Vehicle tyre

Abstract

The invention relates to a vehicle tyre having a tread (1) with a tread outer surface (1a), wherein the vehicle tyre has at least one discharge path for discharging electrostatic charges to the tread outer surface, wherein the tread (1) has a radially outer tread layer (11) which is made of an electrically non-conductive rubber material and partially forms the tread outer surface (1a) and at least one tread layer (12) which is made of an electrically conductive rubber material, belongs to the discharge path and is spaced apart from the tread outer surface (1a). The electrically conductive rubber material of the tread layer (12) spaced apart from the tread outer surface (1a) has: a. a rebound resilience at 70°C, determined in accordance with ISO 4662, of at least 68.0%; b. a Shore hardness A at 70°C, determined in accordance with DIN EN ISO 868, of at least 58.0 ShA; c. an elongation at break at 100°C, determined in accordance with DIN 53504, of at least 450%; and d. a specific electrical resistance of at most 1.0 x 106 Ω∙m.

Description

[0001] Description

[0002] Vehicle tires

[0003] The invention relates to a vehicle tire with a tread having an outer tread surface located in the tread periphery, wherein the vehicle tire has at least one discharge path for discharging electrostatic charges to the outer tread surface, wherein the tread has a radially outer tread layer made of an electrically non-conductive rubber material that forms the outer tread surface, and at least one tread layer made of an electrically conductive rubber material that belongs to the discharge path and is spaced from the outer tread surface.

[0004] Such a vehicle tire is known, for example, from DE 102015209 084 A1. 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. The tread has shoulder-side tread ribs, each of which is radially penetrated by an electrically conductive rubber component that contacts the radially inner tread layer.

[0005] Furthermore, DE 10 2016 216 072 A1 discloses a commercial vehicle tire with a tread consisting, in the radial direction, of a radially outer tread layer, a middle tread layer, and a radially inner tread layer. The tread pattern is located in the radially outer and middle tread layers. The radially outer tread layer has an elongation at break of 600% to 900% according to DIN 53504, thus achieving good chip and chunk resistance.The middle tread layer has a Shore A hardness according to DIN ISO 7619-1 (now replaced by DIN EN ISO 868) of 50 ShA to 80 ShA, in particular from 65 ShA to 75 ShA, for example 60.1 ShA, furthermore a rebound resilience according to DIN 53512 (Note: DIN 53512 describes a test method identical to ISO 4662, but only allows vertical oscillators and indenters mounted on rigid pendulum rods) at 70°C of 45% to 75%, in particular from 55% to 65%, for example 54%, furthermore an elongation at break according to DIN 53504 of 450% to 700%, in particular from 530% to 600%, for example 565%, as well as a stress value at 300% elongation according to DIN 53504 from 8.0 MPa to 12.0 MPa, for example from 10.0 MPa.

[0006] Due to increasing technical and regulatory requirements, it is becoming increasingly complex to design tread layers in vehicle tires of the type mentioned above with regard to several vulcanizate properties that are important for tire performance. As a result, conflicts between these vulcanizate properties are becoming increasingly difficult to resolve.

[0007] For the radially outer tread layer, which comes into contact with the road surface when the tire rolls, the rubber materials used primarily focus on vulcanized properties, which ensure the tire's handling performance—in particular, grip and response to steering forces—as well as the highest possible abrasion resistance of the tread. Such radially outer tread layers are often not (sufficiently) electrically conductive, so electrically conductive elements, such as a so-called carbon center beam, are incorporated (integrated) into these tread layers.

[0008] Regarding the radially inner tread layer(s), i.e., those layers that do not come into contact with the ground during tire rolling, their rubber materials have so far been optimized primarily with regard to those vulcanizate properties that contribute to rolling resistance and their impact on handling performance. The vulcanizate properties that ensure high abrasion resistance in the rubber material of the radially outer tread layer are not the focus and therefore do not need to be considered, or only rarely.

[0009] In the case of vehicle tires of the type mentioned above, i.e. tires in which a tread layer made of an electrically conductive rubber material, spaced from the tread periphery, forms the discharge path, it has not yet been possible, or not optimally possible, to adequately or optimally balance this tread layer with regard to handling performance, its contribution to rolling resistance and its durability against mechanical stress, i.e. in particular its crack resistance, while at the same time maintaining its electrical conductivity.

