Rubber composition ready for crosslinking

Abstract

The present invention relates to a composition comprising: - 30% to 90% by weight rubber; - 0.1% to 10% by weight of an activating agent; - 0.5 to 5% by weight of a vulcanizing agent containing sulfur; characterized in that said composition comprises a total of at least 0.25% by weight bound sulfur and 0.1% to 5% by weight free sulfur.

Description

[0001]READY-TO-CROSSLINK RUBBER-BASED COMPOSITION The present invention relates to a ready-to-crosslink rubber-based composition, to its manufacturing process and to its uses. Rubber is a material widely used in many fields, for example in aeronautics, in the automotive industry, in the field of construction or in civil engineering. Currently, it would be advantageous to be able to revalue used rubber materials that are available to the user in order to reintegrate them into a production cycle of value-added end products. To do this, the used rubber material must be able to be revalued and allow production of these end products, while retaining mechanical properties that are at least equivalent, or even improved, compared to products made from virgin (raw) rubber (properties adapted to the application),or non-recycled. The interest lies not only in the revaluation of stored waste, end-of-life products or production scrap. Also, this allows a reduction in the manufacturing costs of final products using used rubber materials that are revalued. When the rubber material is used, it may contain a certain amount of bound sulfur since it results from a vulcanization process, when sulfur is used as a vulcanizing agent. This material can be revalued and lead to final products based on these vulcanized rubber materials. Generally, current sectors in the rubber sector do not allow for rapid and easy low-cost recovery of used vulcanized rubber materials. In addition, waste based on vulcanized rubber is not recycled or is rarely recycled. Indeed,Recycling processes for this type of waste are expensive and difficult to implement. The rubber from these recycling processes generally has less attractive mechanical properties, which also results in the production of end products with inadequate properties. In order to attempt a low recovery of this vulcanized rubber waste, it is possible to provide a composition that mainly comprises virgin rubber in the presence of a small quantity of vulcanized rubber, which is still insufficient in view of the current economic situation. Another disadvantage linked to the prior art is the fact that several industrial steps are necessary to provide a vulcanized material from waste or used materials. It may therefore happen that the user must identify sources of used raw materials, then,treat them by companies specializing in devulcanization. The addition of the final ingredients necessary for vulcanization of the material can also be carried out by another actor, which greatly complicates the preparation and production costs. There is therefore a real need to provide a rubber-based composition that is ready to be directly vulcanized, at a low cost, while enhancing the contribution of used rubber materials and retaining advantageous or even improved mechanical properties compared to compositions based on virgin rubber. To solve this problem, the present invention provides a rubber-based composition ready for crosslinking, preferably in the form of an extruded strip, said composition comprising: a) A total amount of rubber of between 30% and 90% by weight or between 30 and 99% by weight; b) A rubber activating agent in an amount of between 0,1% and 10% by weight; c) A vulcanizing agent which comprises sulfur, in an amount of between 0.5 and 5% by weight; characterized in that said ready-to-crosslink composition comprises a total amount of bound sulfur of at least 0.25%, preferably between 0.25% and 10% by weight, more preferably between 0.25% and 5% by weight, preferably between 0.1 and 5% by weight, and an amount of free sulfur of between 0.1 and 5%, each aforementioned % by weight being expressed relative to the total weight of the composition. The composition according to the invention solves the above problems in that it contains an amount of bound sulfur of between 0.1 and 10% by weight,relative to the total weight of said composition. This quantity of bound sulfur means that a (major) part of the rubber comes from elastomer waste which has already been vulcanized (fully or partially) and which thus contains a certain quantity of bound sulfur. Advantageously, the quantity of bound sulfur is provided by the supply of rubber, a major part of which comes from elastomer waste which has already been vulcanized and then devulcanized, preferably by (thermo)mechanical means, and which thus contains a certain quantity of bound sulfur. In this embodiment, a part of the sulfur bonds is broken but remains (partially bound), which is also part of the present invention. These bonds can be SS or SC bonds. The quantities of bound