WO2022250535A1

WO2022250535A1 - Recyclable racket sports ball and method of recycling a mixed waste stream comprising said ball

Info

Publication number: WO2022250535A1
Application number: PCT/NL2022/050287
Authority: WO
Inventors: Eric Petersen
Original assignee: Renewaball B.V.
Priority date: 2021-05-26
Filing date: 2022-05-25
Publication date: 2022-12-01
Also published as: NL2028298B1

Abstract

This disclosure describes a recyclable product (1), in particular in the form of a racket sports ball, comprising a renewable polymeric composition and a marker substance distributed over the product, wherein the distribution (2) of the marker substance is configured to provide exterior access to the marker substance in any angular orientation of the product (1) to thereby allow selection of the recyclable product (1) from a mixed waste stream. Such a product (1) enables a method of recycling a mixed waste stream comprising said recyclable product (1) by means of (S1) detecting the marker substance of the recyclable product (1) to identify the recyclable product (1) within the mixed waste stream, (S2) separating the recyclable product (1) from the mixed waste stream and (S3) obtaining the renewable polymeric composition from the separated recyclable product (1).

Description

RECYCLABLE RACKET SPORTS BALL AND METHOD OF RECYCLING A MIXED WASTE STREAM COMPRISING SAID BALL

[1] The present invention relates to recyclable products and methods of recycling, in particular applied to sports or playing objects comprising a renewable polymeric composition. Such sports and playing objects are widely used in many countries around the world.

[2] In order to reduce waste, costs of production and environmental impact, products are often recycled, repurposed or reused. However, for a range of products, this has so far not been possible.

[3] In particular where products have a standardised outward appearance yet variable inner compositions, recycling is impeded and often impossible. At best, this leads to down-cycling of potentially valuable materials of the product, though incineration or land-fill is more common. Examples of such products are sports or playing objects, such as racket sports balls. In the case of tennis balls, more than 300 million items are produced and disposed of annually around the world.

[4] Accordingly, there is a demand for a method of recycling racket sports balls. There is furthermore a demand for recycling racket sports balls having similar densities but different composition. There is also a demand for simplification of the recycling of racket sports balls.

[5] It is an objective of the present invention to overcome or at least reduce the above disadvantages.

[6] This is achieved through the invention by providing a recyclable product in the form of a racket sports ball comprising:

- a solid or hollow core of a renewable polymeric composition; and

- a marker substance distributed over the product,

- wherein the distribution of the marker substance is configured to provide exterior access to the marker substance in any angular orientation of the product to thereby allow selection of the recyclable product from a mixed waste stream

[7] The marker substance in its distribution over the product allows selection of the product, preferably in an automated fashion, from a mixed waste stream irrespective of the orientation of the product in such waste stream. This improves speed and accuracy of the selection of the products comprising the renewable polymeric composition so that products comprising the renewable polymeric composition may be separately collected and reused as a raw material, thereby renewing the polymeric composition into new products, preferably the same products. [8] Polymeric compositions in general degrade over time, for example by exposure to solvents, ultraviolet light, temperature/pressure cycles and / or mechanical forces, eventually leading to disposal of products comprising potentially renewable polymeric compositions. In particular when polymeric compositions are employed in products such as sports balls which require a particular bounce, degrading of properties of polymeric compositions directly impacts the usability of the products. In addition to racket sports balls such as tennis balls, padel balls and squash balls, other relevant products may include playing objects or toys such as stress balls, bouncy balls and soft toys.

[9] The marker substance is observable or accessible from the exterior of the product and thus marks the product as comprising the renewable polymeric composition, though this renewable polymeric composition may itself not be observable or accessible from the exterior of the product. Further, the marker substance may be associated to a group of renewable polymeric compositions that are jointly renewable. The marker substance can be employed favourably to identify a specific renewable polymeric composition present in the product, thus enabling selection of products bearing the marker substance to increase purity of a recycling stream comprising various products with various polymeric compositions. Via the marker substance, products comprising the selected renewable polymeric composition can be combined to form a waste stream of increased purity.

