WO2024174029A1 - A method to degrade rubber materials - Google Patents

Abstract

There is provided a method for the degradation of a rubber material. The method comprises providing a rubber material contacted with catalytic system, wherein the catalytic system is adapted for an in situ production of hydrogen peroxide, and wherein the hydrogen peroxide generates radicals which cause the degradation of the rubber material. Also, there is provided a catalytic system for use in the degradation of a rubber material. Moreover, there is provided a kit for use in the degradation of a rubber material.

Description

TITLE OF THE INVENTION

A METHOD TO DEGRADE RUBBER MATERIALS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Patent Application No. 63/486,763 filed on February 24, 2023. The content of this application is incorporated herein in its entirety by reference.

FIELD OF THE INVENTION

[0002] The invention relates generally to methods for the degradation of rubber materials. More specifically, the invention relates to a method which comprises providing a rubber material contacted with a catalytic system that promotes in situ production of hydrogen peroxide, which is then used to generate radicals, causing the degradation of the rubber material. The method according to the invention allows for processing rubber materials directly in typical waste streams with no need for their separation from other waste materials or addition of chemical agents.

BACKGROUND OF THE INVENTION

[0003] Rubber materials are common materials appreciated for their strong and customizable elastomeric properties. They are used as main components in the manufacture of many day-to-day objects such as but not limited to tires, gloves, condoms, hoses, baby teats, seals, and O-rings. Also, rubber materials enter the composition of composite blends of many more objects. They can also be included in composite materials to optimize their physical or chemical properties.

[0004] A variety of elastomeric carbon-based materials have been developed including natural rubber (NR), butyl rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), c/s-isoprene rubber, trans- isoprene rubber, epoxidized rubber, silicon rubber, gutta percha, halobutyl rubber, nitrile butadiene rubber (NBR), neoprene (polychloroprene), ethylene propylene diene monomer (EDPM), fluoroelastomers including FKMs, and combinations thereof. These materials offer enhanced resistance to water, solvents, chemical agents, atmospheric conditions, high temperature and pressure and have enabled many applications. [0005] Elastomeric materials can be prepared using various methods. Rubber films can be cast, i.e., a rubber latex suspension is deposited on a plate and the liquid fraction removed by evaporation, dipped, i.e., a rubber film is formed at the surface of a former by immersing it in a rubber latex suspension and dried subsequently. Rubber objects can be fabricated using various techniques, including extrusion, compression molding, injection molding, transfer molding, calendaring, and 3D printing. The properties of the prepared rubbery material depend on its vulcanization state i.e., the nature and degree of cross-linking created between polymer strands during the preparation of the material. Vulcanization is a chemical reaction which can be conducted in various ways although two approaches are preferred in the industry, sulfur curing and peroxide curing. In the former, the cross-linking is achieved with sulfide or oligo-sulfide covalent bonds whereas the latter forms carbon-carbon covalent bonds.

[0006] The resistance of rubber materials to extreme conditions makes their disposal problematic as they will tend to endure for decades or centuries in landfills. The alternative being their incineration which comes with added carbon emissions. Achieving fast, efficient, and environmentally responsible degradation of rubber materials is therefore paramount in limiting carbon emissions for many industries. However, few recycling processes are available for rubber materials and most of them end up in landfills or in incinerators. While some are thermoplastic and can be recast or remolded allowing for reuse, other rubber materials are thermoset and require chemical recycling or degradation into new molecules. This is the case, for example, of latex gloves, balloons, and condoms among others.

[0007] In the case of thermoset materials, both biodegradation and chemical degradation have been considered.

[0008] The biodegradation of natural rubber has been the most studied. Although naturally sourced from Hevea trees, natural rubber is resistant to biodegradation, especially after the vulcanization process, designed to improve the strength and elastomeric properties of the polymer by introducing crosslinking i.e., chemical bonds in between polymer chains. Studies report that even after 6 months buried in soil, less than 5% mass loss of rubber polymer was measured [1], The isolation of microorganisms able to metabolize vulcanized rubber was conducted and several promising strains were identified but even such organisms have a slow action. In the case of Streptomyces strains isolated from vulcanized gaskets, 12 months were required to poke holes in the material [2], Some strains were more efficient in the degradation of natural rubber gloves which lost 75% of their mass over 2 weeks [3], The strain’s action was however slower on other rubber-based products such as rubber bands, tubing, and stoppers, which required more than 8 weeks to obtain observable results.

[0009] There are however settings where degradation of rubbers is desirable but their exposition to a specific microbial strain is difficult to achieve. Such settings include, but are not limited to, most natural environments where rubbers might be abandoned, backyard or industrial composting from which the desired strains are absent or in which the conditions (temperature, humidity, pH, etc.) are incompatible with their growth. Even if the setting is artificially enriched with the desired strain, competition with native organisms is likely to severely impede their action or altogether prevent rubber degradation.

[0010] The sensitivity of rubbers to radicals generated by light, UV irradiation, ozone, and peroxides, typically but not restricted to hydrogen peroxide, or combinations thereof, is well known [4-10], The radicals trigger a p-scission reaction which breaks down polymer chains and generate aldehyde and ketone moieties. Sato et al. [11 ,12] and Enoki et al. [13] independently report the use of enzymes to generate radicals able to break down various types of rubbers. The catalytic system they use includes peroxidases, enzymes capable of using hydrogen peroxide as a co-substrate to oxidize small molecules into radicals. These mobile radicals, also referred to as shuttles or mediators, interact with the polymer chains and initiate chain reactions that result in polymer matrix break down [11 ,13], The authors report a 50% mass loss from vulcanized rubber in just 4 days.

[0011] Methods known in the art for the degradation of rubber materials including the methods described herein above generally present severe limitations when considering plastic commodities, generally considered single-use or, at least, disposable, and of limited economic value. Most rubber products are disposed of in non-specific ways and are mixed with other materials of diverse origin and chemical nature. Segregation of the rubbers, a costly operation, is thus often necessary to minimize the occurrence of side reactions and limit reagent use. Moreover, light or gas exposure at the industrial level requires specific reactors and further investment. Finally, hydrogen peroxide, the preferred rubber-degrading reagent, is corrosive, toxic, and is an acute skin sensitizer, and thus must be used in controlled settings away from customers. For these reasons, methods commonly known in the art are difficult to apply at the industrial level to most rubber products. [0012] There is a need for improved methods for the degradation of rubber materials. In particular, there is a need for such methods that are efficient, cost-effective and that does not present a risk for the user’s health.

SUMMARY OF THE INVENTION

[0013] The inventors have designed and developed a method for the degradation of a rubber material. The method comprises providing a rubber material contacted with a catalytic system that promotes in situ production of radicals, with hydrogen peroxide as an intermediate, causing the degradation of the rubber material. The method according to the invention allows for processing rubber materials directly in typical waste streams with no need for their separation from other waste materials or addition of chemical agents.

[0014] In embodiments of the invention, the catalytic system comprises: a first catalyst, an initiating agent, and a second catalyst. Optionally, the catalytic system comprises a mediator. The first catalyst is suitable for reacting with the initiating agent to generate hydrogen peroxide; and the second catalyst is suitable for reacting with hydrogen peroxide to produce radicals directly, or is suitable for using hydrogen peroxide to react with the mediator to produce radicals. The radicals subsequently cause the degradation of the rubber material.

