FIELD OF THE INVENTION

The present invention relates to a food contact plastic material that may be easily separated from other types of plastic for recycling purposes. In particular, the food contact plastic material comprises an up-conversion-based florescent marker that enables the food contact plastic to be easily identified and separated from a mixture of plastic materials.

BACKGROUND OF THE INVENTION

Plastic materials are widely used in the food packaging industry because of plastic's ability to protect a product from physical damage, loss, and other degradation. Also, plastic material enables the food packaged within to reach the consumer in the same state it was in when packaged at the time of distribution.

With an increase in food delivery and ready-to-go food available in supermarkets, there has been an increase in the amount of food contact plastics found in our rubbish bins. Also, with the enactment of recycling legislation and the use of bottle deposits to discourage litter across the world, the amount of plastic film and bottles available for recycling is increasing rapidly. Ideally, used food contact plastic could be recycled into new bottles or film product thereby saving landfill space, energy and raw materials. Also, since cleanliness of plastic material that is particularly recycled as food contact plastic is a huge consideration, it is much easier to recycle already used food contact plastic materials into beverage containers or other food-contact applications rather than other scrap plastic which will have to undergo a more thorough cleaning process before it can be recycled as food contact plastic. However, before the used food contact plastic material is recycled, the used food contact plastic must be first identified/ detected, and then separated.

Many food contact plastics, such as polyethylene and polyethylene terephthalate (PET), could be recycled as beverage containers or as food contact plastic films easily without undergoing an extensive cleaning process that other scrap plastics, that may have been used in the chemical industry, may have to go through. Accordingly, it is safer and cheaper to recycle food contact plastics than any other plastic. Further, since there is so much food contact plastic being currently produced, recycling the food contact plastic would increase landfill space and is better for the environment, in the event these plastics are incinerated.

Currently however, the problem in the food packaging industry is that the food contact plastic materials cannot be easily separated from the other plastic materials as they can be easily identified or detected in a mountain of mixed plastic materials. Since the used food contact plastic material cannot be identified and/or distinguished from the other plastic materials in a mixture or in a rubbish pile, using a machine or a separator that is usually used for sorting of rubbish, used food contact plastic material cannot be recycled at the moment.

WO 2021/058063A2 discloses a sorting method that could be used on waste that enables recycling and/ or recovery of specific materials from a mixture of different types of materials (for example plastic). In particular, WO 2021/058063A2 discloses a method where the materials to be sorted may have specific properties such as material type, origin or application and these materials may be sorted or detected using a fluorescent code and/or a watermark and/or a barcode and/or a QR code or the like that may be introduced into the material before the sorting process. However, the method in WO 2021/058063A2 makes the process of sorting materials complicated and requires a new type of device for sorting rubbish, particularly plastic rubbish. Further, WO 2021/058063A2 still does not provide a simple and efficient means of detecting food contact plastics in a mixture of different plastics to be recycled. Further, the materials may lose the labels before they reach the sorting process, and these materials cannot then be sorted.

Accordingly, there is still a need in the art for a means of detecting, separating and consequently recycling food contact plastics simply and efficiently.

DESCRIPTION OF THE INVENTION

The present invention attempts to solve the problems above by providing food contact plastic material that comprises a marker. In particular, the marker is an up-conversion-based florescent marker. More in particular, the food contact plastic is manufactured with the marker in the plastic. Food quality plastic material with at least one up-conversion-based fluorescent marker inside is advantageous for the process of recycling of food contact plastic waste into new use food contact plastic. This process of recycling food contact plastic waste or used food contact plastic is only possible because the food contact plastic waste incorporated with the marker within can be distinguished from other plastic waste and therefore results in improved sorting and separation of the used food contact plastic from all other kinds of plastic in automatic waste sorting and separation machines and marker-based sorting machines. The use of up-conversion based florescent marker in the food contact plastic marks the material with clearly distinguishable optical properties. Considering the high-speed industrial sorting machines, the use of up-conversion based fluorescent markers, for marking of food-contact plastic materials, enables the fluorescent markers to create easily recognizable optical signals and to separate the food-contact plastic materials according to its application and not chemical composition.

