Method for producing recycled plastic material

Abstract

The invention relates to a method for producing a recycled plastic material, comprising the following method steps: a) producing or providing a starting composition comprising a target plastic in a mass fraction of 90% or higher, based on the mass of the starting composition, said target plastic being selected from the group consisting of polyethylene, polypropylene and polystyrene; b) comminuting the starting composition in a comminuting unit to obtain a particulate plastic material; c) cleaning the particulate plastic material to obtain a cleaned plastic material, where the cleaning comprises washing in a strong scrubber, where the washing in the strong scrubber is performed at a temperature of 60 DEG C or higher, where the cleaning after the strong scrubber comprises rinsing with permeate water, where the washing in the strong scrubber is performed at a temperature of 60 DEG C or higher, and the washing after the strong scrubber is performed at a temperature of 60 DEG C or higher. Wherein the permeate water is produced by purification in a reverse osmosis device; and d) extruding and granulating the purified plastic material to obtain a plastic reclaimed material containing the target plastic.

Description

[0001] manual

[0002] This invention relates to a method for producing plastic recyclables and a purification apparatus for such a method. Plastic recyclables produced using said method are also disclosed.

[0003] Millions of tons of plastic are used globally each year to produce packaging, especially for short-lived products such as food and cosmetics. A large portion of this packaging will eventually become waste.

[0004] Most plastic materials used in packaging today are made from virgin materials, typically comprising 90% or more of the pure raw materials. Currently, only a small fraction of the materials needed in many Western industrialized countries are supplied by so-called recycled materials. These recycled materials primarily come from production waste and are generally cleaner and more homogeneous than product waste that has already been used for its intended purpose. On the other hand, plastics collected and sorted from private households are mainly used in applications where the purity of the plastic (type) is less critical, such as in the construction industry or agriculture.

[0005] Given that a significant portion of plastics (also known as PCR, or "post-consumer recycled materials") exists in plastic products previously used for their intended purpose, there is ongoing interest in enabling these PCR plastics to be used in higher-value applications through suitable recycling methods. Therefore, there is a need to define methods for producing recycled plastic materials that can yield high-quality plastic materials from PCR plastic waste. These materials are particularly clean and sorted by type, making them especially suitable for, for example, the manufacture of new packaging materials.

[0006] Due to the high importance of polyethylene terephthalate (PET) plastic in the plastic packaging industry, efficient recycling methods for PET have been developed in the prior art. However, polyethylene (PE), especially high-density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS), are also important plastic materials in terms of quantity, and for these materials, the existing purification methods and systems, mostly designed for PET, are still considered to require improvement in many cases.

[0007] The main objective of this invention is to eliminate or at least mitigate the disadvantages of the prior art.

[0008] Specifically, the object of the present invention is to provide a method for producing recycled plastic materials, the method being able to obtain particularly clean and pure types of polyethylene, especially HDPE, polypropylene and polystyrene.

[0009] An important objective of this invention is that the prescribed method should also be applicable to the treatment of household plastic waste (PCR), thereby enabling an increase in the recycling rate of the aforementioned plastics in the manufacture of new plastic packaging.

[0010] Another object of the present invention is that the prescribed method should be particularly efficient and economical, so that the pure recycled plastic produced therefrom will be highly accepted in the plastics processing industry due to its favorable material price.

[0011] Another object of the present invention is that the disclosed method should preferably be designed so that the produced recycled plastic material is substantially odorless, i.e., should not have any odor. In this regard, it is also desirable that the disclosed method be able to provide recycled plastic material with precise control over its color and transparency properties, and it is particularly desirable that the specified method also be able to produce substantially colorless and transparent recycled plastic material, especially from PCR plastic waste with uneven color as starting material.

[0012] Another objective of the present invention is to ensure that the method is as environmentally friendly as possible and that the workers employed in the method are exposed to as few health risks as possible.

[0013] Furthermore, the object of the present invention is to provide a purification device that is particularly suitable for the specified method.

[0014] A secondary objective of this invention is to provide advantageous recycled plastic materials that can be produced using the prescribed methods.

[0015] The inventors of this invention have now discovered that, as defined in the claims, the above-mentioned objective can be achieved by combining hot cleaning in a scrubber with rinsing the material using permeate water in a method for producing recycled plastic material.

[0016] The aforementioned objectives are thus achieved through the inventive subject matter defined in the claims. Preferred embodiments of the invention are set forth in the dependent claims and in the following description.