[10] In the context of the present invention, ‘renewable’ relates to reuse of the polymeric composition for the production of the same or a similar product. The renewed product may thus comprise the same material and be of the same quality as the recycled product that was used as the source of the material. The renewable polymeric composition may comprise fresh material (also termed new or virgin material) and / or previously recycled material. For example, the renewable polymeric composition may comprise only fresh material before its first reuse.

[11] The marker substance may be invisible to the human eye or may at least be invisibly distributed over the product. In other words, though the marker on its own, i.e. in a pure form and of sufficient quantity, may in fact be visible to the human eye, the distribution of the marker is preferably invisible to the human eye. The outer appearance of the product may therefore not be distinguishable by the human eye from similar products which do not comprise the marker.

[12] The marker substance may be detectable upon excitation by electromagnetic radiation. To this end, the marker substance preferably comprises a photoluminescent compound, more preferably an infrared luminescent compound. [13] The marker substance may comprise at least one metal ion, preferably at least one rare- earth metal ion, more preferably at least one ion of europium, yttrium, ytterbium, lutetium and / or tantalum.

[14] Alternative or additionally, the marker substance may comprise at least one metal oxide, preferably at least one transition metal oxide and / or at least one lanthanide oxide, more preferably on or more metal oxides out of the group of europium oxide, yttrium oxide, ytterbium oxide, lutetium tantalate, even more preferably yttrium oxide and / or ytterbium oxide. Metal oxides are generally known and may comprise metal ions in various oxidation states combined with one or more oxygen atom. Metal oxides provide improved stability of the marker substance.

[15] The marker substance may be distributed in the form of particles, preferably microparticles and / or nanoparticles, more preferably with a median particle size in the range of 0.05 - 1.10² pm. Such particles are not or hardly discernible by the human eye. Moreover, these allow dispersion or mixing with carrying materials, such as the renewable polymeric composition, glues or outer layers.

[16] The renewable polymeric composition may comprise a natural or synthetic rubber compound, preferably at least one of natural rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, butyl rubber, EPDM rubber, more preferably natural rubber and butadiene rubber.

[17] The renewable polymeric composition may comprise sulphur crosslinks, preferably obtained by vulcanisation.

[18] The recyclable product may further comprise an outer layer arranged around the renewable polymeric composition, in particular around the solid or hollow core of the racket sports ball. In this case, the marker substance is preferably disposed in or on the outer layer. Alternatively or additionally, the outer layer may comprise cover sections defining connection lines between the cover sections. The marker substance may then be arranged in the cover sections and / or the connection lines, preferably in the connection lines. Any such outer layer is distinct from the renewable polymeric composition that can form the hollow or solid core of the product.

[19] The recyclable product may form a sports or playing object, preferably a sports ball, more preferably a racket sports ball, even more preferably a tennis ball.

[20] Further, the invention provides a method of recycling a mixed waste stream comprising a recyclable product according to the invention. The recycling method comprises the steps of detecting the marker substance of the recyclable product to identify the recyclable product within the mixed waste stream, separating the recyclable product from the mixed waste stream and obtaining the renewable polymeric composition from the separated recyclable product.

[21] The step of detecting the marker substance of the recyclable product may comprise at least one of exciting the marker substance with electromagnetic radiation, collecting electromagnetic radiation emitted by the marker substance and detecting photoluminescence of the marker substance, preferably infrared photoluminescence. Detecting can be done using a camera sensitive to the emitted radiation, such as a charge-coupled device.

[22] The step of obtaining the renewable polymeric composition from the separated recyclable product comprises at least one of removing an outer layer of the recyclable product, granulating the obtained renewable polymeric composition and de-crosslinking the renewable polymeric composition for renewed use.

[23] Preferably, the method further comprises a step of forming the obtained renewable polymeric composition into recyclable products or components thereof.

