Method and system for obtaining purified plastic material from a mixed waste material stream.

Abstract

This disclosure relates to a method (100) for obtaining purified plastic material (10) from a mixed waste material stream (PS). The method comprises using a near-infrared spectroscopy system to distinguish a first type of plastic material (110a). Separating the first type of plastic material into a first type of plastic material fraction (2) (110b). Reducing the size of the material items in the first type of plastic material fraction (120). Subjecting the first type of plastic material fraction to a washing step (130). Distinguishing the washed first type of plastic material fraction (140a), separating the washed first type of plastic material fraction (140b), thereby obtaining purified plastic material. This disclosure further relates to a system (1) for obtaining purified plastic material (10) from a mixed waste material stream (PS).

Description

Technical Field

[0001] The present invention generally relates to a method for obtaining purified plastic materials from mixed waste material streams. The present invention also generally relates to a system for obtaining purified plastic materials from mixed waste material streams.

Background Art

[0002] Food packaging, bottles, and containers are but one example of products that can be manufactured from plastic. Plastic materials are beneficial as materials due to many beneficial properties, such as being lightweight, water-resistant, and long-lasting. Due to this combination of properties, plastic materials are widely used and required in many industries. However, when plastic materials are released into the natural environment, they cause problems for plants and wildlife. Therefore, it is important that used plastics are collected and sent to disposal sites.

[0003] Typically, plastics that reach disposal sites are sent for incineration, landfill, or recycled by chemical or mechanical processes. These are currently the main techniques used to manage plastic waste. However, there are many problems associated with the management of plastic waste. One problem is that when plastic waste is incinerated, valuable materials are lost and cannot be used further. Another problem associated with the incineration of plastics is that the incineration process generates many products harmful to the human body and the environment, such as carbon monoxide, carbon dioxide, chlorine, and other hydrocarbons. These gases contribute to the problem of global warming. The problems associated with landfilling plastic waste are that it occupies landfill space and is labor-intensive. Furthermore, landfilled plastics tend to release harmful substances over time. Additionally, when disposing of plastic waste, the conversion of waste to energy is not efficient.

[0004] Therefore, recycling is an excellent method for dealing with plastic waste. When recycling plastics, the purity levels of various types of plastics are crucial; otherwise, the quality of the final product will suffer. For example, if the recycled material is a mixture of different materials, such as different types of plastics, it is impossible to achieve high-quality recycled plastic. Therefore, it is extremely important to properly sort plastic waste based on, for example, type and origin. Various processes may be used to sort plastics into different fractions. However, existing processes are generally overly labor-intensive, and the facilities used are not flexible enough to accommodate various conditions. Furthermore, existing processes cannot achieve sufficient purity levels for each type or fraction of plastic. As a result, plastic materials sorted by existing methods generally cannot be used to form virgin plastics during recycling. In other words, recycled plastics are typically of lower quality or purity and cannot be used for the same purpose as before recycling. An example of a material that would be beneficial to use in the same field of application is high-impact polystyrene plastic used in food packaging. There is a need for more precise methods to sort these types of plastic products efficiently and effectively, with high efficiency and while maintaining a high purity level of the resulting fractions. [Overview of the project]

[0005] In view of the foregoing, the object of this disclosure is to provide an improved method for obtaining refined plastic materials from a mixed waste material stream.

[0006] The purpose of this disclosure is also to provide an improved system for obtaining refined plastic materials from mixed waste material streams.

[0007] Furthermore, the objective is to provide solutions that address at least some of the above criteria, namely, solutions that enable the recovery of mixed waste material streams with greater precision or sorting into different fractions to produce desired plastic materials with higher purity levels.

[0008] A further objective is to provide a method for separating several different plastic materials into separate fractions with greater efficiency than other materials.

[0009] To achieve at least one of the above objectives, and other objectives that may become apparent from the following description, the present disclosure provides a method having the steps defined in claim 1. Preferred variations of the method will become apparent from the dependent claims.

[0010] More specifically, according to the first embodiment, a method is provided for obtaining refined plastic materials such as high-impact polystyrene materials from a mixed waste material stream. The method comprises: discriminating a first type of plastic material from other types of material in a material stream using a near-infrared spectroscopic system and / or a visible spectroscopic system; diverting the first type of plastic material from other types of material in a material stream into a first plastic material fraction, thereby separating the material of the first type of plastic material from the material stream; reducing the size of the material items in the first type of plastic material fraction; subjecting the first type of plastic material fraction to an alkaline cleaning step and / or a high-temperature cleaning step; discriminating the first type of plastic material in the cleaned first type of plastic material fraction from other types of material using a near-infrared spectroscopic system and / or a visible spectroscopic system; and diverting the first type of plastic material in the cleaned first type of plastic material fraction from other types of material, thereby separating the other types of material from the cleaned first type of plastic material fraction, thereby obtaining a purified plastic material.

[0011] The method may be advantageous in that a second sorting and separation step is performed after a step of reducing the size of the material in the first type of plastic material fraction and after subjecting the first type of plastic material fraction to a washing step, thereby increasing the purity level of the resulting purified plastic material. The material items in the sorted first type of plastic material fraction may be of mixed types before their size reduction. In other words, the material items or objects in the sorted first type of plastic material fraction may contain two or more types of materials that are bound together before the size reduction of the items. By reducing the size of the material items, different types of materials may be separated from each other, resulting in sorting with greater accuracy and purity in the second sorting and separation step. Furthermore, the washing step may remove stickers, markings, etc., from the material in the first type of plastic material fraction, thereby allowing these to be removed in the subsequent sorting and separation step. Thus, higher purity can be achieved. The first sorting performed in the first sorting and separation step may lead to a reduction in the size of the material, potentially resulting in better outcomes when the second sorting and separation step is performed. Higher purity of the plastic material may lead to higher quality of the final product.

[0012] The input material, i.e., the mixed waste material stream, may originate from a bale of mixed waste material or a bale of plastic material. The material may originate from municipal solid waste, which may have already been sorted at a municipal solid waste facility.

[0013] When distinguishing a first type of plastic material from other types of materials, the distinction may depend on the composition of the first type of plastic material. Alternatively, the type of material may be combined with color, such that the first type of plastic material may be a material of a specific composition having a specific color. Once the first type of plastic material is distinguished, it is separated into a first type of plastic material fraction based on the information from the distinction step. In other words, the separation step separates the already distinguished first type of plastic material. Separation means that the first type of plastic material is separated into a different stream or fraction from the other types of materials. The first type of plastic material may be removed from the mixed waste material stream. Other types of materials may be removed from the mixed waste material stream.