[0017] In particularly preferred embodiments, such embodiments, hereinafter referred to as preferred, are combined with features having other features, also referred to as preferred embodiments. Therefore, combinations of two or more embodiments, hereinafter referred to as particularly preferred, are especially preferred. Similarly preferred embodiments are those in which features of embodiments referred to as preferred to any degree are combined with one or more other features of other embodiments referred to as preferred to any degree. The features of preferred plastic recycled materials and preferred purification equipment derive from the features of preferred methods.

[0018] This invention particularly relates to a method for producing recycled plastic materials, comprising the following steps:

[0019] a) Producing or providing a starting composition comprising, based on the mass of the starting composition, 90% or more by mass of a target plastic, wherein the target plastic is selected from polyethylene, polypropylene, and polystyrene.

[0020] b) Crush the starting composition in a crushing unit to obtain granular plastic material.

[0021] c) Clean the granular plastic material to obtain a purified plastic material.

[0022] The cleaning process includes washing in a high-intensity washer, wherein the washing in the high-intensity washer is performed at a temperature of 60°C or higher.

[0023] The cleaning process following the high-intensity scrubber includes rinsing with permeate water, which is produced by purification in a reverse osmosis unit.

[0024] d) The purified plastic material is extruded and granulated to obtain a recycled plastic material containing the target plastic.

[0025] The method according to the invention is used for producing recycled plastics. In step a), a starting composition comprising a target plastic is first provided. In the context of the method of the invention, the target plastic refers to the type of plastic obtained as the purest (in terms of type) plastic recyclable in the method according to the invention. Those skilled in the art will understand that, for economic and ergonomic reasons, it is suitable to provide a sufficient mass fraction of the target plastic A in the starting composition if a target plastic A is to be obtained, because the high mass fraction in the starting composition directly affects the efficiency of the method. Therefore, a preferred method according to the invention is one in which the starting composition comprises a target plastic with a mass fraction of 92% or higher, preferably 94% or higher, and particularly preferably 96% or higher.

[0026] Those skilled in the art will understand that, since this is a method for producing recycled plastic material, the target plastic is a recycled material. In other words, the method according to the invention is a method in which the starting composition comprises a target plastic in the form of recycled plastic material.

[0027] At least in theory, it is conceivable that excellent results can be achieved by using the method according to the invention to treat plastic waste known as PIR (“post-industrial recycled material”) obtained in industrial environments. However, given the performance of the method according to the invention, for virtually all embodiments, it is preferred to use the method according to the invention to obtain clean and single-type plastic recycled material from more demanding PCR waste. Therefore, the preferred method according to the invention is characterized by a starting composition comprising a target plastic in the form of recycled plastic material from the end-user sector, particularly recycled plastic packaging, and / or a starting composition comprising a target plastic in the form of recycled plastic material from household collection or disposal. The corresponding plastic material is also characterized by the addition of the meaning of “post-consumer recycled material” according to DIN EN ISO 14021:2016-07. In other words, the preferred method according to the invention is a method in which the starting composition comprises a target plastic in the form of recycled plastic material from post-consumer recycled material.

[0028] Preferably, according to the method of the invention, based on the mass of the starting composition, the starting composition consists of 95% or more, preferably 98% or more, particularly preferably 99% or more, of recycled plastic material, and most preferably substantially entirely of recycled plastic material, particularly recycled plastic material collected or processed from the end-consumer sector or household.

[0029] The starting composition used in step a) of the method meets specific minimum requirements for further processing in the method according to the invention, particularly due to the defined mass fraction of the target plastic. In practice, those skilled in the art will adjust the starting composition according to the dosage form to suit the size of the purification equipment used and the downstream purification steps. For example, depending on the region, lightweight packaging bundles, such as those collected from households, may not yet meet the quality desired for further processing by those skilled in the art. Besides an excessively low mass fraction of the target plastic, this may include other aspects such as potentially unsuitable particle size, excessively high concentrations of metallic impurities, and, in particular, insufficient color purity if, for example, there are too many colored plastic components in the bundling material, resulting in an inability to achieve the desired color in the recycled plastic. The inventors have proposed efficient pretreatment methods for efficiently obtaining starting compositions particularly suitable for use in the method of the invention, for example, from bundling materials or other household plastic waste. For this purpose, a preferred method is the method according to the invention, wherein in step a), the starting composition is produced from the precursor composition using a method comprising one or more, preferably several, and particularly preferably all of the following steps:

[0030] a1) Pre-crushing the precursor composition to obtain a pulverized precursor composition, wherein preferably the particle size of the pulverized precursor composition is separated, preferably by a sieving device, wherein the size of the plastic particles in the particle size of the pulverized precursor composition is preferably 10 mm to 380 mm, particularly preferably 20 mm to 350 mm, particularly preferably 30 mm to 320 mm, and / or

