Tire comprising a dual tread

Abstract

The invention relates to a tire comprising a double layer tread. The present invention relates to a pneumatic tire comprising a double layer tread made of a first layer comprising a first tread compound having a first tread performance and a second layer comprising a second tread compound having a second tread performance.

Description

Technical Field

[0001] The present invention relates to a pneumatic tire comprising a double-layer tread made of a first layer comprising a first tread rubber compound having first tread properties and a second layer comprising a second tread rubber compound having second tread properties. Background Art

[0002] For racing, the performance of the tire is very specific in order to meet different weather conditions. The tread shape of the pneumatic tire used for racing is different from the tread shape of the pneumatic tire used for, for example, a passenger car. The performances that the competition is concerned about are wet traction, dry traction, tread wear, thermal conductivity and electrical conductivity. In particular, it is important to achieve fast and effective fatigue heat build-up (heat build-up) of the tread rubber in the tire used for racing. In fact, the racing tire is heated via, for example, a heating jacket so as to be within its operating / performance temperature window. This allows to improve its performance, such as grip on the track. Due to obvious environmental reasons, the use of such heating jackets should be reduced or even stopped.

[0003] Therefore, there is a clear need to provide improved tread compounds that are capable of achieving improved fatigue heating under dry and / or wet conditions without the use of external heating sources. Summary of the invention

[0004] Thus, the present invention relates to a pneumatic tire comprising a tread having a ground engaging surface, the tread being a double-layer tread made from

[0005] - a first layer comprising a first tread rubber compound having a loss compliance LC(1);

[0006] - a second layer comprising a second tread rubber compound having a loss compliance LC(2);

[0007] wherein both the loss compliances LC(1) and LC(2) are measured by a dynamic mechanical analysis system at a frequency of 10 Hz, at a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep from 0°C to 130°C;

[0008] When the tread temperature is between 5°C and 50°C, LC(1)>LC(2);

[0009] In the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.5:1 to 10:1.

[0010] The present invention further relates to a pneumatic tire comprising a tread having a ground engaging surface, the tread being a double-ply tread made from

[0011] - a first layer comprising a first tread rubber compound having a loss modulus E" (1);

[0012] - a second layer comprising a second tread rubber compound having a loss modulus E"(2);

[0013] wherein both the loss modulus E" (1) and E" (2) are measured by a dynamic mechanical analysis (DMA) system at a frequency of 10 Hz, at a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep from 0°C to 130°C;

[0014] Wherein when the tread temperature is between 0°C and 20°C, E”(1)>E”(2);

[0015] In the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.5:1 to 10:1.

[0016] definition

[0017] “Loss Compliance” or “LC” is the loss of E” with respect to (E * ) 2 LC=E” / (E * ) 2 A higher loss compliance value indicates that the material is more compliant and is able to dissipate more energy, such as generating heat, when subjected to mechanical stress. E" stands for loss modulus, Denotes Young's complex modulus, and E' denotes storage modulus. In the context of the present invention, the loss compliance LC is determined by a dynamic mechanical analysis (DMA) system at a frequency of 10 Hz, a pre-strain of 10% and a dynamic strain of 2.5% at a temperature scan from 0°C to 130°C. The DMA system is a system from Netzsch called 150N machine.

[0018] E" is the loss modulus and is determined by a dynamic mechanical analysis (DMA) system at a frequency of 10 Hz, a pre-strain of 10% and a dynamic strain of 2.5% at a temperature sweep from 0°C to 130°C. The DMA system is a product from Netzsch called 150N machine.

[0019] The "glass transition temperature" or "Tg" of a material (in this case a polymer) is the temperature region over which the polymer changes from a rigid "glass" state to a flexible "rubber" state. Tg is determined as the midpoint of the peak by differential scanning calorimetry (DSC) at a ramp rate of 20°C / min according to ASTM D3418 or equivalent. In the context of the present invention, Tg is measured by The apparatus was used to measure Tg in a temperature sweep from -80°C to 40°C at 10% prestress and 0.25% amplitude, and Tg was determined by the maximum value of tan δ = E" / E'.

[0020] In the context of the present invention, the term "operating window" refers to the optimum temperature range (not too cold and not too hot) for a pneumatic racing tire to have ultimate grip without causing excessive tire degradation and / or loss of ultimate grip.

