Transmission belt with reduced environmental impact

Abstract

The invention relates to a transmission belt (10) comprising a body provided with at least one elastomer-based tooth (B), said at least one tooth comprising: - an ethylene-propylene-diene monomer in a proportion of between 85 and 100 parts, per 100 parts of elastomer; - natural rubber in a proportion at most equal to 15 parts; - and regenerated carbon black in a proportion of between 20 and 70 parts.

Description

Description TITLE: LOW ENVIRONMENTAL IMPACT DRIVE BELT Technical field of the invention

[0001] The present invention relates to a transmission belt, in particular a transmission belt comprising a mixture of materials from renewable or sustainable sources in order to have a reduced environmental impact. Technological background

[0002] Transmission belts, of all shapes and sizes, are used in association with motorized systems in a wide variety of applications, for example in motor vehicles, industrial machinery or household appliances.

[0003] Currently, drive belts are manufactured from raw materials derived primarily from hydrocarbon processing, such as petroleum. Specifically, belts are made from elastomeric rubbers like chloroprene (CR), polybutadiene (BR), styrene-butadiene (SBR), ethylene-propylene-diene monomer (EPDM), hydrogenated polybutadiene acrylonitrile (HNBR), or polyurethane (PU), all of which are predominantly petroleum-based. They may also include reinforcing fillers such as carbon black produced from hydrocarbon combustion and / or synthetic fibers, mainly polyamide, polyester, or aramid.

[0004] However, the carbon footprint of these belts is high. Carbon footprint is defined as an indicator aimed at measuring the impact of a product - in this case the belts - on the environment, and more specifically the greenhouse gas emissions linked to this product, this indicator being expressed in kilograms of carbon dioxide equivalent per kilogram of product (kgCO2e / kg).

[0005] Furthermore, the treatment of production waste and used belts can be problematic due to the emission of toxic gases during their combustion, particularly with chloroprene-based belts which are widely used for the good compromise it offers in terms of mechanical strength, aging and adhesion performance.

[0006] To reduce the carbon footprint of belts, solutions have been proposed. Belts made primarily from natural rubber have, for example, been proposed in document EP-A1-2584217.

[0007] However, belts made primarily of natural rubber do not meet the same mechanical performance requirements. This type of belt is particularly limited in terms of resistance to thermal aging and ozone. Electric motors are known to be sources of ozone, making belts made primarily of natural rubber unsuitable for this type of application.

[0008] Also, one objective of the invention is to offer a functional transmission belt that reduces environmental impact, particularly carbon footprint.

[0009] Another objective of the invention is to provide a transmission belt with physical and mechanical properties similar to current references. Summary of the invention

[0010] It is therefore proposed a transmission belt comprising a body with at least one elastomer-based tooth, this tooth comprising: an ethylene-propylene-diene monomer in a proportion of between 85 and 100 parts, for 100 parts of elastomer; - natural rubber in a proportion not exceeding 15 parts, for 100 parts of elastomer; - a regenerated carbon black in a proportion of between 20 and 70 parts.

[0011] Thus, thanks to the invention, a reduction in the carbon footprint of the drive belt is ensured. Indeed, the carbon black used as a belt reinforcement element is regenerated; that is to say, it is not produced directly from hydrocarbons, but rather this regenerated carbon black is produced from pre-processed elastomeric materials that can come, for example, from used tires or belts, or from any type of product made primarily of rubber. The regenerated carbon black is therefore derived from pre-existing and already processed products and is used for another This application, within the scope of the invention, provides a functional and usable belt. Furthermore, the presence of regenerated carbon black also reduces the presence of polycyclic aromatic hydrocarbons (PAHs), which are natural constituents of coal and petroleum, among other things.