[0014] The material items in the first type of plastic material fraction are subjected to a step of reducing the size of the material items. This step allows the material items to be more exposed and therefore accessible for a cleaning step. In the step of subjecting the first type of plastic material fraction to a cleaning step, the first type of plastic material fraction may undergo an alkaline cleaning step, a high-temperature cleaning step, or a combination thereof. The cleaning step may remove dirt, dust residue, adhesives, and / or labels. The small size of the material items in the first type of plastic material fraction can facilitate the cleaning step. The cleaning step may be adapted to the type of plastic material. By cleaning the first type of plastic material fraction, the purity level of the final product, the refined plastic material, can be further improved.

[0015] Following the washing step, the material items of the washed first type of plastic material fraction are separated again, and the first type of plastic material is separated from the other types of material. The other types of material may be material separated from the first type of plastic material during the sizing step or washing step. The separated first type of plastic material is then separated from the other types of material based on the separation. In this way, the first type of plastic material is separated from the other materials into purified plastic material. Thus, the second step of separation and separation further increases the purity of the first type of plastic material.

[0016] The first type of plastic material may be the first type of high-impact polystyrene material, and as a result, a refined high-impact polystyrene material is obtained.

[0017] High-impact polystyrene materials are economically valuable, especially when they can be sorted into high-purity fractions according to their type. Therefore, suitable methods for sorting high-impact polystyrene materials, as described above for plastic materials, can offer the possibility of material reuse.

[0018] The high temperature during the washing process may be within the range of 30° to 80°, preferably within the range of 40° to 60°.

[0019] The method may further comprise: using a near-infrared spectroscopic system and / or a visible spectroscopic system to distinguish a second type of plastic material from other types of materials in a material stream from which a first type of plastic material has been separated; separating the second type of plastic material from other types of materials in the material stream into a second plastic material fraction, thereby separating the second type of plastic material from the material stream; reducing the size of the material items in the second type of plastic material fraction; subjecting the second type of plastic material fraction to an alkaline cleaning step and / or a high-temperature cleaning step; using a near-infrared spectroscopic system and / or a visible spectroscopic system to distinguish the second type of plastic material in the cleaned second type of plastic material fraction from other types of materials; separating the second type of plastic material in the cleaned second type of plastic material fraction from other types of materials, thereby separating other types of materials from the cleaned second type of plastic material fraction and simultaneously obtaining a second purified plastic material.

[0020] Adding a second sorting and separation step to separate a second type of plastic material can be advantageous because it allows for the simultaneous handling of more types of materials, further improving the efficiency of the method. Separating the second type of plastic material may also improve the recycling rate. The additional step can also reduce the labor intensity of the method because it reduces the need to move materials that are not of the first type of plastic material back through the method in different settings regarding the types of materials being sorted. Another advantage is that the settings regarding the types of materials being sorted and the washing settings do not need to be changed as frequently.

[0021] If the first type of plastic material has already been separated from the mixed waste material stream, typically a step is performed to separate the second type of plastic material from other types of mixed waste material in the material stream. The second type of plastic material, which is separated and separated, typically undergoes a refining process equivalent to that of the first type of plastic material. For example, the first type of plastic material may be white, and the second type of plastic material may be a different color. The settings for each separation step are typically set to suit the respective required type of plastic material. The steps of reducing the material size and subjecting the material to a washing process may also have different settings depending on the type of plastic material. In other words, the settings used for the second type of plastic material may differ from the corresponding settings used for the first type of plastic material. For example, the size may be different, or the temperature may be different.

[0022] The second type of plastic material may be a second type of high-impact polystyrene material, resulting in a second refined high-impact polystyrene material.

[0023] The second type of high-impact polystyrene material offers similar advantages to those described above with respect to the first type of high-impact polystyrene material.

[0024] If one or more further types of plastic materials are to be sorted, the method may be extended to include further distinction and separation steps of the mixed waste material stream. Such further types of plastic materials may be subjected to a purification process substantially equivalent to the purification process of the first or second type of plastic material. In other words, the method may further comprise: using a near-infrared spectroscopic system and / or a visible spectroscopic system to distinguish a further type of plastic material from other types of material in a material stream from which a second type of plastic material has been separated; separating the further type of plastic material from other types of material in the material stream into a further plastic material fraction, thereby separating the further type of plastic material from the material stream; reducing the size of the material items in the further type of plastic material fraction; subjecting the further type of plastic material fraction to an alkaline cleaning step and / or a high-temperature cleaning step; using a near-infrared spectroscopic system and / or a visible spectroscopic system to distinguish the further type of plastic material in the cleaned further type of plastic material fraction from other types of material; separating the further type of plastic material in the cleaned further type of plastic material fraction from other types of material, thereby separating other types of material from the cleaned further type of plastic material fraction and obtaining further purified plastic material.

[0025] As those skilled in the art will understand, the method may be adapted to obtain any required or desired number of plastic materials. By sorting a wider variety of plastic materials, the method can be easily adapted to the sorting systems required in a particular region or country.

[0026] Further types of plastic materials may include further types of high-impact polystyrene materials, resulting in further refined high-impact polystyrene materials.

[0027] The refined plastic material, and if present, the second refined plastic material, may be a food grade plastic material.

[0028] By sorting food grade plastic materials, the materials can be recycled for new food plastic material applications. Materials for food packaging have certain requirements, and thus not all plastics are suitable for use in recycled food packaging. When food grade plastic materials are sorted, the quality of the materials can be guaranteed, making it possible to use the recycled materials for new food applications. Recycled packaging is a desirable product that can potentially reduce environmental impact. Therefore, being able to obtain refined food grade plastic materials can be advantageous.

[0029] The method may further comprise using a near-infrared spectroscopy system and / or a visible spectroscopy system to distinguish a first type of plastic material from other types of materials in a first type of plastic material fraction, and separating other types of materials from the first type of plastic material in the first type of plastic material fraction, thereby purifying the first type of plastic material fraction, before reducing the size of the material items in the first type of plastic material fraction and, if present, a second type of plastic material fraction; and using a near-infrared spectroscopy system and / or a visible spectroscopy system to distinguish a second type of plastic material from other types of materials in a second type of plastic material fraction, and separating other types of materials from the second type of plastic material in the second type of plastic material fraction, thereby purifying the second type of plastic material fraction, if the second type of plastic material fraction is present.