[0015] In embodiments of the invention, the catalytic system contacts the rubber material externally and/or internally. Also, the catalytic system may be embedded (or incorporated or encapsulated or immobilized) within the rubber material. In embodiments of the invention, the catalytic system may be in liquid form, solid form, or a combination thereof.

[0016] In embodiments of the invention, the first catalyst or hydrogen peroxidegenerating catalyst may comprise any suitable enzymatic and/or non-enzymatic catalyst used in a chemical or biochemical process to generate hydrogen peroxide.

[0017] In embodiments of the invention, the initiating agent may be any molecule or polymer suitable for acting as a substrate for the first catalyst. In preferred embodiments the initiating agent comprises lignin and/or starch.

[0018] In embodiments of the invention, the second catalyst may comprise cations and corresponding metal complexes capable of achieving Fenton-type reactions; and/or enzymes which possess other activities than reaction with hydrogen peroxide and which may be described otherwise than peroxidase, including the cytochrome P450 family and other cytochromes. In preferred embodiments, the second catalyst comprises manganese peroxidase (MnP) and/or horse radish peroxidase (HRP).

[0019] In embodiments of the invention, the mediator may comprise any molecule suitable to be turned into a radical or into a chemical species prone to decompose into radicals by a catalytic system and then promote homolytic bond breaking within a polymer; and/or any suitable molecule known to adopt a stable yet reactive radical form and to ease a radical transfer. In preferred embodiments, the mediator comprises linoleic acid and/or 1 -hydroxybenzotriazole (HOBt).

[0020] In embodiments of the invention, the catalytic system is adapted for an in situ production of radicals, under suitable conditions. Such conditions may be humidity- related, temperature-related, pH-related, and/or buffer-related. The conditions depend on the nature of the contact between the polymer and the catalytic system (internal or external) and the state in which the reaction is conducted (in solution or as solids).

[0021] In embodiments of the invention, the rubber material may be of various nature as described herein, for example, the rubber material may comprise natural rubber (NR).

[0022] In other embodiments, there is provide a catalytic system used in the method according to the invention. Also, a kit for use in the degradation of a rubber material is provided. Moreover, there is provided a waste treatment facility which embodies the method according to the invention as well a facility which produces the catalytic system as well as the kit use in conducting the method.

[0023] The invention thus provides the following in accordance with aspects thereof:

(1). A method for the degradation of a rubber material, comprising providing a rubber material contacted with catalytic system, wherein the catalytic system is adapted for an in situ production of hydrogen peroxide, and wherein the hydrogen peroxide generates radicals which cause the degradation of the rubber material.

(2). The method according to (1) above, wherein the catalytic system contacts the rubber material externally and/or internally.

(3). The method according to (1) above, wherein the catalytic system is embedded (or incorporated or encapsulated or immobilized) within the rubber material. (4). The method according to any one of (1) to (3) above, wherein the catalytic system is in liquid form, solid form, or a combination thereof.

(5). The method according to any one of (1) to (4) above, wherein the catalytic system comprises: a first catalyst, an initiating agent, and a second catalyst; and wherein the first catalyst reacts with the initiating agent to generate the hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to produce the radicals which cause the degradation of the rubber material.

(6). The method according to any one of (1) to (4) above, wherein the catalytic system comprises: a first catalyst, an initiating agent, a second catalyst, and a mediator; and wherein the first catalyst reacts with the initiating agent to generate the hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to react with the mediator to produce the radicals which cause the degradation of the rubber material.

(7). The method according to (5) or (6) above, wherein the first catalyst comprises any suitable enzymatic and/or non-enzymatic catalyst used in a chemical or biochemical process to generate hydrogen peroxide; preferably the first catalyst comprises: an enzyme selected from the group consisting of: laccases, glucose oxidase, galactose oxidase, glyoxal oxidase, superoxide dismutase, alcohol oxidase, cholesterol oxidase, aryl-alcohol oxidase, oxalate oxidase, mono-amine oxidase, NADPH oxidase, NADH oxidase, lactate oxidase, pyruvate oxidase, D-amino acid oxidase, diamine oxidase, polyamine oxidase, glycolate oxidase, xanthine oxidase, and combinations thereof; and/or an organic molecule selected from the group consisting of: anthraquinone, flavonoids, and combinations thereof; and/or a metal complex selected from the group consisting of: cobalt, copper and manganese complexes, hematite, nickel oxide, cobalt sulfide; and/or a nanomaterial selected from the group consisting of: palladium gold nanoparticles, bismuth titanate nanosheets, metal-organic frameworks, carbon nanotubes, graphene, and combinations thereof.

(8). The method according to any one of (5) to (7) above, wherein the initiating agent comprises any molecule or polymer suitable for acting as a substrate for the first catalyst; preferably the initiating agent is selected from the group consisting of: lignin, cellulose, hemicellulose, starch, glucose or other carbohydrate (possibly generated from the hydrolysis of biopolymers), proteins, peptides, oligopeptides, or amino-acids (including those generated by hydrolysis of proteins), humic substances, and combinations thereof; more preferably the initiating agent comprises lignin and/or starch. (9). The method according to (5) above, wherein the second catalyst comprises an enzyme or set of enzymes or metal complex or molecule or polymer suitable for reacting with the hydrogen peroxide to generate the radicals.

(10). The method according to (6) above, wherein the second catalyst comprises an enzyme or set of enzymes or metal complex or molecule or polymer suitable for using the hydrogen peroxide to react with the mediator to generate the radicals.

(11). The method according to any one of (5) to (10) above, wherein the second catalyst comprises cations and corresponding metal complexes capable of achieving Fenton-type reactions; and/or enzymes which possess other activities than reaction with hydrogen peroxide and which may be described otherwise than peroxidase, including the cytochrome P450 family and other cytochromes; preferably the second catalyst comprises one or more of: iron (II) sulfate, iron (II) oxalate, iron (II) lactate, hemin, iron(ll) and humic acid complex; enzymes of the peroxidase class such as manganese peroxidase (MnP), horseradish peroxidase (HRP), NADH peroxidase, myeloperoxidase, lactoperoxidase, lipid peroxidase, lignin peroxidase, hemoglobin, and cytochrome C; combined enzymes such as glutathione peroxidase and horseradish peroxidase; and combinations thereof; more preferably the second catalyst comprises manganese peroxidase (MnP) and/or horse radish peroxidase (HRP).

(12). The method according to (6) or (10) above, wherein the mediator comprises any molecule suitable to be turned into a radical or into a chemical species prone to decompose into radicals by a catalytic system and then promote homolytic bond breaking within a polymer; and/or any suitable molecule known to adopt a stable yet reactive radical form and to ease a radical transfer; preferably the mediator is selected from the group consisting of: linoleic acid; hydroxybenzotriazole (HOBt); unsaturated fatty acids such as oleic acid, palmitoleic acid, linolenic acid, arachidonic acid, and their salts; phenols such as vanillin, para-coumaric acid, syringaldehyde, veratryl alcohol, tyrosine, humin and humic acid, and phenol red; aldehybes such as 2,4-decadienal, 2- butenedial; molecules containing an NOH group such as 2,2,6,6-tetramethylpiperidin-1- yl)oxyl (TEMPO), N-hydroxynaphthalimide, N-hydroxyacetanilide, and N- hydroxymaleimide; thiazolines and thiazines such as 2,2’-azinobis-(3- ethylbenzthiazoline-6-sulphonate (ABTS) and chlorpromazine, violuric acid (VLA); quinones such as anthraquinone and Remazol Brilliant blue, di- and trimethoxybenzenes such as 1 ,4-dimethoxybenzene (DMB) and 2-chloro-1 ,4- dimethoxybenzene (2CI-1 ,4-DMB); flavins; tetrazoles; tetrazolones; and combinations thereof; more preferably the mediator comprises linoleic acid and/or HOBt.

