Vehicle tyre and tread

Abstract

The invention relates to a vehicle tyre which contains, at least in a tread (1), a vulcanizate which is obtained by sulfur vulcanization of a rubber mixture, wherein one or more electrically conductive radially running rubber components (9) are arranged in the tread, extend radially outwards as far as the outer surface of the tread (1) and extend radially inwards as far as an electrically conductive inner rubber part of the vehicle tyre. The rubber mixture contains 25 to 100 phr of at least one butadiene rubber, wherein the butadiene rubber has a glass transition temperature Tg below -75°C, and 20 to 70 phr of at least one silicic acid, and carbon black as a filler.

Description

[0001] Description

[0002] Vehicle tires and treads

[0003] The invention relates to a vehicle tire, in particular a commercial vehicle tire. Furthermore, the invention relates to the tread of a commercial vehicle tire and the use of a sulfur-curable rubber compound for the tread.

[0004] The rubber composition of the tread largely determines the properties of a vehicle tire. Therefore, very high demands are placed on these rubber compounds for the tread, especially with regard to tire rolling resistance. The terms "tread" and "tread surface" are to be considered synonymous in this text.

[0005] The rolling resistance (RR) of tires is frequently measured using drum tests. Drum tests are generally the basis for legal rolling resistance certifications, the awarding of rolling resistance labels, or the verification of rolling resistance limit requirements. These drum tests are typically based on tests according to ISO 28580. ISO 28580 specifies a target ambient temperature of 25 °C for the rolling resistance test and also provides a linear rolling resistance correction formula for test temperatures between 20 °C and 30 °C.

[0006] Little has been published to date regarding the influence of low or very low ambient temperatures (e.g., below 0 °C) on tire rolling resistance, specifically for truck and / or bus tires. The available correction formula for the effect of ambient temperature on rolling resistance is only valid for a temperature range of 20 °C to 30 °C. Furthermore, this correction formula does not consider individual tire characteristics and technologies, such as the tread pattern, the rubber compounds used, the tire construction, the tire contour, etc. It is based solely on the measured rolling resistance value with fixed input values ​​and only distinguishes between "passenger car tires," "smaller truck and bus tires," and "larger truck and bus tires."

[0007] The present invention was based on the objective of providing a rubber compound for treads and a corresponding tread which, compared to the prior art, exhibits an improvement in the property profile, particularly with regard to the rolling resistance behavior at low ambient temperatures below standard room temperature and the temperature sensitivity of the rolling resistance behavior.

[0008] Surprisingly, the rubber compound, vulcanizate, tread strip and vehicle tire according to the invention achieve an improvement in rolling resistance behavior, especially at low ambient temperatures.

[0009] 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 or elements of the tire, with varying 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 encompassed by the invention.

[0010] The following section describes in more detail the components of the rubber compound according to the invention and the properties of the tread strip produced therefrom.

[0011] All information regarding the components of the rubber compound according to the invention, regardless of the degree of preference given to these features, also applies accordingly to the vulcanizate according to the invention, the tread according to the invention, the (commercial) vehicle tire according to the invention, and uses according to the invention. The unit phr (parts per hundred parts of rubber by weight) used in this document is the quantity commonly used in the rubber industry for compound formulations. The dosage of the parts by weight of the individual substances is given in this document as a percentage of 100 parts by weight of the total mass of all rubbers present in the compound with a molecular weight Mw according to GPC greater than 20,000 g / mol. The specified value ranges always include the limit values.

[0012] According to the invention, the rubber mixture further contains at least one diene rubber, which is a butadiene rubber (synonyms: BR, BR rubber, polybutadiene).

[0013] Diene rubbers are rubbers that are formed by polymerization or copolymerization of dienes and / or cycloalkenes and thus have C=C double bonds either in the main chain or in the side groups.

[0014] According to the invention, the proportion of BR in the rubber mixture is at least 25 phr and at most 100 phr. In the latter case, the rubber component of the rubber mixture consists of BR.

[0015] Preferably, the proportion of BR in the rubber mixture is at least 30 phr, more preferably at least 40 phr, more preferably at least 50 phr, and even more preferably at least 60 phr.

[0016] Preferably, the proportion of BR in the rubber compound is a maximum of 90 phr, more preferably a maximum of 80 phr, and even more preferably a maximum of 70 phr. The butadiene rubber is, in particular, not one of the other possible diene rubbers listed below.

[0017] According to the invention, the rubber mixture can further contain at least one diene rubber from the group consisting of natural polyisoprene (NR) and synthetic polyisoprene (IR) with a proportion of at most 75 phr, preferably between 10 and 70 phr including 10, more preferably 10 to 60 phr, and particularly preferably 20 to 60 phr.

[0018] According to the invention, the rubber mixture can further contain the diene rubber styrene-butadiene rubber (SBR), in particular solution-polymerized styrene-butadiene rubber (SSBR) or emulsion-polymerized styrene-butadiene rubber (ESBR). According to the invention, the proportion of SBR in the rubber mixture is at most as high as the total proportion of polyisoprene, i.e., NR and IR.