[0030] It may be advantageous for various plastic material fractions to pass through a second discrimination and separation step before the size is reduced, as it is possible to further increase the purity level of the various plastic materials by sorting out materials that may have been mixed into the wrong fractions. The separation step separates other types of materials from the various plastic material fractions.

[0031] The various plastic material fractions may be subject to a number of discrimination and separation steps in order to further purify the various plastic material fractions. As described above, the separation step is performed based on the information from the discrimination step.

[0032] The method may further comprise using a near-infrared spectroscopy system and / or a visible spectroscopy system to distinguish a first type of plastic material and, if present, a second type of plastic material from other types of materials in the material stream from which the first type of plastic material has been separated, or from other types of materials in the material stream from which the second type of plastic material has been separated if the second type of plastic material is present, and separating the first type of plastic material and, if present, the second type of plastic material from other types of materials in the material stream into a recovered plastic material fraction that rejoins the original mixed waste material stream.

[0033] After all types of plastic materials have been separated, it may be advantageous to include a separation and sorting step for materials in the mixed waste material stream. This allows material items of each type of plastic material to be sorted and reintroduced at the start of the mixed waste material stream. Material items of each type of plastic material may not be separated or sorted when they should for various reasons. This may be due to the stacking of material items, which may prevent all materials from being separated, or it may be due to oversight in the sorting step. Therefore, the recycling level of this method is further improved by giving material items that were overlooked in the first step of separation and sorting an additional opportunity to be separated and sorted into the correct type of plastic material. This loop may continue until the material items are correctly sorted. Thus, both the effectiveness and yield of this method are improved.

[0034] By rejoining the recovered material fraction into the initial mixed waste material stream, all types of plastic materials can be transported on a single means of transport, such as a single conveyor belt, or any other type of transport used. This results in a less complex system compared to a system where all types of plastic materials are directly separated into their respective plastic material fractions. This configuration makes it easier to expand the system later, so rejoining the recovered material fraction is still advantageous even when only a first type of plastic material is being separated. Furthermore, in the case of only a first type of plastic material, it is also possible to direct the recovered material fraction into the first plastic material fraction.

[0035] The step of reducing the size of the material items may include crushing the material of a first type of plastic material fraction and, if present, a second type of plastic material fraction.

[0036] Using crushing to reduce the size of material items can be advantageous because it is a well-known and cost-effective method. Crushing may typically be performed by a crusher.

[0037] After the step of reducing the size of the material item, the material item may have a size with a maximum cross-sectional extension that can be 18 mm at most.

[0038] Reducing the maximum cross-sectional length to less than 18 mm can be advantageous because it may increase the success rate of separating different types of plastic materials into refined plastic materials. Size reduction may also facilitate the cleaning process. Size reduction may also increase the likelihood of a single material being present in the material items being reduced in size.

[0039] The purified plastic material, and any second purified plastic material, may have a material purity level of at least 95%, preferably at least 98%.

[0040] A material purity level of at least 95% can be advantageous because it further guarantees the relatively high quality of recycled materials.

[0041] The step of subjecting a first type of plastic material fraction, and a second type of plastic material fraction, if present, to an alkaline cleaning step may further comprise subjecting the first type of plastic material fraction, and a second type of plastic material fraction, if present, to a cleaning solution comprising sodium hydroxide and having a pH of 8 to 13, preferably 9 to 11.

[0042] Alkaline cleaning processes with a pH of 8-13 can be advantageous because they can help remove dirt, labels, and markings from material items. The pH level may be adapted to the type of plastic material being cleaned or the type of material to be removed.

[0043] The method may further include subjecting a first type of plastic material fraction, and a second type of plastic material fraction, if present, to a flotation separation step, thereby separating materials with a density higher than water from materials with a density lower than water.

[0044] The flotation separation process can be advantageous because it can separate lighter materials from denser materials, thereby further improving the purity level of refined plastic materials. Subjecting material items to the flotation separation process also provides an alternative method for sorting different types of materials. Some materials will flotate or sink, thereby sorting the materials based on their density.

[0045] The method may further comprise a washing step of a first type of purified plastic material fraction and, if present, a second type of plastic material fraction, followed by drying the material in the first type of plastic material fraction and, if present, the material in the second type of plastic material fraction.

[0046] Because material items can stick together when wet, it can be advantageous to dry the materials before they enter the final sorting and separation steps. Wet materials tend to stick to each other or to other objects, which can make it difficult to separate the correct material items. By drying the material items, the purity level of the resulting plastic materials can be further increased.

[0047] The method may further comprise at least one of the following: separating ferrous materials from a mixed waste material stream using a magnetic device, and separating non-ferrous materials from a mixed waste material stream using an eddy current separator, before distinguishing the first type of plastic material.

[0048] Considering the value of many iron materials, separating iron materials from mixed waste material streams can be advantageous. By separating iron materials, the materials can be recycled, potentially increasing the profitability of the process. Sorting out iron materials can also lead to a reduction in the amount of material downstream in the mixed waste material stream, which can further simplify the sorting step.

[0049] Considering the value of many non-ferrous materials, separating them from a mixed waste stream can be advantageous. By separating non-ferrous materials, the materials can be recycled, potentially increasing the profitability of the process. Separating non-ferrous materials can also lead to a reduction in the amount of material downstream in the mixed waste stream, which can further simplify the separation step.

[0050] The distinction step may include obtaining the spectra of objects originating from the material stream, and the separation step may include separating the objects originating from the material stream based on the obtained spectra.

[0051] Once the sorting process obtains a spectrum, that spectrum may be compared to a database containing the spectrum, or to a simplified spectrum, or by exclusion, in order to determine which objects should be separated. For example, the database may have a range of spectra considered to be a certain type of plastic material, and if a spectrum matches any of these, that spectrum is separated. Another example is when a simplified spectrum is used, and several properties within the spectral profile are searched, and if the obtained spectrum matches these properties, that spectrum is separated. Objects originating from the material stream may be present in the mixed waste material stream itself, or in a subsequent fraction to be sorted, such as a first type of plastic material fraction or a washed first type of plastic material fraction.

[0052] The method may further comprise separating the mixed waste material stream based on cross-sectional length before distinguishing the first type of plastic material.

