System and method for producing polyolefin food grade recyclates

Abstract

A polyolefin recycler (6) for a post-consumer plastic waste treatment system (1) for producing polyolefin food grade recyclates, suitable for use in direct contact with food, comprises: an inlet (601) to receive post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes; a shredder (602) configured to shred the post-consumer polyolefin-based food grade plastic to obtain flakes; an inspection unit (605C) configured for inspecting the flakes to obtain a group of flakes formed only of flakes of polyolefin-based, food grade plastic used for beverage purposes; an extruder (606A) configured to extrude the flakes belonging to the desired category; a pelletizing unit (607) configured for transforming the extruded flakes into polyolefin food grade recyclates.

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 differentpolymer 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 thosemethods might not be suitable for contact with food.

[0014] In this context, patent document EP3509811B1 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] Patent document W02024 / 166005A1 , in the name of the same applicant, describes a system for treating post-consumer plastic waste to produce food grade recycled polyolefins, in which plastic containers collected after use are divided into material used for beverage purposes and material used for non-beverage purposes. The beverage-related material is subjected to shredding, washing, and subsequent extrusion and palletization.

[0016] Patent document US2023 / 114094A1 discloses an integrated recycling process for heterogeneous post-consumer plastic waste streams, in which optical sorting and density-based separation techniques are used to divide mixed plastic waste into polyester and polyolefin fractions.

[0017] Patent document WO2023 / 139157A1 relates to decontamination processes for recycled polyolefins, including thermal and vacuum treatments aimed at improving material purity.

[0018] Patent document US11975365B2 discloses sensor-based and optical sorting systems for separating recyclable materials, including plastics, based on detected material properties.

[0019] Silvia Serranti et al., “Characterization of post-consumer polyolefin wastes by hyperspectral imaging for quality control in recycling processes”, Waste Management, vol. 31, no. 11, describes hyperspectral and optical inspection techniques for analysing post-consumer polyolefin waste.

[0020] Moreover, polyolefins tend to easily absorb odours and substances, which are subsequently extremely difficult to remove in order to comply with the limits laid down by EU regulations to meet food safety certification.

[0021] However, prior art systems and method for treating post-consumer plasticwaste to obtain polyolefin food grade recyclates have some disadvantages and can be improved. In effect, there are several needs in this field.

[0022] In particular, there is a need for a post-consumer plastic waste treatment system for producing polyolefin recyclates more efficiently and reliably and capable of producing polyolefin food grade recyclates suitable for use in food safe 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.

[0023] 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.

[0024] Disclosure of the invention

[0025] The aim of this disclosure is to provide a polyolefin recycler, a system and a method for producing polyolefin food grade recyclates to overcome the above mentioned disadvantages of the prior art.

[0026] This aim is fully achieved by the method, system and polyolefin recycler of this disclosure as characterized in the appended claims.

[0027] According to an aspect of it, this disclosure provides a polyolefin recycler. The polyolefin recycler is suitable for use in a post-consumer plastic waste treatment system for producing polyolefin food grade recyclates. The recycler may also be used in other contexts for producing polyolefin food grade recyclates.

[0028] The polyolefin recycler includes an inlet. The inlet is configured to receive post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes. In an example, the inlet may be provided with the polyolefin-based, food grade plastic by the bales of postconsumer plastic containers. In an example, the bales of post-consumer plastic containers are divided into a first group of material and a secondgroup 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.

[0029] The polyolefin recycler includes a shredder. The shredder is configured to shred the post-consumer polyolefin-based food grade plastic to obtain flakes. It should be noted that the polyolefin-based food grade plastic formed of material used for beverage purposes received at the inlet may be (at least partly) already in the form of flakes or it may be unshredded). If the polyolefin-based food grade plastic formed of material used for beverage purposes received at the inlet is already shredded, it may be further shredded inside the shredder of the polyolefin recycler, or if the recycler is not provided with a shredder, the pre-shredded flakes are not further shredded.

[0030] The flake recycler includes an inspection unit. The inspection unit is configured to inspect the flakes. The purpose of inspection is to obtain a property parameter of the flakes.

[0031] The polyolefin recycler includes a separation unit. The separation unit is configured to separate the flakes. The separation unit is configured to separate the flakes based on the property parameter. The separation unit is configured to separate the flakes into a plurality of groups. The plurality of groups includes a first group including desired objects, and a second group including undesired objects. The desired objects category includes flakes of post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes. The undesired objects category includes flakes of post-consumer plastic used for non-beverage purposes and / or of non-plastic materials.

[0032] It should be noted that in an example that is not claimed, separation may be performed only or also on post-consumer polyolefin-based food grade plastic before it is shredded.