[0012] The process according to the invention may include one or more of the following features, taken individually or in combination with each other: at least one tooth comprises non-regenerated carbon black in a defined proportion such that a total proportion of carbon black, corresponding to an addition of the proportion of regenerated carbon black and the proportion of non-regenerated carbon black, is at most 80 parts, for example between 50 and 80 parts, preferably between 55 and 80 parts and even more preferably between 55 and 75 parts; - at least one tooth comprises cellulose fibers in a proportion at least equal to 3 parts; - the proportion of cellulosic fibers is between 3 and 30 parts, preferably between 5 and 20 parts; - the cellulosic fibers are chosen from wood fibers such as spruce or oak fibers, cotton fibers, flax fibers, rice fibers, hemp fibers or a combination of at least two of the aforementioned types of cellulosic fibers; at least one tooth comprises a regenerated mixture of ethylene-propylene-diene monomer in a proportion not exceeding 30 parts; - the proportion of regenerated carbon black is between 25 and 65 parts, and preferably between 30 and 65 parts; - the proportion of natural rubber is between 5 and 15 parts, and preferably between 8 and 12 parts; - the tooth is devoid of chloroprene; - the tooth is free of any halogenated compound; - the belt comprises a plurality of cables embedded in the body of the belt, the cables being based on polyamide, polyester, aramid, glass, carbon or bio-based or recycled yarns; the body is provided with at least one longitudinal tooth, the transmission belt being an asynchronous belt; the body is provided with a plurality of transverse teeth, the transmission belt being a synchronous belt. Brief description of the figures

[0013] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which:

[0014] Figure 1 shows a schematic view of a transmission belt according to the invention, for example a ribbed belt,

[0015] Figure 2 shows a schematic view of another transmission belt according to the invention, for example a synchronous belt,

[0016] Figure 3 shows a schematic view of another transmission belt according to the invention, by a belt with a single tooth,

[0017] Figure 4 shows a schematic view of a test bench equipped with an unbalanced weight J for measuring the service life of a belt,

[0018] Figure 5 shows a schematic view of a test bench equipped with an unbalanced weight H for measuring the service life of a belt.

[0019] Figure 6 represents a graph showing the evolution of the electrical resistance of the tooth of a belt as a function of the rate of non-regenerated carbon black (CB) according to the number of parts of regenerated carbon black (rCB) in the composition. Detailed description of the invention

[0020] In what follows, reference is made to carbon black. For the purposes of this invention, it is important to note that carbon black is divided into two categories: non-reclaimed carbon black and reclaimed carbon black. The distinction between these two categories is explained later.

[0021] The invention relates to a transmission belt 10 comprising a body having at least one elastomer-based tooth B which includes: - ethylene-propylene-diene monomer (EPDM) in a proportion of between 85 and 100 parts, for 100 parts of elastomer; - natural rubber in a proportion not exceeding 15 parts, for 100 parts of elastomer; - a regenerated carbon black in a proportion of between 20 and 70 parts.

[0022] According to the standards body ASTM International (American Society for Testing and Materials), and in particular the standard designated by ASTM D3053-23 (published on February 28, 2023), relating to its terminology, carbon black (CB for carbon black) is an engineered material, consisting mainly of elemental carbon, produced by the partial combustion or thermal decomposition of hydrocarbons, and existing in the form of acinar morphology aggregates which are composed of spheroidal primary particles (also designated by the term "nodules") which exhibit a uniformity of size of primary particles within a given aggregate and a turbostratic stratification within the primary particles.

[0023] ASTM D3053-23 provides further information characterizing the bonds between particles. Primary particles, or nodules, are linked together by covalent bonds and organize themselves into "clusters" to form complex three-dimensional entities called aggregates. These aggregates subsequently assemble into clusters and form agglomerates under the influence of attractive Van der Waals forces.

[0024] Furthermore, from a geometric point of view, the turbostratic structure of carbon black particles exhibits graphene sheets, arranged in a more or less graphitic manner in parallel stacking, but whose orientation relative to adjacent sheets is random. The graphitic crystallites are often misaligned with each other within the primary particle, leading to a disordered state of the carbon black microstructure. It is also known that carbon black, as defined above, possesses conductive properties which, in the application of belts, ensure electrical conduction through the belt. The belt's conductivity will vary depending on the size of the carbon black particles; in particular, conductivity will tend to increase as the particle size decreases.The conductivity of carbon black can also be increased by increasing the number of polyaromatic rings and decreasing the number of aliphatic groups on the surface of the carbon black particles. This is described in particular in Pantea D., Darmstadt H., Kaliaguine S., Sümmchen L., Roy C, Carbon 39, 1147-1158 (2001).