[0010] The invention is therefore based on the object of resolving the conflict of objectives between the handling performance of the tire, the rolling resistance of the tire and the tread durability in a vehicle tire of the type mentioned at the outset - with regard to the mentioned tread layer - in a more favorable manner than before, while additionally maintaining the discharge path.

[0011] The stated object is achieved according to the invention in that the electrically conductive rubber material of the tread layer spaced from the tread outer surface has a) a rebound resilience at 70°C, determined according to ISO 4662, of at least 68.0%, b) a Shore A hardness at 70°C, determined according to DIN EN ISO 868, of at least 58.0 ShA, c) an elongation at break at 100°C, determined according to DIN 53504, of at least 450% and d) a specific electrical resistance of maximum 1.0 x 10 6 Q m.

[0012] The rebound resilience at 70°C is a primary rolling resistance indicator, with a rebound resilience of at least 68.0% minimizing the tread layer's contribution to rolling resistance. The Shore A hardness at 70°C is a primary handling performance indicator and is related to the "stiffness" of the tread layer, with a Shore A hardness at 70°C of at least 58.0 ShA ensuring good handling performance. The elongation at break at 100°C is a primary crack resistance indicator. An elongation at break at 100°C of at least 450% ensures good crack resistance, thus ensuring long durability of the tread layer and thus improving the overall durability of the tread. The specific electrical resistance is a conductivity indicator, with a specific electrical resistance of a maximum of 1.0 x 10 6Q m ensures the maintenance of a perfectly functioning dissipation path through the tread layer spaced from the tread periphery. Thus, in the tread layer spaced from the outer surface of the tread, several vulcanizate properties are harmonized in a particularly advantageous manner.

[0013] According to a preferred embodiment, the tread consists, in the radial direction, of a tread cap containing the complete tread pattern and a tread base. The tread base is the tread layer made of electrically conductive rubber material spaced apart from the tread outer surface. A tread with a correspondingly designed tread base is particularly advantageous for resolving the aforementioned conflict of objectives.

[0014] With regard to the rolling resistance of the tyre, it is particularly advantageous if the rebound resilience at 70°C, determined according to ISO 4662, of the electrically conductive rubber material of the tread layer spaced from the tread outer surface is at least 70.0%.

[0015] For handling performance, it is particularly advantageous if the Shore A hardness at 70°C, determined according to DIN EN ISO 868, of the electrically conductive rubber material of the tread layer spaced from the outer tread surface is at least 60.0 ShA. The durability of the tread is further improved if the elongation at break at 100°C, determined according to DIN 53504, of the electrically conductive rubber material of the tread layer spaced from the outer tread surface is at least 470%, preferably at least 490%.

[0016] The electrical conductivity of the vehicle tyre is further improved if the specific electrical resistance of the electrically conductive rubber material of the tread layer spaced from the outer surface of the tread is a maximum of 5.0 x 10 5 Q m, preferably maximum 1 ,0 x 10 5 Q m, particularly preferably 5.0 x 10 4 Q m, most preferably 1 ,0 x 10 4 Q m.

[0017] According to a further preferred embodiment, the electrically conductive rubber material of the tread layer spaced from the tread outer surface has a loss factor tan d at a temperature of 70°C, determined according to ISO 4664-1, of a maximum of 0.100, in particular a maximum of 0.090. This loss factor represents a secondary (supplementary) rolling resistance indicator. The use of such a rubber material is of additional advantage with regard to low rolling resistance.

[0018] According to a further preferred embodiment, the electrically conductive rubber material of the tread layer spaced from the tread outer surface has a stress value at an elongation of 200% and a temperature of 70°C, determined according to DIN 53504, of at least 6.5 MPa, in particular of at least 7.0 MPa, and preferably of at least 7.5 MPa. This stress value represents a secondary (supplementary) handling performance indicator. The use of such a rubber material is additionally advantageous with regard to handling performance.

