Method for mechanically recovering polypropylene

Abstract

The invention relates to a method for mechanically recycling polypropylene, a method for obtaining high-purity reworked material grade, a mixed plastic polypropylene blend corresponding to the high-purity reworked material grade, a product containing the high-purity reworked material grade and application of the high-purity reworked material grade to preparation of polypropylene labels.

Description

Technical Field

[0001] This invention relates to a method for obtaining mechanically recycled polypropylene of a high purity recycled grade, a mixed plastic polypropylene blend corresponding to the high purity recycled grade, articles containing the high purity recycled grade, and the use of the high purity recycled grade in the preparation of polypropylene labels. Background Technology

[0002] Over the past decade, there has been a growing focus on the environmental sustainability of plastics and their current usage. This has led to new legislation concerning the disposal, collection, and recycling of polyolefins. Furthermore, some countries are striving to increase the percentage of plastic materials recycled, rather than sending them to landfills.

[0003] In Europe, approximately 27 million tons of plastic waste are generated annually; in 2016, 7.4 million tons were landfilled, 11.27 million tons were incinerated (for energy production), and about 8.5 million tons were recycled. Polypropylene-based materials present a particular problem due to their widespread use in packaging. Given the enormous amount of waste collected compared to the amount recycled (only about 30%), there is still significant potential for intelligent reuse of plastic waste streams and mechanical recycling of plastic waste.

[0004] Take the automotive industry as an example. In Europe, the EU's End-of-Life (ELV) Directive stipulates that 85% / 95% of automotive materials should be recyclable or reusable. Currently, the recycling rate of automotive parts is far below this target. On average, a car consists of 9 wt.% plastic, and of that, only 3 wt.% is currently recycled. Therefore, there is still a significant unmet need to achieve the automotive industry's plastic recycling goals. This invention specifically focuses on the mechanical recovery of waste streams, rather than "energy recovery" through the combustion of polyolefins for energy. However, due to cost, poor mechanical properties, and low processability, waste streams containing cross-linked polyolefins are often used for energy recovery (such as incineration in district heating plants or for heating in the cement industry) and are rarely recycled into new products.

[0005] A major trend in the polyolefin sector is the use of recycled materials from a variety of sources. Durable goods streams such as waste electrical equipment (WEE) or end-of-life vehicles (ELV) contain a variety of plastics. These materials can be processed to recycle acrylonitrile-butadiene-styrene (ABS), high-impact polystyrene (HIPS), polypropylene (PP), and polyethylene (PE) plastics. Separation can be achieved by first performing density separation in water, followed by further separation based on fluorescence, near-infrared absorption, or Raman fluorescence. However, it is often difficult to obtain pure recycled polypropylene or pure recycled polyethylene. Generally, recycled polypropylene on the market is a mixture of polypropylene (PP) and polyethylene (PE); this is especially true for post-consumer waste streams. Commercially recycled materials derived from post-consumer waste typically contain a mixture of PP and PE, with minor components comprising <50 wt%.

[0006] The higher the quality (i.e., the higher the purity) of recycled polyolefins, the more expensive the material. In addition, recycled polyolefin materials are often cross-contaminated with non-polyolefin materials (such as polyethylene terephthalate, polyamide, polystyrene) or non-polymer substances (or wood, paper, glass, or aluminum, etc.).

[0007] Furthermore, materials rich in recycled polypropylene generally perform much worse than virgin materials unless the amount of recycled polyolefin added to the final compound is extremely small. For example, these materials typically exhibit poorer odor and taste, limited stiffness, limited impact strength, and poorer mechanical properties (e.g., brittleness), thus failing to meet customer requirements.

[0008] For certain applications, polymer grades require high purity and stringent requirements, which are often difficult to achieve when using recycled materials for the reasons mentioned above. Polypropylene labels are one such application. In addition to the requirements of balanced mechanical properties and high purity, polypropylene labels typically need to be white or transparent. Therefore, developing recycling methods that can obtain high-purity recycled materials with an ideal balance of properties (including color) is crucial for expanding the application of recycled materials in a wider range of fields. Summary of the Invention

[0009] This invention is based on the observation that high purity can be achieved through mechanical recycling methods involving providing a precursor polypropylene recycled stream composed of polypropylene labels and performing a specific combination of cleaning steps. The correct combination of the provided starting material and the cleaning process contributes to the unexpectedly superior properties of the final recycled polypropylene.

[0010] Therefore, in a first aspect, the present invention relates to a method for mechanically recycling polypropylene, comprising the following steps in a given sequence:

[0011] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0012] b) Optionally, the precursor polypropylene recovery stream (A) may be sorted according to the polymer type to remove any fragments containing polymers other than polypropylene, thereby generating a purified polypropylene recovery stream (B).

[0013] c) The purified polypropylene recovery stream (B) is cleaned in one or more cleaning steps, or if step b) is not present, the precursor polypropylene recovery stream (A) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0014] d) Optionally, the washed polypropylene stream (C) is separated into heavy fraction and light fraction polypropylene recovery stream (D).

[0015] e) Melt-extrude the light-grade polypropylene recycled stream (D), preferably granulating it, or if step d) is absent, melt-extrude the washed polypropylene stream (C), preferably granulating it, preferably adding an additive (Ad) in the molten state, thereby forming an extruded, preferably granulated, recycled polypropylene composition (E); and

[0016] f) Optionally, the recycled polypropylene composition (E) is ventilated to remove volatile organic compounds, thereby generating an ventilated recycled polypropylene product (F1).

[0017] In this case, the order of steps f) and e) can be interchanged, such that the light fraction polypropylene recycled stream (D) is first aerated, or if step d) is absent, the cleaned polypropylene stream (C) is aerated to form aerated recycled polypropylene sheets (F2), which are then extruded, preferably with additives (Ad) added in the molten state, to form an extruded, preferably granulated, aerated recycled polypropylene product (F3).

[0018] In a second aspect, the present invention relates to a blended plastic polypropylene (PP) having a melt flow rate (MFR2) of 3.5 to 8.0 g / 10 min, as determined according to ISO 1133 at 230°C and 2.16 kg.

[0019] The polymer portion of the mixed plastic polypropylene blend (PP) has:

[0020] i) The ethylene content (C2 (total)) determined by CRYSTEX QC analysis is 0.0 to 5.0 wt%;

[0021] ii) The crystalline fraction (CF) content, as determined by CRYSTEX QC analysis, is 93.0 to 100.0 wt%;

[0022] iii) The soluble fraction (SF) content, as determined by CRYSTEX QC analysis, is 0.0 to 7.0 wt%; and

[0023] iv) The ethylene content (C2(CF)) of the crystalline fraction determined by CRYSTEX QC analysis is 0.0 to 5.0 wt%.

[0024] Particularly preferred is that the method of the first aspect prepares the mixed plastic polypropylene blend (PP) of the second aspect.

[0025] Preferably, the mixed plastic polypropylene blend (PP) of the second aspect is produced by the method of the first aspect.

[0026] In a third aspect, the present invention relates to articles comprising a blend of polypropylene (PP) plastics of the second aspect, wherein the articles are selected from labels and films.

[0027] In a final aspect, the present invention relates to the use of a blended plastic polypropylene (PP) blend for the production of polypropylene labels containing recycled materials.

[0028] definition

[0029] Post-consumer waste refers to items that have completed at least their first use cycle (or life cycle), meaning they have achieved their primary purpose; while industrial waste refers to production waste that typically does not reach consumers.

[0030] The recycling stream may contain either articles for recycling or fragments of articles for recycling, such as flakes. In this invention, the contents of the recycling stream are referred to as fragments, whether these fragments are whole articles, fragments of articles, or flakes. In some embodiments, the fragments may be flakes, while in other embodiments, the fragments may be larger objects that are transformed into flakes in a later stage.

[0031] In this invention, a mixed plastic recycling stream can be any stream suitable for recycling that contains polyolefins and not just a single polyolefin product. For example, for some post-industrial waste recycling streams, the production waste of a single polyolefin grade, or a single polyolefin-containing product, may be the only fragment present in the stream. Generally, post-consumer waste recycling streams containing polyolefins will be mixed plastic recycling streams, as are many post-industrial waste recycling streams containing polyolefins. According to the invention, a "polyolefin recycling stream" can be a mixed plastic recycling stream, or one that has undergone a pre-sorting process to enrich a specific type of polyolefin. Alternatively, or additionally, due to optimized waste collection management, a polyolefin recycling stream may also have a high purity of one type of polyolefin, where only a specific type of waste is collected in a given recycling stream.

[0032] In this invention, "product form" refers to the shape and form of the products in the polyolefin recycling stream. These products may exist in the form of films, bags, and pouches, which are considered flexible products; or they may exist in the form of molded products, such as food containers, skincare containers, and plastic bottles, which are considered rigid products. Commercial optical sorting machines, such as Tomra Autosort, RTT Steinert Unisort, and Redwave Pellenc, can separate rigid products from flexible products by aerodynamic characteristics (i.e., airflow is typically applied in the aforementioned stream, and the falling arc of rigid products differs from that of flexible products), thereby converting the stream containing such products into so-called rigid and flexible streams.

[0033] Furthermore, those skilled in the art will recognize that even state-of-the-art sorting methods, such as those involving the automated sorting machines described below, cannot achieve perfect sorting. This means that any wording such as "wherein the stream contains only one color" or "wherein the stream contains only one type of polyolefin" should be interpreted broadly, whereby the described stream essentially contains only the specified color or type of polyolefin, but cannot achieve 100% purity due to the technical limitations of the sorting steps.

[0034] Those skilled in the art will recognize that pH values ​​greater than 14.0 and less than 0.0 are theoretically possible; however, they will also recognize that determining such pH values ​​using conventional pH probes is very difficult. Therefore, in this invention, an aqueous solution with an effective pH value greater than 14.0 is considered to have a pH value of 14.0, while an aqueous solution with an effective pH value less than 0.0 is considered to have a pH value of 0.0.

[0035] In this invention, the term "rinse" refers to the addition of a solvent (usually water) to remove foreign matter or residual liquid from the surface of a polyolefin. This can be achieved in a very short time, i.e., less than 5 minutes, typically less than 1 minute. Compared to the "washing" step, which usually requires longer time and agitation, "rinse" can remove foreign matter adhering to the surface of the polyolefin and may extract volatile organic compounds from the polyolefin.

[0036] When the term "comprising" is used in this specification and claims, it does not exclude other undescribed elements that have a primary or secondary function. For the purposes of this invention, the term "consisting of..." is considered a preferred embodiment of the term "comprising...". If a group is defined below as comprising at least a certain number of elements, it can also be understood as disclosing a group that preferably consists only of those elements.

