Commercial vehicle tires

Abstract

The invention relates to a commercial vehicle tire with bead sections, each comprising a bead core, a two-part apex, and a horn profile. The bead core sections are provided with a folded-over carcass ply. The apex consists of a radially outer part and a radially inner part, both made of a vulcanizable rubber compound. The radially inner apex part has a cross-sectional area that is 60% to 160% of the area of ​​the bead core. Furthermore, the tensile strength of the rubber material of the inner apex part at 100% elongation is 2.00 MPa to 30.00 MPa higher than that of the outer apex part. Additionally, the rubber material of the outer apex part exhibits a rebound elasticity at 70°C that is 5.0 to 50.0 percentage points higher than that of the inner apex part. According to the invention, the horn profile is made of a sulfur-curable rubber compound of a predetermined composition.

Description

[0001] The invention relates to a commercial vehicle tire with bead areas, each comprising a bead core, a two-part apex radially mounted on the outside of the bead core, and a horn profile, as well as a single- or multi-layer carcass insert folded around the bead cores, wherein each apex comprises a radially outer apex part and a radially inner apex part contacting the bead core, wherein the radially outer apex part and the radially inner apex part each consist of a rubber material, and the rubber material of the radially outer apex part differs from the rubber material of the radially inner apex part. • wherein the radially inner apex part has a cross-sectional area with an area of ​​60% to 160% of the cross-sectional area of ​​the bead core, • wherein the rubber material of the radially inner apex part has a stress value at 100% elongation - determined according to DIN 53504 with the test specimen type S3 - which is 2.00 MPa to 30.00 MPa greater than the stress value at 100% elongation of the rubber material of the radially outer apex part and • wherein the rubber material of the radially outer apex part has a rebound elasticity at 70°C - determined according to ISO 4662, with a test specimen with a thickness of 6.3 mm ± 0.5 mm according to Annex A of ISO 4662 - which is 5.0 percentage points to 50.0 percentage points greater than the rebound elasticity at 70°C of the rubber material of the radially inner apex part.

[0002] A commercial vehicle tire of the type mentioned above is known from WO 2024 / 022560 A1.

[0003] The increasing electrification of the commercial vehicle sector is placing ever higher demands on the design and performance of tires. Commercial vehicles converted to electric mobility are generally heavier than their conventional, combustion engine-powered counterparts. This weight increase is primarily due to the large and heavy batteries required for electric drive. The additional weight leads to increased stress on the tires, resulting in higher rolling resistance, more intense heat generation, and faster wear.

[0004] The tire's rim profile plays a crucial role in this context, as it is subjected to considerable stress. The additional weight of the vehicles and the specific loads from the electric drive, such as instantaneous torque and regenerative braking energy, significantly increase the forces acting on the rim profile. This component zone, responsible for the connection between the tire and the rim, is central to load transfer and is subjected to considerable stress by the heavier electric vehicles.

[0005] While the rim profile already represents a critical zone on conventional commercial vehicles, the increased stress on electric commercial vehicles leads to a heightened risk of deformation or structural weaknesses. The rim profile is subjected to additional stress, particularly during tire removal for retreading, as the tire must be repeatedly removed from and remounted on the rim. This process exposes the rim profile to high mechanical stresses, which can lead to premature wear or weakening of the profile. This is especially true if the tire has already been subjected to significant stresses due to additional loads and regenerative braking energy transfer, potentially resulting in massive and often irreparable damage to the rim profile.

[0006] In view of these challenges, the focus is on the further development of the horn profile for electrically powered commercial vehicles in order to better withstand the higher loads and thermal stress.

[0007] Furthermore, the sustainability of tire use is gaining importance. Retreading represents an environmentally friendly alternative to the complete production of new tires, as it reuses the carcass and only renews the tread. However, this process is particularly challenging for electric commercial vehicles. The wear and accelerated aging caused by the higher weight and increased heat generation place greater demands not only on the carcass and tread, but especially on the bead profile, which is subjected to particular stress during retreading. Improvements in material selection and bead profile design are therefore crucial to extending the service life of retreaded tires and meeting the requirements of electromobility.

[0008] The object of the present invention is to provide a tire, particularly for electrically powered commercial vehicles, that withstands the increased mechanical and thermal loads resulting from the additional vehicle weight and the specific conditions of the electric drive. In particular, the tire bead should be designed to maintain its structural integrity even under these increased loads and to withstand the specific requirements of retreading without premature wear or deformation.

[0009] Furthermore, the aim is to extend the overall lifespan of the tire, increase its thermal stability, and enable sustainable use through multiple retreadings in order to meet the growing demands for efficiency and environmental friendliness in the commercial vehicle sector.

[0010] In a commercial vehicle tire of the type mentioned above, the radially inner apex has a significantly smaller cross-sectional area than is currently standard, with the cross-sectional area of ​​the radially inner apex being at least one-third, and potentially at least 50%, smaller than that of conventional apex designs. Despite the "small" size of the radially inner apex, its stiff rubber material (higher tensile strength at 100% elongation) ensures overall high bead stability (good bead durability), making the commercial vehicle tire ideally suited for retreading. In particular, bead durability is significantly improved compared to current one-piece apex designs. The radially outer apex, which consequently has a larger cross-sectional area than previously standard, is made of a rubber material whose rebound elasticity at 70°C is significantly greater than that of the rubber material used in the radially inner apex.The rubber material of the radially outer apex is thus optimized with regard to the tire's rolling resistance. The higher rebound elasticity further reduces heat generation in this part of the apex, which increases the durability of the upper bead area. The rolling resistance is significantly improved, especially compared to conventional commercial vehicle tires with the previously standard two-piece apex (low rolling resistance). As described in WO 2024 / 022560 A1, the commercial vehicle tire is therefore significantly improved with regard to the inherent trade-off between rolling resistance and bead stability.