[0025] ASTM D8178-22 (published on July 4, 2022) defines the terminology for recovered carbon black (rCB). Recovered carbon black is a solid product regenerated by the thermal decomposition of elastomeric products containing carbon black. It is free of yarn and fabric and, once ground, generally imparts semi-reinforcing properties to an elastomer.

[0026] It is understood that a carbon black meeting the ASTM D3053-23 standard and therefore not the ASTM D8178-22 standard, can be defined as a non-regenerated carbon black.

[0027] Thus, according to the definitions provided by these two standards, non-reclaimed carbon black is produced directly from hydrocarbons, such as petroleum, while reclaimed carbon black is not produced directly from hydrocarbons but from elastomeric products that have already been processed and contain carbon black. These processed elastomeric products are most often used elastomeric products such as tires or belts.

[0028] Currently, two types of industrialized thermal processes exist for recovering carbon content, for example from an end-of-life tire: pyrolysis and vapor-thermolysis. The recovered carbon content is then considered regenerated carbon black as defined by the ASTM D8178-22 standard.

[0029] In the invention, the regenerated carbon black can therefore be obtained from a pyrolysis or vapo-thermolysis treatment of used elastomer products.

[0030] In the invention, the reclaimed carbon black has the advantage of reducing the presence of polycyclic aromatic hydrocarbons (PAHs) in the belt because the reclaimed carbon black contains few of them. The low proportion of PAHs in the reclaimed carbon black was notably described in Anjum, A. (2021), Recovered carbon black from waste tire pyrolysis, Characteristics, performance, and valorisation, [PhD Thesis - Research UT, graduation UT, University of Twente], University of Twente; Doi: https: / / doi.org / 10.3990Z1.9789036552899. The pyrolysis process used allows for such a reduction of PAHs, as described in CJ Norris, A. Lopez Cerdân, P. ter Haar; Understanding Recovered Carbon Black. Rubber Chemistry and Technology 1 April 2023; 96 (2): 196-213; doi: https: / / doi.org / 10.5254 / rct.23.76956. These PAHs are natural constituents of petroleum, for example, and are found in compounds derived directly from it, such as non-reclaimed carbon black. PAHs are compounds generally classified as dangerous to health, or even carcinogenic.

[0031] Preferably, the proportion of regenerated carbon black is between 25 and 65 parts, and even more preferably is between 30 and 65 parts.

[0032] It has been observed that a belt containing only recycled carbon black, i.e., without any non-recycled carbon black, is naturally electrically insulating. "Electrically insulating" is understood to mean the definition given by ISO 1813:2014, published in February 2014, regarding electrical resistance.

[0033] Indeed, conductivity decreases with increasing levels of non-carbonaceous elements on the surface of carbon black particles and / or pyrolyzed polymer residues. These non-carbonaceous elements can be, for example, impurities such as oxides like zinc oxide, silica, or sulfur. These non-carbonaceous elements, or impurities, originate from components commonly used in the elastomeric materials / products recovered to produce regenerated carbon black.

[0034] Advantageously, regenerated carbon black contains these impurities in a proportion, by mass, of between 5% and 30%.

[0035] This characteristic, namely being electrically insulating, represents an advantage for certain specific applications. For example, an electrically insulating belt, that is, one that conducts little or no electricity, may be desirable for household appliances that require such belts due to the absence of a ground wire at the motor. This prevents the propagation of electricity to other parts of the appliance that the user might touch. In other words, these insulating belts help prevent electrocution.

[0036] However, this can be problematic for other applications requiring minimal electrical conduction through the belt.