[24] Finally, the invention relates to use of a marker substance, preferably the marker substance of the recyclable product according to the invention, in a sports or playing object for identification of this object in a mixed waste stream. Preferably, the sports or playing object forms a sports ball, more preferably a racket sports ball, most preferably a tennis ball. In any of these products, the marker substance can advantageously be used in a seam of the product, object or ball, which enables detection of the marker substance from various angular orientations of the ball. Tennis balls in particular deteriorate fast, for example through loss of pressure and / or elasticity.

[25] The invention is further clarified through the following figures, wherein:

FIG. 1 schematically depicts a recyclable product, embodied as a squash ball, according to the invention in a cutaway view;

FIG. 2 schematically depicts a recyclable product, embodied as a tennis ball, according to the invention in a cutaway view; and

FIG. 3 is a flow diagram of a preferred embodiment of the method according to the invention.

[26] The following reference signs are used:

1 recyclable product

2 distribution of marker substance

3 core

4 outer layer

5 cover section 6 connection line

51 detecting marker substance of recyclable product

51.1 exciting marker substance with electromagnetic radiation

51.2 collecting electromagnetic radiation emitted by marker substance

52 separating recyclable product from mixed waste stream

53 obtaining renewable polymeric composition from recyclable product

53.1 removing outer layer of recyclable product

53.2 granulating renewable polymeric composition

53.3 de-crosslinking renewable polymeric composition

54 forming renewable polymeric composition

[27] In the following detailed description of the figures, examples of racket sports balls are presented to illustrate the invention in a coherent manner. However, the invention should not be understood to be limited to this particular application, as the limits of the present invention are defined by the appended claims. Various other examples are presented throughout this disclosure.

[28] FIG. 1 shows a cutaway drawing of a recyclable product 1 according to the invention, here embodied as a squash ball 1. The squash ball 1 comprises a renewable polymeric composition and a marker substance distributed over the ball 1. The distribution 2 of the marker substance is configured to provide exterior access to the marker substance in any angular orientation of the product 1 to thereby allow selection of the recyclable product 1 from a mixed waste stream.

[29] The squash ball 1 comprises the renewable polymeric composition in the form of a core 3. For a squash ball 1, the core 3 is hollow, though it may also be solid in other product types, for example a golf ball or playing toy, like a squishy or a stress ball. The marker substance is preferably distributed over the core 3 in a distribution 2 that is invisible to the human eye. For example, the marker substance may be distributed throughout the renewable polymeric composition, for example by mixing the marker substance with the renewable polymeric composition in the production process of the squash ball 1, or the marker substance may be distributed over the exterior surface of the product 1, here the core 3 of the squash ball 1, that is accessible in any angular orientation of the product. This enables more efficient recycling, since positioning of the recyclable product 1 in order to select it from a mixed waste stream is no longer required, which is otherwise particularly difficult with balls and other rounded products.

[30] Such distributions 2 can include randomly arranged dots and / or circumferential lines, preferably extending into the bulk of the core 2 for reducing effects of wear. In the example of FIG. 1, the markers substance is illustrated as randomly distributed throughout the core 2 of the squash ball 1. The concentration may be chosen such that the marker substance is always accessible via the exterior of the squash ball 1 irrespective of exterior wear of this squash ball 1. In addition to the squash ball 1, these arrangements may be employed with any hollow or solid product 1 in which the renewable polymeric composition carries the marker substance in the distribution 2 that is accessible from the exterior of the product 1, such as a bouncy ball or other hollow or solid polymeric toy.

[31] FIG. 2 shows cutaway drawing of a recyclable product 1 according to the invention, here embodied as a tennis ball 1. Alternatively, the illustrated and described recyclable product 1 may also represent a padel ball. In any case, this tennis or padel ball 1 comprises a renewable polymeric composition and a marker substance distributed over the ball 1. The distribution 2 of the marker substance is configured to provide exterior access to the marker substance in any angular orientation of the ball 1 to thereby allow selection of the ball 1 from a mixed waste stream.