[0011] However, such a commercial vehicle tire requires further optimization measures, especially if it is intended for electrically powered commercial vehicles, to withstand the increased mechanical and thermal stresses resulting from the additional vehicle weight and the specific conditions of the electric drive. Simply improving the durability of the apex construction and matching the radial outer to the radial inner apex compound would only shift the failure pattern, as other areas of the bead would be prematurely damaged without additional optimization due to the higher loads in electrified vehicles.The goal of extending the overall service life of the tire, increasing its thermal stability, and enabling sustainable use through multiple retreadings is achieved through the particularly advantageous combination of the design described in WO 2024 / 022560 A1 with further adaptations to the bead according to the invention. In particular, the focus here is on the tire's horn profile, which must be designed to maintain its structural integrity even under these increased loads and to withstand the specific requirements of retreading without premature wear or deformation.

[0012] This is solved by optimizing the sulfur-crosslinkable rubber compound for the horn profile.

[0013] According to the invention, the horn profile is made from a sulfur-curable rubber compound containing at least the following components: - at least one diene rubber, - 40 to 90 phr (parts by weight, based on 100 parts by weight of the total rubbers in the mixture) of at least one carbon black, wherein the carbon black or blacks have a weighted average iodine value according to ASTM D 1510 of 55 to 80 g / kg, - 5 to 20 phr of at least one silica, - at least a silane coupling agent and - an efficient vulcanization system containing at least one vulcanization accelerator and elemental sulfur, wherein the mass ratio of vulcanization accelerator to sulfur is 8:1 to 3:1.

[0014] This also extends the overall lifespan of the tire, increases thermal stability and enables sustainable use through multiple retreadings, thus meeting the growing demands for efficiency and environmental friendliness in the commercial vehicle sector.

[0015] Rolling resistance and durability are known to be influenced by the type and quantity of fillers used and by the crosslinking system. Rubber compounds in vehicle tires are generally reinforced with fillers, typically carbon black and / or silica. Switching to a carbon black with a lower surface area, for example, generally leads to a reduction in hysteresis (correlated with an improvement in rolling resistance), but simultaneously to a deterioration of properties important for durability. Conversely, switching from a carbon black with a lower surface area to one with a higher surface area results in worse hysteresis but improved durability.

[0016] The term "sulfur-cured rubber compound" refers to a rubber compound produced from a finished rubber compound (or raw rubber compound) through sulfur vulcanization. A sulfur-cured rubber compound is therefore a vulcanizate. Unless otherwise specified, the description of the individual components refers to the rubber compound before vulcanization, i.e., the sulfur-curable rubber compound. It is understood by those skilled in the art that the components may be in a modified form after vulcanization, which applies in particular to the rubbers (polymers), sulfur, and other components involved in the vulcanization process.

[0017] Rubber compounds for vehicle tires are typically crosslinked with sulfur, with the ratio of vulcanization accelerator to sulfur determining the efficiency of the sulfur network. A low ratio of vulcanization accelerator to sulfur, i.e., below 1:2, indicates conventional vulcanization and results in long sulfur chains. A high ratio indicates an efficient vulcanization system with shorter sulfur chains. Increasing the efficiency of the sulfur network generally improves durability (aging resistance), but increases rolling resistance.

[0018] High durability, especially resistance to aging, is crucial, particularly in the bead area of ​​pneumatic tires, as this area is subject to high mechanical and thermal stresses. At the same time, tire rolling resistance must be continuously reduced. However, areas of the pneumatic tire that are particularly stressed include – as mentioned – the rim profiles, also known as rim tape or bead protection strips, which are partially in direct contact with the outside air.

[0019] Surprisingly, it has been found that the specific combination of one or more carbon blacks, whose iodine value is between 55 and 80 g / kg on a weighted average, with a small amount of silica and a silane coupling agent and with a special efficient vulcanization system, each in the specified quantities in diene rubber mixtures, leads to a high durability of the vulcanizates through improved aging resistance, while simultaneously reducing hysteresis.

[0020] The unit phr (parts per hundred parts of rubber by weight) used in this document is the standard unit of measurement for compound formulations in the rubber industry. The dosage of the parts by weight of each substance is always based on 100 parts by weight of the total mass of all solid rubber components present in the mixture.

[0021] According to the invention, the rubber mixture contains at least one diene rubber. Diene rubbers are rubbers formed by the polymerization or copolymerization of dienes and / or cycloalkenes and thus exhibit C=C double bonds either in the main chain or in the side chains. The diene rubbers can be functionalized, modified, or coupled.

[0022] The diene rubber(s) is / are preferably selected from the group consisting of natural polyisoprene (NR), synthetic polyisoprene (IR), epoxidized polyisoprene (ENR), butadiene rubber (BR), butadiene-isoprene rubber, styrene-butadiene rubber (SBR), in particular solution-polymerized styrene-butadiene rubber (SSBR) and emulsion-polymerized styrene-butadiene rubber (ESBR), styrene-isoprene rubber, liquid rubbers with a molecular weight M wof greater than 20000 g / mol, halobutyl rubber, polynorbornene, isoprene-isobutylene copolymer, ethylene-propylene-diene rubber, nitrile rubber, chloroprene rubber, acrylate rubber, fluororubber, silicone rubber, polysulfide rubber, epichlorohydrin rubber, styrene-isoprene-butadiene terpolymer, hydrogenated acrylonitrile butadiene rubber and hydrogenated styrene-butadiene rubber.

[0023] In particular, nitrile rubber, hydrogenated acrylonitrile butadiene rubber, chloroprene rubber, butyl rubber, halobutyl rubber, or ethylene propylene diene monomer rubber are used in the manufacture of technical rubber articles such as belts, straps, and hoses, and / or shoe soles. The preferred application is of the compound compositions known to those skilled in the art for these rubbers—specifically with regard to fillers, plasticizers, vulcanization systems, and additives.

[0024] According to a particularly preferred embodiment of the invention, the diene rubber(s) is / are selected from the group consisting of natural polyisoprene (NR), synthetic polyisoprene (IR), butadiene rubber (BR), solution-polymerized styrene-butadiene rubber (SSBR), and emulsion-polymerized styrene-butadiene rubber (ESBR). Natural polyisoprene is understood to be rubber that can be obtained by harvesting from sources such as rubber trees (Hevea brasiliensis) or non-rubber tree sources (such as guayule or dandelion (e.g., Taraxacum koksaghyz)). Natural polyisoprene (NR) is understood to mean non-synthetic polyisoprene.

