High performance toothed belt made of epdm

Abstract

The invention relates to an elastomeric toothed belt comprising a fabric spanning the teeth of the toothed belt, wherein the elastomer mixture forming the teeth contains at least 70% by weight of crosslinked ethylene-propylene rubber (EPM) and / or crosslinked ethylene-propylene terpolymer rubber (EPDM) based on the proportion of polymers of the elastomer mixture, and wherein an intermediate layer is arranged between the fabric and the elastomer mixture forming the teeth, which intermediate layer contains at least 70% by weight of hydrogenated acrylonitrile-butadiene rubber (HNBR) based on the proportion of polymers of the intermediate layer. This elastomeric toothed belt is halogen-free and is characterized by improved durability and good low-temperature stabilization properties. The invention further relates to a method for producing these elastomeric toothed belts and the use of a hydrogenated acrylonitrile-butadiene rubber (HNBR) layer in these toothed belts to increase the service life, improve the low-temperature stabilization and improve the adhesion between the teeth and the fabric.

Description

Technical Field

[0001] This invention relates to elastomeric toothed belts comprising a fabric with teeth spanning the belt, wherein the elastomeric mixture forming the teeth contains at least 70% by weight of crosslinked ethylene-propylene rubber (EPM) and / or crosslinked ethylene-propylene terpolymer rubber (EPDM) based on a polymer proportion of the elastomeric mixture, and wherein an intermediate layer is disposed between the fabric and the elastomeric mixture forming the teeth, the intermediate layer containing at least 70% by weight of hydrogenated acrylonitrile-butadiene rubber (HNBR) based on a polymer proportion of the intermediate layer. The invention further relates to methods for producing these elastomeric toothed belts and the use of a hydrogenated acrylonitrile-butadiene rubber (HNBR) layer in these toothed belts to increase service life, improve low-temperature stability, and improve adhesion between the teeth and the fabric. Background Technology

[0002] Toothed belts are conventionally made from elastomer blends based on chloroprene (CH2=C(Cl)-CH=CH2). Higher-quality toothed belts containing sulfur-crosslinked HNBR (=hydrogenated acrylonitrile / butadiene rubber) as the base polymer can be used as an alternative. Furthermore, HNBR using peroxidative crosslinking is known to have particularly good heat aging resistance. The strength of HNBR elastomers can be further improved by adding zinc salts of acids with free radical polymerizable groups (such as, in particular, acrylic acid or methacrylic acid, and also sorbic acid) for peroxidative crosslinking.

[0003] For reinforcement, conventional toothed belts typically include a fabric layer on the toothed side and usually also on the opposite side. This fabric layer covers the teeth or belt body, and the toothed pulley is engaged between the teeth through this fabric layer. To firmly attach this fabric to the teeth of the toothed belt, the fabric is usually first coated with a mixture of resorcinol / formaldehyde and latex (also known as an RFL layer). Subsequently, as an adhesion-promoting mixture, an elastomer mixture is applied, which is usually formed of the same elastomer as the teeth of the toothed belt, to ensure a good bond between the coated fabric and the elastomer of the teeth. In the case where the teeth of the toothed belt are formed of chloroprene, a chloroprene coating is applied to the fabric, while in the case where the teeth of the toothed belt are formed of HNBR, an HNBR coating is applied to the fabric.

[0004] The application of adhesion-promoting mixtures traditionally involves dissolving an uncrosslinked elastomer in a suitable organic solvent (e.g., toluene, xylene, or carboxylic acid esters) and applying it to an RFL-treated fabric in an amount sufficient to form an adhesion-promoting layer with a thickness in the range of approximately 10 μm after solvent removal. Alternatively, a thin layer of elastomer can be applied to the RFL-treated fabric via calendering.

[0005] However, a problem with conventional high-performance toothed belts made of chloroprene rubber is their chlorine content, as combustion of, for example, end-of-life chloroprene products releases hydrogen chloride, requiring expensive and complex combustion exhaust filtration. Therefore, there is a need for an alternative to chloroprene rubber that offers desirable, comparable performance characteristics but is free of chlorine or other halogens.

[0006] HNBR meets the requirement of the lowest possible chlorine content, but on the other hand, it has the disadvantages of relatively high price and relatively low flexibility in a lower temperature range.