[0033] It should be noted that the term "flakes" is only an example of a generic form which the objects (post-consumer polyolefin-based food gradeplastic, in particular after being shredded) may have when they are inspected and separated into the plurality of groups. In effect, the objects which are shredded and inspected do not necessarily need to be flat, since some of the desired objects may be granular.

[0034] Therefore, in all the text of this disclosure, the term "flakes" may be replaced with "shavings".

[0035] The polyolefin recycler includes an extruder. The extruder is configured to extrude the flakes belonging to the desired category.

[0036] The polyolefin recycler includes a pelletizing unit. The pelletizing unit is configured for transforming the extruded flakes into polyolefin food grade recyclates.

[0037] Such a solution provides a reliable and efficient way of obtaining polyolefin food grade recyclates suitable for direct contact with foodstuffs, since it allows having, before processing, a flow of plastic material (through the extruder, for example) which has already been selected by removing from the flow the plastic which has not previously been used in contact with food and / or other materials not suitable for obtaining polyolefin food grade recyclates.

[0038] In view of this, it would seem that a suitably trained vision system could make this selection. Therefore, the material which is processed in the recycler (in particular, the extruder and the pelletizing unit) is material which has been used only for foods (in particular, beverages), thus allowing polyolefin recyclates of food grade quality to be obtained in a reliable manner.

[0039] It should be noted that the PO flakes of the desired category are derived from material previously used only for beverages, and thus does not contain contaminants which make them unfit for direct contact with food and are 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, considering that the post-consumer material used to obtain the polyolefinrecyclates 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.

[0040] Thus, the polyolefin recyclates obtained with this method are very high quality.

[0041] According to one aspect of the present invention, the inspection unit and the separation unit are functionally distinct units and the separation of the flakes is performed as a direct function of the outcome of the inspection. In particular, the inspection unit is connected to the inspection unit, configured for receiving the property parameter obtained by the inspection unit, and for separating the flakes based on this property parameter. In particular, the inspection unit is configured to obtain a property parameter of the flakes, and the separation unit is configured to separate the flakes into a plurality of groups, including desired and undesired objects, based on said property parameter obtained by the inspection unit. The separation is therefore not a mere classification or sorting based on intrinsic material properties alone, but a selection step that acts on the inspection result to physically assign individual flakes to the desired or undesired category prior to downstream processing.

[0042] In an example, the inspection unit includes an optical inspection system configured to capture and analyse one or more images of the flakes.

[0043] In an example, therefore, the inspection performed on the flakes is an optical inspection.

[0044] In an example, the property parameter is representative of the shape of the flakes.

[0045] Inspection based on the shape of the flakes allows avoiding the risk of leaving flakes which are the right material and / or colour to obtain polyolefin food grade recyclates but not the right origin (they have not been used in contact with food or, in particular, with beverages).

[0046] In an example, the recycler includes a polymer separator. In an example, the polymer separator is positioned upstream of the inspection unit. Thepolymer separator is configured to classify the flakes based on the type of polymer.

[0047] In an example, the recycler includes a colour separator. The colour separator is positioned downstream of the inspection unit. The colour separator is configured to classify the flakes based on colour.

[0048] In an example, the desired objects category represents the flakes obtained from plastic caps used for beverages. In an example, the undesired objects category represents the flakes obtained from plastic caps used for purposes other than beverages.

[0049] In an example, the inspection unit is further configured to classify the flakes belonging to the desired objects category based on the features of the plastic caps.

[0050] 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 postconsumer 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 postconsumer plastic containers can be processed through the polyolefin recycler together or separately. It should be noted that the plastic caps are made from polyolefins.

[0051] In an example, the separation unit includes a neural network for extracting features from the images captured by the inspection unit and for assigning each image of the post-consumer polyolefin-based food grade plastic to a group of the plurality of groups.

[0052] In an example, the separation unit includes a first neural network upstream of the shredder and a second neural network downstream of the shredder. In an example, the second neural network is configured to receive data representative of the undesired objects from the first neural network.In an example, the polyolefin recycler includes a decontamination unit. The decontamination unit is configured for decontaminating and purifying the extruded flakes.

[0053] 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 post-consumer plastic waste treatment system is made according to one or more aspects described in Italian patent application 102023000001968 in the name of the present Applicant and totally incorporated by reference in this patent application.

[0054] The system includes an inlet unit. The inlet is configured to receive postconsumer polyolefin-based food grade plastic. The polyolefin-based, food grade plastic is formed of material used for beverage purposes.

[0055] The system includes a polyolefin recycler. The polyolefin recycler is configured for processing post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes to obtain polyolefin food grade recyclates. The polyolefin recycler may be made according to one or more aspects of this disclosure.

[0056] In an example, the inlet of the system may receive bales of post-consumer plastic containers. In such an example, 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.