[0025] The butadiene rubber (= BR, polybutadiene) optionally contained in the rubber compound according to the invention can be any type known to those skilled in the art. This includes, among others, the so-called high-cis and low-cis types, whereby polybutadiene with a cis content greater than or equal to 90 wt.% is referred to as a high-cis type and polybutadiene with a cis content less than 90 wt.% as a low-cis type. For example, Li-BR (lithium-catalyzed butadiene rubber) with a cis content of 20 to 50 wt.% is a low-cis polybutadiene. Particularly good properties and low hysteresis of the rubber compound are achieved with a high-cis BR.

[0026] The polybutadiene(s) used may be end-modified and / or functionalized along the polymer chains. These modifications may involve hydroxy groups, ethoxy groups, epoxy groups, siloxane groups, amino groups, aminosiloxane, carboxy groups, phthalocyanine groups, and / or silane sulfide groups. Other modifications, also known as functionalizations, are also possible and are known to a qualified professional. Metal atoms may be part of such functionalizations.

[0027] In the event that at least one styrene-butadiene rubber (styrene-butadiene copolymer) is included in the rubber mixture, it can be either solution-polymerized styrene-butadiene rubber (SSBR) or emulsion-polymerized styrene-butadiene rubber (ESBR), and a mixture of at least one SSBR and at least one ESBR can also be used. The terms "styrene-butadiene rubber" and "styrene-butadiene copolymer" are used synonymously within the scope of the present invention.

[0028] The styrene-butadiene copolymer used can be end-group modified and / or functionalized along the polymer chains with the modifications and functionalizations mentioned above for polybutadiene.

[0029] For use of the rubber compound according to the invention in the horn profile of a vehicle pneumatic tire, the rubber compound preferably contains 20 to 50 phr of natural rubber (NR) and 50 to 80 phr of at least one butadiene rubber (BR).

[0030] The rubber compound according to the invention contains 40 to 90 phr, preferably 50 to 80 phr, of at least one carbon black, wherein the carbon black or blacks have, on average, an iodine value according to ASTM D 1510 of 55 to 80 g / kg. Accordingly, a carbon black with an iodine value according to ASTM D 1510 of 55 to 80 g / kg can be used in the compound, for example, carbon black of type N351 (iodine value: 68 g / kg). However, it is also possible to use two or more carbon blacks in the compound such that an average iodine value according to ASTM D 1510 of 55 to 80 g / kg is obtained. In this case, a blend of several carbon blacks is used.

[0031] The rubber compound contains 5 to 20 phr of at least one silica compound. Any silica compound known to those skilled in the art can be used, including those suitable for use in mixtures. Preferably, silica compounds with a nitrogen surface area (BET surface area) (according to DIN ISO 9277 and DIN 66132) of 35 to 400 m² are used. 2 / g, and a CTAB surface area (according to ASTM D 3765) of 30 to 400 m² 2 / g. Suitable silicas include, for example, those of the Ultrasil® VN3 type (trade name) from Evonik, as well as silicas such as Zeosil® 1115 or Zeosil® 1085 from Solvay, and highly dispersible silicas, so-called HD silicas (e.g., Zeosil® 1165 MP from Solvay). To improve the sustainability of the mixture, it is preferable to include silica produced from rice husk ash ("rice husk ash silica" (RHAS)).

[0032] It can be advantageous if the sulfur-curing rubber compound and / or the sulfur-curing rubber compound or rubber mixture of the radially outer apex portion and / or the sulfur-curing rubber compound or rubber mixture of the radially inner apex portion contain 5 to 20 phr of silica, preferably 10 to 20 phr of silica. Particularly preferably, both the sulfur-curing rubber compound or rubber mixture of the radially outer apex portion and the sulfur-curing rubber mixture of the horn profile contain 5 to 20 phr of silica, preferably 10 to 20 phr of silica.

[0033] With regard to sustainability, it may be advantageous if the rubber material of the radially outer apex part is made from a sulfur-curable rubber compound or rubber mixture and / or the rubber material of the radially inner apex part is made from a sulfur-curable rubber compound or rubber mixture containing silica produced from rice husk ash (“rice husk ash silica” (RHAS)).

[0034] In order to further increase the sustainability of commercial vehicle tires, in addition to improved retreadability and the advantageous use of RHAS, it may be advantageous if the sulfur-curing rubber compound and / or the sulfur-curing rubber compound or rubber compound of the radially outer apex part and / or the sulfur-curing rubber compound or rubber compound of the radially inner apex part contain at least 5 phr, preferably at least 10 phr, particularly preferably at least 15 phr, recycled materials.

[0035] According to the invention, recycled materials include all commonly used or novel recycled materials in industry, such as recovered carbon blacks (r-CB), regenerates from used tires and other used rubber articles (e.g., conveyor belts, V-belts, hoses) or plastic articles, as well as products from pyrolysis processes, including pyrolysis oil (TPO) and materials obtained therefrom such as light and heavy oils, carbon blacks (s-CB), resins (s-Resins) and process aids (s-Plasticizer).

[0036] To improve processability and to bind the silica to the diene monomer rubber of the mixtures, at least one of the mixtures contains at least one silane coupling agent, which is preferably used in amounts of 1–15 pph (parts by weight, based on 100 parts by weight of silica / silica) in the rubber mixture. The silane coupling agents can also be used in the mixture and / or differ between the mixtures.

[0037] The unit pph (parts per hundred parts of filler by weight) used in this document is the quantity commonly used in the rubber industry for coupling agents for polar fillers. In the context of this application, pph refers to the silica / silicic acid present, meaning that other fillers that may be present, such as carbon black, are not included in the calculation of the quantity of silane coupling agent.