[0019] Other possible diene rubbers that may be present in smaller quantities in the mixture according to the invention are butadiene-isoprene rubber, styrene-isoprene rubber, halobutyl rubber, polynorbornene, isoprene-isobutylene copolymer, ethylene-propylene diene rubber, nitrile rubber, chloroprene rubber, acrylate rubber, fluorocarbon rubber, silicone rubber, polysulfide rubber, epichlorohydrin rubber, styrene-isoprene-butadiene terpolymer, hydrogenated acrylonitrile butadiene rubber and hydrogenated styrene-butadiene rubber.

[0020] In this process, plasticizers, vulcanization systems and additives known to experts for these rubbers are used preferentially.

[0021] With the proportions of butadiene rubber (BR) and NR or IR according to the invention, the problem underlying the invention is solved particularly well and a tread strip produced from the rubber mixture exhibits good rolling resistance behavior, especially at low temperatures.

[0022] Preferably, the rubber mixture contains only NR or only IR.

[0023] Preferably, the proportions of NR, IR and BR add up to approximately 100 phr or exactly 100 phr.

[0024] In the event that the rubber mixture contains less than 100 phr of NR, IR and BR, at least one further rubber, preferably at least one further diene rubber selected from the above list, is included, such that the sum of the contained rubbers by definition equals 100 phr.

[0025] The BR rubber used in the present rubber compound can be polymerized using organometallic catalysts, e.g. with neodymium, cobalt, titanium, nickel, lithium, sodium or other catalysts or Ziegler-Natta catalysts.

[0026] It can be BR rubber with a high cis content (high-cis) or low cis content (low-cis), or with a high or low trans content.

[0027] The butadiene rubber (polybutadiene, BR) contained in the rubber compound according to the invention is particularly preferably of the low-cis type. The so-called high-cis and low-cis types are understood to be polybutadienes with a cis content greater than or equal to 90 wt.% (weight %, high-cis type) and polybutadienes with a cis content less than 90 wt.% (low-cis type), respectively.

[0028] The polybutadienes used can preferably be end-group modified and / or functionalized along the polymer chains with modifications and functionalizations according to the fillers used. The polybutadienes can be simply or multiple times modified. The modifications can include hydroxy groups, ethoxy groups, epoxy groups, siloxane groups, amino groups, aminosiloxane groups, carboxy groups, phthalocyanine groups, and / or silane sulfide groups. Other modifications, also known as functionalizations, are also possible and are known to a competent person. Metal atoms can be part of such functionalizations. These functionalizations or modifications can be specifically selected or developed for the filler used, e.g., specifically for silica or carbon black fillers.

[0029] The BR rubber used in the present rubber compound is preferably a BR specifically functionalized for the binding of silica, which preferably has a low glass transition temperature. The terms "silica," "silicon dioxide," and "silicon dioxide" are used synonymously within the scope of the present invention. The BR rubber functionalized for silica is preferably mixed in the present rubber compound with high-surface-area silica, as specified in more detail below.

[0030] Preferably, the chain ends of the BR rubber used in the present rubber compound are functionalized for the attachment of silicas.

[0031] The functionalized BR rubber can have several functionalizations and, for example, can also be functionalized for interaction with carbon black.

[0032] The glass transition temperature (Tg) of the BR is preferably below - 75 °C, more preferably below - 85 °C, and even more preferably below - 90 °C.

[0033] The BR rubber used in the present rubber compound preferably has a molar mass between 300,000 and 600,000 g / mol.

[0034] It is also possible to mix several of the aforementioned BR rubbers.

[0035] The combination results in an unexpectedly significant performance advantage for the rubber compound. It unexpectedly shows a marked improvement in rolling resistance at low temperatures and lower temperature sensitivity, meaning less change in rolling resistance with changes in ambient temperature.

[0036] An exemplary BR rubber suitable for use in the present invention is, for example, KBR820 from KKPC (Tg = -92 °C, functionalized, 40.5% cis content and 12% vinyl content, high silica affinity). The percentages given are by weight.

[0037] The BR used can be crude oil-based. Preferably, the BR used can also be partially or fully based on recycled, renewable, and / or bio-based raw materials. This BR from renewable raw materials can be obtained, for example, from wood, beets, potatoes (peels), fruits (skin), or byproducts of biodiesel production, such as glycerin.

[0038] All rubber materials used can be based on recycled, renewable and / or bio-based raw materials or on recycled material, e.g. recycled rubber, in particular recycled natural rubber or IR / BR recycled rubber.

[0039] According to the invention, the rubber mixture contains as a further component 20 to 70 phr, preferably 30 to 70 phr, particularly preferably 40 to 60 phr, more preferably 45 to 55 phr of at least one silica.

[0040] The at least one silica has a mean nitrogen surface area (BET surface area) according to DIN ISO 9277 of at least 80 m2 / g (square meters per gram).