[0037] Also, each tooth B of the belt 10 according to the invention can comprise both conventional carbon black, i.e., non-regenerated, and regenerated carbon black. Advantageously, this non-regenerated carbon black is present in a defined proportion such that a total proportion of carbon black, which corresponds to the sum of the proportions of regenerated carbon black and non-regenerated carbon black, is at most equal to 80 parts.

[0038] For example, for 20 parts of recycled carbon black, there may be 60 parts of non-recycled carbon black. It is also possible for 20 parts of recycled carbon black to have fewer than 60 parts of non-recycled carbon black, such as 50 or 40 parts, or even less. For example again, for 30 parts of recycled carbon black, there may be 50 parts of non-recycled carbon black. It is also possible for 30 parts of recycled carbon black to have fewer than 50 parts of non-recycled carbon black, such as 40 or 30 parts, or even less. Again, for example, for 40 parts of recycled carbon black, there may be 40 parts of non-recycled carbon black. It is also possible for 40 parts of regenerated carbon black to have less than 40 parts of non-regenerated carbon black, such as 30 parts or 20 parts of non-regenerated carbon black, or even less.For example, for 70 parts of recycled carbon black, there could be 10 parts of non-recycled carbon black. It is also possible for 70 parts of recycled carbon black to contain fewer than 10 parts of non-recycled carbon black, such as 5 parts or even 1 part.

[0039] For example, the total proportion of carbon black can be between 50 and 80 parts, preferably between 55 and 80 parts, and even more preferably between 55 and 75 parts.

[0040] Tooth B of belt 10 may have a proportion of recycled carbon black less than 70 parts, for example 65 parts recycled carbon black, while containing no non-recycled carbon black. In other words, it may contain less than 70 parts recycled carbon black and 0 parts non-recycled carbon black.

[0041] Incorporating a proportion of non-reclaimed carbon black allows the belt's conductivity to be adjusted according to the performance requirements of a given application. Therefore, the higher the proportion of non-reclaimed carbon black in the total carbon black content, the higher the belt's conductivity.

[0042] The environmental impact will, admittedly, be greater than for a belt without conventional carbon black, but will still remain lower than the environmental impact of a reference belt. Furthermore, the environmental impact of such a belt—with a blend of regenerated carbon black and non-regenerated carbon black - can be offset and improved by adding other regenerated, recycled or renewable source elements, as described later.

[0043] Furthermore, the inventors observed that a total carbon black proportion exceeding 80 parts could lead to difficulties in manufacturing the transmission belt. Indeed, the proportion of carbon black influences, among other things, the viscosity of the elastomer, which, beyond 80 parts carbon black, no longer mixes sufficiently to achieve the desired properties.

[0044] Each tooth B of the belt 10 according to the invention may also comprise a regenerated EPDM-based blend, referred to as regenerated EPDM. A regenerated EPDM-based blend is defined as an EPDM blend derived from the recycling of a previously processed elastomer product containing EPDM elastomer, and which is therefore not produced directly from hydrocarbons such as petroleum. This elastomer product may be a used belt or other material, for example. The EPDM elastomer contained in the used elastomer product may be conventional EPDM elastomer, i.e., directly derived from the processing of hydrocarbons, bio-based materials, or already recycled.

[0045] The term EPDM blend refers to all the components that make up a vulcanized rubber based on EPDM elastomer. This includes at least the EPDM elastomer, reinforcing fillers, plasticizers and / or other additives.

[0046] During the production of the regenerated EPDM blend, the initial EPDM blend is thermo-mechanically decomposed, notably by shearing, which breaks the vulcanization bonds and even the polymer chains. Thus, at least some of the components of the initial EPDM blend can be recovered in the regenerated EPDM blend.

[0047] This has the advantage of further improving the reduction of the environmental impact and carbon footprint of belt 10.

