Method of recycling

Abstract

The present disclosure relates to a method of devulcanizing a vulcanized rubber, the vulcanized rubber comprising cross-linking bonds, wherein the method comprises: contacting the vulcanized rubber with a peroxide reagent in a reaction mixture to provide a devulcanized rubber product, wherein the peroxide reagent comprises: hydrogen peroxide, and a cyclic ether of formula (I). The present disclosure further relates to the use of the peroxide reagent in a method of devulcanizing rubber, and a method of pre-treating a vulcanized rubber to remove or reduce an amount of at least one additive.

Description

[0001] METHOD OF RECYCLING

[0002] FIELD

[0003] The present disclosure relates to a method of devulcanizing a vulcanized rubber, the vulcanized rubber comprising cross-linking bonds, wherein the method comprises: contacting the vulcanized rubber with a peroxide reagent in a reaction mixture to provide a devulcanized rubber product, wherein the peroxide reagent comprises: hydrogen peroxide, and a cyclic ether of formula (I). The present disclosure further relates to the use of the peroxide reagent in a method of devulcanizing rubber, and a method of pre-treating a vulcanized rubber to remove or reduce an amount of at least one additive.

[0004] BACKGROUND

[0005] The global tyre industry generates an immense amount of waste annually, contributing significantly to environmental pollution. The complex chemical structure of rubber, particularly in vulcanized form, makes recycling a formidable challenge. The cross-linked nature of rubber prevents it from being easily melted down and reprocessed, which hampers efforts to establish a circular economy for these materials. The complexity of modern tyres, compounded by additives like sulfur, metals, and other polymers, exacerbates the recycling problem, leading to a large volume of rubber waste being incinerated or landfilled. This inefficiency not only wastes potential resources but also leads to environmental hazards such as leaching of toxic substances and significant fire risks. Despite these challenges, several recycling technologies have been developed, though each has significant drawbacks that limit their effectiveness and environmental sustainability.

[0006] Pyrolysis involves the thermal decomposition of rubber in the absence of oxygen, resulting in three primary products: char, liquid oil (often referred to as tire pyrolysis oil, TPO), and gas. The process has been explored extensively due to its ability to break down complex materials like rubber. However, the high sulfur content in rubber poses a significant challenge, as it leads to the formation of sulfur-containing by-products, which require additional treatment to meet environmental standards. Furthermore, the liquid and gas fractions are often contaminated with sulfur, necessitating costly and complex desulfurization processes. Zeolite catalysts, such as H-ZSM-5 and Pd / H-BEA, have been used to enhance the pyrolysis process by improving the yield of desirable products like light olefins and aromatic compounds. However, these catalysts can be deactivated by coke formation, and their effectiveness is limited by the need for precise temperature control and extensive catalyst regeneration. Microwave pyrolysis offers improved energy efficiency and faster processing times, but it requires thorough removal of metals from the rubber to prevent equipment damage, adding to the complexity and cost. Ultimately, pyrolysis generates a low value product that requires extensive refining for further use.

[0007] 1

[0008] 55812689-2Gasification is a process that converts rubber into syngas (a mixture of hydrogen, carbon monoxide, and methane) by reacting it with limited oxygen or steam. Gasification requires high temperatures, which can lead to the formation of toxic by-products if not carefully controlled. Additionally, the presence of impurities in rubber, such as metals and sulfur, can affect the quality of the syngas and the overall efficiency of the process. Although CO2-assisted gasification has shown promise in improving syngas yield and reducing CO2 emissions, the technology is still in its early stages and requires further development. Ultimately, the rubber is destroyed to yield a low value product.

[0009] Oxidative cleavage uses oxidizing agents, such as ozone or hydrogen peroxide, to break down rubber into smaller, functionalized oligomers. This method allows for the introduction of useful chemical groups, such as aldehydes and ketones, into the degraded products. However, controlling the reaction to prevent over-oxidation is challenging, and the resulting oligomers have limited applications, reducing the economic attractiveness of this approach. Some examples involve the use of hazardous oxidizing agents, which raises environmental and safety concerns, further complicating the adoption of oxidative cleavage on a large scale. Solubility remains an issue as oxidising agents such as hydrogen peroxide and ozone will not permeate the rubber to any significant degree.

[0010] Devulcanization aims to reverse the vulcanization process by breaking the crosslinking bonds, e.g., sulfur bonds that cross-link rubber polymers, and thereby restoring the material's elasticity and making it soluble for further processing. However, this process is technically challenging: the energy required to break sulfur bonds is close to that needed to break carbon bonds in the rubber backbone, making selective bond scission difficult. The reactive sulfur radicals generated during devulcanization can easily reattach to the polymer chains, leading to re-cross-linking and low yields of devulcanized rubber. Various devulcanizing agents, such as diphenyl disulfide and supercritical carbon dioxide, have been used to mitigate these issues, but they often involve hazardous chemicals or require expensive equipment, limiting their practicality.

[0011] Lamy-Mendes etal., (Aerogel Composites Produced from Silica and Recycled Rubber Sols for Thermal Insulation, Materials, 2022, 15(22), 7897; DOI: 10.3390 / ma15227897) reports a method for partly dissolving rubber tires using an ethanolic solution of peracetic acid. Peracetic acid is a hazardous substance, and on the Authorisation and Restriction lists of REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals). Also, the acidic conditions of the reaction are likely to affect the physical properties of the resultant rubber, and lead to an acidic waste stream that requires neutralisation prior to disposal.

[0012] Deepa etal., (Innovative Method of Devulcanizing Waste Rubber from the Automotive Industry, Curr. J. Appl. Sci. Technol., 2024, 43(7), 1-8; DOI: 10.9734 / cjast / 2024 / v43i74401) describe a method of devulcanizing waste rubber using benzoyl peroxide (BPO) as an organic

[0013] 2

[0014] 55812689-2peroxide and toluene as a solvent. A disadvantage of this system is that toluene is a toxic solvent facing increasing usage restrictions and is typically sourced from the petrochemical industry. Furthermore, at the end of the process, the organic peroxide will give quantitative amounts of organic by-products and increased waste.

[0015] There is a need in the art for alternative devulcanization processes, in particular processes that: are more efficient and / or selective; allow for the recovery of additives and other materials present in vulcanized rubber; yield high-value products; utilise less hazardous or toxic reagents (such that the reagents are not necessarily subject to strict regulatory requirements) and / or reagents that may be sourced from green or otherwise renewable resources; and result in fewer or no hazardous or toxic by-products.

[0016] SUMMARY

[0017] The present invention provides a novel method of devulcanizing a vulcanized rubber. In particular, the present inventors have found that a devulcanized rubber is provided from contacting a vulcanized rubber with a peroxide reagent comprising hydrogen peroxide and a cyclic ether of formula (I). Notably, the peroxide reagent is, without being bound by theory, selective for devulcanization reactions (i.e. , the breaking of cross-linking bonds) rather than the reduction of unsaturation in the backbone of the vulcanized rubber polymer chain. The retained unsaturation means that the resultant devulcanized rubber product is more amenable for re-use and / or further processing. Furthermore, the peroxide reagent is non-aqueous, affordable to produce, green (that is, environmentally friendly: low hazard, low / non-hazardous waste from use, and may be produced from renewable feedstocks), stable, and safe, resulting in devulcanization process that is greener and safer than processes known in the art. Without being bound by theory, the inventors believe that the novel method is effective at least in part due to the ability of the cyclic ether present in the peroxide reagent to ‘swell’ (i.e., increase the volume of) the vulcanized rubber, allowing the hydrogen peroxide (possibly as a solute of, or as a complex with, the cyclic ether) to obtain thorough penetration of the vulcanized rubber.

[0018] Therefore, viewed from a first aspect, there is provided a method of devulcanizing a vulcanized rubber, the vulcanized rubber comprising cross-linking bonds, wherein the method comprises:

[0019] contacting the vulcanized rubber with a peroxide reagent in a reaction mixture to provide a devulcanized rubber product;

[0020] wherein the peroxide reagent comprises:

[0021] (a) hydrogen peroxide; and

[0022] (b) a cyclic ether;

[0023] 3

[0024] 55812689-2wherein the cyclic ether is of formula (I):

[0025]

[0026] wherein:

[0027] R1, R2, R3, and R4are each independently selected from Ci-4alkyl and Ci.4haloalkyl; X and Y are each independently -CR5R6-;

[0028] each R5and R6is independently selected from H, Ci-4alkyl, halo, and Ci.4haloalkyl; and

[0029] n is 0, 1, 2 or 3.

[0030] Additionally, viewed from a second aspect, there is provided the use of a peroxide reagent in a method of devulcanizing a vulcanized rubber, wherein the peroxide reagent is as defined in the first aspect of the invention.

[0031] Furthermore, the present inventors have found that additives present in vulcanized rubber may be extracted from the vulcanized rubber, optionally prior to subjecting it to the devulcanization process, in view of removing or reducing the amount of the additive in the vulcanized rubber prior to devulcanization. The inventors have found that this can be achieved by contacting the vulcanized rubber with a cyclic ether of formula (I), optionally with a peroxide reagent as defined above. This ‘pre-treatment’ process has been found to enable a more efficient subsequent devulcanization process as (without being bound by theory) a pre-treated vulcanized rubber has less additives that may otherwise consume (i.e. , react with) some of the peroxide reagent that would otherwise react with the cross-linking bonds. Additionally, this pre-treatment process may have a utility independent of a devulcanization process, as it can provide a useful method to extract valuable additives from a vulcanized rubber. Thus, whilst it is typically referred to herein as a “pre-treatment” process, it will be appreciated that this method may be employed as a standalone method for extracting at least one additive from a vulcanized rubber. In such examples, the method may be simply considered as a further treatment method rather than a pre-treatment method. Accordingly, the terms “treating” and “pre-treating”, and “treatment” and “pre-treatment” may be used interchangeably.

[0032] Therefore, viewed from a third aspect, there is provided a method of treating or pretreating a vulcanized rubber to remove or reduce an amount of at least one additive, comprising:

[0033] (i) contacting the vulcanized rubber with a cyclic ether such that the at least one additive is extracted (e.g., dissolved) into the cyclic ether to provide a cyclic ether extract; and

[0034] 4

[0035] 55812689-2(ii) separating the cyclic ether extract from the vulcanized rubber;

[0036] wherein the cyclic ether is as defined in the first aspect.

[0037] In some embodiments, the cyclic ether may be comprised in the peroxide reagent as described herein.

[0038] Additionally, the invention also extends to devulcanized rubber products obtainable or obtained by the methods disclosed herein. Therefore, viewed from a fourth aspect, there is provided a devulcanized rubber product obtainable by the method of the first aspect.

[0039] BRIEF DESCRIPTION OF THE FIGURES FIG. 1: Results from Experiment I: (A) Infra-red (IR) absorption spectrum of a cyclic ether, TMO (2,2,5,5-tetramethyloxolane); (B) IR absorption spectrum of a peroxide reagent, “TMO2” (where the cyclic ether is TMO, the peroxide reagent may be referred to as TMO2);

[0040] (C) IR absorption spectrum of hydrogen peroxide (H2O2, aq.).

[0041] FIG. 2: Results from Experiment II: (A) IR absorption spectrum of starting material 1A; (B) IR absorption spectrum of product 3A; (C) STA analysis (simultaneous thermal analysis, comprising differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis) of starting material 1A; (D) STA analysis of product 3A.

[0042] FIG. 3: Results from Experiment III: (A) IR absorption spectrum of product 3B; (B) STA analysis of product 3B.

[0043] FIG. 4: Results from Experiment IV: (A) IR absorption spectrum of starting material 1B; (B) IR absorption spectrum of product 3C; (C) STA analysis of starting material 1B; (D) STA analysis of product 3C.

[0044] FIG. 5: Results from Experiment V: (A) IR absorption spectrum of product 3D; (B) STA analysis of product 3D.

[0045] FIG. 6: Results from Experiment VI: (A) IR absorption spectrum of starting material 10; (B) IR absorption spectrum of product 3E; (C) STA analysis of starting material 10; (D) STA analysis of product 3E.

[0046] FIG. 7: Results from Experiment VII: (A) IR absorption spectrum of starting material 1G2; (B) IR absorption spectrum of product 3F; (C) STA analysis of starting material 1G2; (D) STA analysis of product 3F.

[0047] FIG. 8: Results from Experiment VIII: IR absorption spectrum of product 3G.

[0048] FIG. 9: Results from Experiment IX: IR absorption spectrum of product 3H.

[0049] FIG. 10: Results from Experiment X: IR absorption spectrum of product 3I.

[0050] FIG. 11 : Results from Experiments XII and XIII: (A) I R absorption spectrum of extracts from Experiment Xlla; (B) IR absorption spectrum of extracts from Experiment Xllla; (C) overlap of IP absorption spectra of extracts from Experiments Xlla and Xllla.

[0051] 5

[0052] 55812689-2DETAILED DESCRIPTION

[0053] Definitions

[0054] In the discussion that follows, reference is made to a number of terms, which have the meanings provided below, unless a context indicates to the contrary. The nomenclature used herein for defining compounds, in particular the compounds according to the invention, is in general based on the rules of the IUPAC organisation for chemical compounds, specifically the “IUPAC Compendium of Chemical Terminology (Gold Book)”. For the avoidance of doubt, if a rule of the IUPAC organisation is in conflict with a definition provided herein, the definition herein is to prevail. Furthermore, if a compound structure is in conflict with the name provided for the structure, the structure is to prevail.

[0055] The term “comprising” or variants thereof is to be understood herein to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0056] The term “consisting” or variants thereof is to be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, and the exclusion of any other element, integer or step or group of elements, integers or steps.

[0057] The disclosure also encompasses various deuterated forms of the compounds as described herein. Each available hydrogen atom attached to a carbon atom may be independently replaced with a deuterium atom. A person of ordinary skill in the art will know how to synthesize deuterated forms of the compounds disclosed herein, including those referred to above. For example, deuterated materials, such as alkyl groups may be prepared by conventional techniques (see for example: methyl-d3 -amine available from Aldrich Chemical Co., Milwaukee, Wl, Cat. No.489, 689-2).

[0058] The disclosure also includes isotopical ly labelled compounds of the present disclosure, but for the fact that one or more atoms are replaced by an atom having an atomic mass or mass number different from the atomic mass or mass number most commonly found in nature. Examples of isotopes that can be incorporated into compounds of the disclosure include isotopes of hydrogen, carbon, nitrogen, oxygen, fluorine, iodine and chlorine such as3H,11C,14C,18F,123l or125l. Compounds of the present disclosure and pharmaceutically acceptable salts of said compounds that contain the aforementioned isotopes and / or other isotopes of other atoms are within the scope of the present disclosure.

[0059] The term “about” herein, when qualifying a number or value, is used to refer to values that lie within ± 5% of the value specified. For example, where a concentration range is defined as from about 0.05% to about 25% w / w, concentrations of 0.0475% and 26.25% w / w are considered to be included.