[0041] The silica preferably has a CTAB surface area according to ASTM D 3765 of at least 80 m2 / g.

[0042] The at least one silica is preferably amorphous silica, preferably precipitated silica.

[0043] The high silica content in the rubber compound results in advantageous wet braking properties.

[0044] Surprisingly, the present composition has succeeded in achieving good rolling resistance behavior, especially at low temperatures.

[0045] A suitable silica with a CTAB surface area of ​​245 to 255 m² / g is available, for example, under the trade name Premium SW from Solvay Silica Korea Co., Ltd. The rubber compound according to the invention may also contain at least one further filler.

[0046] Other reinforcing fillers are in particular carbon blacks, preferably selected from industrial carbon blacks and pyrolysis carbon blacks, with industrial carbon blacks being further preferred.

[0047] The carbon blacks known to those skilled in the art for rubber mixtures can be used, with a proportion of a maximum of 18 phr, preferably a maximum of 10 phr, more preferably a maximum of 5 phr.

[0048] In one embodiment, the carbon black has an iodine number, according to ASTM D 1510, also referred to as the iodine adsorption number, between 10 and 250 g / kg, preferably 30 to 180 g / kg, particularly preferably 40 to 180 g / kg, and most preferably 40 to 130 g / kg, and a DBP number according to ASTM D 2414 of 40 to 250 mL / 100g, preferably 80 to 200 mL / 100g, and particularly preferably 100 to 200 mL / 100g. A carbon black with an iodine adsorption number between 80 and 110 g / kg and a DBP number of 100 to 130 mL / 100g, such as carbon blacks of type N339, is particularly suitable and preferred.

[0049] The DBP number according to ASTM D 2414 determines the specific absorption volume of a carbon black or a light filler using dibutyl phthalate.

[0050] The carbon blacks used also include so-called "recovered" carbon blacks, meaning carbon blacks that have been reclaimed or recycled. The carbon blacks used may also be oxidized.

[0051] The filler used (e.g., carbon black or silica or other fillers) can consist partially or completely of recycled, renewable, and / or bio-based material, e.g., recovered or recycled filler or filler based on sustainable or renewable raw materials, e.g., silica based on rice hulls or carbon black based on vegetable oil, such as palm oil, rapeseed oil, etc. Other optional non-reinforcing fillers within the scope of the present invention include, for example, aluminosilicates, kaolin, chalk, starch, magnesium oxide, titanium dioxide, or rubber gels, as well as fibers (such as aramid fibers, glass fibers, carbon fibers, cellulose fibers).

[0052] Other potentially reinforcing fillers include, for example, carbon nanotubes (CNTs) 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 and graphene and so-called "carbon-silica dual-phase filier".

[0053] According to the invention, the rubber mixture further contains 1 to 15 phr, preferably 1 to 10 phr silanes in the form of organosilicon compounds.

[0054] 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:

[0055] 1) Anti-aging agents and ozone-protecting waxes such as diamines, like N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditolyl-p-phenylenediamine (DTPD), N-(1,4-dimethylpentyl)-N'-phenyl-p-phenylenediamine (7PPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and / or dihydroquinolines, like 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ), and / or substituted bisphenols, like 2,2'-methylenebis(4-methyl-6-tert-butylphenol) (BPH), and / or substituted phenols, like butylhydroxytoluene (BHT), 2) Activators, such as... B. Zinc oxide and fatty acids (e.g. stearic acid) and / or other activators, such as zinc complexes like zinc ethylhexanoate,

[0056] 3) further activators and / or agents for the binding of fillers, in particular carbon black or silica, such as S-(3-Aminopropyl)-thiosulfuric acid and / or their metal salts (binding to carbon black).

[0057] 4) Hydrocarbon resins, in particular phenolic resins, especially as adhesive resins,

[0058] 5) Mastication aids, such as 2,2'-dibenzamidodiphenyldisulfide (DBD) and

[0059] 6) Process aids, in particular fatty acid esters and metal soaps, such as e.g.

[0060] Zinc soaps and / or calcium soaps I) Plasticizers, such as aromatic, naphthenic or paraffinic mineral oil plasticizers, such as MES (Mild Extraction Solvate) or RAE (Residual Aromatic Extract) or TDAE (Treated Distillate Aromatic Extract), or Rubber-to-Liquid (RTL) oils or Biomass-to-Liquid (BTL) oils, preferably with a polycyclic aromatic content of less than 3 wt% according to method IP 346, or triglycerides, such as rapeseed oil, or Faktisse, or hydrocarbon resins 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.

[0061] When using mineral oil, it is preferably selected from the group consisting of DAE (Destilled Aromatic Extracts), RAE (Residual Aromatic Extract), TDAE (Treated Destillated Aromatic Extracts), MES (Mild Extracted Solvents) and naphthenic oils.

[0062] The proportion of the total amount of other additives is preferably 3 to 150 phr, particularly preferably 3 to 100 phr, and most preferably 5 to 80 phr. The rubber compound according to the invention is preferably used in vulcanized form, especially in the treads of vehicle tires.