[0057] In such an example, the shredder is configured to shred the first group of material to obtain plastic flakes.

[0058] 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 (polyolefin) flakes. The second subset may be formed of PET flakes. The second subset may also beformed of other plastic materials. The second subset may therefore comprise flakes that do not include PO. It should be noted that in the sorting unit, the plastic flakes may be divided into more than two subsets. In such an example, the polyolefin recycler is configured for processing the first subset of flakes to obtain the polyolefin food grade recyclates.

[0059] In an example, when the inlet of the system receives bales of postconsumer plastic, 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.

[0060] In an example, the inlet of the system may receive plastic caps used on reusable or refillable beverage bottles. The shredder of the system 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.

[0061] Alternatively, the inlet may directly receive polyolefin-based, food grade plastic formed of material used for beverage purposes which is preselected and thus is not further separated at the inlet. In such an example, the plastic received at the inlet is formed mainly of beverage containers and caps.

[0062] The system includes a washing unit, located downstream of the shredderand configured to wash the flakes at a temperature of between 40°C and 110°C, preferably between 50°C and 100°C, and more preferably between 55°C and 95eC.

[0063] The system may comprise a polyolefin recycler. The polyolefin recycler is configured for processing the flakes to obtain the polyolefin food grade recyclates.

[0064] The system may include 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 may include 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 may include a packaging unit for inserting a predetermined amount of the polyolefin food grade recyclates into a pack. 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. The system may include 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.

[0065] In an example, the inspection centre is configured to carry out an inspection on the flakes to obtain the physical property parameter.

[0066] In an example, at least one of the following conditions is verified:

[0067] - the flakes are separated based on colour and the physical property parameter is obtained based on the colour of the flakes,

[0068] - 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.

[0069] Thus, both of these conditions are verified at the same time or only oneand not the other.

[0070] 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.

[0071] 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.

[0072] 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. According to an aspect of it, this disclosure provides a method for producing polyolefin food grade recyclates. The polyolefin food grade recyclates are produced in a polyolefin recycler. The polyolefin food grade recyclates are suitable for use in direct contact with foodstuffs. The postconsumer plastic waste treatment method is according to one or more aspects described in Italian patent application 102023000001968 in the name of the present Applicant and totally incorporated by reference in this patent application.

[0073] The method comprises a step of collecting post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes. The method comprises a step of shredding the post-consumer polyolefin-based food grade plastic, which is formed of material used for beverage purposes; to obtain flakes therefrom. The method comprises a step of performing an inspection on the flakes to obtain a property parameter thereof. The method comprises a step of separating the flakes into a plurality of groups based on the property parameter. The plurality of groups includes a group of desired objects and a group of undesired objects. The desired objects category includes flakes of post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes. The undesired objects category includes flakes of postconsumer plastic used for non-beverage purposes and / or of non-plastic materials. The method includes a step of extruding the flakes belonging to the desired category. The method includes a step of pelletizing the extruded flakes into polyolefin food grade recyclates.

[0074] In an example, inspection is an optical inspection during which images of the flakes are captured and analysed.

[0075] In an example, the method includes a step of classifying the flakes based on polymer and / or colour. Preferably, the step of performing an inspection on the flakes is carried out after the step of classifying the flakes based on polymer and / or before the step of classifying the flakes based on colour. In an example, the step of performing an inspection is carried out through a neural network that extracts features from the images and assigns each image of the post-consumer polyolefin-based food grade plastic to a group of the plurality of groups.

[0076] In an example, the method comprises a step of separating the postconsumer polyolefin-based food grade plastic through a first neural network before the step of shredding and separating the post-consumer polyolefin-based food grade plastic through a second neural network after the step of shredding. In an example, the second neural network receives data representative of the undesired objects from the first neural network.In an example, the method comprises a step of decontaminating and purifying the extruded flakes.

[0077] The method may comprise a step of washing the flakes at a temperature of between 40-110eC, 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.

[0078] 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.

[0079] The method may comprise 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 post-consumer polyolefin-based food grade plastic. The method may comprise a step of separating the postconsumer 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 may comprise a step of inserting a predetermined amount of thepolyolefin food grade recyclates into the pack. 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. 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.

[0080] 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.

[0081] Thus, the polyolefin recyclates obtained with this method are very high quality.

[0082] 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.

[0083] In an example, the physical property parameter is derived through an inspection carried out on the flakes.

[0084] In an example, the flakes are separated based on colour. The flakes mayalso be divided according to the type of polymer. The physical property parameter may be obtained based on the colour of the flakes.

[0085] 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.

[0086] The flakes may be inspected and divided based both on colour and on primary application or based on only one of these criteria.

[0087] 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.