[0060] 6

[0061] 55812689-2The term “alkyl” defines univalent groups derived from alkanes by removal of a hydrogen atom from any carbon atom, wherein the term “alkane” is intended to define acyclic branched or unbranched hydrocarbons having the general formula CnH2n+2, wherein n is an integer >1. Alkyl groups may be Ci-4alkyl groups. Ci-4alkyl refers to any selected from the group consisting of methyl, ethyl, n-propyl, / so-propyl, n-butyl, sec-butyl, / so-butyl and tertbutyl.

[0062] The term “halo” refers to a monovalent halogen radical such as fluoro, chloro, bromo, and iodo.

[0063] The term “haloalkyl” refers to univalent groups derived from alkyl groups wherein one or more hydrogen atoms has been replaced with a halo group. The halo group may be independently selected from fluoro, chloro, bromo, and iodo. Haloalkyl groups may be Ci-4haloalkyl groups. Ci.4haloalkyl refers but is not limited to fluoromethyl, difluoromethyl, trifluoromethyl, 2-fluoroethyl, 2,2,2-trifluoroethyl, perfluoroethyl, hexafluoroisopropyl, chloromethyl, 2-chloroethyl, 3-chloropropyl, and 4-chlorobutyl.

[0064] Methods

[0065] As described above, in a first aspect there is provided a method of devulcanizing a vulcanized rubber, the vulcanized rubber comprising cross-linking bonds, wherein the method comprises:

[0066] contacting the vulcanized rubber with a peroxide reagent in a reaction mixture to provide a devulcanized rubber product;

[0067] wherein the peroxide reagent comprises:

[0068] (a) hydrogen peroxide; and

[0069] (b) a cyclic ether;

[0070] wherein the cyclic ether is of formula (I):

[0071]

[0072] wherein:

[0073] R1, R2, R3, and R4are each independently selected from Ci-4alkyl and Ci.4haloalkyl; X and Y are each independently -CR5R6-;

[0074] each R5and R6is independently selected from H, Ci-4alkyl, halo, and Ci.4haloalkyl; and

[0075] n is 0, 1, 2 or 3.

[0076] 7

[0077] 55812689-2For the avoidance of doubt, whilst the present invention is directed to methods of devulcanization, the invention also extends to devulcanized rubber products obtainable or obtained by the methods disclosed herein. The following methods may confer on the resultant devulcanized rubber product a particular composition or structure.

[0078] As used herein, a peroxide reagent is a chemical reagent that may be used as a source of hydrogen peroxide (“peroxide”, or H2O2). The peroxide reagent of the first aspect of the invention comprises hydrogen peroxide and a cyclic ether of formula (I). In some embodiments, the peroxide reagent consists of, or consists essentially of, hydrogen peroxide and the cyclic ether.

[0079] The peroxide reagent may take any suitable form that allows it to be prepared, stored, and / or used. In some embodiments, the peroxide reagent may take the form of a composition, mixture, solution, or dispersion. In some embodiments, the peroxide reagent is a composition comprising hydrogen peroxide and the cyclic ether. In some embodiments, the peroxide reagent is a mixture of hydrogen peroxide and the cyclic ether. In some embodiments, the peroxide reagent is a solution of hydrogen peroxide in the cyclic ether; that is, the hydrogen peroxide is dissolved in the cyclic ether. In some embodiments, the peroxide reagent is a dispersion of hydrogen peroxide in the cyclic ether. As described above and herein, and without being bound by theory, the peroxide reagent is or may comprise a complex of hydrogen peroxide and the cyclic ether that forms upon contacting the hydrogen peroxide and the cyclic ether. Thus, the peroxide reagent in any of the forms described herein (e.g., a composition, mixture, solution or dispersion) may comprise a complex of hydrogen peroxide and the cyclic ether.

[0080] As stated above, R1, R2, R3, and R4are each independently selected from Ci-4alkyl and Ci-4haloalkyl. In some embodiments, R1, R2, R3, and R4are each independently selected from Ci-4alkyl, fluoromethyl, difluoromethyl, trifluoromethyl, 2-fluoroethyl, 2,2,2-trifluoroethyl, and perfluoroethyl. In some embodiments, R1, R2, R3, and R4are each independently selected from Ci-4alkyl, fluoromethyl, difluoromethyl, and trifluoromethyl. In some embodiments, R1, R2, R3, and R4are each independently selected from methyl, ethyl, and trifluoromethyl. In more preferred embodiments, R1, R2, R3, and R4are each independently Ci-4alkyl. Typically, R1, R2, R3, and R4are each independently selected from methyl and ethyl. Even more typically R1, R2, R3, and R4are each methyl.

[0081] In some embodiments, R1and R2are the same, for example, R1and R2are methyl. In some embodiments, R3and R4are the same, for example, R3and R4are methyl. Typically, R1, R2, R3, and R4are all the same, for example, R1, R2, R3, and R4are all methyl.

[0082] As described above, X and Y are each independently -CR5R6-, wherein each R5and R6is independently selected from H, Ci-4alkyl, halo, and Ci-4haloalkyl. That is to say, X and Y

[0083] 8

[0084] 55812689-2are each independently a methylene group optionally substituted with one or more groups selected from H, Ci-4alkyl, halo, and Ci.4haloalkyl.

[0085] In some embodiments, each R5and R6is independently selected from H, Ci-4alkyl, fluoro, chloro, fluoromethyl, difluoromethyl, trifluoromethyl, 2-fluoroethyl, 2,2,2-trifluoroethyl, perfluoroethyl, hexafluoroisopropyl, chloromethyl, 2-chloroethyl, 3-chloropropyl, and 4-chlorobutyl. In some embodiments, each R5and R6is independently selected from H, Ci-4alkyl, fluoro, chloro, fluoromethyl, difluoromethyl, and trifluoromethyl. In some embodiments, each R5and R6is independently selected from H, methyl, ethyl, n-propyl, / so-propyl, fluoro, and trifluoromethyl. In some embodiments, each R5and R6is independently selected from H, methyl, ethyl, fluoro, difluoromethyl, trifluoromethyl and perfluoroethyl. In more preferred embodiments, each R5and R6is independently selected from H and Ci-4alkyl, such as methyl, ethyl, n-propyl, / so-propyl, and n-butyl. Typically, each R5and R6is independently selected from H, methyl, and ethyl, more typically H. In some embodiments, each R5and R6is the same; typically, each R5and R6is H.

[0086] As stated above, n is 0, 1, 2 or 3. In other words, the cyclic ether may comprise a 4- to 7- membered ring. In some embodiments, n is 1, 2, or 3. In more preferred embodiments, n is 1 or 2. Typically, n is 1. For the avoidance of doubt, where n is greater than 1, each Y is independent; that is, each R5and R6is selected independently.

[0087] In some embodiments, the cyclic ether is a cyclic ethereal solvent. That is to say, the cyclic ether is a compound with an ether functional group comprised within a ring system, and the compound has solvent-like properties, for example: the compound is a liquid at room temperature. The skilled person will be familiar with or will be able to identify compounds that satisfy these criteria.

[0088] In some embodiments, the cyclic ether is selected from formulae (la) to (Id):

[0089]

[0090] The cyclic ether of formula (la) may be referred to as 2,2,5,5-tetramethyltetrahydrofuran (TMTHF), or simply tetramethyloxolane (TMO); formula (lb) as 2,2,6,6-tetramethyltetrahydropyran; formula (Ic) as 2,2,4,4-tetramethyloxetane; and formula (Id) as 2,2,7,7-tetramethyloxepane. In more preferred embodiments, the cyclic ether is selected from formulae (la) and (lb), more typically (la).

[0091] The cyclic ethers disclosed herein may be obtained commercially or prepared through conventional laboratory synthesis; the skilled person will be familiar with the conventional organic chemistry reactions that may be utilised to synthesise said cyclic ethers. One method

[0092] 9

[0093] 55812689-2of making TMO (formula (la)) is described in WO 2018 / 033635 A1, the contents of which are incorporated herein by reference. The method is a condensation reaction of a diol in the presence of a p-zeolite catalyst. For the avoidance of doubt, this method, and others also suitable for the synthesis of TMO, may be suitable for many other cyclic ethers of formula (I). The precursor diol for the synthesis of TMO described in WO 2018 / 033635 A1 may be synthesised from acetone and acetylene, which may be obtained from renewable or sustainable feedstocks. Thus, in some embodiments, the cyclic ether is obtainable from renewable or sustainable feedstocks. The synthesis of the cyclic ether of formula (lb) is described in Singh et al., Amberlyst-15-Catalyzed Efficient Cyclization of y- and 6-Unsaturated Alcohols: Green Synthesis of Oxygen Heterocycles, Synthetic Communications, 2010, 40, 74, and involves the acid catalysed cyclisation of a linear alcohol comprising an alkene. Specifically, the precursor alcohol for the described synthesis of the cyclic ether of formula (lb) is 2,6-dimethyl-5-hepten-2-ol. This method may be suitable for many other cyclic ethers of formula (I). Additionally, the synthesis of oxetane derivatives such as cyclic ethers of formula (Ic) are described in Mill and Montorsi, The Liquid-Phase Oxidation of 2,4-Dimethylpentane, International Journal of Chemical Kinetics, 1973, V, 119, which may also be applicable to other cyclic ethers of formula (I).

[0094] Where the peroxide reagent comprises a cyclic ether of formula (la), the resultant peroxide reagent is referred to herein as “TMO2”.

[0095] As will be appreciated by one of skill in the art, the peroxide reagent may be prepared in a range of concentrations and / or the desired concentration of the hydrogen peroxide in the peroxide reagent to be used in a particular application may vary depending on a number of factors (such as rate of reaction and ease of handling). For example, in some cases, a higher concentration of hydrogen peroxide may be desirable to provide an increased rate of reaction. In other examples, a lower concentration of hydrogen peroxide may be desirable, e.g. to facilitate safer handling of the reagent.

[0096] In some embodiments, the concentration of hydrogen peroxide in the peroxide reagent is from about 0.01% to about 90% w / w (percentage by weight, or wt. %, or mass fraction). In some embodiments, the concentration of hydrogen peroxide in the peroxide reagent is from about 0.05% to about 50% w / w (percentage by weight, or wt. %, or mass fraction). In some embodiments, the concentration of hydrogen peroxide in the peroxide reagent is from about 0.05% to about 25% w / w. In some embodiments, the concentration is from about 0.5% to about 10% w / w, typically from about 1% to about 5% w / w, more typically from about 2% to about 4% w / w, often about 3% w / w.

[0097] Where the peroxide reagent has been prepared in a particular concentration, the concentration of hydrogen peroxide may be increased by selective removal of the cyclic ether (e.g. under reduced pressure or the like).

[0098] 10

[0099] 55812689-2The concentration of hydrogen peroxide in the peroxide reagent may be quantified through some analytical means. This may be performed spectroscopically, or through “wet” methods such as titration. For example, titration may be performed with potassium permanganate (KMnC ) to determine a concentration of hydrogen peroxide in the peroxide reagent.

[0100] In some embodiments, the density of the peroxide reagent is from about 0.5 to about 1.0 g / mL. In some embodiments, the density is from about 0.6 to about 0.9 g / mL, typically from about 0.7 to about 0.8 g / mL, often about 0.75 g / mL. The densities as described herein may be determined under ambient conditions, for example under standard temperature and pressure.

[0101] The peroxide reagent may be characterised through spectroscopic means. For example, the infrared (IR) absorption spectrum of the peroxide reagent can be recorded. The IR spectrum may be obtained through any suitable instrument; the skilled person will be familiar with obtaining such spectra. In some embodiments, the peroxide reagent has an absorbance peak from about 3250 to about 3450 cm-1. This peak is typically due to an O-H stretching vibration, representative of hydrogen peroxide. The peak may be broad and traverse a wide range of wavenumbers. In some embodiments, the peroxide reagent has an IR absorbance peak from about 3300 to about 3400 cm-1, typically from about 3320 to about 3360 cm-1, more typically about 3330 to about 3350 cm-1, often about 3340 cm-1(e.g., about 3342 cm-1). Additionally, the peroxide reagent may have an IR absorption peak due to a C-H stretching vibration, representative of an aliphatic C-H bond of the cyclic ether. Therefore, in some embodiments, the peroxide reagent has an IR absorbance peak at about 3000 cm-1, typically about 2970 cm-1. The C-H stretching peak is typically sharp and not spread over a wide range of wavenumbers.

[0102] One particularly advantageous feature of the presently disclosed peroxide reagent is that it is anhydrous, i.e., it is substantially free from water. Thus, in some embodiments, the peroxide reagent is anhydrous. The term anhydrous may indicate a water content of <5 wt% water, or <1 wt%, or <0.1 wt%, or <0.01 wt%, or <0.001 wt%. Ideally, the peroxide reagent contains no water. Water content may be represented as wt% or ppm. 5 wt% is equivalent to 50,000 ppm; 1 wt% is 10,000 ppm; 0.1 wt% is 1,000 ppm; 0.01 wt% is 100 ppm; 0.001 wt% is 10 ppm.

[0103] The peroxide reagent may be stable. In some embodiments, the peroxide reagent may be stable for a prolonged period of time when stored at room temperature (e.g., about 20 to about 25 °C), or when stored under refrigerated conditions (e.g., from about 2 to about 8 °C, such as about 4 °C). In some embodiments, the peroxide reagent may be stable for a prolonged period of time even when stored under direct light.

[0104] 11

[0105] 55812689-2In some embodiments, the peroxide reagent may be stable such that the concentration of hydrogen peroxide remains relatively constant over a period of time. In some embodiments, the concentration of the hydrogen peroxide may be at least about 70%, or at least about 80% of an initial concentration after storage for a period of time. The period of time may be at least 1 week, 2 weeks, 3 weeks or 4 weeks. By way of further example, in some embodiments, the concentration of the hydrogen peroxide may be at least about 80% of an initial concentration after storage at room temperature for a period of 4 weeks.

[0106] As described above, in some embodiments the peroxide reagent is a complex of hydrogen peroxide and a cyclic ether of formula (I). The term “complex” is used herein to refer to a stable association between two or more molecules through non-covalent intermolecular interactions, such as hydrogen bonding. Without being bound by theory, in some embodiments, the complex comprises a hydrogen bond between the oxygen atom of the cyclic ether and a hydrogen atom of hydrogen peroxide. Accordingly, the complex may comprise hydrogen peroxide complexed to the cyclic ether by way of a hydrogen bond between the oxygen atom of the cyclic ether and a hydrogen atom of hydrogen peroxide.

[0107] In some embodiments, the hydrogen peroxide is complexed to two molecules of the cyclic ether. In some embodiments, the stoichiometry of the hydrogen peroxide to the cyclic ether is 1:1. In some embodiments, the stoichiometry is 1:2.