sulfur expressed above also apply to the aforementioned embodiments. Preferably,these devulcanized elastomer wastes make it possible to provide a composition according to the invention. Preferably, said composition comprises a total quantity of rubber of between 30% and 90% by weight or between 30 and 99% by weight, preferably between 40 and 99% by weight, more preferably between 45 and 99% by weight, even more preferably between 50 and 99% by weight. The invention makes it possible to recover substantial quantities of rubber which can come from the recycling sector. This is particularly advantageous given that the prior art is limited to smaller quantities in the proposed compositions. The present invention also preferentially targets a composition which is in the form of a strip which comprises a non-negligible total quantity of rubber. The preferred mass ratio between free sulfur and bound sulfur of the composition according to the invention is between 0.1 and 10, preferably between 1 and 2,when advantageously the rubbery material (the rubber) consists of 100% devulcanized rubber. The preferred mass ratio between free sulfur and bound sulfur of the composition according to the invention is between 0.2 and 15, preferably between 1.5 and 3, when the rubbery material (the rubber) comprises 50% by weight, preferably less than 50% by weight, more preferably less than 40% by weight of accelerated virgin rubber (comprising at least the activating and vulcanizing agent) and 50% by weight of devulcanized rubber, preferably more than 50% by weight, more preferably more than 55% by weight, even more preferably more than 60% by weight of devulcanized rubber. Even more advantageously, the preferred mass ratio between free sulfur and bound sulfur of the composition according to the invention is between 0.1 and 5, preferably between 0.5 and 1,when the rubber material comprises 50% virgin rubber (unaccelerated) and 50% devulcanized rubber. Also, it is understood that the majority of the free sulfur comes from the vulcanizing agent which comprises sulfur, or possibly from the vulcanization accelerator which also provides a quantity of free sulfur. Finally, the ready-to-crosslink rubber-based composition is formulated so that it already contains the quantities of activating agent, for example zinc oxide (ZnO), and vulcanizing agent, preferably consisting of sulfur and possibly an accelerator, which allows direct vulcanization of the composition. This composition is thus advantageous for the user who can quickly and easily use the composition according to the invention. According to a particularly advantageous embodiment,the composition is in the form of an extruded strip which is also ready to be vulcanized easily and directly. When the composition is an extruded strip, it is in the form of a ready-to-use paste. In a preferred embodiment of the invention, the composition, preferably in the form of an extruded strip, has a viscosity of between 20 and 85 Mooney, preferably between 35 and 80 Mooney,measured according to ISO-289 or ASTM D1646-19a. Rubber is a viscoelastic material whose behavior lies between a viscous fluid and an elastic solid. Measuring the Mooney viscosity makes it possible to predict the deformation and flow behavior of the material under the effect of stress. The composition according to the invention having a viscosity of between 20 and 85 Mooney thus has a resistance to deformation and flow under stress which is ideal for the applications envisaged. These may, for example, concern the manufacture of tires in the automobile industry, seals, elastic soles (anti-vibration) (railway), etc. In a preferred embodiment of the invention, the composition further comprises a rubber vulcanization accelerator in an amount of between 0.5% and 5% by weight, relative to the total weight of said composition. In a particularly advantageous manner,the vulcanization accelerator is chosen from the group consisting of N-cyclohexyl-2-benzothiazole-sulfenamide (CBS), 2,2-dibenzothiazole disulfide (MBTS), tetramethyl thiuram disulfide (TMTD) and any equivalent. The presence of vulcanization accelerator makes it possible to accelerate the vulcanization process, preferably by adding free sulfur to the composition according to the invention. Depending on the desired mechanical properties and / or the chemical composition of the composition, and the transformation process adopted, it may be advantageous to modify the quantity of vulcanization accelerator. The vulcanization accelerator makes it possible to accelerate the vulcanization reaction and to provide a composition which will be activated (read, ready to be crosslinked / vulcanized effectively). In a preferred embodiment of the invention, the composition further comprises additives chosen from the group consisting of reinforcing fillers, diluting fillers,fatty acids, preferably stearic acid, plasticizers, anti-ozone protectors, antioxidants, oils and mixtures thereof. The presence of additives