[0031] a2) Separating magnetic impurities from the precursor composition or the pulverized precursor composition or the particle size fraction of the pulverized precursor composition, wherein the separation is preferably carried out using a magnetic separator, particularly an overband magnetic separator and / or a drum magnetic separator, and / or

[0032] a3) Use a non-ferrous metal separator to remove non-magnetic metal impurities from the precursor composition or the particle size fraction of the pulverized precursor composition, and / or

[0033] a4) Plastics are sorted from a precursor composition or a pulverized precursor composition or a particle size fraction of a pulverized precursor composition by sensor-based sorting in a sorting device, wherein sensor-assisted sorting is preferably performed using an optical sensor, wherein the optical sensor is particularly preferably an NIR sensor, wherein the sorting is specifically for removing non-target plastics, and optionally, wherein the sorting is also performed based on the color of the plastic.

[0034] The method according to the invention is well-suited for producing recycled polyethylene, polypropylene, or polystyrene plastics. However, based on the inventors' evaluation, the method is particularly effective for processing polyethylene, especially HDPE, and therefore the corresponding design of the method is especially preferred. Thus, a preferred method according to the invention is one in which the target plastic is selected from materials including polyethylene, preferably having a density of 0.94 g / cm³ at 20°C. 3 Or higher than 0.94 g / cm 3 Polyethylene, particularly preferably with a density of 0.94 g / cm³. 3 Up to 0.97 g / cm 3 Polyethylene.

[0035] In step b) of the method of the present invention, the starting composition is first pulverized in a pulverizing unit to obtain granular plastic material. In view of the foregoing, those skilled in the art will understand that the pulverization of the starting composition can begin with a pre-pulverized starting composition to obtain the particle size desired for further processing. In this regard, the inventors have successfully determined particularly suitable particle sizes, using which excellent results can be obtained in downstream processing steps, particularly in high-intensity scrubbers. A preferred method according to the invention is one in which the average particle size D50 of the granular plastic material is 1 mm to 30 mm, preferably 2 mm to 25 mm, and particularly preferably 3 mm to 20 mm.

[0036] According to the inventors' assessment, it is particularly advantageous to perform the pulverization step in such a manner that the granular plastic material is primarily, preferably substantially entirely, in fragment form, which allows for particularly good processing, especially in subsequent high-intensity washing. Therefore, the method according to the invention is preferred, wherein the granular plastic material comprises the target plastic in fragment form.

[0037] The inventors have achieved particularly good results in terms of the quality of the resulting recycled plastic material by underwater pulverization of the starting composition, for example, using a wet cutter. Therefore, a preferred method according to the invention is a method in which the starting composition is pulverized underwater.

[0038] According to the inventors' assessment, the particularly important method step is method step c). In this method step c), the particulate plastic material is cleaned. This cleaning may include several separate cleaning steps, but in any case includes washing the particulate plastic material in a powerful washer at elevated temperatures and rinsing with penetrating water, as further disclosed below.

[0039] According to the inventors' assessment, cleaning particulate plastic materials in a powerful washer is particularly important. The unique feature of the method developed by the inventors is that this washing in the powerful washer is not carried out at room temperature, but at an elevated temperature. Combined with the subsequent post-cleaning with penetrating water described below, this ensures excellent cleaning of the previously pulverized starting composition.

[0040] In this regard, the inventors have successfully determined particularly suitable operating parameters for the temperature in the powerful washer, using which particularly advantageous results can be obtained, especially for polyethylene, particularly HDPE. Preferably, the method according to the invention is used, wherein washing in the powerful washer occurs at a temperature of 65°C or higher, preferably 70°C or higher, particularly preferably 75°C or higher, and especially preferably 80°C or higher. Preferably, additionally, or alternatively, the method according to the invention is preferred, wherein washing in the powerful washer is carried out at a temperature of 60°C to 90°C, preferably 65°C to 85°C.

[0041] The energy required for hot washing can be advantageously obtained, for example, through photovoltaic systems and / or connected block loop heating equipment.

[0042] The method of this invention relies on the use of a powerful washer, which means using specific, dedicated washing equipment for hot washing. This equipment is designed to wash the material to be cleaned at a specified temperature, with a predetermined average residence time, and accompanied by agitation, preferably mechanical agitation. In other words, the powerful washer is designed to enable the washing of granular plastic materials at a specified washing temperature.

[0043] Preferably, the method according to the invention involves washing in a high-intensity washer with an average residence time of 0.5 to 15 minutes, preferably 1 to 10 minutes, which has proven to be particularly advantageous for cleaning as a target residence time. Therefore, the high-intensity washer is particularly preferably designed to wash particulate plastic materials with an average residence time of 0.5 to 15 minutes, preferably 1 to 10 minutes.

