Rubber composition comprising an amount of recycled rubber

Abstract

The invention relates to a rubber composition comprising at least 20% and up to 99% by weight of a recycled rubber selected from the group comprising ethylene-propylene diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR) and mixtures thereof, and characterised in that: - the vulcanised rubber composition has a retention of at least 65% in terms of tensile strength and a retention of at least 75% in terms of elongation at break, the percentages being expressed relative to a vulcanised virgin material tested according to standard ISO 37; or - a tensile strength of at least 7 MPa and an elongation at break of at least 180% in the presence of at least 65% by weight of the recycled rubber, preferably GTR tyres.

Description

[0001] RUBBER COMPOSITION INCLUDING A QUANTITY OF RECYCLED RUBBER

[0002] The present invention relates to a rubber composition comprising a quantity of recycled rubber, its manufacturing process and its uses.

[0003] Rubber is a material widely used in many fields, for example in aeronautics, the automotive industry, construction, and civil engineering.

[0004] Rubber can be either natural, when it is obtained from natural products, such as the rubber tree, or synthetic, when it comes from the petrochemical industry.

[0005] The current economic climate is pushing companies to try to find greener and more sustainable solutions. The idea is to be able to recover used rubber materials after their first life cycle and give them a second life in order to limit the use of natural or synthetic rubber, and more specifically rubbers obtained through chemical products derived from petroleum.

[0006] Currently, companies are running out of solutions and generally decide to send these used materials to a technical landfill, to be discarded, which blocks any prospect of further recovery of this waste.

[0007] One of the difficulties encountered lies in devulcanization, which is often ineffective on recycled rubbers. Furthermore, crosslinking the material by vulcanization in the presence of sulfur does not allow for the incorporation of sufficient recycled material into a new composition. Indeed, this crosslinking must be effective in order to achieve sufficient mechanical properties and enable its use in various application areas.

[0008] For example, US patent 6,515,059 discloses the possibility of utilizing EPDM waste with a content of less than 50% by weight relative to the final composition, which consists primarily of virgin rubber. Although this patent provides a composition based on recycled rubber, it appears that the greater the quantity of recycled rubber, the less advantageous the mechanical properties of the resulting composition become. Thus, the quantities of rubber that can be reused remain limited, making it impossible to eliminate the need for virgin materials. Furthermore, the mechanical properties reported in the aforementioned patent remain insufficient, particularly when a quantity of recycled and devulcanized EPDM is incorporated into the composition.

[0009] At present, the compositions provided contain a greater quantity of virgin rubber compared to the quantity of recycled rubber.

[0010] More broadly, used rubbers based on ethylene-propylene-diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR), GTR tires and their blends are not sufficiently utilized in subsequent generation products (2 ème generation, 3 ème generation, etc).

[0011] There is therefore a real need to provide a recycled rubber composition, supplied at a low cost, which allows the incorporation of a large quantity of recycled rubber, while retaining advantageous mechanical properties compared to compositions based on virgin rubber.

[0012] To solve this problem, the present invention provides a rubber composition comprising at least 20% by weight and up to 99% by weight of a recycled rubber selected from the group comprising ethylene-propylene-diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR), GTR tires and their mixtures and characterized in that: said vulcanized rubber composition exhibits a retention of at least 65% in terms of tensile strength and a retention of at least 75% in terms of elongation at break, said percentages being expressed relative to a virgin vulcanized material tested according to ISO 37, or a tensile strength of at least 7 MPa and an elongation at break of at least 180% in the presence of at least 65% by weight of said recycled rubber, preferably from GTR tires.

[0013] The recycled rubber selected from the group comprising ethylene-propylene-diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR), GTR tires and their mixtures is advantageously recycled rubber that has been previously devulcanized, preferably by (thermo)mechanical means.

[0014] Surprisingly, it appears that the rubber composition according to the invention comprises at least 20% by weight and up to 99% by weight, preferably up to 98% by weight, more preferably up to 97% by weight, advantageously up to 96% by weight, more advantageously up to 95% by weight, of recycled rubber and exhibits a retention of at least 65% in terms of breaking strength and a retention of at least 75% in terms of elongation at break, said percentages being expressed in relation to a virgin vulcanized material tested according to ISO 37.

[0015] The remainder of the rubber composition may include a rubber activator and a vulcanizing agent to enable the vulcanization of the recycled material.