[0088] 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 ofeach subset have a specific range for the value of the physical property parameter which is the same for all the flakes in that subset.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] The method may comprise a step of extruding the flakes. The method comprises a step of pelletizing the extruded flakes to obtain polyolefin foodgrade granules. Thus, in an example, the polyolefin recyclates are granules of polyolefin recyclates.

[0096] In an example, the method may comprise 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.

[0097] This solution improves the efficiency of decontamination and removes the by-products of decontamination (for example, acetone).

[0098] 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.

[0099] 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.

[0100] The polyolefin quality control may be carried out before or after decontamination.

[0101] 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.

[0102] If the control is carried out after decontamination and the results do not correspond to the predetermined values, the polyolefins undergo another decontamination cycle.

[0103] In an example, the operational conditions include one of more of the following parameters:

[0104] - a flow rate at which the extruded flakes are fed to the decontamination unit;- temperature at which the flakes are vacuumed;

[0105] - the period of time for which the flakes are vacuumed.

[0106] 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.

[0107] The method comprises a step of shredding the first group of material to obtain plastic flakes.

[0108] 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. 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.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 which would make 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.

[0109] Thus, the polyolefin recyclates obtained with this method are very high quality.

[0110] 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.

[0111] The step of processing the first subset of flakes through the polyolefin recycler also includes a step of extruding the first subset of flakes. Morespecifically, 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] In an example, the polymer is classified using near-infrared (NIR) spectroscopy systems. In another example, the polymer may be classified using other technologies.

[0117] 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 ofpreselecting. 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.

[0118] 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.

[0119] 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.

[0120] 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 collectedbelongs 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.

[0121] 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.

[0122] The step of processing the first subset of flakes through the polyolefin recycler may comprise a step of demetallizing the first subset of flakes. The step of processing the first subset of flakes through the polyolefin recycler may comprise a step of washing the first subset of flakes.

[0123] 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.

[0124] 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.Brief description of drawings

[0125] 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:

[0126] - Figure 1 shows a polyolefin recycler according to one or more aspects of this disclosure;

[0127] - Figures 2A and 2B illustrate the steps of producing and separating the polyolefin recyclates according to one or more aspects of this disclosure; - Figures 3A, 3B and 4 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;

[0128] - Figures 5A and 5B illustrate the polyolefin recycler used in the postconsumer plastic waste treatment system;

[0129] - Figure 6 illustrates the post-consumer plastic waste treatment system for producing polyolefin food grade recyclates;

[0130] - Figure 7 illustrates the viscosity of the HDPE after several process cycles;

[0131] - Figures 8 and 9 illustrate the results of experiments conducted on the caps;

[0132] - Figure 10 shows a flow diagram of the polyolefin production line;

[0133] - Figure 11 shows a cross section of the polyolefin production line.

[0134] Detailed description of preferred embodiments of the invention 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 1 for producing polyolefin food grade recyclates suitable for use in direct contact with food ("the system" for short) includes an inlet unit Iwhich receives post-consumer plastic formed of material used for beverage purposes; the inlet unit may also receive 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 inlet unit I separately from the plastic used for non-beverage purposes; thus, in an example, each bale B received at the inlet unit 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 postconsumer material collection centre POC, where empty plastic containers CO are collected after being used by users U. In an example, the inlet unit 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 balesprovide post-consumer 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 which is received by the inlet unit. The post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes is collected in an inlet unit. 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.

[0135] 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 post-consumer polyolefin-based food grade plastic to obtain flakes. The plastic flakes are washed in awashing stage (washing unit) 604. The washing stage reaches high temperatures to remove contaminants from the post-consumer 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.

[0136] Preferably, the flakes are hot washed straight after being shredded.

[0137] 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.

[0138] 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.

[0139] According to an aspect of it, this disclosure provides a polyolefin recycler 6.

[0140] In an example, the system includes the polyolefin recycler 6.

[0141] The polyolefin recycler receives the polyolefin-based, food grade plastic formed of material used for beverage purposes.

[0142] In the example in which the system receives the post-consumer plastic atits inlet 601 , the first subset of flakes is processed in the polyolefin recycler 6 to obtain polyolefin food grade recyclates.

[0143] Otherwise, as explained above, the post-consumer food grade plastic, formed of material used for beverage purposes and / or plastic caps, received at the inlet 601 may be already shredded, partially shredded or not shredded. It should be noted that the polyolefin-based, food grade plastic is formed of material used for beverage purposes may include both the containers and the caps of beverages. In an example, besides the polyolefin-based, food grade plastic formed of material used for beverage purposes, plastic caps may be fed to the inlet 601 together with the postconsumer plastic or separately. 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 R1. 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.

[0144] 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 firstsubset is conveyed to the inlet 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 P1 , 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 homogeneous flakes.