[0007] Elastomer materials that better meet comparable performance characteristics include ethylene-propylene elastomers, such as ethylene-propylene-diene elastomers (EPDM). For example, DE 10 2008 055 530 describes toothed belts for camshaft drives in internal combustion engines, wherein the elastomer of the toothed belt body is composed of an EPDM blend that also contains special short fibers with lengths ranging from 2 mm to 5 mm. The blend described in DE 10 2008 055 530 is claimed to allow for at least a significant elimination of NBR and HNBR, while achieving improved low-temperature flexibility and longer service life, as well as the same or better force transmission.

[0008] However, in the case of toothed tapes made of EPDM, where a layer of EPDM is placed between the fabric and the EPDM, it was found that sufficient adhesion between the fabric and the EPDM material could not be achieved, and therefore these toothed tapes exhibited only insufficient durability. Even when fabric with a conventional RFL coating is directly bonded to the teeth of the toothed tape made of EPDM, a sufficient service life cannot be achieved.

[0009] EP 1 677 030 B1 describes a toothed belt having a body made of EPDM and a fabric attached thereto, wherein the fabric has been impregnated and coated with a resorcinol-formaldehyde latex containing carboxylated hydrogenated nitrile butadiene rubber as a latex. This coating is claimed to improve the adhesion of the fabric of the toothed belt to the EPDM body (compared to a toothed belt without an RFL coating). However, this adhesion does not show a significant improvement in durability, possibly due to the significantly different polarities of the resorcinol-formaldehyde resin and carboxylated hydrogenated nitrile butadiene rubber on the one hand, and the non-polar EPDM elastomer on the other hand, or due to the relatively large difference in stiffness between the two materials.

[0010] Against this backdrop, there is a need for methods and means to achieve cost-effective and ideally halogen-free toothed belts with long service life. There is also a need for methods and means to achieve strong adhesion between the fabric and EPDM elastomer in the toothed belt. This invention addresses these needs. Summary of the Invention

[0011] In the context of the research upon which this invention is based, it has been unexpectedly discovered that a good service life and adhesion between the toothed belt body and the fabric can be achieved through a toothed belt. Preferred embodiments of such toothed belts are specifically defined below.

[0012] Therefore, in a first aspect, the present invention relates to an elastomeric toothed belt having a body and a plurality of teeth arranged longitudinally spaced apart from each other on the inner or outer side of the body and a fabric spanning the teeth, the body having a length, sides arranged laterally apart from each other, and inner and outer sides, wherein the elastomeric mixture forming the teeth contains at least 70% by weight of crosslinked ethylene-propylene rubber (EPM) and / or crosslinked ethylene-propylene terpolymer rubber (EPDM) based on a polymer proportion of the elastomeric mixture, and wherein an intermediate layer is disposed between the fabric and the elastomeric mixture forming the teeth, the intermediate layer containing at least 70% by weight of hydrogenated acrylonitrile-butadiene rubber (HNBR) based on a polymer proportion of the intermediate layer.

[0013] To improve the adhesion between the fabric and the toothed belt body, it is therefore crucial that a large portion of the elastomer in the contact area between the toothed belt body and the intermediate layer is made of EPDM / HNBR. A higher proportion of other elastomers can weaken this adhesion, and therefore their proportion should generally be kept low but not necessarily destructive.

[0014] Unless otherwise stated below, all reported numbers relate to the polymer proportions in the respective compositions, and as a result, the sum of these reported numbers may exceed 100%.

[0015] In the context of the invention described herein, EPM or EPDM forms at least the primary elastomer material of the teeth of the toothed belt, wherein a particularly preferred proportion is based on the polymer ratio of the elastomer mixture forming the teeth, which contains crosslinked ethylene-propylene rubber (EPM) and / or crosslinked ethylene-propylene terpolymer rubber (EPDM) at a ratio of at least 80% by weight, preferably at least 90% by weight, very particularly preferred at least 95% by weight, and even more preferably at least 98% by weight. Alternatively or additionally, it is preferred that these elastomers form the primary elastomer material of the entire contact surface (i.e., teeth and connecting web) between the fabric and the toothed belt. Furthermore, it is preferred that the entire body of the toothed belt is primarily (i.e., reaching at least 70% by weight) formed of EPM and / or EPDM as the elastomer, as this simplifies the production of the toothed belt body. "Entire body" should now be understood to mean a toothed belt body without any reinforcing elements (e.g., tensile strands) that may be present.