[0044] In developing the method according to the invention, the use of particularly advantageous powerful washers in the hot washing module has proven advantageous. The inventors recognized that using powerful washers arranged as vertically as possible, having washing chambers much steeper than those in conventional washing lines, is particularly advantageous. Therefore, it is preferred that the powerful washers according to the invention be substantially, preferably entirely, vertical, and / or that the powerful washers have washing chambers in which the longitudinal direction of the washing chambers forms an angle of 80° to 90°, preferably 85° to 90°, with the horizontal plane.

[0045] In a powerful washer that the inventors have determined to be particularly advantageous for the method of the invention, which is as vertical as possible, unlike many powerful washers known in the prior art, the particulate plastic material is introduced into the upper inlet of the powerful washer relative to the direction of gravity, such that the particulate plastic material is guided through the powerful washer by gravity. Therefore, it is preferred to use the method according to the invention, wherein the powerful washer has a washing chamber, wherein the washing chamber includes an inlet for the particulate plastic material in an upper region (preferably in the upper third, particularly preferably in the upper quarter, and most preferably in the upper fifth), and an outlet for the particulate plastic material in a lower region (preferably in the lower third, particularly preferably in the lower quarter, and most preferably in the lower fifth, especially at the lowest point of the washing chamber). Preferably, additionally, or alternatively, it is the method according to the invention, wherein the particulate plastic material is introduced into the washing chamber of the powerful washer in the upper region relative to the direction of gravity, and after washing in the powerful washer, is discharged from the washing chamber in the lower region.

[0046] Combined with vertical arrangement, this design creates a thermal washing module designed so that granular plastic material is introduced into the upper part of the powerful washer and forms a column of material within the washer. This column of material creates a pressure gradient within the container, which can be controlled by the fill level and increases with increasing packing density at the bottom of the container. The granular plastic material is agitated and kept in slow motion within the powerful washer, preferably by agitation arms, causing the surfaces of the plastic particles to mechanically rub against each other. This gentle frictional effect achieves a gentle yet powerful cleaning of the material, resulting in minimal material loss within the fine particle size range.

[0047] For hot washing in a high-powered scrubber, the inventors suggest that a washing solution can be preferably used, which, in addition to water, may contain an alkaline compound and / or a surfactant compound for adjusting the pH value. Particularly preferred is the use of a surfactant compound in addition to water, adjusting the pH value of the washing solution to 7 to 8, preferably 7 to 7.5. The amount and composition of the washing solution, particularly regarding the ratio of the alkaline compound and / or surfactant compound, are preferably controlled according to demand and time, such that, for example, the content of the alkaline compound can be adjusted to the pH value of the water used or controlled according to the pH value of the wastewater. In view of the foregoing, a preferred method according to the invention is: where washing in the high-powered scrubber is carried out using a washing solution, wherein, based on the mass of the washing solution, the washing solution comprises:

[0048] (ic) water,

[0049] And others

[0050] ii.c1) One or more basic compounds, wherein the basic compound is preferably selected from sodium hydroxide and potassium hydroxide, and / or

[0051] ii.c2) One or more surfactant compounds, wherein the surfactant compound is preferably selected from anionic surfactants.

[0052] Between the pulverization of the starting composition, such as in a wet cutting mill, and the high-intensity washer, one or more further cleaning steps can be inserted as part of the cleaning process. In particular, the inventors suggest that using a friction washer after the pulverization unit can produce pre-cleaned granular plastic material, which can be further purified particularly efficiently in the subsequent high-intensity washer. The concept of friction washer is known to those skilled in the art from the prior art, and friction washer is commercially available from various suppliers. Such friction washer is typically used to clean pulverized material fractions and to convey the pulverized material against gravity in an inclined washing chamber via a helical shaft, wherein particularly small impurities are removed along with the washing water by a screen inserted into the friction washer. Therefore, it is preferable that the method according to the invention includes cleaning in the friction washer prior to the high-intensity washer.

[0053] Another particular feature of the method of the present invention is that, in step c), conventional fresh water is not used for post-washing; instead, the material obtained from the powerful washer is rinsed with permeate water, if necessary, after further intermediate washing or density separation. A preferred method according to the invention is characterized by rinsing with permeate water immediately after washing in the powerful washer, or immediately after density separation downstream of the powerful washer, in the latter case rinsing the target fraction.