(13). The method according to any one of (1) to (12) above, wherein the rubber material is selected from the group consisting of: natural rubber (NR), butyl rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), c/s-isoprene rubber, frans-isoprene rubber, epoxidized rubber, silicon, gutta percha, halobutyl rubber (HBR), nitrile butadiene rubber (NBR), neoprene (polychloroprene), ethylene propylene diene monomer (EDPM), fluoroelastomers including FKMs, and combinations thereof; preferably the rubber material comprises natural rubber (NR).

(14). The method according to any one of (1) to (13) above, wherein the rubber material is a blend or a composite material.

(15). The method according to any one of (1) to (14) above, wherein the rubber material has undergone a chemical modification; optionally the chemical modification is local or general; optionally the chemical modification is in bulk or at a surface thereof.

(16). The method according to any one of (1) to (15) above, wherein the rubber material is prepared by a method selected from the group consisting of: extrusion, injection molding, compression molding, transfer molding, calendaring, dipping, casting, coating, 3D printing, and combinations thereof.

(17). The method according to any one of (1) to (16) above, wherein the rubber material is uncured (non-cross linked) or vulcanized (cross linked); optionally vulcanization uses sulfur curing technique or peroxide curing technique.

(18). The method according to any one of (1) to (17) above, wherein the rubber material is thermoplastic or a thermoset.

(19). The method according to any one of (1) to (18) above, wherein conditions associated with the in situ production of the hydrogen peroxide and the radicals depend on one or more of: temperature, pH, buffer, and humidity; preferably the conditions depend on temperature.

(20). A catalytic system for use in the degradation of a rubber material, comprising: a first catalyst, an initiating agent, and a second catalyst, wherein the first catalyst is adapted to react with the initiating agent to generate hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to produce radicals which cause the degradation of the rubber material.

(21). A catalytic system for use in the degradation of a rubber material, comprising: a first catalyst, an initiating agent, a second catalyst, and a mediator, wherein the first catalyst is adapted to react with the initiating agent to generate hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to react with the mediator to produce radicals which cause the degradation of the rubber material.

(22). A kit for use in the degradation of a rubber material, comprising: a first catalyst, an initiating agent, a second catalyst, and instructions for use, wherein the first catalyst is adapted to react with the initiating agent to generate hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to produce radicals which cause the degradation of the rubber material.

(23). A kit for use in the degradation of a rubber material, comprising: a first catalyst, an initiating agent, a second catalyst, a mediator, and instructions for use, wherein the first catalyst is adapted to react with the initiating agent to generate hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to react with the mediator to produce radicals which cause the degradation of the rubber material.

(24). A rubber material contacted with the catalytic system as defined in (20) or (21) above.

(25). A waste treatment facility, which embodies the method as defined in any one of (1) to (19) above; preferably the facility is an industrial facility.

(26). A facility adapted for producing the catalytic system as defined in (20) or (21) above; preferably the facility is an industrial facility.

(27). A facility adapted for producing the kit as defined in (22) or (23) above; preferably the facility is an industrial facility.

[0024] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0026] In the appended drawings:

[0027] Figure 1 : FTIR spectrum of peroxide-cured natural rubber (NR) film incubated in a solution contaning laccase and horseradish peroxidase (HRP) for 7 days at 35°C.

[0028] Figure 2: FTIR spectrum of peroxide-cured NR film incubated in a solution contaning laccase and manganese peroxidase (MnP) for 7 days at 35°C.

[0029] Figure 3: TGA of peroxide-cured NR films incubated in solutions containing buffer only (top left), laccase and MnP (top right), laccase and HRP (bottom).

[0030] Figure 4: TGA (left) and visual aspect (right) of sulfur-cured dipped (top) or cast (bottom) NR films incubated in solutions containing laccase and HRP in sodium acetate buffer and with 50 mM mediators concentration.

[0031] Figure 5: Schiff staining of sulfur-cured (A,C) or peroxide-cured (B,D) NR films incubated in solutions containing laccase, humic acid, and iron(ll) chloride (A, B) or laccase and hemin (C, D) for 14 days at 35°C, 100 rpm. The pink-purple coloration indicates the presence of aldehydes. Soluble aldehydes were also detected (E). Middle: Schiff staining of the solutions in which the films above were incubated. An untreated sulfur-cured film does not show color (F).

[0032] Figure 6: Physical aspect of NR films incubated for 4 days at 35°C. A) Without enzymes; B) with embedded enzymes but without mediators, external lignin; C) with embedded enzymes and mediators, external lignin; D) with embedded enzymes, mediator, and lignin.

[0033] Figure 7: FTIR spectra showing the effect of laccase and HRP embedded inside a NR film incubated for 4 days at 35°C. Lignin was contacted at the surface of the film.

[0034] Figure 8: FTIR spectra showing the effect of laccase and HRP embedded inside a NR film incubated for 4 days at 35°C. Lignin was embedded inside the film. [0035] Figure 9: TGA of NR films without embedded enzymes (top left), with embedded enzyme and lignin contacted externally (top right), with embedded enzymes and lignin (bottom).

[0036] Figure 10: Physical aspect of peroxide-cured NR films incubated in compost for 14 days at 58°C. Left: with laccase, HRP, and mediators. Right: enzymes were omitted

[0037] Figure 11 : FTIR spectra of cured NR films with enzyme-loaded starch particles incubated for 7 days at 58°C. Mediators were embedded in the film. Lignin was provided either embedded in the film or as a powder in contact with the film.

[0038] Figure 12: TGA of NR films with incorporated starch particles containing the enzymes. The mediators and lignin were incorporated in the film at the casting step.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0039] Before the present invention is further described, it is to be understood that the invention is not limited to the particular embodiments described below, as variations of these embodiments may be made and still fall within the scope of the appended claims. It is also to be understood that the terminology employed is for the purpose of describing particular embodiments; and is not intended to be limiting. Instead, the scope of the present invention will be established by the appended claims.

[0040] In order to provide a clear and consistent understanding of the terms used in the present specification, a number of definitions are provided below. Moreover, unless defined otherwise, all technical and scientific terms as used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure pertains.

[0041] Use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one”. Similarly, the word “another” may mean at least a second or more.

[0042] As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0043] As used herein, the term “rubber material” refers to materials as described in detail in the Background section of the present specification. Herein, this term is used interchangeably with the terms “elastomeric material” or “elastomer”. These terms are meant to also include a material comprising rubber or rubber-based material or composite material.

[0044] As used herein, the term “contacted” as it relates to the catalytic system and the rubber material, means that the catalytic system is in contact with the rubber material. The contact can be external and the term “contacted externally” is used, or the contact can be internal and the term “contacted internally” is used. In this later case the terms “embedded”, “incorporated”, and “encapsulated” are also used. Accordingly, the terms “contacted internally”, “incorporated”, and “encapsulated” are used interchangeably. The term “immobilized” is also used in this regard.