[32] The tennis ball 1 comprises the renewable polymeric composition in the form of a hollow core 3, for example of rubber or rubber-like material. Further, the tennis ball 1 comprises an outer layer 4, for example of felt material, arranged around the core 3 formed by the renewable polymeric composition. Glue is commonly used to mount the outer layer 4 onto the core 3.

[33] The outer layer 4 may comprise cover sections 5 which can be mutually separated, thereby defining one or more than one connection line 6. The illustrated tennis ball 1 has two cover sections 5 and one connection line 6 running in a closed loop between the two cover sections 5.

The connection line 6 is generally filled with glue to connect the cover sections 5 of the outer layer 4 and is sometimes known as the seam. This glue may comprise a vulcanising solution.

[34] Advantageously, the marker substance can be distributed over the tennis ball 1 by arranging the marker substance in or on the outer layer 4 of the tennis ball 1 to provide exterior access. In this way, the renewable polymeric composition is left free from marker substance. Alternatively or additionally, the marker substance may be provided between the outer layer 4 and the core 3 of the ball 1, for example in or on the glue layer in between.

[35] For example, the marker substance may be arranged in at least one cover section 5 of the product 1. In case of a tennis or padel ball 1 covered with felt material, the marker substance may be comprised in at least one felt cover section 5 of the ball 1, for example by providing the marker substance into or onto fibres used to produce this felt material by means of a dying process, blending in fibres composed of the marker substance or otherwise. [36] It is further considered to provide the tennis or padel ball 1 with cover sections 5 made out of biodegradable materials, such as wool and / or cotton. This avoids synthetic fibres, such as nylon and polyester, that are presently commonly used, but which result in micro-plastics pollution when used in games of tennis, padel or otherwise. Biodegradable fibres may thus reduce environmental impact and player safety.

[37] As an alternative example or in addition to arranging the marker substance in at least one cover section of the outer layer 4, the marker substance may be arranged in at least one connection line 6 of the outer layer 4 of the product 1. As illustrated in FIG. 2, the marker substance may be arranged in the connection line 6 of the tennis or padel ball 1 to provide exterior access to the marker substance in any angular orientation of the ball 1. Since balls in particular are difficult to orientate in a mixed waste stream, providing the marker substance in this way facilitates efficient recycling.

[38] The marker substance may be disposed in the connection line 6 of the tennis ball 1 by mixing the marker substance with the glue that is normally used for the seam in producing tennis balls. This mixture may then be provided to the sides of the cover sections 5 to define the connection line 6 which provides the exterior access to the marker substance in any angular orientation of the ball 1.

[39] In any implementation of the invention, the following materials and properties are contemplated for the marker substance and the renewable polymeric composition.

[40] The marker substance may be configured to be detectable upon excitation by electromagnetic radiation. Preferably, the marker substance comprises a photoluminescent compound. More preferably, the marker substance comprises an infrared luminescent compound. In this context, ‘infrared luminescent’ means that the emitted light is in the infrared range of the electromagnetic spectrum. Though associated excitation may preferably also occur in the infrared, it may also occur in other regions of the electromagnetic spectrum, such as the visible or ultraviolet.

[41] Both the excitation range and the emission range of the infrared luminescent compound may he in the range of 0.7 - 1.4 pm, preferably 0.8 - 1.1 pm. It is further preferred that the excitation range is of shorter wavelength, i.e. of higher energy, than the emission range, though these may partly overlap. A maximum of the emission spectrum may lie in the range of 850 - 900 nm. Particularly advantageous is an excitation range of 800 - 1050 nm, more preferably 820 - 980 nm, combined with an emission range of 850 - 1100 nm, more preferably 890 - 1040 nm. These ranges improve distinctiveness of the recyclable product within a mixed waste stream. [42] As alternative to infrared luminescent compounds, it is also contemplated to employ ultraviolet luminescent compounds which emit light in the ultraviolet range of the electromagnetic spectrum.

