TECHNOLOGICAL FIELD

The invention generally contemplates methods for XRF marking of natural rubber.

BACKGROUND OF THE INVENTION

Natural rubber is a uniquely highly waterproof material typically obtained from latex- a whitish milky liquid containing proteins, starch, alkaloids, and other natural components. While the liquid may be obtained from a variety of trees, the rubber tree- Hevea brasiliensis- is the main source of the natural product. The latex is drawn off by making incisions in the bark of the tree and collecting the fluid into collection cups in a process called tapping. The latex is then refined into rubber that is ready for commercial processing.

The latex may also be allowed to coagulate in the collection cups. The coagulated lumps may be collected, processed into dry forms and sold as a raw material in a variety of industries for producing gardening products, tires and conveyer belts, cements, adhesives, footwear and rainwear, piping, marine products and other miscellaneous goods.

GENERAL DESCRIPTION

Material origination and product authentication have become of high importance in the daily use of products made from naturally derived raw materials, such as leather, silk, precious metal and stones, as well as of natural rubber. Existing methods for determining material composition that can establish material origination and authenticity are unsatisfactory for a variety of reasons, including inter alia processing complexity, the unavailability of sensitive on-the-spot methods, the destructive nature of some of these methods and others.

In many cases, on-the-spot determination of non-authentic goods is not possible for lack of available tools that can replace off-site laboratory tools for analysis. In a similar way, tools for determining product origination, particularly for unprocessed products directly derived from nature, are unavailable or are time-consuming, cost ineffective and in general suffer from such deficiencies that prevent simple determination or product origination.

There is thus a need in the art for a novel approach for proper marking of raw materials and products made therefrom for managing the use, reuse and recycling of the raw materials or products made therefrom, in particular rubber-based materials. The methodology disclosed herein permits generating a product certificate relating to the raw material or product made therefrom, which provides origination, authentication and product description and history. Such a certificate is based on the ability to mark and read by real time inspection the raw material or product.

The present invention takes advantage of earlier techniques developed by the inventors of the present application for reading electromagnetic radiation signature(s) of various material(s), in response to certain irradiation, based on specific marking embedded in the material(s), and determine properties/conditions of each material from the detected signature.

In its broadest aspect, the invention provides an x-ray fluorescence (XRF) sensitive natural rubber. According to the invention, a marking agent or a marking composition comprising one of more XRF-identifiable materials (atoms or compounds) is applied to the natural rubber, wherein the identity of the marker, and/or its concentration, and/or presence of a second or a further marker, and/or the ratio amounts between one marker and another, and/or the distribution of the marker in the rubber, and/or a ratio amount between one of the markers and a natural material present in the rubber and being also XRF-identifiable define an XRF signature certifying one or more of the rubber features. Thus, marking the natural rubber, as defined, permits forming a product certificate reflecting origination, authentication and traceability; or more specifically any one or more of the following:

-natural rubber origin, e.g., country, entity harvesting the rubber, type of trees from which the rubber was obtained, etc.

-date of harvesting,

-details and identity of company or entity harvesting the rubber,

-quality of rubber,

-processing conditions, e.g., conditions used in the harvesting of the rubber,

-the identity and location of a processing plant,

-product type, -batch number, and

-generally any other parameter relevant to the history and processing of the rubber or any of its products.

The invention also provides a process for marking natural rubber which involves applying one or more XRF-identifiable marker(s) to the natural rubber, at any stage of a process for harvesting or coagulating the rubber, under conditions that do not introduce or impose any change to the rubber or to any processing steps, and also which allows for homogenously distributing the marker(s) within the rubber, thus enabling detection of the marker at any stage thereafter, including in a finished marketable rubber product.

As known in the art, natural rubber is a product of nature harvested from the bark of certain trees. When the bark of the tree is partially cut through (tapped), a milky liquid exudes from the wound and dries to yield a rubbery substance- the latex. The latex consists of an aqueous suspension of small particles, about 0.5 micrometer in diameter, of cis-polyisoprene, a linear rubbery polymer of high molecular weight. The rubber content of the suspension is about 30 percent. The most common method of extracting the rubber from the latex uses coagulation, a process that thickens the polyisoprene into a mass. This process is accomplished by adding an acid such as formic acid to the latex. Water is squeezed out of the coagulum of rubber using a series of rollers, resulting in thin rubber sheets that may be further processes into a variety of rubber products.