[0016] In one alternative, 100% of the elastomer in the elastomer mixture may be supplied by EPM or EPDM. In another alternative, the remainder to 100% of the elastomer may be formed from different elastomers, preferably one or more of silicone rubber, chloroprene rubber, epichlorohydrin, hydrogenated nitrile-butadiene rubber, natural rubber, ethylene-vinyl acetate copolymer, ethylene-methacrylate copolymer and terpolymer, styrene-butadiene rubber, nitrile rubber, chlorinated polyethylene, chlorosulfonated polyethylene, alkylated polyethylene-polysulfone, butadiene rubber, and mixtures thereof. However, it is preferred that the other elastomers are not halogen-containing elastomers.

[0017] In one embodiment, the remainder to 100% or at least a portion thereof of the elastomer may be NBR or HNBR. In yet another alternative, a mixture of EPM and EPDM may be used as the main component of the elastomer of the teeth of the toothed belt, i.e., at least 70% by weight of the elastomer in the teeth is provided by EPM and EPDM, wherein it may be preferred that the teeth of the toothed belt are formed solely of a mixture of EPM and EPDM as the elastomer.

[0018] The EPDM in the teeth of the toothed belt used in this invention is not subject to any relevant limitations, and any suitable conjugated diene can be used in its production, including, for example, 1,4-hexadiene, dicyclopentadiene, or ethylidene norbornene (ENB). Preferred EPM or EPDM elastomers of this invention contain 35% to 80% by weight of ethylene units, 65% to 25% by weight of propylene units, and 0% to 10% by weight of unsaturated diene components. In more preferred embodiments, the EPM or EPDM elastomer contains 55% to 78% by weight of ethylene units, and in the most preferred embodiment, the EPM or EPDM elastomer contains 65% to 75% by weight of ethylene units. At these more preferred ethylene contents, the annular belt containing the EPM or EPDM elastomer composition as the main body of the toothed belt exhibits improved anti-pilling properties. Most preferably, the elastomer of the entire body of the toothed belt according to this invention is EPDM.

[0019] The teeth of the toothed belt and optionally the entire body (except for reinforcing elements, such as reinforcing strips integrated therein) are preferably formed of an elastomer mixture that contains not only an elastomer but also reinforcing filler, particularly in an amount of 25 to 250 parts per 100 parts of elastomer, and preferably 25 to 100 parts per 100 parts of elastomer, and optionally 1 to 30 parts per 100 parts of elastomer, of a metal salt of an α,β-unsaturated organic acid.

[0020] Suitable fillers may include, for example, carbon black, calcium carbonate, talc, clay, hydrated silica, or mixtures of these materials. Fillers impart favorable thermal stability to the elastomer material while simultaneously achieving good tear resistance and dynamic properties.

[0021] The elastomer mixture may also contain textile fibers with a length of up to 7 mm as filler and / or for reinforcement, wherein the fibers may be formed from aramid, carbon, glass, polyester, polyamide, synthetic yarn, polyvinyl alcohol or other materials.

[0022] In addition to these components, elastomer blends may also contain other ingredients commonly used in elastomer compositions. These components include, for example, processing oils and extender oils, antioxidants, waxes, pigments, softeners, plasticizers, etc. These additives may be used in the amounts conventionally used in standard elastomer blends.

[0023] The EPM and / or EPDM in the elastomer forming the teeth of the elastomer toothed band are cross-linked, wherein the cross-linking can be induced by any cross-linking agent commonly found in the art. Particularly suitable cross-linking agents are sulfur cross-linking agents and peroxide-based cross-linking agents. Therefore, the cross-linked elastomer in the elastomer mixture forming the teeth is preferably a sulfur-cross-linked or peroxide-cross-linked elastomer. This elastomer is very particularly preferred to be a peroxide-cross-linked elastomer.

[0024] In the context of the invention described herein, preferred peroxide crosslinking agents for EPM and / or EPDM elastomers are organic peroxides, including but not limited to dicumyl peroxide, bis(tert-butyl peroxide)diisopropylbenzene, tert-butyl perbenzoate, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane, and α,α-bis(tert-butyl peroxide)diisopropylbenzene. A particularly preferred organic peroxide is α,α-bis(tert-butyl peroxide)diisopropylbenzene.