[0145] 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.

[0146] 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.

[0147] 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 polyolefin recycler includes a decontamination unit. The decontamination unit is configured for decontaminating and purifying the extruded flakes. In an example, the refining stage includes a decontamination unit 606B, where the extruded flakes are filtered and purified to remove volatile substances and other contaminants.

[0148] 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.

[0149] The polyolefin recycler 6 includes a pelletizing unit 607, where theextruded 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 (as in the example shown in Figure 3B).

[0150] 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.

[0151] Described below is the process for producing food grade polyolefins according to Figure 11.

[0152] Post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes is collected and shredded in a shredder 3. 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.

[0153] Preferably, the flakes are hot washed straight after being shredded. After hot washing, the flakes undergo a control step, which measures differentflake parameters such as, for example, moisture, polymer type, presence of foreign matter, volatile substances, etc.

[0154] 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.).

[0155] The flakes may be separated according to colour (white, neutral, red, green blue hues).

[0156] 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.

[0157] 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 decontaminationunit, 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.

[0158] In an example, the operational conditions include one of more of the following parameters:

[0159] - a flow rate at which the extruded flakes are fed to the decontamination unit;

[0160] - temperature at which the flakes are vacuumed;

[0161] - the period of time for which the flakes are vacuumed.

[0162] 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.

[0163] 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.

[0164] 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 the polyolefin-based food grade plastic is separated based on the physical property parameter, into a plurality of groups, where a respectivephysical property parameter is assigned to each group of the plurality of groups.

[0165] 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. Thus, the process described above and represented in Figure 10 may be combined with one or more aspects of this disclosure.

[0166] Usually, plastic caps are made from high-density polyethylene (HDPE). HDPE can be processed several times without losing its essential properties and can therefore be recycled several times.

[0167] 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.

[0168] 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%).

[0169] 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.

[0170] 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.

[0171] The dimensions of the caps were also measured, in particular, the ovalityand 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.

[0172] 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). 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.

[0173] The flakes were then sorted by colour. 100% of the flakes were used in a moulding process to obtain caps from the flakes.

[0174] 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.

[0175] 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.

[0176] 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.

[0177] 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). It was concluded that HDPE (both virgin and post-consumer) has thepotential to be used in a circular process and recycled many times.

[0178] There are, however, factors which may have a significant negative impact on the recycling of HDPE.

[0179] For example, the presence of impurities such as paper and fibres may cause undesirable odours in the HDPE recyclate.

[0180] 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.

[0181] The recycler 6 also includes an inspection unit 605C for inspecting the flakes to obtain a property parameter thereof.

[0182] In particular, the polyolefin-based food grade post-consumer plastic formed of material used for beverage purposes is received at the inlet of the recycler either in the form of flakes, hence the first subset, or not shredded. Whatever the case, the plastic received at the inlet 601 is shredded in the shredder 602.

[0183] The flakes which leave the shredder 602 are inspected in the inspection unit 605C. In particular, the inspection performed on the flakes is an optical inspection.

[0184] The inspection is carried out on the basis of the shape of the flakes. Other inspection parameters (for example, colour) are also possible, however. Thus, the flakes are inspected and divided into different groups, so that the flakes whose origin is suitable for the production of polyolefin food grade recyclates, fit for use in direct contact with foods, hence only food safe post-consumer plastic, in particular, used for beverages, are divided and separated from the rest (for example, plastic of other origins, not polyolefin-based, or other undesired objects such as, for example, pieces of straws or pipes. The undesired objects are then rejected and the desired flakes are further processed to obtain the polyolefin recyclates. Preferably, the inspection is carried out after the flakes have beenseparated based on polymer type and before the flakes are separated based on colour. It should be noted that unlike other inspections, separating the flakes does not include a step of rejecting some of the flakes and therefore, this step is preferably after the step of inspecting so as to obtain only the desired flakes. The flakes are classified in a separation unit SP, downstream of the inspection unit IP.

[0185] In an example, the flakes after inspection are divided (separately or in addition to other groups) into two groups: beverage caps (flakes obtained from caps collected and previously used for beverage containers) and non-beverage caps (flakes obtained from caps collected and previously used for containers for non-beverage products). In this case, the flakes of the "beverage cap" group may be further divided into different sub-groups, for example based on the features of the plastic caps. The flakes of the "beverage cap" group are further classified according to one or more of the following characteristic features of the cap, including knurling, tabs, tamper evident strips, etc.

[0186] In an example, after being classified in the inspection unit, the flakes are labelled with information regarding their origin (for example, beverage / non-beverage cap, desired / undesired). It should be noted that the flakes may be divided first into the "desired" and "undesired" groups and then into the beverage cap / non-beverage cap sub-groups, or divided directly into the beverage cap / non-beverage cap groups, or divided only into the "desired / undesired" groups.