[0053] This can be advantageous because material items smaller or larger than a given cross-sectional length can be separated from the outset. Many smaller materials, such as gravel and sand, may be separated from the mixed waste material stream through such sorting. Similarly, material items with larger cross-sectional lengths may also be separated, which can further improve the separation process and prevent larger material items from covering other material items, thereby making their separation impossible.

[0054] The method may further comprise using a wind sieve to separate the mixed waste material stream based on the weight of each object in the mixed waste material stream, before distinguishing the first type of plastic material.

[0055] According to a second aspect, a system for obtaining purified plastic material from a mixed waste material stream comprises a first sorting and sorting device, a material item size reduction device, a washing device, and a purified sorting and sorting device, the first sorting and sorting device comprising a first sorting and sorting station configured to receive a mixed waste material stream, the first sorting and sorting station comprising a near-infrared (NIR) spectroscopy system and / or a visible spectroscopy system configured to distinguish a first type of plastic material from other types of material in the material stream, and a discharge unit configured to separate the first type of plastic material from other types of material in the material stream into a first plastic material fraction, thereby separating the material of the first type of plastic material from the material stream, the material item size reduction device receiving the first plastic material fraction and reducing the size of material items in the first type of plastic material fraction The washing device comprises a first crusher configured as such, a first washing station configured to receive a first type of plastic material fraction from a material item size reduction device and to wash the plastic material fraction in an alkaline washing step and / or a high-temperature washing step, and the purification, sorting and separation device comprises a first purification, sorting and separation station configured to receive the washed first type of plastic material fraction from the first washing device, the first purification, sorting and separation station comprising a near-infrared (NIR) spectroscopic system and / or a visible spectroscopic system configured to distinguish the first type of plastic material from other types of material in the washed first type of plastic material fraction, and a discharge unit configured to separate the first type of plastic material from other types of material, thereby separating other types of material from the washed first type of plastic material fraction, thereby obtaining purified plastic material.

[0056] In general, the features of this embodiment offer similar advantages to those discussed above with respect to prior embodiments of the present invention. The features of the method may be provided to the system individually or in combination. Therefore, to avoid excessive repetition, the features and advantages described above will not be repeated.

[0057] Further applications of the present invention will become apparent from the detailed description given below. However, while the detailed description and specific examples illustrate preferred variations of the concept of the present invention, it should be understood that they are given merely as examples, as various changes and modifications within the scope of the concept of the present invention will become apparent to those skilled in the art from this detailed description.

[0058] Therefore, since devices can vary, it should be understood that the concept of the present invention is not limited to specific components of the described devices. It should also be understood that the terms used herein are solely for the purpose of describing specific modifications and are not intended to be limiting. Note that the articles “a,” “an,” “the,” and “the” used herein and in the appended claims mean that one or more of the elements exist unless the context clearly indicates otherwise. Therefore, for example, a reference to “a unit” or “the unit” may include multiple devices, etc. Furthermore, words such as “equip,” “include,” and “contain” do not exclude other elements.

[0059] The aspects of the concept of the present invention, including its specific features and advantages, will be readily apparent from the following detailed description and accompanying drawings. The figures are provided to illustrate the general structure of the concept of the present invention. Throughout, similar reference numerals refer to similar elements. [Brief explanation of the drawing]

[0060] [Figure 1] This is a flowchart of a system for obtaining refined plastic material from a mixed waste material stream. [Figure 2] This is a flowchart of a system for obtaining refined plastic material from a mixed waste material stream, with additional stations within the system compared to the system in Figure 1. [Figure 3] This is a schematic perspective of the classification and sorting station. [Figure 4] This flowchart illustrates the various steps in a method for obtaining refined plastic material from a mixed waste material stream. [Figure 5] This flowchart shows various steps in a method for obtaining purified plastic material from a mixed waste material stream, which has additional steps in the method compared to the method in Figure 4. [Modes for carrying out the invention]

[0061] The concept of the present invention will be described more fully below with reference to the accompanying drawings showing currently preferred modifications of the concept of the present invention. However, the concept of the present invention may be implemented in many different forms and should not be construed as being limited to the modifications described herein, but rather these modifications are provided for the purpose of thoroughness and completeness and will fully convey the scope of the concept of the present invention to those skilled in the art.

[0062] Figure 1 shows a flowchart of System 1 for obtaining purified plastic material 10 from a mixed waste material stream PS. System 1 comprises a first sorting and separation device 20, a material item size reduction device 30, a washing device 40, and a purified sorting and separation device 50. In the first sorting and separation device 20, the first sorting is performed. The first sorting and separation station 22 within the first sorting and separation device 20 receives the mixed waste material stream PS. The input material, i.e., the mixed waste material stream PS, may originate from a bale of mixed waste material or a bale of plastic material. However, it should be noted that if the plastic material is high-impact polystyrene material, the origin of the material may be from municipal solid waste that has already been sorted at a municipal solid waste facility, or it may be a bale of sorted mixed polystyrene material.

[0063] Referring here to Figure 3, the first sorting and separation station 22 comprises a near-infrared (NIR) spectroscopy system 222 and / or a visible spectroscopy system configured to distinguish a first type of plastic material from other types of materials in the material stream PS, and a discharge unit 224 configured to separate the first type of plastic material from other types of materials in the material stream PS into a first plastic material fraction 2. When distinguishing the first type of plastic material from other types of materials, the distinction may depend on the composition of the first type of plastic material. The type of material may also be combined with color, so that the first type of plastic material may be a material of a specific composition having a specific color. After the first type of plastic material has been distinguished, it is separated into a first type of plastic material fraction 2 based on the information from the distinction. In other words, the first sorting and separation station 22 separates the first type of plastic material that has already been distinguished. In other words, the first sorting and separation station 22 separates a first type of plastic material that has already been distinguished from other materials present in the mixed waste material stream PS. Separation means that the first type of plastic material is separated from other types of materials into a different stream or fraction. The first type of plastic material may be removed from the mixed waste material stream PS, or other types of materials may be removed from the mixed waste material stream PS. Other materials separated from the sorting and separation station are represented by dotted arrows in the figure. All sorting and separation stations in System 1 may be stations of the same type. In other words, there may be multiple stations of the same type in the system. An example of such a station is further described in relation to Figure 3.