[0025] For the purposes of this invention, the curing activity of the organic peroxide is typically 2 to 10 parts (per 100 parts elastomer). The preferred content of the organic peroxide is between 4 and 6 parts per 100 parts elastomer. As part of the mixed curing system, sulfur may optionally be added to the organic peroxide crosslinking composition in an amount of 0.01 to 1.0 parts (per 100 parts elastomer) to improve the elastic modulus of the cured elastomer without adversely affecting its tear resistance.

[0026] The second essential component of the toothed belt according to the invention is an intermediate layer comprising HNBR as its main polymer component (i.e., 70% or more by weight). This layer is not formed of resorcinol-formaldehyde and HNBR, because due to the high polarity of resorcinol-formaldehyde, such a layer cannot impart sufficiently favorable adhesion to the teeth of the toothed belt formed from EPM / EPDM as an elastomer. Therefore, it is preferred that the intermediate layer does not contain any proportion of the resorcinol-formaldehyde resin contained therein. In the context of this application, the term "HNBR" or "hydrogenated acrylonitrile-butadiene rubber" should be understood to mean a hydrogenated rubber material composed of acrylonitrile and butadiene, and also a corresponding terpolymer, which additionally contains up to 20% by weight of acrylic acid and / or methacrylate.

[0027] In addition to HNBR, the interlayer may also contain (based on a total proportion of no more than 30% by weight) the aforementioned elastomer as a possible additive of EPM and / or EPDM as the tooth material of the toothed belt according to the invention. However, the highest possible proportion of HNBR is preferred, wherein at least 80% by weight is considered preferred and at least 90% by weight is considered particularly preferred, in each case based on the proportion of polymer in the interlayer.

[0028] A particularly advantageous HNBR for use as the interlayer material in the toothed belt according to the invention is hydrogenated acrylonitrile-butadiene rubber with a hydrogenation degree ranging from 70% to 99%, preferably 95% to 98%. Alternatively or additionally, hydrogenated acrylonitrile-butadiene rubber with an acrylonitrile content of 18% to 47% by weight, and especially 30% to 37% by weight, is also particularly suitable.

[0029] In the elastomeric toothed tape according to the invention, the intermediate layer is advantageously crosslinked, wherein the crosslinking agents available particularly include sulfur or peroxide crosslinking agents, especially organic peroxide crosslinking agents, as cited above for the crosslinking of EPM and / or EPDM elastomers. In the intermediate layer, sulfur-crosslinked HNBR exhibits better adhesion values, while peroxide-crosslinked HNBR exhibits better long-term heat resistance.

[0030] On the one hand, the thickness of the interlayer should be sufficiently large to impart adequate adhesion between the fabric and the teeth of the toothed tape. On the other hand, no additional improvement in adhesion or other properties is observed above a certain thickness, and therefore, further increasing the thickness is often disadvantageous due to the cost of HNBR. In this context, an interlayer thickness of at least about 10 μm is considered preferred, a thickness in the range of about 10 to 500 μm is considered particularly preferred, and a thickness in the range of about 50 to 200 μm is considered very particularly preferred. An interlayer with a thickness within the particularly preferred range can be applied to the fabric by calendering, and therefore the coating can be performed solvent-free.

[0031] The HNBR interlayer preferably has a Shore A hardness of less than 90, as determined according to DIN ISO 7619-1. Particularly preferred is that the hardness of the HNBR interlayer is in a similar range to the Shore A hardness of the elastomer mixture forming the teeth, i.e., preferably within ±10 and particularly within ±5 of the Shore A hardness of the elastomer mixture forming the teeth.

[0032] To impart conductivity and the ability to dissipate static charge, in addition to the HNBR elastomer, the interlayer may contain conductive additives, among which carbon black is considered particularly suitable. If carbon black is included in the interlayer, the proportion of carbon black is preferably in the range of 20 to 70 parts, and particularly preferably 30 to 60 parts, based on 100 parts of polymer in the interlayer. Alternatively or additionally, the interlayer contains conductive additives, particularly in the form of carbon black, in an amount that imparts a resistance of less than 50 MΩ, and preferably less than 5 MΩ, to the toothed strip as determined according to ISO 9563:2015.