The rubber sheets may be processed through four steps: compounding, mixing, shaping and vulcanizing. The rubber compounding formulation and method depends on the intended outcome of the rubber fabrication process.

Compounding adds chemicals and other additives to customize the rubber for its intended use. The chemicals added during compounding react with the rubber during the vulcanizing process to stabilize the rubber polymers. The identity of the added chemicals will depend on the intended final product.

In the stage of mixing the additives are thoroughly mixed into the rubber. The high viscosity of the rubber makes mixing difficult. In order to avoid thermal treatments which would ease the mixing process, mixing usually takes place in two stages, whereby in each stage different chemical are added. Shaping rubber products takes place any processing method known in for polymers: extrusion, calendaring, coating or molding, and casting. To achieve a final product, more than one shaping technique may be used.

Vulcanization completes the rubber-production process. Vulcanization advances crosslinking between the polymers in the rubber. The crosslinking may be tailored to meet the requirements of the final rubber product.

As used herein, reference to natural rubber encompasses reference to latex and coagulated latex, excluding rubber undergone compounding, shaping and vulcanizing. Processes of the invention aim the production of XRF-marked or XRF-sensitive latex and coagulated rubber and latex and coagulated rubber made therefrom. The coagulated rubber” is a latex or coagulated latex product having undergone natural coagulation or chemical coagulation, e.g., by using a coagulating material or a mechanical coagulation involving application of shear force or other mechanical means.

Thus, in a process for marking latex or coagulated rubber, the process comprises treating the latex or the coagulated rubber with at least one XRF-identifiable marker (neat or in a formulation form) under conditions permitting homogenous distribution of said marker in the latex or rubber. The process of marking may be integrated in a process for producing rubber, which comprises harvesting latex and coagulating the latex.

Putting it differently, in a process for producing rubber which comprises harvesting latex and/or coagulating the latex, the process further comprises a step of marking the harvested latex and/or coagulated latex with at least one XRF-identifiable marker (neat or in a formulation form) under conditions permitting homogenous distribution of said marker in the latex or coagulated latex.

The invention also provides a process for identifying natural rubber or a product made therefrom, the process comprising treating latex or rubber with at least one XRF- identifiable marker under conditions permitting homogenous distribution of said marker in the latex or rubber; and analyzing the presence of the XRF-identifiable marker in said latex or rubber. The analysis may be carried out as disclosed herein.

The XRF-identifiable marker is selected to identify a particular property, signature, information or generally define a certificate relating to the latex or rubber or products made therefrom and thus may thereafter be unequivocally identified and monitored. Where the latex or rubber is treated more than once with different markers, each of the markers may provide a latent marking that identifies a different property or information. Additionally, the concentration of the marker can also be measured enabling encoding of information by associating different codewords for different concentrations of markers.

Thus, in another aspect, there is provided a process for identifying origin, and/or production and/or commercial history (traceability) of natural rubber or a product made therefrom, the natural rubber having been marked with at least one XRF-identifiable marker, the process comprising directing an X-ray or gamma-ray radiation towards the rubber or product made therefrom and detecting a response X-ray signal emitted from the marker in response, such that said response signal is indicative of the presence, concentration or relative concentration of the marker to thereby provide information encoded by the marker on the origin, production and/or commercial history of the rubber or product made therefrom.

The invention further provides a process for identifying origin and/or production and/or commercial history of a natural rubber, the process comprising

-treating latex with a first XRF-identifiable marker at a first stage prior to coagulation thereof, to embed said first marker in the latex; wherein the first marker encoding at least one first information set, e.g., relating to origin, trees, harvesting facility, date of harvesting, etc;

-following latex coagulation treating the marked coagulated rubber with a second XRF-identifiable marker to embed said second marker in the rubber; wherein the second marker encoding at least one second information set, e.g., relating to the processing conditions, processing facilities, intended use, etc;

-optionally further treating the marked rubber with a further XRF-identifiable marker to embed said further marker in the rubber; wherein the further marker encoding at least one further information set; and

-analyzing the presence of the first and/or second and/or further XRF- identifiable markers in said rubber or in a product manufactured therefrom to identify information encoded in the first and/or second and/or information set.