[0037] When referring to a singular noun, the use of an indefinite or definite article, such as "a," "a kind," or "the," includes the plural form of the noun, unless otherwise specified. Detailed Implementation

[0038] Methods for mechanically recycling polypropylene

[0039] In a first aspect, the present invention relates to a method for mechanically recycling polyolefins, comprising the following steps in a given sequence:

[0040] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0041] b) Optionally, the precursor polypropylene recovery stream (A) may be sorted according to the polymer type to remove any fragments containing polymers other than polypropylene, thereby generating a purified polypropylene recovery stream (B).

[0042] c) The purified polypropylene recovery stream (B) is cleaned in one or more cleaning steps, or if step b) is not present, the precursor polypropylene recovery stream (A) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0043] d) Optionally, the washed polypropylene stream (C) is separated into heavy fraction and light fraction polypropylene recovery stream (D).

[0044] e) The light-grade polypropylene recycled stream (D) is melt-extruded, preferably granulated, or if step d) is absent, the washed polypropylene stream (C) is melt-extruded, preferably granulated, with additive (Ad) added in the molten state, thereby forming an extruded, preferably granulated, recycled polypropylene composition (E); and

[0045] f) Optionally, the recycled polypropylene composition (E) is ventilated to remove volatile organic compounds, thereby generating the ventilated recycled polypropylene product (F1).

[0046] In this case, the order of steps f) and e) can be interchanged, such that the light fraction polypropylene recycled stream (D) is ventilated first, or if step d) is not present, the cleaned polypropylene stream (C) is ventilated to form ventilated recycled polypropylene sheets (F2), and then the ventilated recycled polypropylene sheets (F2) are extruded, preferably with additives (Ad) added in the molten state, to form an extruded, preferably granulated, ventilated recycled polypropylene product (F3).

[0047] In one implementation, the method includes the following steps in a given order:

[0048] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0049] c) Cleaning the precursor polypropylene recovery stream (A) in one or more cleaning steps to obtain a cleaned polypropylene stream (C); and

[0050] e) The cleaned polypropylene stream (C) is melt-extruded, preferably granulated, and preferably additives (Ad) are added in the molten state to form an extruded, preferably granulated, recycled polypropylene composition (E).

[0051] In another embodiment, the method includes the following steps in a given order:

[0052] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0053] b) The precursor polypropylene recovery stream (A) is sorted according to polymer type to remove any fragments containing polymers other than polypropylene, thereby generating a purified polypropylene recovery stream (B).

[0054] c) The purified polypropylene recovery stream (B) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C); and

[0055] e) The cleaned polypropylene stream (C) is melt-extruded, preferably granulated, and preferably additives (Ad) are added in the molten state to form an extruded, preferably granulated, recycled polypropylene composition (E).

[0056] In yet another embodiment, the method includes the following steps in a given order:

[0057] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0058] c) The precursor polypropylene recovery stream (A) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0059] d) Separating the cleaned polypropylene stream (C) into heavy fraction and light fraction polypropylene recovery stream (D); and

[0060] e) The light-grade polypropylene recycled stream (D) is melt-extruded, preferably granulated, and preferably additives (Ad) are added in the molten state to form an extruded, preferably granulated, recycled polypropylene composition (E).

[0061] In yet another embodiment, the method includes the following steps in a given order:

[0062] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0063] c) The precursor polypropylene recovery stream (A) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0064] e) Melt-extrude the cleaned polypropylene stream (C), preferably granulating it, and preferably adding an additive (Ad) in the molten state, thereby forming an extruded, preferably granulated, recycled polypropylene composition (E); and

[0065] f) Aeration of the recycled polypropylene composition (E) is used to remove volatile organic compounds, thereby generating the aerated recycled polypropylene product (F1).

[0066] In another embodiment, the method includes the following steps in a given order:

[0067] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0068] c) The precursor polypropylene recovery stream (A) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0069] f) Aeration of the cleaned polypropylene stream (C) removes volatile organic compounds, thereby generating aerated recycled polypropylene sheets (F2); and

[0070] e) The aerated recycled polypropylene sheet (F2) is melt-extruded, preferably granulated, and preferably additives (Ad) are added in the molten state to form an extruded, preferably granulated, aerated recycled polypropylene product (F3).

[0071] In another embodiment, the method includes the following steps in a given order:

[0072] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0073] b) The precursor polypropylene recovery stream (A) is sorted according to polymer type to remove any fragments containing polymers other than polypropylene, thereby generating a purified polypropylene recovery stream (B).

[0074] c) The purified polypropylene recovery stream (B) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0075] d) Separating the cleaned polypropylene stream (C) into heavy fraction and light fraction polypropylene recovery stream (D); and

[0076] e) The light-grade polypropylene recycled stream (D) is melt-extruded, preferably granulated, and preferably additives (Ad) are added in the molten state to form an extruded, preferably granulated, recycled polypropylene composition (E).

[0077] In another embodiment, the method includes the following steps in a given order:

[0078] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0079] b) The precursor polypropylene recovery stream (A) is sorted according to polymer type to remove any fragments containing polymers other than polypropylene, thereby generating a purified polypropylene recovery stream (B).

[0080] c) The purified polypropylene recovery stream (B) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0081] e) Melt-extrude the cleaned polypropylene stream (C), preferably granulating it, and preferably adding an additive (Ad) in the molten state, thereby forming an extruded, preferably granulated, recycled polypropylene composition (E); and

[0082] f) Aeration of the recycled polypropylene composition (E) is used to remove volatile organic compounds, thereby generating the aerated recycled polypropylene product (F1).

[0083] In another embodiment, the method includes the following steps in a given order:

[0084] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0085] b) The precursor polypropylene recovery stream (A) is sorted according to polymer type to remove any fragments containing polymers other than polypropylene, thereby generating a purified polypropylene recovery stream (B).

[0086] c) The purified polypropylene recovery stream (B) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0087] f) Aeration of the cleaned polypropylene stream (C) removes volatile organic compounds, thereby generating aerated recycled polypropylene sheets (F2); and

[0088] e) The aerated recycled polypropylene sheet (F2) is melt-extruded, preferably granulated, and preferably additives (Ad) are added in the molten state to form an extruded, preferably granulated, aerated recycled polypropylene product (F3).

[0089] In another embodiment, the method includes the following steps in a given order:

[0090] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0091] c) The precursor polypropylene recovery stream (A) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0092] d) Separate the cleaned polypropylene stream (C) into heavy fraction and light fraction polypropylene recovery stream (D);

[0093] e) Melt-extrude the light-grade polypropylene recycled stream (D), preferably granulating it, and preferably adding an additive (Ad) in the molten state, thereby forming an extruded, preferably granulated, recycled polypropylene composition (E); and

[0094] f) Aeration of the recycled polypropylene composition (E) is used to remove volatile organic compounds, thereby generating the aerated recycled polypropylene product (F1).

[0095] In another embodiment, the method includes the following steps in a given order:

[0096] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0097] c) The precursor polypropylene recovery stream (A) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0098] d) Separate the cleaned polypropylene stream (C) into heavy fraction and light fraction polypropylene recovery stream (D);

[0099] f) Aeration of the light-grade polypropylene recovery stream (D) to remove volatile organic compounds, thereby generating aerated recycled polypropylene sheets (F2); and

[0100] e) The aerated recycled polypropylene sheet (F2) is melt-extruded, preferably granulated, and preferably additive (Ad) is added in the molten state to form an extruded, preferably granulated, aerated recycled polypropylene product (F3).

[0101] In another embodiment, the method includes the following steps in a given order:

[0102] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0103] b) The precursor polypropylene recovery stream (A) is sorted according to polymer type to remove any fragments containing polymers other than polypropylene, thereby generating a purified polypropylene recovery stream (B).

[0104] c) The purified polypropylene recovery stream (B) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0105] d) Separate the cleaned polypropylene stream (C) into heavy fraction and light fraction polypropylene recovery stream (D);

[0106] e) Melt extrusion of the light-grade polypropylene recycled stream (D), preferably granulation, and preferably the addition of an additive (Ad) in the molten state, to form an extruded, preferably granulated, recycled polypropylene composition (E); and

[0107] f) Aeration of the recycled polypropylene composition (E) is used to remove volatile organic compounds, thereby generating the aerated recycled polypropylene product (F1).

[0108] In the final implementation, the method includes the following steps in a given order:

[0109] a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A);

[0110] b) The precursor polypropylene recovery stream (A) is sorted according to polymer type to remove any fragments containing polymers other than polypropylene, thereby generating a purified polypropylene recovery stream (B).

[0111] c) The purified polypropylene recovery stream (B) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0112] d) Separate the cleaned polypropylene stream (C) into heavy fraction and light fraction polypropylene recovery stream (D);

[0113] f) Aeration of the light-grade polypropylene recovery stream (D) to remove volatile organic compounds, thereby generating aerated recycled polypropylene sheets (F2); and

[0114] e) The aerated recycled polypropylene sheet (F2) is melt-extruded, preferably granulated, and preferably additive (Ad) is added in the molten state to form an extruded, preferably granulated, aerated recycled polypropylene product (F3).

[0115] Without being bound by theory, it is considered advantageous to perform step f) before step e), because an increased surface area to volume ratio of the polypropylene sheet means that more volatile organic compounds (VOCs) can be removed. Performing step e) before step f) is also advantageous because extrusion can generate new VOCs through the decomposition of polyolefins or contaminants (e.g., PVC or PET), or it can cause VOCs that were not originally near the sheet surface to migrate to the surface of the extruded product, thereby enhancing odor. Which implementation method is more preferred will vary depending on the process and should be optimized accordingly.

[0116] Step a) involves providing a precursor polypropylene recycled stream (A).

[0117] Based on the total weight of the precursor polypropylene recycled stream (A), the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing labels, more preferably at least 90 wt% polypropylene-containing labels, more preferably at least 95 wt% polypropylene-containing labels, and most preferably, the precursor polypropylene recycled stream (A) consists primarily of polypropylene-containing labels.

[0118] Using a labeled precursor polypropylene recycled stream (A) is one of the key steps of this invention. Commercially available polypropylene labels are typically made from polypropylene grades, such as propylene homopolymers, which are the main component of multilayer labels (typically comprising about 80-90 wt% of conventional multilayer labels). Therefore, when recycled using appropriate recycling methods, the resulting recycled material is highly homogeneous in terms of polymer properties (e.g., molecular weight, typically a low MFR2 value of 1 to 5 g / 10 min) and comonomer content (which is minimal due to the dominance of propylene homopolymers).

[0119] Preferably, the polypropylene-containing labels in the precursor polypropylene recycled stream (A) and the precursor polypropylene recycled stream (A) originate from post-consumer waste.