[0187] As explained above, inspection is preferably an optical inspection.

[0188] The inspection unit includes an optical device. The optical device captures an image of each object (flakes subjected to inspection) located in an inspection station. In another example, the optical device is configured to capture a plurality of images of each object. In an example, the images captured are of both the front and the rear of each flake, or only of the front or the rear depending on the position of the flake in the inspection station. In an example, the flakes move down an inclined surface providedwith slots and a single flake falls through each slot and is imaged individually. Both sides of each flake may be imaged or only one side. In an example, the optical device includes a camera. The flakes may be fed to the inspection station one by one. In other words, in a preferred embodiment, the flakes are conveyed to the inspection station one at a time. In another example, the flakes may be conveyed to the inspection station in a disordered flow so that more than one object is present in the inspection station at any one time. The inspection unit may also comprise a processing unit which processes each image.

[0189] In an example, the optical device includes one or more emitters to emit electromagnetic radiation towards the flakes in the inspection station. An optical sensor captures the electromagnetic radiation reflected by the flakes in the inspection station and transduces the electromagnetic radiation into corresponding measurement signals. These measurement signals are used to generate the image of the object which is undergoing inspection. The control unit is connected to the optical sensor to receive the measurement signals.

[0190] In an example, the flakes are inspected using a CVS system configured with:

[0191] • Dome illumination, 60 mm radius, (the distance between the bottom of the dome and the capsule must be approximately 40-50 mm)

[0192] • Colour camera, 1920 x 1200 pixel resolution

[0193] • Fixed focus lens, 28 mm

[0194] • PC with I9 processor.

[0195] In an example, each image of the flakes is processed through a neural network.

[0196] Described below is an example of automated classification and separation of plastic flakes using a neural network to distinguish between desired objects and undesired objects (in particular, material used for beverage purposes and material used for other purposes), in addition to identifying and separating any extraneous objects that may be present in the recycledmaterial (post-consumer polyolefin-based food grade plastic received at the inlet and formed of material used for beverages).

[0197] In a test, bags of plastic flakes were collected which had been received from recycling plants and which contained mainly caps used for beverage containers but whose total purity was not guaranteed (e.g. 95%). The contaminants included extraneous bodies such as polystyrene, pieces of oil containers, labels or residues of plastic not classifiable as material used for beverage purposes.

[0198] In a first session, the samples received were analysed using a pre-trained neural network.

[0199] The front and rear of the flakes received were imaged and the images generated were analysed.

[0200] Described below is how the images were analysed.

[0201] We analysed each image through a classification network based on a pretrained neural network model to extract distinctive features of the flakes. The features detected included surface features such as knurling, threads or tamper evident strips, which varied between caps used for beverages and those used for other purposes.

[0202] The network identified and categorized the flakes based on the features detected, distinguishing the caps used for beverage purposes, the caps used for purposes other than beverages and the extraneous bodies (e.g. polystyrene, label remnants).

[0203] We found that the precision of this classification process increases if the impurities are known beforehand, allowing them to be separated more precisely.

[0204] We captured images of the front and rear of the individual flakes of each sample and divided the samples into at least two categories (material used for beverages and material used for other purposes). We tried to divide the material used for beverage purposes into sub-groups, for example, tamper evident strip and other characteristic features of the cap used for beverage purposes.In this example the images of the front and the rear of each flake were analysed separately, for example, if the image of the front of a flake contained the image of a thread, tamper evident strip or knurling, etc., that image was classified in the category of thread, tamper evident strip or knurling and so on, but the front and rear of the same flake were not analysed as a set. Therefore there are two separate datasets for the two sides of each flake to be analysed.

[0205] As explained above, a classification network was used to be able to distinguish between the different categories. In particular, a pre-trained network was used on many images to extract features from each image to enable each category to be determined.

[0206] Therefore, the input to the network includes the images captured for each flake.

[0207] The network then outputs a representation of the data and based on this representation, it is possible to determine the category to which the image can be likened.

[0208] Therefore, the classification of objects used for beverage and nonbeverage purposes is performed on the basis of features extracted from each image. The network classifies the images by considering significant features, if any (knurling, for example, which is used both in material for beverages and in material for non-beverage products, but in two different shapes and sizes) or the shape and colour of the flakes.

[0209] In an example, two neural networks are used, one before and one after shredding.

[0210] For example, a first network operates before the shredder to separate the flakes originating from the caps (or material in general) used for beverage purposes from those used for purposes other than beverages, and a second network operates after the shredder to identify and remove residual extraneous bodies and other impurities.