According to one aspect of the present invention, there is provided a food-contact plastic material used in food packaging, the material comprising at least one up-conversion-based florescent marker.

The term “fluorescent” as used herein in conjunction with up-conversion markers, refers a luminescence phenomenon in which electron de-excitation occurs almost spontaneously, and in which emission from a luminescent substance ceases when the exciting source is removed. In fluorescent materials, the excited state has the same spin as the ground state. A compound capable of fluorescence is termed a “fluor”.

The term “luminescence” as used herein refers to the process in which light is emitted from a material at a different wavelength than that which is absorbed. It is an umbrella term covering both fluorescence and phosphorescence. As used herein, the term “up-conversion” refers to a process where light can be emitted with photon energies higher than those of the light generating the excitation. Photoexcitation at a certain wavelength in the near infrared (NIR) followed by luminescence at a shorter wavelength in the VIS is called NIR to VIS photon up-conversion. This phenomenon may be considered to be rather unusual as low energy photons are “converted” to higher energy photons. At least two NIR photons are required to generate one VIS photon. When fluorescence is emitted by a medium as a consequence of being excited with incident light, the wavelength of the fluorescence is usually longer than that of the exciting light. Photon energy is thus reduced. Up-conversion fluorescence may also occur in some cases where the wavelength of the emitted light is shorter. A more elaborate disclosure of the mechanism behind up-conversion markers is provided in EP2297678 B1. Further, photo-luminescent properties of rare earth compounds are described in US7, 184,203 which may also be used according to any aspect of the present invention.

The concept of frequency up-conversion of infrared-to-visible light in materials fixed with rare-earth (RE) was found to be efficient as a means of labelling or as markers with various functions. Examples of up-conversion markers are sodium yttrium fluoride (NaYF4) doped with lanthanide ions. Suitable lanthanide ions are the rare earths selected from cerium (Ce), erbium (Er), europium (Eu), dysprosium (Dy), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), terbium (Tb), thulium (Tm), and ytterbium (Yb). Particularly, lanthanide ions such as ytterbium (Yb3+), holmium (Ho3+), Erbium (Er3+) or Thulium (Tm3+), orYb3+/Er3+ co-dopants may be used.

Hexagonal sodium yttrium fluoride, NaYF4, may be specifically used for green (Yb3+/Er3+ doped) and blue (Yb3+/Tm3+ doped) up-conversion phosphors. Blue light can also be alternatively generated by Yb,Tm:YLF (yttrium lithium fluoride) when pumped with diode laser light having a wavelength of approximately 958 to approximately 959 nm, green visible light can be efficiently generated by Yb,Er:NYF (sodium yttrium fluoride) when pumped with diode laser light having a wavelength of approximately 976 nm, and red visible light can be efficiently generated by Yb,Er:KYF(potassium yttrium fluoride) or Yb,Er:YF3 when pumped with diode laser light having a wavelength of approximately 973.5 nm to approximately 976 nm. US6,897,999 discloses different up-conversion markers that may be used according to any aspect of the present invention.

In particular, the up-conversion fluorescent marker may be an oxide and/or salt of rare-earth metals. More in particular, the up-conversion fluorescent marker may be selected from the group consisting of yttrium oxide, yttrium ytterbium oxide, yttrium ytterbium oxysulfide, titanium dioxide, cobalt oxide, lanthanum oxide, europium oxide, coordination complexes of rare-earth metals and mixtures thereof. Examples of coordination complexes of rare-earth metals are found at least in Pointel Y et al., Inorganic Chemistry, American Chemical Society, 2020, 59 (15):10673-87 and Jakoby, M., et al., iScience 24(3) art. 102207, March 19, 2021 .