[0120] The precursor polypropylene recycled stream (A) can be obtained in a variety of ways.

[0121] In a broad sense, providing the precursor polypropylene recycled stream (A) is not difficult as long as it contains at least 85 wt% polypropylene-containing labels. Therefore, while some embodiments of the method according to the first aspect involve one or more steps of obtaining polypropylene-containing labels by sorting from other polymer articles, other embodiments of the invention may simply involve purchasing the precursor polypropylene recycled stream (A), for example, from a PET recycling organization. These embodiments, where sorting steps have previously occurred (typically at different locations and by different people), still fall within the scope of the invention because the key requirement of step a) is to provide the precursor polypropylene recycled stream (A) containing at least 85 wt% polypropylene-containing labels, regardless of how the precursor polypropylene recycled stream (A) is obtained.

[0122] In some implementations, providing a precursor polypropylene recycled stream (A) involves sorting out polypropylene-containing labels from other polymer articles.

[0123] Polypropylene labels typically appear as labels on bottles (such as PET bottles) and also exist on other containers in the form of so-called "pressure-sensitive labels." Polypropylene labels on bottles usually adhere only slightly to the bottle and are typically only adhered to one or more points on the label. Pressure-sensitive labels, on the other hand, are usually attached to rigid polyolefin-containing articles by adhesive, thus requiring more force to remove compared to polypropylene labels on bottles.

[0124] In one embodiment, the step of providing a precursor polypropylene recycled stream (A) containing at least 85 wt% polypropylene-labeled material is achieved by separating the polypropylene label from the bottle (preferably a PET-containing bottle) and then collecting the polypropylene label to obtain the precursor polypropylene recycled stream (A).

[0125] In this embodiment, the acquisition of polypropylene-containing labels is achieved as a byproduct of the PET recycling process. The precursor polypropylene recycled stream (A) obtained in this manner typically has high purity because separating the polypropylene bottle label from the PET-containing bottle (given the significant differences between polypropylene and PET) and the polyethylene (typically HDPE) cap is relatively straightforward. The polypropylene-containing label is usually the only polypropylene-containing component, thus it can be easily collected without significant contamination.

[0126] Furthermore, by utilizing byproducts from the PET recycling process, the process helps reduce waste and improves the overall impact of PET recycling on the circular economy.

[0127] Alternatively, the step of providing a precursor polypropylene recycled stream (A) containing at least 85 wt% polypropylene-containing labels is achieved by separating the polypropylene-containing labels attached to a rigid article containing polyolefin by an adhesive, then sorting out the polypropylene-containing labels from the rigid article containing polyolefin and collecting the polypropylene-containing labels, thereby obtaining the precursor polypropylene recycled stream (A).

[0128] While polypropylene labels are not as easily separated from rigid polyolefin-containing articles as they are from PET bottles, given the much greater similarity between polyolefins and polypropylene in polyolefin-containing articles (at least compared to PET), separating polypropylene labels from rigid polyolefin-containing articles using a simple dry density separation technique can be relatively straightforward. This technique separates flexible fragments (e.g., films and labels) from rigid fragments based on their aerodynamic properties. Such separation techniques are well known in the art. Suitable techniques include pneumatic classification, air separators, and zigzag cascades or air separators.

[0129] Based on the total weight of the precursor polypropylene recycled stream (A), the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing labels; however, these polypropylene-containing labels need not be in whole article form (i.e., complete labels). Other fragments, such as shredded labels, may also constitute part of the total label content in the precursor polypropylene recycled stream.

[0130] In some embodiments, it is preferable to reduce the fragment size of the precursor polypropylene recovery stream (A) or the purified polypropylene recovery stream (B) directly before the washing step.

[0131] The additional size reduction step can be performed using any method known to those skilled in the art. One suitable method involves milling the precursor polypropylene recovery stream (A) or the purified polypropylene recovery stream (B). Another method involves pulverizing the precursor polypropylene recovery stream (A) or the purified polypropylene recovery stream (B). Particularly preferred is that the additional size reduction step is a pulverizing step.

[0132] The additional pulverization step can be a wet pulverization process or a dry pulverization process. If this step is performed on the precursor polypropylene recovery stream (A) before step b), then the additional pulverization step is preferably a dry pulverization process. Alternatively, if this step is performed directly on the precursor polypropylene recovery stream (A) or the purified polypropylene recovery stream (B) before step c), then the additional pulverization step is preferably a wet pulverization process, wherein the precursor polypropylene recovery stream (A) or the purified polypropylene recovery stream (B) is first contacted with an aqueous solution, and then the resulting suspension is pulverized.

[0133] There are no particular restrictions on the choice of aqueous solution; however, it is preferred that the pH value of the aqueous solution is 8.0 to 14.0, more preferably 10.0 to 14.0, and most preferably 12.0 to 14.0.

[0134] Particularly preferably, the aqueous solution is the regenerated water washing solution previously used in step c).

[0135] Step b), if present, involves sorting the precursor polypropylene recovery stream (A) according to polymer type to remove any fragments containing polymers other than polypropylene, thereby generating a purified polypropylene recovery stream (B).

[0136] There are no particular limitations on the method used to sort the precursor polypropylene recovery stream (A) according to polymer type.

[0137] In one embodiment, the sorting in step b) can be performed using more than one optical sorter. In this invention, "optical sorter" refers to a sorting unit that uses any form of electromagnetic (EM) radiation (visible or non-visible light) to distinguish fragments of the precursor polypropylene recovery stream (A).

[0138] Suitable methods for sorting the recycled stream according to the polyolefin type include near-infrared spectroscopy, mid-infrared spectroscopy, high-speed laser spectroscopy, Raman spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. Near-infrared spectroscopy is particularly preferred.

[0139] The sorting in step b) can be achieved using a simple sorting algorithm, where optical sensors are programmed to evaluate which fragments should be selected or rejected based on a simple binary criterion. Alternatively, a more sophisticated AI-based system can be used for more precise sorting, where the optical sorter can identify certain articles, such as those bearing a specific brand, and determine the type of polymer contained in those articles based on this identification, without requiring manual determination of polymer content (e.g., via infrared spectroscopy analysis).

[0140] Alternatively, the sorting in step b) can also be achieved using, for example, the dry density separation technique described above, thereby removing rigid fragments (products or sheets) that do not contain polypropylene.

[0141] Although the precursor polypropylene recycled stream (A) is already of high purity, adding an extra sorting step at this stage helps ensure the highest possible purity, resulting in a purified polypropylene recycled stream (B) that is more enriched in the polypropylene-containing label. Furthermore, any polypropylene-containing labels containing significant amounts of polyolefins other than polypropylene can also be removed at this stage.

[0142] Step c) involves cleaning the purified polypropylene recovery stream (B) in one or more cleaning steps, or if step b) is not present, cleaning the precursor polypropylene recovery stream (A) in one or more cleaning steps to obtain a cleaned polypropylene stream (C).

[0143] While the nature of the cleaning steps is not limited in a broad sense, preferably, one or more cleaning steps in step c) continue until at least 85% of all ink is removed from the purified polypropylene recovery stream (B), or if step b) is not present, at least 85% of all ink is removed from the precursor polypropylene recovery stream (A).

[0144] Generally, the primary contaminant on polypropylene labels is ink. Label coloring is rarely achieved, as is typically the case with rigid (i.e., thicker) products, by adding more than one pigment to the polypropylene composition used to manufacture the label; instead, it is achieved by applying an ink layer to the label surface. With few exceptions, the polypropylene compositions used to produce polypropylene-containing labels are typically natural-colored (i.e., without pigment) or white. For white polypropylene compositions, the white appearance is usually a result of cavitation, which is generally associated with the presence of calcium carbonate. Cavitation is often used in conjunction with a white pigment (typically titanium dioxide).

[0145] While the presence of ink and / or ink-derived contaminants in the final recycled grade does not excessively affect polymer properties (e.g., rheological or mechanical properties), they do have a significant impact on the appearance of the recycled material, often resulting in a dark gray or black color. For some applications, dark gray or black is a suitable color, but this is often not the case. Removing at least 85% of all ink from the purified polypropylene recycled stream (B), or, if step b), from the precursor polypropylene recycled stream (A), can improve the appearance of the final recycled grade and reduce the content of ink-derived contaminants, such as various metal ions and other organic compounds that may cause odors (inks (or adhesives) are inherently odorless, but degradation of the ink (or adhesive) during compounding may produce volatile, odorous compounds), or otherwise adversely affect the final recycled grade (e.g., metal ion-catalyzed degradation pathways).

[0146] Preferably, one or more of the cleaning steps in step c) are continued until at least 90%, more preferably at least 95%, and most preferably substantially 100% of all ink is removed from the purified polypropylene recovery stream (B); or if step b) is not present, at least 90%, more preferably at least 95%, and most preferably substantially 100% of all ink is removed from the precursor polypropylene recovery stream (A).

[0147] Those skilled in the art will readily understand that the degree of ink removal can be monitored throughout the entire process of more than one cleaning step to ensure that sufficient ink has been removed. Alternatively or additionally, those skilled in the art can appropriately optimize the cleaning conditions to achieve this degree of ink removal, wherein key parameters (e.g., cleaning temperature, cleaning time, selection of cleaning solution, presence / absence of agitation) affect the ink removal effectiveness of cleaning steps known in the art.

[0148] For example, suitable conditions for removing ink during polyolefin recycling are disclosed in WO2021 / 018605A1 and WO2021 / 104797A1. In these documents, good results are obtained using acid washing (preferably concentrated H2SO4) or acid / oil emulsions (preferably H2SO4 / cyclohexane). The conditions in these documents are also applicable to removing other foreign matter, such as metal layers, adhesives, paper labels, etc.

[0149] However, preferably, at least one of the cleaning steps in step c) uses an alkaline water washing solution and is carried out at a temperature of 40 to 85°C. More preferably, all of the cleaning steps in step c) use an alkaline water washing solution and are carried out at a temperature of 40 to 85°C.

[0150] There are no particular restrictions on the choice of alkaline washing solution; however, preferably, the pH value of the alkaline washing solution is 8.0 to 14.0, more preferably 10.0 to 14.0, and most preferably 12.0 to 14.0.

[0151] Preferably, the alkaline washing solution is an aqueous solution selected from calcium hydroxide, potassium hydroxide, magnesium hydroxide, lithium hydroxide, sodium bicarbonate, sodium hydroxide, and mixtures thereof. Most preferably, the alkaline washing solution is an aqueous solution of sodium hydroxide.

[0152] Preferably, the alkali content in the alkaline washing solution is 0.05 to 10 wt% relative to the total weight of the alkaline washing solution, more preferably 0.10 to 7 wt%, and most preferably 0.50 to 5 wt%.