[0021] The present invention discloses the following scheme:

[0022] Solution 1. A pneumatic tire comprising a tread having a ground engaging surface, the tread being a double-layer tread made from

[0023] - a first layer comprising a first tread rubber compound having a loss compliance LC(1);

[0024] - a second layer comprising a second tread rubber compound having a loss compliance LC(2);

[0025] wherein both the loss compliances LC(1) and LC(2) are measured by a dynamic mechanical analysis system at a frequency of 10 Hz, at a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep from 0°C to 130°C;

[0026] When the tread temperature is between 5°C and 50°C, LC(1)>LC(2);

[0027] In the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.5:1 to 10:1.

[0028] Aspect 2. The pneumatic tire according to aspect 1, wherein the second tread rubber compound is a polymer rubber compound having a glass transition temperature Tg(2) of -10°C to 15°C.

[0029] Solution 3. The pneumatic tire according to Solution 1 or 2, wherein the dry traction of the second tread rubber compound is higher than the dry traction of the first tread rubber compound.

[0030] A pneumatic tire comprising a tread having a ground engaging surface, the tread being a double-layer tread made from

[0031] - a first layer comprising a first tread rubber compound having a loss modulus E" (1);

[0032] - a second layer comprising a second tread rubber compound having a loss modulus E"(2);

[0033] wherein both the loss modulus E" (1) and E" (2) are measured by a dynamic mechanical analysis (DMA) system at a frequency of 10 Hz, at a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep from 0°C to 130°C;

[0034] Wherein when the tread temperature is between 0°C and 20°C, E”(1)>E”(2);

[0035] In the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.5:1 to 10:1.

[0036] Aspect 5. The pneumatic tire according to Aspect 4, wherein the second tread rubber compound is a polymer rubber compound having a glass transition temperature Tg(2) of -20°C to 0°C.

[0037] Aspect 6. The pneumatic tire according to aspect 4 or 5, wherein the wet traction of the second tread rubber compound is higher than the wet traction of the first tread rubber compound.

[0038] Aspect 7. The pneumatic tire according to aspect 1 or 4, wherein the tread is formed by extruding the first tread rubber material and the second tread rubber material to form a double-layer strip.

[0039] Aspect 8. The pneumatic tire according to Aspect 7, wherein the double-layer tread is formed by continuous spiral winding of a double-layer strip.

[0040] Aspect 9. The pneumatic tire according to aspect 1 or 4, wherein the double-layer tread is formed by sequentially extruding a first tread rubber material and a second tread rubber material.

[0041] Aspect 10. The pneumatic tire according to aspect 1 or 4, wherein in the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.60:1 to 10:1.

[0042] Aspect 11. The pneumatic tire according to Aspect 1 or 4, which is a racing tire.

[0043] Aspect 12. The pneumatic tire according to aspect 1 or 4, wherein the cross-sectional shape of the first layer is substantially triangular, preferably triangular.

[0044] Aspect 13. A pneumatic tire according to aspect 12, wherein the second layer has an inverted substantially triangular cross-sectional shape compared to the first layer, preferably an inverted triangular cross-sectional shape compared to the first layer.

[0045] Aspect 14. The pneumatic tire according to aspect 12, wherein in the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.6:1 to 1.5:1.

[0046] Aspect 15. A pneumatic tire according to aspect 14, wherein the outermost surface of the first layer is a first ground engaging surface, and the outermost surface of the second layer is a second ground engaging surface, the first ground engaging surface and the second ground engaging surface forming a ground engaging surface of the tread.

[0047] Aspect 16. The pneumatic tire according to aspect 1 or 4, wherein the cross-sectional shape of the first layer is substantially trapezoidal, preferably trapezoidal.

[0048] Aspect 17. The pneumatic tire according to Aspect 16, wherein the cross-sectional shape of the second layer is substantially trapezoidal, preferably trapezoidal.

[0049] Aspect 18. The pneumatic tire according to aspect 16, wherein in the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 2:1 to 9:1.

[0050] Aspect 19. The pneumatic tire of aspect 18, wherein the outermost surface of the first layer is a first ground engaging surface, and the outermost surface of the second layer is a second ground engaging surface, the first ground engaging surface and the second ground engaging surface forming a ground engaging surface of the tread.