[0019] It is also advantageous if the electrically conductive rubber material of the tread layer spaced from the outer surface of the tread has a tensile strength at a temperature of 100°C, determined according to DIN 53504, of at least 16.0 MPa, in particular of at least 17.0 MPa, preferably of at least 18.0 MPa. Tensile strength represents a secondary indicator of crack resistance. The aforementioned rubber material ensures further improved crack resistance and thus a particularly long tread life.

[0020] According to a further preferred embodiment, the electrically conductive rubber material of the tread layer spaced from the tread outer surface is made of a rubber mixture containing one or more carbon blacks having the following properties:

[0021] - Oil absorption number according to ASTM D 3493:2021 from 150 ml / 100 g to 190 ml / 100 g, in particular from 166 ml / 100 g to 180 ml / 100 g,

[0022] - Iodine adsorption number according to NF T45-111 ; NF ISO 1304 of 78 mg / g to 95 mg / g, in particular up to 88 mg / g,

[0023] - Nitrogen adsorption number according to ASTM D 6556-21 of 73 m 2 / g up to 83 m 2 / G,

[0024] - Color intensity according to ISO 5435 of 90% to 110%, especially up to 102%. Such carbon blacks contribute particularly reliably to achieving the desired vulcanizate properties.

[0025] In the latter embodiment, according to an advantageous further development, the rubber compound of the electrically conductive rubber material of the tread layer spaced from the outer surface of the tread contains no additional carbon black. This also contributes to achieving the desired vulcanizate properties.

[0026] According to a second advantageous further development of the last-mentioned embodiment, carbon black(s) is / are contained in the rubber mixture of the electrically conductive rubber material of the tread layer spaced from the tread outer surface in a total amount of 40.0 phr to 50.0 phr, in particular up to 45.0 phr.

[0027] The tread layer spaced from the outer surface of the tread preferably extends, viewed in cross-section, axially over at least 50% of the width of the tread's ground contact patch. This contributes to a tire that is particularly well balanced with regard to the aforementioned conflict of objectives.

[0028] The vehicle tire is preferably a passenger car, van, SUV or commercial vehicle tire.

[0029] Further features, advantages and details of the invention will now be explained in more detail with reference to the single figure, Fig. 1, which schematically shows a partial cross-section through a commercial vehicle tire with an embodiment of the invention.

[0030] Vehicle tires designed according to the invention are tires for motor vehicles, in particular for multi-track motor vehicles, preferably for passenger cars (PCs), vans (transporters), SLIVs or commercial vehicles and preferably pneumatic vehicle tires, particularly preferably pneumatic vehicle tires of radial design for rims with a rim diameter of 13 inches to 24 inches.

[0031] Fig. 1 shows a partial cross-section of a commercial vehicle tire. The radial direction is indicated by a double arrow R, the axial direction by a double arrow A, and the tire equatorial plane by a line AA. The "axial direction" refers to the direction perpendicular to the tire equatorial plane. The "radial direction" refers to the direction parallel to the tire equatorial plane in the axially oriented cross-section.

[0032] The commercial vehicle tire has a profiled tread 1, a four-ply belt structure 2, sidewalls 3, a carcass ply 4, and an inner layer 5. The bead regions (not shown) can be designed in a manner known per se. In each shoulder region, a shoulder padding designed in a particularly known manner, which comprises, for example, one or more shoulder and / or belt edge pads, is preferably provided. All of the components mentioned are components running circumferentially. The electrostatic charges occurring during driving are conducted from the vehicle, in particular from the body, to the respective ground ("grounding") via a discharge path, which leads from the rim, at least one electrically conductive sidewall flange profile passage, if applicable.an electrically conductive belt passage formed in the region of the belt assembly 2 and at least one electrically conductive tread layer spaced from the tread periphery and one or more electrically conductive elements located in the tread, as will be explained in more detail below.

[0033] The belt assembly 2, the sidewalls 3, the carcass ply 4, and the inner layer 5 can be constructed in a manner known per se. The electrically conductive sidewall-Zhorn profile passage is formed, for example, by a sidewall 3 and a horn profile, each made of electrically conductive rubber material, or by electrically conductive threads in the region of the horn profile, on the inside of the sidewall 3 andZor the outside of the carcass ply 4. The electrically conductive belt passage is formed, for example, by an electrically conductive belt rubber coating or electrically conductive threads on the belt layers.