makes it possible to provide a composition intended for use in a final product which must have a certain number of technical characteristics. The choice and quantity of additive are guided by the rheological, physicochemical and mechanical characteristics of the products which it is desired to manufacture with the composition. Finally, certain additives protect the composition from possible degradation. In an advantageous embodiment, the activating agent is zinc oxide. In a preferred embodiment of the invention, said rubber is derived from a devulcanized rubber, preferably by (thermo)mechanical means, which is present in an amount of between 51% and 100% by weight, preferably between 55% and 100% by weight, more preferably between 60% and 100% by weight,more preferably still between 70% and 100% by weight, advantageously between 80% and 100% by weight, more advantageously between 90% and 100% by weight, relative to the total weight of rubber. Advantageously, said rubber comprises a virgin rubber, which is present in an amount of between 10 and 49% by weight, preferably between 10% and 40% by weight, more preferably between 10% and 35% by weight, more preferably still between 10% and 30% by weight, advantageously between 10% and 25% by weight, more advantageously between 10% and 20% by weight, relative to the total weight of rubber. According to a preferred embodiment, the devulcanized rubber is predominantly present in said rubber. Advantageously, said rubber from said devulcanized rubber has a quantity of bound sulfur of at least 0.25% by weight, preferably between 0.25% and 10% by weight, more preferably between 0.25 and 5% by weight, even more preferably between 1 and 2% by weight, determined before addition to said composition. According to an even more advantageous embodiment, the devulcanized rubber is mainly from a recycling channel. In other words, used rubber will be recycled in that it will be processed to be supplied preferably in the form of granules, chips or powders. In addition, these types of rubber have, during their first use, been vulcanized and then transformed into granules, chips or powders for their recovery. The present invention should advantageously use recycled and vulcanized rubber in the form of granules, chips or powders, and possibly further devulcanized by (thermo)mechanical means, to be able to be part of the composition provided. It is thus possible for the rubber to consist of 100% by weight of recycled rubber, preferably devulcanized,which is particularly advantageous. In a preferred embodiment of the invention, said devulcanized rubber is derived from a vulcanized elastomer waste, preferably chosen from the group consisting of ethylene-propylene-diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR) and mixtures thereof, preferably in the form of chips, granules or powders. The devulcanized rubber derived from a waste comprising at least one elastomer waste is preferably in the form of chips, granules or powders. The EPDM, SBR, NR and IR elastomers represent the majority of the constituents found in elastomer waste. More specifically, these materials may originate in particular from waste truck tires, car tires, aircraft tires, seals or elastic membranes. In a preferred embodiment of the invention,said rubber is obtained by mixing an amount of between 50% and 90% by weight of devulcanized rubber, and an amount of between 10% and 50% by weight of virgin rubber, said % by weight being expressed relative to the total amount of rubber. Preferably, the devulcanized rubber comprises 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. Again and advantageously, the devulcanized rubber of the present invention is mainly (completely) derived from a recycling channel. In other words, used rubber will be recycled in that it will be processed to be supplied preferably in the form of granules, chips or powders. In addition, these types of rubber have, during their first use, been vulcanized and then transformed into granules,chips or powders for their recovery. The present invention should advantageously use recycled rubber in the form of vulcanized granules, chips or powders which will then have been devulcanized to be able to form part of the composition provided. According to another preferred embodiment, it may be useful to provide a composition based on ready-to-crosslink rubber which comprises at least 50%, preferably at least 51% of recycled rubber, preferably devulcanized to target certain applications. A mixture between devulcanized rubber and virgin rubber can thus be produced to provide the total rubber quantity. Other embodiments of the composition according to the invention are indicated in the appended claims. The invention also relates to a method for manufacturing a composition, preferably the composition according to the invention, based on ready-to-crosslink rubber, to form an extruded strip,said method comprising the following steps: a) Selection of a first fraction comprising at least 