[43] Both organic as well as inorganic photolumine scent compounds are possible. However, inorganic materials are preferred for their stability.

[44] In particular, the marker substance may comprise at least one metal ion, preferably at least one rare-earth metal ion, more preferably at least one ion of europium, yttrium, ytterbium, lutetium and tantalum.

[45] The term ‘rare-earth metals’ may be defined as the group of the following elements: scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

[46] Trivalent lanthanide ions, including Eu³⁺, Tb³⁺, Nd³⁺, Er' and Yb³⁺, may provide good photoluminescent properties to improve spectral distinctiveness of the product 1 in a mixed waste stream. Lanthanide-doped phosphors may also be employed as the marker substance.

[47] In addition or alternatively to the above materials, the marker substance may comprise at least one metal oxide, preferably at least one transition metal oxide and / or at least one lanthanide oxide, more preferably on or more metal oxides out of the group of europium oxide, yttrium oxide, ytterbium oxide, lutetium tantalate, even more preferably yttrium oxide and / or ytterbium oxide.

[48] The term ‘transition metals’ may be defined as elements of groups 3-12 of the periodic table, also termed the d-block.

[49] The term ‘lanthanides’ may be defined as the group of the following elements: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

[50] The marker substance may be distributed in the form of particles or in the form of a powder. Preferably, the marker substance is provided as microparticles and / or nanoparticles, more preferably with a median particle size in the range of 0.05 - 1 x 10² pm. In this context, ‘microparticles’ may be defined as particles with dimensions in the range of 1 - 1 x 10³ pm while ‘nanoparticles’ may be defined as particles with dimensions in the range of 1 - 1 x 10³ nm.

[51] The marker substance may be distributed in the form of particles with a D50 value in the range 0.05 - 5 pm, preferably 0.5 - 3 pm, more preferably of 2 ± 1 pm. Particle size can be determined by laser diffraction or by other known test methods. The D50 value is the median particle size as determined by the chosen test method.

[52] In tests, a particularly favourable particle size distribution was found to have a D50 value of 2 pm and a D95 value of 6 pm, as measured by laser diffraction. D50 indicates the median particle size, while D95 indicates that 95% of the measured particles were determined to be below this dimension. This particle size distribution provides favourable detection via the exterior of the product 1.

[53] The concentration of the marker substance may be in the range of 10 - 600 ppm, preferably 100 - 200 ppm, more preferably 120 - 180 ppm. These ranges provide favourable detectability when the marker substance is mixed with carrier material, such as renewable polymeric composition of the core 3 or glue of the connection line 6.

[54] In particular when mixing the marker substance with glue for the connection line 6 of the tennis ball 1, an advantageous combination was found to be in the range of 6 - 12 g of marker substance for 40 - 80 kg glue as generally used in the art for this purpose.

[55] The renewable polymeric composition may comprise a natural or synthetic rubber compound, preferably at least one of natural rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, butyl rubber, EPDM rubber, more preferably natural rubber and butadiene rubber.

[56] Butadiene rubber may be produced by polymerisation of 1,3 -butadiene. Styrene-butadiene rubber may be produced by copolymerisation of styrene and butadiene. Isoprene rubber may be produced by polymerisation of isoprene resulting in cis-l,4-polyisoprene dominant polyisoprene. Butyl rubber may be produced by copolymerisation of isobutylene and isoprene. It may be in the form of halogenated butyl rubber, also termed halobutyl rubber, such as chlorobutyl or bromobutyl. EPDM rubber (in full: ethylene propylene diene monomer rubber) may be produced by polymerisation of ethylene and propylene with diene co-monomers for crosslinking.

[57] The polymeric composition may further comprise additives, fillers, curing agents, colorants, and / or sulphur or other crosslinking agents.