[0048] Advantageously, the regenerated EPDM has a proportion of no more than 30 parts in tooth B of belt 10. This ensures the stability of the properties of the total EPDM blend obtained, regardless of the variability of the waste / products used to produce the regenerated EPDM blend. Tooth B of belt 10 thus has a total EPDM proportion that corresponds to the sum of conventional or non-regenerated EPDM and regenerated EPDM from the The regenerated EPDM blend is as described previously. The total elastomer content is 100 parts. It is understood that for a given proportion of EPDM, the proportion of regenerated EPDM is equal, so the total EPDM content is 100 parts. In other words, when the belt 10 comprises both conventional EPDM and regenerated EPDM, the total EPDM content is constant and approximately equal to 100 parts.

[0049] Thus, the proportions of EPDM from the regenerated EPDM blend are defined by the composition of the source material used. The remaining proportions consist mainly of reinforcing or non-reinforcing fillers such as carbon black, or clear fillers which, depending on the composition of the source material, may be added to the proportion of carbon black. Clear fillers include reinforcing, semi-reinforcing, or inert fillers such as, for example, silica, calcium carbonate, kaolin, or talc.

[0050] Natural rubber (NR) in the composition of tooth B of belt 10 offers the advantage of further reducing the environmental impact and carbon footprint of belt 10. Natural rubber has a proportion of no more than 15 parts in the mixture. The inventors observed that a higher proportion of natural rubber in the belt tooth leads to a degradation of mechanical properties after aging.

[0051] Natural rubber can have a proportion of between 5 and 15 parts, and preferably between 8 and 12 parts.

[0052] Advantageously, each tooth B of the transmission belt 10 is free of chloroprene (CR). More generally, the entire belt 10 is advantageously free of chloroprene. This has the advantage of reducing the density of the elastomer and thus decreasing the linear mass of the belt while maintaining the same functionality. An average density of 1.3 ± 0.05 was observed for the tooth of a reference belt containing chloroprene, and an average density of 1.12 ± 0.05 for the tooth of a belt without chloroprene according to the invention.

[0053] Furthermore, as mentioned in the introduction, chloroprene releases toxic gases when burned, which pose a problem for the treatment of waste containing it, such as used belts. In addition, a belt free of chloroprene also improves its environmental impact.

[0054] Advantageously, the transmission belt 10 is free of any halogenated compounds, that is, any compound containing at least one atom belonging to the halogen group of elements in the periodic table (fluorine, chlorine, bromine, iodine, and astatine). This offers advantages similar to those obtained without chloroprene. In addition, it provides a preventative benefit regarding the emission of any potentially hazardous halogenated compounds.

[0055] In order to ensure that the materials used in the composition of the tooth(s) B of the belt 10 are free from any halogenated compound, strict conditions may be taken upstream with suppliers and / or in the choice of sources of supply.

[0056] Renewable functional fillers are used to reinforce the elastomer. These fillers can be cellulosic fibers, including but not limited to cotton, flax, rice, hemp, and wood fibers such as spruce or oak, or a combination of these types of fillers. Because these fillers are derived from plant sources, and are therefore renewable, they also help reduce the belt's carbon footprint. Cellulosic fibers serve as reinforcing fillers. In particular, these fibers introduce anisotropy into the blend and contribute to improving low-stretch properties.

[0057] Each tooth B of the belt may comprise cellulosic fibers in a proportion of at least 3 parts. Advantageously, the proportion of cellulosic fibers is between 3 and 30 parts, preferably between 5 and 20 parts.

[0058] Cellulosic fibers can replace, at least partially, reclaimed carbon black (rCB) in the mixture. They can also replace, or substitute, at least partially, unreclaimed carbon black (CB), i.e., conventional carbon black. In this way, in the proportions described above, cellulosic fibers make it possible to avoid adding excessive amounts of carbon black (reclaimed or unreclaimed), which, in total proportions exceeding a certain threshold, can lead to viscosity problems in the mixture, as previously described.

[0059] Cellulosic fibers thus contribute to reducing environmental impact and also to reducing the proportion of PAHs in the mixture by replacing carbon blacks.

[0060] Other fillers can be used as a replacement for regenerated carbon black. Lignin can be used, for example.