[0064] The first type of plastic material fraction 2 is received by the material item size reduction device 30. In the material item size reduction device 30, the size of the material items in the first type of plastic material fraction 2 is reduced. In the illustrated system 1 of Figure 1, the material items are crushed to smaller sizes by the crusher 32 in the material item size reduction device 30. The material items may be crushed to a size where the maximum cross-sectional length can be at most 18 mm.

[0065] The first washing station 42 of the washing apparatus 40 receives a first type of plastic material fraction 2 from the material item size reduction apparatus 30. By crushing the material items, the material items are more exposed and therefore may be accessible for the washing process. Washing of the first type of plastic material fraction 2 may be in an alkaline washing process and / or a high-temperature washing process, as illustrated in Figure 1. The temperature and alkalinity of the washing process depend on the composition of the first type of plastic material fraction 2 and / or the type of material that needs to be removed from the first type of plastic material by washing. The high temperature in the washing process may be within the range of 30° to 80°, preferably within the range of 40° to 60°. The washing solution may comprise sodium hydroxide and have a pH of 8 to 13, preferably 9 to 11. The washing process may be used to remove stickers, labels, etc., from the material items in the first type of plastic material fraction 2.

[0066] Following the washing process, the material items of the washed first type of plastic material fraction 2 are separated again, and the first type of plastic material is separated from other types of material. Other types of material may be materials separated from the first type of plastic material during the sizing process or washing process. The refining sorting and separation apparatus 50 includes a first refining sorting and separation station 52 configured to receive the washed first type of plastic material fraction 2 from the first washing apparatus 40. The first refining sorting and separation station 52 in Figure 1 is of the same type as the first sorting and separation station 22. For the sake of efficiency, how it works will not be repeated and the sorting and separation stations will be described further in relation to Figure 3. The main difference between the first sorting and separation station 22 and the refining sorting and separation station 52 is that the refining sorting and separation station 52 separates other types of material from the washed first type of plastic material fraction 2, thereby obtaining the refined plastic material 10.

[0067] Moving on to Figure 2, an example of System 1 for obtaining refined plastic material 10 from a mixed waste material stream PS is shown, along with further stations within System 1. The stations already described in relation to Figure 1 also form System 1 in Figure 2 and will not be described further in this section. It should be emphasized that the stations within System 1 in Figure 1 are sufficient to work synergistically when sorting the mixed waste material stream PS.

[0068] Figure 2 shows examples of station types that may further constitute part of System 1. A station may form System 1 on its own or in combination with other stations. For ease of understanding, the stations are shown together. The various stations described below may be used individually or in any combination, depending on the requirements of the facility in which System 1 operates.

[0069] System 1 in Figure 2 further comprises a pre-sorting device 60. The pre-sorting device 60 comprises a bale opener 61 configured to open bales from which the mixed waste material stream PS may be derived. The pre-sorting device 60 further comprises a magnetic device 62 configured to separate ferrous materials from the mixed waste material stream PS into a ferrous material fraction 63. Ferrous materials often have high value and can be recycled by separating them, which can further increase the profitability of the system. The pre-sorting device 60 comprises an eddy current separator 62b configured to separate non-ferrous materials from the mixed waste material stream PS into a non-ferrous material fraction 63b. Non-ferrous materials or non-ferrous metals often have high value and can be recycled by separating them, which can further increase the profitability of the system.

[0070] The pre-sorting device 60 further includes a screener 64 that separates material items with a maximum cross-sectional length smaller than a predetermined screen range into a waste fraction 65 and material items with a maximum cross-sectional length larger than a predetermined screen range into a pre-crusher 68. For example, the predetermined screen range may be 20 mm to 320 mm. The pre-crusher 68 of the pre-sorting device 60 crushes the material so that the maximum cross-sectional length is smaller than the upper limit of the predetermined screen range. The crushed material items are then reintroduced into the mixed waste material stream PS.

[0071] The pre-sorting device 60 further includes a wind sieve that separates film material from the mixed waste material stream PS into a film fraction 67.

[0072] In the first sorting and sorting apparatus 20, a second sorting is performed by a second sorting and sorting station 23 that receives a mixed waste material stream PS from the first sorting and sorting station 22. The second sorting and sorting station 23 comprises a near-infrared (NIR) spectroscopy system 222 and / or a visible spectroscopy system configured to distinguish a second type of plastic material from other types of mixed waste material in the material stream PS, and a discharge unit 224 configured to separate the second type of plastic material from other types of material in the material stream PS into a second plastic material fraction 3 (see also Figure 3). In other words, the second sorting and sorting station 23 distinguishes and separates plastic materials that differ from the first plastic material in either composition and / or color. Once the second type of plastic material is distinguished, it is separated into a second type of plastic material fraction 3 based on the information from the distinction. The second sorting and separating station 23 handles the mixed waste material stream PS in the same manner as the first sorting and separating station 22, except that the first type of plastic material has already been separated and the material to be separated and separated is the second type of plastic material.

[0073] As those skilled in the art will understand, if System 1 needs to sort further types of plastic materials, additional sorting and sorting stations may be added to System 1.

[0074] The sorting and separation device 20 further comprises a first purification sorting and separation station 25 and a second purification sorting and separation station 26. Since the first purification sorting and separation station 25 and the second purification sorting and separation station 26 are the same type of stations as the first sorting and separation station 22 and the second sorting and separation station 23, how the stations function will not be repeated.

[0075] The first purification, sorting, and separation station 25 is configured to separate the first type of plastic material and further purify the first type of plastic material fraction 2.

[0076] The second purification, sorting, and separation station 26 is configured to separate the second type of plastic material to further purify the second type of plastic material fraction 3. In other words, the first purification, sorting, and separation station 25 and the second purification, sorting, and separation station 26 are configured to separate other materials from their respective types of plastic material fractions 2 and 3. These steps further increase the purity levels of the first type of plastic material fraction 2 and the second type of plastic material fraction 3.

[0077] The sorting and separating device 20 further comprises a recovery sorting and separating station 24 of the same type as the other sorting and separating stations. The recovery sorting and separating station 24 receives a mixed waste material stream PS from the second sorting and separating station 23 and is configured to separate and separate the first type of plastic material and the second type of plastic material so that these types of plastic material are reintroduced into the mixed waste material stream PS entering the first sorting and separating station 22. Material items of each type of plastic material may not be separated or separated when they should have been separated or separated, i.e., in the early stages of the process, for various reasons. This may be due to material items being stacked or stuck together, preventing all materials from being separated, or it may be due to oversight in the separation step. Therefore, the recycling level of this method is further improved by giving material items overlooked in the first separation and separating step an additional opportunity to be separated and separated into the correct type of plastic material. This loop may continue until the material items are correctly separated.