[58] Preferably, the renewable polymeric composition comprises sulphur crosslinks. Such sulphur crosslink may have previously been obtained by vulcanisation of the polymeric composition, for example to form the core 3 of the product 1. Sulphur crosslinks are beneficial because these allow de-crosslinking of the renewable polymeric composition by de vulcanisation. This is further described below in relation to the recycling method. Alternatively, the renewable polymeric composition may be crosslinked with peroxides. Using crosslinking peroxides rather than sulphur improves stability of the renewable polymeric composition before it is crosslinked.

[59] FIG. 3 shows a flow diagram of a preferred embodiment of the method according to the invention, including a number of optional steps.

[60] The method of recycling a mixed waste stream comprising the recyclable product 1 according to the invention is now described in more detail. The method comprises a step SI of detecting the marker substance of the recyclable product to identify the recyclable product within the mixed waste stream, a step S2 of separating the recyclable product from the mixed waste stream and a step S3 of obtaining the renewable polymeric composition from the separated recyclable product.

[61] The step SI of detecting the marker substance of the recyclable product 1 may comprise detecting photoluminescence of the marker substance, preferably infrared photoluminescence. Alternatively or additionally, the step S 1 may comprise a step S 1.1 of exciting the marker substance with electromagnetic radiation and / or a step SI.2 of collecting electromagnetic radiation emitted by the marker substance. Performing both excitation S 1.1 and collecting emission SI.2 provides increased selectivity to the recyclable product 1 comprising the marker substance, especially when the marker substance comprises a rare-earth metal ion generally not occurring in (roughly sorted) waste streams.

[62] The step S 1 may be implemented by a camera and / or an illuminator, each optionally equipped with filters to select a range of the electromagnetic spectrum associated with the marker substance.

[63] The step SI results in identification of the recyclable product 1 within the mixed waste stream. This identification may be based on cumulative requirements. As a first requirement, the detection of autonomous or induced photoluminescence of the marker substance may be employed, for example as described above.

[64] As a second requirement, image recognition may be employed, for example by recognition of a shape of the recyclable product 1 or exterior markings thereon. Image recognition may be based on a visual image of the mixed waste stream. Such visual image may be collected separately from the detection of the marker substance which may be invisible and / or photoluminescent. Alternatively, image recognition may be performed on an image of the detected signal arising from the marker substance, e.g. its photoluminescence, to determine whether the detected distribution of the marker substance in the image matches the distribution 2 expected for the marker substance in the recyclable product 1.

[65] As a third requirement, spectral features of the exterior of the recyclable product 1 may be employed, for example to recognise a material of the outer layer 4 of the recyclable product 1. Detected spectral features may be compared to a database to determine whether or not a particular article in the waste stream meets this third requirement. Preferably, these spectral features are in the near infrared range. For example, fingerprint regions in infrared spectra, X-ray fluorescence or ultraviolet-visible spectroscopy can be employed to discriminate the recyclable product 1 or a part thereof from other items within the mixed waste stream.

[66] For example, when the mixed waste stream is formed by tennis balls over various makes, it is possible to separate those tennis balls having nylon and / or polyester in their cover sections 5 from those balls who have not on the basis of the third requirement. Further, tennis balls 1 of the invention can be identified in the waste stream on the basis of the first requirement with the second requirement being used as a control. Other implementations are conceivable, such as using the three requirements cumulatively before an article in the waste stream is identified as the recyclable product 1.

[67] The step S2 of separating the recyclable product from the mixed waste stream may be implemented by directing pulses of compressed air, controlling an array of levers, controlling moveable grabbers or any further methods known in the art.

[68] It has been found particularly favourable to adapt existing sorting machines for the purpose of executing at least the step S2 of the method, for example to detect and separate tennis balls 1 bearing the marker substance from a mixed waste stream of racket sports balls. Existing sorting machines may be adapted with light sources (such as infrared light-emitting diodes) and / or cameras appropriate for the detection of the marker substance as disclosed herein. Machines suitable for such adaption are described in WO 2007102732 A1 and EP 3689126 A

[69] The step S3 of obtaining the renewable polymeric composition from the separated recyclable product may comprises a step S3.1 of removing an outer layer 4 of the recyclable product 1 and / or a step S3.2 of granulating the obtained renewable polymeric composition and / or a step S3.3 of de-crosslinking the renewable polymeric composition for renewed use.