[0054] Permeate water, as is commonly known to those skilled in the art, refers to very pure water that can be produced by reverse osmosis. This is a method known to those skilled in the art, in which osmotic pressure can be overcome by applying pressure and using a semi-permeable membrane, thereby obtaining purified water with reduced content of dissolved impurities, particularly salts and suspended solids. Using permeate water allows for more effective rinsing of granular plastic materials and prevents undesirable cross-contamination between the washed plastic material and contaminated process water. While not wishing to be bound by this theory, the inventors hypothesize that permeate water with low saturation levels of salts and other impurities has a beneficial effect on removing such substances from the granular plastic material to be washed. The inventors recognize that particularly good results can be achieved in subsequent rinsing stages when using a powerful reverse osmosis system capable of providing permeate water with low impurity content. According to common practice in the art, this is characterized in particular by the conductivity and pH value of the obtained permeate water.

[0055] Preferably, the method according to the invention has a conductivity of 5 µS / cm or less at 25°C, preferably 4 µS / cm or less, particularly preferably 3 µS / cm or less, particularly preferably 2 µS / cm or less, and especially preferably 1 µS / cm or less. However, for economic reasons, the method according to the invention is also preferred, or alternatively, the conductivity of the permeate at 25°C is 200 µS / cm or less, preferably 150 µS / cm or less, particularly preferably 120 µS / cm or less, wherein the conductivity is measured, for example, according to DIN EN 27888 (C8) 1993-11.

[0056] Preferably, additionally, or alternatively, the method according to the invention is wherein the pH of the permeate water is 4 to 6, preferably 4.5 to 5.5. Preferably, additionally, or alternatively, the method according to the invention is wherein the pH of the permeate water is 7.5 or lower, wherein the pH value can be measured, for example, according to DIN EN ISO 10523 (C5) 2012-04.

[0057] Preferably, additionally, or alternatively, the method according to the invention is wherein the dH value (German hardness) of the permeate water is 3°dH or less, preferably 2.5°dH or less, particularly preferably 2°dH or less. Preferably, additionally, or alternatively, the method according to the invention is wherein the dH value (German hardness) of the permeate water is 5°dH or less, preferably 4.5°dH or less, particularly preferably 4.0°dH or less, wherein the dH value can be measured, for example, according to DIN EN ISO 17294-2 (E29): 2017-01.

[0058] While it is theoretically conceivable that permeate water for the method according to the invention could be simply obtained, for example, by purchasing it from a supplier, it is preferable to produce permeate water within the framework of the method of the invention using a suitable reverse osmosis system for the most economical and ecological process management possible. Therefore, a preferred method according to the invention involves the immediate production of permeate water before and / or during step c) of the method.

[0059] The inventors suggest that, especially when particularly high purity is required, multiple rinsing steps with permeate water can also be provided. In this case, the preferred method according to the invention is that the cleaning in step c) includes one or more, preferably two or more, further washing and rinsing with water, preferably with permeate water.

[0060] Since rinsing with permeate water according to the invention yields correspondingly pure permeate water, as another embodiment, such pure permeate water can be used that has already been used in high-intensity scrubbers or even in possible wet cutting and grinding machines. According to the inventors' assessment, this could potentially bring further advantages in terms of the purity of the achievable granular plastic material. However, these improvements in purity are offset by the increased cost and production capacity requirements of the system used to produce the permeate water; therefore, according to the inventors' assessment, this configuration will primarily be relevant to selected high-performance applications. Preferably, the method according to the invention includes rinsing with permeate water in the high-intensity scrubber.

[0061] To achieve particularly advantageous cleaning performance, the inventors suggest that density-based separation of impurities and other plastics should also be performed in method step c). This separation stage for separating floating and sinking plastics achieves several advantageous functions. On the one hand, it results in additional separation of various plastics according to their type; on the other hand, it provides additional buffering against detergents or alkaline compounds that are rinsed away. Advantageously, particulate plastic material can be removed from this separation stage by a dehydration check, which has the advantage of minimizing the carryover of alkaline compounds or detergent components. This also significantly reduces the amount of freshwater used after the cleaning process. By actively controlling this separation stage, for example by removing floating or sinking fractions, the purification equipment used can be advantageously and flexibly adapted to the processing of different plastic materials. Preferably, the method according to the invention includes density-based separation of impurities and non-target plastics in method step c), preferably based on their floating or sinking behavior in water, wherein the target plastic particles are preferably removed from the water container by a dehydration screw conveyor. The method according to the invention is particularly preferred in which the removal point of the target plastic particles removed from the density-based separation is changed according to the target plastic, particularly the target plastic between the floating fraction and the sinking fraction.