[0016] The invention makes it possible to valorize significant quantities of rubber that can come from the recycling sector.

[0017] In the presence of virgin rubber, the tensile strength and elongation resistance are even higher than those indicated above. Furthermore, the properties can be greatly improved compared to a composition made solely of virgin rubber, which is particularly advantageous.

[0018] This means that for a quantity of recycled rubber in the rubber composition according to the invention, the tensile strength and elongation at break properties of this vulcanized composition are significantly superior to a composition with an equal recycled rubber content from the prior art.

[0019] This allows up to 99% by weight, preferably up to 98% by weight, more preferably up to 97% by weight, advantageously up to 96% by weight, more advantageously up to 95% by weight, of recycled (devulcanized) rubber in the composition according to the invention, preferably in the presence of activation and vulcanizing agents.

[0020] According to a preferred mode, the rubber composition according to the invention has a tensile strength of at least 9 MPa and an elongation at break of at least 300% in the presence of at least 65% by weight of said recycled rubber, preferably at least 75% by weight, preferably EPDM.

[0021] Preferably, the rubber composition according to the invention exhibits: - a retention of at least 65% and up to 100% in terms of tensile strength and a retention of at least 75% in terms of elongation at break when the recycled rubber is selected from the group comprising EPDM, SBR, and their combinations, or - a retention of at least 70% and up to 100% in terms of tensile strength and elongation at break when the recycled rubber is NR, or

[0022] - a retention of at least 80% and up to 100% in terms of breaking strength and elongation at break when the recycled rubber is IR.

[0023] Advantageously, the rubber composition according to the invention has a total sulfur content (including the sum of the amounts of bound sulfur and free sulfur) of at least 2% by weight, preferably at least 2.5% by weight, more preferably at least 3% by weight, relative to the total weight of the composition.

[0024] Preferably, the rubber composition according to the invention has a free sulfur content of between 0.5 and 5% by weight.

[0025] According to a preferred embodiment, the rubber composition according to the invention has: a breaking strength of at least 9 MPa and an elongation at break of at least 300% in the presence of at least 65% by weight of said recycled rubber, preferably at least 75% by weight, preferably of EPDM or SBR or IR, or a breaking strength of at least 7 MPa and an elongation at break of at least 180% in the presence of at least 65% by weight of GTR tires from car tires, or a breaking strength of at least 10 MPa and an elongation at break of at least 250% in the presence of at least 65% by weight of GTR tires from truck tires.

[0026] Preferably, the rubber composition according to the invention is obtained by the process comprising the following steps: a) Providing a vulcanized elastomer waste selected from the group comprising ethylene propylene diene monomer (EPDM), styrene butadiene rubber (SBR), natural rubber (NR), synthetic isoprene (IR), GTR tires, and their mixtures; b) Devulcanizing said elastomer waste by (thermo)chemical or (thermo)mechanical means to obtain a devulcanized material, preferably in the form of a paste, said devulcanized material having a bound sulfur content of between 0.5 and 5% by weight and a viscosity of between 20 and 100 Mooney, preferably between 45 and 75 Mooney, determined according to ISO 289; c) Mixing a sufficient quantity, preferably at least 20% by weight, more preferably up to 99% by weight. weight, preferably up to 98% by weight, more preferably up to 97% by weight,advantageously up to 96% by weight, more advantageously up to 95% by weight, of said devulcanized material with at least one rubber activator and a vulcanizing agent comprising sulfur, forming a crosslinkable mixture comprising at least 0.25% by weight, preferably between 0.25% and 10% by weight, more preferably between 0.25% and 5% by weight of bound sulfur, and between 0.25% and 5% by weight of free sulfur, relative to the total weight of said mixture; (d) Vulcanization of said mixture with formation of the rubber composition exhibiting a retention of at least 65% in terms of tensile strength and a retention of at least 75% in terms of elongation at break, said percentages being expressed relative to a virgin vulcanized material tested according to ISO 37,or a tensile strength of at least 7 MPa and an elongation at break of at least 180% in the presence of at least 65% by weight of said recycled rubber, preferably from GTR tires.

[0027] Preferably, during the process, some bound sulfur remains in the material after devulcanization. After devulcanization, a paste may be obtained. This paste can then be vulcanized in the presence of vulcanizing and activating agents at a specific temperature to transition from a paste-like state to a solid state.

[0028] The bound sulfur is inert and will not react during vulcanization.