[0045] The inventors have designed and developed a method for the degradation of a rubber material. The method comprises providing a rubber material contacted with a catalytic system that promotes in situ production of radicals causing the degradation of the rubber material. The method according to the invention allows for processing rubber materials directly in typical waste streams with no need for their separation from other waste materials. The method may take place in natural settings such as soil or in common industrial facilities. This allows for composting without any further intervention be it human or through an automated process. As will be understood by a skilled person, the active chemical, preferably hydrogen peroxide, is generated in situ.

[0046] The inventors reasoned that in situ generation of hydrogen peroxide from a benign naturally occurring substrate would be beneficial at several levels: low concentration of oxidant, degradation taking place in natural setting (biodegradation, composting), compatibility with natural microbiome, opportunity for Trojan horse strategy. The latter would allow the development of smart materials whose degradation could be triggered at the opportune moment, for example in conditions met only during biodegradation or composting processes.

[0047] Many enzymes are known to generate hydrogen peroxide from a substrate and molecular oxygen, including but not limited to laccases, glucose oxidase, galactose oxidase, glyoxal oxidase, superoxide dismutase, alcohol oxidase, cholesterol oxidase, aryl-alcohol oxidase, oxalate oxidase, mono-amine oxidase, NADPH oxidase, NADH oxidase, lactate oxidase, pyruvate oxidase, D-amino acid oxidase, diamine oxidase, polyamine oxidase, glycolate oxidase, xanthine oxidase. In theory, any of these enzymes can be used in a biochemical process to generate hydrogen peroxide provided an adequate substrate is present.

[0048] Hydrogen peroxide generation can also be achieved by non-enzymatic means including metal-containing homogeneous catalysts such as various cobalt, copper and manganese complexes and heterogenous catalysts various oxides and sulfides like hematite, nickel oxide cobalt sulfide, palladium gold nanoparticles or bismuth titanate nanosheets or metal-organic frameworks. Non-metal containing materials have also been identified like anthraquinone, flavonoids, carbon nanotubes and graphene. In accordance with the present invention, the high reactivity, specificity, and relatively harmless nature of enzymes for the initiating reagent may be preferred to control the moment and rate of radical generation and limit the overall environmental impact of the degradation process.

[0049] The hydrogen peroxide produced can then be utilized by another catalyst, consisting of an enzyme or set of enzymes or metal complex, to promote the ultimate formation of radicals that will then degrade the rubber polymer, provided the adequate substrate is present. Such catalysts include but are not limited to cations and corresponding metal complexes capable of achieving Fenton-type reactions: iron (II) sulfate, iron (II) oxalate, iron (II) lactate, hemin, enzymes of the peroxidase class, including, among others, manganese peroxidase (MnP), horseradish peroxidase (HRP), NADH peroxidase, myeloperoxidase, lactoperoxidase, lipid peroxidase, lignin peroxidase, cytochrome C, or combined enzymes such as the association of glutathione peroxidase and horseradish peroxidase. All enzymes mentioned can be sourced from various organisms and will require specific preferred conditions to operate.

[0050] The method presented uses naturally occurring compounds or polymers to initiate an enzymatic or chemo-enzymatic cascade that generates small molecules able to react with the rubber polymer chains and break them. Such compounds may include but are not limited to lignin, cellulose, hemicellulose, starch, glucose or other carbohydrate (possibly generated from the hydrolysis of biopolymers), amino-acids (including those generated by hydrolysis of proteins), humic substances or any molecule or polymer susceptible to act as a substrate for the hydrogen peroxide-generating enzymes mentioned above and combination thereof. The initiating agent can be provided externally as a solution or suspension, as a dry powder, or be directly incorporated to the polymer as a Trojan horse strategy.

[0051] The target rubber materials may include but are not limited to natural rubber (NR), butyl rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), cis-isoprene rubber, trans-isoprene rubber, epoxidized rubber, silicon rubber, gutta percha, halobutyl rubber, nitrile butadiene rubber (NBR), neoprene (polychloroprene), ethylene propylene diene monomer (EDPM), fluoroelastomers including FKMs, and any combination thereof. It may also include any composite blend in which the rubber material constitutes a significant part (10% or more). It may also include any material where part of the rubber has been chemically modified such as in the case of epoxidized rubber. The above elastomers may be prepared by any method known in the art including extrusion, injection molding diping, etc. The elastomer may be vulcanized by any known method in the art including sulfur or peroxide curing. It may also be uncured (obtained by water evaporation from an emulsion). It may or may not contain additives such as, among others, antioxidants, dyes or coloring agents, scorching agents, curing agents, or emulsifiers.

[0052] In composites, the enzymatic cascade can be used in association with any other enzyme, catalyst, or other chemical agent capable of degrading any component of the material. For example, this includes the addition of hydrolytic enzymes to degrade a rubber-polylactic acid or rubber-polyester composite. Enzymes, catalysts, or other chemical agents may be added with the purpose of breaking the crosslinking in between polymer chains and speed up degradation. The combination of the enzymatic cascade with enzymes known to degrade natural rubber can also be achieved. Such enzymes include rubber oxidases A and B (Rox A, Rox B), latex clearing proteins (Lcp). The initiation of the cascade can also be achieved in multiple steps such as in the addition of amylase to starch to generate glucose which can act as a substrate of glucose oxidase to generate hydrogen peroxide. In this case, starch is the initiating agent, but the cascade is now made of three steps.

[0053] The products of the reaction typically produce lower molecular weight polymer chains which can be observed using, for example, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), or any adequate technique. The soluble molecules created can be detected using the adequate assay or technique including colorimetric and fluorogenic assays, gas chromatography (GC), high-performance chromatography (HPLC), nuclear magnetic resonance (NMR), Fourier-transform Infrared (FTIR) spectroscopy, mass spectrometry (MS) and any combination thereof. One can also monitor the evolution of the physical properties of the rubber material such as tensile strength, modulus, and elongation at break. Finally, bioavailability of the carbon freed during polymer degradation can be monitored by CO₂ evolution.

[0054] The inventors report the use of such enzymatic and chemo-enzymatic cascades that promote the degradation of rubber materials. Three variations are presented: 1- where the catalytic system is present in solution and is contacted with the solid polymer and the initiating compound is present in suspension, 2- where the catalytic system in solution is incorporated inside the polymer before the initiating agent is contacted as a dry or damp solid, 3- where the catalytic system is encapsulated in particles which are then incorporated in the polymer and then contacted with the initiating agent (in suspension or as a dry or damp solid).

[0055] The mediators, small molecules in charge of promoting the transfer of radical moieties from the enzyme active site to the polymer typically used in this study are linoleic acid and hydroxybenzotriazole (HOBt), however any molecule known to be turned into a radical by the enzymatic system and then able to promote homolytic bond breaking within the polymer is suitable. Preferred examples are unsaturated fatty acids such as oleic acid, palmitoleic acid, linolenic acid, arachidonic acid, and their salts. Other molecules are known to adopt a stable yet reactive radical and to ease the radical transfer including but not limited to phenols such as vanillin, para-coumaric acid, syringaldehyde, veratryl alcohol, tyrosine, humin and humic acid, and phenol red, aldehydes such as 2,4-decadienal, 2-butenedial, molecules containing an NOH group such as 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), N-hydroxynaphthalimide, N- hydroxyacetanilide, and N-hydroxymaleimide, thiazolines and thiazines such as 2,2’- azinobis-(3-ethylbenzthiazoline-6-sulphonate (ABTS) and chlorpromazine, violuric acid (VLA), quinones such as anthraquinone and Remazol Brilliant blue, di- and trimethoxybenzenes such as 1 ,4-dimethoxybenzene (DMB) and 2-chloro-1 ,4- dimethoxybenzene (2CI-1 ,4-DMB), flavins, tetrazoles, and tetrazolones.