[0034] The tread 1 has an outer tread surface 1a located in the tread periphery and a ground contact patch with a width B determined in the axial direction, wherein the ground contact patch corresponds, as is known, to the statically determined footprint (determined with a tire mounted on a standard rim, loaded at 70% of the maximum load capacity, internal pressure 85% of the standard pressure, according to ETRTO standards). The tread 1 is composed in the radial direction of two tread layers, namely a tread cap 1i containing the tread pattern and forming the outer tread surface 1a, and a tread base 12. In the exemplary embodiment, the tread 1 is profiled by four circumferential grooves 7. The tread cap 1i and the tread base 12 are each made of a rubber material.At least one electrically conductive element e is integrated into the tread cap 11 in the area of ​​the ground contact patch, in the exemplary embodiment in the area of ​​the tire equatorial plane (line AA), which penetrates the tread cap 1i in the radial direction and extends to the tread outer surface 1a. In particular, a single electrically conductive element 6 is provided in the form of a so-called carbon center beam, which is an electrically conductive rubber strip running circumferentially. If there are several electrically conductive elements 6, these are preferably distributed over the tire circumference in such a way that when the tire rolls, at least one of the elements 6 is located in the area of ​​the footprint. The rubber material of the tread cap 1i is electrically non-conductive and can be designed in a known manner.

[0035] The tread base 12 extends, viewed in the axially oriented cross-section, over the entire axial width of the tread cap 1 i. The design of the rubber material of the tread base 12 is discussed in more detail below.

[0036] The rubber material of the tread base I2 is optimized with regard to its contribution to rolling resistance, its impact on handling performance (stable driving behavior, for example, response to steering forces), and its crack resistance, and is also electrically conductive. In the example shown, the tread base I2 is thus the aforementioned "at least one electrically conductive tread layer spaced from the tread periphery."

[0037] Table 1 shows exemplary recipes, i.e. compositions, of rubber compounds for the rubber material of the tread base I2. Table 1 lists known comparative compounds V1, V2, and a rubber compound E1 prepared according to an exemplary embodiment of the invention. As is common in rubber technology, the recipes are based on 100 parts of rubber (phr = parts per hundred parts rubber). The quantities therefore refer to 100 parts by mass of the base polymer (rubber) or, in the case of polymer blends, which are not provided for in the exemplary recipes, to those of the base polymers (rubbers).

[0038] Table 1 : Recipes

[0039] Antioxidants include, in particular, DTPD, 6PPD, TMQ, and UV stabilizers. Vulcanization chemicals include, in particular, zinc oxide, stearic acid, accelerators such as CBS and / or TBBS, and sulfur.

[0040] Table 2 shows some typical parameters for characterizing the types A, B, C of carbon blacks given in Table 1.

[0041] Table 2: Characterization of soot types

[0042] Rubber compounds intended for the tread base 12 contain at least one carbon black with the following properties:

[0043] Oil absorption number according to ASTM D 3493:2021 = 150 ml / 100 g to 190 ml / 100 g, in particular 166 ml / 100 g to 180 ml / 100 g;

[0044] Iodine adsorption number according to NF T45-111; NF ISO 1304 = 78 mg / g to 95 mg / g, in particular up to 88 mg / g;

[0045] Nitrogen adsorption number according to ASTM D 6556-21 = 73 m 2 / g up to 83 m 2 / G;

[0046] Colour intensity according to ISO 5435 = 90% to 110%, especially up to 102%

[0047] The rubber compound intended for tread base 12 contains carbon black(s) of the above type in a total amount of 40.0 phr to 50.0 phr, in particular up to 45.0 phr. As already mentioned, the rubber material of tread base I2 is optimized with regard to its contribution to rolling resistance, its impact on handling performance, and its crack resistance, with the rubber material additionally being made electrically conductive. The following describes the vulcanizate properties of the rubber material of tread base I2, which are indicators for rolling resistance,

[0048] Handling performance, crack resistance and electrical conductivity.