[0029] Advantageously, the mixing step is carried out by adding at least 20% by weight, preferably at least 30% by weight, more preferably at least 40% by weight, more preferably still at least 50% by weight, advantageously at least 65% by weight, more advantageously at least 75% by weight of said devulcanized material, relative to the total weight of said mixture, and preferably up to 99% by weight, preferably up to 98% by weight, more preferably up to 97% by weight, advantageously up to 96% by weight, more advantageously up to 95% by weight, of said devulcanized material.

[0030] According to a preferred mode, the process includes, preferably before, during or after the mixing step, an addition of a virgin elastomer, preferably a virgin rubber, selected from the group comprising ethylene-propylene-diene monomer (EPDM), styrene-butodiene (SBR), natural rubber (NR), synthetic isoprene (IR), GTR tires and their mixtures.

[0031] According to a more preferential method, the so-called sufficient quantity of said devulcanized material is greater than the quantity of virgin elastomer added to form said mixture before vulcanization.

[0032] Advantageously, said mixing step is carried out by adding between 20 and 99% by weight, preferably between 65 and 99% by weight, of said devulcanized material and between 10% and 80% by weight, preferably between 10 and 35% by weight of said virgin elastomer, relative to the total weight of said mixture.

[0033] Even more advantageously, said mixing step is carried out by adding between 20 and 99% by weight, preferably between 65 and 99% by weight, preferably between 65 and 98% by weight, more preferably between 65 and 97% by weight, advantageously between 65 and 96% by weight, more advantageously between 65 and 95% by weight of said devulcanized material.

[0034] Preferably, between 10% and 80% by weight, preferably between 10% and 35% by weight of said virgin elastomer are added to said mixture relative to its total weight.

[0035] More advantageously, when at least 65% by weight of said devulcanized material is added to said mixture, preferably in the presence of said virgin elastomer, the resulting rubber composition exhibits a retention of at least 65% in terms of tensile strength and a retention of at least 75% in terms of elongation at break, said percentages being expressed relative to virgin vulcanized material tested according to ISO 37 or a tensile strength of at least 7 MPa and an elongation at break of at least 180% in the presence of at least 65% by weight of said recycled rubber, preferably from GTR tires. In this embodiment, for the retention values, the recycled rubber is selected from the group comprising ethylene propylene diene monomer (EPDM), styrene butadiene rubber (SBR), natural rubber (NR), and synthetic isoprene (IR). GTR is therefore preferably not included in this group.

[0036] Advantageously, the quantity of virgin elastomer can be between 10 and 35% by weight relative to the total weight of the rubber composition.

[0037] Preferably, the rubber composition is produced by continuous extrusion. More preferably, the vulcanized elastomer waste or virgin elastomer is supplied in granule form.

[0038] Advantageously, said rubber activating agent is preferably zinc oxide, and is added in an amount between 0.1% and 10% by weight.

[0039] More advantageously, the said vulcanizing agent, preferably sulfur, is added in an amount between 0.5% and 5% by weight.

[0040] According to an advantageous method, comprising a rubber vulcanization accelerator in an amount between 0.5% and 5% by weight, relative to the total weight of the composition.

[0041] Particularly advantageously, the vulcanization accelerator is chosen from the group consisting of N-cyclohexyl-2-benzothiazole-sulfenamide (CBS), 2,2-dibenzothiazole disulfide (MBTS), tetramethyl thiurame disulfide (TMTD) or any equivalent.

[0042] The presence of a vulcanization accelerator speeds up the vulcanization process, preferably by adding free sulfur to the rubber compound according to the invention. Depending on the desired mechanical properties and / or the chemical composition of the rubber compound, and the transformation process adopted, it may be advantageous to modify the amount of vulcanization accelerator. The vulcanization accelerator speeds up the vulcanization reaction and provides a rubber compound that is activated (i.e., ready to be effectively crosslinked / vulcanized).

[0043] It is also understood that most of the free sulfur comes from the vulcanizing agent which contains sulfur, or possibly from the vulcanizing accelerator which also provides a quantity of free sulfur.

[0044] In a preferred embodiment of the invention, all the steps of the process are carried out successively so as to provide the composition according to the invention in the form of an extruded strip which can be stored for at least 24 hours, with preservation of the stated properties.