[0051] Aspect 20. The pneumatic tire of aspect 16, wherein the outermost surface of the second layer is a ground engaging surface of the tread, and the first layer does not have a ground engaging surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present invention will be described by way of example and with reference to the accompanying drawings, in which:

[0053] Figure 1 is a schematic illustration of a portion of a double-layer tread 10 included in a pneumatic tire according to the present invention.

[0054] Figure 2 is a schematic illustration of a portion of a double-layer tread 100 included in a pneumatic tire according to the present invention.

[0055] Figure 3 is a schematic illustration of a portion of a double-layer tread 200 included in a pneumatic tire according to the present invention.

[0056] Figure 4 The loss compliances LC(1) and LC(2) (dry conditions) of the polymer tread compound of the pneumatic tire according to the present invention are shown.

[0057] Figure 5 The loss modulus E" (1) and E" (2) (wet conditions) of the polymer tread compound of the pneumatic tire according to the present invention are shown. Specific implementation plan

[0058] The present invention relates to a pneumatic tire comprising a tread having a ground engaging surface, the tread being a double-layer tread made of

[0059] - a first layer comprising a first tread rubber compound having a loss compliance LC(1);

[0060] - a second layer comprising a second tread rubber compound having a loss compliance LC(2);

[0061] wherein both the loss compliances LC(1) and LC(2) are measured by a dynamic mechanical analysis system at a frequency of 10 Hz, at a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep from 0°C to 130°C;

[0062] When the tread temperature is between 5°C and 50°C, LC(1)>LC(2);

[0063] In the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.5:1 to 10:1.

[0064] Preferably, the second tread compound is a polymer compound having a glass transition temperature Tg(2) between -10°C and 15°C, more preferably between -5°C and 15°C, more preferably between -5°C and 10°C.

[0065] Preferably, the first tread compound is a polymer compound having a glass transition temperature Tg(1) between -25°C and +10°C, more preferably between -20°C and +5°C, more preferably between -18°C and +3°C.

[0066] Preferably, the dry traction of the second tread rubber compound is higher than the dry traction of the first tread rubber compound.

[0067] Preferably, the pneumatic tire has an operating window of 80°C to 120°C.

[0068] Preferably, the pneumatic tyre is suitable for use in dry conditions. Preferably, the pneumatic tyre is used in dry conditions.

[0069] Preferably, the minimum ratio of LC(1) to LC(2) is about 1.15:1, more preferably about 1.2:1. Preferably, the maximum ratio of LC(1) to LC(2) is about 4:1, more preferably about 3:1.

[0070] The present invention further relates to a pneumatic tire comprising a tread having a ground engaging surface, the tread being a double-ply tread made from

[0071] - a first layer comprising a first tread rubber compound having a loss modulus E" (1);

[0072] - a second layer comprising a second tread rubber compound having a loss modulus E"(2);

[0073] wherein both the loss modulus E" (1) and E" (2) are measured by a dynamic mechanical analysis (DMA) system at a frequency of 10 Hz, at a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep from 0°C to 130°C;

[0074] Wherein when the tread temperature is between 0°C and 20°C, E”(1)>E”(2);

[0075] In the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.5:1 to 10:1.

[0076] Preferably, the second tread compound is a polymer compound having a glass transition temperature Tg(2) between -20°C and 0°C, more preferably between -15°C and -1°C, more preferably between -10°C and -3°C.

[0077] Preferably, the first tread compound is a polymer compound having a glass transition temperature Tg(1) between 0°C and 10°C, more preferably between 0°C and 5°C, more preferably between 1°C and 4°C.

[0078] Preferably, Tg(1)>Tg(2).

[0079] Preferably, the wet traction of the second tread rubber compound is higher than the wet traction of the first tread rubber compound.

[0080] Preferably, the pneumatic tire has an operating window of 20°C to 70°C.

[0081] Preferably, the pneumatic tyre is suitable for use in wet conditions. Preferably, the pneumatic tyre is used in wet conditions.

[0082] Preferably, the ratio of E"(1) to E"(2), E"(1) / E"(2), is in the range of 1.3:1 to 3:1, more preferably in the range of 1.5:1 to 2:1.

[0083] According to the invention, due to the higher loss compliance or higher loss modulus of the first layer compared to the second layer of the pneumatic tire according to the invention, more heat is generated in the first layer compared to the second layer. Therefore, the generation of a large amount of heat by the first layer of the pneumatic tire according to the invention will help the second layer to reach its optimal temperature much faster than usual (i.e. in the absence of the first layer).