The conditions used to embed the marker in the latex or rubber may change depending on a variety of factors, such as stage of marking; physical properties of the latex or rubber, e.g., viscosity; the nature of the marker, e.g., whether it is water soluble or water insoluble; presence of several markers; the temperature of the rubber, and others. Typically and as stated herein, the step of embedding the marker does not impose any change to the processing of rubber from latex or to the production of products from the rubber. Markers may be added neat, namely not dissolved, suspended or otherwise carried in a carrier, e.g., a liquid carrier, or may be added as a liquid solution or a suspension or an emulsion in an aqueous medium or an organic medium. In some embodiments, the marker is provided in formulation form and methods of the invention thus comprise treating the latex or rubber with a formulation comprising one or more XRF-identifiable markers. As used herein, the term “treating” or any lingual variation thereof encompasses adding to the latex or rubber the marker or the formulation, a water-based formulation or other non-aqueous solutions, which includes one or more markers, herein the “marker formulation”. Following the addition, the latex or rubber and the marker are mixed to homogenously distribute the marker in the latex or rubber. With increasing viscosities, to ensure homogenous distribution of the marker in the rubber, the combination or rubber and marker may be mechanically treated using e.g., a roll mill, until measurements indicate substantial homogenous distribution in the rubber. Homogenous distribution may be determined by measuring the presence of the marker in several different locations of a rubber sample, to ensure substantially identical XRF or other spectroscopic reading.

To assist in distribution of the marker in the rubber, in some embodiments, apart from the marker molecules or marker elements, a marker formulation may also include processing agents such as surfactants and water insoluble material which, in some embodiments, can be later removed.

The marker used for marking the latex or rubber may be detected and measured by X-Ray fluorescence (XRF) spectrometers (readers) which detect and identify the marker response (signature) signal(s). The XRF readers may be Energy Dispersive X- Ray fluorescence EDXRF spectrometers. XRF markers are flexible, namely, they may be combined, blended or form compounds with a huge range of carriers and materials.

The marker is an atom or a material that comprises an atom that is XRF- identifiable. The marker is typically selected not to be an atom that is present in the latex or rubber; nor in any of the processing solutions typically used in in rubber production. Using a marker that is not native to the latex or rubber enables accurate and confident encoding and further generating a complex encoding scheme. The XRF markers may be, for example, in the form of inorganic salts, metal oxides, bi or tri metal atom molecules, polyatomic ions, and organometallic molecules, as described for instance in PCT/IL2020/050794 and PCT/IL2020/050793 or any US application derived therefrom, which are herein incorporated by reference. An XRF marker or a marking formulation including several XRF markers may be designed to have a preselected set of properties.

Generally speaking, a metal or an atom used as a marker may be any atom of the periodic table that is XRF sensitive and any material containing the atom provided that the atom or the material containing same does not harm, damage or in any way modify or change properties of the latex or rubber. The atom may be presented as a salt, a complex, an organic compound or an inorganic compound. For example, where the marker is a metal or a metal containing material, e.g., organometallic material, or metal salt the metal atom may be selected from aluminum (provided as e.g., aluminum sulfate), titanium (provided as, e.g., titanium sulfate), cobalt (provided as e.g., cobalt nitrate hexahydrate, cobalt gluconate hydrate, cobalt glycinate), nickel (provided as nickel nitrate hydrate, nickel glycinate), yttrium provided as e.g., yttrium nitrate hexahydrate ), cadmium (provided as e.g., cadmium nitrate tetrahydrate), tin (provided as e.g., tin chloride), scandium, niobium, silver, tungsten, zinc, zirconium, manganese, copper, lead, molybdenum, vanadium, bismuth, antimony, tantalum and cesium (provided as e.g., cesium carbonate).

Other metal-based markers may be provided in a water-insoluble form. Such include aluminum oxide, scandium acetate, titanium oxide, cobalt acetyl acetonate, cobalt carbonate, cobalt dibromo, nickel acetyl acetonate, nickel acrylate, yttrium oxide, niobium oxide, silver carbonate, silver chloride, tin ethyl hexanoate, tungsten oxide and others.