[0033] To improve strength and / or crosslinking rate, the intermediate layer may further contain metal salts of organic acids with polymerizable groups, such as zinc dimethacrylate or zinc diacrylate, or carboxylic acids having two or more conjugated double bonds, particularly in the form of sorbic acid.

[0034] Considering the intermediate layer and body of the elastomer toothed band, it is important to note that in the case of crosslinking, the crosslinking agent and the elastomer undergo a chemical reaction, and reactive components such as sorbic acid or the referenced metal salt are optionally included in these reactions.

[0035] The fabric present in the elastomeric toothed belt according to the invention can have any desired construction, such as a conventional fabric composed of warp and weft yarns at any angle, or it can be composed of warp yarns, or a knitted, woven, or warp-knitted construction, etc. More than one layer of material can be used. If desired, the material can be obliquely cut such that the ply forms an angle with the direction of belt movement. Conventional fabrics can be used, employing materials such as cotton, polyester, polyamide, hemp, jute, glass fiber, and various other natural and synthetic fibers. In a preferred embodiment of the invention, the fabric layer consists of a stretchable, abrasion-resistant fabric, wherein at least one of the warp or weft yarns is made of polyamide. Fabrics composed of at least 70% polyamide, particularly linear aliphatic polyamide, are particularly preferred. In the most preferred form, the fabric is composed of nylon 66.

[0036] To impart improved adhesion on the intermediate layer, the fabric may include a coating with resorcinol-formaldehyde latex (RFL). Available RFL compositions include any suitable materials, wherein, in each case, based on the solids content of the composition, the proportion of resorcinol-formaldehyde resin in the RFL composition is advantageously in the range of 2% to 40% by weight, and the proportion of latex is in the range of 60% to 98% by weight. A resorcinol-formaldehyde resin proportion in the range of 5% to 30% by weight and a latex proportion in the range of 70% to 95% by weight are considered preferred.

[0037] There are no particular requirements for the latex included in the RFL composition, and therefore, in principle, any latex conventionally used in RFL compositions can be used. Examples of such latex materials include, in particular, HNBR, NBR, carboxylated HNBR, carboxylated NBR, vinylpyridine / styrene-butadiene rubber (“VP / SBR”), carboxylated VP / SBR, SBR, chlorosulfonated polyethylene (“CSM”), ethylene-α-olefin elastomers such as ethylene-propylene-diene terpolymers (“EPDM”) and ethylene-propylene copolymers (“EPM”), wherein mixtures of two or more of these materials may also be used. In terms of processing characteristics, it is preferred that the latex is halogen-free. In the context of this invention, the latex preferably used in the RFL composition is a vinylpyridine-containing latex, such as vinylpyridine / styrene-butadiene rubber (“VP / SBR”) or carboxylated VP / SBR. The vinylpyridine content of this latex is preferably greater than 50% by weight.

[0038] For the application rate of the RFL composition, a range of 10% to 50% by weight (based on the total weight of the RFL-coated fabric) can be considered appropriate.

[0039] To further enhance the structural integrity of the toothed belt, the belt may additionally contain multiple tensile strands embedded in the toothed belt body. These tensile strands, especially in the form of cords, may be made of polyamide (PA), aromatic polyamide, polyester, glass (e.g., E- or K-glass), carbon, polyetheretherketone (PEEK), or polyethylene 2,6-naphthalenedicarboxylate (PEN).

[0040] While an HNBR-based interlayer between the fabric and the teeth of the toothed belt is essential for the invention of the elastomeric toothed belt, the toothed belt may also include a fabric overlay on the side opposite to the teeth, which may then have a PFL coating and / or be bonded to the toothed belt body via an HBNR-based or other material interlayer.

[0041] In another aspect, the present invention relates to a method for producing an elastomer toothed belt, the method comprising the following steps:

[0042] (i) Provide fabric;

[0043] (ii) Applying a coating to the fabric, wherein the coating composition contains at least 70% by weight hydrogenated acrylonitrile-butadiene rubber (HNBR) based on the polymer proportion in the coating composition.

[0044] (iii) The fabric is fixed to the body of the elastomeric toothed belt, the teeth of which are formed of an elastomeric mixture, which contains at least 70% by weight of crosslinked ethylene-propylene rubber (EPM) and / or crosslinked ethylene-propylene terpolymer rubber (EPDM) based on the polymer ratio of the elastomeric mixture that forms the teeth, such that the coating from step (ii) is disposed between the teeth and the fabric.