[0049] Rolling resistance indicators (rolling resistance indicators)

[0050] The primary rolling resistance indicator is the rebound resilience at 70°C according to ISO 4662 (2017-06 edition). Greater rebound resilience at a temperature of 70°C is associated with lower (better) rolling resistance.

[0051] The rebound resilience at a temperature of 70°C was determined as follows: Determination according to ISO 4662:

[0052] - Elastomers or thermoplastic elastomers - Determination of the rebound resilience of vulcanizates

[0053] - Issue 2017-06

[0054] - Thickness of the test specimens: 6.3 mm ± 0.3 mm

[0055] - Vulcanization parameters (production of test specimens): o Vulcanization temperature: 140°C o Vulcanization time: 30 minutes

[0056] - Measurement parameters: o Tempering time: 30 minutes o Temperature: 70°C ± 1 °C

[0057] The loss factor tan d at 70°C according to ISO 4664-1 (edition 2022-07) is used as a secondary (supplementary) rolling resistance indicator. A lower loss factor tan d at 70°C indicates lower (better) rolling resistance.

[0058] The loss factor tan d at 70°C was determined as follows:

[0059] Determination according to ISO 4664-1:

[0060] - Elastomers or thermoplastic elastomers - Determination of dynamic properties - Part 1: Principles

[0061] - Issue 2022-07

[0062] - Vulcanization parameters (production of test specimens): o Vulcanization temperature: 140°C o Vulcanization time: 30 minutes

[0063] - Measurement parameters: o Measurement frequency: 10 Hz o Pre-force: 50 N o Amplitude force: 30 N o Tempering time: 5 minutes o Temperature: 70°C ± 1 °C o Measurement recording: After 30 seconds of test time

[0064] Handling performance indicators (Handling performance indicators) The handling performance indicators provide information about the stiffness of the rubber material. The primary handling performance indicator is the Shore A hardness at 70°C according to DIN EN ISO 868 (2003-10 edition). A higher Shore A hardness indicates better handling performance.

[0065] The Shore A hardness was determined as follows:

[0066] Determination according to DIN EN ISO 868:

[0067] - Plastics and hard rubber - Determination of indentation hardness using a durometer (Shore hardness) (ISO 868:2003); German version EN ISO 868:2003

[0068] - Edition 2003-10

[0069] - Vulcanization parameters (production of test specimens): o Vulcanization temperature: 140°C o Vulcanization time: 30 minutes

[0070] - Measurement parameters: o Tempering time: 30 minutes o Temperature: 70°C ± 2°C o Measurement time (holding time): 15 seconds

[0071] The secondary handling performance indicator is the stress value at 200% elongation and 70°C according to DIN 53504 (2017-03 edition). The determination of this value is explained below in the crack resistance indicators. A higher stress value at 200% elongation indicates better handling performance.

[0072] The secondary handling performance indicator (stress value at 200% elongation) was determined at a temperature of 70°C, as this temperature is within the range of typical tire temperatures encountered during driving.

[0073] Crack resistance indicators (crack resistance indicators)

[0074] The primary indicator of crack resistance is the elongation at break at 100°C according to DIN 53504 (2017-03 edition). A higher elongation at break indicates better crack resistance.

[0075] Tensile strength at 100°C according to DIN 53504 (2017-03 edition) is used as a secondary indicator of crack resistance. Higher tensile strength is expected to result in better crack resistance.

[0076] The two crack resistance indicators (elongation at break and tensile strength) were

[0077] - in contrast to the secondary handling performance indicator (stress value at 200% elongation) - determined at a temperature of 100°C, since this temperature is close to the usual failure temperature (in a high-speed test or durability test).

[0078] The stress value at 200% elongation and 70°C, the elongation at break at 100°C and the tensile strength at 100°C were determined as follows:

[0079] Determination according to DIN 53504:

[0080] - Testing of rubber and elastomers - Determination of tear strength, tensile strength, elongation at break and stress values ​​in tensile tests

[0081] - Issue 2017-03

[0082] - Vulcanization parameters (production of test specimens): o Vulcanization temperature: 140°C o Vulcanization time: 30 minutes

[0083] - Measurement parameters: o Temperature: 70°C ± 2°C (stress value at 200% elongation) o Temperature: 100°C ± 2°C (elongation at break, tensile strength)

[0084] Electrical conductivity indicator (conductivity indicator)

[0085] The conductivity indicator is the specific electrical resistance (specific volume resistance), which was calculated from a previously measured electrical resistance (measured volume resistance: resistance of a material to the flow of current).