[0056] The mediators and initiating agent can be provided externally (as a solution, suspension, or a damp or dry powder), embedded into the rubber material, or encapsulated to allow for controlled release and degradation of the polymer. [0057] The embedding or encapsulation of enzymes, mediators or initiating agent inside or at the surface of particles may be achieved by any means known in the art with the purposes of protecting the enzymes through conditions that may denature them including but not limited to temperature, pH, mechanical stress, or chemical denaturants, or to delay their action to the opportune moment via controlled release.

[0058] The degradation phase can take place in solution, still or under agitation. In such conditions, it is preferrable to choose a buffer which contains a preferred salt at a preferred concentration and pH for the enzymes used. For example, in the case of manganese peroxidase (MnP), a buffer containing sodium oxalate at 10 mM and pH 4.5 is preferred although deviation is allowed. In the case where more than one enzyme is present, one should prefer a buffer salt concentration and pH where both enzymes can operate. Temperature should also be chosen in order to guarantee enzyme activity and stability. For example, in the case of horseradish peroxidase, it should be comprised between 0°C and 40°C with a preferred temperature at 35°C. Other enzymes, known as thermophilic, may be used at higher temperatures, typically 40°C to 80°C.

[0059] Many aspects must be carefully considered when designing a cascade. The initiator and mediators must be compatible with the catalysts chosen. Operating conditions such as solution temperature and pH are also paramount. In the case of enzymes, the buffer nature and concentration must also be carefully chosen. In general, the pair of catalysts, enzymatic or not, should show an overlap between their respective activity spaces for the cascade to be enabled. In some settings, solubility in a single solvent, preferably water, is preferrable and the use of co-solvent might be required. Finally, interference generated by minor components of the rubber material, typically curing agents and accelerators, or antioxidants, should be anticipated and addressed.

[0060] The degradation phase may also be conducted in solid phase with or without mechanical agitation. Water may or may not be provided in the form of humidity. Temperature can be maintained between 0 and 80°C. Preferred temperature value may depend on the choice of enzymatic system and conditions of degradation. For example, in the case of laccase and HRP, a preferred temperature is 58°C. Mechanical agitation can be performed continuously or sporadically (i.e., alternating mechanical agitation and resting phases) to promote contact and diffusion between all components of the system. The degradation can be achieved with the target material being in contact with air and initiating agent only. It can also be buried inside various materials which would allow the reaction to proceed, for example soil, or fresh compost, or compost residue. Materials and methods

Peroxide pre-vulcanization of natural rubber

[0061] 0.185 g of iron(ll) pyrophosphate was introduced in a vessel and dissolved in

106.67 g of deionized water, then heated and stirred until complete dissolution. After the solution cooled down to below 40°C, 100 g of natural rubber (based on solid content) was added along with 0.62 g of fructose and 0.411 g of te/Y- butyl hydroperoxide both as solution in 1 .2 g of deionized water. The mixture was brought to 60°C and the reactor’s atmosphere purged with N₂. The reaction was stirred at 60°C for 150 minutes before letting it cool to room temperature. The resulting emulsion was conserved in the fridge until use.

Sulfur pre-vulcanization of natural rubber

[0062] Pre-vulcanization of natural rubber was achieved using the formulation described in Table 1 below and conducted for 1 hour at 50°C followed by 3 hours of maturation at room temperature.

Table 1

Vulcanization of cast films

[0063] On a clean and dry glass plate, a 9 in. x 9 in. square contour was drawn with a glue gun and left to dry. The plate was placed on a drying stand and its horizontality controlled. The pre-vulcanized natural rubber suspension was mixed with deionized water and gently poured onto the plate.

[0064] The plate was left to dry at room temperature overnight. After drying, the natural rubber (NR) sheet was coated with powdered calcium carbonate and removed from the glass plate by removing the glue frame. The film was then soaked in water overnight at room temperature. The NR sheet was then placed between two glass plates and vulcanized for 50°C for 140 minutes.

[0065] After cooling to room temperature, one of the glass plates was removed. The sheet was coated with powdered calcium carbonate and the sheet was removed from the remaining glass plate. The powder remaining on the film was removed under nitrogen current.

Film dipping

[0066] Ceramic formers were dipped in a coagulant bath containing 10% mass solution of calcium nitrate for 20 seconds. The formers were then dried for 20 minutes at 85°C before being cooled to 60°C. The formers with coagulant were then dipped for 10 seconds in a latex dispersion before being dried for 5 minutes at 70°C. The formers with latex film were then leached in warm water (60-65°C) for 5 minutes after which the films were vulcanized at 100°C for 30 minutes. The films were then stripped from the formers.

Stock solutions preparation

[0067] Lignin was suspended in deionized water or chosen buffer to obtain a 3% wt/vol suspension which was sonicated for 20 minutes for homogenization purposes. Solutions of 1 -hydroxybenzotriazole (HOBt) and of linoleic acid at 500 mM in ethanol were prepared. Fresh stock solutions of enzymes were prepared at 1% wt/vol: in sodium oxalate buffer (pH 4.5, 10 mM), in sodium phosphate buffer (pH 7, 10 mM), or in sodium acetate (pH 4.9, 100 mM). A solution of manganese sulfate was also prepared at 200 mM in sodium oxalate buffer (pH 4.5, 10 mM). A solution of Tween 20 5% wt/vol in deionized water was prepared.

Hydrogen peroxide production by laccase in contact with lignin

[0068] The stock solutions above were combined in a vial to obtain 3 mL of a solution with final concentrations described in Table 2 below.

Table 2

Compound Final concentration Lignin 0.33% wt/vol Tween 20 0.5% wt/vol Linoleic acid 50 mM HOBt 50 mM Laccase 0.1% wt/vol

[0069] The mixture was incubated at 35°C and 75 rpm for 24 hours. The generation of hydrogen peroxide was monitored using semi-quantitative colorimetric test strips (Peroxide Test from Supelco).

[0070] In other experiments, laccase or the surfactant and mediators were omitted.

External action of Laccase/MnP system on rubber films

[0071] The stock solutions above were combined in a vial to obtain 1 mL of a solution with final concentrations described in Table 3 below.

Table 3

Compound _ Final concentration

Lignin 1 .2% wt/vol

Manganese sulfate 20 mM

Tween 20 0.5% wt/vol

Linoleic acid 50 mM Laccase 0.1% wt/vol MnP 0.2% wt/vol

[0072] A piece of peroxide-cured cast rubber film was introduced in the vial which was then closed and incubated for 7 days at 35°C and 75 rpm.

External action of free Laccase/HRP system on rubber films [0073] The stock solutions above were combined in a vial to obtain 1 mL of a solution with final concentrations described in Table 4 below.

Table 4

Final concentration

Lignin 1 .2% wt/vol

Tween 20 0.5% wt/vol

Linoleic acid 25 mM

HOBt 25 mM Laccase 0.1% wt/vol

HRP 0.2% wt/vol

[0074] A piece of peroxide cured cast rubber film was introduced in the vial which was then closed and incubated for 7 days at 35°C and 75 rpm.