[0108] As stated above, the peroxide reagents described herein may comprise such complexes (which may form spontaneously when hydrogen peroxide and the cyclic ethers are contacted with one another). Thus, in some embodiments, the method may comprise contacting the vulcanized rubber with a complex as described herein, e.g. a complex of hydrogen peroxide and a cyclic ether of formula (I).

[0109] As stated above, the method comprises contacting the vulcanized rubber with a peroxide reagent to provide a devulcanized rubber product. The term “contacting” is used herein to refer to any one or more of the acts of combining, such as reacting, mixing, stirring, slurrying, blending, dissolving, impregnating, incubating, passing over, flowing over, or otherwise, in any order, and for any length of time; the skilled person will recognise that the invention is not limited as such.

[0110] In some embodiments, the contacting comprises heating the reaction mixture to a temperature sufficient to induce devulcanization. In some embodiments, the contacting comprises heating the reaction mixture to a temperature sufficient such that the vulcanized rubber is substantially devulcanized (particular embodiments as to the definition of devulcanized are provided below, for example, such that the resultant devulcanized rubber product is substantially soluble in an organic solvent (e.g. at least about 95% soluble), such as a cyclic ether of formula (I)) after 24 hours of contacting at that temperature.

[0111] 12

[0112] 55812689-2In some embodiments, the contacting comprises heating the reaction mixture to, or under, reflux (e.g., the boiling point of the peroxide reagent, or the boiling point of the cyclic ether).

[0113] Additionally or alternatively, the contacting comprises heating the reaction mixture to from about 50 °C to about 120°C, or from about 55 °C to about 115°C. In some embodiments, the contacting comprises heating the reaction mixture from about 60 °C to about 112 °C. Typically, the contacting comprises heating the reaction mixture at a temperature of at least about 60 °C or 70 °C. In some embodiments, the contacting comprises heating the reaction mixture from about 70 °C to about 112 °C. Typically, the above temperatures refer to the internal temperature of the reaction mixture, although, on some occasions, the temperatures may refer to the temperatures of external heating elements.

[0114] The skilled person will recognise that the reaction conditions i.e. temperature at which devulcanization will begin to occur (e.g. at a desired rate) will depend on other variables such as the nature of the vulcanized rubber, the nature of the peroxide reagent, and the pressure that the process is conducted at. The temperature ranges defined above in relation to the contacting step may be applicable under standard pressure conditions. As used herein, standard pressure may refer to a pressure of about 101.325 kPa (1 atm). The skilled person will recognise that the temperature ranges may be adapted where the contacting takes place under different pressure conditions.

[0115] The term “reaction mixture” used herein is intended to refer broadly to the mixture of the peroxide reagent and the vulcanized rubber, optionally alongside any additives, byproducts, solvents, catalysts, additional reagents, products and the like that may otherwise be in contact with the peroxide reagent and the vulcanized rubber during the method of devulcanizing the vulcanized rubber.

[0116] In some embodiments, the contacting is carried out under an inert atmosphere (e.g., under an atmosphere of nitrogen or argon gas) and / or the contacting is carried out anhydrous conditions. An inert atmosphere is understood to refer to reaction conditions whereby the reaction occurs under a closed system substantially free from air (i.e., oxygen and water vapour), typically achieved through the replacement of air with an inert gas such as nitrogen or agon gas. Anhydrous conditions are understood to refer to reaction conditions whereby the reaction occurs in a system substantially free from water. The term anhydrous may indicate a water content in the reaction mixture of <5 wt% water, or <1 wt%, or <0.1 wt%, or <0.01 wt%, or <0.001 wt%. Water content may be represented as wt% or ppm. 5 wt% is equivalent to 50,000 ppm; 1 wt% is 10,000 ppm; 0.1 wt% is 1,000 ppm; 0.01 wt% is 100 ppm; 0.001 wt% is 10 ppm. The contacting is not necessarily limited to an inert atmosphere and / or anhydrous conditions. Indeed, in some embodiments, the reaction is carried out substantially in the presence of air and / or water.

[0117] 13

[0118] 55812689-2In some embodiments, the method further comprises contacting the vulcanized rubber with a catalyst. In other words, a catalyst may be present in the reaction mixture. In some embodiments, the catalyst is a Lewis acid catalyst that is, the catalyst acts as an electron-pair acceptor to (without being bound by theory) increase the reactivity of the vulcanized rubber to the peroxide reagent.

[0119] Suitable Lewis acid catalysts may be based on main group elements such as aluminium, boron, silicon and tin, as well as d-block metals, and the catalysts may comprise salts of these elements / metals. Representative examples include, but are not limited to, oxides, halides, alkoxides, triflates, nitrates, and the like. In some embodiments, the Lewis acid catalyst is selected from molybdenum trioxide (MoOs), isopropoxide salts (such as titanium tetraisopropoxide (Ti(i-PrO)4), boron triisopropoxide (B(i-PrO)s), and aluminium triisopropoxide (Al(i-PrO)s)), aluminium chloride (AlCh), boron trifluoride (BF3), titanium tetrachloride (TiCL), iron trichloride (FeCh), diethylaluminium chloride (Et2AICI), triethylaluminium (EtsAI), titanium dioxide (TiC>2), zirconium dioxide (ZrC>2), lanthanum triflate (La(OTf)s), ytterbium triflate (Yb(OTf)3), silver nitrate (AgNOs), gold chloride (AuCh), palladium chloride (PdCh), tungsten trioxide (WO3), sodium tungstate dihydrate (Na2O4W*2H2O), lithium tungstate (U2WO4), tungsten dichloride dioxide (WCI2O2), and sodium tungstate (Na2O4W). In some embodiments, the Lewis acid catalyst is selected from molybdenum trioxide (MoOs), and isopropoxide salts (such as titanium tetraisopropoxide (Ti(i-PrO)4), boron triisopropoxide (also known as triisopropyl borate, B(i-PrO)s), and aluminium triisopropoxide (Al(i-PrO)s)), typically molybdenum trioxide, titanium tetraisopropoxide, and boron triisopropoxide. Therefore, in some embodiments where the catalyst is a Lewis acid catalyst, the catalyst is selected from molybdenum trioxide, titanium tetraisopropoxide, boron triisopropoxide, and sodium tungstate.

[0120] In some embodiments, the weight ratio of the peroxide reagent to the vulcanized rubber (peroxide reagent : vulcanized rubber) is in the range of from about 0.01:1 to about 100:1, from about 0.01:1 to about 90:1, from about 0.01:1 to about to 80:1, from about 0.01:1 to about 75: 1 , from about 0.01:1 to about 70: 1 , from about 0.01:1 to about 60: 1 , from about 0.01:1 to about 50:1, from about 0.05:1 to about 50:1, from about 0.1:1 to about 50:1, from about 0.1:1 to about 40: 1 , from about 0.1:1 to about 30: 1 , from about 0.1:1 to about 25: 1 , from about 0.1:1 to about 20: 1 , from about 0.1:1 to about 10:1, from about 0.15:1 to about 10:1, from about 0.2:1 to about 10:1, from about 0.2:1 to about 7.5:1, from about 0.2:1 to about 5:1, from about 0.2:1 to about 2.5:1, from about 0.2:1 to about 2:1, from about 0.25:1 to about 2:1, from about 0.25:1 to about 1:1, or from about 0.25:1 to about 0.5:1. In some embodiments, the weight ratio of the peroxide reagent to the vulcanized rubber (peroxide reagent : vulcanized rubber) is in the range of from about 0.01:1 to about 100:1, from about 0.1:1 to about 50:1, from about 0.2:1 to about 10:1, or from about 0.25:1 to about 2:1. In some embodiments, the

[0121] 14

[0122] 55812689-2weight ratio of the peroxide reagent to the vulcanized rubber (peroxide reagent : vulcanized rubber) is about 0.25: 1 or about 0.5:1.

[0123] Vulcanization typically refers to a process whereby a rubber polymer is reacted at high temperature with a sulfur species to create cross-linking bonds. These cross-linking bonds alter the properties of the rubber polymer - now referred to as a vulcanized rubber - often such that the rubber is strong and rigid. A vulcanized rubber typically comprises cross-linking bonds between polymer chains, sometimes in an intrachain or interchain fashion, or combinations thereof. A cross-link between chains (or between different parts of one chain) typically comprises multiple cross-linking bonds, e.g., a cross-link may be a sulfide bridge that connects the chains through one S atom, connected to each chain through C-S bonds. By way of further example, a cross-link may comprise two or more S atoms (such as a ‘disulfide bridge’, “trisulfide bridge”, “tetrasulfide bridge”, etc), such that it comprises C-S and S-S bonds. Without being bound by theory, it is thought that the most reactive sites on a rubber polymer chain for vulcanization, and hence for the cross-linking bonds to form, is at allyl and vinyl sites. An allyl site is an sp3-hybridised carbon atom in an a position to a C=C double bond; a vinyl site is directly connected to an sp2-hybridised carbon atom comprised within in a C=C double bond. Resultant cross-linking bonds may therefore originate on a chain from both sp3- and sp2-hybridised carbon atoms.

[0124] As described above, devulcanization aims to reverse the vulcanization process by breaking the cross-linking bonds, e.g., breaking the C-S and / or S-S bonds that cross-link the chains. Therefore, in some embodiments, the cross-linking bonds are selected from S-S and C-S bonds.

[0125] In some embodiments, the method may facilitate or allow the resultant devulcanized rubber product to be isolated or separated from the vulcanized rubber and / or one or more other components remaining in the reaction. The ability to isolate and / or separate the devulcanized rubber product is useful in allowing it to be more easily reused, recycled and / or reprocessed e.g. as a valuable product in its own right. Additionally, the isolation or separation of this component of the reaction mixture can facilitate the re-use or recycling of one or more other components present in the vulcanized rubber. Therefore, in some embodiments, the method further comprises separating and / or isolating the devulcanized rubber product from the vulcanized rubber and / or from one or more other components present in the vulcanized rubber (such as additives, pigments, textiles, metal and the like). In some embodiments, the one or more other components may be selected from metal (e.g. metal wire), textiles, and pigments (e.g. carbon black).

[0126] The separating and / or isolating may be carried out using any suitable separation and / or extraction techniques as known in the art. Representative examples include filtration, centrifugation, solvent extraction, drying techniques and the like.

[0127] 15

[0128] 55812689-2Filtering may separate any components insoluble in the reaction mixture (e.g., insoluble in the peroxide reagent of the cyclic ether) from any components dissolved in the reaction mixture. In particular, the present inventors have observed that the devulcanized rubber product may be soluble in the reaction mixture (in particular, the devulcanized rubber product may be soluble in the cyclic ether of formula (I)), whereas the vulcanized rubber is substantially insoluble in the reaction mixture (e.g. is substantially insoluble in the cyclic ether of formula (I)). As such, a filtration step can be a very useful method to separate the devulcanized rubber product from the vulcanized rubber starting material.

[0129] Therefore, in some embodiments, the method further comprises filtering the reaction mixture to separate the devulcanized rubber product from the vulcanized rubber and / or from one or more other components present in the vulcanized rubber. In some embodiments, the filtrate comprises the devulcanized rubber product (optionally the filtrate further comprises the cyclic ether of formula (I)). By way of further example, the devulcanized rubber product may be soluble in the cyclic ether of formula (I) (such as the cyclic ether of formula (la)) whereas the vulcanized rubber may be substantially insoluble in the cyclic ether of formula (I) (e.g. of formula (la)). Such a filtration step may additionally separate the devulcanized rubber product from one or more other components present in the reaction mixture, i.e. one or more other components that are substantially insoluble in the cyclic ether of formula (I) (such as the cyclic ether of formula (la)). By way of example, the one or more other components may be selected from additives, pigments, textiles, metal, and the like (e.g. that may have been present in the vulcanized rubber). In some examples, the one or more other components may be selected from metal (e.g. metal wire), textiles, and pigments (e.g. carbon black).

[0130] In some embodiments, the method may further comprise washing the reaction mixture and / or the devulcanized rubber product with a solvent to remove or reduce an amount of one or more components present in the vulcanized rubber. Where the devulcanized rubber product is present in a filtrate (obtained as described above), the method may comprise washing the filtrate with the solvent. Suitable solvents may include those that are immiscible with the cyclic ether of formula (I).

[0131] In some embodiments, the solvent is an aqueous solvent such as water or a solvent / solution containing substantially water. In other words, the devulcanized rubber product (either perse or when in the reaction mixture) may be contacted with a solvent with a view to removing or reducing an amount of one or more components originally present in the vulcanized rubber, and (residually or otherwise) present in the devulcanized rubber (or the reaction mixture / filtrate. Therefore, in some embodiments, the method further comprises washing the reaction mixture, the devulcanized rubber product and / or filtrate with a solvent to remove or reduce an amount of one or more components present in the vulcanized rubber, optionally wherein the solvent is an aqueous solvent (i.e., water). In particular, the step of

[0132] 16

[0133] 55812689-2washing the reaction mixture, the devulcanized rubber product and / or filtrate with a solvent may remove or reduce an amount of one or more components which are soluble in the solvent. Where the solvent is an aqueous solvent, the step of washing may remove one or more components that are soluble in the aqueous solvent. Alternatively, in some embodiments, the step of washing may modulate the acidity of the filtrate.

[0134] In some embodiments, the washing step may be performed with a view to removing or reducing an amount of sulfur or sulfur-containing byproducts. Such by-products may be formed during the contacting of the peroxide reagent with the vulcanized rubber, likely as a result of the peroxide reagent reacting with cross-linking bonds. The presence of such byproducts in the resultant devulcanized rubber product may be desirable in some instances, but may otherwise be seen as an impurity. Therefore, in some embodiments, the method further comprises washing the reaction mixture, the devulcanized rubber product and / or the filtrate (as described above) with an aqueous solvent (e.g., water or a solvent / solution containing substantially water) to remove or reduce an amount of sulfur and / or sulfur-containing compounds. Examples of sulfur-containing compounds include but are not limited to hydrogen sulfide, sulfur dioxide, carbon disulfide, and acidic sulfuric by-products (such as sulfuric acid).

[0135] As stated above, the devulcanized rubber product may be isolated or separated from the vulcanized rubber by a filtration method, wherein the devulcanized rubber product may be present in the filtrate. In some embodiments, this filtrate may be subjected to a washing step with a solvent (optionally an aqueous solvent). In some embodiments, the method may comprise drying the filtrate and / or drying the devulcanized rubber product. As used herein, the step of “drying” may refer to the removal and / or reduction of water. In other words, in some examples, drying the filtrate with a drying agent may remove residual water or aqueous species from the filtrate. Concentrating the filtrate may enable the isolation of the product in substantially neat form. As used herein, the step of concentration may refer to the removal (or substantial removal) of a solvent from the devulcanized rubber product.