50% by weight, preferably at least 55% by weight, more preferably at least 60% by weight of a vulcanized elastomer waste selected from the group consisting of ethylene-propylene-diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR) and mixtures thereof, and wherein said vulcanized elastomer waste has a quantity of bound sulfur of at least 0.25% by weight, preferably between 0.25% and 10% by weight, more preferably between 0.25 and 5% by weight, b) Devulcanization by (thermo)chemical or (thermo)mechanical means of said first fraction with obtaining a devulcanized material, c) Optionally, a selection of a second fraction comprising at least 30 % by weight of a virgin elastomer selected from the group consisting of ethylene-propylene-diene monomer (EPDM),styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR) and mixtures thereof, d) Optionally, an addition of said devulcanized material to said second fraction; e) Mixing the material obtained in step b or step d, with at least one rubber activating agent and a vulcanizing agent which comprises sulfur, with formation of a devulcanized mixture corresponding to said ready-to-crosslink rubber-based composition; characterized in that said ready-to-crosslink rubber-based composition obtained during the mixing of step (e) comprises 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 2% by weight of free sulfur, relative to the total weight of said composition. The process of the invention makes it possible to recover vulcanized elastomer waste. This involves a specific devulcanization,preferably carried out by (thermo)mechanical means, preferably by shearing carried out in an extruder. This devulcanization will make it possible to break certain SS and / or CS bonds in the waste. The first fraction obtained can be transformed into chips, granules or powders before devulcanization. Thus, these vulcanized chips, granules or powders are then devulcanized according to the process of the invention. The first fraction can also be mixed with the second fraction depending on the intended applications. Preferably, the selection of the second fraction can comprise at least 10% by weight, preferably 20% by weight, more preferably 30% by weight of a virgin elastomer chosen from the group consisting of ethylene-propylene-diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR) and mixtures thereof. Alternatively,when the material obtained in step b is mixed with the vulcanizing agent and the activating agent, the material thus obtained can be further mixed with said second virgin fraction (virgin elastomer) which also comprises an activating agent and a vulcanizing agent, to form the ready-to-crosslink composition according to the invention. The method provided is efficient and easy to implement for a large number of sources of rubber waste, while allowing a revalorization thereof at a competitive cost. The devulcanization step b of the method is preferably carried out mechanically, more preferably thermomechanically, preferably by shearing in an extruder. In a preferred embodiment of the invention, the mixing step of step (e) is carried out by adding between 50% and 100% by weight of said devulcanized material,relative to the total weight of said composition. The devulcanization step b makes it possible to obtain a devulcanized material. It is possible in the process according to the invention to introduce all of this material into the mixing step of step (e). It is also possible to introduce only a portion thereof, of at least 50% by weight, preferably at least 55% by weight, more preferably at least 60% by weight, advantageously at least 70% by weight, more advantageously at least 85% by weight, relative to the total weight of said composition. In a preferred embodiment of the invention, the mixing step (step e) is carried out by adding between 50% and 90% by weight of said devulcanized material and between 10% and 50% by weight of said second fraction, relative to the total weight of said composition. Preferably, said second fraction is present in an amount of between 5 and 30% by weight, preferably between 5 and 20% by weight,more preferably between 5 and 15% by weight, even more preferably between 5 and 10% by weight, relative to the total weight of the composition ready for crosslinking. The addition of said second fraction makes it possible to introduce virgin rubber (or compound based on virgin material) into the mixing step e. The properties of the devulcanized mixture resulting from step (e) corresponding to the composition based on rubber ready for crosslinking will be modified following this addition. Depending on the expected properties, it is possible to vary the quantity of said second fraction added. In a preferred embodiment of the invention, the method is carried out by continuous extrusion to form said extruded strip. Thus, after the selection step(s),the first devulcanized fraction is mixed according to the steps included in the method according to the invention. The direct