[0153] In a particularly preferred embodiment, the alkaline washing solution is a sodium hydroxide solution, and the concentration of sodium hydroxide is 0.50 to 5.0 wt% relative to the total weight of the alkaline washing solution.

[0154] The alkaline washing solution applicable to one or more cleaning steps in step c) may contain detergent in an amount of 0.1 wt% to 1.0 wt% relative to the total weight of the alkaline washing solution.

[0155] The detergent may be a commercially available detergent mixture or may be composed in any manner known to those skilled in the art. Suitable detergents include TUBIWASH SKP, TUBIWASH GFN, TUBIWASHEYE and TUBIWASH TOP, which are commercially available from CHT Company; KRONES colclean AD 1004, KRONES colclean AD 1002 and KRONES colclean AD 1008, which are commercially available from KIC KRONES Company; and P3-stabilon WT and P3-stabilon AL, which are commercially available from ECOLAB Ltd.

[0156] Preferably, the cleaning in step c) involves applying agitation in one or more cleaning steps, wherein the agitation is selected from mechanical mixing, ultrasonic treatment, mechanical grinding, or pump circulation, or combinations thereof. This agitation helps to bring the flakes in the recovery stream into contact with fresh cleaning fluid, thereby ensuring that the above method is not hindered by the accumulation of contaminants (e.g., ink) near the flakes.

[0157] Those skilled in the art will recognize that the various individual methods described above can be combined to improve mixing effects, such as a combination of mechanical mixing and ultrasonic treatment. Furthermore, defoamers can be added to help prevent foaming, thereby improving the mixing effect of the flakes and increasing cleaning efficiency.

[0158] The cleaning in step c) can be carried out for 5 minutes to 2 hours, more preferably 10 minutes to 1 hour, and most preferably 10 minutes to 30 minutes.

[0159] Particularly preferably, each individual cleaning step in step c) includes the following steps in a given order:

[0160] Ci) involves contacting the relevant polypropylene recovery stream with the cleaning fluid at a controlled temperature for a controlled time, thereby generating a suspended polypropylene recovery stream (C1); and

[0161] cii) Remove at least a portion of the cleaning fluid and any substances not floating on the surface of the cleaning fluid, thereby generating a cleaned polypropylene recovery stream (C2).

[0162] Preferably, the last separate cleaning step in step c) further includes the following steps:

[0163] ciii) Dry the cleaned polypropylene recovery stream (C2) to obtain a dried polypropylene recovery stream (C3).

[0164] The dried polypropylene recovery stream (C3), or if step ciii) is absent, the cleaned polypropylene recovery stream (C2) generated in the last separate cleaning step is used as the cleaned polypropylene stream (C) in subsequent steps.

[0165] By removing each cleaning fluid sequentially, ink and other contaminants (such as adhesives and / or paper labels) removed during the cleaning process can be removed from the recycling stream.

[0166] After one or more steps cii), the cleaned polypropylene recovery stream may optionally be rinsed with water to remove residual cleaning fluid remaining on the surface of the cleaned polypropylene recovery stream (C2) fragments. Preferably, at least the final separate cleaning step of step c) prior to step ciii) includes rinsing with water to remove residual cleaning fluid remaining on the surface of the cleaned polypropylene recovery stream (C2) fragments.

[0167] If any rinsing steps are involved, their duration should be less than 5 minutes.

[0168] Rinsing not only removes all residual cleaning fluid, but also removes any residual contaminants (such as ink) contained in the residual cleaning fluid.

[0169] Step d (if present) involves separating the cleaned polypropylene stream (C) into heavy fraction and light fraction polypropylene recovery stream (D).

[0170] Light fraction polypropylene recycled stream (D) typically contains labels and fragments derived from the labels, while heavy fraction contains rigid fragments.

[0171] The separation in step d) can be performed using any dry density separation technique known in the art. Suitable techniques include pneumatic classification, air sieves, and zigzag cascades or air separators.

[0172] Those skilled in the art will understand that the separation of light and heavy fractions using this method is influenced not only by the flake density but, more importantly, by the aerodynamic properties of the flakes (typically the surface area to weight ratio). Therefore, flat labels will separate from the larger polyolefin flakes. The terms "light fraction" and "heavy fraction" are commonly used in the art and do not strictly refer to classification solely by density. In this invention, these terms have the same meaning as commonly understood in the art.

[0173] In addition to the separation in step d), debris not originating from the label and / or film can be removed through sorting operations other than dry density separation techniques. Suitable methods include optical sorting machines that sort based on article morphology, such as camera systems (operating in the visible light range of the EM spectrum). This sorting step can be achieved using simple sorting algorithms, where optical sensors are programmed to evaluate which debris should be selected or rejected based on simple binary considerations. Alternatively, more sophisticated AI-based systems can be used to achieve more precise sorting, especially when sorting based on article morphology.

[0174] Alternatively, non-polypropylene materials can be removed by a flotation-sinking separation step based on density.

[0175] Between step d) and step e), there may be an additional step to remove fragments (i.e., fine particles) with a maximum size of less than 2 mm. This can be done using any method known to those skilled in the art, such as using a filter or sieve.

[0176] Step e) involves melt extruding the light-grade polypropylene recycled stream (D), preferably granulating, or, if step d) is absent, melt extruding the cleaned polypropylene stream (C), preferably granulating, with the addition of an additive (Ad) in the molten state, thereby forming an extruded, preferably granulated, recycled polypropylene composition (E).

[0177] Preferably, the extrusion of the recycled polypropylene composition (E) in step e) is carried out using an extruder, more preferably using a twin-screw extruder.

[0178] Conventional compounding or blending equipment is particularly preferred, such as a Banbury mixer, a twin-roll rubber mill, a Buss co-kneader, or a twin-screw extruder. More preferably, the mixing is completed in a co-rotating twin-screw extruder. Preferably, the extruded recycled polypropylene composition (E) recovered from the extruder is in granular form, i.e., granulated recycled polypropylene composition (E).

[0179] Preferably, the melt extrusion in step e) includes a melt filtration step, wherein gel and other fine particles are removed from the melt by filtration. This significantly improves the purity of the resulting recycled material, which is especially important when the recycled material is used to produce new labels with high purity / visual appearance requirements.

[0180] Any additives (Ad) added in step e) are selected from additives known in the art, preferably from antioxidants, stabilizers, fillers, colorants, nucleating agents, antistatic agents, and mixtures thereof.

[0181] Such additives are typically commercially available and are described, for example, on pages 871-873 of the 5th edition of Hans Zweifel's Plastic Additives Handbook, published in 2001.

[0182] Step f (if present) involves ventilating the recycled polypropylene composition (E) to remove volatile organic compounds, thereby generating the ventilated recycled polypropylene product (F1).

[0183] The ventilation in step f) can be achieved by using air, inert gas or steam.

[0184] Preferably, the ventilation in step f) is achieved by contacting the recycled polypropylene composition (E) with N2 gas at a volume ratio of at least 60%, or if steps e) and f) are interchanged, the cleaned polypropylene stream (C) is contacted with N2 gas at a volume ratio of at least 60%.

[0185] Preferably, the ventilation temperature according to step f) is 50 to 155°C, more preferably 100 to 150°C.

[0186] It is also beneficial to perform the ventilation in step f) at a reduced pressure, for example, below 500 mbar, more preferably below 200 mbar, and most preferably below 100 mbar.

[0187] The aeration performed according to step f) ensures that the content of volatile organic compounds (VOCs) in the aerated, extruded recycled polypropylene (F1) or aerated recycled polypropylene sheet (F2) is minimized, avoiding any off-odors that typically arise from recycled polyolefin blends. These VOCs are usually generated due to polyolefin contamination during first-consumer use, such as through contact with food, skin care products, or other bath products, or simply due to the breakdown of polyolefins into volatile oligomer chains during processing steps.

[0188] In addition to the steps described above, preferably, the method of the first aspect further includes a step of color sorting polypropylene fragments in the cleaned polypropylene stream (C), the light-grade polypropylene recovery stream (D), or the aerated recycled polypropylene sheet (F2) to remove all non-white or transparent polypropylene fragments.

[0189] Since labels are typically made of white or transparent polypropylene, any coloring is the result of surface inks, not any pigments contained in the polypropylene itself. Therefore, removing any polypropylene fragments that are neither white nor transparent helps to further improve the purity of the final recycled material, as polypropylene fragments not derived from the label can be removed directly through color sorting.

[0190] Preferably, the white and transparent fragments are separated from each other and carried out as separate streams in subsequent steps in the method of the first aspect. This additional separation can be performed simultaneously with the removal of polypropylene fragments that are neither white nor transparent (i.e., triaxial sorting between white, transparent and other colors), or it can be performed as binary sorting after the initial removal of polypropylene fragments that are neither white nor transparent.

[0191] Preferably, the color sorting in this subsequent step is performed using an optical sorting machine. In a broader sense, any optical sorting machine can be used to perform the sorting in this subsequent step. In this invention, "optical sorting machine" refers to a sorting unit that uses any form of electromagnetic (EM) radiation (visible or non-visible light) to distinguish fragments from a given recycling stream.

[0192] Preferably, the optical sorting machine in step c) performs sorting by a method selected from:

[0193] The camera system (operating in the visible light range of the EM spectrum) and visible light reflectance spectroscopy.

[0194] While performing color sorting in subsequent steps, other sorting criteria can be applied, such as additional sorting based on polyolefin type (removing any non-polypropylene fragments that may have been missed in previous sorting steps).

[0195] Suitable methods for sorting the recycled stream according to the polyolefin type include near-infrared spectroscopy, mid-infrared spectroscopy, high-speed laser spectroscopy, Raman spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. Near-infrared spectroscopy is particularly preferred.

[0196] In some implementations, a single sensor type (such as a near-infrared sensor or a camera system operating in the visible light range of the EM spectrum) can be used to distinguish multiple properties (e.g., color and polyolefin type). Furthermore, many near-infrared sensor units include a visible light reflectance unit or can be configured to simultaneously measure the near-infrared and visible light regions of the EM spectrum, meaning that a single sensor unit can utilize multiple detection methods.

[0197] Multiple detection methods and / or multiple sensors can be used to achieve sorting in subsequent steps.

[0198] Subsequent sorting steps can be achieved using simple sorting algorithms, where optical sensors are programmed to evaluate which fragments should be selected or returned based on a simple binary criterion. Alternatively, more sophisticated AI-based systems can be used to achieve more precise sorting.

[0199] Particularly preferred is that the aerated, extruded recycled polypropylene product (F1) or the extruded, aerated recycled polypropylene product (F3) is a mixed plastic polypropylene blend (PP) according to the second aspect.