[0045] In a preferred embodiment of the invention, the rubber composition further comprises additives selected from the group consisting of reinforcing fillers, diluting fillers, fatty acids, preferably stearic acid, plasticizers, ozone suppressants, antioxidants, oils, and mixtures thereof. Thermoplastic elastomers, also known as thermoplastic rubbers, are a type of material generally obtained by physically blending a plastic and a rubber. This particular blend results in a material exhibiting both thermoplastic and elastomeric characteristics. Thermoplastic rubbers, unlike thermosets, are easier to use in the manufacture of parts such as injection-molded parts. They combine the advantages of both rubber and plastic materials.

[0046] Preferably, the composition according to the invention further comprises a compatibilizing agent, preferably in solid or liquid form, comprising a thermoplastic polymer in an amount of between 0.5 and 25% by weight relative to the total weight of the composition.

[0047] Thermoplastic rubbers are widely used due to their numerous applications. Their diverse uses stem from their versatile mechanical properties: primarily their settling and elastic recovery, as well as their temperature resistance. They have various applications in construction, for manufacturing window profiles with insulation, expansion joints, and weatherproofing profiles. In industry, they are used to produce anti-vibration components, anti-slip parts, cable protectors, sports equipment, and toys.

[0048] The compatibilizing agent will further broaden the scope of application of the rubber composition according to the invention. Therefore, vulcanization is not necessarily required when a thermoplastic polymer is present.

[0049] The mixture of a thermoplastic polymer and an elastomer is known as "TPE-V" or "TPV" for a vulcanized polypropylene / ethylene-propylene-diene (PP / EPDM) blend and as TPE-O or TPO for an unvulcanized polypropylene / ethylene-propylene-diene (PP / EPDM) blend. These blends are olefin-based thermoplastic elastomers in which elastic polymer chains are bonded within a thermoplastic material.

[0050] TPVs are dynamically vulcanized during a compounding process. This vulcanization process modifies the structure of the rubber phase, making it more durable. In particular, it enables its compression set, elasticity, and resistance to aggressive fluids such as oils and solvents. This process modifies the rubber phase by creating cross-links or chemical bridges between the different rubber chains, forming a network structure.

[0051] The thermoplastic polymer is preferably derived from a polymer based on polypropylene, polyethylene or polyurethane for example.

[0052] Advantageously, the recycled rubber is made from GTR tires and, after vulcanization, is blended with thermoplastic polymers that have not necessarily undergone devulcanization. These thermoplastic polymers can then be added to the GTR tires, which have already been devulcanized. This allows for the production of a blend that primarily comprises devulcanized GTR rubber and the thermoplastic polymer as defined in the invention.

[0053] Preferably, the rubber composition according to the invention comprises a quantity of bitumen of at least 5%, relative to the total weight of the composition.

[0054] Bitumen is not particularly limited and can be chosen by those skilled in the art according to the requirements of the final product. Typical bitumen bases suitable for use in the rubber composition according to the invention include distillation bitumens of varying degrees of penetration, hard road bitumens, oxidized bitumens, and cutback bitumens.

[0055] The present invention also relates to products comprising the rubber composition according to the invention and may therefore concern the following objects:

[0056] Product containing the rubber composition according to the invention, or

[0057] Tires comprising the rubber composition according to the invention, or

[0058] Seals or sealants comprising the rubber composition according to the invention, or

[0059] Elastic (anti-vibration) sole for railway track comprising the rubber composition according to the invention, or

[0060] Roofing waterproofing membrane comprising the rubber composition according to the invention.

[0061] The invention also relates to the uses of the composition in tires (all possible types of tires, bicycle, motorcycle, car, airplanes, trucks, ...) in civil engineering, in construction, etc.