and successive combination consisting of devulcanizing and carrying out the mixing step (e) is particularly advantageous for the user who can offer a composition ready for crosslinking which is ready for use, read to be vulcanized to be recovered in a new final product. In a preferred embodiment of the invention, said vulcanized elastomer waste is in the form of granules, chips, or powders. According to an advantageous embodiment, said virgin elastomer is in the form of granules, chips, powders or strip. In a preferred embodiment of the invention, the method further comprises a step of cooling said devulcanized material. In a preferred embodiment of the invention,all the steps of the process are carried out successively so as to provide said composition ready for crosslinking in the form of an extruded strip which has a shelf life of more than 24 hours, which allows the composition to be easily stored in the event of delivery, without losing the stated properties. The shelf life corresponding to the period during which the composition can be stored before use. Other embodiments of the process according to the invention are indicated in the appended claims. Within the scope of the present invention, any singular article such as for example, "a", "an", "the", "the", "of", "of the" may be replaced by an article or an expression which designates a plural such as for example "at least 2", "at least 3", "several" etc. The word "include","contains" or any equivalent term or derivative may be replaced by "consisting of" in order to define a list or exclusive selection possibilities so as not to include other elements not mentioned in the expression used. When percentages (%) are indicated, these are expressed by weight, unless otherwise indicated. By crosslinking, according to the invention, is meant a crosslinking of a rubber or elastomer with sulfur, which is more specifically called vulcanization because sulfur is used as a vulcanizing agent. The term crosslinking which thus includes vulcanization also targets other types of crosslinking agent, such as peroxides. In the following, the terms crosslinking or decrosslinking will therefore respectively include the terms vulcanization and devulcanization. Rubber or rubbery material are common terms for naming elastomers or elastomeric materials,which are more technical terms, and these common terms will be used hereinafter, in this sense. The adjective "used" used in the present invention encompasses end-of-life, discarded or stored waste products. The expression "bound sulfur" must be understood as designating sulfur which is bound to another S atom (SS) or to a carbon atom (SC). This expression also relates to sulfur which could be designated as partially bound, in particular when a devulcanization step has been carried out. It is understood that this expression makes it possible to indirectly characterize the composition according to the invention, in that it contains a certain quantity of vulcanized and / or devulcanized elastomer waste. This bound sulfur can be demonstrated by elemental analysis of an intensively washed rubber composition, for example by Soxhlet extraction,using a sulfur solvent. The expression "free sulfur" must be understood as designating sulfur that does not bind to the elastomer / rubber present in the composition. This free sulfur may come from the sulfur-based vulcanizing agent and also, "optionally, from a vulcanization accelerator, for example CBS or TMTD. This free sulfur, in the presence or absence of the vulcanization accelerator, may be recovered in solution during intensive washing of said composition according to the invention, for example by Soxhlet extraction. The sulfur determination may be carried out by the PCS calcination method (standard NF EN 15408) and determination on the washing of the fumes. In a devulcanized rubber or devulcanized elastomer, some of the sulfur bonds are broken and remain partially bound. These bonds may 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 will break the bond that unites several macromolecular chains, but in the majority of cases, the sulfur will remain 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 the rubber by breaking the carbon-sulfur or sulfur-sulfur bonds. It is possible to determine the quantity of sulfur in a composition by elemental analysis. In order to ensure that the quantity of sulfur measured during an elemental analysis corresponds to the quantity of sulfur bound to the rubber, intensive washing can be carried out, for example by Soxhlet extraction,the rubber composition using a sulfur solvent. This washing solubilizes the free sulfur that may be present in the rubber composition. By bound sulfur, we mean the sulfur that can be detected by elemental analysis in a rubber composition thus washed. The sulfur determination can be carried out by the PCS calcination method (standard NF EN 15408) and determination on the washing of fumes The expression "virgin rubber" or "virgin elastomer" must