Halide-based markers include tri-iodine phenol (TIP), tribromophenol (TBP), tri chlorophenol (TCP), 2,2-bis(bromomethyl) propane- 1,3-diol, 2,4,6-tribromo aniline, pentabromobenzyl acrylate, 4,5,6,7-tetrabromoisobenzofuran-l,3-dione, ammonium bromide and others.

In some embodiments, the marker is or comprises any atom selected from Y, Sr, Nb and Zr. In other embodiments, the marker is a combination of two or more markers, at least one of which comprises or is an atom selected from Y, Sr, Nb and Zr. In some embodiments, the marker is not any of the materials naturally present in latex or natural rubber. Putting it differently, the marker(s) used in accordance with aspects and embodiments of the invention is different (composition wise) from any of the materials naturally present in harvested latex or natural rubber or coagulated forms thereof.

Thus, in an XRF sensitive product obtained by any of the processes of the invention, the product being an XRF-marked latex, coagulated latex, coagulated rubber or natural rubber, the XRF marker is any of the aforementioned markers. In some embodiments, the marker is or comprises any of the atoms selected from Y, Sr, Nb and Zr. In other embodiments, the marker is a combination of two or more markers, at least one of which comprises or is an atom selected from Y, Sr, Nb and Zr.

In some embodiments, the invention provides an XRF sensitive natural rubber, an XRF-sensitive latex, an XRF-sensitive coagulated latex or coagulated rubber, each of which comprising at least one atom selected from atoms selected from Y, Sr, Nb and Zr.

The marked latex material or rubber material, as defined, may be characterized by a signature generated in response to the exciting / reading radiation. In the description below, the use of XRF technique is exemplified with regards to readings of materials’ signature in order to determine the material properties/conditions/origin/authentication. It should however be understood that the principles of the novel approach of the present invention are not limited to this specific type of signature/marking.

XRF markers may be detected and measured by X-Ray Fluorescence (XRF) analysis by XRF spectrometers (readers) which may detect and identify their response (signature) signals. In an example, the XRF readers are Energy Dispersive X-Ray fluorescence (ED XRF) spectrometers. XRF markers are flexible, namely, they may be combined, blended or form compounds with, or embedded within a huge range of carriers, materials, substances, and substrates, without negatively affecting their signature signals.

Due to the flexibility in using different types, combinations and amounts of the XRF-sensitive markers, the XRF markers, or a marking composition including several XRF markers (possibly with additional materials, such as carriers or additives), may be designed to have a preselected set of properties. Additionally, XRF marking can be detected and identified when markers are present under the surface of an object but not on the surface itself, for instance, when the object is covered by a packaging material, dirt or dust. Furthermore, XRF analysis enables measurement of the concentration of the markers present within a material as well as the ratio (the relative concentration) of the markers within a material.

The present invention further provides an approach for overcoming problems relating to recycling and reuse of rubber or latex materials. In particular, the present invention enables the marking and identification of rubber. Moreover, the technique of the present invention allows to identify the number of times the rubber material has undergone recycling. Furthermore, in case of a product which includes both virgin material(s) and recycled rubber materials, the composition of the product can be determined, namely, by measurement of a relation (e.g. ratio) between the virgin material, rubber material recycled once, rubber material recycled twice, and so on. To this end, a set of one or more markers are introduced to the recycled rubber material in each round of a recycling process during the overall recycling processes. Additionally, according to the invention, a virgin rubber material may also be marked by one or more markers which may be introduced into the virgin material, for example, during its harvesting as a latex material, during manufacturing of rubber products, etc.

The one or more markers are embedded within a rubber material to obtain a marked rubber material and may be detected and identified (e.g. by XRF analysis) at any stage during the life cycle of the marked rubber material.

Thus, according to one broad aspect of the invention, it provides a method for providing an XRF-identifiable latex or rubber raw material, such as natural rubber, the method comprising marking a sample of the raw material with an amount of an XRF- identifiable marker, the amount defining an electromagnetic radiation signature indicative of the raw material composition and/or production profile (the raw material data). The profile may include one or more dates of manufacture, site of manufacture, composition, presence or absence of unnatural additives, etc.