[0078] Where different apparatus and stations handling the first type of plastic material fraction 2 and the second type of plastic material fraction 3 are described below, only the apparatus and stations handling the first type of plastic material fraction 2 will be described. The second type of plastic material fraction 3 also passes through substantially the same types of apparatus and stations. Figure 2 shows such apparatus only for the second type of plastic material fraction 3. More specifically, the second material item size reduction apparatus 30a, the second washing apparatus 40a, and the second purification, sorting, and separation apparatus 50a are schematically shown in Figure 2.

[0079] The material size of the first type of plastic material fraction 2 is reduced in a material item size reduction device 30 before it enters the washing device 40, as described in relation to Figure 1. The washing device 40 comprises a first washing station 42, as described in relation to Figure 1. The washing device 40 further comprises a density separation station 44. The density separation station 44 receives the purified first type of plastic material fraction 2 from the first washing station 42 and separates the material denser than water from the material less dense than water. The flotation separation process may be advantageous because it can separate lighter materials from denser materials, thereby further improving the purity level of the purified plastic material 10. Subjecting material items to a flotation separation process also provides an alternative method for sorting different types of materials. Some types of materials will flot or sink, thereby sorting the materials based on their density.

[0080] Wet material items from the washing station may tend to stick to each other or to other objects, which can make it more difficult to separate the correct material items. Therefore, a first drying station 46 is added to the washing apparatus 40 of System 1. The first drying station 46 dries the first type of plastic material fraction 2. Drying may be carried out using air circulation and / or high temperature or other known drying methods. The dried material items of the first type of plastic material fraction are then subjected to two sorting steps. The first sorting step is carried out in the first air sieve 48 of the washing apparatus 40, where air is used to separate lighter materials from denser materials by using compressed air to blow away the lighter materials. The first air sieve 48 receives the first type of plastic material fraction 2 from the first drying station 46. The second sorting step is carried out in the first screener 49 of the washing apparatus 40, which sorts the material items based on their cross-sectional size. The first screener 49 receives a first type of plastic material fraction 2 from the first wind screener 48.

[0081] Finally, the purification apparatus 50 receives the first type of plastic material fraction 2 from the washing apparatus 40. The purification apparatus 50 in Figure 2 is substantially the same as the purification apparatus in Figure 1.

[0082] While plastic materials are used throughout the explanation, it should be noted that these plastic materials may be specific types such as high-impact polystyrene, food-grade plastics, or food-grade high-impact polystyrene. The systems described above will function similarly with these types of plastics as well.

[0083] Moving to Figure 3, a schematic perspective view of the sorting and separation station 700 is shown. The first sorting and separation station 22, the second sorting and separation station 23, the recovery sorting and separation station 24, the first washed particle sorting and separation station 25, the second washed particle sorting and separation station 26, and the first purified sorting and separation station 52 may all be of the same type as the sorting and separation station 700 described herein. Each of the stations may have one or more of the features described below. However, for the sake of brevity, the station 700 will be described below as the sorting and separation station 700.

[0084] Material pieces or material items 710 are supplied to the classification and sorting station 700. The material pieces 700 are transported through the detection zone 720. However, the material pieces 700 may be provided through the detection zone 720 by any preferred means or manually without technical means. A light source device 730 and an NIR spectrometer 222 are provided. The spectrometer 222 is adapted to receive and analyze light 732 reflected and / or scattered by the material pieces 710 in the detection zone 720 from the light source device 730. Thus, the NIR spectrometer 222 typically obtains the spectrum of the material pieces 710 from the stream of material being transported through the detection zone 720. The NIR spectrometer 222 of the classification and sorting station 700 is configured to distinguish a first type of plastic material from other materials, such as plastic material, based on the obtained spectrum. In other words, the NIR system 222 is typically configured to distinguish a particular type of plastic material from other types of materials based on its spectrum.

[0085] The sorting and separation station may further include an optical spectroscopy system 760 configured to acquire spectra of plastic materials originating from a material stream PS being transported through a detection zone 720. The discharge unit 224 of the sorting and separation station 700 may further be configured to separate the aforementioned types of plastic materials originating from the mixed waste material stream PS based on the acquired spectra, thereby separating the first type of plastic material fraction based on its color.

[0086] The optical spectroscopy system 760 may determine different colors of the plastic material being transported through the detection zone 720 based on the acquired spectrum. The advantage of determining the color of the plastic material is that the plastic material can be sorted into different fractions.

[0087] The sorting and separation station 700 may further include a laser triangulation system 740 configured to determine height information of material 710 being transported through a detection zone 720. The discharge unit 224 of at least one sorting and separation station may further be configured to separate the plastic material based on the determined height information.

[0088] The laser triangulation system 740 is typically configured to project a laser beam 742 toward the detection zone 720. The illustrated laser triangulation system 740 includes a camera-based sensor device 744 configured to receive and analyze light 746 reflected and / or scattered by material pieces 710 within the detection zone 720. By using the laser triangulation system 740, the sorting and separation station 700 may be able to detect plastic materials that are difficult to detect with the NIR spectroscopy system 222. An example of such plastic material may be black plastic material. By detecting height differences on the conveyor belt used to transport the materials to be sorted, the sorting and separation station may combine its height information with information obtained from the NIR spectroscopy system 222 to determine whether black plastic material or difficult-to-detect plastic material is present on the conveyor belt. Thus, further plastic material may be recycled.

[0089] The sorting and separation station 700 may further include a camera 750 configured to acquire images of plastic materials originating from a material stream being transported through a detection zone 720. The sorting and separation station 700 may also include an artificial neural network in combination with the camera 750. Such an artificial neural network may be configured to detect various properties of the plastic materials being transported through the detection zone 720 based on the images acquired by the camera 750. In this case, the discharge unit 224 of the sorting and separation station 700 may further be configured to separate the plastic materials being transported through the detection zone 720 based on the detected properties of the plastic materials. In other words, the properties of the plastic materials may be determined by the artificial neural network from images acquired by the camera. The properties may be shape, color, surface features, or anything in the appearance of the plastic materials that can be determined and classified by the artificial neural network. The camera 750 may provide the possibility of further separating the material into different fractions. With the help of the artificial neural network, it may be possible to separate plastic materials of the same material composition into different fractions depending on quality and origin.