[0045] Preferably, this method produces the elastomeric toothed belt as described above.

[0046] The coating application in step (ii) can advantageously be performed by applying the HNBR solution to the fabric and subsequently evaporating the solvent. The solvent used can be any suitable solvent for dissolving HNBR, such as xylene, toluene, or carboxylic acid esters. The advantage of applying the intermediate layer from the solution is that a relatively thin layer can be applied, thereby minimizing the amount of HNBR material used.

[0047] On the other hand, a disadvantage of applying the interlayer from the solution is that the solvent needs to be removed during further processing, which may be undesirable due to the associated environmental burden. Therefore, a pre-formed interlayer can also be, and preferably, applied to the fabric by calendering. The larger thickness of the HNBR layer typically used in this case has the additional advantage of achieving better stability in the connecting web region of the toothed strip, due to the increased distance between the tensile strands present in the toothed strip and the fabric.

[0048] As mentioned above, the adhesion between the fabric and the interlayer can be further improved by applying an RFL layer to the fabric. Therefore, in the context of this invention, it is preferable to further include the step of applying a resorcinol / formaldehyde / latex adhesion-promoting layer prior to step (i). This application can be achieved, for example, by an immersion treatment, in which the fabric is immersed in a solution of the RFL composition, removed, and subsequently dried for the time required to obtain the desired RFL application rate.

[0049] The fixation in step (iii) of the method preferably includes the step of crosslinking the elastomer in the teeth and optionally in the toothed belt body and in the intermediate layer.

[0050] This invention is based on the unexpected discovery that good adhesion between the toothed belt body based on BPM and / or EPDM and the reinforcing fabric can be achieved by incorporating an intermediate layer composed of HNBR. Improved low-temperature stability can be achieved compared to HNBR-based elastomer toothed belts. Therefore, another aspect of the invention relates to the use of a hydrogenated acrylonitrile-butadiene rubber (HNBR) layer disposed between the EPM and / or EPDM teeth of the toothed belt and the fabric spanning these teeth for increasing the service life of the toothed belt and / or for improving the adhesion between the teeth and the fabric in the toothed belt and / or improving the low-temperature stability of the toothed belt. Attached Figure Description

[0051] The invention will now be described in more detail with reference to numerous working examples; however, these working examples should not be construed as limiting the scope of protection of this application in any way.

[0052] The present invention will be further illustrated with reference to the schematic diagram.

[0053] Figure 1 A three-dimensional schematic diagram of a toothed strip with a coating is shown;

[0054] Figure 2 A longitudinal section passing through a coated toothed strip is shown. Detailed Implementation

[0055] Figure 1 The diagram shows a toothed strip having an outer layer 2 serving as a strip backing, an embedded strength member 3, and a substructure 4. The strength member consists of multiple parallel tensile strands forming... Figure 1 The strength member layer shown is a single-layer embodiment. The tensile strands, especially in the form of cords, can be made of polyamide (PA), aramid, polyester, glass (e.g., E- or K-glass), carbon, polyetheretherketone (PEEK), or polyethylene 2,6-naphthalenedicarboxylate (PEN), or a combination of the materials mentioned above.

[0056] The outer layer (2) and the substructure (4) together form an elastic body, which, in the context of the present invention, is composed of, for example, vulcanized rubber based on EPM, EPDM or an EPM / EPDM mixture.

[0057] Substructure 4 has a toothed profile including teeth 5 and toothed connecting webs 6 and forms a force transmission region 7 that is particularly prone to wear. For this reason, the force transmission region is provided with an abrasion-resistant coating 8 in the form of a textile cover. The textile cover is made of a woven or knitted fabric, preferably composed of polyamide (PA) and / or polyester and / or cotton and / or aramid and / or polyether ether ketone (PEEK). A layer composed of HNBR is arranged between the textile cover and the elastomer forming the teeth and toothed connecting webs. According to the invention, an intermediate layer (not shown) composed of HNBR is arranged between the textile cover and the elastomer forming the teeth and toothed connecting webs.