[0086] The electrical resistance (R [Q]) was measured using a DC current meter with two metal electrodes (Fluke 1507 insulation tester with a test range of 1 ■ 10 4 to 1 ■ 10 10Ohm) and a defined vulcanized test specimen as well as in an air-conditioned test laboratory (23°C).

[0087] The test specimen had the following geometry:

[0088] - Circular cylindrical test specimen (test specimen in the shape of a right circular cylinder)

[0089] - Diameter: 44.6 mm

[0090] - Thickness (height, strength): 6.3 mm

[0091] The test specimen was manufactured (vulcanized) under the following vulcanization parameters:

[0092] - Vulcanization temperature: 140°C

[0093] - Vulcanization time: 30 minutes

[0094] To measure the electrical resistance (R [Q]), the test specimen was placed flat between two metal electrodes (circular cylindrical metal electrodes with a diameter of 44.6 mm), which were loaded 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 circular cylindrical test specimen. After measuring the electrical resistance (R [Q]), the specific electrical resistance was calculated using the following equation: spec. [Q m] = R [Q] ■ (S [m 2 ] / T [m]) Rspec. [Q m] Specific electrical resistance in the unit Ohm x meter R [Q] Measured electrical resistance in the unit Ohm

[0095] S [m 2 ] Measuring area of ​​the test specimen (= size of a (single) circular area) in the unit square meter

[0096] T [m] Thickness of the test specimen in meters

[0097] Table 3 shows the values ​​for the rolling resistance indicators, the handling performance indicators, the crack resistance indicators and the conductivity indicator of the rubber materials made from the rubber compounds V1, V2, E1 specified in Table 1.

[0098] Table 3: Vulcanizate properties / indicators

[0099] Vulcanizate

[0100] Unit E1 property

[0101] Rolling resistance indicators

[0102] Primary rolling resistance indicator

[0103] Rebound resilience

[0104] ISO 4662 69.6 74.6 70.1

[0105] (70°C)

[0106] Secondary rolling resistance indicator

[0107] Loss factor tan d

[0108] 0.087 0.052 0.082 (70°C)

[0109] Handling performance indicators

[0110] Primary handling performance indicator

[0111] DIN EN ShA

[0112] Shore A hardness (70°C) 59.7 56.2 62.1

[0113] ISO 868 (Shore A) Secondary handling performance-! indicator

[0114] Stress value MPa

[0115] DIN 53 504 6.3 4.9 8.0

[0116] (200% elongation, 70°C) (Megapascal)

[0117] Crack resistance indicators

[0118] Primary crack resistance! <eitsi ndikator Reißdehnung

[0119] DIN 53 504 496 467 498

[0120] (100°C)

[0121] Secondary crack resistance indicator

[0122] MPa

[0123] Tensile strength (100°C) DIN 53 504 16 13.5 18.2 (megapascals)

[0124] Conductivity indicator Larger than

[0125] Specific Q m

[0126] None, above electrical (Ohm x 2.7E+09 2.7E+09 4.9E+03

[0127] Test procedures

[0128] resistance meter)

[0129] The rubber material of the tread base 12 has for the above

[0130] Vulcanizate properties generally have the following values:

[0131] - Rebound resilience (70°C) = at least 68.0%, in particular at least 70%,

[0132] - Loss factor tan d (70°C) = maximum 0.100, in particular maximum 0.090

[0133] - Shore hardness A (70°C) = at least 58.0 ShA, in particular at least 60.0 ShA - Tensile strength (200% elongation, 70°C) = at least 6.5 MPa, in particular at least 7.0 MPa, preferably at least 7.5 MPa

[0134] - Elongation at break (100°C) = at least 450%, in particular at least 470%, preferably at least 490%

[0135] - Tensile strength (100°C) = at least 16.0 MPa, in particular at least 17.0 MPa, preferably at least 18.0 MPa