The term ‘food-contact plastic material’ as used herein refers to different types of plastic materials that are used for packaging food that are brought in direct contact with food. Food comes into contact with many different materials and articles during its production, processing, storage, preparation and serving, before its eventual consumption. Such materials maybe called food- contact materials. Food-contact materials are either intended to be brought into contact with food, are already in contact with food, or can reasonably be brought into contact with food or transfer their constituents to the food under normal or foreseeable use. In particular, the food-contact plastic material according to any aspect of the present invention is brought in direct contact with food or was in direct contact with food. Examples of such uses of food-contact plastic material include containers fortransporting food, plastic parts of machinery to process food, plastic packaging materials, plastic kitchenware and tableware. More in particular, food-contact plastic material refers to different types of plastic materials that is brought in direct contact with food. A wide variety of plastics in both rigid and flexible forms may be used as food-contact plastic material. The safety of food-contact plastic material is evaluated by the European Food Safety Authority (EFSA).

Here, the term ‘food’ refers to any matter that is for consumption. Food refers to food products that may include beverages as well as solid and liquid food. Food may also include supplements and medication.

The term ‘food packaging’ as used herein refers to materials that have been used for packaging food for storage and/or fortransport at least.

The phrase ‘the food-contact plastic material comprising at least one up-conversion-based florescent marker’ refers in any aspect of the present invention to a volume-based marking. That is to say, the food-contact plastic does not comprise markers that are used as labels, but the plastic is in itself manufactured with markers. The markers used according to any aspect of the present invention is thus part of the plastic material (i.e. the polymer). The plastic polymer from which the food-contact plastic is made from is thus combined with the up-conversion fluorescent marker during the manufacturing process of the food-contact plastic and/or during the extrusion process of the food-contact plastic. The up-conversion fluorescent marker integrated within the plastic has the advantage that the marker is never lost, and the plastic can almost always be sorted and therefore recycled. The currently available food-contact plastic materials, however, may have labels attached to them instead, if anything at all, and these may fall off before reaching the sorting machine and cannot thus be detected and sorted and therefore cannot be recycled. Further, since the marker is a property of the plastic material in the food-contact plastic material according to any aspect of the present invention, there is a higher chance of the plastic material being almost always sorted even when the sorting is fast. The food-contact plastic according to any aspect of the present invention may also have the advantage that it can be used for any flexible food packaging such as fumes that can also be distinguished, sorted and recycled.

In particular, the up-conversion fluorescent markers according to any aspect of the present invention can be added to the plastics directly or via masterbatch route. However, due to low marker concentration in the plastics (ppm-range) the masterbatch route is clearly preferrable. The up-conversion fluorescent marker concentration in masterbatch can be in range 100 ppm - 500 ppm. More in particular, the up-conversion fluorescent marker concentration may be about 50- 1000, 50-950, 50-900, 50-850, 50-800, 50-750, 50-700, 50-650, 50-600, 50-550, 50-500, 100- 1000, 100-950, 100-900, 100-850, 100-800, 100-750, 100-700, 100-650, 100-600, 100-550, 100- 500, 150-1000, 150-950, 150-900, 150-850, 150-800, 150-750, 150-700, 150-650, 150-600, 150- 550, 150-500, 200-1000, 200-950, 200-900, 200-850, 200-800, 200-750, 200-700, 200-650, 200- 600, 200-550, 200-500, 250-1000, 250-950, 250-900, 250-850, 250-800, 250-750, 250-700, 250- 650, 250-600, 250-550, 250-500, 300-1000, 300-950, 300-900, 300-850, 300-800, 300-750, 300-

700, 300-650, 300-600, 300-550, 300-500, 350-1000, 350-950, 350-900, 350-850, 350-800, 350-

750, 350-700, 350-650, 350-600, 350-550, 350-500, 400-1000, 400-950, 400-900, 400-850, 400-

800, 400-750, 400-700, 400-650, 400-600, 400-550, 400-500 ppm. Even more in particular, the up- conversion fluorescent marker concentration may be about 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, or 1000 ppm in the masterbatch.

In one example, the masterbatch with 500 ppm of up-conversion fluorescent marker material can be manufactured through mixing of 50 kg of the granulated plastic material with 10 g of up- conversion fluorescent marker material and 20 ml of dispersion additive in a tumble mixer. This masterbatch can then be diluted through addition of non-marked plastics granulate in extruder.