[0058] according to Figure 2 The toothed tape includes an outer layer 11 as a backing, an embedded strength member 12 in the form of tensile strands, and a substructure 13 having a toothed force transmission region 14. In this working example, both the overlay 11 and the force transmission region are provided with coatings 15 / 16. Each of these coatings comprises a textile overlay, particularly in the form of a fabric, coated with an elastomer mixture 18 or 19 to bond the fabric to the EPDM of the substructure.

[0059] The present invention is described below with reference to several examples, which should not be construed as limiting the scope of protection of this application in any way.

[0060] Example:

[0061] Various toothed belts with the geometry STD 1280 8M-15 are manufactured using the following construction:

[0062] Table 1:

[0063]

[0064] *Chloroprene rubber; phr = number of parts per 100 parts of rubber (number of parts per 100 parts of rubber).

[0065] Perform routine tests on the toothed belts produced in this manner. The measured characteristic values ​​are reported in Table 2 below:

[0066] Table 2

[0067]

[0068]

[0069] As clearly shown in Table 2, the toothed belt "Invention 1" exhibits the best durability (352h) compared to the toothed belts 1 to 3 (Comparison 1). In contrast, the toothed belts made of chloroprene rubber (Comparison 1) and EPDM without an interlayer (Comparison 3) show a significant decline in durability. The toothed belt made of EPDM with a chloroprene rubber interlayer (Comparison 2) shows an insufficient service life of only 87h.

[0070] The toothed tapes "Invention 1" and "Comparative 3" are chlorine-free. Both "Comparative 1" and "Invention 1" have relatively low resistance, which allows charge to discharge via the tape. Therefore, it is evident that the toothed tape "Invention 1" has the best characteristic distribution.

[0071] Compared to toothed belts (not shown) made entirely of HNBR as the elastomer material, the toothed belt "Invention 1" also has significantly improved low-temperature stability.

Claims

1. An elastomer toothed belt having a body and a plurality of teeth arranged longitudinally spaced apart on the inner or outer side of the body, and a fabric crossing the teeth, the body having sides arranged laterally at a distance from each other, and inner and outer sides, characterized in that, The elastomeric mixture forming these teeth contains at least 70% by weight of crosslinked ethylene-propylene rubber (EPM) and / or crosslinked ethylene-propylene terpolymer rubber (EPDM) based on the polymer proportion of the elastomeric mixture, and wherein an intermediate layer is disposed between the fabric and the elastomeric mixture forming these teeth, the intermediate layer containing at least 70% by weight of hydrogenated acrylonitrile-butadiene rubber (HNBR) based on the polymer proportion of the intermediate layer.

2. The elastomeric toothed band as described in claim 1, wherein, Based on the polymer proportions of the elastomer mixture that forms these teeth, these teeth contain at least 80% by weight of the crosslinked ethylene-propylene rubber (EPM) and / or ethylene-propylene terpolymer rubber (EPDM).

3. The elastomeric toothed band as described in claim 2, wherein, Based on the polymer proportions of the elastomer mixture that forms these teeth, these teeth contain at least 90% by weight of the crosslinked ethylene-propylene rubber (EPM) and / or ethylene-propylene terpolymer rubber (EPDM).

4. The elastomeric toothed band as described in claim 3, wherein, Based on the polymer proportions of the elastomer mixture that forms these teeth, the teeth contain at least 95% by weight of the crosslinked ethylene-propylene rubber (EPM) and / or ethylene-propylene terpolymer rubber (EPDM).

5. The elastomeric toothed band as described in claim 1, wherein, The body is formed from cross-linked ethylene-propylene rubber (EPM) and / or ethylene-propylene terpolymer rubber (EPDM) as elastomers.

6. The elastomeric toothed band as described in claim 1, wherein, The crosslinked elastomers in the elastomer mixture that forms these teeth are sulfur-crosslinked or peroxidation-crosslinked elastomers.

7. The elastomeric toothed band as described in claim 6, wherein, The cross-linked elastomer in the elastomer mixture that forms these teeth is a peroxidized cross-linked elastomer.

8. The elastomeric toothed band as described in claim 1, wherein, Based on the polymer ratio of the intermediate layer, the intermediate layer contains at least 80% by weight hydrogenated acrylonitrile-butadiene rubber (HNBR).