Action of the laccase/HRP system embedded in prevulcanized rubber films

[0075] 1 mL of peroxide pre-vulcanized rubber emulsion was mixed with 50 pL of

HOBt stock solution, 50 pL of linoleic acid solution, and 50 pL of Tween 20 stock solution and 1 mL of a solution containing 1 mg of laccase and 1 mg of HRP. The mixture was mixed for a short time and then poured on a glass plate and left to dry at room temperature overnight. The resulting films were placed in Petri dishes containing 5 g of humid lignin and incubated for 4 days at 35°C.

[0076] In some experiments, HOBt, linoleic acid, and Tween 20 were omitted. In another, 1 mL of a 3% w/w lignin suspension was added to the mixture containing the pre-vulcanized rubber, enzymes, and mediators. The resulting films were incubated without coating them in lignin.

Action of laccase/HRP system immobilized in starch embedded in rubber films

[0077] 200 mg of starch were suspended in 1.8 g of water and heated at 100°C under strong agitation to form a gel. 2 mL of a solution containing 1 mg of laccase, 1 mg of HRP in sodium oxalate buffer (pH 4.5, 10 mM) was added to the starch solution after it cooled to below 40°C. The mixture was stirred for 10 minutes before being dried in an oven set at 40°C for 3 hours. The resulting solid (6% humidity content) was ground and the powder passed through a 10 pm sieve.

[0078] The fine powder (0.1 g) was then combined with a peroxide pre-vulcanized latex suspension (4 mL) and 50 pL of the HOBt stock solution, 50 pL linoleic acid stock solution, and 50 pL of the Tween 20 stock solution. The mixture was spread on glass plates and left to dry at room temperature overnight. The resulting films were then vulcanized at 50°C for 140 minutes. The films were coated with powdered lignin and incubated for 7 days at 58°C in humid soil.

[0079] In one experiment, 1 mL of a 3% w/w lignin suspension was added to the prevulcanized rubber before the addition of the other components. The mixture was dried, and the resulting films vulcanized in the conditions described above. They were then incubated in humid soil like the other films but without lignin coating.

Role of mediator concentration and buffer on the Laccase/HRP system on sulfur- vulcanized rubber films

[0080] The stock solutions above were combined in a vial to obtain 10 mL of a solution sodium acetate buffer (pH 4.9, 100 mM) with final concentrations described in Table 5 below.

Table 5

Compound Final concentration

Lignin 3.3% wt/vol Tween 20 0.5% wt/vol Linoleic acid 50 mM HOBt 50 mM Laccase 0.1% wt/vol HRP 0.1% wt/vol

[0081] A piece of sulfur-vulcanized dipped or cast rubber film was introduced in the vial which was then closed and incubated for 7 or 14 days at 35°C and 75 rpm.

Action of laccase/HRP system embedded in peroxide-prevulcanized rubber film in compost

[0082] A stock solution containing both laccase and HRP at 1% wt/vol in sodium acetate buffer above was prepared. 20 g of peroxide-prevulcanized rubber latex was weighed to which 50 pL of Tween 20 stock solution was added followed 50 pL of HOBt stock solution and 50 pL of linoleic acid stock solution. 1 mL of the enzyme solution is then added drop-by-drop.

[0083] 10 g of peroxide-prevulcanized rubber mixture was poured into a petri dish and left to dry at 25°C. the resulting film was cut into pieces of around 5x5 mm. 0.5 g of the latex film was combined with 100 g of synthetic composting waste prepared according to IS020200 and the resulting mixture was incubated at 58°C for 7 days.

[0084] In another experiment, the enzymes were omitted.

Action of the laccase/hemin and laccase/humic acid systems on rubber films

[0085] Stock solutions in sodium acetate buffer (pH 4.9, 100 mM) were prepared: 200 mg/mL FeCI₂, 100 mg/mL humic acid, 100 mg/mL lignin, 10 mg/mL laccase. A 10 mM stock solution of hemin in DMSO was also prepared. The stock solutions were combined in a vial in order to obtain 5 mL of a dispersion according to Table 6 below.

Table 6

Compound Laccase/humic acid Laccase/hemin Lignin 0.4% wt/vol 0.4% wt/vol Humic acid 40 mg/mL FeCI₂ 16 mg/mL Hemin 2 mM Laccase 2 mg/mL 2 mg/mL Tween 20 0.1% wt/vol 0.1% wt/vol Linoleic acid 2 mM 2 mM

[0086] A piece of peroxide-cured or sulfur-cured NR film was introduced in the vial which was then closed and incubated for 14 days at 35°C and 100 rpm.

Analysis

[0087] The rubber films were washed with deionized water and dried. Rubber film modifications were studied by FTIR and TGA. The presence of soluble, low molecular weight molecules containing aldehyde function was controlled using a commercial dedicated colorimetric assay. In some embodiments, aldehyde presence was detected qualitatively at the surface of films or in the solution in which they were incubated using Schiff’s reagent. Results

Evidence of hydrogen peroxide generation by laccase in the presence of lignin

[0088] The contact between laccase and lignin is known to generate hydrogen peroxide [14], We found that a solution containing 0.1% wt/vol of laccase from T. versicolor and 0.3% wt/vol lignin was found to generate high concentrations of at least 700 pM within 20 minutes. This concentration remained constant over 24 hours when only laccase is added but declined over time in the presence of the mediators (linoleic acid, HOBt) and surfactant. The decline is however slow and a concentration of around 0.3 mM was still observed after 24 hours. This slow decrease illustrates the necessity of a second catalyst to speed up the activation of hydrogen peroxide and mediators into highly reactive radicals.

Evidence of rubber film degradation by enzyme cascade in solution (peroxide-cured films)

[0089] The capacity of the enzymatic cascade to degrade peroxide-cured rubber films in the presence of lignin was first confirmed. Incubating uncured natural rubber films with a solution containing laccase and HRP (1% wt/vol) for 7 days at 35°C in oxalate buffer at pH 4.5 led to a noticeable loss of physical integrity of the film which turned from a flexible solid to a sticky and easily broken goo. FTIR of the incubated film showed emergence of bands in the 1700 cnr¹ region characteristic of C=O bonds of aldehydes and ketones, to be expected in the radical reactions at play [13], Generation of soluble low molecular weight aldehydes was confirmed using a dedicated colorimetric assay. Thermogravimetric analysis (TGA) also showed alteration of the polymer matrix with the emergence of a peak around 240°C corresponding to the removal of lower molecular weight polymer chains accounting for more than 20% of the mass of the incubated film. Taken together, these results indicate significant degradation of the rubber films and demonstrate the efficacy of the proposed enzymatic cascade in this regard. Activity assays characteristics of laccase and HRP also showed that the enzymes were still active after the incubation period, indicating that further degradation may be expected over longer incubation times.

[0090] A 21-26% mass loss measured by TGA was observed for sulfur-cured NR films -obtained by dipping or casting process, thereby demonstrating that the degradation system is effective regardless of the curing method or film forming technique. The films turned brittle and showed multiple cracks. To achieve this result, the concentration of mediators was increased which could be due to the interference of curing agent still present in the material, the nature of the crosslinking bonds created during curing and also to the presence of an antioxidant in the formulation. Antioxidants are added to NR films to prevent its oxidation over time due to oxygen exposure and extend its shelf life. Antioxidants are designed to capture and inactivate Reactive Oxygen Species (ROS) which are of a similar chemical nature to the radicals generated by the degradation system. The present result demonstrates that the present invention can be applied to rubber materials produced according to industry standards.