be understood as designating a rubber that has not undergone vulcanization and which has therefore not been devulcanized. This constitutes the non-recycled virgin raw material. The first step a of the process according to the invention relates to a step of selecting the raw material. This step consists of selecting from a certain number of wastes, the raw material of interest which will constitute at least 50% by weight,preferably 51% by weight of a first fraction. This raw material is a vulcanized elastomer waste, read used. More precisely, if this elastomer waste is a used aircraft tire for example, it can be recycled and treated to be transformed into granules, chips or vulcanized powders. It is thus possible that this fraction also contains other compounds resulting from the composition used to manufacture aircraft tires. This reasoning can be applied to all types of recycled raw materials, such as truck tires, car tires, or even elastic soles, seals or membranes, preferably rubbers used in the construction or civil engineering sector. Each starting composition will be specific to the intended final product. In addition, the person skilled in the art knows GTR tires (in English for 'Ground Tire Rubber') which comprise an elastomer chosen from the group consisting of SBR, NR,SBR and their mixtures. The person skilled in the art also knows that these elastomer wastes can also include other compounds such as carbon black, steel, etc. Any compound used in the manufacture of this type of tire is thus included in the scope of the present invention. Grinding and granulating are the most used methods for recycling these tires. The devulcanization step makes it possible to partially break some of the SC and SS bonds present in the elastomer waste in order to make it suitable for the recovery provided for in the scope of the present invention. Although the person skilled in the art knows the devulcanization techniques, the present invention prefers to apply a devulcanization obtained by mechanical shearing, preferably under the action of heat (read, thermomechanical). This step can be followed by cooling and addition of the vulcanizing agent,of the activating agent and additives in order to provide a so-called "active" composition in that it only needs to be vulcanized at a certain vulcanization temperature. This devulcanization is preferably carried out with an extruder on a continuous conveyor belt. The devulcanization carried out within the framework of the present invention is advantageously carried out in the absence of devulcanizing agent or oils. The mixing step (e) of the present invention can be carried out in several ways. According to an advantageous embodiment, the rubber-based composition ready for crosslinking is mainly composed of rubber devulcanized in the presence of an activating agent (ZnO), a vulcanizing agent (S), and optionally a vulcanization accelerator (CBS) and optionally additives. Thus the mixing step (e) took place with the devulcanized material which mainly comprises devulcanized rubber. According to this embodiment,it is therefore not necessary to add virgin rubber. According to a preferred embodiment, it is possible to use a second fraction which comprises at least 30%, preferably a maximum of 20%, more preferably a maximum of 10% by weight of a virgin elastomer. In this case, the devulcanized material which contains devulcanized rubber is added to this second fraction. Then, the activating agent (ZnO), the vulcanizing agent (S), optionally the vulcanization accelerator (CBS) and optionally the additives are added to the mixture which contains the devulcanized material and the second fraction. According to a particularly advantageous embodiment of the invention, it is also possible to directly add the activating agent (ZnO), the vulcanizing agent (S),possibly the vulcanization accelerator (CBS) and possibly the additives to the second fraction. This can also be carried out with the devulcanized material which will thus include these same aforementioned elements. The mixing step (e) will consist of mixing the second fraction containing all the aforementioned elements with the devulcanized material, also,consisting of the aforementioned elements to form the rubber-based composition ready for crosslinking according to the invention. Example 1 Table 1 Compounds Quantity (wt. %) Rubber consisting of 100 92% devulcanized rubber from aircraft tires ZnO 4 S 1 CBS 1 Stearic acid 2 Example 2 Table 2 Compounds Quantity (wt. %) Rubber consisting of 75 92% devulcanized rubber from aircraft tires and 25% virgin rubber ZnO 4 S 1 CBS 1 Stearic acid 2 Example 3 Table 3 Compounds Quantity (wt. %) Rubber consisting of 90 92% devulcanized rubber from aircraft tires and 10% virgin rubber ZnO 4 S 1 CBS 1 Stearic acid 2 It is understood that the present invention is in no way limited to the embodiments described above and that many modifications may be made thereto without departing from the scope of the appended claims.,

