RECYCLING METHOD

Abstract

A method for recycling packaging wastes, referred to as first articles, made of PET or polyolefins (PO), that can be decolored in accordance with the key-locker principle, and second articles made of PET or PO, comprising the steps: (a) pre-sorting the first and second articles, (b) pre-washing the articles, (c) comminuting the articles to form flakes, (d) washing the articles, (e) dewatering and drying the flakes, (f) flake sorting, (g) extrusion, (h) solid-state polycondensation (SSP) in the case of PET wastes, or (i) decontamination in the case of PO wastes. The first articles are separated from the second articles by optical sorting and are decolored separate from the second articles in a decoloring step (j) by a reagent referred to as a key. The first decolored articles are temporarily stored (m) after step (j). After being stored, the first articles are fed to separate steps (g) and (h) or (i).

Claims

1. A method for recycling packaging wastes made of polyethylene terephthalate (PET) or polyolefins (PO), the packaging wastes forming first articles and second articles made of PET or PO, comprising the steps: (a) pre-sorting the first and second articles, (b) pre-washing the first and second articles, (c) comminuting the first and second articles to form flakes thereof, (d) washing the flakes of the first and second articles in a first washing step, (e) dewatering and drying the flakes of the first and second articles in a first drying step, (f) sorting the flakes of the first and second articles to separate the flakes of the first articles form the flakes of the second articles in order to concentrate the flakes of the first articles, (g) extruding the flakes of the first and second articles, and (h) performing solid-state polycondensation (SSP) in the case of PET flakes, or (i) decontaminating in the case of PO flakes, (j) performing an improving step by decoloring the flakes of the first articles or depleting contaminants from the flakes of the first articles, (m) temporarily storing the flakes of the first articles in a store after performing step (j), and (n) feeding the flakes of the first articles after step (m) to step (g) and then to steps (h) for PET flakes or step (i) for PO flakes.

2. The method according to claim 1, further comprising decoloring the first articles in step (j) in accordance with a key-locker principle wherein the first articles are decolored by a reagent referred to as a key.

3. The method according to claim 1, wherein the first articles are separated from the second articles in step (a).

4. The method according to claim 1, wherein the first articles are separated as flakes from the second articles in step (f).

5. The method according to claim 1, wherein the sorting of the first articles is optical sorting and can be affected by color, shape, digital watermarks or marking substances.

6. The method according to claim 1, wherein the store (m) is filled exclusively with first articles in the form of flakes.

7. The method according to claim 1, wherein the store (m) is filled with first articles in the form of flakes and with natural-colored PO flakes and, respectively, transparent PET flakes from an external recycling method (n).

8. The method according to claim 1, wherein the improving step (j) is part of a bypass of the sorted first articles, which bypass is guided in a main stream of the first articles to the main stream of the second articles.

9. The method according to claim 1, wherein the improving step (i) comprises the decoloring that is performed in a decoloring bath.

10. The method according to claim 9, wherein the decoloring step is operated either in a batchwise or continuous manner.

11. The method according to claim 1, wherein the first articles are ground into flakes before being fed to the improving step (j).

12. The method according to claim 8, further comprising a second washing step (k) in the bypass before or after the improving step (j).

13. The method according to claim 10, wherein the second washing step is a second intensive washing step.

14. The method according to claim 11, wherein the second intensive washing step is performed at a temperature between 50? C. and 90? C. and with a wash liquor with 0.5 to 5% NaOH.

15. The method according to claim 8, further comprising a second drying step in the bypass to dewater decolored flakes of the first articles.

16. The method according to claim 8, further comprising a second drying step is provided in the bypass, in which the decolored flakes of the first articles are dried.

17. The method according to claim 1, wherein the first washing step is an intensive washing step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further advantages and features become apparent from the following description of a plurality of exemplary embodiments of the invention with reference to the schematic representations. In the drawings, which are not true to scale:

[0029] FIG. 1: shows a flow diagram of a method for recycling PET or PO bottles as known from the prior art;

[0030] FIG. 2: shows a flow diagram showing a first embodiment for decoloring first articles integrated into the method according to FIG. 1, wherein the masterbatch is hot liquor-resistant and the first articles have a low market penetration (the low market penetration also applies to the embodiments of FIGS. 3 to 5);

[0031] FIG. 3: shows a flow diagram showing a second embodiment for decoloring first articles integrated into the method according to FIG. 1, wherein the masterbatch is also hot liquor-resistant;

[0032] FIG. 4: shows a flow diagram showing a third embodiment for decoloring first articles integrated into the method according to FIG. 1, wherein the masterbatch is not hot liquor-resistant,

[0033] FIG. 5: shows a flow diagram showing a fourth embodiment for decoloring first articles integrated into the method according to FIG. 1, wherein the masterbatch is also not hot liquor-resistant,

[0034] FIG. 6: shows a flow diagram showing a fifth embodiment for hot liquor-resistant masterbatches, wherein the first articles have a relevant market penetration (the relevant market penetration also applies to the embodiments of FIGS. 6 to 9);

[0035] FIG. 7: shows a flow diagram showing a sixth embodiment for hot liquor-resistant masterbatches;

[0036] FIG. 8: shows a flow diagram showing a seventh embodiment for hot liquor-resistant masterbatches, and

[0037] FIG. 9: shows a flow diagram showing an eighth embodiment for masterbatches that are also not hot liquor-resistant.

