtained based on the primary application.

5. The method according to any of the previous claims from 2 to 4 comprising the following steps:- separating the flakes, based on the physical property parameter, into a plurality of subsets, wherein in each subset the flakes are homogenous with respect to the physical property parameter;- processing each subset of the plurality of subsets separately through the polyolefin recycler (6), to obtain a respective plurality of polyolefin food grade recyclate subsets.

6. The method according to claim 1 , wherein the physical property parameter is obtained by performing a melt index test on the flakes and / or on the polyolefin food grade recyclates.

7. The method according to any of the previous claims, wherein the information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack includes information on how the physical property parameter is obtained.

8. The method according to any of the previous claims, wherein the information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack includes operational information representative of the application of the polyolefin food grade recyclates in a moulding process for obtaining a final product from the polyolefin food grade recyclates of each pack as a function of operating conditions of the moulding process.

9. The method according to claim 8, wherein the operational information includes information on a suggested percentage of the polyolefin food grade recyclates to be used in combination with virgin polymer.

10. The method according to any of the previous claims, comprising the following steps:- extruding the flakes;- pelletizing the extruded flakes to obtain polyolefin food grade granules.

11. The method according to claim 10 including the following steps:- decontaminating the flakes through a decontamination unit (606B) after the step of extruding and before pelletizing the extruded flakes;- vacuuming the flakes during the step of decontaminating them.

12. The method according to claim 11 , wherein the polyolefin food grade recyclates, before being introduced into the pack, undergo a quality control and wherein one or more operational conditions of the step of decontaminating them are adjusted in response to the step of the quality control.

13. The method according to claim 12, wherein the operational conditions include one of more of the following parameters:- a flow rate at which the extruded flakes are fed to the decontamination unit;- temperature at which the flakes are vacuumed;- the period of time for which the flakes are vacuumed.

14. A post-consumer plastic waste treatment system (1 ) for producing polyolefin food grade recyclates, suitable for use in direct contact with food, comprising:- an input unit (e) to receive post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes;- a shredder (3) configured to shred post-consumer polyolefin-based food grade plastic to obtain flakes;- a washing unit (604), downstream of the shredder, and configured to wash the flakes at a temperature which falls within a range of 55-95eC;- a polyolefin recycler (6) configured for processing the flakes to obtain the polyolefin food grade recyclates;- an inspection centre (IP) for inspecting the post-consumer polyolefin- based food grade plastic to obtain a physical property parameter representative of a melt index of the post-consumer polyolefin-based food grade plastic;- a separation centre (SP) for separating the post-consumer polyolefin- based food grade plastic, based on the physical property parameter, into a plurality of groups, wherein a respective physical property parameter is assigned to each group of the plurality of groups;- a packaging unit (PA) for introducing a predetermined amount of the polyolefin food grade recyclates into the pack, wherein the predetermined amount of the polyolefin food grade recyclates inserted into the pack are homogenous with respect to the physical property parameter;- a labelling unit (LA) for providing each pack with information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack.

15. The post-consumer plastic waste treatment system (1) according to claim 14, wherein the inspection centre (IP) is configured to carry out an inspection on the flakes for obtaining the physical property parameter.

16. The post-consumer plastic waste treatment system (1 ) according to claim 15, wherein at least one of the following conditions is verified:- the flakes are separated based on colour and the physical property parameter is obtained based on the colour of the flakes;- the post-consumer polyolefin-based food grade plastic before shredding is separated based on the primary application and the physical property parameter is obtained based on the primary application.

17. The post-consumer plastic waste treatment system (1 ) according to any of claims 14 to 16 wherein the separation centre (SP) is configured to separate the flakes, based on the physical property parameter, into a plurality of subsets, wherein in each subset the flakes are homogenous with respect to the physical property parameter and wherein the polyolefin recycler is configured to process each subset of the plurality of subsets to obtain a respective plurality of polyolefin food grade recyclate subsets.

18. The post-consumer plastic waste treatment system (1) according to claim 14 wherein the inspection centre (IP) is configured to perform a melt index test on the flakes and / or on the polyolefin food grade recyclates toobtain the physical property parameter.

19. The post-consumer plastic waste treatment system (1 ) according to any of the previous claims from 14 to 18, wherein the information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack includes information on how the physical property parameter is obtained.

20. The post-consumer plastic waste treatment system (1) according to any of the previous claims from 14 to 19, wherein the information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack includes operational information representative of the application of the polyolefin food grade recyclates in a moulding process for obtaining a final product from the polyolefin food grade recyclates of each pack as a function of operating conditions of the moulding process, wherein the operational information includes information on a suggested percentage of the polyolefin food grade recyclates to be used in combination with virgin polymer.

21. The post-consumer plastic waste treatment system (1 ) according to any of the previous claims from 14 to 20 wherein the polyolefin food grade recyclates are in the form of granules.

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