[0062] The invention also relates to a method for manufacturing the rubber compound according to the invention and comprises the following steps: a) Providing vulcanized elastomer waste selected from the group comprising ethylene propylene diene monomer (EPDM), styrene butadiene rubber (SBR), natural rubber (NR), synthetic isoprene (IR), GTR tires, and their mixtures; b) Devulcanizing said elastomer waste by (thermo)chemical or (thermo)mechanical means to obtain a devulcanized material, preferably in the form of a paste, said devulcanized material having a bound sulfur content of between 0.5 and 5% by weight and a viscosity of between 20 and 100 Mooney, preferably between 45 and 75 Mooney, determined according to ISO 289; c) Mixing a sufficient quantity, preferably at least 20% by weight, more preferably up to 99%. % by weight, preferably up to 98% by weight, more preferably up to 97% by weight,advantageously up to 96% by weight, more advantageously up to 95% by weight, of said devulcanized material with at least one rubber activator and a vulcanizing agent comprising sulfur, forming a crosslinkable mixture comprising at least 0.25% by weight, preferably between 0.25% and 10% by weight, more preferably between 0.25% and 5% by weight of bound sulfur, and between 0.25% and 5% by weight of free sulfur, relative to the total weight of said mixture; (d) Vulcanization of said mixture with formation of the rubber composition exhibiting a retention of at least 65% in terms of tensile strength and a retention of at least 75% in terms of elongation at break, said percentages being expressed relative to a virgin vulcanized material tested according to ISO 37,or a tensile strength of at least 7 MPa and an elongation at break of at least 180% in the presence of at least 65% by weight of said recycled rubber, preferably from GT tires.

[0063] All the characteristics mentioned above for the composition and for the rubber compositions obtained according to the process described are applicable to the manufacturing process of the rubber composition according to the invention.

[0064] The present invention thus enables the creation of new types of deposits by allowing the use of rubber waste that can be devulcanized and then reintegrated into vulcanizable products with advantageous mechanical properties. This type of recycled rubber is the focus of the present invention.

[0065] Thus, the invention targets recycled rubber (read: waste) that primarily comes from recycling streams. In other words, used rubber will be recycled by being processed (through devulcanization) and preferably supplied in granule form. Furthermore, these types of rubber were vulcanized during their initial use and then transformed into granules. Devulcanization transforms the material into a paste, which solidifies after further vulcanization.

[0066] According to the invention, preferably, the recycled rubber used in the context of the invention is devulcanized recycled rubber.

[0067] In a particularly advantageous manner, the rubber composition is presented in the form of a paste, preferably in the form of an extruded strip, which is also ready to be easily and directly vulcanized to form a solid product after vulcanization.

[0068] Rubber is a viscoelastic material whose behavior lies between that of a viscous fluid and an elastic solid. Measuring Mooney viscosity allows us to predict the deformation and flow behavior of the material under stress.

[0069] The devulcanization step, by (thermo)chemical or (thermo)mechanical means, of said elastomer waste (read: recycled rubber in the invention) yields a devulcanized material, preferably in the form of a paste. This devulcanized material has a bound sulfur content of between 0.5 and 5% and a viscosity of between 20 and 100 Mooney, preferably between 45 and 75 Mooney, determined according to ISO-289. This devulcanized material thus possesses resistance to deformation and flow under stress that is ideal for the intended applications. These applications may include, for example, the manufacture of tires for the automotive industry, seals, and elastic pads (anti-vibration, for example, in railways, or sealing membranes during vulcanization).

[0070] Recycled rubbers such as EPDM, SBR, NR, IR, and GTR tires represent the majority of constituents found in elastomer waste. More specifically, these materials can originate from, among other things, waste truck tires, car tires, aircraft tires, seals, anti-vibration mount sealants, springs, adhesives, or elastic membranes. In a preferred embodiment of the invention, the recycled rubber used in the context of the invention is devulcanized EPDM.

[0071] EPDM elastomers make up the majority of the components found in elastomer waste. More specifically, these materials generally come from used waterproofing membranes.

[0072] When percentages (%) are indicated, they are expressed by weight unless otherwise stated.

[0073] According to the invention, crosslinking refers to the crosslinking of a rubber or elastomer with sulfur, more specifically called vulcanization because sulfur is used as the vulcanizing agent. The term crosslinking, which thus encompasses vulcanization, also covers other types of crosslinking agents, such as peroxides. In the following, the terms crosslinking and decrosslinking will therefore respectively encompass the terms vulcanization and devulcanization.

[0074] The adjective "used" or "recycled" or the noun "waste" used in the present invention encompasses end-of-life products, discarded products, or stored waste.

[0075] The term "bonded sulfur" should be understood as referring to sulfur that is bonded to another sulfur atom (SS) or to a carbon atom (SC). This term also refers to sulfur that could be described as partially bonded, particularly when a devulcanization step has been performed. It is understood that this term indirectly characterizes the composition according to the invention, in that it contains a certain quantity of vulcanized and / or devulcanized elastomer waste. This bonded sulfur can be detected by elemental analysis of an intensively washed rubber composition, for example, by Soxhlet extraction using a solvent.