[0200] All preferred features and alternative schemes of the mixed plastic polypropylene blend (PP) according to the second aspect are applicable in parallel to the first aspect.

[0201] Polypropylene (PP) blends are a type of mixed plastic.

[0202] In a second aspect, the present invention relates to a mixed plastic polypropylene blend (PP).

[0203] In this invention, the term "mixed plastic polypropylene blend" refers to a blend containing more than one polymer grade. This blend does not necessarily contain polymers other than polypropylene; blends containing only polypropylene fractions also constitute the mixed plastic polypropylene blends of this invention, at least partially derived from recycled materials. Such mixed plastic polypropylene blends typically consist of multiple different virgin grades collected during the recycling process; therefore, those skilled in the art can easily distinguish such mixed plastic polypropylene blends from virgin grades with defined modalities (e.g., unimodal, bimodal, etc.).

[0204] The melt flow rate (MFR2) of the polypropylene blend (PP) is 3.5 to 8.0 g / 10 min, more preferably 4.0 to 7.0 g / 10 min, and most preferably 4.5 to 6.5 g / 10 min, as determined by ISO 1133 at 230 °C and 2.16 kg.

[0205] Polypropylene (PP) blends can be characterized using the CRYSTEX QC method with trichlorobenzene (TCB) as a solvent. This method is described in the determination methods section below. In some cases, this method can yield more useful data (compared to, for example, methods based on xylene-based cold soluble fractions) because the crystalline fraction (CF) and soluble fraction (SF) more accurately correspond to the matrix and elastomer phases of the multiphase propylene-ethylene copolymer, respectively. Due to the differences in the separation methods of xylene extraction and the CRYSTEX QC method, the characteristics of the XCS / XCI fraction are not entirely the same in one respect as those of the crystalline / soluble (CF / SF) fraction in another respect. This means that the content and characteristics of the matrix phase (i.e., CF or XCI) and the elastomer phase (i.e., SF or XCS) can differ.

[0206] CRYSTEX QC analysis quantifies the properties of the soluble fraction (SF) and crystalline fraction (CF) in the polymer portion of blended plastic polypropylene (PP) blends; therefore, any non-polymer components, such as talc and titanium dioxide, are not taken into account.

[0207] The polymer portion of the polypropylene blend (PP) contains 0.0 to 5.0 wt% ethylene (C2 (total)) as determined by CRYSTEX QC analysis, more preferably 0.0 to 4.0 wt%, and most preferably 0.0 to 3.5 wt%.

[0208] Furthermore, the polymer portion of the polypropylene blend (PP) contains 93.0 to 100.0 wt% crystal fraction (CF) as determined by CRYSTEX QC analysis, more preferably 93.0 to 99.0 wt%, and most preferably 94.0 to 99.0 wt%.

[0209] Furthermore, the polymer portion of the polypropylene blend (PP) contains 0.0 to 7.0 wt% soluble fraction (SF) as determined by CRYSTEX QC analysis, more preferably 1.0 to 7.0 wt%, and most preferably 1.0 to 6.0 wt%.

[0210] Furthermore, the ethylene content (C2(CF)) of the polymer fraction of the mixed plastic polypropylene blend (PP), as determined by CRYSTEX QC analysis, is 0.0 to 5.0 wt%, more preferably 0.0 to 4.0 wt%, and most preferably 0.0 to 3.5 wt%.

[0211] Preferably, the intrinsic viscosity (iV(CF)) of the polymer fraction of the mixed plastic polypropylene blend (PP), as determined by CRYSTEX QC analysis, is 1.90 to 2.20 dL / g, more preferably 1.95 to 2.15 dL / g, and most preferably 2.00 to 2.10 dL / g.

[0212] As described above, the blended plastic polypropylene (PP) is at least partially derived from recycled materials. Preferably, at least 90 wt%, more preferably at least 95 wt%, and most preferably at least 98 wt% of the blended plastic polypropylene (PP) is derived from recycled materials.

[0213] If native polymers are available, these polymers are preferably masterbatch carrier polymers used to introduce additives during the compounding process.

[0214] The present invention has discovered that the blended plastic polypropylene (PP) of the second aspect has unexpectedly superior properties as a recycled material, including improved flexural modulus (relative to other recycled materials), and is particularly suitable for replacing virgin propylene homopolymers in polypropylene compositions without sacrificing mechanical properties (which is usually the case when recycled materials are added).

[0215] The polypropylene blend (PP) according to embodiments of the present invention also has a distinctive light gray color, primarily due to the presence of residual ink that may not have been 100% removed during the recycling process. The more efficient the washing process, the less noticeable this gray color becomes (i.e., the whiter the polypropylene blend (PP)). Other non-polypropylene components may also contribute to the ashing effect, either directly or by forming degradation products that lead to the ashing effect.

[0216] Therefore, preferably, the mixed plastic polypropylene blend (PP) conforms to the CIELAB color space as determined by ISO 11664-4. )for:

[0217] i) The value is 60.0 to 90.0, more preferably 70.0 to 85.0;

[0218] ii) The range is from -5.0 to 0.0; and

[0219] iii) The range is from 0.0 to 20.0.

[0220] This CIELAB color space is typical of exceptionally pure recycled materials (i.e., whiter than ordinary recycled materials, but not as white as the white virgin polymer grades).

[0221] While it is possible to obtain the native grades of colors within this CIELAB color space, this is typically achieved by adding a small amount of black pigment (such as carbon black) to a white polymer grade, meaning that the native grade will contain only white and black pigments.

[0222] In the polypropylene (PP) blends of this invention, the gray color does not originate from the addition of black pigment, but rather from residual inks of various colors. Typical black pigments contain carbon (i.e., carbon black), white pigments contain, for example, titanium (in titanium dioxide), while the blend inks contain a variety of different elements that can be detected by X-ray fluorescence spectrometry (XRF). In otherwise identical gray virgin materials, the same wide range of different elements is not detectable.

[0223] Therefore, the following elements detected by XRF analysis indicate the recycling sources of the blended plastic polypropylene (PP). For the following XRF element contents, the use of "preferred" does not mean that higher element contents are always better, but rather that "more preferred" and "most preferred" embodiments more accurately define the recycling sources of the blended plastic polypropylene (PP).

[0224] Therefore, preferably, the aluminum (Al) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectroscopy (XRF) is at least 60 ppm, more preferably at least 90 ppm, and most preferably at least 120 ppm.

[0225] More preferably, the iron (Fe) content of the mixed plastic polypropylene blend (PP) determined by X-ray fluorescence spectrometry (XRF) is at least 30 ppm, more preferably at least 50 ppm, and most preferably at least 80 ppm.

[0226] More preferably, the sodium (Na) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectrometry (XRF) is at least 20 ppm, more preferably at least 50 ppm, and most preferably at least 80 ppm.

[0227] More preferably, the sulfur (S) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectrometry (XRF) is at least 5 ppm, more preferably at least 15 ppm, and most preferably at least 30 ppm.

[0228] More preferably, the zinc (Zn) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectrometry (XRF) is at least 15 ppm, more preferably at least 25 ppm, and most preferably at least 30 ppm.

[0229] Particularly preferably, the blended plastic polypropylene (PP) blend has at least three of the following properties, more preferably all of them:

[0230] a) The iron (Fe) content, as determined by X-ray fluorescence spectrometry (XRF), is at least 30 ppm;

[0231] b) The sodium (Na) content, as determined by X-ray fluorescence spectrometry (XRF), is at least 20 ppm;

[0232] c) The sulfur (S) content, as determined by X-ray fluorescence spectrometry (XRF), is at least 5 ppm;

[0233] d) The zinc (Zn) content, as determined by X-ray fluorescence spectrometry (XRF), is at least 15 ppm.

[0234] Such combinations of Fe, Na, S, and / or Zn were not observed in the native grades. Therefore, the presence of these elements suggests a recycled source for the blended plastic polypropylene (PP), especially when combined with the aforementioned CIELAB color space.

[0235] Particularly preferably, the sum of the iron (Fe), sodium (Na), sulfur (S) and zinc (Zn) contents determined by X-ray fluorescence spectrometry (XRF) is at least 80 ppm, more preferably at least 150 ppm, and most preferably at least 300 ppm.

[0236] Similarly, the presence of such a high Al content clearly indicates the recycled source of the blended plastic polypropylene (PP), especially for recycled materials derived from the label.

[0237] More preferably, the bromine (Br) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectrometry (XRF) is at least 0.5 ppm, more preferably at least 1.0 ppm, and most preferably at least 2.0 ppm.

[0238] More preferably, the potassium (K) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectrometry (XRF) is at least 1 ppm, more preferably at least 5 ppm, and most preferably at least 15 ppm.

[0239] More preferably, the strontium (Sr) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectrometry (XRF) is at least 1 ppm, more preferably at least 5 ppm, and most preferably at least 10 ppm.

[0240] More preferably, the calcium (Ca) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectroscopy (XRF) is at least 100 ppm, more preferably at least 500 ppm, and most preferably at least 800 ppm.

[0241] More preferably, the chlorine (Cl) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectrometry (XRF) is at least 25 ppm, more preferably at least 35 ppm, and most preferably at least 40 ppm.

[0242] More preferably, the titanium (Ti) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectroscopy (XRF) is at least 200 ppm, more preferably at least 600 ppm, and most preferably at least 1000 ppm.

[0243] More preferably, the magnesium (Mg) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectrometry (XRF) is at least 50 ppm, more preferably at least 80 ppm, and most preferably at least 90 ppm.

[0244] More preferably, the silicon (Si) content of the mixed plastic polypropylene blend (PP) as determined by X-ray fluorescence spectroscopy (XRF) is at least 50 ppm, more preferably at least 100 ppm, and most preferably at least 120 ppm.

[0245] Another indicator of the recycled source of polypropylene (PP) blends can be obtained by measuring the phosphorus (P) content.

[0246] The presence of phosphorus in polymer grades is almost 100% attributable to phosphorus-based stabilizers, such as antioxidants. In almost all commercially available grades, the amount of such additives in the virgin grade is very consistent, corresponding to the amount needed to adequately stabilize the polymer grade at the expected number of compounding steps (considering that oxidation is most likely to occur in these high-temperature compounding steps), without incurring unnecessary costs due to excessive stabilizer use. When consumer products are recycled, most of the stabilizers have been consumed (i.e., they will be oxidized and can no longer be used as antioxidants), and more phosphorus-based stabilizers need to be added to stabilize the recycled grades. This means that the phosphorus present in recycled materials is either a) at the typical level of the virgin grade, but mostly oxidized; or b) much higher than the typical level of the virgin grade.