[70] The step S3.1 of removing the outer layer 4 of the recyclable product 1 may comprise a dry separation technique, for example by means of the machine described in EP 3 567 157 Al. A bath of recyclable products 1, preferably in the form of a tennis or padel balls 1, is introduced into this machine and broken into course pieces while these pieces are agitated and sieved to obtain the outer layer material separated from the core material, i.e. the renewable polymeric composition. As a further example, a shredder and cyclone device may be employed to separate the outer layer 4 from the core 3 of the recyclable product 1. However, this results in finer pieces of material compared to the previous example.

[71] The step S3.2 of granulating the obtained renewable polymeric composition may be performed as part of the step S3.1. It may also be performed additionally to or instead of the step S3.1.

[72] The step S3.3 of de-crosslinking the renewable polymeric composition may comprise devulcanisation of the renewable polymeric composition, preferably after it has been granulated in the step S3.2. The step S3.3 enables a reduction in the amount of fresh material required in renewing the polymeric composition with similar properties as the original renewable polymeric composition. For example, when producing a core for a tennis ball from recycled tennis ball cores having the same polymeric composition, test results indicate that about half of the polymeric composition can be of recycled origin and the remainder freshly produced while still meeting specifications of the International Tennis Federation.

[73] Preferably, the recycling method further comprises a step S4 of forming the obtained renewable polymeric composition into recyclable products 1 or components thereof. Especially when the step S3.3 of de-crosslinking is performed prior to the step S4, the renewable polymeric composition obtained from the recyclable product 1 can be mixed with fresh renewable polymeric composition for the newly produced products or components without further treatment.

[74] Though the invention is more widely applicable, the present invention is particularly relevant for racket sports balls (e.g. tennis balls, padel balls, squash balls). These balls generally degrade over time and by use, for example losing their original bounce, thus becoming unsuitable for their intended use. Renewing them to again meet technical specification would extend their useful life, but is only now made possible through the present invention. Previously, many sports balls could not be renewed but could only disposed off as waste. In some cases, recycling of sports balls has been implemented, though this does not lead to new sports balls but to lower grade products such as flooring.

[75] Nevertheless, the features described in relation with the step S3 of obtaining the renewable polymeric composition from the separated recyclable product, provide various improvements to presently available recycling methods. This is in particular the case for tennis or padel balls, where the step S3 may result in separated fractions of felt material sourced from the outer layer and material sourced from the rubber core, i.e. the renewable polymeric composition.

[76] Moreover, tennis or padel balls may vary greatly in the composition of their core. A mixed waste stream of tennis balls of various makes may therefore not be suitable for reuse as a source of the renewable polymeric composition to produce further tennis balls, unless the invention is applied to enable separating specific tennis balls having the renewable polymeric composition. If all or cores from such a mixed tennis ball waste stream were combined, only a low-grade polymeric material would be obtained that would only be useable for down-cycling and not be useable for new tennis balls. The invention enables obtaining a renewable polymeric composition fraction from the mixed waste stream of increased purity by separating those balls having the specific renewable polymeric composition from the mixed waste stream via their marker substance.

[77] Though the invention is here described with a focus on racket sports balls, in particular squash and tennis balls, the technology presented here may be applied to various recyclable products comprising a renewable polymeric composition. Examples include various sports, play or leisure articles, so that recycling of such articles in separated waste streams may be efficiently implemented.

Claims

1 A recyclable racket sports ball (1) comprising:

- a solid or hollow core (3) of a renewable polymeric composition; and

- a marker substance at least invisibly distributed over the recyclable racket sports ball (1) to the human eye,

- wherein the distribution (2) of the marker substance is configured to provide exterior access to the marker substance in any angular orientation of the recyclable racket sports ball (1) to thereby allow selection of the recyclable racket sports ball (1) from a mixed waste stream.