[0062] The purified plastic material obtained from rinsing with permeate water in step c) can advantageously be dried and then removed from residual impurities, which have been separated from the plastic particles in the vigorous scrubber but not removed from the purified plastic material in subsequent rinsing and purification steps, by a suitable separation process, such as air separation or sieving. Therefore, it is preferred to use the method according to the invention, wherein cleaning in step c) includes drying the purified plastic material, preferably by mechanical drying and / or thermal drying, particularly preferably by mechanical drying and thermal drying. Preferably, additionally, or alternatively, it is the method according to the invention, wherein cleaning in step c) after drying includes separating excessively small and / or light components from the purified plastic material, preferably by air separation and / or sieving.

[0063] The inventors suggest that further downstream sorting steps can be performed after the dried and purified plastic material. This step is particularly desirable, for example, when a particularly high color purity is required, such as for producing transparent or colorless granules, or when the starting material is particularly heavily contaminated by other plastics. For this downstream sorting step, the inventors believe that radiation-based or optical sorting methods are particularly effective, such as infrared-based methods. Near-infrared methods are particularly suitable for identifying particles with undesirable colors and / or chemical compositions in the purified plastic material. Particles identified in this way can be separated using suitable methods, such as by a robotic system or by an air gun.

[0064] The purified plastic material obtained in step c) is then extruded and granulated in step d) to obtain the desired recycled plastic material in an easily processable form. The concept of plastic extrusion is well known to those skilled in the art. Suitable equipment for this purpose is called an extruder and is commercially available from various manufacturers. The inventors have successfully determined particularly suitable extrusion temperatures, which yield particularly advantageous results in the method according to the invention, especially when combined with additional purification of the liquefied plastic material in the extruder as disclosed below. A preferred method according to the invention is characterized by extrusion being carried out at a temperature of 230°C to 300°C, preferably 240°C to 280°C.

[0065] According to the inventors, it is particularly advantageous if the plastic material is not simply conveyed through an extruder for granulation, but rather its liquefaction is utilized in a synergistic manner by a filter installed in the extruder to produce an additional cleaning effect. For this purpose, a fine-mesh screen can be used, preferably with a pore size of 75µm to 200µm, more preferably 100µm to 150µm. The plasticized material can be extruded through a suitable fine-mesh screen to trap impurities. A preferred method according to the invention is characterized by filtering the liquefied plastic material in the extruder before granulation, preferably by a laser filter.

[0066] Furthermore, a vacuum stage can advantageously be provided in the extruder, which helps to further reduce odor by removing volatile substances. A preferred method according to the invention includes one or more, preferably two or more, vacuum stages in the extruder for extruding and granulating the purified plastic material.

[0067] The inventors have recognized that underwater granulation as part of the method of the invention yields optimal results. In a particularly advantageous embodiment, this underwater granulation is not carried out in ordinary water, but rather in the permeable water already disclosed above. This brings particularly advantageous characteristics to the granulation process and yields the desired recycled plastic pellets with exceptionally high purity. The preferred method according to the invention is a method characterized by granulation of the purified plastic material via underwater granulation, preferably in permeable water.

[0068] One advantage of the method according to the invention is its ability to be efficiently automated, thereby achieving a substantially continuous process, which is particularly desirable from an economic point of view. Therefore, a preferred method according to the invention is a method characterized by being continuous or semi-continuous. Additionally or alternatively, a preferred method according to the invention is a method characterized by being controlled by an electronic data processing device.

[0069] The inventors suggest that plastic materials can be advantageously conveyed between the various workstations of the method according to the invention using screw conveyors, particularly considering the good controllability and economical and ecological process management, at least when the material is wet. For granular plastic materials produced according to the method of the invention, especially in fragment form, transport by vacuum conveying is particularly preferred. Using screw technology eliminates the need for centrifuges, which would otherwise require drying the material between units. Screw technology also reduces the formation of fine or small particles in the abrasive material due to fine wear and contaminants carried between different units. Preferably, the method according to the invention involves the target plastic being conveyed, at least partially, preferably primarily, and particularly preferably substantially entirely, between the various workstations of the method using screw conveyors, pressure conveyors, or vacuum conveyors, preferably screw conveyors, relative to the conveyor line.

[0070] One advantage of the method according to the invention is its ability to efficiently integrate water treatment. In a synergistic manner, it is even possible to use a preferably provided reverse osmosis system to fractionate certain wastewater to particularly high purity. However, in the inventors' view, considering the purity of the permeate and the maintenance requirements of the reverse osmosis system, it is preferable not to use the wastewater generated in the water treatment process to produce permeate, but rather to return it to, for example, a wet cutter, any friction scrubber and / or pre-scrubber upstream of a high-intensity scrubber, or only in the high-intensity scrubber or density separation, and to use fresh water to produce permeate. Preferably, according to the method of the invention, the wastewater generated in method steps b) and c) is treated by a water treatment device, preferably a water treatment device, wherein the treated wastewater is preferably returned to method steps b) and c) with a recovery rate of 80% or higher, preferably 85% or higher, particularly preferably 90% or higher.