[0247] The total phosphorus content can be analyzed by X-ray fluorescence spectrometry (XRF), while the ratio of the unoxidized stabilizer tris(2,4-di-tert-butylphenyl) phosphite to the oxidized stabilizer tris(2,4-di-tert-butylphenyl) phosphate can be evaluated by HPLC analysis.

[0248] Therefore, preferably, the content of tris(2,4-di-tert-butylphenyl) phosphate, as determined by HPLC analysis, is 60% to 100% relative to the total content of tris(2,4-di-tert-butylphenyl) phosphate and tris(2,4-di-tert-butylphenyl) phosphate, and the total phosphorus content, as determined by X-ray fluorescence spectrometry (XRF), is 15 to 60 ppm.

[0249] This is consistent with the grade of recycled material that has not been further additiveed.

[0250] Alternatively, preferably, the total phosphorus content, as determined by X-ray fluorescence spectroscopy (XRF), is greater than 60 ppm. This is consistent with recycled material grades that have been further supplemented with additives using additional phosphorus sources.

[0251] Furthermore, preferably, the inorganic residue content of the polypropylene blend (PP) as determined by thermogravimetric analysis (TGA) according to DIN 1172 is 0.10 to 7.5 wt% relative to the total weight of the blended plastic polypropylene blend (PP), more preferably 0.20 to 5.0 wt%, and most preferably 0.5 to 4.0 wt%.

[0252] Preferably, the total volatile organic compound (TVOC) content of the mixed plastic polypropylene blend (PP), as determined by the measurement method given in the determination method, is 0 to 25 µg / g, more preferably 0 to 18 µg / g, and most preferably 0 to 15 µg / g.

[0253] Particularly preferred is that the mixed plastic polypropylene blend (PP) is obtained by the method according to the first aspect, and more preferably produced by the method according to the first aspect.

[0254] All preferred features and alternatives of the first aspect are applicable in analogous manner to mixed plastic polypropylene blends (PP) obtained (more preferably produced according to the method of the first aspect) according to the method of the first aspect.

[0255] Products

[0256] In a third aspect, the present invention relates to articles comprising a blend of polypropylene (PP) plastics of the second aspect, wherein the articles are selected from labels and films.

[0257] Preferably, relative to the total weight of the article, the article of the third aspect comprises at least 90 wt%, more preferably at least 95 wt%, and most preferably at least 98 wt% of the mixed plastic polypropylene blend (PP) of the second aspect.

[0258] If there are other polymers besides the polypropylene blend (PP) of the second aspect, these polymers may be modifiers or virgin polymer grades used to change the properties of the polypropylene blend (PP).

[0259] All preferred features and alternatives of the second aspect of the mixed plastic polypropylene blend (PP) are applicable in comparison to articles comprising the third aspect.

[0260] use

[0261] In a final aspect, the present invention relates to the use of a blend of plastic polypropylene (PP) for the production of polypropylene-containing labels containing recycled materials.

[0262] All preferred features and alternatives of the blended plastic polypropylene (PP) of the second aspect are applicable to the use of the blended plastic polypropylene (PP) of the fourth aspect. Example

[0263] 1. Measurement Method

[0264] Unless otherwise defined, the following terms and measurement methods apply to the above general description of the invention (including the claims) and the following embodiments.

[0265] CRYSTEX QC Analysis

[0266] Methods for crystallization and soluble fractionation

[0267] The crystalline fraction (CF) and soluble fraction (SF) of polypropylene (PP) compositions, as well as the comonomer content and intrinsic viscosity of each fraction, were analyzed using a Polymer Char (Valencia, Spain) CRYSTEX instrument. Detailed information on this technique and method can be found in the literature (Ljiljana Jeremic, Andreas Albrecht, Martina Sandholzer and Markus Gahleitner (2020) Rapid characterization of high-impact ethylene–propylene copolymer composition by crystallization extraction separation: comparability to standard separation methods, International Journal of Polymer Analysis and Characterization, 25:8, 581-596).

[0268] The crystalline and amorphous fractions were separated by a temperature cycle of dissolution at 160 °C, crystallization at 40 °C, and redissolution in 1,2,4-trichlorobenzene at 160 °C. SF and CF were quantified and the ethylene content (C2) was determined using an integrated infrared detector (IR4), and the intrinsic viscosity (IV) was determined using an online dual-capillary viscometer.

[0269] The IR4 detector is a multi-wavelength detector that measures two different wavelengths (CH3 stretching vibration, centered at approximately 2960 cm⁻¹). -1 (at location) and CH stretching vibration (2700-3000 cm) -1 The infrared absorbance of the IR4 detector is used to determine the concentration and ethylene content of ethylene-propylene copolymers. The IR4 detector is calibrated with a series of eight EP copolymers, with known ethylene contents ranging from 2 wt% to 69 wt%. 13 (C-NMR determination), the concentration of each copolymer ranged from 2 to 13 mg / mL. To simultaneously correct for both concentration and ethylene content (for the various polymer concentrations that may occur in Crystex analysis), the following calibration equation was applied:

[0270] (Equation 1)

[0271] (Equation 2)

[0272] The constants a to e in Equation 1 and the constants a to f in Equation 2 were determined by least squares regression analysis.

[0273] Use the following formula to convert CH3 / 1000C to ethylene content (wt%):

[0274] (Equation 3)

[0275] The XS calibration curves correlated the amounts of the soluble fraction (SF) and crystalline fraction (CF) to the amounts of the "cold xylene soluble" (XCS) fraction and the "cold xylene insoluble" (XCI) fraction, respectively, as determined by the standard gravimetric method according to ISO 16152. The XS calibration curves were obtained by testing various EP copolymers with XS contents ranging from 2 to 31 wt%. The determined XS calibration curves were linear.

[0276] (Equation 4)

[0277] The intrinsic viscosity (IV) of the parent EP copolymer and its soluble and crystalline fractions was determined using an online dual-capillary viscometer and correlated to the corresponding IV obtained according to standard methods in decahydronaphthalene according to ISO 1628-3. Calibration was performed using various EP and PP copolymers with IV = 2-4 dL / g. The obtained calibration curves were linear.

[0278] (Equation 5)

[0279] The sample to be analyzed is weighed at a concentration of 10 mg / ml to 20 mg / ml. To avoid injecting gels and / or polymers (e.g., PET and PA) that may be insoluble in TCB at 160°C, the weighed sample is placed in a stainless steel mesh with a MW 0.077 / D 0.05 mm diameter.

[0280] After filling vials with 1,2,4-TCB containing 250 mg / L 2,6-tert-butyl-4-methylphenol (BHT) as an antioxidant, the sample was dissolved at 160°C until completely dissolved, typically for 60 minutes with continuous stirring at 400 rpm. To prevent sample degradation, the polymer solution was covered with a nitrogen atmosphere during the dissolution process.

[0281] A predetermined volume of sample solution is injected into a column packed with an inert support, where the sample crystallizes and the soluble fraction is separated from the crystalline fraction. This process is repeated twice. During the first injection, the entire sample is measured at high temperature to determine the IV [dl / g] and C2 [wt%] of the PP composition. During the second injection, the soluble fraction (at low temperature) and crystalline fraction (at high temperature) of the crystallization cycle, as well as the crystallization cycle (wt% SF, wt% C2, IV), are measured.

[0282] melt flow rate

[0283] Melt flow rate (MFR) was determined according to ISO 1133, with units of g / 10 min. MFR characterizes the flowability of a polymer, and thus its processing properties. A higher melt flow rate generally corresponds to a lower polymer viscosity. The MFR2 of polypropylene was determined at 230°C and a load of 2.16 kg.

[0284] X-ray fluorescence spectroscopy (XRF)

[0285] The instrument used for XRF measurements was the Malvern Panalytical Zetium (2.4 kW) wavelength dispersive XRF instrument. The instrument was calibrated using Malvern Panalytical's Adpol, RoHS, and Toxel standard samples, as well as a set of custom calibration standard samples (hereinafter referred to as "custom"), according to the table below.

[0286]

[0287] The analysis was performed on a plate with a diameter of 40 mm and a thickness of 2 mm under vacuum.

[0288] This method is used to determine the quantitative content of Na, Mg, Al, Si, P, S, Ca, Ti, Zn, Cu, Br, Cl, K, Sr and Fe elements in a given polyolefin matrix, and the content must be within the range defined by these standard samples.

[0289] The content of each specific element was evaluated using the following criteria (LOD = limit of detection):

[0290]

[0291] For elements not covered by the standard samples, or elements whose content exceeds the range of the calibration standard samples, a semi-quantitative mode (Omnian software from Malvern Panalytical) is used for analysis. For elements not covered by the calibration standard samples, if the corresponding peak is not visible, its value is not reported, and therefore it cannot be analyzed using Omnian software.

[0292] The CH content required for semi-quantitative evaluation using Omnian software is estimated by the software itself.

[0293] In this invention, the presence of multiple elements that would not normally appear in native polymer grades (at least certainly not in combination) indicates that a particular polypropylene grade is at least partially derived from recycled materials.

[0294] The table below lists typical data for several native and recycled grades (i.e., r-PP), which indicate the presence of certain elements that reveal the recycling source:

[0295]

[0296] - Measured before the addition of additives (i.e., before the addition of additional, fresh stabilizer, while all other r-PP values ​​are measured after the addition of additives).

[0297] - Observed only in some samples, not all.

[0298] HPLC analysis

[0299] After extraction with ethyl acetate, the content of antioxidants (such as Irganox® 1010 and Irgafos® 168, namely pentaerythritol tetrakis(3-(3',5'-di-tert-butyl-4-hydroxyphenyl)propionate and tris(2,4-di-tert-butylphenyl) phosphite, and their oxidized derivatives) was determined by high-performance liquid chromatography (HPLC). First, approximately 10 g of the sample was cryogenically milled under liquid nitrogen assistance. Then, 0.5 g of the milled sample was extracted with ethyl acetate as the solvent. The extraction was carried out at 95°C for 90 minutes with continuous stirring. After the mixture was cooled to room temperature again, it was filtered and analyzed by HPLC to quantify the antioxidants. The HPLC system was equipped with a C18 column for separation and a diode array detector (DAD) for detection.

[0300] The presence of phosphorus in polymer grades is almost entirely attributable to phosphorus-based stabilizers, such as antioxidants. In almost all commercially available grades, the amount of such additives in the virgin grade is very consistent, corresponding to the amount needed to adequately stabilize the polymer grade for the expected number of compounding steps (considering that oxidation is most likely to occur in these high-temperature compounding steps), without incurring unnecessary costs due to excessive stabilizer use. When consumer products are recycled, most of the stabilizers have been consumed (i.e., they will have been oxidized and can no longer be used as antioxidants), and more phosphorus-based stabilizers need to be added to stabilize the recycled grades. This means that the phosphorus present in the recycled material will either a) be at the typical level of the virgin grade, but mostly oxidized; or b) be significantly higher than the typical level of the virgin grade (see Virgin Polymers 1 to 3 in the table above).