In accordance with the present invention, the rubber may be marked as detailed herein with an XRF-identifiable marker at any stage of its production. Where the rubber is mixed with at least one another material, the rubber is marked prior to mixing with the at least one another material. Marking may be during the stage latex collection, i.e., during tapping; prior to, during or after sap solidification with a solidification agent; prior to, during or after coagulation; or after the rubber is dried.

According to another broad aspect of the invention, it provides a product comprising a composition of a natural unrecycled rubber product and one or more recycled rubber materials, wherein at least one of the natural unrecycled rubber product and the recycled rubber materials comprises at least one predetermined marker capable of responding to exciting radiation by a characteristic radiation signature, embedding data indicative of one or more properties and conditions of said composition detectable from readings of said radiation signature of said at least one marker.

A reading unit may be used for detecting the marking compositions and/or measuring their concentrations or relative concentration in the preselected areas or complete area on the surface of the object. In an example the marking composition includes markers which are identifiable by XRF analysis and the verification unit comprises an XRF analyzer which emits an X-ray or Gamma-ray radiation towards the object and detects the X-ray signal (a response signal) that is emitted from the markers in response. Such an XRF analyzer may be configured to measure/estimate the concentration or relative concentration of each of the markers according to the detected response signal. The concentrations of the markers may be indicative of the information encoded by the marking composition on the object. Accordingly, based on the measured/estimated concentration the system may be configured and operable to verifying that the applied marker composition indeed matches/encodes the intended information/authentication data that should have had being marked on the object and possibly also verifies the quality of the marking applied by the marking device (i.e. the quality may be determined based on the signal to noise (SNR) of the detected signal). The invention further provides a system for managing a supply chain of latex or natural rubber or coagulated forms thereof, the system including a database system (central or distributed) where data relating to latex or rubber and their marking is stored. For example, the database system may include information relating to the origin of the latex, the manufacturer of the latex, type of latex or rubber products as well as distributers and buyers. For that purpose, the device reading the marking (e.g. an XRF analyzer) may communicate with the database system. The database system may be an on-the-premises, cloud-based system or a distributed ledger. In an example, the database system may be a distributed blockchain system wherein a plurality of parties store and access the relevant data. In such a blockchain system a plurality of parties (for example, parties which are members of the same supply chain) may store and access data wherein the data stored is immutable, easily verifiable and, due the distributed design, inherently resistant to modification. In an example, the parties to the blockchain system may include farms, production facilities, suppliers, delivery companies, and even end users. In an example the marking on a silk fiber is read (detected) by a suitable XRF device and recorded every time it changes hands along the supply chain and recorded (e.g. automatically) on the blockchain allowing each party to easily verify the provenance and complete history of the latex or rubber and/or products made therefrom. Blockchain systems that are suitable for managing a supply chain of marked objects and products are described in International Patent Applications PCT/IL2018/050499 and PCT/IL2019/050283 or any US applications derived therefrom, which are incorporated herein by reference.

The invention further provides:

A process for marking latex or coagulated latex or natural rubber, the process comprising treating the latex or the coagulated latex or the natural rubber with an amount of at least one XRF-identifiable marker under conditions permitting homogenous distribution of said marker in the latex or coagulated latex or natural rubber, wherein the amount and nature of the XRF-identifiable marker defining an electromagnetic radiation signature indicative of a production profile or a commercial history of the latex, coagulated latex or natural rubber.

The process according to the invention, wherein the production profile comprises one or more dates of harvesting, site of harvesting, date of processing, site of processing, composition, and source of latex.

The process according to the invention, the process comprising one or more of harvesting latex and/or natural rubber and/or coagulating the latex and marking the harvested latex or coagulated latex with at least one XRF-identifiable marker under conditions permitting homogenous distribution of said marker in the latex.

A process for identifying origin, and/or production and/or commercial history of natural rubber, the natural rubber having been marked with at least one XRF- identifiable marker, the process comprising directing an X-ray or gamma-ray radiation towards the natural rubber and detecting a response X-ray signal emitted from the marker in response, such that said response signal is indicative of the presence, concentration or relative concentration of the marker to thereby provide information encoded by the marker on the origin, production and/or commercial history of the natural rubber.