[0090] Now moving to Figure 4, a method 100 for obtaining purified plastic material 10 from a mixed waste material stream PS is described. Method 100 begins by distinguishing a first type of plastic material from other types of material in the material stream PS using a near-infrared spectroscopic system 222 and / or a visible spectroscopic system 110a.

[0091] Method 100 proceeds to separate the first type of plastic material into a first plastic material fraction 2 from other types of mixed waste material in the material stream 110, thereby separating the first type of plastic material from the material stream.

[0092] Method 100 proceeds to reducing the size of the material item in the first type of plastic material fraction 2 120.

[0093] Method 100 proceeds to subject the first type of plastic material fraction 2 to an alkaline cleaning step and / or a high-temperature cleaning step 130.

[0094] Method 100 proceeds to distinguish the first type of plastic material in the washed first type of plastic material fraction 2 from other types of material using a near-infrared spectroscopic system 222 and / or a visible spectroscopic system 140a.

[0095] Method 100 proceeds to separate the first type of plastic material from other types of material in the washed first type of plastic material fraction 2 140b, thereby separating other types of material from the washed first type of plastic material fraction 2, thereby obtaining the purified plastic material 10.

[0096] It should be noted that the steps or actions in Method 100 described above may be performed in any preferred order and therefore do not have to be in the order given above. Furthermore, one or more of the steps or actions may be performed in parallel. Also, it should be noted that the steps or actions may be performed by different equipment, at different times and / or at different locations. In other words, for example, the method may be performed in a distributed manner at multiple locations where different steps or actions are performed at different times. However, it may be advantageous for the method to be performed at a single location in the order described above.

[0097] Moving to Figure 5, Method 100 from Figure 4 is shown with a set of alternative steps. The alternative steps may be added to Method 100 from Figure 4, either alone or in any combination, depending on the requirements. For the sake of efficiency, steps already described in relation to Figure 4 will not be described again. Method 100 further comprises a step 170 in which ferrous material is separated from the mixed waste material stream PS using a magnetic device 62, preceding the separation step 110a. Method 100 further comprises a step 180 in which non-ferrous material is separated from the mixed waste material stream PS using an eddy current separator 62b, preceding the separation step 110a.

[0098] Following the sorting step 110b, a step 112a is provided in which a second type of plastic material is distinguished from other types of material in the sorted material stream PS using a near-infrared spectroscopy system 222 and / or a visible spectroscopy system.

[0099] Method 100 proceeds to separate the second type of plastic material from the other types of mixed waste material in the material stream PS into a second plastic material fraction 3 112b, thereby separating the second type of plastic material from the material stream PS.

[0100] Method 100 proceeds to distinguish the first type of plastic material and the second type of plastic material from other types of materials in the separated material stream PS using a near-infrared spectroscopic system 222 and / or a visible spectroscopic system 116a.

[0101] Method 100 proceeds to separate the first type of plastic material and the second type of plastic material from the other types of material in the material stream PS into a recovered plastic material fraction 4 which is rejoined with the initial mixed waste material stream PS 116b. By rejoining the recovered material fraction with the initial mixed waste material stream, all types of plastic material can be transported on a single transport means, such as a single conveyor belt.

[0102] The following describes the different steps for processing the first plastic material fraction 2 and the second plastic material fraction 3. For efficiency, the steps are described together. However, it should be understood that these are two different flows, and these steps may be performed in parallel with each other and at different stations.

[0103] Method 100 proceeds to distinguish the first type of plastic material from the other types of materials in the first type of plastic material fraction 2 and the second type of plastic material fraction 3 using a near-infrared spectroscopic system 222 and / or a visible spectroscopic system 113a, 115a.

[0104] Method 100 proceeds to separate the other types of materials from the first type of plastic material in the first type of plastic material fraction 2 and the second type of plastic material fraction 3 113b, 115b, thereby purifying the first type of plastic material fraction 2 and the second type of plastic material fraction 3.

[0105] Method 100 proceeds to subject the first type of plastic material fraction 2 and the second type of plastic material fraction 3 to a flotation separation step 150, 152, thereby separating the material with a density higher than water from the material with a density lower than water.

[0106] The method proceeds to drying the materials in the first type of plastic material fraction 2 and the second type of plastic material fraction 3, 160, 162.

[0107] It should be noted that the steps or actions in Method 100 described above may be performed in any preferred order and therefore do not have to be in the order given above. Furthermore, one or more of the steps or actions may be performed in parallel. Also, it should be noted that the steps or actions may be performed by different equipment, at different times and / or at different locations. In other words, for example, the method may be performed in a distributed manner at multiple locations where different steps or actions are performed at different times. However, it may be advantageous for the method to be performed at a single location in the order described above.

[0108] Furthermore, by examining the drawings, disclosures, and accompanying claims, various modifications of the disclosed modifications can be understood and implemented by those skilled in the art when practicing the claimed invention. In the claims, the word “equipped with” does not exclude other elements, and the indefinite article “a” or “an” does not exclude plurals. The mere fact that certain means are described in different dependent claims does not imply that combinations of these means cannot be used advantageously.

Claims

1. A method (100) for obtaining a refined plastic material (10) such as a high-impact polystyrene material from a mixed waste material stream (PS), Distinguishing a first type of plastic material from other types of materials in the material stream (PS) using a near-infrared spectroscopy system (222) and / or a visible spectroscopy system (110a), The first type of plastic material is separated from other types of material in the material stream (PS) into a first plastic material fraction (2) (110b), thereby selecting the material of the first type of plastic material from the material stream, Reducing the size of the material items in the first type of plastic material fraction (2) (120), The first type of plastic material fraction (2) is subjected to an alkaline cleaning step and / or a high-temperature cleaning step (130), Using a near-infrared spectroscopy system (222) and / or a visible spectroscopy system, distinguish the first type of plastic material in the washed first type of plastic material fraction (2) from other types of material (140a), The first type of plastic material in the washed first type of plastic material fraction (2) is separated from other types of material (140b), thereby separating other types of material from the washed first type of plastic material fraction (2), thereby obtaining the purified plastic material (10). A method (100) comprising:

2. The method according to claim 1 (100), wherein the first type of plastic material is a first type of high-impact polystyrene material, and as a result, a purified high-impact polystyrene material (10) is obtained.

