LOW ENVIRONMENTAL IMPACT DRIVE BELT

Abstract

Transmission belt (10) comprising a body having at least one tooth (B) made of elastomer, said at least one tooth comprising: - ethylene-propylene-diene monomer in a proportion of between 85 and 100 parts per 100 parts of elastomer; - natural rubber in a proportion not exceeding 10 parts; - reclaimed carbon black in a proportion of between 20 and 70 parts. Figure for the abbreviation: Figure 1

Description

Title of the invention: 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 application areas, for example in motor vehicles, industrial machinery or household appliances.

[0003] Currently, transmission belts are manufactured from raw materials derived primarily from the processing of hydrocarbons such as petroleum. In particular, belts are based on elastomeric rubbers such as 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-derived. They may also include reinforcing fillers such as carbon blacks derived from hydrocarbon combustion and / or synthetic fibers, mainly based on 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 - here the belts - on the environment, and more particularly the greenhouse gas emissions related to this product, this indicator being then expressed in kilograms of carbon dioxide equivalent per kilogram of product (kgCO2e / kg).

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

[0006] In order 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 requirements in terms of mechanical performance. This type of solution is particularly limited in terms of resistance to thermal aging and ozone. However, it is known that electric motors are sources of ozone, which makes belts made primarily of natural rubber unsuitable for this type of application.

[0008] Also, an objective of the invention is to provide a functional transmission belt that reduces environmental impact, in particular carbon footprint.

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

[0010] A transmission belt is therefore proposed comprising a body having 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 transmission belt. Indeed, the carbon black used as a belt reinforcement element is regenerated, meaning it is not produced directly from hydrocarbons. Rather, this regenerated carbon black is produced from pre-processed elastomeric materials, which can come, for example, from used tires or belts, or any type of product consisting primarily of rubber. The regenerated carbon black is therefore derived from pre-existing and already processed products and is used for another purpose which, 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 method according to the invention may comprise 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 the total proportion of carbon black, corresponding to the sum of the proportion of regenerated carbon black and the proportion of non-regenerated carbon black, is at most 80 parts, per example between 50 and 80 shares, preferably between 55 and 80 shares and even more preferably between 55 and 75 shares; - 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 fibers 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 equipped with at least one longitudinal tooth, the transmission belt being an asynchronous belt; - the body is equipped 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 [Fig. 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 shows a graph illustrating the evolution of the electrical resistance of a belt tooth as a function of the percentage of unregenerated 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 the present 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 given 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 in English) 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. Thus, the 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 shows graphene sheets, organized in a more or less graphitic manner in a parallel stacking, but whose orientation relative to adjacent sheets is random. The graphitic crystallites are often misoriented with respect to each other within the primary particle, leading to a The disordered state of the carbon black microstructure. Furthermore, it is known that carbon black, as defined above, possesses conductive properties which, in the use 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 notably described 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 relating to recovered carbon black (rCB). Recovered carbon black is a solid product regenerated by the thermal decomposition of elastomeric products containing carbon black, which is free of thread and fabric, and which, 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 in fact 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, whereas reclaimed carbon black is not produced directly from hydrocarbons but from elastomeric products that have already been processed and that contain carbon black. These processed elastomeric products are most often used elastomeric products such as tires or belts.

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

[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 very little 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 / 10.3990 / L9789036552899. The pyrolysis process The process used allows for such a reduction of PAHs, as described in CJ Noms, A. López Cerdán, 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 hazardous to health, 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 recovered elastomeric materials / products used to produce regenerated carbon black.

[0034] Advantageously, the 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 to say, one that is non-conductive or very weakly conductive, may be desirable for household appliance applications that require such belts due to the absence of a ground wire at the motor. In this way, the propagation of electricity to other parts of the appliance that the user might touch is prevented. In other words, these insulating belts prevent the risk of electrocution.

[0036] On the other hand, this may 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 the total proportion of carbon black, which corresponds to the sum of the proportions of regenerated and non-regenerated carbon black, is at most equal to 80 parts.

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

[0039] For example, the total proportion of carbon black may 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 the belt 10 may have a proportion of recycled carbon black less than 70 parts, for example 65 parts recycled carbon black, while not including any non-recycled carbon black. In other words, there may be less than 70 parts recycled carbon black and 0 parts non-recycled carbon black.