The process according to the invention, the process comprising treating latex or coagulated latex or the natural rubber with an amount of at least one XRF-identifiable marker under conditions permitting homogenous distribution of said marker in the latex or coagulated latex or natural rubber, wherein the amount and nature of the XRF- identifiable marker defining an electromagnetic radiation signature indicative of a production profile or a commercial history of the latex, coagulated latex or natural rubber.

The process according to the invention, wherein the latex or coagulated latex are processed to provide rubber.

The process according to the invention, the process comprising

-treating latex with a first XRF-identifiable marker at a first stage prior to coagulation thereof, to embed said first marker in the latex; wherein the first marker encoding at least one first information set;

-following latex coagulation treating the marker coagulated rubber with a second XRF-identifiable marker to embed said second marker in the rubber; wherein the second marker encoding at least one second information set;

-optionally further treating the marked rubber with a further XRF-identifiable marker to embed said further marker in the rubber; wherein the further marker encoding at least one further information set; and

-analyzing the presence of the first and/or second and/or further XRF- identifiable markers in said rubber or in a product manufactured therefrom to identify information encoded in the first and/or second and/or information set.

The process according to the invention, wherein the at least one XRF- identifiable marker is provided neat, or in a liquid solution, suspension or an emulsion in an aqueous medium or an organic medium.

The process according to the invention, wherein at least one XRF-identifiable marker is an atom or a material comprising an XRF-identifiable atom.

The process according to the invention, wherein the material is a salt, a complex, an organic compound or an inorganic compound. The process according to the invention, wherein the atom is selected from aluminum, titanium, cobalt, nickel, yttrium, cadmium, tin, scandium, niobium, silver, tungsten, zinc, zirconium, manganese, copper, lead, molybdenum, vanadium, bismuth, antimony, tantalum, strontium and cesium.

The process according to the invention, wherein the marker is or comprises an atom selected from Y, Sr, Nb and Zr.

An XRF sensitive latex or coagulated latex obtained by the process of any one of claims 1 to 12.

The latex or coagulated latex according to the invention, comprising an XRF marker that is or comprises an atom selected from Y, Sr, Nb and Zr.

The natural rubber according to the invention, comprising an XRF marker that is or comprises an atom selected from Y, Sr, Nb and Zr.

A system for managing a supply chain of latex, rubber or coagulated forms thereof, the system comprising a database system (central or distributed) comprising data relating to the latex or rubber or coagulated forms and their marking with an XRF- identifiable marker.

DETAILED DESCRIPTION OF EMBODIMENTS

In its broadest aspect, the invention provides an x-ray fluorescence (XRF) sensitive natural rubber and a method of manufacturing same. In the following examples, latex and coagulated rubber were separately treated with a marker to receive a homogenous XRF sensitive product. In an identical manner to the introduction of the marker materials mentioned below, other marker materials may be used to achieve the XRF sensitive rubber.

Natural rubber was obtained according to known methods in the art and was used without further processing.

Example 1 - Coagulated Rubber

Materials:

1) CV-60 Rubber

2) Marking system A: YC13*6H2O and SrCh*6H2O

3) Marking system B: Nb2Os and ZrCh Experiment Description:

Initially, a roll mill unit was cleaned with CV-60 and was processed for a period of at least 20 minutes in order to make sure that no markers could be derived from contaminating impurities. This was verified.

Thereafter, 1 kg of rubber CV-60 was inserted into the roll mill unit and the rubber was processed by “breaking” the sample. After at least 10 min of rubber processing, the rubber was heated by friction on the rolls to a temperature between 60- 80 °C (without any further heating from the machinery) and the rubber was made into a single piece. Markers were added at this stage.

For better embedding of markers, a gap of 0cm was set on the roll mill. This way, high shear forces induced better mixing of the marker. Processing was continued for a period of 10 minutes. Three samples from different locations along the sheet were cut. Each piece was measured for the presence of the marker - a total of 9 measurements. The process was repeated until the homogeneity of the markers was good and did not improve (less than 10%).

Same process was repeated with rubber samples from various sources. In all cases, XRF sensitive rubber materials were obtained.

Each of the two marking systems was used in different samples, each providing a different reading and marking signatures.