[0211] The two networks can cooperate, sharing information on the impurities identified, in order to improve the precision of separation.It should be noted that in this example, the neural network is not trained in supervised mode; however, in another example, a machine-learned model might be used to assign each image of the post-consumer polyolefin-based food grade plastic to the desired or undesired category, for example, trained using training data which includes only images of desired objects.

[0212] Described below is an example of flake inspection through the neural network.

[0213] The neural network was used substantially as an extractor of diagnostic indicators to then compare each image data item of a dataset in a working space, where each image data item is illustrated as a data point, and to obtain similarity values.

[0214] For each image of the dataset, the network was used to obtain three most similar images in the dataset.

[0215] Each image has a score which represents a similarity value assigned by the network with respect to the image data of the dataset (the higher the score, the higher the similarity).

[0216] This method allows separating the different categories and assigning high scores to images belonging to the same category.

[0217] A possible criterion for establishing the class of belonging may be to consider the majority class of the 3 (hence at least 2 of 3).

[0218] In an example, inspection and classification are based on the knurling of a beverage cap.

[0219] In this case, the 3 most similar images are 3 images of knurling but differing in colour (in this case, the network is able to discriminate on the basis of the knurling).

[0220] Thus, to assign a class (beverage cap / non-beverage cap) we can consider the majority class, and in this case, we have 3 cases of knurling, and can assign the beverage cap label to the images.

[0221] In another example, the images belonging to a child proof cap are classified.The three most similar images belong to 3 different categories: child proof, child proof ammonia, PP caps.

[0222] In this case, it is not possible to assign one category because there is no majority.

[0223] However, since there are in any case 3 flakes of non-beverage caps, the non-beverage cap label may be assigned to the images.

[0224] A general network therefore can extract the features that can separate the two desired / undesired and / or beverage cap / non-beverage cap categories. In an example, therefore, one neural network was used as feature extractor. For each image (query), the three most similar images in the dataset were identified, based on a similarity score.

[0225] The class of the query image was determined on the basis of the majority class of the three most similar images.

[0226] The interpretation of the results was according to the following criterion: starting from a query image of a flake from a beverage container, if the three images of the dataset with the highest score are also from beverage containers. Similarly, starting from a query image of a flake from a non-beverage container, if the three images of the dataset with the highest score are also from non-beverage containers.

[0227] 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.

[0228] 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 ingrammes) of polymer which flows out in 10 minutes corresponds to the value of the Melt Flow Index.

[0229] The greater the mass of material that flows out, the higher the Melt Flow Index and the lower the viscosity.

[0230] 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.

[0231] 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".

[0232] For example, a subdivision of the melt index value might be as follows:

[0233] Type 1

[0234] • melt index (2.16 kg 90°C): 0.4-0.85 g / 10 minutes

[0235] • density: 0.95-0.965 g / cmA3

[0236] Type 2

[0237] • melt index (2.16 kg 90°C): 1.4 - 3.3 g / 10 minutes

[0238] • density: 0.95-0.962 g / cmA3

[0239] Type 3

[0240] • melt index (2.16 kg 90°C): 3.3 - 8.5 g / 10 minutes

[0241] • density: 0.95-0.962 g / cmA3

[0242] 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 afterprocessing the flakes on the polyolefin recyclates (preferably granules), or before shredding.

[0243] More than one inspection is also possible, before or after shredding and before or after processing the flakes.

[0244] 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.

[0245] 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.

[0246] 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.

[0247] In another example, the melt index value of the plastic can be measuredbefore or after shredding or before or after processing in the recycler 6 by conducting a test according to ISO standard 1133-1.

[0248] 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.

[0249] Caps and bottles having the same physical property parameter may be separated and processed together.

[0250] Further, the polyolefin food grade recyclates may be sent to the final inspection unit 7.

[0251] Figures 2A and 2B illustrate two distinct embodiments in which inspection and separation are carried out on the granules and on the flakes, respectively.

[0252] Also, the flakes are extruded and pelletized to form granules of a food grade polyolefin.

[0253] 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. 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.

[0254] This information may be provided in the form of a label or a QR code on the pack.

[0255] The information related to the physical property parameter of the polyolefin food grade recyclates contained in the pack may include information onhow 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, etc., 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 examples 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.