[0038] The silane coupling agents react with the surface silanol groups of silica or other polar groups during the mixing of the rubber or rubber compound (in situ) or even before the addition of the filler to the rubber as a pretreatment (pre-modification). Any silane coupling agents known to those skilled in the art for use in rubber compounds can be used as such. Such coupling agents known from the prior art are bifunctional organosilanes that have at least one alkoxy, cycloalkoxy, or phenoxy group as a leaving group on the silicon atom and that possess, as a further functionality, a group which, if necessary after cleavage, can undergo a chemical reaction with the double bonds of the polymer. This latter group can be, for example, the following chemical groups: -SCN, -SH, -NH₂, or -S. x- (with x = 2-8). Thus, silane coupling agents can include, for example, 3-mercaptopropyltriethoxysilane, 3-thiocyanatopropyltrimethoxysilane, or 3,3'-bis(triethoxysilylpropyl)polysulfides with 2 to 8 sulfur atoms, such as 3,3'-bis(triethoxysilylpropyl)tetrasulfide (TESPT), the corresponding disulfide, or mixtures of the sulfides with 1 to 8 sulfur atoms and varying concentrations of the different sulfides. TESPT can also be added, for example, as a mixture with carbon black (trade name X50S from Degussa). Blocked mercaptosilanes, such as those known from WO 99 / 09036, can also be used as silane coupling agents. Silanes, as described in WO 2008 / 083241 A1, WO 2008 / 083242 A1, WO 2008 / 083243 A1 and WO 2008 / 083244 A1, can also be used. For example, silanes marketed under the name NXT are suitable. ®Various versions are available from the company Momentive, USA, or those marketed under the name VP Si 363 by Evonik Industries. So-called "silated core polysulfides" (SCP, polysulfides with a silylated core), described, for example, in US 20080161477 A1 and EP 2 114 961 B1, can also be used.

[0039] The rubber compound may contain other fillers, such as aluminosilicates, kaolin, chalk, starch, magnesium oxide, titanium dioxide, rubber gels, and fibers (such as aramid fibers, glass fibers, carbon fibers, cellulose fibers), carbon nanotubes (including discrete CNTs, so-called hollow carbon fibers (HCF), and modified CNTs containing one or more functional groups, such as hydroxy, carboxy, and carbonyl groups), graphite, graphene, or so-called "carbon-silica dual-phase fillers" in typical quantities, whereby the fillers may be used in combination.

[0040] A key feature of the invention is that the rubber compound has an efficient vulcanization system comprising at least one vulcanization accelerator and elemental sulfur, wherein the mass ratio of vulcanization accelerator to sulfur is 8:1 to 3:1, preferably 7:1 to 3:1, and particularly preferably 6:1 to 3.5:1. This enables crosslinking with short sulfur chains to form an efficient network.

[0041] The vulcanization accelerator(s) can be selected from all vulcanization accelerators known to those skilled in the art for sulfur vulcanization. These accelerators include thiazole accelerators, mercapto accelerators, sulfenamide accelerators, sulfenimide accelerators, thiocarbamate accelerators, thiuram accelerators, thiophosphate accelerators, thiourea accelerators, xanthate accelerators, and guanidine accelerators. For particularly good durability and low rolling resistance, the vulcanization accelerator(s) is preferably selected from the group consisting of mercapto accelerators, sulfenamide accelerators, sulfenimide accelerators, and guanidine accelerators.

[0042] All vulcanization accelerators can also be used in mixtures.

[0043] For good aging resistance of the vulcanizates, the rubber mixture preferably contains 0.5 to 1.5 phr sulfur.

[0044] Furthermore, the rubber compound may contain vulcanization retarders.

[0045] The terms “vulcanized” and “crosslinked” are used synonymously within the scope of the present invention.

[0046] The rubber compound according to the invention may further contain various plasticizers. These are preferably present in quantities of up to 50 phr in the compound.

[0047] Suitable plasticizers include, for example, those selected from the group consisting of plasticizers derived from renewable raw materials such as rapeseed oil or sunflower oil, or rubber-to-liquid (RTL) or biomass-to-liquid (BTL) oils, preferably with a polycyclic aromatic hydrocarbon content of less than 3 wt% according to method IP 346, or in particular resin acids or factisse or liquid polymers whose mean molecular weight (determined by GPC = gel permeation chromatography, in accordance with BS ISO 11344:2004) is between 500 and 20000 g / mol, mineral oils, phosphoric acid esters such as tri(2-ethylhexyl) phosphate, and liquid polymers with a weight-average molecular weight distribution M waccording to GPC of 60,000 g / mol or less. If additional liquid polymers are used as plasticizers in the rubber compound according to the invention, these are not included as rubber in the calculation of the polymer matrix composition. Preferably, DAE (Distilled Aromatic Extracts), RAE (Residual Aromatic Extract), TDAE (Treated Distilled Aromatic Extracts), MES (Mild Extracted Solvents), rapeseed oil and / or liquid diene polymers are used.

[0048] Furthermore, the rubber compound may contain common additives in usual proportions by weight, which are preferably added during its manufacture in at least one basic mixing stage. These additives include: a) Antioxidants, such as N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditolyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N,N'-di(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-di(1-ethyl,4-methylhexyl)-p-phenylenediamine (88PD), N,N'-bis-(1-ethyl-3-methylpentyl)-p-phenylenediamine (DOPD), and N,N'-di-[3-naphthyl-p-phenylenediamine (DNPD), 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ), b) Activators, such as zinc oxide (e.g., ZnO granules or powder; conventionally used zinc oxide typically has a BET surface area of ​​less than 10 m²). 2 / g. However, it can also be a zinc oxide with a BET surface area of ​​10 to 100 m². 2 / g, such as so-called “nano-zinc oxides”, are used) and fatty acids (e.g. stearic acid) or zinc complexes such as zinc ethylhexanoate, c) Resins, such as phenolic resins, in particular adhesive resins. Natural or synthetic resins, such as hydrocarbon resins, can be used as adhesive resins, acting as tackifiers. The hydrocarbon resins can be phenolic, aromatic, or aliphatic. Preferably, the adhesive resins are selected from the group consisting of rosin resins and their esters, terpene phenolic resins, alkyne phenolic resins, phenolic resins, and coumaron indene resins, with phenolic resins being particularly well suited for the present invention. d) Mastication aids, such as 2,2'-dibenzamidodiphenyl disulfide (DBD), and e) Processing aids, such as fatty acid salts, such as zinc soaps, and fatty acid esters and their derivatives.