[0061] The belt 10 according to the invention is thus designed to include a maximum of materials from renewable and / or sustainable sources.

[0062] The composition may include at least one peroxide compound in a proportion of between 1 and 15 parts. The peroxide compound(s) are used for the vulcanization of the rubber. This peroxide compound(s) may be selected, without limitation, from [1,3-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide, [1,4-phenylenebis(1-methylethylidene)]bis[tert-butyl] peroxide, 4,4-bis(tert-butyldioxy)butyl valerate peroxide, or a combination of at least two of the aforementioned compounds.

[0063] Peroxide compounds also have the advantage of offering better resistance to aging for a transmission belt containing natural rubber (NR).

[0064] The vulcanization system can alternatively be composed of sulfur, accelerators, co-agents or metal oxides.

[0065] With reference to Figure 1, the belt 10 can be an asynchronous belt, for example, a poly-V® type belt with a profile selected, without limitation, from profiles H, J, K, L, or M, or another type. These profiles are defined by ISO 9982:2021, published in September 2021. The belt 10 can also be a synchronous belt, as illustrated in Figure 2. Figure 3 shows, for example, another type of belt 10, with a single tooth B.

[0066] The belt 10 according to the invention may also include cables C embedded in the body of the belt 10. These cables C may be made of polyamide, polyester, aramid, glass, carbon, or bio-based or recycled fibers. "Bio-based" means material derived from renewable organic matter of plant or animal origin. "Recycled" means material that has undergone further processing after being collected and reprocessed. It is understood that the aforementioned materials may be recycled materials.

[0067] The transmission belt 10, which includes at least one elastomer-based tooth, is obtained by a conventional manufacturing / molding process.

[0068] Example(s) of implementation:

[0069] The invention is described in more detail through various embodiments presented in Table 1. The examples presented concern ribbed belts, which are asynchronous belts. These examples are not limiting.

[0070] Table 1 presents several example compositions (AE) of belt teeth according to the invention compared to a reference belt which includes at least one tooth based on chloroprene and polybutadiene and carbon black.

[0071] It should be noted that conventional carbon black (CB), i.e., non-regenerated carbon black, exhibits superior strengthening properties compared to regenerated carbon black (rCB). In other words, for given mechanical properties, less conventional carbon black is required than regenerated carbon black.

[0072] [Table 1]

[0073] Examples A to E show a variation in the proportions of regenerated and non-regenerated carbon black. Furthermore, examples C and D include natural rubber (NR).

[0074] Example E does not contain any non-reclaimed carbon black, meaning carbon black directly derived from hydrocarbons. In other words, the belt tooth in Example E contains only reclaimed carbon black. As described above, such a belt is electrically insulating.

[0075] When non-regenerated carbon black (CB) is used in the composition, it can typically be standard carbon black of type N115 as defined in ASTM D1765-23b, published in January 2024. It is also possible to use non-regenerated carbon black of type N330 or N550.

[0076] Carbon blacks (non-reclaimed) are classified into families according to their particle size, from N110 (the finest) to N990. The finer the carbon black, the more it mechanically strengthens the mixture and the more it increases the mixture's conductivity. N330 or N550 types can therefore be considered intermediate choices.

[0077] As mentioned previously, the tooth composition may include cellulose fibers. Example A does not contain cellulose fibers. In contrast, examples B through E include cellulose fibers in a proportion of at least 3 parts, and preferably in a proportion between 5 and 20 parts.

[0078] Typically, the compositions of the various examples include a vulcanizing system, at least one plasticizer, and at least one processing agent. Clear fillers and protectants may also be present.

[0079] The vulcanization system may be chosen, without limitation, from peroxide compounds, sulfur, accelerators, co-agents or metal oxides in a proportion of between 1 and 15 parts.

[0080] The plasticizer may be chosen, without limitation, from an aromatic, paraffinic or naphthenic oil in a proportion of between 5 and 20 parts.