[0136] In view of the above, in some embodiments, the separating and / or isolating may comprise:

[0137] filtering the reaction mixture to provide a filtrate comprising the devulcanized rubber product; and

[0138] washing the filtrate with water or an aqueous solvent / mixture to remove one or more components that are soluble in the aqueous solvent / mixture.

[0139] In some embodiments, the method may further comprise drying the washed filtrate with a drying agent (such as sodium sulfate or magnesium sulfate), and optionally concentrating the filtrate (e.g. using a rotary evaporator).

[0140] 17

[0141] 55812689-2In some embodiments, the method may facilitate a mass recovery of devulcanized rubber product from the vulcanized rubber of at least about 5%.

[0142] The present inventors have found that as the devulcanization process proceeds, the acidity of the reaction mixture increases (without being bound by theory) due to the formation of acidic sulfur by-products. Therefore, in some embodiments, the method comprises contacting the vulcanized rubber with a peroxide reagent in a reaction mixture to provide a devulcanized rubber product and one or more acidic sulfur by-products. In principle, the overall progress or kinetics of the devulcanization process may be determined through measurement of the acidity of the reaction mixture.

[0143] The present inventors have found that treating the vulcanized rubber with a solvent prior to subjecting it to the method of devulcanization disclosed herein, can improve the efficiency of the devulcanization process. Therefore, in some embodiments, the method further comprises pre-treating the vulcanized rubber with a solvent, optionally wherein the solvent is an organic solvent, further optionally wherein the solvent is a cyclic ether of formula (I), e.g. of formula (la).

[0144] Without being bound by theory, the present inventors have found that additives present in vulcanized rubber may be extracted from the vulcanized rubber using an organic solvent, such as the cyclic ethers disclosed herein. These solvents can be particularly useful in reducing the amount of various additives in the vulcanized rubber prior to devulcanization. This ‘pre-treatment’ process has been found to enable a more efficient subsequent devulcanization process as (without being bound by theory) a pre-treated vulcanized rubber has less additives that may otherwise consume (i.e., react with) some of the peroxide reagent that would otherwise react with the cross-linking bonds; any additives that may be extracted with the solvent can also be recovered, by separating the solvent extract from the vulcanized rubber. As an aside, a further possible reason for the increase in efficiency is that the pretreatment swells the vulcanized rubber in preparation for the devulcanization process.

[0145] In some embodiments wherein the solvent is a cyclic ether of formula (I), the solvent is comprised within a peroxide reagent as defined above, or further comprises hydrogen peroxide. That is to say, in some embodiments, the method further comprises pre-treating the vulcanized rubber with a peroxide reagent as defined above, for example the peroxide reagent comprising hydrogen peroxide and a cyclic ether of formula (I). Without being bound by theory, pre-treatment of the vulcanized rubber with a peroxide reagent as defined above may further improve the efficiency of the devulcanization process by dissolving or reacting with (e.g. oxidising) additives in the vulcanized rubber. Additives that have been reacted with (e.g. oxidised) may be inert to the subsequent peroxide reagent in the devulcanization process such that less peroxide reagent is consumed in deleterious side reactions than in the desired reaction of the peroxide reagent with the cross-linking bonds. Alternatively, oxidised additives

[0146] 18

[0147] 55812689-2may be extracted from the pre-treated vulcanized rubber such that they cannot impede the action of the peroxide reagent in the devulcanization process. Certain additives present in the vulcanised rubber, oxidised or otherwise, may be more soluble in the peroxide reagent than in the cyclic ether per se - without being bound by theory, this may be due to the increased polarity of the peroxide reagent with respect to the cyclic ether per se. By pre-treating the vulcanized rubber with the peroxide reagent defined herein, it is possible that the benefits of both the above-described pre-treatment with a solvent (i.e. a cyclic ether of formula (I)) and with the pre-treatment with a peroxide reagent may therefore be obtained.

[0148] Multiple pre-treatment steps may be carried out in order to optimise the vulcanized rubber for the devulcanization process. For example, the vulcanized rubber may be pretreated two or more times, with any combination of (or the same) solvents and / or peroxide reagents in each pre-treatment step. In some embodiments, the method further comprises: (1) pre-treating the vulcanized rubber with a solvent (e.g. a cyclic ether of formula (I)); and (2) pre-treating the vulcanized rubber with a peroxide reagent (e.g. as defined above). In some embodiments, step (1) occurs prior to step (2); in alternative embodiments, step (2) occurs prior to step (1).

[0149] In order to prevent or minimise devulcanization in the pre-treatment process, the pretreatment may be carried out under conditions suitable such that devulcanization is prevented or minimised, for example at a certain temperature. The skilled person will recognise that the pre-treatment conditions i.e. temperature or pressure at which extraction will occur (at a reasonable rate) will depend on other variables such as the nature of the vulcanized rubber, and the nature of the solvent or peroxide reagent. In some embodiments, the pre-treatment step is carried out at a temperature sufficient to induce extraction and not to induce devulcanization. For example, in some embodiments, the pre-treatment step is carried out at a temperature such that the resultant pre-treated vulcanized rubber is substantially vulcanized (particular embodiments as to the definition of vulcanized (i.e. in contrast to devulcanized) are provided below, for example, such that the resultant vulcanized rubber is substantially insoluble in an organic solvent (e.g. at least about 95% insoluble), such as a cyclic ether of formula (I)) after 24 hours at that temperature. In some embodiments where the method further comprises pre-treating the vulcanized rubber with a peroxide reagent as defined above, the pre-treatment step is carried out at a temperature less than a minimum temperature required to induce devulcanization, such as less than about 60, 55, 50, 45, 40, 35, or 30 °C, optionally less than 50 °C. Where the method further comprises pre-treating the vulcanized rubber with a solvent (e.g. a cyclic ether of formula (I)), the step may be carried out at a temperature to induce faster extraction of additives into the solvent, e.g. a temperature of at least about 30, 40, 50, 60, 70, 80, 90, 100, or 110 °C.

[0150] 19

[0151] 55812689-2Non-limiting examples of additives include antioxidants, processing oils, plasticisers, softening agents, and combinations thereof. By way of further example, the additives may include one or more of: antioxidants (such as amino acids, phenols, phospholipids, tocotrienol, betaines, / V-phenyl-1 -naphthylamine, diphenylamine and derivatives (such as alkylated diphenylamines), BHT, Santowhite, tris(nonylphenyl) phosphite, dilauryl thiodipropionate (DLTDP), distearyl thiodipropionate (DSTDP), and 1,2-dihydro-2,2,4-trimethylquinoline (TMQ, Antioxidant 4020)), processing oils (such as polyaromatic hydrocarbons (PAHs), naphthenic oils, paraffin oils, and bio-based oils), plasticisers (such as diisodecyl phthalate (DI DP), dioctyl phthalate (DOP / DEHP), tricresyl phosphate (TCP), triphenyl phosphate (TPP), dioctyl adipate (DOA), dioctyl sebacate (DOS), butyl oleate, methyl oleate, naphthenic oils, paraffinic oils, treated distillate aromatic extract (TDAE), phenolic resins, and hydrocarbon resins (C5 and C9 resins)), and softening agents (such as naphthenic oils, paraffinic oils, treated distillate aromatic extract (TDAE), residual aromatic extract (RAE), mildly extracted solvate (MES), stearic acid, zinc stearate, oleic acid, microcrystalline wax, paraffin wax, phenolic resins, hydrocarbon resins (C5 and C9 resins), epoxidized soybean oil (ESBO), and tall oil derivatives).

[0152] Therefore, in some embodiments where the method further comprises pre-treating the vulcanized rubber with a solvent, the pre-treating the vulcanized rubber with the solvent is to remove or reduce an amount of at least one additive in the vulcanized rubber, and the method comprises: (i) contacting the vulcanized rubber with the solvent for a period of time such that the at least one additive is extracted (e.g., dissolved) into the solvent to provide a solvent extract containing the at least one additive; and (ii) separating the solvent extract from the vulcanized rubber. In some embodiments, the at least one additive is selected from the nonlimiting examples above. In some embodiments, the at least one additive is soluble in an organic solvent, such as a cyclic ether of formula (I) (e.g., of formula (la), TMO).

[0153] Further details of the pre-treatment step are provided below in relation to the third aspect. The examples provided in relation to the third aspect are also equally applicable to this step when used as a pre-treatment step in a method of devulcanization.

[0154] As noted above, devulcanization is a process involving the breaking of (or cleavage of) cross-linking bonds in a rubber, such as C-S and S-S cross-linking bonds, whilst minimising the breaking of the rubber polymer backbone. Therefore, in some embodiments, the method comprises breaking cross-linking bonds (such as C-S and S-S cross-linking bonds) in the vulcanized rubber. Without being bound by theory, the peroxide reagent disclosed herein may break cross-linking bonds by oxidising cross-linking sulfur atoms (such that the cross-linking bonds are broken). Therefore, in some embodiments, the method comprises oxidising cross-linking sulfur atoms such that the cross-linking bonds are broken. This may be achieved by the action of hydrogen peroxide in the peroxide reagent on the cross-

[0155] 20

[0156] 55812689-2linking sulfur atoms, mediated by the cyclic ether. Without being bound by theory, the cyclic ether may form a complex with the hydrogen peroxide (e.g. a 1:1 or 2:1 cyclic ether to hydrogen peroxide complex) which enables the typically aqueous soluble hydrogen peroxide coming into contact with the typically aqueous insoluble vulcanized rubber, allowing oxidation of the cross-linking sulfur atoms to occur. Additionally, the cyclic ether may swell the vulcanized rubber such that the peroxide reagent may penetrate the bulk material of the vulcanized rubber, enabling a more thorough and complete devulcanization process. Various conditions may be tuned such that the cross-linking sulfur atoms are generally oxidised whilst the polymer backbone atoms are not, such as reaction temperature, pressure, the cyclic ether, and concentration of hydrogen peroxide in the peroxide reagent.

[0157] In some embodiments, the devulcanized rubber product comprises a reduced number of cross-linking bonds in comparison to the vulcanized rubber. That is to say, relative to the vulcanized rubber, the devulcanized rubber product is devulcanized. In some embodiments, the devulcanized rubber product comprises less than or equal to about 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, or 5% of the C-S and S-S cross-linking bonds present in the vulcanized rubber. In some embodiments, the devulcanized rubber product comprises substantially no cross-linking bonds.

[0158] A rubber may be considered to be devulcanized, at least to some extent, if the solubility of the devulcanized rubber product in organic solvents (such as a cyclic ether of formula (I)) has increased with respect to the starting vulcanized rubber. For example, a rubber that is entirely (or substantially) devulcanized may be entirely soluble in an organic solvent (such as a cyclic ether of formula (I)). Discussions of solubility herein generally refer to solubility at ambient / standard temperature and pressure; the skilled person will recognise that solubility is dependent on such conditions. Furthermore, the organic solvent often refers to toluene or a cyclic ether of formula (I), such as TMO.

[0159] This increase in solubility is (without being bound by theory) the result of a decrease in the amount of cross-linking bonds in the devulcanized rubber product with respect to the starting vulcanized rubber, the cross-linking bonds comprising sulfur. Hence, one way to determine the amount of vulcanization (and hence the amount of devulcanization) is through the amount of sulfur present in the rubber, which may be quantified in parts per hundred rubber, or phr. Parts per hundred rubber may be calculated by dividing the mass of additive (in this instance, sulfur) by the mass of rubber, and multiplying by 100. By way of example, if 2 g of sulfur is added to 100 g of rubber, the sulfur content may be represented as 2 phr sulfur. Generally speaking:

[0160] • A rubber with high cross-linking typically becomes a rubbery gel with minimal swelling, but no dissolution, upon contact with an organic solvent. Highly cross-linked rubbers typically comprise about 3 to about 4 phr sulfur.

[0161] 21

[0162] 55812689-2• A rubber with moderate cross-linking typically swells significantly in an organic solvent but does not fully dissolve. Moderately cross-linked rubbers typically comprise about 1 to about 3 phr sulfur.

[0163] • A rubber with light cross-linking, e.g., a rubber that is significantly devulcanized, typically dissolves in an organic solvent but may take longer than a substantially or entirely devulcanized rubber. Lightly cross-linked rubbers typically comprise about 0.1 to about 1 phr sulfur.

[0164] • A rubber that is substantially or entirely devulcanized, i.e., comprises no or substantially no cross-linking bonds, typically dissolves in an organic solvent with ease. Such rubbers typically comprise less than or equal to about 0.1 phr sulfur.

[0165] Therefore, in some embodiments where the devulcanized rubber product comprises a reduced number of cross-linking bonds in comparison to the vulcanized rubber, the devulcanized rubber product comprises less than or equal to about 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1 phr sulfur. In some embodiments, the devulcanized rubber product comprises less than or equal to about 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 phr sulfur. In some embodiments, the devulcanized rubber product comprises less than or equal to about 1 , 0.5, or 0.1 phr sulfur.

[0166] The determination of the sulfur content of a rubber, either vulcanized or devulcanized, is within the remit of the skilled person. Methods to quantify phr sulfur include but are not limited to elemental analysis, such as Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES), and X-ray fluorescence (XRF), and the like.

[0167] ASTM standard test D6814 (“Standard Test Method for Determination of Percent Devulcanization of Crumb Rubber Based on Crosslink Density”), incorporated herein by reference, describes a test to determine the extent of devulcanization a rubber might have undergone during a recycling process, such as during a devulcanization process described herein. This test method determines percent devulcanization from cross-link density measurements, which is a quantitative determination.

[0168] As described in the above methods, first, the samples to be tested (around 10 g) are extracted with hot acetone for 16 h in a Soxhlet apparatus. After extraction, the samples are dried at 75 °C in an oven for another 16 h. Then, around 2 g of sample is transferred in a weighed vial. The amount can be adjusted to fill less than % of the vial's volume. Next, the vial is complexly filled with toluene. Every 24 h, the toluene is changed. After a total of 72 h, the excess toluene is eliminated by filtration and the swollen sample, which remained in the vial, is quickly weighed and dried for 24 h at 85° C. in an oven. Finally, the dried sample is weighed. Repeated weighing of the vial at determined time intervals allowed the determination of the

[0169] 22

[0170] 55812689-2retained toluene mass and sample mass at equilibrium. In some cases, to determine the powder's density, a gas pycnometer was used.

[0171] In some embodiments, the devulcanized rubber product is greater than or equal to about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, or 99% devulcanized as determined by ASTM standard D6814 (or modifications thereof), or is about 100% devulcanized as determined by ASTM standard D6814 (or modifications thereof).

[0172] In some cases, a substantially or entirely devulcanized rubber may be readily soluble in an organic solvent such as toluene or a cyclic ether of formula (I) (such as TMO), such that it would result in a degree of devulcanization as determined by the above tests to be greater than or equal to about 95%, or is about 100%. Therefore, in some embodiments, the devulcanized rubber product is greater than or equal to about 95%, 96%, 97%, 98%, or 99% devulcanized, or is about 100% devulcanized, as determined by ASTM standard D6814 (or modifications thereof). As such, in some embodiments, the devulcanized rubber product is substantially soluble in the cyclic ether (at standard temperature and pressure).