[0136] - Specific electrical resistance = maximum 1.0 x 106 Q m, in particular a maximum of 5.0 x 10 5 Q m, preferably maximum 1 ,0 x 10 5 Q m, particularly preferably 5.0 x 10 4 Q m, most preferably 1 ,0 x 10 4 Q m

[0137] As can be seen from Table 3, the rubber material of the rubber compound E1 is characterized by the fact that it is additionally electrically conductive - in accordance with its specific electrical resistance - while maintaining high values ​​for the primary rolling resistance indicator (rebound resilience (70°C)), the primary handling performance indicator (Shore hardness A (70°C)) and the primary crack resistance indicator (elongation at break (100°C)).

[0138] Tire tests

[0139] Commercial vehicle tires in size 315 / 70 R22.5 (tire designation Conti EfficientPro D) were manufactured with a two-layer tread 1, with the tread cap 1i made of matching rubber compounds and the tread base 12 made of rubber compounds V1 and E1, respectively. The rolling resistance and electrical leakage resistance of the commercial vehicle tires were tested. The test conditions are given below.

[0140] Rolling resistance test:

[0141] - Standard: ISO 28580

[0142] - Car, truck and bus tyre rolling resistance measurement method - Single-point test and correlation of measurement results

[0143] - Issue 2018-07

[0144] Test for electrical leakage resistance:

[0145] - wdk 110 Sheet 1 :2022-03

[0146] - Measurement method for determining the electrical leakage resistance of pneumatic tires on the test bench - Edition 2022-03

[0147] According to Table 4, both the commercial vehicle tire with a tread base made of rubber compound V1 and the commercial vehicle tire with a tread base made of rubber compound E1 exhibit good (low) rolling resistance values. However, the electrical resistance of commercial vehicle tires with a tread base made of rubber compound E1 is so significantly lower that, in a commercial vehicle tire with a tread base made of rubber compound E1—in contrast to a commercial vehicle tire with a tread base made of rubber compound V1—the dissipation of electrostatic charges via the tread base and thus via the aforementioned dissipation path is ensured.

[0148] The invention is not limited to the described embodiment.

[0149] The tread has at least one tread layer made of a correspondingly designed, electrically conductive rubber material, spaced from the outer tread surface located in the tread periphery, wherein the tread layer, viewed in cross-section, preferably extends in the axial direction over at least 50% of the width B of the ground contact area. This tread layer is connected to at least one electrically conductive element extending to the outer tread surface. In the context of the present invention, an electrically conductive material is understood to be one having a specific electrical resistance of < 10 6Ohm m. The electrically conductive material (e.g. rubber material, rubber coating, fabric, coating, suspension) underlying the respective tire component (e.g. element 6 or passage) therefore has a specific electrical resistance of < 10 6 Ohm m on.

[0150] List of reference symbols

[0151] 1 tread

[0152] 1 i Tread cap

[0153] I2 tread base

[0154] 1a Tread outer surface 2 Belt assembly

[0155] 3 side wall

[0156] 4 Carcass insert

[0157] 5 inner layer

[0158] 6 electrically conductive element 7 circumferential groove

[0159] A Double arrow (axial direction)

[0160] AA line (tyre equatorial plane)

[0161] B Width

[0162] R double arrow (radial direction)

Claims

Patent claims 1. Vehicle tire with a tread (1) with an outer tread surface (1a) located in the tread periphery, wherein the vehicle tire has at least one discharge path for discharging electrostatic charges to the tread outer surface (1a), wherein the tread (1) has a radially outer tread layer (1i) made of an electrically non-conductive rubber material, which co-forms the tread outer surface (1a), and at least one tread layer (I2) made of an electrically conductive rubber material and is spaced from the tread outer surface (1a), which belongs to the discharge path, characterized in that the electrically conductive rubber material of the tread layer (I2) spaced from the tread outer surface (1a) has a) a rebound resilience at 70°C, determined according to ISO 4662, of at least 68.0%, b) a Shore A hardness at 70°C, determined according to DIN EN ISO 868, of at least 58.0 ShA, c) an elongation at break at 100°C,determined according to DIN 53504, of at least 450% and d) a specific electrical resistance of maximum 1 ,0 x 10, 6 Q m.