[0063] The terms “vulcanized” and “crosslinked” are used synonymously within the scope of the present invention.

[0064] The vulcanization of the rubber compound according to the invention is preferably carried out in the presence of sulfur and / or sulfur donors using vulcanization accelerators, wherein some vulcanization accelerators can also act as sulfur donors. The accelerator is selected from the group consisting of thiazole accelerators, mercapto accelerators, sulfenamide accelerators, thiocarbamate accelerators, thiuram accelerators, thiophosphate accelerators, thiourea accelerators, xanthate accelerators, and guanidine accelerators. Preferably, at least one sulfenamide accelerator is selected from the group consisting of N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N,N-dicyclohexylbenzothiazole-2-sulfenamide (DCBS), benzothiazole-2-sulfene morpholide (MBS), N-tert-butyl-2-benzothiazole sulfenamide (TBBS), N-tert-butyl-2-benzothiazole sulfenimide (TBSI), and / or at least one guanidine accelerator, such as diphenylguanidine (DPG).

[0065] In particular, two or more accelerators can also be used.

[0066] Any sulfur-donating substance known to experts can be used as the sulfur-donating substance.

[0067] Furthermore, one or more reversion protectants, such as 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexane, hexamethylene-1,6-bis(thiosulfate) disodium salt dihydrate, and / or tetrabenzylthiuram disulfide (TBzTD), may be used in the rubber compound.

[0068] Furthermore, vulcanization retarders may be present in the rubber compound. Otherwise, the rubber compound is produced according to the standard process in the rubber industry, in which a base mixture containing all components except the vulcanization system (e.g., sulfur and vulcanization-influencing substances) is first prepared in one or more mixing stages. The finished compound is then produced by adding the vulcanization system in the mixing stages, preferably in the final stage.

[0069] The finished compound is further processed, for example by extrusion or calendering, and formed into the appropriate shape. The rubber compound according to the invention is particularly suitable for use as a tread in vehicle tires, especially pneumatic tires. Such a tread can be composed of several layers. In the case that the tread is composed of several layers, this invention relates to the radially outer region of the tread.

[0070] For use as tread in vehicle tires, the mixture is prepared as a ready-made mixture and shaped accordingly before vulcanization, and then applied and vulcanized as usual during the production of the vehicle tire blank.

[0071] As already explained at the outset, the subject matter of the present invention is in particular a vehicle tire and a tread in the vehicle tire, which comprises at least one vulcanizate made from the vulcanized rubber compound according to the invention.

[0072] Furthermore, the present invention also includes tread compounds for hot retreaded tires and for cold retreaded tires, in which PCTs (Pre-Cured-Treads, pre-vulcanized treads for cold retreading of tires) are used, comprising rubber compounds of the described formulation.

[0073] Under the vehicle tires, within the scope of the present invention

[0074] This includes pneumatic and solid rubber tires, as well as non-pneumatic tires such as spoked tires, including tires for industrial and construction vehicles, trucks, cars, and motorcycles. It is primarily intended for use in commercial vehicle tires such as trucks or buses.

[0075] A vulcanizate with the claimed rubber composition is not electrically conductive because the carbon black content is low. Therefore, to improve the electrical conductivity of the tire, one or more radially oriented rubber components are arranged in the tread, which have a specific electrical resistance of less than 1 x 10⁻⁶. 8 square meters, preferably less than 1 x 10 7 square meters, preferably less than 1 x 10 6 Qm, exhibiting and extending radially outwards to the outer surface of the tread and radially inwards to an electrically conductive inner rubber part of the vehicle tire with a specific electrical resistance of less than 1 x 10 8 square meters, preferably less than 1 x 10 7 square meters, preferably less than 1 x 10 6 square meters.

[0076] The tread is preferably constructed in two layers in the radial direction and consists of a tread cap containing the tread pattern and a radial rubber plate (tread base) extending within the tread cap. The tread base extends axially across the width of the tread cap, but can also be wider or narrower than the tread cap in the axial direction.

[0077] When using a base cap structure, an electrically conductive tread base can be employed, ensuring electrically conductive contact between the tread base and the tread surface. This contact with the tread surface can be achieved by means of one or more rubber components extending radially outwards (i.e., outwards) to the tire circumference, essentially or precisely in one direction. "Outwards" here means that contact is established with the tread surface and thus with the surface of the tire.

[0078] Within the scope of this invention, an electrically conductive or electrically conducting material is generally understood to be one which has a specific electrical resistance of less than or equal to 1 x 10 8 Qm (Ohm meter), preferably less than or equal to 1 x 10 7 Qm (Ohm Meter) particularly preferred less than or equal to 1 x 10 6Qm (Ohm Meter). Such setups to enable sufficient conductivity are state of the art and are described in various embodiments, e.g. in the publications EP 0798142 B1 or DE 102015 209 084 A1.