2 Recyclable racket sports ball (1) of claim 1, wherein the marker substance is detectable upon excitation by electromagnetic radiation, wherein the marker substance preferably comprises a photoluminescent compound, more preferably an infrared luminescent compound.

3 Recyclable racket sports ball (1) of claim 1 or 2, further comprising an outer layer (4) arranged around the solid or hollow core (3).

4 Recyclable racket sports ball (1) of claim 3, wherein the marker substance is disposed in or on the outer layer (4).

5 Recyclable racket sports ball (1) of claim 3 or 4, wherein the outer layer (4) comprises cover sections (5) defining connection lines (6) between the cover sections (5).

6 Recyclable racket sports ball (1) of claim 5, wherein the marker substance is arranged in the cover sections (5). 7 Recyclable racket sports ball (1) of claim 5 or 6, wherein the marker substance is arranged in the connection lines (6).

8 Recyclable racket sports ball (1) of any previous claim forming a tennis ball or a padel ball.

9 Recyclable racket sports ball (1) of claim 8, wherein the marker substance is distributed in the seam of the tennis ball or the padel ball.

10 Recyclable racket sports ball (1) of any previous claim, wherein the marker substance comprises at least one metal ion, preferably at least one rare-earth metal ion, more preferably at least one ion of europium, yttrium, ytterbium, lutetium, tantalum, even more preferably an yttrium and / or ytterbium ion. 11 Recyclable racket sports ball (1) of any previous claim, wherein the marker substance comprises at least one metal oxide, preferably at least one transition metal oxide and / or at least one lanthanide oxide, more preferably on or more metal oxides out of the group of europium oxide, yttrium oxide, ytterbium oxide, lutetium tantalate, even more preferably yttrium oxide and / or ytterbium oxide.

12 Recyclable racket sports ball (1) of any previous claim, wherein the marker substance is distributed in the form of particles, preferably microparticles and / or nanoparticles, more preferably with a median particle size in the range of 0.05 - 1 · 10² pm as measured by laser diffraction.

13 Recyclable racket sports ball (1) of any previous claim, wherein the renewable polymeric composition comprises a natural or synthetic rubber compound, preferably at least one of natural rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, butyl rubber, EPDM rubber, more preferably comprising natural rubber and butadiene rubber.

14 Recyclable racket sports ball (1) of any previous claim, wherein the renewable polymeric composition comprises sulphur crosslinks, preferably obtained by vulcanisation.

15 Method of recycling a mixed waste stream comprising a recyclable racket sports ball (1) of any previous claim, wherein the recycling method comprises:

- (SI) detecting the marker substance of the recyclable racket sports ball (1) to identify the recyclable racket sports ball (1) within the mixed waste stream;

- (S2) separating the recyclable racket sports ball (1) from the mixed waste stream; and

- (S3) obtaining the renewable polymeric composition from the separated recyclable racket sports ball (1).

16 Method of claim 15, wherein the step (SI) of detecting the marker substance of the recyclable racket sports ball (1) comprises at least one of:

- (S 1.1) exciting the marker substance with electromagnetic radiation;

- (SI.2) collecting electromagnetic radiation emitted by the marker substance; and

- detecting photoluminescence of the marker substance, preferably infrared photoluminescence.

17 Method of claim 15 or 16, wherein the step (S3) of obtaining the renewable polymeric composition from the separated recyclable product (1) comprises at least one of:

- (S3.1) removing an outer layer (4) of the recyclable product (1);

- (S3.2) granulating the obtained renewable polymeric composition; and

- (S3.3) de-crosslinking the renewable polymeric composition for renewed use. 18 Method of any of the claims 15 - 17, further comprising (S4) forming the obtained renewable polymeric composition into recyclable racket sports balls (1) or components thereof.

19 Use of a marker substance in a seam of a racket sports ball, preferably a tennis ball or a padel ball, for identification of said ball in any angular orientation thereof in a mixed waste stream.