[0076] The term "free sulfur" should be understood as referring to sulfur that is not bound to the elastomer / rubber present in the composition. This free sulfur may originate from the sulfur-based vulcanizing agent and also, "optionally," from a vulcanization accelerator, for example, CBS or TMTD. This free sulfur, with or without the vulcanization accelerator, can be recovered in solution during intensive washing of said composition according to the invention, for example, by Soxhlet extraction. Sulfur content can be determined by the PCS calcination method (standard EN 15408) and by measuring the sulfur content in the fume wash. In devulcanized rubber or devulcanized elastomer, some of the sulfur bonds are broken, while others remain partially bound. These bonds can be of the SS (sulfur-sulfur) and / or CS (carbon-sulfur) types. Thus, these sulfur-based bonds form bridges between the macromolecular chains of the rubber.Devulcanization breaks the bonds that link several macromolecule chains, but in most cases, the sulfur remains attached to a rubber macromolecule. The devulcanization process allows for the recovery of used rubber material. More precisely, devulcanization consists of partially destroying the three-dimensional network of rubber by breaking the carbon-sulfur or sulfur-sulfur bonds.

[0077] The amount of sulfur in a compound can be determined by elemental analysis. To ensure that the amount of sulfur measured in elemental analysis corresponds to the amount of sulfur bound to the rubber, the rubber compound can be intensively washed, for example by Soxhlet extraction, using a sulfur solvent. This washing solubilizes any free sulfur that may be present in the rubber compound. By bound sulfur, we mean the sulfur that can be detected by elemental analysis in a rubber compound washed in this way.

[0078] Sulfur content can be determined by the PCS calcination method (NF EN 15408 standard) and by measuring the amount of sulfur in the flue gas scrubbing.

[0079] The term "virgin rubber," "virgin elastomer," or "virgin material" should be understood as referring to rubber that has not undergone vulcanization and has therefore not been devulcanized. This constitutes virgin, non-recycled raw material.

[0080] The terms "recycled rubber," "used rubber," or "elastomer waste" refer, within the context of this invention, to used elastomer waste selected from the group consisting of EPDM, SBR, NR, SBR, GTR tires, and their mixtures. Any compound that has undergone an initial cycle of vulcanization and use and has become obsolete for its primary uses can be defined as "recycled rubber," "used rubber," or "elastomer waste," and which has subsequently been devulcanized as described in the present invention.

[0081] The term "devulcanized material" in the context of this invention refers to recycled rubber or other equivalent term mentioned above that has undergone a devulcanization process using (thermo)chemical and / or (thermo)mechanical methods. This devulcanized material is ready for further vulcanization after the addition of additives.

[0082] The term "rubber composition" refers to the final product, preferably obtained according to the process described in the present invention. In practice, this refers to the product obtained by vulcanizing the devulcanized material described above.

[0083] All the properties of the rubber composition according to the invention advantageously target rubber in the vulcanized state.

[0084] The term GTR tires comes from the English "Ground Tire Rubber" and refers to elastomers selected from the group consisting of SBR, NR, SBR, and their blends. Those skilled in the art also know that these elastomer scraps may also include other compounds such as carbon black, steel, etc. Any compound used in the manufacture of this type of tire is therefore included within the scope of the present invention.

[0085] Within the scope of the present invention, the rubber composition can be characterized by a retention (expressed as a percentage) in terms of tensile strength and elongation, as well as in terms of values ​​corresponding to tensile strength (expressed in MPa) and elongation (expressed as a percentage). When the recycled rubber is selected from the group consisting of ethylene propylene diene monomer (EPDM), styrene butadiene rubber (SBR), natural rubber (NR), synthetic isoprene (IR), and mixtures thereof, the retention expressed above and in the remainder of the text, as well as the values ​​in terms of tensile strength and elongation, can be applied. Indeed, for each compound included in the closed list above, there is a corresponding reference in terms of virgin rubber, which allows the result to be expressed in terms of retention.

[0086] Within the scope of this invention, the parameters expressed when the recycled rubber is from GTR tires will be those indicated by the tensile strength and elongation resistance. Indeed, it is more difficult to express a percentage of retention as described in this text, given that it is a composite material. For this reason, the values ​​of tensile strength and elongation are preferred to characterize the composition, which includes GTR tires as a component to be recycled.