[0079] According to one embodiment, the tire has a tread consisting of a radially outer tread layer made of an electrically non-conductive rubber material and a radially inner tread layer made of an electrically conductive rubber material, wherein the tread preferably has shoulder-side profile ribs, each of which is penetrated in the radial direction by an electrically conductive rubber component contacting the radially inner tread layer.

[0080] Alternatively, in one embodiment, the formation of a conductive path in the tread cap can also be achieved without a tread base by establishing contact with the tread surface via one or more radially extending conductive rubber components, originating from any electrically conductive rubber component inside the tire. The rubber component could be, for example, a conductive rubber coating on a steel cord belt ply, or directly the steel cord belt ply, or a conductive rubber coating on a steel cord carcass ply, or directly the steel cord carcass ply. This is described, for example, in EP 0658452 B1.

[0081] Alternatively, the tread can also be constructed in three or four layers in the radial direction. The important aspect here is the formation of a conductive path in the tread cap, by ensuring contact via one or more radially outwardly extending electrically conductive rubber components between the tread surface and a conductive rubber layer arranged radially inward to the radially outer tread according to the invention.

[0082] Further, partly optional, features are described below in relation to the figure.

[0083] Optionally, the vehicle tires according to the present invention can have two to six belt plies, with angles for individual belt plies from 0° to 90°, including parallel (0°) and intersecting (90°) belt plies. The belt plies can, for example, have steel cord reinforcements or other non-steel cord reinforcements, such as aramid, glass fiber, carbon fiber, synthetic fibers, or cord.

[0084] Preferably, the vehicle tires have a tread pattern with a cavity volume between 5% and 35% (see also definition according to EP 2 292 448 B1 below).

[0085] Possible tread profiles include, for example, ribbed profiles, grooved profiles, lamella profiles, or block profiles. Groove or lamella geometries can be oriented laterally (90°) or circumferentially (0°), or with a constant or alternating direction between 0° and 90° relative to the circumferential direction. The directions, geometries, or widths of the lamellae can change along the tread. The profiles can, for example, have 1 to 10 circumferential grooves across the entire tread width. The profiles can, for example, have 30 to 600 transverse grooves or lamellae per circumferential rib.

[0086] Possible configurations include lateral or circumferential grooves or lamellae with rectangular grooves or grooves with a radially increasing or decreasing width. Other possibilities include constant groove widths from the groove base to the running surface or varying groove widths from bottom to top.

[0087] The invention comprises tires with different base geometries and base thicknesses or base volumes.

[0088] A commercial vehicle tire and its configurations are known, for example, from EP 3 611 036 B1.

[0089] The invention will now be explained in more detail using comparative and exemplary embodiments.

[0090] The examples according to the invention are marked with E1 and E2 and the comparative example with V1.

[0091] E1 and E2 differ only in the proportions of BR and NR, respectively. Substances used:

[0092] NR: NR TSR 20.

[0093] BR: KBR820, manufactured by KKPC (Kumho), Tg = -92 °C, functionalized,

[0094] KBR820 is a low-cis butadiene rubber (BR) produced using an alkyllithium catalyst. KBR820 has a cis content of 40.5% and a vinyl content of 12%. It is functionalized and exhibits a high affinity for silica.

[0095] Carbon black: N220, manufactured by Birla Carbon.

[0096] Silica: Premium SW, Solvay, average CTAB surface area 250 m2 / g, average BET surface area 275 m2 / g.

[0097] 1) Silane and other additives, namely zinc soap, zinc oxide, stearic acid, plasticizers, antioxidants, ozone-protective wax.

[0098] 2) DPG and vulcanizing chemicals (volcanic chemicals): Sulfenamide accelerator and sulfur.

[0099] The mass fractions in phr are given in Table 1.

[0100] Table 1: The mixture was produced according to the three-stage process common in the rubber industry.

[0101] Test specimens were produced from all mixtures by vulcanization to t95 to t100 (measured on the Moving Die Rheometer according to ASTM D 5289-12 / ISO 6502) under pressure at 140 °C and stirred for 30 minutes, and material properties typical for the rubber industry were determined using these test specimens with the test procedures specified below.

[0102] • Shore A hardness at room temperature (RT) and at 70 °C according to ISO 868,

[0103] • Rebound elasticity at room temperature (RT) and at 70 °C according to ISO 4662,

[0104] • Stress value at 300% elongation (M 300) at RT, tensile strength and elongation at break at room temperature (RT), according to DIN 53 504.

[0105] Table 2:

[0106] As can be seen in Table 2, the vulcanizate according to the invention exhibits better rebound behavior, especially at room temperature.

[0107] Test simulations were performed for tires with the compounds V1 and E1 as well as E2 as the tread, to compare the rolling resistance behavior and its change at different temperatures. Simulation results for V1, E1, and E2 are shown in Table 4.