2. Vehicle tire according to claim 1, characterized in that the tread (1) consists in the radial direction of a tread cap (1 i) containing the complete profiling and a tread base (I2), wherein the tread base (I2) is the tread layer (I2) made of the electrically conductive rubber material spaced from the tread outer surface (1a).

3. Vehicle tyre according to claim 1 or 2, characterised in that the rebound resilience at 70°C, determined according to ISO 4662, of the electrically conductive rubber material of the tread layer (I2) spaced from the tread outer surface (1a) is at least 70.0%.

4. Vehicle tire according to one of claims 1 to 3, characterized in that the Shore A hardness at 70°C, determined according to DIN EN ISO 868, of the electrically conductive rubber material of the tread layer (I2) spaced from the tread outer surface (1a) is at least 60.0 ShA.

5. Vehicle tire according to one of claims 1 to 4, characterized in that the elongation at break at 100°C, determined according to DIN 53504, of the electrically conductive rubber material of the tread layer (I2) spaced from the tread outer surface (1a) is at least 470%, preferably at least 490%.

6. Vehicle tyre according to one of claims 1 to 5, characterised in that the specific electrical resistance of the electrically conductive rubber material of the tread layer (I2) spaced apart from the tread outer surface (1a) is at most 5.0 x 10 5 Q m, preferably maximum 1 ,0 x 10 5 Q m, particularly preferably 5.0 x 10 4Q m, most preferably 1 ,0 x 10 4 Q m.

7. Vehicle tire according to one of claims 1 to 6, characterized in that the electrically conductive rubber material of the tread layer (I2) spaced from the tread outer surface (1a) has a loss factor tan d at a temperature of 70°C, determined according to ISO 4664-1, of maximum 0.100, in particular of maximum 0.

090.

8. Vehicle tyre according to one of claims 1 to 7, characterised in that the electrically conductive rubber material of the tread layer (I2) spaced apart from the tread outer surface (1a) has a stress value at an elongation of 200% and a temperature of 70°C, determined according to DIN 53504, of at least 6.5 MPa, in particular of at least 7.0 MPa, and preferably of at least 7.5 MPa.

9. Vehicle tire according to one of claims 1 to 8, characterized in that the electrically conductive rubber material of the tread layer (I2) spaced from the tread outer surface (1a) has a tensile strength at a temperature of 100°C, determined according to DIN 53504, of at least 16.0 MPa, in particular of at least 17.0 MPa, preferably of at least 18.0 MPa.

10. Vehicle tyre according to one of claims 1 to 9, characterised in that the electrically conductive rubber material of the tread layer (I2) spaced apart from the tread outer surface (1a) is made of a rubber mixture which contains one or more carbon black(s) having the following properties: - Oil absorption number according to ASTM D 3493:2021 from 150 ml / 100 g to 190 ml / 100 g, in particular from 166 ml / 100 g to 180 ml / 100 g, - Iodine adsorption number according to NF T45-111 ; NF ISO 1304 of 78 mg / g to 95 mg / g, in particular up to 88 mg / g, - Nitrogen adsorption number according to ASTM D 6556-21 of 73 m 2 / g up to 83 m 2 / G, - Color intensity according to ISO 5435 from 90% to 110%, in particular up to 102%.

11. Vehicle tire according to claim 10, characterized in that the rubber mixture of the electrically conductive rubber material of the tread layer (I2) spaced from the tread outer surface (1a) contains no further carbon black(s).

12. Vehicle tire according to claim 10 or 11, characterized in that in the rubber mixture of the electrically conductive rubber material of the tread layer (I2) spaced from the tread outer surface (1a) carbon black(s) is / are contained in a total amount of 40.0 phr to 50.0 phr, in particular of up to 45.0 phr.

13. Vehicle tyre according to one of claims 1 to 12, characterised in that the tread layer (12) spaced apart from the tread outer surface (1a) extends, viewed in cross-section, in the axial direction over at least 50% of the width (B) of the ground contact area of the tread (1).

14. Vehicle tire according to one of claims 1 to 13, which is a passenger car, van, SUV or commercial vehicle tire.

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