[0087] This reasoning can be applied to all types of recycled raw materials (ethylene propylene diene monomer (EPDM), styrene butadiene (SBR), natural rubber (NR), synthetic isoprene (IR), GTR tires and their compounds). More specifically, it can concern the following products: truck tires, car tires, or even elastic soles, seals or membranes, preferably made from rubbers used in the construction or civil engineering sectors.

[0088] The devulcanization step makes it possible to partially break some of the SC and SS bonds present in the rubber waste in order to make it suitable for the recovery envisaged within the framework of the present invention.

[0089] Although those skilled in the art are familiar with devulcanization techniques, the present invention prefers to apply devulcanization achieved by mechanical shearing, preferably under the action of heat (i.e., thermomechanical). This step can be followed by cooling and the addition of the vulcanizing agent, the activating agent, and additives to provide a composition that is considered "active" in that it only needs to be vulcanized at a specific vulcanization temperature.

[0090] This devulcanization is preferably carried out with an extruder on a continuous conveyor belt.

[0091] The devulcanization carried out within the framework of the present invention is advantageously done in the absence of devulcanizing agent or oils.

[0092] The tensile strength and elongation at break shown in the invention can be determined according to ISO 37, preferably when the composition is vulcanized.

[0093] Within the framework of the present invention, any singular article such as, for example, "a", "an", "the", "of", "of" can be replaced by an article or an expression which designates a plural such as, for example, "at least 2", "at least 3", "several", etc.

[0094] The word "include," "contains," or any equivalent or derived term can be replaced by "consisting of" to define a list or exclusive selection possibilities so as not to include other elements not mentioned in the expression used. Example 1

[0095] Table 1

[0096] This corresponds to 100% retention in terms of breaking strength and 100% retention in terms of elongation at break.

[0097] Example 2

[0098] Table 2 The difference between EPDM 1, shown in Example 1, and that of Example 2 lies in its formulation. This type of composition corresponds to a retention of 65% in terms of tensile strength and a retention of 75% in terms of elongation at break. Example 3 Table 3

[0099] After vulcanization, the composition exhibits a tensile strength of 7 MPa and an elongation at break of 180%.

[0100] Example 4 Table 4

[0101] After vulcanization, the composition exhibits a tensile strength of at least 10 MPa and an elongation at break of 250%.

[0102] It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made to it without departing from the scope of the annexed claims.

Claims

DEMANDS 1. A rubber composition comprising at least 20% by weight and up to 99% by weight of recycled rubber selected from the group comprising ethylene propylene diene monomer (EPDM), styrene butadiene (SBR), natural rubber (NR), synthetic isoprene (IR), GTR tires and their mixtures and characterized in that: said vulcanized rubber composition exhibits a retention of at least 65% in terms of tensile strength and a retention of at least 75% in terms of elongation at break, said percentages being expressed in relation to virgin vulcanized material tested according to ISO 37, or a tensile strength of at least 7 MPa and an elongation at break of at least 180% in the presence of at least 65% by weight of said recycled rubber, preferably from GTR tires.

2. Rubber composition according to claim 1, having a tensile strength of at least 9 MPa and an elongation at break of at least 300% in the presence of at least 65% by weight of said recycled rubber, preferably at least 75% by weight, preferably EPDM.

3. Rubber composition according to claim 1 or 2, having: - a retention of at least 65% and up to 100% in terms of tensile strength and a retention of at least 75% in terms of elongation at break when the recycled rubber is chosen from the group including EPDM, SBR, and their combination, or - a retention of at least 70% and up to 100% in terms of tensile strength and elongation at break when the recycled rubber is NR, or - a retention of at least 80% and up to 100% in terms of breaking strength and elongation at break when the recycled rubber is IR.

4. Rubber composition according to any one of the preceding claims, having a total sulfur content (including the sum of the amounts of bound sulfur and free sulfur) of at least 2% by weight, preferably at least 2.5% by weight, more preferably at least 3% by weight, relative to the total weight of the composition.

5. Rubber composition according to any one of the preceding claims having: - a tensile strength of at least 9 MPa and an elongation at break of at least 300% in the presence of at least 65% by weight of said recycled rubber, preferably at least 75% by weight, preferably EPDM, or SBR or IR, or - a tensile strength of at least 7 MPa and an elongation at break of at least 180% in the presence of at least 65% by weight of GTR tires from car tires, or - a breaking strength of at least 10 MPa and an elongation at break of at least 250% in the presence of at least 65% by weight of GTR tires from truck tires.