[0108] The tire considered in these simulations has the following characteristics: The test tire is a 315 / 70 R 22.5" drive axle tire, optimized for long haul applications, with a focus on optimizing rolling resistance: The tire has a low-void profile with sipes (13.3% void volume, cf. e.g. definition of void volume in EP 2 292 448 B1) and a low tread depth (13.2 mm in the example).

[0109] As described in EP 2 292 448 B1, the treads of pneumatic tires for commercial vehicles have circumferential grooves which divide the tread into circumferential ribs, wherein an envelope running parallel to the tread periphery in the tread, which touches the deepest circumferential groove from the radial inside, together with the tread periphery and shoulder-side flank sections defines a tread gross volume and all grooves in the tread define the cavity volume.

[0110] It should be noted that in real-world tire use, the actual ambient temperatures can deviate considerably from the target temperature of 25 °C for testing rolling resistance in the so-called drum test according to ISO 28580.

[0111] Significant differences in ambient temperature have a considerable impact on the rolling resistance of the tire. Generally, a lower ambient temperature results in higher, and therefore worse, rolling resistance compared to the rolling resistance measured under ISO test conditions. Conversely, a higher ambient temperature generally results in lower, and therefore better, rolling resistance compared to the rolling resistance measured under ISO test conditions.

[0112] The rolling resistance of a tire directly affects its energy absorption or consumption, which increases at lower temperatures. This also affects, for example, the fuel consumption of combustion engine vehicles or the electricity consumption of battery-powered electric vehicles.

[0113] In battery-powered vehicles, the increase in tire-related energy consumption at low ambient temperatures, i.e., operating temperatures, therefore also has a negative impact on the maximum range with a certain, e.g., maximum, battery charge, compared to the maximum range at higher ambient temperatures.

[0114] While ISO 28580 provides an extrapolation function for ambient temperatures between 20 °C and 30 °C, this function cannot be used for very low ambient temperatures below 20 °C, especially below 0 °C.

[0115] Since rolling resistance results for low ambient temperatures (below 20 °C, especially below 0 °C) are not known or published, particularly for commercial vehicle tires such as truck / bus tires, a quantified correlation of tire rolling resistance at low ambient temperatures is not available.

[0116] For this reason, no optimization methods are known that reduce the sensitivity of tire rolling resistance to low ambient temperatures. Consequently, no measures are known that reduce the increase in tire energy consumption at low ambient temperatures (below 20°C, especially below 0°C) compared to higher ambient temperatures (20°C to 30°C). This means, for example, that for battery-powered electric vehicles, no tire-related optimization measures are known that reduce the difference between the maximum range at a given battery charge (e.g., maximum) at low ambient temperatures and the maximum range at a given battery charge (e.g., maximum) at higher ambient temperatures. Therefore, to quantify the change in rolling resistance behavior at low temperatures, a simulation methodology was developed in two steps within the scope of the present invention.In the first step, the tire rolling resistance was measured in a drum test at various ambient temperatures. Apart from the ambient temperatures, the test conditions were the same as for the test according to ISO 28580. In particular, the warm-up time for the drum tests also complied with the ISO standard.

[0117] The second step was a simulation of the tire rolling resistance using the same parameters as in the drum tests.

[0118] To validate the simulation methodology, three different tire variants, described below, were tested in drum tests at different temperatures, and the same tests were replicated by simulations. The results for rolling resistance in the tests and in the simulations are shown in Table 3.

[0119] Tire option 1:

[0120] A drive axle tire with dimensions 315 / 70 R 22.5", optimized for long-haul transport ("long haul"), with a focus on optimizing rolling resistance: The tire has a low void volume with sipes (13.3% void volume, void volume determined according to EP 2 292 448) and a shallow tread depth (13.2 mm). The tread and carcass of the tire comprise vulcanized rubber compounds optimized for low rolling resistance under ISO drum test conditions. The tire contour is also optimized with respect to rolling resistance. Tire variant 1 was also used as the basis for the simulations carried out in relation to the present invention.

[0121] Tire variant 2:

[0122] A drive axle tire with dimensions 315 / 70 R 22.5", optimized for regional use, with a focus on optimizing mileage and traction: The tire has a high cavity profile with blocky elements (16.2% cavity volume, cavity volume determined according to EP 2 292 448) and a high tread depth (18.7 mm). The tire's tread compound is vulcanized and optimized for high mileage and traction. The tire carcass is also vulcanized and optimized for consistently high mileage.

[0123] Tire variant 3: Essentially the same tire as in tire variant 2, but with a tread depth ground down to 4 mm. This grinding process is carried out with considerable effort to achieve a very smooth tire surface, closely resembling the surface quality of a tire at the end of its service life.

[0124] The three tire variants described cover a wide range of tire design limits:

[0125] - wide range of tire rolling resistances,

[0126] - wide range of profile depths,

[0127] - Tread depths of new tires and tires that are almost completely worn out

[0128] - wide range of tread characteristics.