[0041] Incorporating a proportion of non-regenerated carbon black allows the belt's conductivity to be adjusted according to the performance requirements of a given application. Thus, the higher the proportion of non-regenerated 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 mixture of regenerated and non-regenerated carbon black—can be offset and improved by the addition of other regenerated, recycled, or renewable elements, as described later.

[0043] Furthermore, the inventors have observed that a total carbon black proportion exceeding 80 parts could lead to difficulties in manufacturing the transmission belt. Indeed, the carbon black proportion influences, among other things, the viscosity of the elastomer which beyond 80 parts in 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 understood to be an EPDM blend obtained from the recycling of a previously processed elastomer product containing an 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 a conventional EPDM elastomer, i.e., directly derived from the processing of hydrocarbons, from bio-based materials, or may already be recycled.

[0045] EPDM blend means 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 components.

[0046] During the production of the regenerated EPDM blend, the initial EPDM blend is thermo-mechanically decomposed, notably by shearing, which breaks the vulcanization bridges 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 at most 30 parts in tooth B of the belt 10. This ensures the stability of the properties of the total EPDM mixture obtained, regardless of the variability of the waste / products used to prepare the regenerated EPDM mixture. Tooth B of the belt 10 thus has a total EPDM proportion that corresponds to the sum of conventional or non-regenerated EPDM and regenerated EPDM, resulting from the regenerated EPDM mixture as described above. The total elastomer proportion is 100 parts. It is understood that for a given proportion of EPDM, the proportion of regenerated EPDM is equal, so that the total EPDM proportion is 100 parts. In other words, when belt 10 comprises both conventional EPDM and regenerated EPDM, the total proportion of EPDM is constant and substantially equal to 100 parts.

[0049] Thus, the proportions of EPDM, resulting from the regenerated EPDM blend, are defined by the composition of the source material used. The remaining proportions correspond mainly to 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 are understood to be 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 the belt 10 has the advantage of further reducing the environmental impact and carbon footprint of the belt 10. Natural rubber has a proportion of no more than 15 parts in the mixture. The inventors have observed that a higher proportion of natural rubber in the belt tooth leads to a degradation of the mechanical properties after aging.

[0051] Natural rubber may 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 reducing 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. Moreover, a belt free of chloroprene also improves its environmental impact.

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

[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 selected without limitation from cotton fibers, flax fibers, rice fibers, hemp fibers, wood fibers such as spruce or oak fibers, or a combination of these types of fillers. Since these fillers come from plant sources, and are therefore renewable, they also help to reduce the carbon footprint of the belt. Cellulosic fibers serve as reinforcing fillers. In particular, these cellulosic fibers introduce anisotropy to the mixture and contribute to improving low-elongation 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, regenerated carbon black (rCB) in the mixture. They can also replace or substitute, at least partially, non-regenerated carbon black (CB), i.e., conventional carbon black. In this way, in the proportions described above, the cellulosic fibers make it possible to avoid adding too much carbon black (regenerated or non-regenerated), which, in total proportions exceeding a certain threshold, can lead to viscosity problems in the mixture, as described above.

[0059] Cellulosic fibers thus contribute to reducing the environmental impact but 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 comprise 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 [l,3-phenylenebis(l-methylethylidene)]bis[tert-butyl peroxide, [l,4-phenylenebis(l-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 may, alternatively, be composed of sulfur, accelerators, co-agents or metal oxides.

[0065] With reference to [Fig. 1], the belt 10 may be an asynchronous belt, for example of the poly-V® type, having a profile selected, without limitation, from a profile H, J, K, L or M or another type. These profiles are defined by ISO 9982:2021, published in September 2021. The belt 10 may also be a belt synchronous, as illustrated in [Fig.2]. [Fig.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 yarns. "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 comprising 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 relate to 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, 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] [Tables 1] Ref. 1 Ex. A Ex. B Ex. C Ex. D Ex. E Polybutadiene / chloroprene (BR / CR) 100 parts - - - - Ethylene-propylene-diene monomer (EPDM) - 100 parts 100 parts 90 parts 90 parts 100 parts Natural rubber (NR) - - - 10 parts 10 parts - Non-reclaimed carbon black (CB) 55 parts 35 parts 42 parts 40 parts 35 parts - Carbon black - 20 30 35 40 65 | regenerated (rCB)|| shares | shares | shares | shares | shares |

[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-regenerated carbon black, that is, carbon black directly derived from hydrocarbons. In other words, the tooth of the belt in Example E contains only regenerated carbon black. With reference to what has been 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 NI 15 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-regenerated) are classified into families according to their particle size, from NI 10 (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. Types N330 or N550 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 to E include cellulose fibers in a proportion of at least 3 parts, and preferably in a proportion of 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 can 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 can be chosen, without limitation, from an aromatic, parafinic 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] The clear fillers may be reinforcing, semi-reinforcing or inert fillers such as, for example, silica, calcium carbonate, kaolin or talc. They may be present in a proportion not exceeding 20 parts.