9. The elastomeric toothed band as described in claim 8, wherein, Based on the polymer ratio of the intermediate layer, the intermediate layer contains at least 90% hydrogenated acrylonitrile-butadiene rubber (HNBR) by weight.

10. The elastomeric toothed band as claimed in claim 1, wherein, The hydrogenated acrylonitrile-butadiene rubber has a degree of hydrogenation ranging from 70% to 99% and / or an acrylonitrile content ranging from 18% to 47% by mass.

11. The elastomeric toothed band as claimed in claim 10, wherein, The hydrogenated acrylonitrile-butadiene rubber has a hydrogenation degree ranging from 95% to 98%.

12. The elastomeric toothed band as claimed in claim 10, wherein, The hydrogenated acrylonitrile-butadiene rubber has an acrylonitrile content of 30% to 37% by weight.

13. The elastomeric toothed band as claimed in claim 1, wherein, The intermediate layer has a thickness of at least 10 µm and / or a Shore A hardness of less than 90.

14. The elastomeric toothed band as claimed in claim 13, wherein, The intermediate layer has a thickness ranging from 10 µm to 500 µm.

15. The elastomeric toothed band as claimed in claim 13, wherein, The intermediate layer has a thickness ranging from 50 µm to 200 µm.

16. The elastomeric toothed band as claimed in claim 1, wherein, The intermediate layer contains additives to impart conductivity.

17. The elastomeric toothed band as claimed in claim 16, wherein, The additive is in the form of carbon black.

18. The elastomeric toothed band as claimed in claim 16 or 17, wherein, Based on 100 parts of polymer in the intermediate layer, the intermediate layer contains 20 to 70 parts of the additive, and / or wherein the elastomer toothed strip has a resistance of less than 50 MΩ as determined according to ISO 9563:2015.

19. The elastomeric toothed band as claimed in claim 18, wherein, Based on 100 parts of polymer in the intermediate layer, the intermediate layer contains 30 to 60 parts of the additive.

20. The elastomeric toothed band of claim 18, wherein, The elastomer toothed strip has a resistance of less than 5 MΩ as measured according to ISO 9563:2015.

21. The elastomeric toothed band as claimed in claim 1, wherein, The fabric is made of polyamide to a degree greater than 70%.

22. The elastomeric toothed band as claimed in claim 21, wherein, The fabric is formed of linear aliphatic amides to a degree greater than 70%.

23. The elastomeric toothed band as claimed in claim 1, wherein, The fabric has a coating that contains resorcinol / formaldehyde / latex.

24. The elastomeric toothed band as claimed in claim 23, wherein, The latex of this resorcinol / formaldehyde / latex has a vinylpyridine content of more than 50% by weight.

25. A method for producing elastomer toothed belts, wherein, The method includes the following steps: (i) Provide fabric; (ii) Applying a coating to the fabric, wherein the coating composition contains at least 70% by weight hydrogenated acrylonitrile-butadiene rubber (HNBR) based on the proportion of polymer in the coating composition. (iii) The fabric is fixed to the elastomer toothed belt body, the teeth of which are formed of an elastomer mixture, based on the polymer ratio of the elastomer mixture forming the teeth, the elastomer mixture containing at least 70% by weight of crosslinked ethylene-propylene rubber (EPM) and / or crosslinked ethylene-propylene terpolymer rubber (EPDM), such that the coating from step (ii) is disposed between the teeth and the fabric.

26. The method of claim 25, wherein, The coating in step (ii) is performed by applying a solution of the hydrogenated acrylonitrile-butadiene rubber to the fabric and then evaporating the solvent, or by calendering a film containing the hydrogenated acrylonitrile-butadiene rubber onto the fabric.

27. The method of claim 25 or 26, wherein, The method further includes the step of applying a resorcinol / formaldehyde / latex adhesion-promoting layer to the fabric prior to step (i).

28. The use of distributing a layer of hydrogenated acrylonitrile-butadiene rubber (HNBR) between the teeth of a toothed belt formed of an elastomer mixture containing at least 70% by weight of ethylene-propylene rubber (EPM) and / or ethylene-propylene terpolymer rubber (EPDM) based on the polymer proportion of the elastomer mixture and the fabric spanning the teeth, for increasing the service life of the toothed belt and / or for improving the adhesion between the teeth of the toothed belt and the fabric and / or for improving the low-temperature stability of the toothed belt.

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