[0081] The processing agent is in a proportion of between 1 and 10 parts. The processing agent(s) may be chosen, without limitation, from stearic acid, hydrocarbon resins or paraffin.

[0082] Clear fillers can be reinforcing, semi-reinforcing or inert fillers such as, for example, silica, calcium carbonate, kaolin or talc. They can be present in a proportion not exceeding 20 parts.

[0083] The protectants are chosen, without limitation, from among amines, phenols or phosphates, or from among protective waxes, in a proportion not exceeding 5 parts.

[0084] Table 2 presents other belt tooth compositions which are not part of the invention but are given as elements of comparison, in particular to show an effect of a variation in the proportion of natural rubber in the composition.

[0085] [Table 2]

[0086] In connection with Table 3, described below, it is shown that for high proportions of natural rubber in the belt tooth(s), the physical and mechanical properties of the belt exhibit degraded performance.

[0087] Table 3 presents various physical and mechanical properties that were determined for the different belts mentioned above. Table 3 includes measurements of density, electrical resistance, and service life for the different examples described in Tables 1 and 2.

[0088] Density is measured according to ISO 2781:2018, published in June 2018.

[0089] Electrical resistance is determined according to ISO 1813:2014, published in February 2014. In this standard, electrical resistance is given in Ohm (Q) for a given belt length and for a given number of teeth, here 5 teeth.

[0090] Service life is generally measured by rotating pulleys. Depending on the intended application, at least one pulley is fitted with an unbalanced weight for testing. The following tests were conducted with unbalanced weights designed for belts with teeth featuring J or H profiles, as defined by ISO 9982:2021. For convenience, a type J unbalanced weight will be used for belt teeth with a J profile, and a type H unbalanced weight for belt teeth with an H profile.

[0091] Figure 4 illustrates a test bench 20 with a type J unbalanced weight 21. In this configuration, the drive pulley M has a diameter of 15 mm and the driven pulley R has a diameter of 300 mm. The drive pulley M has a rotational speed of 1500 rpm. The unbalanced weight 21 is characterized by an 8.6 kg imbalance mass located 300 mm from the axis of rotation of pulley R. The belt The belt is rotated on the pulleys according to a predefined cycle: 60 seconds clockwise, then a 2-second pause, then 60 seconds counterclockwise, then a 2-second pause, and so on until the belt breaks. The test is performed at room temperature.

[0092] Figure 5 illustrates a test bench 30 with an H-type unbalanced weight 31. In this configuration, the drive pulley M has a diameter of mm and the driven pulley R has a diameter of 520 mm. A tensioner roller G is positioned between the two pulleys and has a diameter of 50 mm. The drive pulley rotates at a speed of 3000 rpm. The unbalanced weight 31 is characterized by an 8.6 kg imbalance mass located 300 mm from the axis of rotation of pulley R. The belt is rotated on the pulleys according to a predefined cycle: 15 seconds counterclockwise, then 72 seconds clockwise, and so on until the belt breaks. The test is carried out under controlled temperature, specifically ensuring that the center of the driven pulley R is at a temperature approximately equal to 100°C.

[0093] With reference to Table 3, the reference belt, which contains chloroprene and non-regenerated carbon black, has a density of approximately 1.26 and an electrical resistance of approximately 10 -4 MO. During testing, the lifespan of such a belt is measured at 155 hours with an imbalance H and 325 hours with an imbalance J.

[0094] The absence of chloroprene in the belt composition ensures a reduction in belt density, as observed for all examples.

[0095] Electrical resistance can be adjusted by varying the proportions of recycled and non-recycled carbon black. For example, Figure 6 shows a graph illustrating the change in electrical resistance as a function of the proportion of non-recycled carbon black (CB), here type N-115, and the proportion of recycled carbon black (rCB). The proportion of non-recycled carbon black (CB) is defined as the ratio of the number of parts of non-recycled carbon black (CB) to the sum of the parts in the belt tooth. Generally, electrical resistance decreases as the proportion of non-recycled carbon black (CB) increases. Conversely, for a given proportion of non-recycled carbon black (CB), electrical resistance decreases as the proportion of recycled carbon black (rCB) increases.