The final concentration of up-conversion fluorescent marker in plastics may be in the range 1 ppm - 200 ppm. In particular, the final concentration of up-conversion fluorescent marker in the foodcontact plastic according to any aspect of the present invention may be 1-200, 1-150, 1-100, 1-50, 1-45, 1-40, 1-35, 1-30, 1-25, 1-20, 1-15, 1-10, 1-5, 5-200, 5-150, 5-100, 5-50, 5-45, 5-40, 5-35, 5- 30, 5-25, 5-20, 5-15, 5-10, 10-200, 10-150, 10-100, 10-50, 10-45, 10-40, 10-35, 10-30, 10-25, IQ- 20, 10-15, 15-200, 15-150, 15-100, 15-50, 15-45, 15-40, 15-35, 15-30, 15-25, 15-20, 20-200, 20- 150, 20-100, 20-50, 25-200, 25-150, 25-100, 25-50, 30-200, 30-150, 30-100, 30-50, 40-200, 40- 150, 40-100, 50-200, 50-150, 50-100, 100-200, 100-150 ppm. More in particular, the final concentration of up-conversion fluorescent marker in the food-contact plastic according to any aspect of the present invention may be about 1 , 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 125, 150, 175, or 200 ppm. Even more in particular, the final concentration of up-conversion fluorescent marker in the food-contact plastic according to any aspect of the present invention may be about 10 ppm.

The homogenization of the plastics-marker mixture (i.e. food contact plastic material with the up- conversion fluorescent marker) can be carried out in standard drum mixer. The improvement of the homogeneity of the marker distribution on the masterbatch can be achieved by use of dispersion additives, for example TEGOMER®, TEGOPREN®, TEGODISPERS®, Epolene®.

As used herein, the terms "about" and "approximately", as applied to the up-conversion fluorescent marker) marker concentration refer to a range of values that are similar to the stated reference value forthat condition. In certain examples, the term "about" refers to a range of values that fall within 25, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 , 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 percent or less of the stated reference value forthat condition. For example, a temperature employed during the method according to any aspect of the present invention when modified by “about” includes the variation and degree of care typically employed in measuring in an experimental condition in production plant or lab. For example, the temperature when modified by “about” includes the variation between batches in multiple experiments in the plant or lab and the variation inherent in the analytical method. Whether or not modified by “about,” the amounts include equivalents to those amounts. Any value stated herein and modified by “about” can also be employed in the present invention as the amount not modified by “about.”

In particular, the food-contact plastic material may be selected from the group consisting of High- Density Polyethylene (HDPE), Low-Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), Polyvinylchloride (PVC), Polypropylene (PP), Polystyrene (PS), polyamide (PA), polyethylene-terephthalate (PET), Polyethylene terephthalate glycol (PETG) polymethylmethacrylate (PMMA), polycarbonate (PC), expanded polystyrene (EPS), expanded polypropylene (EPP), polyurethanes (PU), glass-fiber reinforced PP, epoxy-based composites, mixtures, multilayer-systems of above-mentioned materials and mixtures thereof. More in particular, the food-contact plastic material is selected from the group consisting of multilayer PE/PA, multilayer PET/ PETG, PET, and multilayer LDPE / LLDPE / HDPE. The food-contact plastic material may also include flexible packages made from films or thin sheets of polyolefins or plasticized PVC.

The up-conversion based fluorescent marker according to any aspect of the present invention may be combined with a further marker. Again, the further marker will be added to the food contact plastic material during the manufacture or extrusion process that the further marker becomes part of the material and is not just a label. In another example, the further marker is only a label and is used in combination with the up-conversion based fluorescent marker that is integrated into the food-contact plastic.

In particular, the further marker may be a pigment, liquid crystal, ultraviolet/visible (UV/VIS) marker, a near infrared (NIR) marker, a phosphorescent (Phos) marker, and/or a magnetic marker. It is advantageous to use the up-conversion marker in combination with a further marker as firstly, none of these markers can be detected when irradiated by light of the visible spectrum. Therefore, the marking of the food-contact plastic cannot be detected unless scanned for by using dedicated detection equipment. It also advantageous to use both the markers as there may be a limitless combination of unique detection codes available for the different food contact plastics enabling the different materials to be detected and therefore separated from one another.