[0071] In view of the above disclosure, those skilled in the art will understand that the present invention also discloses plastic recycled materials produced or producible according to the method of the present invention.

[0072] Furthermore, the present invention also relates to a purification apparatus for use in the method according to the present invention, comprising:

[0073] i) A grinding unit for grinding the starting composition,

[0074] ii) A powerful washer for cleaning particulate plastic materials at temperatures of 60°C or above.

[0075] iii) Reverse osmosis equipment used to produce permeate water, and

[0076] iv) Extruders used for extruding and granulating purified plastic materials.

[0077] Preferred embodiments of the purification devices according to the present invention are derived from preferred methods according to the present invention, and these preferred purification devices are designed to perform these preferred methods.

[0078] In this regard, a purification device according to the present invention is particularly preferred, wherein the purification device further comprises:

[0079] v) Pre-crushing unit, and / or

[0080] vi) Screening equipment, and / or

[0081] vii) One or more magnetic separators, and / or

[0082] viii) One or more non-ferrous metal sorting machines, and / or

[0083] ix) Sorting equipment for sensor-assisted sorting, wherein the sorting equipment preferably includes one or more optical sensors, particularly preferably NIR sensors.

[0084] Preferably, additionally, or alternatively, the purification device according to the invention is a wet cutting and grinding machine.

[0085] Preferably, additionally, or alternatively, the purification device according to the present invention further includes:

[0086] x) A friction washer, wherein the friction washer is preferably arranged between the pulverizing unit and the high-intensity washer, and / or

[0087] xi) A pre-washer, preferably used for pre-cleaning before the high-powered washer, and / or

[0088] xii) A separation stage for separating floating and sinking plastics, preferably including a dewatering screw conveyor.

[0089] Preferably, additionally, or alternatively, the purification device according to the invention further includes:

[0090] xiii) Drying equipment, including means for mechanical drying and / or thermal drying.

[0091] Preferably, additionally, or alternatively, the purification device according to the invention further includes:

[0092] xiv) An air classifier and / or screening equipment located downstream of the drying equipment.

[0093] Preferably, additionally, or alternatively, the purification device according to the invention further includes:

[0094] xv) Electronic data processing equipment used to control the device.

[0095] Preferably, additionally, or alternatively, the purification device according to the invention further includes:

[0096] xvi) Multiple spiral conveyors arranged between the components of the purification equipment.

[0097] The present invention and its preferred embodiments are explained and described in more detail below with reference to the accompanying drawings. The drawings show:

[0098] Figure 1 A schematic diagram of some method steps of method step a) according to the preferred embodiment of the present invention;

[0099] Figure 2 A schematic diagram of the sub-method steps of method steps b) and c) according to the preferred embodiment of the method of the present invention; and

[0100] Figure 3 A schematic diagram of a sub-step of method step d) according to the preferred embodiment of the present invention.

[0101] Figure 1 , Figure 2 and Figure 3 A particularly preferred method for producing recycled plastic material using the purification equipment according to the present invention is illustrated in the form of a process diagram. Method step a) is shown in... Figure 1 Method steps b) and c) are shown in Figure 2 Method step d) is shown in Figure 3 These method steps are each divided into sub-method steps of the preferred process sequence, and the process direction is indicated by the arrows shown.

[0102] Figure 1 This illustrates how a precursor composition, for example, consisting of HDPE bales collected or processed from a household, is transformed into a starting composition. In sub-step 102, the bale material is fed into a pre-grinding mill, followed by sieving with a flat sieve in sub-step 104, where particle sizes from 30 mm to 320 mm are separated. Then, before transferring the composition to a non-ferrous metal separator, the metallic components of the plastic material are cleaned in sub-step 106, using a combination of belt and drum magnetic separators to separate the magnetic components. Subsequently, in sub-step 108, the material is optically analyzed using NIR / VIS process technology to sort the material based on its color characteristics and remove foreign plastics. Figure 1 In the exemplary method shown, a starting composition is produced, which, in the example shown, has a purity greater than 94% for the color and material of HDPE. In sub-step 110, the material obtained in this manner is bale-packed using a bale press for ease of handling before storage and further processing.