DETAILED DESCRIPTION OF THE INVENTION

[0038] FIG. 1 illustrates a flow diagram of a known method for recycling PET or PO packaging wastes. The method comprises the following steps: [0039] (a) pre-sorting the collected articles, [0040] (b) pre-washing the articles, [0041] (c) comminuting the articles to form flakes, [0042] (d) washing the articles in a first washing step, [0043] (e) dewatering and drying the flakes in a first drying step, [0044] (f) flake sorting, [0045] (g) extrusion and [0046] (h) solid-state polycondensation (SSP) in the case of PET wastes, or [0047] (i) decontamination in the case of PO wastes,

[0048] The pre-sorting (a) is an optical sorting operation by which articles are advantageously sorted by color from the mixed-color plastic waste products of one type of plastic (PO or PET), and other foreign materials are separated so that the target fraction is concentrated.

[0049] Steps (b) and (c) can be carried out in the following embodiment options: [0050] 1.) Single-stage comminution with pre-wash and/or post-wash or [0051] 2.) Two-stage comminution with pre-wash and/or intermediate wash and/or post-wash or [0052] 3.) Comminution by means of a wet or dry mill.

[0053] The first washing step (d) can be an intensive washing step. The intensification can be performed, for example, by means of a multi-hour intensive hot wash with liquor and detergents. After the SSP (h), the pellets made of rPET produced by extrusion (g) can, for example, be processed again to form containers, in particular bottles. The recycled pellets made of rHDPE can, for example, also be processed again to form containers, such as bottles.

[0054] The method according to the present invention is based on a partial stream of first articles of a recycled product requiring or enabling a special treatment step, also referred to as an improving step, which significantly enhances the added value or the quality of the overall product. The main stream accordingly consists of second articles which constitute the main volume stream of the product to be recycled. The partial stream of first articles has a feature that can be used in (optical) sorting to separate this partial stream. The relevant treatment step can be a decoloring concept or, more generally, the specific separation of contaminants that can only be found on a partial stream that can be uniquely assigned by sorting techniques. The contaminants can be, for example, special coatings on PET flakes.

[0055] An embodiment based on smart coloring technology is shown in FIGS. 2 to 5. In the method according to FIGS. 2 to 5, first and at least second articles made of PET or polyolefins (PO) are mixed in the packaging wastes which are fed as bales to step (a). The bales contain between 90 and 98 wt. % of packaging wastes of one type of plastic, i.e., PET or PO. The first articles can be decolored according to the key-locker principle, which principle is disclosed in EP 3 516 108 A1 and EP 3 770 208 A1. In this case, a color masterbatch is used whose color can be absorbed by a polar decoloring agent (reagent or key). This allows the first articles to be decolored by dissolving the coloring substances out of the first articles. This essentially improves the sustainability of plastic bottles and products.

[0056] With this principle, there is firstly a risk that the first articles will bleed in a common fraction with second articles, i.e., release their color early or at points in the recycling process where this has a disruptive effect. It is also disruptive if impurities also enter the decoloring bath.

[0057] Secondly, when a new technology is introduced, such as the key-locker principle, the quantities in the return stream of collected recyclables are still too small to be able to recycle them in a correctly sorted and at the same time economical manner.

[0058] The flow diagrams according to FIGS. 2 to 5 relate to methods when the first articles have a low market penetration. That is, the feed stream of packaging wastes has a low proportion of first articles. Typical quantities of first articles are below 10 wt. %.

[0059] The flow diagrams according to FIGS. 6 to 9 show methods for a relevant market penetration of first articles. That is, the feed stream of packaging wastes has a relevant proportion of first articles. Typically, more than 10 wt. % of first articles are present in the recycling stream.

[0060] The flow charts according to FIGS. 2 and 3 are based on the idea of splitting the recycling stream in the processing phase, and thereby separating the first articles into a bypass or main stream of the first articles during the flake sorting (f) and collecting them separately in a storage silo (m) after the decoloring (j). This allows the recycling method to be operated economically even with low market penetration. Since the first articles present as flakes are separated from the main stream of the second articles only after the first washing step (d), the masterbatch must be hot liquor-resistant. Bleeding in the intensive washing step (d) is therefore not possible.