[0096] [Table 3] measured with an H-type imbalance, is at least equivalent to or greater than the service life of the reference belt.

[0098] The service life of the belt of example E according to the invention, measured with a type J unbalance, is equivalent to or greater than the service life of the reference belt.

[0099] Comparing compositions 1 and 2, on the one hand, and example E, on the other, demonstrates the influence of the natural rubber content on the various properties of the belt tooth. It can be observed that the measured service life with an imbalance J decreases as the proportion of natural rubber increases, ranging from 0.20 to 50 parts. It can be deduced that a high proportion of natural rubber in the composition impairs the stability of the belt tooth(s), thus reducing its service life. Although other parameters vary in compositions 1 and 2, such as the proportion of regenerated carbon black, these variations are considered to have a negligible impact on the observed degradation, as they remain within the range defined by the invention.

[0100] It has also been observed that the carbon footprint is reduced for belts without chloroprene. The reduction in carbon footprint may This can be further improved by increasing the proportion of recycled carbon black and / or natural rubber and / or cellulosic fibers in the composition. However, depending on the needs and intended application, adjustments must be made to the proportions used in the composition. Indeed, in addition to improving the belt's carbon footprint, there is a direct impact on the belt's physical, particularly electrical, and mechanical properties, as described previously.

Claims

Demands [1] Transmission belt (10) comprising a body having at least one elastomer-based tooth (B), said at least one tooth comprising: - an ethylene-propylene-diene monomer in a proportion of between 85 and 100 parts, for 100 parts of elastomer; - natural rubber in a proportion not exceeding 15 parts, for 100 parts of elastomer; - a regenerated carbon black in a proportion of between 20 and 70 parts. [2] Belt (10) according to claim 1, wherein said at least one tooth (B) comprises non-regenerated carbon black in a defined proportion such that a total proportion of carbon black, corresponding to an addition of the proportion of regenerated carbon black and the proportion of non-regenerated carbon black, is at most 80 parts, for example between 50 and 80 parts, preferably between 55 and 80 parts and even more preferably between 55 and 75 parts. [3] Belt (10) according to any one of claims 1 or 2, wherein said at least one tooth comprises cellulosic fibres in a proportion of at least 3 parts. [4] Belt (10) according to claim 3, wherein the proportion of cellulosic fibres is between 3 and 30 parts, preferably between 5 and 20 parts. [5] Belt (10) according to any one of claims 3 or 4, wherein said cellulosic fibres are selected from wood fibres such as spruce fibres or oak fibres, cotton fibres, flax fibres, rice fibres, hemp fibres or a combination of at least two of the aforementioned types of cellulosic fibres. [6] Belt (10) according to any one of claims 1 to 5, wherein said at least one tooth (B) comprises a regenerated mixture of ethylene-propylene-diene monomer in a proportion not exceeding 30 parts. [7] Belt (10) according to any one of claims 1 to 6, wherein the proportion of regenerated carbon black is between 25 and 65 parts, and preferably between 30 and 65 parts. [8] Belt (10) according to any one of claims 1 to 7, wherein the proportion of natural rubber is between 5 and 15 parts, and preferably between 8 and 12 parts. [9] Belt (10) according to any one of claims 1 to 8, wherein said tooth (B) is devoid of chloroprene. [10] Belt (10) according to any one of claims 1 to 9, wherein said tooth (B) is devoid of any halogenated compound. [11] Belt (10) according to any one of claims 1 to 10, comprising a plurality of cables (C) embedded in the body of said belt, said cables being based on polyamide, polyester, aramid, glass, carbon or bio-based or recycled yarns. [12] Belt (10) according to any one of claims 1 to 11, wherein the body is provided with at least one longitudinal tooth (B), said transmission belt being an asynchronous belt. [13] Belt (10) according to any one of claims 1 to 11, wherein the body is provided with a plurality of transverse teeth (B), said transmission belt being a synchronous belt.

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