[0049] The quantity of other additives in the total quantity is 3 to 150 phr, preferably 3 to 100 phr and particularly preferably 5 to 80 phr.

[0050] The rubber compound is produced according to a process customary in the rubber industry, in which a base mixture containing all components except the vulcanization system (sulfur and vulcanization-influencing substances) is first prepared in one or more mixing stages. The finished mixture is then produced by adding the vulcanization system in a final mixing stage. This finished mixture is further processed, for example, by extrusion, and formed into the desired shape. Subsequent processing is carried out by vulcanization, whereby sulfur crosslinking occurs due to the vulcanization system added within the scope of the present invention.

[0051] This rubber compound can be used for a wide variety of rubber products where low hysteresis and high durability and aging resistance are advantageous. It is preferably used in the manufacture of vehicle tires, such as car, van, truck, or motorcycle tires. It can be used in various components of vehicle tires, especially pneumatic tires. These components can include, for example, compounds in the bead and sidewall areas, such as the apex, parts of the apex, parts of the sidewall, or crescent-shaped inserts in the sidewall area.

[0052] According to the invention, the rubber compound is used as a rim profile for commercial vehicle tires. Tires with a rim profile made from the compound according to the invention are characterized by low rolling resistance and high durability.

[0053] In the production of commercial vehicle tires, the mixture is brought into the shape of the relevant component, namely the horn profile, as a ready-made mixture before vulcanization and applied as usual during the production of the vehicle tire blank.

[0054] The invention encompasses all advantageous embodiments, which are reflected, inter alia, in the claims. In particular, the invention also encompasses embodiments resulting from the combination of different features, for example, components of the rubber compound, and different degrees of preference given to these features, such that a combination of a first feature designated as "preferred" or described within the framework of an advantageous embodiment with a further feature designated, for example, as "particularly preferred," is also covered by the invention.

[0055] The invention will now be explained in more detail with reference to comparative and exemplary embodiments, which are summarized in Table 1. The comparative mixtures are marked with V, and the mixture according to the invention is marked with E.

[0056] The compound was prepared according to standard rubber industry procedures under typical conditions in three stages using a laboratory mixer. In the first two stages (basic mixing stages), all components except the vulcanization system (sulfur and vulcanization-influencing substances) were mixed. The final compound was then produced by adding the vulcanization system in the third stage (final mixing stage), with mixing taking place at 90 to 120 °C.

[0057] Test specimens were produced from all mixtures by vulcanization for 15 minutes under pressure at 160 °C, and material properties typical for the rubber industry were determined using these test specimens with the test procedures specified below: - Network node spacing according to differential scanning calorimetry: This method utilizes the fact that the liquid-solid phase transition of a swelling agent within a swollen polymer network depends on the crosslinking density. Samples of the respective rubber compound are swollen with cyclohexane as a swelling agent; for this purpose, the respective sample is extracted with cyclohexane and then allowed to swell further at room temperature (RT). Subsequently, the freezing point depression of cyclohexane in the network is determined compared to the macroscopically extended liquid phase: The prepared sample is cooled in the measuring apparatus, and the heat flux is recorded. Two freezing peaks are observed: the peak of pure cyclohexane at approximately 3°C and another peak of the cyclohexane present in the swollen sample. The network node spacing is calculated from the temperature difference. - Shore A hardness at room temperature according to ISO 868 - Rebound elasticity at 70 °C according to ISO 4662 - Elongation at break at room temperature according to DIN 53504. The samples were measured before and after aging: aging in air for 14 days at 80 °C. - Fatigue crack resistance (fatigue fracture life) as the number of load cycles in kilocycles (kC) until failure of a dumbbell-shaped specimen with a thickness of 1.35 to 1.55 mm and a length and width of 230 mm * 76 mm (based on a standard bar S2 described in DIN 53504) under a continuously repeating strain cycle with a frequency of 10⁴ ± 8 min⁻¹, determined using a Monsanto Fatigue to Failure Tester (FTF) at room temperature (RT, 23 °C ± 2 °C). Six specimens of a rubber compound are measured, and the load cycles achieved for each are used to calculate the median for each rubber compound. The median represents the test result for each rubber compound, as shown in Table 1. The specimens were measured before and after aging: aging in air for 14 days at 80 °C. The unaged samples were measured at a preload of 89%, the aged samples at a preload of 61%.

[0058] High rebound elasticity at 70 °C (equivalent to reduced hysteresis) can be correlated with low rolling resistance when the compound is used in vehicle tires. Furthermore, the reduced hysteresis results in less heat generation, allowing the tread profile to run cooler and therefore age more slowly, which has a positive effect on durability. Table 1 Components Unit 1(V) 2(V) 3(V) 4(V) 5(V) 6(E) natural rubber phr 30 30 30 30 30 30 BR a phr 70 70 70 70 70 70 Soot N339 b phr 70 70 0 62 0 0 Soot N351 c phr 0 0 66,5 0 57 57 Silica d phr 0 0 0 10 10 10 Silane coupling agent e phr 0 0 0 0,72 0,72 0,72 Plasticizer oil phr 5 5 5 5 5 5 zinc oxide phr 3 3 3 3 3 3 Stearic acid phr 2 2 2 2 2 2 Anti-aging agents phr 3 3 3 3 3 3 Ozone protection wax phr 2 2 2 2 2 2 Adhesive resin phr 5 5 5 5 5 5 TBBS f phr 2,5 4,3 2,5 3,5 3,5 5,3 sulfur phr 2,5 1,01 2,5 2,5 2,5 1,01 Characteristics Network node spacing nm 4,2 3,7 3,0 3,7 3,6 3,8 Shore hardness at RT Shore A 73,6 72,3 75,8 75,0 73,9 73,3 Rebound strength at 70 °C % 58,6 57,8 64,0 59,7 62,8 61,2 Elongation at break (unrestrained) % 225 208 153 204 211 226 Elongation at break (aged) % 106 151 95 93 104 138 Fatigue crack resistance (unprotected) kC 69 101 8 25 38 87 Fatigue crack resistance (aged) kC 14 20 1 15 5 70 a high-cis polybutadiene rubber b Carbon black N339, iodine value: 90 g / kg c Carbon black N351, iodine value: 68 g / kg d Ultrasil ® VN3, Evonik, nitrogen surface area = 180 m² 2 / g, CTAB 165 m 2 / G e TESPD (3,3'-Bis(triethoxysilylpropyl)disulfide), Si266, Evonik f N-tert-Butyl-2-benzothiazylsulfenamid