[0173] Typically, fora devulcanized rubber product to be used in the preparation of vulcanized rubber (i.e. , to be subject to a vulcanization process), it must comprise unsaturated bonds, such as C=C double bonds. Thus, to facilitate the recycling, re-use and / or further processing of a devulcanized rubber product (e.g. to form new products), the devulcanized rubber products should retain at least some degree of unsaturation in the C-C backbone. By way of example, and as described above, this ensures that there are reactive sites (such as allyl and vinyl sites) for sulfur to react at and form cross-linking bonds. Therefore, a notable benefit of the method of devulcanization described herein is that the process does not necessarily remove unsaturated bonds from the vulcanized rubber, in other words, the peroxide reagent is selective for cross-linking bonds over unsaturated bonds (such as C=C double bonds). In such a case, the devulcanized rubber product obtained by the method comprises unsaturated bonds, such as C=C double bonds. This may increase the value of the devulcanized rubber product, given its greater utility for further vulcanization, amongst other processes. This is notable as, to recycle vulcanized rubber, the vulcanization typically must be removed first (at least to some extent) in order to reshape the rubber in later vulcanization processes, but the vulcanization relies on unsaturation, which, in an unselective devulcanization process, may be removed concomitantly to the cross-linking bonds. As described above, the energy required to break C-S bonds is similar to that needed to break C=C bonds.

[0174] Therefore, in some embodiments, the devulcanized rubber product retains or comprises C=C double bonds. In some embodiments, the devulcanized rubber product retains at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95% of the C=C double bonds present in the vulcanized rubber, optionally wherein the devulcanized rubber product comprises substantially all of the C=C double bonds present in the vulcanized rubber.

[0175] 23

[0176] 55812689-2As noted above, the present invention extends to devulcanized rubber products obtainable or obtained by the methods disclosed herein. As such, the above embodiments described in relation to the devulcanized rubber product provided by the methods described above apply mutatis mutandis to the devulcanized rubber product per se. For example, the devulcanized rubber product may comprise a reduced number of cross-linking bonds in comparison to a vulcanized rubber, such as less than or equal to about 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, or 5% of the C-S and S-S cross-linking bonds present in a vulcanized rubber. The devulcanized rubber product may comprise substantially no crosslinking bonds. Furthermore, the devulcanized rubber product may be greater than or equal to about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, or 99% devulcanized as determined by ASTM standard D6814, or may be about 100% devulcanized as determined by ASTM standard D6814. By way of further example, the devulcanized rubber product may retain or comprise at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95% of the C=C double bonds present in a vulcanized rubber, or the devulcanized rubber product may comprise substantially all of the C=C double bonds present in a vulcanized rubber. In another example, the devulcanized rubber product may comprise less than or equal to about 1, about 0.5, or about 0.1 parts per hundred rubber (phr) sulfur (as defined above). Further, the devulcanized rubber product may be substantially soluble in a cyclic ether as defined above.

[0177] Vulcanized rubber typically comprises one or more rubber polymers selected from natural rubber (NR), styrene-butadiene rubber (SBR), polybutadiene rubber (BR), ethylene propylene diene monomer (EPDM), nitrile rubber (NBR), chloroprene rubber (CR, or neoprene), silicone rubber, and acrylonitrile-butadiene rubber (ABS). Typically, tyres comprise one or more rubber polymers selected from natural rubber (NR), styrene-butadiene rubber (SBR), polybutadiene rubber (BR), ethylene propylene diene monomer (EPDM), and combinations thereof. The method of devulcanization disclosed herein is not limited to any particular vulcanized rubber sample. Therefore, in some embodiments, the vulcanized rubber comprises one or more rubber polymers selected from natural rubber (NR), styrene-butadiene rubber (SBR), polybutadiene rubber (BR), ethylene propylene diene monomer (EPDM), nitrile rubber (NBR), chloroprene rubber (CR, or neoprene), silicone rubber, acrylonitrile-butadiene rubber (ABS), and combinations thereof. In some embodiments, the vulcanized rubber comprises one or more rubber polymers selected from styrene-butadiene rubber, natural rubber (polyisoprene), polybutadiene rubber, ethylene propylene diene monomer rubber, and combinations thereof.

[0178] The vulcanized rubber may be provided in various sizes, shapes, forms, and the invention is not limited as such. For example, the vulcanized rubber may be provided as a whole single piece, e.g., a whole tyre or a single part of a tyre, or it may be provided as an

[0179] 24

[0180] 55812689-2aggregate of objects, e.g., a rubber crumb, possibly prepared through the granulation of waste rubber.

[0181] The present invention may find particular utility in the recycling industry, with respect to the recycling of waste rubber, such as used tyres, although the invention is not limited as such. As described above, used tyres are an abundant resource that contributes significantly to environmental pollution. Therefore, in some embodiments, the vulcanized rubber is:

[0182] (i) from a waste source, such as a pre-consumer or post-consumer waste source, optionally wherein the vulcanized rubber is production waste (e.g., manufacturing production waste); and / or

[0183] (ii) a tyre, optionally a used tyre.

[0184] As described above, viewed from a second aspect, there is provided the use of a peroxide reagent in a method of devulcanizing a vulcanized rubber, wherein the peroxide reagent is as defined in the first aspect of the invention.

[0185] For the avoidance of doubt, all embodiments of the first aspect of the invention, in respect of any feature, apply to the second aspect mutatis mutandis. For example, in some embodiments of the second aspect, R1, R2, R3, and R4are each independently selected from Ci-4alkyl and Ci-4haloalkyl, typically methyl or ethyl, more typically methyl; X and Y are each independently -CR5R6-; each R5and R6is independently selected from H, Ci-4alkyl, halo, and Ci-4haloalkyl, typically H, methyl, and ethyl, more typically H; and / or n is 0, 1, 2, or 3, typically 1 or 2, more typically 1.

[0186] As described above, viewed from a third aspect, there is provided a method of treating or pre-treating a vulcanized rubber to remove or reduce an amount of at least one additive, comprising:

[0187] (i) contacting the vulcanized rubber with a cyclic ether such that the at least one additive is extracted (e.g., dissolved) into the cyclic ether to provide a cyclic ether extract; and

[0188] (ii) separating the cyclic ether extract from the vulcanized rubber;

[0189] wherein the cyclic ether is as defined in the first aspect.

[0190] The method may further comprise: (iii) separating the at least one additive from the cyclic ether extract.

[0191] For the avoidance of doubt, all embodiments of the first aspect of the invention, in respect of any feature, apply to the third aspect. For example, in some embodiments of the third aspect, R1, R2, R3, and R4are each independently selected from Ci-4alkyl and Ci-4haloalkyl, typically methyl or ethyl, more typically methyl; X and Y are each independently -CR5R6-; each R5and R6is independently selected from H, Ci-4alkyl, halo, and Ci-4haloalkyl, typically H, methyl, and ethyl, more typically H; and / or n is 0, 1, 2, or 3, typically 1 or 2, more typically 1.

[0192] 25

[0193] 55812689-2The term “cyclic ether extract” used herein is understood to refer to (typically) a solution (or in some cases, a suspension) of the at least one additive in the cyclic ether.

[0194] As described above with respect to the first aspect of the invention, and without being bound by theory, the present inventors have found that additives present in vulcanized rubber may be extracted from the vulcanized rubber using an organic solvent, such as the cyclic ethers disclosed herein. These solvents can be particularly useful in reducing the amount of various additives in the vulcanized rubber prior to devulcanization. This ‘pre-treatment’ process has been found to enable a more efficient subsequent devulcanization process as (without being bound by theory) a pre-treated vulcanized rubber has less additives that may otherwise consume (i.e. , react with) some of the peroxide reagent that would otherwise react with the cross-linking bonds; any additives that may be extracted with the solvent can also be recovered, by separating the solvent extract from the vulcanized rubber. This pre-treatment process is not limited in its utility to the methods of devulcanization disclosed herein but may be used in combination with other devulcanization methods. As an aside, a further possible reason for the increase in efficiency is that the pre-treatment swells the vulcanized rubber in preparation for the devulcanization process. As described above, the pre-treatment process may also be carried out with a peroxide reagent as defined in the first aspect of the invention. That is to say, in some embodiments, the cyclic ether is, or is comprised in, a peroxide reagent comprising hydrogen peroxide and a cyclic ether of formula (I). In other words, there is provided a method of pre-treating a vulcanized rubber to remove or reduce an amount of at least one additive, comprising: contacting the vulcanized rubber with a peroxide reagent such that the at least one additive is extracted (e.g., dissolved) by the peroxide reagent to provide a peroxide reagent extract, and separating the peroxide reagent extract from the vulcanized rubber; wherein the peroxide reagent is as defined in the first aspect.

[0195] In such embodiments, the at least one additive may be soluble in the cyclic ether and / or the peroxide reagent leading to its dissolution in the peroxide reagent extract. Alternatively, the at least one additive may react with the peroxide reagent (e.g. be oxidised by the peroxide reagent) to form an oxidised additive, and the oxidised additive may be soluble in the cyclic ether and / or peroxide reagent, leading to its dissolution in the peroxide reagent extract. As noted above, and without being bound by theory, additives that have been reacted with (e.g. oxidised) may be inert to the peroxide reagent in any subsequent devulcanization process such that less peroxide reagent is consumed in deleterious side reactions than in the desired reaction of the peroxide reagent with the cross-linking bonds. Oxidised additives may be extracted from the pre-treated vulcanized rubber such that they cannot impede the action of the peroxide reagent in the devulcanization process. The increased polarity of the peroxide reagent with respect to the cyclic ether may result in greater extraction of certain additives,

[0196] 26

[0197] 55812689-2oxidised or otherwise, than using the cyclic ether per se; although other additives may have a greater solubility in the cyclic ether per se.

[0198] In some embodiments, the method comprises repeating steps (i) and (ii), and optionally step (iii), a plurality of times, e.g. 2, 3, 4, or 5 times.

[0199] In other words, in some embodiments, the method comprises multiple pre-treatment steps. In some examples, the method may comprise at least one pre-treatment step with a cyclic ether as defined herein, and at least one pre-treatment step with a peroxide reagent as defined herein. By way of further example, the method may comprise a first pre-treatment step with the cyclic ether (defined above) and a second pre-treatment step with a peroxide reagent (defined above), or vice versa. In some examples, multiple pre-treatment steps with the same solvent or peroxide reagent may be carried out. For example, in some embodiments, the method may comprise a plurality of (e.g. 2, 3, 4, or 5) pre-treatment steps with the cyclic ether (e.g. TMO). By way of further example, in some embodiments, the method may comprise a plurality of (e.g. 2, 3, 4, or 5) pre-treatment steps with the peroxide reagent (e.g. TMO2).

[0200] Each pre-treatment step generally comprises a corresponding separating step, but multiple pre-treatment steps may alternatively comprise a consolidated separating step. The use of multiple pre-treatment steps may allow for an optimised extraction of additives from the vulcanized rubber prior to devulcanization and / or may maximise a recovery of additives from the vulcanized rubber.

[0201] As noted above, in order to prevent or minimise devulcanization in the pre-treatment process, the pre-treatment method may be carried out under conditions suitable such that devulcanization is prevented or minimised, for example at a certain temperature. As described above, the skilled person will recognise that the pre-treatment conditions i.e. temperature or pressure at which extraction will occur (at a reasonable rate) will depend on other variables such as the nature of the vulcanized rubber, and the nature of the solvent or peroxide reagent. In some embodiments, the pre-treatment step is carried out at a temperature sufficient to induce extraction and not to induce devulcanization. For example, in some embodiments, the pre-treatment method is carried out at a temperature such that the resultant pre-treated vulcanized rubber is substantially vulcanized (particular embodiments as to the definition of vulcanized (i.e. in contrast to devulcanized) are provided above, for example, such that the resultant vulcanized rubber is substantially insoluble in an organic solvent (e.g. at least about 95% insoluble), such as a cyclic ether of formula (I)) after 24 hours at that temperature. In some embodiments where the pre-treatment method is carried out with a peroxide reagent, the method is carried out at a temperature less than a minimum temperature required to induce devulcanization, such as less than about 60, 55, 50, 45, 40, 35, or 30 °C, optionally less than about 50 °C. In some embodiments where the pre-treatment method is carried out with a solvent such as a cyclic ether, and not a peroxide reagent (or further comprising hydrogen

[0202] 27

[0203] 55812689-2peroxide), the method may be carried out at a temperature to induce faster extraction of additives into the solvent, e.g. a temperature of at least about 30, 40, 50, 60, 70, 80, 90, 100, or 110 °C.

[0204] The method may comprise separating the at least one additive from the cyclic ether extract (or optionally the peroxide reagent extract). The separating may comprise isolating the at least one additive from the cyclic ether (or optionally the peroxide reagent). For example, the separating (e.g. isolating) may comprise removing the cyclic ether solvent from the at least one additive under reduced pressure or by distillation. Such a separation step may provide an extract comprising the at least one additive.

[0205] It will be appreciated that the ability to extract additives from vulcanized rubber has a utility that is independent of a method of devulcanization. Thus, whilst this method is typically referred to herein as a “pre-treatment” method, methods of contacting a vulcanized rubber with the cyclic ether (and optionally the peroxide reagent) as described herein may be employed independently as a method for extracting additives present in vulcanized rubber. Thus, such methods may also be referred to more simply as a “treatment” method. Thus, the methods may also be considered as a method of treating or pre-treating a vulcanized rubber to extract at least one additive. Accordingly, the disclosure further provides a method of treating or pre-treating a vulcanized rubber to extract at least one additive, comprising:

[0206] (i) contacting the vulcanized rubber with a cyclic ether (e.g. as described herein) such that the at least one additive is extracted (e.g., dissolved) into the cyclic ether to provide a cyclic ether extract; and

[0207] (ii) separating the cyclic ether extract from the vulcanized rubber; and

[0208] (iii) separating the at least one additive from the cyclic ether extract.

[0209] In many cases, the pre-treatment or treatment method may provide a mixture of additives (e.g. a mixture of different types of additives) in the cyclic ether extract. Further downstream processing steps may be carried out on the mixture to allow separation and / or isolation of at least additive from the mixture of additives.

[0210] For example, the method may further comprise separating the mixture of additives (e.g. to isolate one or more additives and / or to provide a mixture (or mixtures) of fewer additives) using any suitable separation and / or extraction techniques as known in the art. Representative examples include filtration, centrifugation, solvent extraction, drying techniques, distillation, and the like.