[0091] Replacing the second catalyst with non-enzymatic alternatives, like hemin or humic acid combined with iron(ll) chloride also yielded positive results. The presence of aldehydes on rubber surfaces (peroxide-cured and sulfur-cured) was detected with Schiff’s reagent which turns a pinkish purple color in their presence. Soluble aldehydes were also detected in solution, showing that material fragmentation to relatively small molecular weight can be achieved. The films aspect was also affected with loss of elasticity and increased transparency. A mass loss of 5% was observed by TGA. In contrast, no aldehydes could be detected at the surface of untreated films or in solution with the same technique and films retained their integrity. Non-enzymatic catalysts can present a financial advantage compared to enzymes.

[0092] Referring to the figures, Figure 1 is an FTIR spectrum of cured NR film incubated in a solution laccase and HRP for 7 days at 35°C. Figure 2 is an FTIR spectrum of cured NR film incubated in a solution of laccase and MnP for 7 days at 35°C.

[0093] Figure 3 is a TGA of NR films incubated in solutions containing buffer only (top left), laccase and MnP (top right), laccase and HRP (bottom) with mediators and initiator. In contrast, films incubated in the same conditions but without enzymes did not show significant alterations using any of the above characterization techniques. In another experiment, HRP was replaced by MnP, another peroxidase susceptible to utilize H₂O₂ to generate labile radicals which led to 18% mass loss as observed in TGA. This demonstrates that several enzymatic cascades can be designed and used for rubber degradation purposes.

[0094] Figure 4 shows the TGA and physical aspect of sulfur-cured NR film prepared by dipping technique or casting technique exposed to a solution containing laccase and HRP with an increased concentration of mediators in acetate buffer for 1 week at 35°C.

[0095] Figure 5 shows the staining of treated NR films (peroxide- or sulfur-cured) with Schiff’s reagent. The films were exposed to the laccase/hemin or laccase/iron(ll)- humic acid systems at 35°C for 14 days.

Evidence of pre-vulcanized rubber degradation by embedded enzymes

[0096] The efficacy of the enzymatic cascade was further confirmed by the study of enzymes directly embedded in rubber films. For that, enzymes were added to the latex dispersion before it was dried to form a film. The film was then contacted with damp lignin and incubated for 4 days at 35°C. Again, the films lost physical integrity and TGA indicated nearly 7% mass loss to the initial polymer. A similar mass loss (5.3%) was observed when lignin was also embedded to the polymer film, which shows that the initiating polymer can also be provided in situ rather than externally. FTIR shows new intense bands around 1700 cnr¹.

[0097] Again, controls run without enzymes showed no measurable mass loss while the omission of linoleic acid and HOBt led to only 3% mass loss. This demonstrates both the role of enzymes in the generation of the polymer-degrading radicals and the importance of adequate substrates in delivering the radical moieties from enzyme active sites to the polymer.

[0098] Figure 6 represents physical aspect of NR films incubated for 4 days at 35°C. A) Without enzymes; B) with embedded enzymes but without mediators, external lignin; C) with embedded enzymes and mediators, external lignin; D) with embedded enzymes, mediators, and lignin. Figure 7 is an FTIR spectra showing the effect of laccase and HRP embedded inside a NR film incubated for 4 days at 35°C. Lignin was contacted at the surface of the film. Figure 8 is an FTIR spectra showing the effect of laccase and HRP embedded inside a NR film incubated for 4 days at 35°C. Lignin was embedded inside the film. Figure 9 is a TGA of NR films without embedded enzymes (top left), with embedded enzyme and lignin contacted externally (top right), with embedded enzymes and lignin (bottom). Figure 10 represents physical aspect of partially vulcanized NR films with or without the laccase/HRP system and incubated at 58°C in industrial composting conditions according to IS020200. The film on the left contains enzymes and is clearly degraded while the film without enzymes remained intact. Evidence of rubber degradation by enzymes supported by microparticles embedded in the films

[0099] Laccase and HRP were also incorporated inside dry gelatinized starch particles ground to a 10 pm size. The particles were mixed with a suspension prevulcanized latex. The resulting mixture was cured at 50°C for 140 minutes. The resulting film was coated in powdered lignin and incubated in humid soil for 7 days at 58°C. The FTIR spectrum clearly shows a clear increase in absorbance in the 1700 cm-¹ region showing the apparition of new aldehyde and ketone moieties tied to the polymer chains. TGA indicates 5.1% mass loss. Both FTIR and TGA data show that lignin can be provided as a filler inside the rubber film or as an external powder in contact with the film without a significant difference in efficacy.

[00100] Figure 11 is a FTIR spectra of cured NR films with enzyme-loaded starch particles incubated for 7 days at 58°C. Mediators were embedded in the film. Lignin was provided either embedded in the film or as a powder in contact with the film. Figure 12 is a TGA of NR films with incorporated starch particles containing the enzymes. The radical shuttles and lignin were incorporated in the film at the casting step.

[00101] As will be understood by a skilled person, other variations and combinations may be made to the various embodiments of the invention as described herein above.

[00102] The scope of the claims should not be limited by the preferred embodiments set forth herein above; but should be given the broadest interpretation consistent with the description as a whole.

[00103] The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.

REFERENCES:

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2. Ali Shah, A.; Hasan, F.; Shah, Z.; Kanwal, N.; Zeb, S. Biodegradation of Natural and Synthetic Rubbers: A Review. Int. Biodeterior. Biodegrad. 2013, 83, 145-157. https://doi.Org/10.1016/j.ibiod.2013.05.004.

3. Tsuchii, A.; Suzuki, T.; Takeda, K. Microbial Degradation of Natural Rubber

Vulcanizates. Appl. Environ. Microbiol. 1985, 50 (4), 965-970. https://doi.Org/10.1128/aem.50.4.965-970.1985.

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9. Sugano, S.; Kouzai, H. Solid-Liquid Phase Degradation of Vulcanized Rubber Using Lipid Peroxidation. Chem. Lett. 2016, 45 (4), 397-399. https://doi.org/10.1246/cl.151165.

10. Wisetkhamsai, K.; Patthaveekongka, W.; Arayapranee, W. Study on Degradation of Natural Rubber Latex Using Hydrogen Peroxide and Sodium Nitrite in the Presence of Formic Acid. Polymers 2023, 15 (4), 1031. https://d0i.0rg/l 0.3390/polym15041031 .

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Claims

CLAIMS:

1. A method for the degradation of a rubber material, comprising providing a rubber material contacted with catalytic system, wherein the catalytic system is adapted for an in situ production of hydrogen peroxide, and wherein the hydrogen peroxide generates radicals which cause the degradation of the rubber material.

2. The method according to claim 1 , wherein the catalytic system contacts the rubber material externally and/or internally.

3. The method according to claim 1 , wherein the catalytic system is embedded (or incorporated or encapsulated or immobilized) within the rubber material.

4. The method according to any one of claims 1 to 3, wherein the catalytic system is in liquid form, solid form, or a combination thereof.

5. The method according to any one of claims 1 to 4, wherein the catalytic system comprises: a first catalyst, an initiating agent, and a second catalyst; and wherein the first catalyst reacts with the initiating agent to generate the hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to produce the radicals which cause the degradation of the rubber material.

6. The method according to any one of claims 1 to 4, wherein the catalytic system comprises: a first catalyst, an initiating agent, a second catalyst, and a mediator; and wherein the first catalyst reacts with the initiating agent to generate the hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to react with the mediator to produce the radicals which cause the degradation of the rubber material.