[0129] The rolling resistance of the three described tire variants was tested and simulated at the following three different ambient temperatures: +25 °C (reference temperature according to ISO 28580),

[0130] +9 °C (temperature close to the annual average temperature for Central European countries), -10 °C

[0131] The rolling resistance simulations in the second step were performed for exactly the same tire variants and for the temperatures used in the tire tests:

[0132] The rolling resistance simulations were performed using a specially developed and optimized rolling resistance simulation program.

[0133] The same boundary conditions were used for the rolling resistance simulation as for the tire test (e.g., drum diameter, speed, air pressure, tire load, rim size). Table 3 shows the rolling resistance results of the previously described drum tests and simulations in % relative to the reference value at 25 °C (100%).

[0134] Table 3:

[0135] Table 3 shows that the simulation results and the test results are very similar.

[0136] Table 3 also shows that the rolling resistance for all tested tire types increases significantly with decreasing temperature.

[0137] In the following, simulations were carried out for tires with the mixtures according to V1 and E1 as well as E2 as the tread mixture, which otherwise correspond to the tires of the tire variant 1 described above, in order to compare the rolling resistance behavior and its change at different temperatures.

[0138] The simulation results for rolling resistance at room temperature (RT) and at -10 °C are given in Table 4 as absolute values ​​in kg / t. The difference in rolling resistance at different temperatures for the same tread compound is also given.

[0139] Tires according to the invention with treads containing or formed from the vulcanizate according to the invention surprisingly exhibit significantly improved rolling resistance behavior at low temperatures (simulation values ​​at -10 °C are shown here) compared to V1. Table 4:

[0140] As can be seen in Table 4, the tires with the tread compounds according to the invention exhibit a lower increase in rolling resistance at an ambient temperature of -10°C compared to the rolling resistance results at an ambient temperature of 25°C. This reduction in the ambient temperature-related increase in rolling resistance from 1.7 kg / t for the reference tread compound (V1) to 1.5 or 1.4 kg / t for the optimized tread compounds (E1, E2) is significant.

[0141] The temperature sensitivity of the rolling resistance behavior is therefore advantageously reduced.

[0142] According to the invention, this is achieved in particular by using a rubber compound with an increased proportion of a BR according to the invention with low Tg.

[0143] This improves the properties of the tire or tread through the rubber compound according to the invention.

[0144] Figure 1 further shows an exemplary embodiment of the tread 1 comprising a vulcanizate of the rubber compound according to the invention with center beam.

[0145] Figure 1 shows, in particular, the usual components of a radial commercial vehicle tire, a tread 1, a belt reinforcement 2 radially within the tread 1, a radial carcass 3 reinforced with a strengthening agent, and an airtight inner layer 4. The tread 1 has a two-layer radial structure and consists of a tread cap 5 containing the tread pattern and the vulcanizate according to the invention, and a tread base 6 extending radially within the tread cap 5. In this figure, the tread base 6 extends axially across the width of the tread cap 5.

[0146] In the illustrated embodiment, the tread 1 has circumferential grooves 7 extending within the tread cap 5, which have the tread depth typical for commercial vehicle tires. The circumferential grooves 7 divide the tread 1 into circumferential profile ribs 8, which can be structured in a block-like manner or consist of profile blocks.

[0147] The tread cap 5 is made from the electrically non-conductive rubber compound according to the invention and accordingly consists of an electrically non-conductive rubber material, wherein, within the scope of the present invention, an electrically non-conductive rubber material is to be understood as one which has a specific electrical resistance of more than 1 ■ 10 8 It has square meters.

[0148] This specific electrical resistance is determined according to DIN IEC 60093:19993-12. Alternatively, the specific electrical resistance (specific volume resistance) can also be determined using the following method:

[0149] The specific electrical resistance is calculated from a previously measured electrical resistance (measured through-resistance: resistance of a material to the flow of current).

[0150] The electrical resistance (R [Q]) is measured using a DC current meter with two metal electrodes (e.g., Fluke 1507 insulation tester with a test range of 1 10 4 up to 1 ■ 10 10 Ohm) and a defined vulcanized test specimen.

[0151] The test specimen has, for example, the following geometry:

[0152] • Circular cylindrical test specimen (test specimen in the form of a straight circular cylinder),

[0153] • Diameter: 44.6 mm, • Height: 6.3 mm.

[0154] The test specimen is produced (vulcanized) under the following vulcanization parameters, for example:

[0155] • Vulcanization temperature: 140°C,

[0156] • Vulcanization time: 30 minutes.

[0157] To measure the electrical resistance (R [Q]), the test specimen is held flat between two metal electrodes (circular cylindrical metal electrodes with a diameter of 44.6 mm), which are pressed against each other with a force of 10 N to hold the test specimen. The circular cylindrical metal electrodes are therefore pressed against the circular surfaces of the test specimen.

[0158] After measuring the electrical resistance (R [Q]), the specific electrical resistance RSpec. [Qm] is calculated according to the following equation: RSpec. [Qm] = R [Q] ■ (S [m2] / T [m]) Where:

[0159] RSpec. [Qm] = Specific electrical resistance in ohms per meter (Qm), R [Q] = Measured electrical resistance in ohms per meter,

[0160] S [m2] = measuring area of ​​the test specimen (= size of one of the circular areas) in the unit square meter,

[0161] T [m] = thickness of the test specimen in meters.