[0211] Non-limiting examples of additives include antioxidants, processing oils, plasticisers, softening agents, and combinations thereof. By way of further example, the additives may include one or more of: antioxidants (such as amino acids, phenols, phospholipids, tocotrienol, betaines, / V-phenyl-1 -naphthylamine, diphenylamine and derivatives (such as alkylated diphenylamines), BHT, Santowhite, tris(nonylphenyl) phosphite, dilauryl thiodipropionate

[0212] 28

[0213] 55812689-2(DLTDP), distearyl thiodipropionate (DSTDP), and 1,2-dihydro-2,2,4-trimethylquinoline (TMQ, Antioxidant 4020)), processing oils (such as polyaromatic hydrocarbons (PAHs), naphthenic oils, paraffin oils, and bio-based oils), plasticisers (such as diisodecyl phthalate (DI DP), dioctyl phthalate (DOP / DEHP), tricresyl phosphate (TCP), triphenyl phosphate (TPP), dioctyl adipate (DOA), dioctyl sebacate (DOS), butyl oleate, methyl oleate, naphthenic oils, paraffinic oils, treated distillate aromatic extract (TDAE), phenolic resins, and hydrocarbon resins (C5 and C9 resins)), and softening agents (such as naphthenic oils, paraffinic oils, treated distillate aromatic extract (TDAE), residual aromatic extract (RAE), mildly extracted solvate (MES), stearic acid, zinc stearate, oleic acid, microcrystalline wax, paraffin wax, phenolic resins, hydrocarbon resins (C5 and C9 resins), epoxidized soybean oil (ESBO), and tall oil derivatives). By way of further example, the at least one additive may be selected from processing oils, softening agents, plasticizers, pigments (e.g. carbon black), and the like.

[0214] Therefore, in some embodiments, the at least one additive is selected from the nonlimiting examples above. In some embodiments, the at least one additive is soluble in an organic solvent, such as the cyclic ether of formula (I) (e.g., formula (la), TMO). In some embodiments, the at least one additive is soluble in a peroxide reagent as defined in the first aspect.

[0215] EXAMPLES

[0216] I to yield product TMO?

[0217] Preparation, characterisation, and stability of TMO2, an exemplary peroxide reagent comprising hydrogen peroxide and 2,2,5,5-tetramethyltetrahydrofuran (TMTHF), or tetramethyloxolane (TMO) as the cyclic ether.

[0218]

[0219] 30% w / v aqueous TMO

[0220] Scheme 1 : the preparation of TMO2 from hydrogen peroxide and TMO.

[0221] Typical preparation procedure for the preparation of TMOy. Distilled TMO (100 mL) and H2O2 (20 mL, 30% w / v aq.) were stirred vigorously overnight. No observable heat change or colour change occurred upon addition of H2O2. The organic phase (comprising TMO2) was separated from the aqueous phase, dried with Na2SC>4, and filtered. The presence of peroxide was verified via peroxide strip tests (1001000 mg / L, Supelco, 1.10337.0001). The resultant TMO2 product had no discernible difference in colour or viscosity relative to pure TMO.

[0222] 55812689-2Density of TMOy The density of TMO2 (-2.4% w / w H2O2) solution was determined by adding 5 mL of TMO2 using a calibrated micropipette to a beaker on a balance. The measurement was repeated nine times, resulting in an average density of 0.74 g / mL at 21 °C.

[0223] Quantification of H2O2 in TMO2: The percentage weight per weight (% w / w) of hydrogen peroxide was determined through titration against freshly prepared KMnC solution as follows.

[0224] Typical titration procedure: TMO2 (2.00 g) was washed with purified water (4 mL x 4) and the combined aqueous phase was acidified with potassium hydrogen sulfate (0.5% w / v, 2-3 mL). The titrant, KMnC (5% w / w, aq.), was added dropwise until the endpoint of the titration (solution colour change from colourless to purple). The results are shown in Table 1.

[0225] Table 1 : titration results for quantification of H2O2 in TMO2.

[0226]

[0227] Characterisation of TMO2: To assess the presence of peroxide in TMO2, an IR spectrum was obtained, and compared to that of pure TMO (FIG. 1A) and 30% w / v aq. hydrogen peroxide (FIG. 1C). The IR spectrum of TMO2 (FIG. 1B) shows an absorbance at 3342 cm-1, which may be attributed to the -OH stretch of H2O2, and is absent from the IR spectrum of TMO (FIG.

[0228] 1A) but present in 30% w / v aq. hydrogen peroxide solution (FIG. 1C).

[0229] Stability Profile of TMOy. To assess the stability of TMO2, a freshly prepared batch was placed in direct light at room temperature. The sample of TMO2 was titrated four times (in triplicate each time) over a period of 20 days. The percentage of hydrogen peroxide in TMO2 decreased over that time from 2.7% to 2.3% w / w, suggesting that the peroxide is quite stable. It was noted that after 12 days, signs of droplets were observed, suggesting some degradation of the hydrogen peroxide to water. In an analogous stability assessment of refrigerated TMO2 (-5 °C), there was no detectable decrease in the concentration of H2O2. The results are shown in Table 2.

[0230] 30

[0231] 55812689-2Table 2: titration results for quantification of H2O2 in TMO2 over a period of 20 days. N.b., each row is an average of three titrations.

[0232]

[0233] Testing the solubility of various rubber samples in a cyclic ether

[0234] Various rubber samples, including vulcanized and non-vulcanized samples, were suspended in a cyclic ether (namely TMO) to assess the solubility of the samples in the cyclic ether. The rubber samples were portioned into 0.5 g chunks and suspended in 4 mL of TMO. The suspensions were left at room temperature for 16 hours. The results are shown in Table 3.

[0235] 55812689-2Table 3: Solubility experiments of various vulcanized and non-vulcanized rubber samples.

[0236]

[0237] As shown in Table 3, all processed rubbers (i.e., vulcanized rubbers) swelled in size (ca. 3-fold increase in sample volume) but none dissolved in the cyclic ether. For some samples (1A, 1B, 1D, 1E, 1F, and 1M), coloured (e.g., yellow) solutions were observed which, without being bound by theory, indicates that some additives may be being leached out of the sample into the cyclic ether. These experiments demonstrate that the cyclic ether, namely TMO, is not able to dissolve vulcanized rubbers, but is able to dissolve non-vulcanized rubbers. This may pose a significant advantage for the recycling process, where other insoluble elements of waste rubber obtained post-devulcanization may be filtered off (e.g., metal wire, fabric, and carbon black) and separated allowing the bulk recycled rubber (the devulcanized rubber product) to be isolated.

[0238] 55812689-2Treatment of model rubber samples

[0239] A vulcanized rubber sample, comprising SBR and NR, was subjected to a treatment process using a peroxide reagent of the present disclosure, namely TMO2. The vulcanized rubber, and the devulcanized rubber product, were subjected to various chemical analyses, selected from IR (infrared) spectroscopy, STA (simultaneous thermal analysis, comprising differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis), and NMR (nuclear magnetic resonance) spectroscopy. All STA analyses herein were run performed by heating the sample to 600 °C at 10 °C min-1under nitrogen gas.

[0240] Experiment II to yield product 3A: To a 100 mL round bottom flask containing 1.024 g of rubber sample 1A, purged with nitrogen, 15 mL of TMO2 (2.5% H2O2 w / w) was added and the suspension heated to 60 °C with stirring. After 2 h at 60 °C, no further changes were observed, with stirring and heating of the suspension continued. A further 10 mL of TMO2 was added. After 16 h at 60 °C, the suspension remained, but a fine black material was observed (possibly carbon black). The material had swelled (at least 3 times in size). Heating at 60 °C and stirring was continued. After 2 days at 60 °C, the suspension remained; a fine black material was still observed (carbon black). The reaction was cooled to room temperature, the mixture filtered over Celite, and washed with 2 mL of TMO. The filtrate was isolated and evaluated for hydrogen peroxide using a peroxide strip. The strip provided a dark-brown result, demonstrating the presence of hydrogen peroxide. The filtrate was washed with distilled water (3 x 20 mL), dried over Na2SC>4, filtered, and the solvent removed under reduced pressure to afford a dark orange gum that was dried in a vacuum oven overnight. Mass recovered: 0.093 g.

[0241] IR analysis (FIG. 2A and FIG. 2B)

[0242] The peak at -961 cm-1(C=C bending) in FIG. 2A (NR + SBR vulcanized rubber, 1A), is clear and prominent, indicating the presence of unsaturated bonds (C=C) in the backbone of NR and SBR. The spectrum for Product 3A (FIG. 2B) retains strong aliphatic C-H stretching and bending bands, along with the presence of C=O stretching (1712 cm-1). This suggests Product 3A contains processing oils and plasticizers.

[0243] STA analysis (FIG. 2C and FIG. 2D)

[0244] Sample 1A (FIG. 2C): Onset decomposition begins at 330 °C, with major weight loss at 387 °C showing thermal degradation (Tg, black trace) of the organic component with a final decomposition temperature of 438 °C. Residual mass of the sample of -65% can likely be attributed to carbon black, fillers, inorganic components and ash. Absence of melting point is in line with a thermoset cross-linked material. The DSC trace shows possible volatilisation

[0245] 33

[0246] 55812689-2starting at 83 °C with a strong exothermic event (-1934 J / g) at 354 °C, aligning with the onset of the thermal degradation. This data aligns with characteristics from a vulcanised SBR and NR material.

[0247] Product 3A (FIG. 2D): Weight loss for the TMO2 treated product is far higher, with less than 10% mass residue remaining, suggesting that carbon black is not present. The onset of degradation is early, suggesting a weaker molecular structure compared to Sample 1A, such as that in the processing oils, plasticisers etc. A shift in the large exothermic event to 385 °C (DSC trace, green), suggests different decomposition kinetics to the starting material. There are also additional endothermic events at 108 °C and 251 °C which suggest a physical change which is not seen for the starting material. These results indicate that the majority of this TMO2- treated material is likely to be extracted processing oils plasticizers, etc.

[0248]

[0249] Product 3A NMR sample prepared in TFA-d (trifluoroacetic acid-d, CF3CO2D), peaks at 1.0 - 2.5 ppm, 5.2 ppm, 5.65 ppm, and -7.5 - 8.6 ppm.

[0250] Experiment III to yield product 3B: In a 100 mL round bottom flask, purged with nitrogen, 20 mL of TMO2 (2.5% H2O2 w / w) was added to 1.014 g of rubber sample 1A, and the mixture was heated to reflux (approx. 112°C) and stirred mechanically. After 16 hours at reflux, the reaction was stopped. The mixture was then filtered on a bed of Celite. The filtrate was tested for peroxide; the concentration of peroxide was low (less than 50 mg / L). The filtrate was then washed with 20 mL (4 x 5 mL) of water to wash out any residual hydrogen peroxide. The organic phase was separated, dried with Na2SC>4, filtered, and evaporated. Mass recovered: 0.961 g.

[0251]

[0252] The 2950 cm-1shoulder (asymmetric C-H stretch of CH3 / CH2) remains consistent between the starting material and product spectra, indicating that the saturated polymer backbone is intact after the reaction, and indicating effective devulcanization without significant backbone degradation. The 3000 cm-1shoulder (C-H stretch of alkenes) has weakened, reflecting some loss of unsaturation due to oxidation or degradation of C=C bonds. The increased intensity of the C=O peak (1715 cm-1) and stronger C-0 stretching (-1006 cm-1) suggest more oxidation products in the current sample (C=C bonds to carbonyls) and / or the presence of phthalate additives, for example, in the mixture. Overall, this experiment indicates devulcanization is likely to have occurred, but with a possible increase in the reduction in unsaturation.

[0253] 34

[0254] 55812689-2STA analysis (FIG. 3B)

[0255] Product 3B: In comparison with the original material (1A), the mass loss was still notable suggesting removal of additive species, and suggests a polymer structure in corresponding with a devulcanized product.

[0256] NMR analysis

[0257]

[0258] Scheme 2: Chemical structures of natural rubber and styrene butadiene repeat units annotated for NMR analysis.

[0259] Rubber product 3B NMR sample prepared in TFA-d.

[0260] Vinyl Protons of NR and SBR (cis-1,4-polyisoprene): Hb, H1 and H2:

[0261] • Peak at 5.69 ppm:

[0262] • Likely corresponds to the cis-vinyl protons (-CH=CH-) of NR, showing retention of unsaturation after processing with TMO2.

[0263] • This shift is slightly downfield compared to literature values (5.1 ppm, in chloroform) due to the acidity and polarity of TFA-d, resulting in deshielding, causing the chemical shift to move downfield (toward higher ppm values).

[0264] Aromatic Protons of SBR (Styrene Units only): H6, H7, H8:

[0265] • Peaks at ~7.5 - 8.6 ppm:

[0266] • These are characteristic of the aromatic protons of the styrene monomer in SBR. Aliphatic Protons of NR and SBR: Ha, He, Hd, H3, H4, H5, H9:

[0267] • Peaks at ~1.0-2.5 ppm:

[0268] • This region contains signals from the methyl (-CH3), methylene (-CH2-), and methine (-CH-) protons of both NR and SBR backbones.

[0269] Additives:

[0270] • The presence of additives in the sample has resulted in a noisy baseline.

[0271] 35

[0272] 55812689-2Additional analysis

[0273] A 20mg sample of product 3B (recovered recycled rubber polymer) was added to 1mL of toluene and stirred for 1 minute at room temperature. The sample fully dissolved indicating that it was devulcanized.

[0274] Devulcanization of ‘real-world’ rubber samples

[0275] Experiments II and III above demonstrate that TMO2 under reflux enables a large quantity of the rubber starting material to be devulcanized, resulting in a TMO-soluble product which has very different thermal characteristics, whilst retaining C=C unsaturation. As such, the reaction conditions of Experiments II and III were applied to a ‘real-world’ waste tyre sample (rubber sample 1B).

[0276] Experiment IV to yield product 3C: The selected starting material was a waste rubber tyre (side wall), sample 1B (CatchPower Lanvigator 2018, DOT 1P24 AAA 1318). This sample is expected to be a blend of natural rubber (NR), polyisoprene (IR), and ethylene propylene diene monomer (EPDM). Typically, the side wall of a tyre has a relatively low degree of vulcanization. To a 100 mL round bottom flask containing 1.091 g of rubber sample 1 B, purged with nitrogen, 15 mL of TMO2 (2.5% H2O2 w / w) was added and the suspension heated to 60°C with stirring. Initially at room temperature, some effervescence was observed, and the reaction mixture turned to a slight yellow colour. After 2 h at 60 °C, the yellow colour remained, and stirring and heating of the suspension continued. A further 10 mLof TMO2was added. After 16 h at 60 °C, the yellow colour had intensified to a yellow-brown colour. The tyre material had swelled (at least 3 times in size). Heating at 60 °C and stirring was continued. After 16 h at 60 °C, the yellow-brown colour intensified further, and the swelled tyre material remained. The reaction was cooled to RT and the mixture was filtered over Celite, then washed with 2 mL of TMO. The remaining solid on the Celite was isolated. The filtrate was isolated and evaluated for hydrogen peroxide using a peroxide strip. The strip provided a dark-brown result, indicating the presence of hydrogen peroxide. The filtrate was washed with distilled water (3 x 20mL), dried over Na2SC>4, filtered, and the solvent removed under reduced pressure to afford a yellow-brown viscous liquid that was dried in a vacuum oven overnight. Mass recovered: 0.061 g.