[0059] The data in Table 1 show the effects of the individual measures: efficient vulcanization system only (2(V)), carbon black with medium iodine value only (3(V)), silica with silane coupling agent only (4(V)), and the combined measure of carbon black with medium iodine value and silica with silane coupling agent (5(V)). None of the comparison compounds simultaneously achieves high durability even after aging (evident from the elongation at break values) while maintaining low rolling resistance (deducible from the rebound elasticity values ​​at 70 °C).

[0060] Only the special compound 6(E) can resolve this conflict of objectives in a surprising way. Rebound elasticity at 70 °C and elongation at break, with and without aging, behave in a manner that far exceeds the expected effects of the respective individual measures.

[0061] A significant improvement in durability is also evident in the markedly improved fatigue crack resistance, particularly after aging. The sample made from the special mixture 6(E) withstood significantly more load cycles after aging at 70 kC than all other samples, which was unexpected.

[0062] According to a preferred embodiment, the cross-sectional area of ​​the radially inner apex portion is 70% to 140%, in particular 75% to 130%, preferably 80% to 120%, and most preferably up to 100%, of the cross-sectional area of ​​the bead core. This is particularly advantageous with regard to the conflict of objectives to be resolved.

[0063] According to a further preferred embodiment, the stress value at 100% elongation of the rubber material of the radially inner apex portion is 3.00 MPa to 25.00 MPa, preferably 4.00 MPa to 18.00 MPa, particularly preferably 4.50 MPa to 16.00 MPa, and most preferably 6.00 MPa to 12.00 MPa greater than the stress value at 100% elongation of the rubber material of the radially outer apex portion. These differences have proven to be particularly advantageous for the bead durability of the tire.

[0064] Additionally, it is advantageous for bead durability if the stress value at 100% elongation of the rubber material of the radially outer apex part is 0.50 MPa to 9.00 MPa, in particular 0.75 MPa to 7.50 MPa, preferably 1.00 MPa to 6.00 MPa, and particularly preferably 2.50 MPa to 5.00 MPa.

[0065] Another preferred embodiment is characterized in that the rebound elasticity at 70°C of the rubber material of the radially outer apex part is 7.5 percentage points to 45.0 percentage points, preferably 9.0 percentage points to 40.0 percentage points, and particularly preferably 10.0 percentage points to 30.0 percentage points, greater than the rebound elasticity at 70°C of the rubber material of the radially inner apex part. This contributes to a further reduction in the rolling resistance of the tire.

[0066] Furthermore, it is advantageous for the tire's rolling resistance if the rebound elasticity at 70°C of the rubber material of the radially inner apex portion is 25% to 65%, particularly 30% to 60%, and preferably at least 45%. This increased rebound elasticity not only contributes to lower rolling resistance but also indicates lower hysteresis and, consequently, lower heat build-up, thus contributing to improved durability.

[0067] It can be advantageous if the sum of the rebound elasticity, expressed as a percentage, of the sulfur-curing rubber compound and the sulfur-curing rubber compound of the radially outer apex, tested at 70°C – each determined according to ISO 4662 using a test specimen with a thickness of 6.3 mm ± 0.5 mm according to Annex A – is greater than 110 percentage points, preferably greater than 115 percentage points, and particularly preferably greater than 120 percentage points. In this particularly advantageous combination, very little heat is generated in both the radially outer region of the bead and the radially innermost region of the bead (at the horn profile), thereby significantly increasing the durability in these two areas relevant for retreadability.

[0068] According to a further preferred embodiment, the carcass ply is single-layered and terminates in each bead area as a carcass bulge with a radially determined height, wherein the radially inner apex portion, on its side facing the inner tire and contacting the carcass ply, has a radially determined maximum height of 60% to 100%, in particular 70% to 90%, of the carcass bulge height, wherein the maximum height and the height refer to a line which, viewed in the tire cross-section, runs axially through a point on the bead area of ​​the commercial vehicle tire corresponding to the rim corner. This embodiment also offers additional advantages for rolling resistance and bead durability.

[0069] According to an alternative further preferred embodiment, the carcass ply is multi-layered, with each layer of the carcass ply terminating in each bead area as a carcass bulge with a radially determined height, wherein the radially inner apex portion, on its side facing the inner surface of the tire and contacting the carcass ply, has a radially determined maximum height of 60% to 100%, in particular 70% to 90%, of the height of the highest carcass bulge, wherein the maximum height and the height are referenced to a reference line L which, viewed in the tire cross-section, runs axially through a point on the bead area of ​​the commercial vehicle tire corresponding to the rim corner. This embodiment is also advantageous for rolling resistance and bead durability.

[0070] In the latter two preferred embodiments, the radial height of the carcass rise in relation to the reference line L is in particular 25.0 mm to 50.0 mm, preferably 30.0 mm to 450 mm.

[0071] Preferably, the cross-sectional area of ​​the radially inner apex portion is triangular, with the radially inner apex portion tapering at its end facing away from the bead core. This design is further advantageous with regard to the trade-off between rolling resistance and bead durability.

[0072] Furthermore, in the latter two designs, it is advantageous if the radially outer apex part, viewed in the tire cross-section, runs between the carcass high point and the radially inner apex part.

[0073] Preferably, the commercial vehicle tire is intended for mounting on a 15° deep-dish rim standardized according to ETRTO standards with a width code of 5.25 to 18.00.