[0162] Base 6 can be made from a rubber compound containing only carbon black as a filler, giving the base rubber high electrical conductivity. The conductive compound of the base and carbon center beam is intended to have a specific electrical resistance of less than 1 x 10⁻⁶. A exhibit a specific electrical resistance of 7 µm. This specific electrical resistance is determined according to DIN IEC 60093:19993-12 or the test procedure described above.

[0163] The tread cap 5 is divided axially in the direction by a narrow rubber component 9, the so-called carbon center beam, which extends radially and circumferentially. The rubber component 9 runs from the base 6 to the tread surface and is made of an electrically conductive rubber compound, preferably the same rubber compound as the base 6.

[0164] The Carbon Center-Beam therefore forms an electrically conductive passage between the tread surface and the Base 6. Typically, the Carbon Center-Beam 9 and the Base 6 are manufactured as a single component during tread extrusion, i.e., extruded as one continuous part.

[0165] Reference symbol list

[0166] 1 tread

[0167] 2 belts 3 radial carcass

[0168] 4 inner layer

[0169] 5 tread strip cap

[0170] 6 tread base

[0171] 7 Circumferential groove 8 Profile rib

[0172] 9 radial rubber component

Claims

Patent claims 1. A vehicle tire comprising at least in one tread (1) a vulcanizate obtained by sulfur vulcanization of a rubber compound containing at least the following components: a) 25 to 100 phr of at least one butadiene rubber, wherein the butadiene rubber has a glass transition temperature Tg below -75 °C, preferably below -85 °C; b) 20 to 70 phr, preferably 40 to 60 phr of at least one silica as a filler; c) carbon black as a filler with a proportion of at most 18 phr, preferably 1 phr to at most 10 phr, wherein one or more radially extending rubber components (9) are arranged in the tread (1), which have a specific electrical resistance of less than 1 x 10 8Qm and which extend radially outwards to the outer surface of the tread (1) and radially inwards to an electrically conductive inner rubber part of the vehicle tire with a specific electrical resistance of less than 1 x 10 8 extend to square meters.

2. Vehicle tires according to claim 1, wherein the proportion of butadiene rubber in the rubber compound is at least 30 phr, preferably at least 40 phr, more preferably more than 50 phr.

3. Vehicle tire according to claim 1 or 2 comprising the following further component in the rubber compound: d) a maximum of 75 phr, preferably 10 phr to a maximum of 70 phr, more preferably 10 phr to a maximum of 60 phr of at least one polyisoprene, preferably one natural polyisoprene.

4. Vehicle tire according to claim 3 comprising the following further component in the rubber compound: e) a styrene-butadiene rubber.

5. Vehicle tires according to any one of claims 1 to 4, wherein the rubber compound does not contain any further rubber components.

6. Vehicle tires according to any one of claims 1 to 5, wherein the silica in the rubber compound has a CTAB surface area according to ASTM D 3765 of over 200 m2 / g, preferably 250 to 400 m2 / g.

7. Vehicle tire according to any one of claims 1 to 6 comprising the following further component in the rubber compound: f) 1 to 15 phr of silanes.

8. Vehicle tires according to any one of claims 1 to 7, wherein the raw materials used in the rubber compound are partially or completely based on recycled, renewable and / or bio-based raw materials, wherein preferably all rubber materials used in the rubber compound are based on recycled, renewable and / or bio-based raw materials, in particular on recycled natural rubber and / or on IR recycled rubber and / or on BR recycled rubber.

9. Vehicle tires according to any one of claims 1 to 8, wherein the butadiene rubber used in the rubber compound is partially or completely based on recycled, renewable and / or bio-based raw materials, preferably based on one or more of wood, beets, potatoes, fruits or by-products of biodiesel production such as glycerin.

10. Vehicle tire according to any one of claims 1 to 9, wherein the filler(s) used in the rubber compound consists partly or entirely of recycled, renewable and / or bio-based material, wherein silica based on rice hulls and / or carbon black based on vegetable oil are preferred as filler.

11. Vehicle tire according to one of claims 1 to 10, wherein it is a new tire, a hot-retreaded tire or a cold-retreaded tire which is a pneumatic tire, a solid rubber tire, or a non-pneumatic tire with a spoked construction.

12. A vehicle tire according to any one of claims 1 to 11, wherein the electrically conductive inner rubber part of the vehicle tire is a tread base (6) or an additional rubber component of the tread (1), or a steel cord belt ply or its rubber linings, or a steel cord carcass ply or its rubber linings.

13. A vehicle tire according to any one of claims 1 to 12, which is a commercial vehicle tire.

14. Pre-vulcanized tread for the cold retreading of vehicle tires, comprising at least one rubber compound according to any one of claims 1 to 10.

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