6. A rubber composition according to any one of the preceding claims, being obtained by a process comprising the following steps: a) Providing vulcanized elastomer waste selected from the group comprising ethylene propylene diene monomer (EPDM), styrene butadiene rubber (SBR), natural rubber (NR), synthetic isoprene (IR), GTR tires, and their mixtures; b) Devulcanizing said elastomer waste by (thermo)chemical or (thermo)mechanical means to obtain a devulcanized material, preferably in the form of a paste, said devulcanized material having a bound sulfur content of between 0.5 and 5% by weight and a viscosity of between 20 and 100 Mooney, preferably between 45 and 75 Mooney, determined according to ISO 289; c) Mixing a sufficient quantity, preferably at least 20% by weight, more preferably up to 99% by weight, preferably up to 98% by weight, more preferably up to 97% by weight,advantageously up to 96% by weight, more advantageously up to 95% by weight, of said devulcanized material with at least one rubber activator and a vulcanizing agent comprising sulfur, forming a crosslinking-ready mixture comprising at least 0.25% by weight, preferably between 0.25% and 10% by weight, more preferably between 0.25% and 5% by weight of bound sulfur, and between 0.25% and 5% by weight of free sulfur, relative to the total weight of said mixture, d) Vulcanization of said mixture with formation of the rubber composition which has a retention of at least 65% in terms of breaking strength and a retention of at least 75% in terms of elongation at break, said percentages being expressed in relation to virgin vulcanized material tested according to ISO 37, or a breaking strength of at least 7 MPa and an elongation at break of at least 180% in the presence of at least 65% by weight of said recycled rubber, preferably from GTR tires.

7. Rubber composition according to any one of the preceding claims, wherein the mixing step is carried out by adding at least 20% by weight, preferably at least 30% by weight, more preferably at least 40% by weight, more preferably still at least 50% by weight, advantageously at least 65% by weight, more advantageously at least 75% by weight of said devulcanized material, relative to the total weight of said mixture.

8. Rubber composition according to any one of the preceding claims, comprising, preferably before, during or after the mixing step, an addition of a virgin elastomer, preferably a virgin rubber, selected from the group comprising ethylene-propylene-diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR), GTR tires and their mixtures.

9. Rubber composition according to any one of the preceding claims, wherein the said sufficient quantity of said devulcanized material is greater than the quantity of virgin elastomer added to form said mixture prior to vulcanization.

10. Rubber composition according to any one of the preceding claims, wherein said mixing step is carried out by adding between 20 and 99% by weight, preferably between 65 and 99% by weight, of said devulcanized material and between 10% and 80% by weight, preferably between 10% and 35% by weight of said virgin elastomer, relative to the total weight of said mixture.

1. Rubber composition according to any one of the preceding claims, wherein when at least 65% by weight of said devulcanized material is added to said mixture, preferably in the presence of said virgin elastomer, the resulting rubber composition exhibits a retention of at least 65% in terms of tensile strength and a retention of at least 75% in terms of elongation at break, said percentages being expressed in relation to virgin vulcanized material tested according to ISO 37 or a tensile strength of at least 7 MPa and an elongation at break of at least 180% in the presence of at least 65% by weight of said recycled rubber, preferably from GTR tires.

12. Rubber composition according to any one of the preceding claims, being implemented by continuous extrusion.

13. Rubber composition according to any one of the preceding claims, wherein said vulcanized elastomer waste or virgin elastomer is supplied in the form of granules.

14. Rubber composition according to any one of the preceding claims further comprising a compatibilizing agent, preferably in solid or liquid form, comprising a thermoplastic polymer in an amount of between 0.5 and 25% by weight, relative to the total weight of the composition.

15. Rubber composition according to any one of the preceding claims, comprising a quantity of bitumen of at least 5%, relative to the total weight of the composition.

16. Product containing the rubber composition according to any one of the preceding claims.

17. Tyres comprising the rubber composition according to any one of claims 1 to 15.

18. Seals or sealants comprising the rubber composition according to any one of claims 1 to 15.

19. Elastic (anti-vibration) sole for railway track comprising the rubber composition according to any one of claims 1 to 15.

20. Roofing waterproofing membrane comprising the rubber composition according to any one of claims 1 to 15.

21. Use of the rubber composition according to any one of claims 1 to 15 in tires, in civil engineering, in construction.

Images