7. The method according to claim 5 or 6, wherein the first catalyst comprises any suitable enzymatic and/or non-enzymatic catalyst used in a chemical or biochemical process to generate hydrogen peroxide; preferably the first catalyst comprises: an enzyme selected from the group consisting of: laccases, glucose oxidase, galactose oxidase, glyoxal oxidase, superoxide dismutase, alcohol oxidase, cholesterol oxidase, aryl-alcohol oxidase, oxalate oxidase, mono-amine oxidase, NADPH oxidase, NADH oxidase, lactate oxidase, pyruvate oxidase, D-amino acid oxidase, diamine oxidase, polyamine oxidase, glycolate oxidase, xanthine oxidase, and combinations thereof; and/or an organic molecule selected from the group consisting of: anthraquinone, flavonoids, and combinations thereof; and/or a metal complex selected from the group consisting of: cobalt, copper and manganese complexes, hematite, nickel oxide, cobalt sulfide; and/or a nanomaterial selected from the group consisting of: palladium gold nanoparticles, bismuth titanate nanosheets, metal-organic frameworks, carbon nanotubes, graphene, and combinations thereof.

8. The method according to any one of claims 5 to 7, wherein the initiating agent comprises any molecule or polymer suitable for acting as a substrate for the first catalyst; preferably the initiating agent is selected from the group consisting of: lignin, cellulose, hemicellulose, starch, glucose or other carbohydrate (possibly generated from the hydrolysis of biopolymers), proteins, peptides, oligopeptides, or amino-acids (including those generated by hydrolysis of proteins), humic substances, and combinations thereof; more preferably the initiating agent comprises lignin and/or starch.

9. The method according to claim 5, wherein the second catalyst comprises an enzyme or set of enzymes or metal complex or molecule or polymer suitable for reacting with the hydrogen peroxide to generate the radicals.

10. The method according to claim 6, wherein the second catalyst comprises an enzyme or set of enzymes or metal complex or molecule or polymer suitable for using the hydrogen peroxide to react with the mediator to generate the radicals.

11. The method according to any one of claims 5 to 10, wherein the second catalyst comprises cations and corresponding metal complexes capable of achieving Fenton-type reactions; and/or enzymes which possess other activities than reaction with hydrogen peroxide and which may be described otherwise than peroxidase, including the cytochrome P450 family and other cytochromes; preferably the second catalyst comprises one or more of: iron (II) sulfate, iron (II) oxalate, iron (II) lactate, hemin, iron(ll) and humic acid complex; enzymes of the peroxidase class such as manganese peroxidase (MnP), horseradish peroxidase (HRP), NADH peroxidase, myeloperoxidase, lactoperoxidase, lipid peroxidase, lignin peroxidase, hemoglobin, and cytochrome C; combined enzymes such as glutathione peroxidase and horseradish peroxidase; and combinations thereof; more preferably the second catalyst comprises manganese peroxidase (MnP) and/or horse radish peroxidase (HRP).

12. The method according to claim 6 or 10, wherein the mediator comprises any molecule suitable to be turned into a radical or into a chemical species prone to decompose into radicals by a catalytic system and then promote homolytic bond breaking within a polymer; and/or any suitable molecule known to adopt a stable yet reactive radical form and to ease a radical transfer; preferably the mediator is selected from the group consisting of: linoleic acid; hydroxybenzotriazole (HOBt); unsaturated fatty acids such as oleic acid, palmitoleic acid, linolenic acid, arachidonic acid, and their salts; phenols such as vanillin, para-coumaric acid, syringaldehyde, veratryl alcohol, tyrosine, humin and humic acid, and phenol red; aldehybes such as 2,4-decadienal, 2-butenedial; molecules containing an NOH group such as 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), N-hydroxynaphthalimide, N- hydroxyacetanilide, and N-hydroxymaleimide; thiazolines and thiazines such as 2,2’- azinobis-(3-ethylbenzthiazoline-6-sulphonate (ABTS) and chlorpromazine, violuric acid (VLA); quinones such as anthraquinone and Remazol Brilliant blue, di- and trimethoxybenzenes such as 1 ,4-dimethoxybenzene (DMB) and 2-chloro-1 ,4- dimethoxybenzene (2CI-1 ,4-DMB); flavins; tetrazoles; tetrazolones; and combinations thereof; more preferably the mediator comprises linoleic acid and/or HOBt.

13. The method according to any one of claims 1 to 12, wherein the rubber material is selected from the group consisting of: natural rubber (NR), butyl rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), c/s-isoprene rubber, frans-isoprene rubber, epoxidized rubber, silicon, gutta percha, halobutyl rubber (HBR), nitrile butadiene rubber (NBR), neoprene (polychloroprene), ethylene propylene diene monomer (EDPM), fluoroelastomers including FKMs, and combinations thereof; preferably the rubber material comprises natural rubber (NR).

14. The method according to any one of claims 1 to 13, wherein the rubber material is a blend or a composite material.

15. The method according to any one of claims 1 to 14, wherein the rubber material has undergone a chemical modification; optionally the chemical modification is local or general; optionally the chemical modification is in bulk or at a surface thereof.

16. The method according to any one of claims 1 to 15, wherein the rubber material is prepared by a method selected from the group consisting of: extrusion, injection molding, compression molding, transfer molding, calendaring, dipping, casting, coating, 3D printing, and combinations thereof.

17. The method according to any one of claims 1 to 16, wherein the rubber material is uncured (non-cross linked) or vulcanized (cross linked); optionally vulcanization uses sulfur curing technique or peroxide curing technique.

18. The method according to any one of claims 1 to 17, wherein the rubber material is thermoplastic or a thermoset.

19. The method according to any one of claims 1 to 18, wherein conditions associated with the in situ production of the hydrogen peroxide and the radicals depend on one or more of: temperature, pH, buffer, and humidity; preferably the conditions depend on temperature.

20. A catalytic system for use in the degradation of a rubber material, comprising: a first catalyst, an initiating agent, and a second catalyst, wherein the first catalyst is adapted to react with the initiating agent to generate hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to produce radicals which cause the degradation of the rubber material.

21. A catalytic system for use in the degradation of a rubber material, comprising: a first catalyst, an initiating agent, a second catalyst, and a mediator, wherein the first catalyst is adapted to react with the initiating agent to generate hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to react with the mediator to produce radicals which cause the degradation of the rubber material.

22. A kit for use in the degradation of a rubber material, comprising: a first catalyst, an initiating agent, a second catalyst, and instructions for use, wherein the first catalyst is adapted to react with the initiating agent to generate hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to produce radicals which cause the degradation of the rubber material.

23. A kit for use in the degradation of a rubber material, comprising: a first catalyst, an initiating agent, a second catalyst, a mediator, and instructions for use, wherein the first catalyst is adapted to react with the initiating agent to generate hydrogen peroxide, and the second catalyst uses the hydrogen peroxide to react with the mediator to produce radicals which cause the degradation of the rubber material.

24. A rubber material contacted with the catalytic system as defined in claim 20 or 21 .

25. A waste treatment facility, which embodies the method as defined in any one of claims 1 to 19; preferably the facility is an industrial facility.

26. A facility adapted for producing the catalytic system as defined in claim 20 or 21 ; preferably the facility is an industrial facility.

27. A facility adapted for producing the kit as defined in claim 22 or 23; preferably the facility is an industrial facility.