[0061] Optical sensors are used to concentrate the first articles in the bypass or the main stream of the first articles. It is conceivable to sort only by color, because the decolorable masterbatch is only used for one color; it is also possible to use characteristic shape features or brand logos that can be identified by image data processing. Finally, digital watermarks and marking substances can also be used. It is understood that identifying features, as described in the previous two sentences, can only be recognized in the case of uncomminuted first articles. Shape features, brand logos or digital watermarks can be used as sorting features only in methods according to flow charts of FIGS. 4 and 8.

[0062] In the bypass, a decoloring step (j) is provided in which the first articles present as flakes are decolored by the key. Advantageously, step (j) is carried out in a decoloring bath. The decolored flakes are fed to a post-wash (k1) as shown in FIG. 2. This post-wash can be carried out with cold water and without chemicals if the decolored flakes no longer require intensive cleaning.

[0063] According to FIG. 3, the post-wash can also be a second intensive washing step (k2) with caustic soda and cleaning substances. Since the flakes have already been decolored, they can no longer bleed in the intensive washing step (k2). After a second drying step (l), the decolored flakes are stored in the storage silo (m).

[0064] In case of low market penetration with first articles, it would be economically unviable to run the first articles through a separate extrusion (g) with subsequent steps (h) or (i). Therefore, the silo (m) is additionally filled with natural-colored PO flakes or transparent PET flakes from an external recycling method (n). The transparent flakes are processed according to the method shown in FIG. 1 up to the flake sorting (f). The separate extrusion (g) of the side stream can thus be operated economically with a sufficient quantity of flakes.

[0065] Also, the decolored and cleaned flakes of the first articles can be admixed to an already existing recycling method, which produces natural-colored or transparent flakes, in a storage silo (m) before the flake mixture is extruded.

[0066] FIGS. 4 and 5 show two embodiments for a low market penetration of first articles, in which the masterbatch is not hot liquor-resistant and would accordingly bleed during intensive hot washing with chemicals. In this case, the separation of the first articles from the main stream of the second articles is brought forward and the first washing step (d) takes place only after the storage silo (m) together with the natural-colored or transparent articles from a separate recycling method.

[0067] According to the method shown in FIG. 4, the first articles are already sorted as bottles out of the main stream of the second articles and the further method steps (b) and (c) are already carried out in the side stream. After the decoloring (j) and a first drying step (e), the decolored flakes are collected in the storage silo (m) and mixed with the additional natural-colored flakes so that a profitable quantity of flakes is present. Only after the storage silo (m) is the first washing step or intensive washing step (d) carried out, which is not critical because the first articles are already decolored. After a second drying step (l) and the flake sorting (f), the flakes can be extruded.

[0068] FIG. 5 also visualizes an embodiment of the recycling method for a low market penetration of first articles and a masterbatch that is not hot liquor-resistant. First, the usual method steps (a), (b) and (c) are performed. After a pre-washing step (d2), which is carried out gently to prevent discoloration of the masterbatch, the first articles are separated in the flake sorting (f). After a first drying step, the first articles present as decolored flakes are temporarily stored in the storage silo (m). As already stated above, the quantity of flakes is increased with the additional natural-colored flakes (n) so that a profitable quantity of flakes is present.

[0069] Only after this increase in quantity are the flakes intensively washed in the washing step or intensive washing step (d). In this step (d), the masterbatch can no longer bleed, since the first articles have already been decolored beforehand. After a second drying step (l), the flakes of the side stream are extruded separately from the main stream of the second articles. This separate extrusion (g) with the subsequent steps (h) or (i) is economically viable, since a sufficient quantity of flakes is present in the storage silo (m).

[0070] In principle, the embodiments according to FIGS. 6 to 9 are equivalent to those of FIGS. 2 to 5 in terms of the method sequence. However, these options are only applied when the recycling market has a sufficiently relevant market penetration of first articles. In that case, it is no longer necessary to supplement the first articles present as flakes in the storage silo (m) with a separate stream (n) of transparent flakes (PO) or natural-colored flakes (PET).

[0071] The invention allows several pre-sorting steps to be combined with a pre-washing step (b), (k), which enables concentration and precleaning of the portions to be provided for the decoloring bath (j). For this purpose, after the pre-sorting, the first articles are guided in a bypass or in a main stream of the first articles, which first articles are collected and temporarily stored in a storage silo (m) after being decolored.

[0072] Depending on market penetration, transparent PET flakes or natural-colored PO flakes can additionally be added to the storage silo (m) if required. These added flakes can already be intensively washed and dried when the first articles also enter the storage silo in a cleaned state. This ensures that there is a sufficient quantity of flake to make separate extrusion (g) for the first articles profitable. In principle, the approach is suitable for PO plastic products and for PET plastic products.