[0256] Type of Cap Ml 0.4-0.85 Ml 1.4-3.3 Ml 3.3-8.5 beverage thickness

[0257]

[0258] Carbonated < 0.9 mm 100-25% 100-25% 70-10%

[0259] 30-40% 30-50% 5-15% Non< 0.6 mm 90-10% 100-10% 100-10% carbonated 20-40% Up to 100% Up to 100% Carbonated >0.9 and 100-25% 100-25% 100-25% <1.7 100-50% 100-50% 5-20% Non>0.6 100-10% 100-10% 100-10% carbonated Up to 100% Up to 100% Up to 100%

[0260]

Claims

CLAIMS1. A polyolefin recycler (6) for a post-consumer plastic waste treatment system (1) for producing polyolefin food grade recyclates, suitable for use in direct contact with food, the polyolefin recycler comprising:- an inlet (601) to receive post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes;- a shredder (602) configured to shred the post-consumer polyolefin-based food grade plastic to obtain flakes;- an inspection unit (605C) configured for inspecting the flakes to obtain a property parameter thereof;- a separation unit (SP) for separating the flakes, based on the property parameter, into a plurality of groups, including desired and undesired objects, wherein the desired objects category includes flakes of postconsumer polyolefin-based food grade plastic formed of material used for beverage purposes and the undesired objects category includes flakes of post-consumer plastic used for non-beverage purposes and / or non-plastic material;- an extruder (606A) configured to extrude the flakes belonging to the desired category;- a pelletizing unit (607) configured for transforming the extruded flakes into polyolefin food grade recyclates.

2. The polyolefin recycler (6) according to claim 1 , wherein the inspection unit (605C) includes an optical inspection system configured to capture one or more images of the flakes and to analyse images of the flakes.

3. The polyolefin recycler (6) according to claim 2, wherein the property parameter is representative of the shape of the flakes.

4. The polyolefin recycler (6) according to any of the previous claims, comprising a polymer separator (605A), upstream of the inspection unit (605C) and configured for classifying the flakes based on polymer type.

5. The polyolefin recycler (6) according to any of the previous claims,comprising a colour separator (605B), downstream of the inspection unit (605C) and configured for classifying the flakes based on colour.

6. The polyolefin recycler (6) according to any of the previous claims, wherein the desired objects category represents flakes obtained from plastic caps used for beverage purposes and the undesired objects category represents flakes of plastic caps used for non-beverage purposes.

7. The polyolefin recycler (6) according to claim 6, wherein the inspection unit is further configured to classify the flakes belonging to the desired objects category based on the features of the plastic caps.

8. The polyolefin recycler (6) according to any of the preceding claims, wherein the inspection unit includes an optical device to capture one or more images from the flakes and wherein the separation unit includes a neural network for extracting features from the images and for assigning each image of the post-consumer polyolefin-based food grade plastic to a group of the plurality of groups.

9. The polyolefin recycler (6) according to claim 8, wherein the separation unit includes a first neural network upstream of the shredder and a second neural network downstream of the shredder.

10. The polyolefin recycler (6) according to claim 9, wherein the second neural network is configured to receive data representative of the undesired objects from the first neural network.

11. The polyolefin recycler (6) according to any of the previous claims, including a decontamination unit configured to decontaminate and purify the extruded flakes.

12. A post-consumer plastic waste treatment system (1) for producing polyolefin food grade recyclates, suitable for use in direct contact with food, comprising:- an inlet unit (I) to receive post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes;- a polyolefin recycler (6) configured for processing post-consumerpolyolefin-based food grade plastic formed of material used for beverage purposes to obtain polyolefin food grade recyclates, wherein the polyolefin recycler is made according to any of the previous claims.

13. A method for producing polyolefin food grade recyclates, in a polyolefin recycler (6), wherein the polyolefin food grade recyclates are 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, which is formed of material used for beverage purposes, to obtain flakes therefrom;- performing an inspection on the flakes to obtain a property parameter thereof;- separating the flakes, based on the property parameter, into a plurality of groups, including desired and undesired objects, wherein the desired objects category includes flakes of post-consumer polyolefin-based food grade plastic formed of material used for beverage purposes and the undesired objects category includes flakes of post-consumer plastic used for non-beverage purposes and / or non-plastic material;- extruding the flakes belonging to the desired category;- pelletizing the extruded flakes into polyolefin food grade recyclates.

14. The method according to claim 13, wherein the inspection is an optical inspection during which one or more images of the flakes are captured and analysed.

15. The method according to claim 13 or 14, comprising a step of classifying the flakes based on polymer and / or colour, wherein the step of performing an inspection on the flakes is carried out after the step of classifying the flakes based on polymer and / or before the step of classifying the flakes based on colour.

16. The method according to any of the previous claims from 13 to 15,wherein the inspection is performed via a neural network that extracts features from the images and assigns each image of the post-consumer polyolefin-based food grade plastic to a group of the plurality of groups.

17. The method according to claim 16, comprising a step of separating the post-consumer polyolefin-based food grade plastic via a first neural network before the shredding step and separating the post-consumer polyolefin-based food grade plastic via a second neural network after the shredding step, wherein the second neural network receives data representative of the undesired objects from the first neural network.

18. The method according to any of the previous claims from 13 to 17, comprising a step of decontaminating and purifying the extruded flakes.

Images