[0301] The table below discloses typical values ​​for recycled materials corresponding to case a) (i.e., no additives have been added in the mechanical recycling process) and case b) (i.e., additives have been added in the mechanical recycling process).

[0302]

[0303] #1 to #4 have typical phosphorus contents as determined by XRF, but a high proportion of Irgafos are present in oxidized form; while #5 to #10 have higher phosphorus contents as determined by XRF than those observed in virgin polypropylene grades.

[0304] Further testing has been illustrated in [the diagram]. Figure 1 In the middle, it precisely shows the same trend (Note: the original brand name will be located in...). Figure 1Somewhere to the lower left, the total P content is low, at 28-52 ppm, and the percentage of oxidized Irgafos 168 is also low.

[0305] TVOC – Total Volatile Organic Compounds

[0306] The total volatile organic compound (TVOC) content was determined according to HS-GC-FID / MS.

[0307] TVOC is measured directly on the granular sample (i.e., without any grinding or other size reduction treatment).

[0308] Headspace setting: Hold at 100°C for 2 hours, with a sample size of 1 gram.

[0309] Specific components are quantified using signals from the FID chromatogram and external standard samples. TVOC is semi-quantitatively determined using all peaks in the sample's FID chromatogram in toluene equivalent form.

[0310] The analysis was performed twice.

[0311] The content of iPP, polystyrene, polyethylene (and ethylene-containing copolymers), polyethylene terephthalate and polyamide-6.

[0312] Sample preparation:

[0313] All calibration samples and samples to be analyzed were prepared on fused plates using a similar method.

[0314] Approximately 2 to 3 g of the compound to be analyzed was melted at 190 °C. Subsequently, a pressure of 60 to 80 bar was applied in a hydraulic heating press for 20 seconds. Next, the sample was cooled to room temperature in a cold press for 40 seconds under the same pressure to control the morphology of the compound. The thickness of the plates was controlled by a 2.5 cm × 2.5 cm metal calibration frame plate with a thickness of 100 to 200 μm (depending on the MFR of the sample); two plates were prepared in parallel under the same conditions. The thickness of each plate was measured before any FTIR measurements; all plates had a thickness of 100 to 200 μm.

[0315] To control the surface of the board and avoid any interference during the measurement process, all boards were pressed between two layers of double-sided silicone release paper.

[0316] For powder samples or non-uniform compounds, the pressing process is repeated three times to improve homogeneity by pressing and cutting the sample under the same conditions as described above.

[0317] Spectrometer:

[0318] Using a standard transmission FTIR spectrometer, such as a Bruker Vertex 70 FTIR spectrometer, the settings are as follows:

[0319] - Spectral range: 4000-400cm -1

[0320] - Aperture: 6mm

[0321] - Spectral resolution: 2cm -1

[0322] - 16 background scans, 16 spectral scans

[0323] - Zero-fill coefficient for interferogram: 32

[0324] -Norton Beer strong anodizing.

[0325] The spectra were recorded and analyzed using Bruker Opus software.

[0326] Calibration sample:

[0327] Since FTIR is an auxiliary method, several calibration standard samples are mixed to cover the target analytical range, typically as follows:

[0328] -PA: 0.2wt% to 2.5wt%

[0329] -PS: 0.1wt% to 5wt%

[0330] -PET: 0.2wt% to 2.5wt%

[0331] -PVC: 0.1wt% to 4wt%

[0332] The compounds used the following commercially available materials: Borealis HC600TF for iPP, Borealis FB3450 for HDPE, for the target polymers such as RAMAPET N1S (Indorama Polymer) for PET, Ultramid® B36LN (BASF) for polyamide 6, Styrolution PS 486N (Ineos) for high-impact polystyrene (HIPS), and Inovyn PVC 263B (powder form) for PVC.

[0333] All compounds were produced on a small scale in a Haake kneader at temperatures below 265°C and for less than 10 minutes to avoid degradation.

[0334] Antioxidants, such as Irgafos 168 (3000 ppm), have also been added to minimize degradation.

[0335] calibration:

[0336] The FTIR calibration principle is the same for all components: the intensity of a specific FTIR band divided by the plate thickness is correlated with the component content determined by 1H or 13C solution NMR on the same plate.

[0337] Each specific FTIR absorption band was chosen because its intensity increases with increasing component concentration, regardless of the composition of the calibration standard sample or the actual sample, and it is isolated from the remaining peaks.

[0338] This method is described in the publication of Signoret et al. (“Alterations of plastic spectra in MIR and the potential impacts on identification towards recycling”, Resources, Conservation and Recycling journal, 2020, Vol. 161, No. 104980).

[0339] The wavelength for each calibration band is:

[0340] -PA:3300cm-1

[0341] PS: 1601cm-1

[0342] -PET: 1410cm-1

[0343] -PVC: 615cm-1

[0344] -iPP: 1167cm-1

[0345] A linear calibration is constructed for each polymer component i (based on the linear relationship of the Beer-Lambert law). A typical linear correlation for this type of calibration is shown below:

[0346]

[0347] In the formula,

[0348] x i It is the fraction of polymer component i (in wt%).

[0349] E i It is the absorbance intensity of a specific wavelength band associated with polymer component i (in au units, see above for values).

[0350] d is the thickness of the sample plate;

[0351] A i and B i These are the two correlation coefficients determined for each calibration curve.

[0352] For the C2-rich fraction, no specific isolated bands were found; therefore, the C2-rich fraction was estimated indirectly.

[0353]

[0354] The content of chalk and talc is estimated as "semi-quantitative". Therefore, the C2-rich content is also estimated as "semi-quantitative".

[0355] For each calibration standard sample, the amount of each component was determined, where feasible, by... 1 H or 13 C solution-state NMR was used as the primary method for determination (except for PA). NMR measurements were performed on the same FTIR plate used to construct the FTIR calibration curve.

[0356] Talc and chalk content

[0357] Talc and chalk were measured using a Perkin Elmer TGA 8000 thermogravimetric analysis (TGA). Approximately 15–25 mg of material was placed in a platinum dish. The temperature was equilibrated at 50 °C for 10 minutes, then increased to 950 °C at a heating rate of 20 °C / min under nitrogen. The weight loss (WCO2) between approximately 550 °C and 700 °C was attributed to CO2 derived from CaCO3, and therefore the chalk content was assessed as follows:

[0358] Chalk content = 100 / 44 × WCO2

[0359] The temperature was then reduced to 300°C at a cooling rate of 20°C / min. The gas was then switched to oxygen, and the temperature was raised again to 900°C. The weight loss in this step is attributed to carbon black (Wcb). Given the contents of carbon black and chalk, the ash content excluding chalk and carbon black is calculated as follows:

[0360] Ash content = (Residual ash) - 56 / 44 × WCO2 - Wcb

[0361] The ash residue refers to the weight percentage measured at 850°C during the first step under nitrogen atmosphere. It is estimated that the ash content is the same as the talc content of the recycled material studied.

[0362] Flexural modulus was determined according to ISO 178 Method A (three-point bending test) on an 80 mm × 10 mm × 4 mm specimen. The test speed was 2 mm / min, and the span length was 16 times the thickness. The test temperature was 23 ± 2°C. Injection molding was performed according to ISO 19069-2, with a melt temperature of 230°C for all materials, regardless of melt flow rate.

[0363] CIELAB

[0364] This method is used to measure sheet color and conforms to ISO 11664-4. Injection-molded sheets with dimensions of 60×60×2mm are prepared from granules according to ISO standard 19069-2:2020 (PP), and then CIELAB measurements are performed. Three standard color values, X, Y, and Z, are measured using a spectrophotometer for calculation. , , Values ​​and their color differences.

[0365] Total content of inorganic residues

[0366] The content of inorganic residues was determined by thermogravimetric analysis (TGA) according to DIN 1172.

[0367] 1. Example

[0368] In the following experiments, the following recycling stream was used as the precursor recycling stream:

[0369] A1: Swedish post-consumer plastic waste stream, rich in post-consumer flexible PP products.

[0370] A2: German post-consumer plastic waste stream, compliant with DSD 323-2 specifications.

[0371] A3: Post-consumer polypropylene waste stream obtained as a byproduct of bottle recycling processes.

[0372] Unlike A1 and A2, A3 contains at least 85 wt% polypropylene-containing labels (in fact, A3 is essentially composed of polypropylene-containing labels).

[0373] For the comparative example (which uses a precursor recovery stream that does not contain at least 85 wt% of a polypropylene-labeled precursor), follow General Procedure A:

[0374] Step 1: Color sort the precursor recovery stream (the criteria for this sorting step vary depending on the experiment, see below);

[0375] Step 2: The sorted products from Step 1 are first cleaned in a low-temperature alkaline cleaning step, and then cleaned in a high-temperature alkaline cleaning step.

[0376] Step 3: Use a near-infrared sorter to further sort the cleaning product from Step 2 to remove any fragments that do not contain polypropylene;

[0377] Step 4: Melt extrusion is performed on the sorted product from Step 3 to form recycled polypropylene grades.

[0378] CE1 involves processing the precursor A1 through a general procedure A, wherein step 1 sorts out transparent fragments (i.e., removes colored fragments).

[0379] CE2 involves processing the precursor A2 through a general procedure A, in which step 1 sorts out transparent fragments.

[0380] CE3 involves processing the precursor A2 through a general procedure A, in which step 1 is not performed.

[0381] CE4 involves processing precursor A2 through a general procedure A, where step 1 only sorts out colored fragments (i.e., removes transparent fragments).

[0382] For embodiments of the invention (which use a precursor recovery stream explicitly containing at least 85 wt% of a polypropylene-labeled precursor), follow general step B:

[0383] Step 1: The precursor A3 was cleaned in a single high-temperature cleaning step (the conditions varied in each experiment, see below), in which additional substances with different densities than polypropylene were also removed by flotation separation.

[0384] Step 2: Use a wind-powered screening machine to separate the product from Step 1 into heavy fractions (i.e., rigid fragments) and light fractions (i.e., flexible fragments).

[0385] Step 3: Melt extrusion of the light fraction from Step 2 to form a recycled polypropylene grade.

[0386] (Note: Since the precursor recovery stream A3 does not contain a large amount of pigment-containing polypropylene (i.e., the pigment is dispersed in the polypropylene matrix, rather than as surface ink), a color sorting step (i.e., step 1 of general procedure A) is not required.)

[0387] IE1 involves treating precursor A3 through a general procedure B, wherein the washing step 1 is performed at 70°C for 10 minutes using a wash solution containing 1.8 wt% NaOH and 0.18 wt% TubiWash EYE detergent. This washing step is insufficient to remove at least 85 wt% of the existing ink. IE1's process is a laboratory-scale recycling process.