[0074] Therefore, the use of the commercial vehicle tire according to the invention on a 15° deep-bed rim standardized according to ETRTO standards with a width code of 5.25 to 18.00 is particularly advantageous.

[0075] Further features, advantages and details of the invention will now be explained with reference to the single figure, Fig. Figure 1, which schematically shows a cross-section through one of the bead areas of a commercial vehicle tire with an embodiment of the invention, is explained.

[0076] Commercial vehicle tires designed according to the invention are tires for multi-track commercial vehicles, preferably for medium-weight trucks (7.5 t < GVW S 18.0 t), for heavy-duty trucks (GVW > 18.0 t) or for buses, and in particular commercial vehicle tires of radial design.

[0077] The heights specified below are measured radially (indicated by the double arrow R) and refer to a line L which, when viewed in cross-section of a suitable, uninflated commercial vehicle tire mounted on a rim, runs axially (indicated by the double arrow A) through a point X corresponding to the rim corner on the respective bead area of ​​the commercial vehicle tire. The axial direction is understood to be the direction parallel to the axis of rotation of the commercial vehicle tire. The radial direction corresponds to the direction perpendicular to the axial direction in the tire cross-section. The rim corner is, as is known, the intersection of the rim shoulder with the rim flange. The heights are determined using a section of the tire circumference cut from a vulcanized pneumatic vehicle tire and mounted on a rim.Alternatively, the heights can be determined using computed tomography.

[0078] Fig. Figure 1 shows a cross-section through a bead area of ​​a vulcanized commercial vehicle tire. The second bead area, not shown, is constructed identically to the bead area shown.

[0079] The commercial vehicle tire is specifically designed for mounting on a 15° drop-center rim, which, according to the European Tyre and Rim Technical Organisation Standards Manual (“ETRTO Standards”) in its currently valid version (as of October 2024), section 15° Drop-Center Rims (width codes 5.25 to 18.00), has nominal diameters of 17.5 inches, 19.5 inches, 20.5 inches, 22.5 inches or 24.5 inches.

[0080] In Fig.Figure 1 shows the following components of the commercial vehicle tire: a section of an airtight inner layer 1, a section of a sidewall 2, a horn profile 3, a section of a single-ply carcass ply 4, a bead core 5, a two-part apex 6 sitting on the bead core 5, a bead flap 7, a steel cord bead reinforcement 8, a filler profile 9, and a filler profile 10. All of these components extend around the entire circumference of the tire; they are therefore ring-shaped components.

[0081] The sidewall 2 typically overlaps the horn profile 3 on the outer side of the tire. The carcass ply 4 consists of steel cords embedded in rubber, running without crossings and essentially parallel to each other. The carcass ply 4 runs in a known manner between the two bead cores 5, is folded around each bead core 5 from the inner side of the tire (facing the inner layer 1) towards the outer side of the tire, and terminates on the outer side of the tire next to the apex 6 as a carcass fold 4a at a height h1 of 25.0 mm to 50.0 mm, preferably 30.0 mm to 45.0 mm. The bead flap 7 consists of a rubberized textile fabric, in particular rubberized nylon fabric, and is wrapped around the bead core 5 in such a way that it separates the carcass ply 4 from the bead core 5.The steel cord bead reinforcement 8 consists of steel cords embedded in rubber, running without crossings and essentially parallel to each other. It runs in contact with the side of the carcass insert 4 facing away from the bead core 5 and terminates on both the inner and outer sides of the tire in the region of the apex 6, ending on the outer side before the end of the carcass high-profile 4a. The filler profile 9 is located on the outer side of the tire, between the bead core 5 and the apex 6. It runs – in sections – between the steel cord bead reinforcement 8 and the horn profile 3, between the carcass high-profile 4a and the horn profile 3, and between the apex 6 and the horn profile 3 or the sidewall 2.The filling profile 10 runs between the two bead areas, is located in each bead area on the inside of the bead core 5 and the apex 6 and runs in each bead area sectionally between the steel cord bead reinforcement 8 and the inner layer 1 as well as sectionally between the inner layer 1 and the carcass insert 4.

[0082] The bead core 5 consists of a circumferentially circulating, tensile-resistant core wire 5a embedded in rubber material, which is preferably made of metal and has a circular cross-section. The bead core 5a is formed in a known manner by winding a single core wire 5a embedded in rubber material or by winding a plurality of core wires 5a embedded in rubber material. Viewed in the tire cross-section, the bead core 5 has a cross-sectional area A5. For a bead core 5 consisting of a single core wire 5a, the cross-sectional area A5 of the bead core 5 is calculated by multiplying the maximum number of turns by the cross-sectional area of ​​the core wire 5a. The number of turns can vary by one turn, depending on the location of the cross-section.The "maximum number of turns" is the number of turns at a point where the greatest number of turns is found. For a bead core 5 made of a multitude of core wires 5a, the cross-sectional area A5 of the bead core 5 is calculated by multiplying the number of core wires 5a by the cross-sectional area of ​​a single core wire 5a. Therefore, the rubber material surrounding the core wire(s) 5a is not taken into account when determining the area A5.

[0083] The two-part apex 6 consists of a radially outer apex part 6a, made of a rubber material and preferably not in contact with the bead core 5, and a radially inner apex part 6b, also made of a rubber material and in contact with the bead core 5. The rubber materials of the apex parts 6a and 6b differ with respect to their tensile strength at 100% elongation and their rebound elasticity at 70°C, as will be explained below. In the illustrated embodiment, the radially inner apex part 6b, viewed in the tire cross-section, has a substantially triangular cross-sectional area, extends at its end facing away from the bead core 5 along a section of the carcass insert 4 running inside the tire and reaches to a maximum height h2 (height at the highest point), which is 60% to 100%, in particular 70% to 90%, of the aforementioned height h1 of the carcass high-profile 4a.The cross-sectional area of ​​the radially inner apex part 6b has an area A. 6b on, which is 60% to 160%, in particular 70% to 140%, preferably 75% to 130%, particularly preferably 80% to 120%, most preferably up to 100%, of the area A5 of the cross-sectional area of ​​the bead core 5.