[0277] IR analysis (FIG. 4A and FIG. 4B)

[0278] The spectrum of the starting material shows a complex, heterogeneous waste tyre sample with clear evidence of intact hydrocarbon backbones (C-H stretching) and significant amounts of carbon black and sulfur cross-links (as inferred from baseline drift and low-wavenumber complexity). The baseline drift may be caused by light scattering from carbon black and the

[0279] 36

[0280] 55812689-2heterogeneous sample preparation. The spectrum of the product shows C-H stretching bands (2919 and 2850 cm-1) and bending bands (1461 cm-1) and some C=O groups (1710 cm-1).

[0281] STA analysis (FIG. 4C and FIG. 4D)

[0282] Starting material 1 B: As previously seen, a far higher mass loss is seen in the recycled product, indicative of lower carbon black content after processing with TMO2 and filtration.

[0283] NMR analysis

[0284] NMR sample 3C was prepared in CDCh (chloroform-d); peaks: 5.13 - 5.39 ppm.

[0285] Experiment V to yield product 3D: To a 100mL round bottom flask containing 1.035 g of rubber sample 1B, purged with nitrogen, was added 20 mL of TMO2 (2.5% H2O2 w / w). The suspension was heated to reflux and stirred mechanically. After 24 h at reflux, the reaction was stopped. Some pieces of rubber were observed to be suspended in the reaction mixture. The reaction mixture was filtered on a bed of Celite. The filtrate was tested for peroxide, and the concentration peroxide was low (less than 50 mg / L). The filtrate was then washed with 20 mL (4 x 5mL) of water to eliminate the residual hydrogen peroxide. The organic phase was separated, dried with Na2SO4, filtered, and evaporated. Mass recovery: 1.007 g.

[0286] IR analysis (FIG. 5A)

[0287] Devulcanization was evident from the weakening of bands due to sulfur cross-link peaks, whilst some oxidation is indicated by the carbonyl (C=O) peak. The polymer backbone remains largely intact, as shown by the retention of strong C-H stretching and bending peaks, though some oxidative degradation may have occurred. Overall, the process was successful in both purifying the rubber and achieving devulcanization, with only minor undesired oxidation.

[0288] STA analysis (FIG. 5B)

[0289] Very different thermal events in the treated sample are seen compared with the starting material (1B), indicating a different polymer structure. As with other TMO2 treated samples, a high mass loss likely indicates carbon black has been removed during processing.

[0290] NMR analysis

[0291] NMR sample 3D was prepared in CDCh (chloroform-d).

[0292] Unsaturation (C=C) can be seen at 5.12 - 5.38 ppm, showing that when using these conditions, the vast majority of C=C bonds are retained whilst cross-linking bonds are largely removed.

[0293] 37

[0294] 55812689-2Additional analysis

[0295] A 20mg sample of product 3D (recovered recycled rubber polymer) was added to 1mL of toluene and stirred for 1 minute at room temperature. The sample fully dissolved indicating that it was devulcanized.

[0296] Effect of peroxide reagent on non-vulcanized rubber samples

[0297] In an effort to assess loss of unsaturation after exposure of a rubber sample to the devulcanization process, non-vulcanized rubber samples were subjected to the devulcanization method.

[0298] Experiment VI to yield product 3E: The rubber sample in this experiment was a nonvulcanized SBR, sample 10. In a 100mL round bottom flask containing 1.002 g of rubber sample 10, purged with nitrogen, 20 mL of TMO2 (2.5% H2O2 w / w) was added. The mixture was heated to reflux and stirred mechanically. After 16 hours, the reaction was stopped. The reaction mixture was tested for peroxide: the concentration of peroxide was low (less than 50 mg / L). The mixture was then washed with 20 mL (4 x 5 mL) of water to remove residual hydrogen peroxide. The possible formation of several emulsions was observed. The organic phase was separated, dried with Na2SO4, filtered, and evaporated. The resultant material was found to be insoluble in methanol and DMSO; the material swelled in DCM and chloroform. The mass recovery was approximately 98-100%.

[0299] IR analysis (FIG. 6A and FIG. 6B)

[0300] The spectrum of the starting material represents typical non-vulcanized SBR with clearly defined 0=0 double bonds (964 cm-1) and aromatic styrene features (697 cm-1). The backbone is saturated (2916 and 2844 cm-1). In the spectrum of the product, the peaks at 964.77 cm-1and 910.29 cm-1indicate that the double bonds are still present after peroxide reagent treatment. Compared to spectra of the original SBR sample, it appears that there is limited reduction in the intensity of these peaks, suggesting limited impact on unsaturation by the devulcanization process. The broad O-H stretching peak at 3379.91 cm-1suggests the addition of hydroxyl groups, likely due to some oxidation or the presence of water.

[0301] STA analysis (FIG. 6C and FIG. 6D)

[0302] A high mass loss likely indicated both organic and inorganic additives have been washed out during treatment, however, there was also high mass loss seen in the starting material sample. This is expected as this was a ‘model rubber’ and not a post-consumer rubber and as such, will not have a particularly high quantity of additives. The appears to be some oxidation of the

[0303] 38

[0304] 55812689-2C=C bonds in this material, resulting in a mild impact on the thermal characteristics of the recycled rubber product.

[0305]

[0306] Scheme 3: Chemical structure of styrene butadiene repeat unit annotated for NMR analysis.

[0307] Sample 3E NMR sample prepared in TFA-d.

[0308] Vinyl Protons of SBR: H1 and H2:

[0309] • Peak at 5.5 ppm:

[0310] • Likely corresponds to the cis-vinyl protons (-CH=CH-) of NR, showing retention of unsaturation after processing with TMO2, even where there are no or substantially no cross-linking bonds present in the starting material.

[0311] • This shift is slightly downfield compared to literature values (5.1 ppm, in chloroform) due to the acidity and polarity of TFA-d, resulting in deshielding, causing the chemical shift to move downfield (toward higher ppm values).

[0312] Aromatic Protons of SBR (Styrene Units only): H6, H7, H8:

[0313] • Peaks at -7.5 - 8.6 ppm:

[0314] • These are characteristic of the aromatic protons of the styrene monomer in SBR. Aliphatic Protons of SBR: H3, H4, H5, H9:

[0315] • Peaks at -1.0-2.5 ppm:

[0316] • This region contains signals from the methyl (-CH3), methylene (-CH2-), and methine (-CH-) protons of both NR and SBR backbones.

[0317] Additives:

[0318] The presence of additives in the sample has resulted in a noisy baseline.

[0319] Experiment VII to yield product 3F: The rubber sample used in this experiment was a nonvulcanized natural rubber, sample 1G2. In a 100 mL round bottom flask purged with nitrogen, 2 OmL of TMO2 (2.5% H2O2 w / w) was added to 1.014 g of rubber sample 1G2. The mixture was heated to reflux and stirred mechanically. After 16 hours, the reaction was stopped. The

[0320] 39

[0321] 55812689-2mixture was tested for peroxide; the concentration of peroxide was high (more than 1000 mg / L). The filtrate was washed with 20 mL (4 x 5 mL) of water to remove the hydrogen peroxide. The formation of several emulsions was observed; these were removed by adding brine to the aqueous layer. The organic phase was separated, dried with Na2SO4, filtered, and evaporated. The mass recovery was approximately 98-100%.

[0322] IR analysis (FIG. 7A and FIG. 7B)

[0323] The spectrum of the starting material was characteristic of natural rubber (NR) with its typical 0=0 stretching (1664 cm-1) and out-of-plane bending (834 cm-1), confirming the presence of unsaturation in the isoprene units. In the product spectrum, the appearance of an O-H stretching peak (-3320 cm-1) suggests the formation of hydroxyl groups, possibly via epoxidation or some hydrolysis of double bonds during the reaction, or the presence of water. The unchanged C-H stretching (2917 / 2845 cm-1) and bending (1450 cm-1) peaks confirm that the primary polymer backbone remains intact despite the oxidative treatment. Peroxide reagent treatment of the natural rubber may have resulted in some reduction in unsaturation, while introducing hydroxyl groups (3379 cm-1). The polymer backbone appears to remain largely unaffected, indicating that the treatment primarily targets the 0=0 double bonds without significant degradation of the main chain. The spectra before and after treatment have a very similar appearance, which is to be expected when treating a non-vulcanized rubber sample with the peroxide reagent described herein.

[0324] STA analysis (FIG. 7C and FIG. 7D)

[0325] Between the starting material 1G2 and the product 3F, STA demonstrated similar thermal profiles, with minimal change expected in NR and treated NR material.

[0326] NMR analysis

[0327]

[0328] Scheme 4: Chemical structure of natural rubber repeat unit annotated for NMR analysis.

[0329] NMR sample 3F was prepared in CDC (chloroform-d).

[0330] Vinyl Protons of NR: Hb:

[0331] 40

[0332] 55812689-2• Peak at 5.65 ppm

[0333] • Likely corresponds to the cis-vinyl protons (-CH=CH-) of NR, showing retention of unsaturation after processing with TMO2.

[0334] Aliphatic Protons of NR and SBR: Ha, He, Hd, H3, H4, H5, H9:

[0335] • Peaks at -1.0-2.5 ppm: This region contains signals from the methyl (-CH3), methylene (-CH2-), and methine (-CH-) protons of both NR and SBR backbones. Additives:

[0336] • The presence of additives in the sample has resulted in a noisy baseline.

[0337] Further devulcanization experiments on ‘real-world’ rubber samples

[0338] Experiment VIII to yield product 3G: The rubber sample in this experiment was taken from the tread of a ‘real-world’ tyre, rubber sample 1 P. This is expected to be a blend of natural rubber, styrene-butadiene rubber, and polybutadiene, with fillers, having a moderate degree of vulcanization. In a 100 mL round bottom flask, 3.5 g of rubber sample 1P and 50 mL of cyclic ether TMO were stirred overnight to wash out additives from the tyre sample. The extraction solvent was evaporated under vacuum which yield ca. 10% isolated additives relative to the original weight of the sample. The extraction contained additives from the waste rubber. The rubber sample had swelled in size, and the solvent had turned brown. The rubber was filtered on a fritted funnel and dried under vacuum and to give 4.512 g of wet swelled rubber. The large mass was thought to be due to residual TMO present in the sample. 1.494 g of this was taken forward for the peroxide reagent treatment. This was placed in a 100 mL round bottom flask to which 30 g of TMO2 (2.5% H2O2 w / w) were added. After flushing with nitrogen, the system was heated to reflux overnight (16 hours). After this time, the reaction was stopped, and the solution in the flask had turned black. The solution was filtered on a filter made of a Celite cake and cotton to remove the carbon black. The filtrate had a very pale yellow colour and was washed with 5 mL of water. The pH of the aqueous layer was determined to be between 4 and 5. The peroxide level of the aqueous layer was very low. The organic layer was then washed two further times with water (2 x 5 mL). The organic layer was dried with Na2SC>4, filtered, and evaporated under reduced pressure. The product was then dried in a vacuum oven to obtain an oily yellow residue. Mass recovery: 0.418 g.

[0339] NMR analysis

[0340] NMR sample 3G was prepared in CDCh (chloroform-d).

[0341] 41

[0342] 55812689-2Various examples of different unsaturated bonds were demonstrated in the spectrum, relating to natural rubber and polybutadiene, showing that C=C bonds are preserved in the rubber. However, no aromatic signals are seen, but this is likely the result of a) the blend of different polymers, b) the much higher % of vulcanization used in the tread (1P) versus the side wall (1 B) of the tyre. As such, SBR was most likely not depolymerised under these conditions.

[0343] Experiment IX to yield product 3H: In a 100 mL round bottom flask, 3.5 g of rubber sample 1P and 50 mL of cyclic ether TMO were stirred overnight. After this time, the rubber had swelled in size and the solvent had turned brown. The rubber was filtered on a fritted funnel and dried under vacuum. 1.503 g of the rubber sample was placed in a 100 mL round bottom flask to which 30 g of TMO2 (2.5% H2O2 w / w) and boron isopropoxide (207 mg) were added. After flushing with nitrogen, the system was heated to reflux overnight. After this time, the reaction was stopped, and the reaction mixture had turned black. The solution was filtered on a filter made of a Celite cake and cotton to remove the carbon black. The filtrate had a pale yellow colour. The filtrate then washed with 5 mL of water (4 times). The pH of the aqueous layer was around 3 to 4; the peroxide level was negligible. The organic layer was dried with Na2SC>4, filtered, and evaporated under reduced pressure. The product was dried in a vacuum oven to obtain an oily yellow residue. Mass recovered: 0.488 g.

[0344] Investiqations into the acidic nature of the resultant reaction mixtures

[0345] As observed in the above-mentioned experiments, the pH of the reaction mixture appears to decrease (i.e., become more acidic) over the course of the reaction. This was thought to be due to the formation of sulfur-based acidic byproducts resulting from oxidation and cleavage of the sulfur cross-links in the vulcanized rubber samples. Experiments X and XI were carried out to investigate this further.

[0346] Experiment X to yield product 3I: 500 mg of elemental sulfur (Ss, 99.5% purity from Fisher, sample 1Q) was added to a 100 mL round bottom flask. Following this, 42.403 g of TMO2 (2.5% H2O2 w / w) was then added. The mixture was stirred for 48 h at 100 °C. After this time, the reaction mixture had become a brown-orange colour. The peroxide level in the reaction mixture was negligible; the pH was highly acidic (ca. 1). The mixture was treated with 40 mL of a solution of BaCh (0.25 M) to precipitate the sulfur in form of BaSC . The mixture was stirred over 72 hours. After this time, a substantial quantity of white precipitate was observed to have formed. The mixture was centrifuged; the organic phase (supernatant) was treated overnight with a further portion of BaCh. The resultant precipitate was washed twice with water and centrifuged twice. The resultant solid residue was dried overnight in a vacuum oven. Mass: 0.927 g; estimated conversion of 25% (based on Ss in SO42" precipitated as BaSC ).

[0347] 42

[0348] 55812689-2IR analysis (FIG. 10)

[0349] An IR spectrum of the product shows that when S-S type bonds are exposed to the experimental conditions above, S-S bond breaking and subsequent generation of a highly acidic species, most likely H2SO4, is observed. Without being bound by theory, it is thought that this mechanism occurs during the treatment of a vulcanized rubber with a peroxide reagent, such as TMO2.