[0388] IE2 involves treating precursor A3 through a general procedure B, where step 1, washing, is performed at 80°C for 10 minutes using a wash solution containing 1.8 wt% NaOH and 0.18 wt% TubiWash EYE detergent. This washing step is insufficient to remove at least 85 wt% of the existing ink. IE2's process is a laboratory-scale recycling process.

[0389] IE3 involves treating precursor A3 through a general procedure B, wherein the washing step 1 is performed at 70°C for 60 minutes using an aqueous wash solution containing 3.0 wt% NaOH and 0.30 wt% TubiWash EYE detergent. This washing step is sufficient to remove at least 85 wt% of the existing ink. The IE3 process is a laboratory-scale recycling process.

[0390] IE4 involves treating precursor A3 through a general procedure B, wherein the washing step 1 is performed at 80°C for 60 minutes using a washing solution containing 3.0 wt% NaOH and 0.30 wt% TubiWash EYE detergent. This washing step is sufficient to remove at least 85 wt% of the existing ink. The IE4 process is a laboratory-scale recycling process.

[0391] IE5 involves treating precursor A3 through a general procedure B, where step 1, washing, is performed at 80°C for 20 minutes using a water wash containing 3.0 wt% NaOH and 0.30 wt% TubiWash EYE cleaner. This washing step is sufficient to remove at least 85 wt% of the existing ink. IE5 is an industrial-scale recycling process. Furthermore, hydrocyclones are used instead of flotation / sinking separation to remove materials with densities different from polypropylene.

[0392] Those skilled in the art will understand that there are differences between laboratory-scale and industrial-scale cleaning processes, with laboratory-scale processes requiring longer cleaning times due to lower agitation efficiency. In terms of cleaning efficiency, a 20-minute industrial-scale cleaning of IE5 is roughly equivalent to a 60-minute laboratory-scale cleaning of IE4.

[0393] Experiments CE1 to CE4 and IE1 to IE5 each produced mixed plastic polypropylene blends, the properties of which are listed in Table 1.

[0394] Table 1. Characteristics of the Invention and Comparative Polypropylene Blends

[0395]

[0396]

[0397] - Below the limit of detection (LOD)

[0398] - Due to the low SF content, iV(SF) and C2(SF) cannot be accurately measured.

[0399] -No clearly visible peaks in the XRF spectrum

[0400] As shown in Table 1, the method of using precursor raw materials derived from polypropylene labels in this invention can obtain high-purity recycled products (although the precursor recycled stream is a byproduct of PET recycling, the filler and PS content is low, and the PET content is also extremely low), with its MFR within a narrow and defined range, and low C2 and other contaminant content. Furthermore, by selecting appropriate washing conditions, a purity exceeding 70% can be obtained. value.

[0401] Further experiments showed that when general procedure B was performed under conditions sufficient to remove 85% of the ink (e.g., IE3, IE4, and IE5 conditions), the resulting recycled material grade had a polypropylene content of 98 wt% (relative to the total polymer content, i.e., ignoring fillers such as talc and chalk).

[0402] By adding an additional sorting step before step 1 of general procedure B, in which an optical (e.g., near-infrared) sorter removes all non-polypropylene fragments, the polypropylene content can be increased to 99 wt% (relative to the total polymer content).

[0403] Furthermore, by adding an additional sorting step between steps 2 and 3 of General Procedure B, where an optical (e.g., near-infrared) sorter separates by color, approximately 40 wt% white fraction containing a significantly higher content of inorganic filler (approximately 7 wt%) can be obtained; approximately 50 wt% transparent fraction (also referred to above as the "natural color" fraction) containing less than 0.5 wt% inorganic filler; and approximately 10 wt% colored fraction containing incompletely deinked fragments and polyethylene fragments (from polyethylene bottle caps that escaped previous sorting steps). The white and transparent fractions can be used for various applications, while the colored fraction can be fed into other recycling processes or used for energy recovery (incineration capacity). Figure 2 The image shows the pellets made from these fractions. The CIELAB value of the white pellets is [value missing]. , and The CIELAB value of transparent granules is... , and .

Claims

1. A method for mechanically recycling polypropylene, comprising the following steps in a given sequence: a) Provide a precursor polypropylene recycled stream (A), wherein the precursor polypropylene recycled stream (A) contains at least 85 wt% polypropylene-containing label based on the total weight of the precursor polypropylene recycled stream (A); b) Optionally, the precursor polypropylene recovery stream (A) may be sorted according to the polymer type to remove any fragments containing polymers other than polypropylene, thereby generating a purified polypropylene recovery stream (B). c) The purified polypropylene recovery stream (B) is cleaned in one or more cleaning steps, or if step b) is not present, the precursor polypropylene recovery stream (A) is cleaned in one or more cleaning steps to obtain a cleaned polypropylene stream (C). d) Optionally, the washed polypropylene stream (C) is separated into heavy fraction and light fraction polypropylene recovery stream (D). e) Melt-extrude the light-grade polypropylene recycled stream (D), preferably granulating it, or, if step d) is absent, melt-extrude the washed polypropylene stream (C), preferably granulating it, and preferably adding an additive (Ad) in the molten state, thereby forming an extruded, preferably granulated, recycled polypropylene composition (E); and f) Optionally, the recycled polypropylene composition (E) is ventilated to remove volatile organic compounds, thereby generating an ventilated recycled polypropylene product (F1). In this case, the order of steps f) and e) can be interchanged, such that the light fraction polypropylene recycled stream (D) is first aerated, or if step d) is absent, the cleaned polypropylene stream (C) is aerated to form aerated recycled polypropylene sheets (F2), which are then extruded, preferably with additives (Ad) added in the molten state, to form an extruded, preferably granulated, aerated recycled polypropylene product (F3).

2. The method according to claim 1, wherein, The step of providing a precursor polypropylene recycled stream (A) containing at least 85 wt% of a polypropylene-labeled precursor polypropylene recycled stream (A) by means of: separating the polypropylene-labeled item from the bottle, preferably from the PET-containing bottle, and then collecting the polypropylene-labeled item to obtain the precursor polypropylene recycled stream (A).

3. The method according to claim 1, wherein, The step of providing a precursor polypropylene recycled stream (A) containing at least 85 wt% of polypropylene-labeled precursor polypropylene recycled stream (A) by means of: separating the polypropylene-labeled material attached to a rigid article containing a polyolefin by an adhesive, sorting the polypropylene-labeled material from the rigid article containing the polyolefin and collecting the polypropylene-labeled material, thereby obtaining the precursor polypropylene recycled stream (A).

4. The method according to any one of the preceding claims, wherein, One or more of the cleaning steps in step c) continue until at least 85% of all ink is removed from the purified polypropylene recovery stream (B), or if step b) is not present, at least 85% of all ink is removed from the precursor polypropylene recovery stream (A).

5. The method according to any one of the preceding claims, wherein, At least one of the cleaning steps in step c) uses an alkaline water washing solution and is carried out at a temperature of 40 to 85°C.

6. The method according to any one of the preceding claims, wherein, The method further includes the following steps: color sorting of polypropylene fragments in the cleaned polypropylene stream (C), the light-grade polypropylene recovery stream (D), or the aerated recycled polypropylene sheet (F2) to remove all non-white or transparent polypropylene fragments.

7. A blend of polypropylene (PP) plastics, wherein the blend of polypropylene (PP) plastics has a melt flow rate (MFR2) of 3.5 to 8.0 g / 10 min, as determined according to ISO 1133 at 230°C and 2.16 kg. in, The polymer portion of the mixed plastic polypropylene blend (PP) has: i) The ethylene content (C2 (total)) determined by CRYSTEX QC analysis is 0.0 to 5.0 wt%; ii) The crystalline fraction (CF) content, as determined by CRYSTEX QC analysis, is 93.0 to 100.0 wt%; iii) The soluble fraction (SF) content, as determined by CRYSTEX QC analysis, is 0.0 to 7.0 wt%; and iv) The ethylene content (C2(CF)) of the crystalline fraction determined by CRYSTEX QC analysis is 0.0 to 5.0 wt%.

8. The mixed plastic polypropylene blend (PP) according to claim 7, wherein, At least 90 wt%, more preferably at least 95 wt%, and even more preferably at least 98 wt% of the blended plastic polypropylene (PP) is derived from recycled materials.

9. The mixed plastic polypropylene blend (PP) according to claim 7 or 8, wherein, The mixed plastic polypropylene blend (PP) is measured in the CIELAB color space according to ISO 11664-4. )for: i) The value is 60.0 to 90.0, more preferably 70.0 to 85.0; ii) The range is from -5.0 to 0.0; as well as iii) The range is from 0.0 to 20.

0.

10. The mixed plastic polypropylene blend (PP) according to any one of claims 7 to 9, wherein, The mixed plastic polypropylene blend (PP) has the following properties: a) The aluminum (Al) content, as determined by X-ray fluorescence spectrometry (XRF), is at least 60 ppm; and / or have at least three of the following characteristics, more preferably all of the following characteristics: b) The iron (Fe) content, as determined by X-ray fluorescence spectrometry (XRF), is at least 20 ppm; c) The sodium (Na) content, as determined by X-ray fluorescence spectrometry (XRF), is at least 30 ppm; d) The sulfur (S) content, as determined by X-ray fluorescence spectrometry (XRF), is at least 5 ppm; e) The zinc (Zn) content, as determined by X-ray fluorescence spectrometry (XRF), is at least 15 ppm.

11. The blended plastic polypropylene (PP) blend according to any one of claims 7 to 10, wherein, The total volatile organic compound (TVOC) content of the mixed plastic polypropylene blend, as determined by the measurement method given in the determination method, is 0 to 25 µg / g, more preferably 0 to 18 µg / g, and most preferably 0 to 15 µg / g.

12. The method according to any one of claims 1 to 6, wherein, The method produces a mixed plastic polypropylene blend (PP) according to any one of claims 7 to 11.

13. The blended plastic polypropylene (PP) blend according to any one of claims 7 to 11, wherein, The mixed plastic polypropylene blend is prepared by the method according to any one of claims 1 to 6.

14. An article comprising the mixed plastic polypropylene blend (PP) of any one of claims 7 to 11 or 13, preferably, wherein the content of the mixed plastic polypropylene blend (PP) relative to the total weight of the article is at least 90 wt%, more preferably at least 95 wt%, and most preferably at least 98 wt%, wherein... The products are selected from labels and films.

15. Use of the blended plastic polypropylene (PP) of any one of claims 7 to 11 or 13 for the production of polypropylene labels containing recycled materials.

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