[0084] The radially outer apex part 6a, viewed in the tire cross-section, extends between the carcass high-lap 4a and the radially inner apex part 6b, thus separating the radially inner apex part 6b from the carcass high-lap 4a together with the core flap 7 and extends in a radial direction to a height ho which is greater than the already mentioned height h1 of the carcass high-lap 4a.

[0085] The stress values ​​already mentioned at 100% elongation were determined according to DIN 53504 (Testing of rubber and elastomers - Determination of tensile strength, tensile strength, elongation at break and stress values ​​in tensile testing (edition 2017-03), test specimen type S3).

[0086] The rebound elasticity at 70°C was determined according to ISO 4662 (Elastomers or thermoplastic elastomers - Determination of rebound elasticity of vulcanizates (Edition 2017-06, Pendulum method according to Section 5)), with the thickness of the test piece being 6.3 mm ± 0.5 mm as mentioned in Annex A (Use of non-standard test pieces).

[0087] The rebound elasticity at 70°C serves as an indicator of the tire's rolling resistance, with high rebound elasticity at 70°C indicating low rolling resistance.

[0088] The rubber material of the radially outer apex part 6a has a stress value at 100% elongation of 0.50 MPa to 9.00 MPa, in particular 0.75 MPa to 7.50 MPa, preferably 1.00 MPa to 6.00 MPa, and particularly preferably 2.50 MPa to 5.00 MPa. The rubber material of the radially inner apex part 6b has a stress value at 100% elongation which is 2.00 MPa to 30.00 MPa, in particular 3.00 MPa to 25.00 MPa, preferably 4.00 MPa to 18.00 MPa, particularly preferably 4.50 MPa to 16.00 MPa, most preferably 6.00 MPa to 12.00 MPa greater than the stress value at 100% elongation of the rubber material of the radially outer apex part 6a.

[0089] The rubber material of the radially outer apex part 6a further exhibits a rebound elasticity at 70°C which is 5.0 percentage points to 50.0 percentage points, in particular 7.5 percentage points to 45.0 percentage points, preferably 9.0 percentage points to 40.0 percentage points, and particularly preferably 10.0 percentage points to 30.0 percentage points, greater than the rebound elasticity at 70°C of the rubber material of the radially inner apex part 6b.

[0090] The rubber material of the radially inner apex part 6b exhibits a rebound elasticity at 70°C of 25% to 65%, particularly 30% to 60%, and preferably at least 45%. In this preferred embodiment, the radially inner and radially outer apex compounds, as well as the horn profile compound, exhibit particularly advantageous, high rebound elasticities and thus contribute significantly to the low heat generation and therefore significantly to the improved durability of the bead.

[0091] In the illustrated embodiment, three circumferential rubber reinforcement strips 11, 12, 13 are installed on the outer side of the tire at the apex 6. Reinforcement strip 11 runs between the carcass bead 4a and the steel cord bead reinforcement 8. Reinforcement strip 12 runs along its entire length in contact with the filler profile 9 and, in sections, in contact with the steel cord bead reinforcement 8, the carcass bead 4a, and the radially outer apex portion 6a. Reinforcement strip 13 covers the free end of the carcass bead 4a and, in sections, runs in contact with the radially outer apex portion 6a and reinforcement strip 12.

[0092] WO 2024 / 022560 A1 shows that the commercial vehicle tire according to WO 2024 / 022560 A1 has a significantly lower rolling resistance than the reference tire Ref. 1 listed therein, and its bead durability remains unchanged. Furthermore, WO 2024 / 022560 A1 shows that the commercial vehicle tire according to WO 2024 / 022560 A1, compared to reference tire Ref. 2, has unchanged rolling resistance and is significantly improved with regard to bead durability.

[0093] The invention is not limited to the described embodiment.

[0094] In the bead area of ​​the tire, additional reinforcing layers containing strengthening elements, as well as further reinforcing strips made of rubber, may be installed. The carcass ply 4 may be multi-layered, in particular two- or three-layered. In a multi-layered carcass ply, the carcass ridges of the carcass ply layers may terminate at different heights. The radially inner apex part 6b may, viewed in the tire cross-section, have a cross-sectional area that deviates from the triangular cross-sectional area. The previously mentioned maximum height h2 of the radially inner apex part 6b is 60% to 100%, in particular 70% to 90%, of the height of the highest carcass ridge. The core flap 7, the steel cord bead reinforcement 8, and the reinforcing strips 11, 12, 13 are optional. The cross-sectional area of ​​the bead core is in particular hexagonal or circular. Alternatively, the cross-sectional area of ​​the bead core has a hexagonal shape.a shape derived from a circle. One such derived shape is, for example, a cross-sectional area in the shape of a hexagon with a corner area cut out in an approximately parallelogram-shaped manner. Reference symbol list 1 inner layer 2 side wall 3 Horn profile 4 Carcass insert 4a Carcass high impact 5 bead core 5a Core wire 6 Apex 6a radial outer apex part 6b radial inner apex part 7 core flag 8 steel cord bead reinforcements 9 Fill profile 10 Fill profile 11 Reinforcement layer 12 Reinforcement layer 13 Reinforcement layer A double arrow (axial direction) A5, A 6b area h0, h1 height h2 maximum height L line R double arrow (radial direction) X point QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2024 / 022560 A1 [0002, 0010, 0011, 0092] WO 99 / 09036

[0038] WO 2008 / 083241 A1

[0038] WO 2008 / 083242 A1

[0038] WO 2008 / 083243 A1

[0038] WO 2008 / 083244 A1

[0038] US 20080161477 A1

[0038] EP 2 114 961 B1

[0038] Cited non-patent literature

[0000] DIN 53504 (Testing of rubber and elastomers - Determination of tensile strength, tensile strength, elongation at break and stress values ​​in tensile testing (Edition 2017-03

[0085] ISO 4662 (Elastomers or thermoplastic elastomers - Determination of rebound elasticity of vulcanizates (Edition 2017-06, Pendulum

[0086]

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