3. Using a near-infrared spectroscopy system (222) and / or a visible spectroscopy system, distinguish the second type of plastic material from other types of material in the material stream (PS) from which the first type of plastic material has been separated (112a), The second type of plastic material is separated from the other types of material in the material stream (PS) into a second plastic material fraction (3) (112b), thereby selecting the second type of plastic material from the material stream (PS), Reducing the size of the material items in the second type of plastic material fraction (3) (122), The second type of plastic material fraction (3) is subjected to an alkaline cleaning step and / or a high-temperature cleaning step (132), Using a near-infrared spectroscopy system (222) and / or a visible spectroscopy system, distinguish the second type of plastic material in the washed second type of plastic material fraction (3) from other types of material (142a), The second type of plastic material in the washed second type of plastic material fraction (3) is separated from the other types of material (142b), thereby separating the other types of material from the washed second type of plastic material fraction (3) and simultaneously obtaining the second purified plastic material. The method according to claim 1 or 2 (100), further comprising the above.

4. The method according to claim 3 (100), wherein the second type of plastic material is a second type of high-impact polystyrene material, and as a result, a second purified high-impact polystyrene material is obtained.

5. The method according to any one of claims 1 to 4 (100), wherein the plastic material (10) and, if present, the second plastic material are food-grade plastic materials.

6. Before reducing the size of the material items in the first type of plastic material fraction (2) and, if present, the second type of plastic material fraction (3) (120, 122), Distinguishing the first type of plastic material from other types of materials in the first type of plastic material fraction (2) using a near-infrared spectroscopy system (222) and / or a visible spectroscopy system (113a), Separating other types of materials from the first type of plastic material (2) (113b), thereby purifying the first type of plastic material fraction (2), If the second type of plastic material fraction (3) is present, Distinguishing the second type of plastic material from other types of materials in the second type of plastic material fraction (3) using a near-infrared spectroscopy system (222) and / or a visible spectroscopy system (115a), Separating other types of materials from the second type of plastic material in the second type of plastic material fraction (3) (115b), thereby purifying the second type of plastic material fraction (3) The method according to any one of claims 1 to 5, further comprising (100).

7. Using a near-infrared spectroscopy system (222) and / or a visible spectroscopy system, distinguish the first type of plastic material and, if present, the second type of plastic material from other types of materials in the material stream (PS) from which the first type of plastic material has been separated, or, if present, the second type of plastic material from other types of materials in the material stream (PS) from which the second type of plastic material has been separated (116a), Separating the first type of plastic material and, if present, the second type of plastic material from other types of material in the material stream (PS) into a recovered plastic material fraction (4) which is rejoined with the initial mixed waste material stream (PS) (116b) The method according to any one of claims 1 to 6, further comprising (100).

8. The method according to any one of claims 1 to 7 (100), wherein the step of reducing the size of the material item (120, 122) comprises crushing the material of the first type of plastic material fraction (2) and, if present, the second type of plastic material fraction (3).

9. The method according to any one of claims 1 to 8 (100), wherein, after the step of reducing the size of the material item (120, 122), the material item has a size having a maximum cross-sectional length of 18 mm at most.

10. The method according to any one of claims 1 to 9 (100), wherein the purified plastic material and, if present, the second purified plastic material have a material purity level of at least 95%, preferably at least 98%.

11. The method according to any one of claims 1 to 10 (100), wherein the step (130, 132) of subjecting the first type of plastic material fraction (2) and, if present, the second type of plastic material fraction (3) to an alkaline cleaning step is further comprising subjecting the first type of plastic material fraction (2) and, if present, the second type of plastic material fraction (3) to a cleaning solution comprising sodium hydroxide and having a pH of 8 to 13, preferably 9 to 11.

12. The method according to any one of claims 1 to 11 (100), further comprising subjecting the first type of plastic material fraction (2) and, if present, the second type of plastic material fraction (3) to a flotation separation step (150, 152), thereby separating a material denser than water from a material less dense than water.

13. After subjecting the first type of plastic material fraction (2) and, if present, the second type of plastic material fraction (3) to the washing step (130, 132), Dry the material in the first type of plastic material fraction (2) and, if present, the material in the second type of plastic material fraction (3) (160, 162) The method according to any one of claims 1 to 12, further comprising (100).

14. Before distinguishing the first type of plastic material (110a), Separating iron material from the mixed waste material stream (PS) using a magnetic device (62) (170), and Separating non-ferrous materials from the mixed waste material stream (PS) using an eddy current separator (62b) (180) The method according to any one of claims 1 to 13 (100), further comprising at least one of the above.

15. The method according to any one of claims 1 to 14 (100), wherein the distinction step comprises obtaining a spectrum of objects originating from the material stream (PS), and the separation step comprises separating the objects originating from the material stream (PS) based on the obtained spectrum.

16. A system (1) for obtaining refined plastic material (10) from a mixed waste material stream (PS), A first classification and sorting device (20), Material item size reduction device (30), Washing device (40), Purification, classification and sorting apparatus (50) Equipped with, The first sorting and sorting apparatus (20) comprises a first sorting and sorting station (22) configured to receive the mixed waste material stream (PS), the first sorting and sorting station (22) comprising a near-infrared (NIR) spectroscopy system (222) and / or a visible spectroscopy system configured to distinguish a first type of plastic material from other types of material in the material stream (PS), and a discharge unit (224) configured to separate the first type of plastic material from other types of material in the material stream (PS) into a first plastic material fraction (2), thereby separating the first type of plastic material from the material stream (PS), The material item size reduction device (30) includes a first crusher (32) configured to receive the first plastic material fraction (2) and reduce the size of the material items in the first type of plastic material fraction (2), The cleaning apparatus (40) includes a first cleaning station (42) configured to receive the first type of plastic material fraction (2) from the material item size reduction apparatus (30) and to clean the plastic material fraction (2) in an alkaline cleaning step and / or a high-temperature cleaning step. System (1), wherein the purification, sorting and separation apparatus (50) comprises a first purification, sorting and separation station (52) configured to receive the washed fraction of the first type of plastic material (2) from the first washing apparatus (40), the first purification, sorting and separation station (50) comprising a near-infrared (NIR) spectroscopy system (222) and / or a visible spectroscopy system configured to distinguish the first type of plastic material from other types of material in the washed fraction of the first type of plastic material (2), and a discharge unit (224) configured to separate the first type of plastic material from other types of material, thereby separating other types of material from the washed fraction of the first type of plastic material (2), thereby obtaining the purified plastic material (10).

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