[0103] exist Figure 2 In China, according to Figure 1 The resulting starting composition, possibly combined with other pre-sorted HDPE bundles, is fed into a wet cutter in sub-step 202 to obtain granular plastic material. This granular plastic material is then fed into an inclined friction washer in sub-step 204.

[0104] Then, in sub-step 208, any remaining heavy particles are separated in a heavy object trap, which also serves as a buffer container. A pre-washing process is then performed in sub-step 210, where wastewater from the pre-washing in sub-step 210, as well as wastewater from the friction washer and wet cutter, can be conveyed to process water treatment 206, from which the treated water can be returned to the wet cutter or pre-washer.

[0105] Following the pre-wash in sub-step 210 is the high-intensity wash in sub-step 212, in which the particulate plastic material is cleaned at a temperature of approximately 80°C and a residence time of 1 to 10 minutes.

[0106] The cleaned granular plastic material obtained from the high-intensity scrubber is then subjected to density separation, wherein in the corresponding sub-step 214, a floating fraction is selected to separate residual non-target plastics, such as polystyrene, that have aggregated in the settling fraction, and then the material is cleaned again in the post-scrubber of sub-step 216. As part of the post-scrubber of sub-step 216, rinsing is performed using permeate water continuously produced in the reverse osmosis unit during the method.

[0107] Subsequently, in sub-step 218, the fragments obtained in this manner are dried, wherein mechanical drying is followed by thermal drying. In sub-step 220, the material dried in this manner is further separated by an air classifier and a fine sieve to remove lightweight materials and fine particles with a diameter less than 2 mm. In sub-step 222, spectroscopic techniques, particularly NIR, are again used to sort out components that are undesirable in terms of color and / or material.

[0108] according to Figure 2 The material obtained at the end of the sub-step can then be fed into the extrusion and granulation process. The corresponding method step d) is in... Figure 3 The process is visualized in the following steps. In sub-step 302, the previously purified plastic material is conditioned in a smart feeder, then melted in an extruder (plasticizing extruder), and filtered through a laser filter to remove further impurities as production waste. The filtered material is then further processed in a vacuum extruder, as shown in sub-step 304. After this vacuum extrusion, granulation is performed in sub-step 306, preferably using permeate water. Extrusion can also be performed directly in a single-screw extruder or similar granulation technology without preconditioning, wherein the laser filter is preferably connected upstream of the granulation. The HDPE recycled plastic material obtained in this manner is packaged in sub-step 308 and, at the end of the entire process, can be sold as a high-performance material, particularly suitable for manufacturing packaging materials or final packaging, especially in the fields of beauty care, cosmetics, and cleaning products, where a purity exceeding 99.6% in both material (value) and color purity is achieved in a time- and cost-efficient manner.

Claims

1. A method for producing recycled plastic materials, comprising the following steps: a) Producing or providing a starting composition comprising, based on the mass of the starting composition, 90% or more by mass of a target plastic, wherein the target plastic is selected from polyethylene, polypropylene, and polystyrene. b) Crush the starting composition in a crushing unit to obtain granular plastic material. c) Clean the granular plastic material to obtain a purified plastic material. The cleaning process includes washing in a high-powered washer at a temperature of 60°C or higher. The cleaning process following the high-intensity scrubber includes rinsing with permeate water, which is produced by purification in a reverse osmosis unit. d) The purified plastic material is extruded and granulated to obtain a recycled plastic material containing the target plastic.

2. The method according to claim 1, wherein the target plastic is selected from polyethylene.

3. The method according to any one of claims 1 or 2, wherein the starting composition consists of 95% or more of recycled plastic material by mass, based on the mass of the starting composition.

4. The method according to any one of claims 1 to 3, wherein the granular plastic material comprises the target plastic in the form of fragments.

5. The method according to any one of claims 1 to 4, wherein the washing in the powerful washer is performed at a temperature of 65°C or higher.

6. The method according to any one of claims 1 to 5, wherein the particulate plastic material forms a packing density gradient along the direction of gravity in the high-intensity washer.

7. The method according to any one of claims 1 to 6, wherein the cleaning prior to the powerful washer comprises cleaning in a friction washer.

8. The method according to any one of claims 1 to 7, wherein the permeate water is produced immediately before and / or during method step c).

9. The method according to any one of claims 1 to 8, wherein the granulation of the purified plastic material is carried out by underwater granulation, preferably by permeation underwater.

10. A purification apparatus for use in the method according to any one of claims 1 to 9, comprising: i) A pulverizing unit for pulverizing the starting composition, ii) A powerful detergent for cleaning the particulate plastic material at temperatures of 60°C or above. iii) Reverse osmosis equipment used to produce permeate water, and iv) An extruder for extruding and granulating the purified plastic material.

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