[0350] Experiment XI to yield product 3J: To a 100 mL round bottom flask, 1.07 g of rubber sample 1 A (SBR and NR) and 20 g of TMO2 (2.5% H2O2 w / w) were added, and the system was flushed with nitrogen. A first aliquot of 0.5 mL was taken and extracted with 3 x 1 mL of distilled water (To'). The pH of the aqueous layer was 7. The system was then heated to reflux. Once at reflux, a further sample of 0.5 mL was taken and extracted with 3 x 1 mL of distilled water (To). The pH of the aqueous layer was 7. This sampling procedure was repeated at several intervals over the reaction time of 16 hours; the results are found in Table 4. The peroxide level of the final reaction mixture was low (less than 50 mg / L).

[0351] Table 4: Change in acidity of the reaction mixture over the course of the reaction time. The pH was measured from the aqueous wash.

[0352]

[0353] Overall, it is clear that as the reaction proceeds that the acidity increases (without being bound by theory) due to the formation of acidic sulfur by-products. These reaction conditions emulated experiment III, where a mass recovery of devulcanized product was 95%.

[0354] 55812689-2Investigations into pre-treatment of the vulcanised rubber

[0355] Extractions of a real-world rubber tyre sample were carried out at room temperature with both TMO (Experiment XII) and TMO2 (Experiment XIII); both experiments were run in duplicate (experiments ‘a’ and ‘b’). The results are summarised in Table 5.

[0356] Experiment XII: In a 100 mL round bottom flask, 5.0 g of a used passenger car tyre and 70 mL of cyclic ether TMO were stirred at room temperature overnight. After this time, the rubber had swelled in size and the solvent had turned dark brown. The solvent was decanted and then resulting swelled rubber suspended in 70 mL of fresh cyclic ether TMO once again and stirred at room temperature overnight. After this time, the solvent had turned brown. The solvent was decanted and resulting swelled rubber washed with 10 mL of fresh cyclic ether TMO. The swelled rubber was dried in the vacuum oven (55 °C, 3 days). All cyclic ether TMO fractions / washings were combined, filtered by gravity and solvent removed from the filtrate (by rotatory evaporation) to afford a dark brown viscous oil (further dried in the vacuum oven, 55 °C, 3 days). Xlla: mass of extracted oils / additives: 0.401 g (recovery: 7.90%); mass of rubber: 4.746 g (recovery: 93.59%). Xllb: mass of extracted oils / additives: 0.395 g (recovery: 7.85%); mass of rubber: 4.726 g (recovery: 94.16%).

[0357] Experiment XIII: In a 100 mL round bottom flask, 5.0 g of a used passenger car tyre and 70 mL of TMO2 (2.5% H2O2 w / w) were stirred at room temperature overnight. After this time, the rubber had swelled in size and the solvent had turned dark brown. The solvent was decanted and then resulting swelled rubber suspended in 70 mL of fresh TMO2 (2.5% H2O2 w / w) once again and stirred at room temperature overnight. After this time, the solvent had turned brown. The solvent was decanted and resulting swelled rubber washed with 10 mL of fresh TMO2 (2.5% H2O2 w / w). The swelled rubber was dried in the vacuum oven (55 °C, 3 days). All TMO2 fractions / washings were combined, and peroxide quenched with aq. 10% Na2SC>4 solution (2 x 50mL), dried over Na2SO4, filtered and solvent removed from the filtrate (by rotatory evaporation) to afford a dark brown viscous oil (further dried in the vacuum oven, 55 °C, 3 days). Xllla: mass of extracted oils / additives: 0.292 g (recovery: 5.90%); mass of rubber: 4.590 g (recovery: 92.76). XI II b: mass of extracted oils / additives: 0.279 g (recovery: 5.65%); mass of rubber: 4.649 g (recovery: 94.15%).

[0358] 44

[0359] 55812689-2Table 5: Summary of results into pre-treatment of vulcanized rubber with TMO or TMO2.

[0360]

[0361] All experiments were conducted at room temperature for 2 days. Starting rubber (g) refers to the mass of rubber before treatment; Extracts (g) refers to the mass of extracts / additives recovered; Recovered rubber (g) refers to the mass of (vulcanised) rubber recovered.

[0362] Analysis (FIG. 11)

[0363] As demonstrated by Table 5 above, TMO2 extracts a lower overall quantity of additives compared to TMO per se. However, IR analysis of the extracted and recovered oils shows a more pronounced IR absorbance in the carbonyl region for extracts obtained using TMO2 (FIG. 11B) than for TMO per se (FIG. 11 A). Without being bound by theory, this is consistent with TMO2 having a higher polarity than TMO per se, and therefore preferentially / selectively extracting more polar species from the rubber matrix, including components containing carbonyl functionalities (e.g. -1709 cm-1as seen in overlapped spectra in FIG. 11C).

[0364] Investigation into the effect of temperature on the devulcanization process

[0365] The devulcanization of a pre-treated (TMO washed) real-world rubber sample was carried out at three different temperatures: 40 °C (Experiment XIV), 60 °C (Experiment XV), and 80 °C (Experiment XVI). The results are summarised in Table 6.

[0366] Experiment XIV: In a 100 mL round bottom flask, 1.0 g of a TMO pre-washed passenger car tyre and 70 mL of TMO2 (2.5% H2O2 w / w) were stirred at 40 °C overnight. After this time, the rubber had swelled in size and the solvent had blackened (i.e. fine carbon black in suspension). The solvent was filtered off, swelled rubber isolated and dried in the vacuum oven (55 °C, 3 days). Mass of recovered solid vulcanized rubber: 0.95 g.

[0367] Experiment XV: In a 100 mL round bottom flask, 1.0 g of a TMO pre-washed passenger car tyre and 70 mL of TMO2 (2.5% H2O2 w / w) were stirred at 60 °C overnight. After this time, the rubber had swelled in size and the solvent had blackened (i.e. fine carbon black in suspension). The solvent was filtered off, swelled rubber isolated and dried in the vacuum oven (55 °C, 3 days). Mass of recovered solid vulcanized rubber: 0.92 g.

[0368] 55812689-2Experiment XVI: In a 100 mL round bottom flask, 1.0 g of a TMO pre-washed passenger car tyre and 70 mL of TMO2 (2.5% H2O2 w / w) were stirred at 80 °C overnight. After this time, the rubber had swelled in size and the solvent had blackened (i.e. fine carbon black in suspension). The solvent was filtered off, swelled rubber isolated and dried in the vacuum oven (55 °C, 3 days). Mass of recovered solid vulcanized rubber: 0.70 g.

[0369] Table 6: Summary of results of investigation into effect of temperature on devulcanization process using TMO2.

[0370]

[0371] All experiments were conducted with 1 g of vulcanized rubber for 16 hours. Recovered rubber (g) refers to the mass of solid rubber (vulcanized) recovered.

[0372] Although the present disclosure has been described in some detail by way of illustration and example for purposes of clarity of understanding, the descriptions and examples should not be construed as limiting the scope of the disclosure. The disclosures of all patent and scientific literature cited herein are expressly incorporated herein in their entirety by reference.

[0373] 55812689-2

Claims

CLAIMS1. A method of devulcanizing a vulcanized rubber, the vulcanized rubber comprising cross-linking bonds, wherein the method comprises:contacting the vulcanized rubber with a peroxide reagent in a reaction mixture to provide a devulcanized rubber product;wherein the peroxide reagent comprises:(a) hydrogen peroxide; and(b) a cyclic ether;wherein the cyclic ether is of formula (I):wherein:R1, R2, R3, and R4are each independently selected from Ci-4alkyl and Ci-4haloalkyl; X and Y are each independently -CR5R6-;each R5and R6is independently selected from H, Ci-4alkyl, halo, and Ci-4haloalkyl; andn is 0, 1, 2 or 3.

2. The method of claim 1 , wherein the cyclic ether is a cyclic ethereal solvent.

3. The method of claim 1 or 2, wherein the peroxide reagent consists of, or consists essentially of: (a) hydrogen peroxide; and (b) the cyclic ether.

4. The method of any one preceding claim, wherein R1, R2, R3, and R4are each independently selected from methyl, ethyl, and trifluoromethyl, optionally wherein:(i) R1and R2are the same;(ii) R3and R4are the same; or(iii) R1, R2, R3, and R4are all the same.

5. The method of any one preceding claim, wherein R1, R2, R3, and R4are each selected from Ci-4alkyl, such as methyl.4755812689-26. The method of any one preceding claim, wherein each R5and R6is independently selected from H, methyl, ethyl, fluoro, difluoromethyl, trifluoromethyl, perfluoroethyl, optionally wherein each R5and R6is independently selected from H, methyl, and ethyl, further optionally wherein each R5and R6is H.

7. The method of any one preceding claim, wherein n is 1 or 2.

8. The method of any one preceding claim, wherein the cyclic ether is of formula (la) or (lb):optionally wherein the cyclic ether is of formula (la).

9. The method of any one preceding claim, wherein the concentration of hydrogen peroxide in the peroxide reagent is from about 0.05% to about 50% w / w, from about 0.05% to about 25% w / w, from about 0.5% to about 10% w / w, or from about 1% to about 5% w / w, or from about 2% to about 4% w / w, or about 3% w / w.

10. The method of any one preceding claim, wherein the contacting comprises heating the reaction mixture to reflux (e.g., the boiling point of the peroxide reagent, or the boiling point of the cyclic ether); and / or heating the reaction mixture to from about 50 °C to about 120°C , from about 55 °C to about 115°C, or from about 60 °C to about 112 °C.

11. The method of any one preceding claim, wherein the contacting is carried out under an inert atmosphere (e.g., under an atmosphere of nitrogen or argon gas) and / or the contacting is carried out anhydrous conditions.

12. The method of any one preceding claim, further comprising:contacting the vulcanized rubber with a catalyst, optionally wherein the catalyst is a Lewis acid catalyst, further optionally wherein the catalyst is selected from molybdenum trioxide, titanium tetraisopropoxide, boron triisopropoxide, and sodium tungstate.

13. The method of any one preceding claim, wherein the weight ratio of the peroxide reagent to the vulcanized rubber (peroxide reagent : vulcanized rubber) is in the range of from55812689-2about 0.01:1 to about 100:1, from about 0.1:1 to about 50:1, from about 0.2:1 to about 10:1, or from about 0.25:1 to about 2:1 (such as 0.25:1 or 0.5:1).

14. The method of any one preceding claim, wherein the cross-linking bonds are selected from S-S and C-S bonds.

15. The method of any one preceding claim, further comprising:separating and / or isolating the devulcanized rubber product from the vulcanized rubber and / or from one or more other components present in the vulcanized rubber (such as additives, pigments, textiles, metal and the like).

16. The method of any one preceding claim, further comprising filtering the reaction mixture to separate the devulcanized rubber product from the vulcanized rubber and / or from one or more other components present in the vulcanized rubber,optionally wherein the filtrate comprises the devulcanized rubber product.

17. The method of any one preceding claim, further comprising:washing the reaction mixture and / or the devulcanized rubber product with a solvent to remove or reduce an amount of one or more components present in the vulcanized rubber;optionally wherein the solvent is an aqueous solvent.

18. The method of claim 17, wherein the method comprises:washing the reaction mixture and / or the devulcanized rubber product with an aqueous solvent (e.g., water) to remove or reduce an amount of sulfur and / or sulfur-containing compounds.

19. The method of any one preceding claim, further comprising:pre-treating the vulcanized rubber with a solvent, optionally wherein the solvent is an organic solvent, and further optionally wherein the solvent is a cyclic ether as defined in any one of claims 1 to 9, optionally wherein the cyclic ether is comprised within a peroxide reagent as defined in claims 1 to 9.

20. The method of claim 19, wherein pre-treating the vulcanized rubber with the solvent is to remove or reduce an amount of at least one additive in the vulcanized rubber, and comprises:4955812689-2contacting the vulcanized rubber with the solvent for a period of time such that the at least one additive is extracted (e.g., dissolved) into the solvent to provide a solvent extract containing the at least one additive; andseparating the solvent extract from the vulcanized rubber.

21. The method of any one preceding claim, wherein the devulcanized rubber product comprises a reduced number of cross-linking bonds in comparison to the vulcanized rubber, optionally wherein the devulcanized rubber product comprises less than or equal to about 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, or 5% of the C-S and S-S crosslinking bonds present in the vulcanized rubber;further optionally wherein the devulcanized rubber product comprises substantially no cross-linking bonds.

22. The method of any one preceding claim, wherein the devulcanized rubber product is greater than or equal to about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, or 99% devulcanized as determined by ASTM standard D6814, or is about 100% devulcanized as determined by ASTM standard D6814 .

23. The method of any one preceding, wherein the devulcanized rubber product retains or comprises at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95% of the C=C double bonds present in the vulcanized rubber,optionally wherein the devulcanized rubber product comprises substantially all of the C=C double bonds present in the vulcanized rubber.

24. The method of any one preceding claim, wherein the devulcanized rubber product comprises less than or equal to about 1, about 0.5, or about 0.1 parts per hundred rubber (phr) sulfur.

25. The method of any one preceding claim, wherein the devulcanized rubber product is substantially soluble in the cyclic ether.

26. The method of any one preceding claim, wherein the vulcanized rubber comprises one or more rubber polymers selected from styrene-butadiene rubber, natural rubber (polyisoprene), polybutadiene rubber, ethylene propylene diene monomer rubber, and combinations thereof.

27. The method of any one preceding claim, wherein the vulcanized rubber is:5055812689-2(i) from a waste source, such as a pre-consumer or post-consumer waste source, optionally wherein the vulcanized rubber is production waste (e.g., manufacturing production waste); and / or(ii) a tyre, optionally a used tyre.

28. Use of a peroxide reagent in a method of devulcanizing a vulcanized rubber, wherein the peroxide reagent is as defined in any one preceding claim.

29. A method of treating or pre-treating a vulcanized rubber to remove or reduce at least one additive, or a method of treating a vulcanized rubber to extract at least one additive, the method comprising:(i) contacting the vulcanized rubber with a cyclic ether such that the at least one additive is extracted (e.g., dissolved) into the cyclic ether to provide a cyclic ether extract; and (ii) separating the cyclic ether extract from the vulcanized rubber;wherein the cyclic ether is of formula (I):wherein:R1, R2, R3, and R4are each independently selected from Ci-4alkyl and Ci.4haloalkyl; X and Y are each independently -CR5R6-;each R5and R6is independently selected from H, Ci-4alkyl, halo, and Ci.4haloalkyl; andn is 0, 1, 2 or 3.

30. The method of claim 29, wherein the cyclic ether is as defined in any one of claims 2 to 8.

31. The method of claim 29 or 30, wherein the cyclic ether is comprised within the peroxide reagent as defined in any one of claims 1 to 9.

32. The method of any one of claims 29 to 31, wherein the method further comprises:(iii) separating or isolating the at least one additive from the cyclic ether extract.55812689-233. The method of any one of claims 29 to 32, wherein the method comprises repeating steps (i) and (ii), and optionally step (iii), a plurality of times.

34. A devulcanized rubber product obtainable by the method of any one of claims 1 to 27.55812689-2

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