[0083] The protectants are chosen, in a non-limiting manner, 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] [Tables2] Composition 1 Composition 2 Polybutadiene / chloroprene (BR / CR) - - Ethylene-propylene-diene monomer (EPDM) 80 parts 50 parts Natural rubber (NR) 20 parts 50 parts Non-reclaimed carbon black (CB) 25 parts 25 parts Reclaimed carbon black (rCB) 40 parts 25 parts

[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 or mechanical properties that have been 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] The electrical resistance is determined according to ISO 1813:2014, published in February 2014. In this standard, the electrical resistance is given in Ohm (Q) for a given length of belt and for a given number of teeth, here 5 teeth.

[0090] Service life is generally measured by rotation on pulleys. Depending on the intended applications, at least one of the pulleys has an unbalanced weight for testing. In the following, tests were carried out with unbalanced weights designed for belts having teeth with J or H profiles as defined by ISO 9982:2021. For convenience, a type J unbalanced weight will be used hereafter 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 unbalance 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 unbalance 21 is characterized by an 8.6 kg imbalance mass located 300 mm from the axis of rotation of the pulley R. 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 carried out at ambient 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 520 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 at temperature, in particular so 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 10⁴ MQ. During testing, the service life of such a belt was measured at 155 hours with an imbalance H and 325 hours with an imbalance J.

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

[0095] The electrical resistance can be adjusted with the respective proportions of regenerated and non-regenerated carbon black. For example, [Fig. 6] shows a graph illustrating the evolution of the electrical resistance as a function of the proportion of non-regenerated carbon black (CB), here of type Nl 15, according to the number of parts of regenerated carbon black (rCB). The proportion of non-regenerated carbon black (CB) is defined as the ratio between the number of parts of non-regenerated carbon black (CB) and the sum of the parts in the belt tooth. Generally, the electrical resistance decreases as the proportion of non-regenerated carbon black (CB) increases. Conversely, for a given proportion of non-regenerated carbon black (CB), the electrical resistance is lower as the number of parts of regenerated carbon black (rCB) increases.

[0096] [Tables3] Ref. 1 Ex. A Ex. C Ex. D Ex. E Comp. 1 Comp. 2 Density 1.26 1.14 1.12 1.16 1.13 1.12 1.13 CB Rate 27.9% 16% 18.3% 15% 0% 12% 12.4% Electrical Resistance (5 teeth) 0.0001 MQ 4.13 MQ 1.14 MQ 1.88 MQ 5000 MQ 481 MQ - Life (unbalance H) 155 h 414 h 300 h 180 h - - - Life (unbalance J) 325 h - - - 380 h 30 h 23 h

[0097] The service life of the belts of examples A, C and D according to the invention, measured with an H-type unbalance, is at least equivalent to or greater than the service life of the reference belt.

[0098] The life of the belt of example E according to the invention, measured with a type J unbalance, is equivalent to or greater than the 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 service life measured with an imbalance J decreases as the proportion of natural rubber increases, which here varies between 0, 20, and 50 parts. It can be deduced that a high proportion of natural rubber in the composition deteriorates 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, given that the variations 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 the carbon footprint can be further improved by increasing the proportion of recycled carbon black and / or increasing the proportion of natural rubber and / or increasing the proportion of cellulosic fibers in the composition. However, depending on the needs and the intended application, a trade-off is necessary in 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 above.

Claims

Demands

1. Transmission belt (10) comprising a body having at least one tooth (B) based on elastomer, said at least one tooth comprising: - 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; - 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 fibers in a proportion of at least 3 parts.

4. Belt (10) according to claim 3, wherein the proportion of cellulosic fibers 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 fibers are selected from wood fibers such as spruce fibers 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.

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.

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13. 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. Belt (10) according to any one of claims 1 to 8, wherein said tooth (B) is devoid of chloroprene. Belt (10) according to any one of claims 1 to 9, wherein said tooth (B) is devoid of any halogenated compound. 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. 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. 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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