Example 2 - Latex

Materials:

1) Latex

2) Marking system A: YC13*6H2O and SrCh*6H2O

3) Marking system B: Nb2CL and ZrCL

Experiment Description:

Liquid latex marking was performed using a liquid latex-ammonia solution. The two marking systems used differed in their solubility in water. The first system was based on water-soluble markers - YCI3 and SrCh. The markers were initially dried in a vacuum oven at ~40°C for 24 hours due to their hygroscopic nature. Then, the dried markers were dissolved in 60 g deionized water. The aqueous marker solution was slowly dripped into 850 g liquid rubber, resulting in a final marker concentration of 0.0078%. The mixture was thoroughly stirred to form a homogenized solution. The second marking system was based on water-insoluble markers - Z1O2 and Nb20s. The markers were added in their powder form into 850 g liquid latex, resulting in a final marker concentration of 78ppm. The materials were thoroughly stirred to form a homogenized mixture.

For both marking systems, the solution was cast in a square mold to form a thin layer (~0.5 cm). The solution was left to dry (ammonia evaporation) for 72 hours under normal conditions. 72 hours later, a flat sheet of marked rubber was obtained.

In the Examples provided herein, the amount of the XRF sensitive material added to the latex or rubber is modified based on the material used. The amount added is typically selected to provide a concentration of the XRF sensitive atom that is the desired concentration. In some embodiments the amount of the XRF sensitive atom is 78ppm or above lOOppm. In some cases the amount of the XRF sensitive atom is between lOppm and lOOppm.

Example 3 - Processing XRF sensitive rubber

Any of the marked rubber materials obtained following the methodology disclosed herein may be processed to achieve a desired end product. The marker content did not change any of the rubber properties as initially measured.

Example 4 - Tree to Bale

Two rubber samples were used

-Rubber sample embedded with marking system A; and

-Rubber sample embedded with marking system B.

0.1% lime solution - Ca(OH)2 was used as well.

Experiment Description:

A rubber sheet embedded with a marker system was processed in a lab environment. Rubber processing with different marker systems was done separately and performed in different days.

150g marked rubber sample was weighted and cut into smaller pieces in size of approximately 30x30mm. The cut rubber pieces were placed in a mesh basket and rinsed through with running tap water and stirred manually for 5 minutes. These steps were repeated for 3 times until the rubber crumbs size achieved to approximately 10mm. The wet rubber crumbs were collected in a mesh basket and shook manually for 1 minute to remove the excessive water on the surface. Thereafter, the rubber crumbs were passed through the 2 roll-mill unit at the nip setting of 5mm for 7 times and rinsed with tap water in between the steps. Final rubber crumbs size reduction was done by manual scissors cut into the size of 3-5mm and then immersed in a tray contained of 0.1% lime solution and stirred constantly for 5 minutes. The rubber crumbs were then removed from the tray and left air-dried in a controlled room temperature at 25°C for more than 12 hours. After the air-drying process, the rubber crumbs were placed into the lab oven at 130°C for 1 hour. The final step was to sheet out the dried rubber by passing through the 2 roll-mill unit at room temperature, with the nip setting at 0.1mm. The rubber sheets were in average achieved a thickness of 2mm.

Example 5 - Bale to Tire

Three rubber samples were used

1) Rubber sample embedded with marking system A;

2) Rubber sample embedded with marking system B;

3) Unmarked rubber bale.

A marked rubber sample was blended with unmarked natural rubber bale to produce diluted rubber sheet with marker system at 20%, 50% and 100% by mass percentage (w/w%) at 800g, this blending step was performed in a 2 roll-mill unit for 5 mins. After each of the blending steps, the 2 roll-mill unit was cleaned thoroughly with CV-60 rubber for a period of 5 minutes to avoid cross -contamination from previous blending steps.

Thereafter, the individual mixing was conducted in an internal mixer using a reference compound and cured at 160°C for 15mins. Mixing recipe as per following:

The cured rubber discs were cut into standard ring size, with a thickness of 6mm and tensile testing were performed to check the impact of marker particles towards compound physical properties. No significant impact was observed in comparison to the unmarked rubber disk and the marked rubber disks at all marker concentration levels (20%, 50% and 100%), for both marker system A and marker system B.