Claims

CLAIMS 1. A rubber-based composition ready for crosslinking, preferably in the form of an extruded strip, said composition comprising: a) A total amount of rubber of between 30% and 90% by weight or between 30 and 99% by weight; b) A rubber activating agent in an amount of between 0.1% and 10% by weight; c) A vulcanizing agent which comprises sulfur, in an amount of between 0.5% and 5% by weight; characterized in that, said composition ready for crosslinking comprises a total amount of bound sulfur of at least 0.25% by weight, preferably between 0.25% and 10% by weight, more preferably between 0.25% and 5% by weight, and an amount of free sulfur of between 0.1% and 5% by weight, each aforementioned % by weight being expressed relative to the total weight of the composition. 2.Composition according to claim 1, having a viscosity of between 20 and 85 Mooney, preferably between 35 and 80 Mooney, measured according to ISO-289.

3. Composition according to claim 1 or 2, further comprising a rubber vulcanization accelerator in an amount of between 0.5% and 5% by weight, relative to the total weight of the composition.

4. Composition according to any one of the preceding claims, further comprising additives chosen from the group consisting of reinforcing fillers, diluting fillers, fatty acids, preferably stearic acid,. plasticizers, anti-ozone protectors, antioxidants, oils and mixtures thereof.

5. A composition according to any preceding claim, wherein the activating agent is selected from the group consisting of zinc oxide.

6. A composition according to any preceding claim, wherein said rubber is derived from a devulcanized rubber which is present in an amount of between 50% and 100% by weight relative to the total weight of rubber.

7. A composition according to claim 6, wherein said devulcanized rubber is derived from a vulcanized elastomer waste selected from the group consisting of ethylene-propylene-diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR) and mixtures thereof, preferably in the form of chips, granules or powders. 8.Composition according to any one of the preceding claims, wherein said rubber is obtained by mixing an amount of between 50% and 90% by weight of devulcanized rubber and an amount of between 10% and 50% by weight of virgin rubber, said % by weight being expressed relative to the total amount of rubber.

9. A method of manufacturing a rubber-based composition ready for crosslinking, to form an extruded strip, said method comprising the following steps: a) Selecting a first fraction comprising at least 50% by weight of a vulcanized elastomer waste selected from the group consisting of ethylene-propylene-diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR) and mixtures thereof, and wherein said vulcanized elastomer waste has an amount of sulfur. bound at least 0.25% by weight, preferably between 0.25% and 10% by weight, more preferably between 0.25% and 5% by weight, b) Devulcanization by (thermo)chemical or (thermo)mechanical means of said first fraction with obtaining a devulcanized material, c) Optionally, a selection of a second fraction comprising at least 30% by weight of a virgin elastomer chosen from the group consisting of ethylene-propylene-diene monomer (EPDM), styrene-butadiene (SBR), natural rubber (NR), synthetic isoprene (IR) and their mixtures, d) Optionally, an addition of said devulcanized material to said second fraction; e) Mixing the material obtained in step b or step d, with at least one rubber activating agent and a vulcanizing agent which comprises sulfur with formation of a devulcanized mixture corresponding to said rubber-based composition ready for crosslinking;characterized in that said ready-to-crosslink rubber-based composition obtained during the mixing of step (e) comprises 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 2% by weight of free sulfur, relative to the total weight of the composition.

10. A method according to claim 9, wherein the mixing step of step (e) is carried out by adding between 50% and 100% by weight of said devulcanized material, relative to the total weight of said composition.; 11. A method according to claim 9 or 10, wherein the mixing step (e) is carried out by adding between 50% and 90% by weight of said devulcanized material and between 10% and 50% by weight of said second fraction, relative to the total weight of said composition.

12. A method according to any one of claims 9 to 11, being carried out by continuous extrusion to form said extruded strip ready for crosslinking.

13. A method according to any one of claims 9 to 12, wherein said vulcanized elastomer waste or said virgin elastomer is in the form of granules, chips or powders.

14. A method according to any one of claims 9 to 13, further comprising a step of cooling said devulcanized material. 15.A method according to any one of claims 9 to 14, wherein all the steps of the method are carried out successively so as to provide said composition ready for crosslinking in the form of an extruded strip which preferably has a shelf life of at least 24 hours.