Further, the use of optical markers (i.e. pigments, liquid crystals and fluorescent markers) as the further marker according to any aspect of the present invention, has an advantage of emission of well-defined light emission spectrum in dependency of the incident light. This spectrum is characteristic for fluorescent material.

In particular, the further marker may be the magnetic marker. More in particular, the magnetic marker may be selected from the group consisting of iron oxide, cobalt oxide, cobalt doped iron oxide, nickel doped iron oxide, chromium doped iron oxide, chromium oxide, and platinum doped iron oxide.

The food-contact material may further comprise an infra-red adsorbing marker. In one example, the food-contact material comprises an up-conversion marker, a magnetic marker and an infra-red adsorbing marker. In the example, all three types of markers may be integrated into the foodcontact plastic. In another example, only the up-conversion marker is integrated into the food- contact plastic material and the other two markers are only present as labels. In yet another example, the up-conversion marker and either the magnetic marker or the infra-red adsorbing marker is integrated into the plastic material and the other marker is only present as a label.

The inclusion of infra-red absorbing markers allows for the separation of food-contact plastic waste into groups according to its application and according to its chemical composition, creating, in this way, waste streams for high- value recyclates.

The term “infrared” as used herein encompasses the range of light spectrum above approximately 650 nm and includes both the far infrared and the near infrared. The term “near-infrared”, as used herein, refers to the wavelength region between about 650 nm and 2000 nm, and particularly between about 750-1100 nm, while the term “far infrared” refers to wavelengths between 1- and 10-mm. Examples of these makers are provided in EP2297678.

The food-contact plastic material according to any aspect of the present invention further comprising food or food remains.

According to a further aspect of the present invention, there is provided a method of separating food-contact plastic material from a mixture of non-food contact plastic material and food-contact plastic material, the method comprising: contacting the mixture to at least one high-speed industrial sorting machine, wherein the food-contact plastic material comprises at least one up-conversion based florescent marker.

The mixture of non-food contact plastic material and food-contact plastic material refers to an assortment of different plastic materials from different applications that are combined and are found in rubbish, particularly plastic waste. The food-contact plastic material may be the plastic material according to any aspect of the present invention.

The high-speed industrial sorting machine may be capable of infra-red adsorbing marker-based sorting. The combination with near infra-red analytics marker-based sorting will allow the separation of plastics waste into groups according to its application and according to its chemical composition, creating, in this way, waste streams for high- value recyclates. Examples of infra-red analytics marker-based sorting include a standard infra-red sorting machine additionally equipped with marker-specific sensors, or with updated detection software, which includes marker emission spectrum in detection algorithm.

According to a further aspect of the present invention, there is provided a use of an up-conversion based florescent marker for separating food-contact-plastic material from non-food contact plastic material, wherein the food-contact-plastic material comprises the up-conversion based florescent marker. The up-conversion-based marker may be combined with a pigment, liquid crystal, or a magnetic marker.

EXAMPLES The foregoing describes preferred embodiments, which, as will be understood by those skilled in the art, may be subject to variations or modifications in design, construction or operation without departing from the scope of the claims. These variations, for instance, are intended to be covered by the scope of the claims. Example 1 (prophetic)

A PE/PA/PE multilayer food packaging film is manufactured by well-known coextrusion method of PE and PA films, where the PA film is located between two PE layers. The up-conversion fluorescent marker used may be Er-doped YYbO2S, Er-doped GdYbO2S, Er/Yb/Nd-doped La2Os, Yb/Ho-doped La2Os is incorporated into the PA-layer. This is called the ‘marked film’ The same multilayer packaging film is manufactured without a marker as reference. This control is called ‘non-marked film’.

50 cm ² big elements of marked and non-marked films are put on a transportation band with PE- packaging and pure PE-film elements and transported through a Near-Infrared (NIR)-detection unit equipped with marker-specific sensing equipment. The NIR-detection unit can clearly distinguish PE-packaging, PE-film and marked PE/PA multilayer film from each other. The PE/PA multilayer film without marker cannot be identified and fails through the sorting procedure (i.e. is not detected and therefore not sorted).