[0084] In the context of the present invention, the first tread rubber material and the second tread rubber material are different from each other in physical properties. In addition, the first tread rubber material and the second tread rubber material are different from each other chemically.

[0085] Preferably, the tread is formed by extruding a first tread rubber material and a second tread rubber material to form a double-layer strip.

[0086] Preferably, the double-ply tread is formed by a continuous helical winding of a double-ply strip.

[0087] Preferably, the tread is formed from a double layer of strip continuously spirally wound onto a tire building drum or carcass.

[0088] Preferably, the width of the double-layer strip corresponds to the width of the tread of the pneumatic tire. Figure 3 ), preferably, the double-layer strip thickness is (or is equivalent to) the thickness of the tread, the thickness of the double-layer strip being determined by the maximum distance between the outermost surface of the double-layer strip (i.e. the ground engaging surface of the tread) and the innermost surface of the double-layer strip. Preferably, the double-layer strip has a thickness of 3 mm to 6 mm, preferably 3.5 mm to 4.5 mm, the double-layer strip thickness being the thickness of the tread, the thickness of the double-layer strip being determined by the maximum distance between the outermost surface of the double-layer strip (i.e. the ground engaging surface of the tread) and the innermost surface of the double-layer strip.

[0089] Alternatively, preferably, the width of the double-layer strip is < the width of the tread of the pneumatic tire. In fact, according to said alternative, the double-layer strip is preferably arranged to form a stack of layers that will form the tread. This alternative is for example Figure 1 and 2 Preferably, the double-layer strip has a thickness of 1 mm to 3 mm, more preferably 1.5 mm to 2 mm. Preferably, according to the alternative, the double-layer strip has a width of 10 mm to 25 mm. The shape of the double-layer strip is disclosed, for example, in US2022 / 0063340A1.

[0090] Preferably, the double-layer tread is formed by sequentially extruding a first tread rubber material and a second tread rubber material. More preferably, the double-layer tread is formed by extruding the first tread rubber material by spiral winding to form a first layer of the tread, and then extruding the second tread rubber material by spiral winding on the first layer to form a second layer.

[0091] Preferably, the first layer consists of a first tread rubber compound.

[0092] Preferably, the second layer consists of a second tread rubber compound.

[0093] Preferably, in the tread, the volume ratio of the second tread rubber material to the first tread rubber material is 0.60:1 to 10:1, more preferably 0.80:1 to 9:1, more preferably 0.85:1 to 9:1, more preferably 0.9:1 to 8:1.

[0094] Preferably, the volume ratio of the second tread compound to the first tread compound at the ground engaging surface of the tread is from 0.60:1 to 10:1, more preferably from 0.80:1 to 9:1, more preferably from 0.85:1 to 9:1, more preferably from 0.9:1 to 8:1.

[0095] Preferably, the pneumatic tire according to the invention is a racing tire.

[0096] Double strips

[0097] Preferably, the cross-section of the first layer is substantially triangular, more preferably triangular.Preferably, the second layer has an inverted substantially triangular cross-sectional shape compared to the first layer, more preferably an inverted triangular cross-sectional shape compared to the first layer.

[0098] Preferably, in the tread, the volume ratio of the second tread rubber material to the first tread rubber material is 0.6:1 to 1.5:1, preferably 0.85:1 to 1.25:1, more preferably 0.9:1 to 1.1:1, more preferably 0.95:1 to 1.05:1.

[0099] Preferably, the outermost surface of the first layer is a first ground engaging surface and the outermost surface of the second layer is a second ground engaging surface, the first ground engaging surface and the second ground engaging surface forming the ground engaging surface of the tread. Figure 1 Shown.

[0100] Alternatively, preferably, the cross-sectional shape of the first layer is substantially trapezoidal, more preferably trapezoidal.

[0101] Preferably, the cross-sectional shape of the second layer is substantially trapezoidal, preferably trapezoidal.

[0102] Preferably, the volume ratio of the second tread rubber material to the first tread rubber material in the tread is 2:1 to 9:1, more preferably 3:1 to 8:1, more preferably 4:1 to 5:1. More preferably, the outermost surface of the first layer is the first ground engaging surface, and the outermost surface of the second layer is the second ground engaging surface, the first ground engaging surface and the second ground engaging surface forming the ground engaging surface of the tread. The construction is composed of, for example Figure 2 Alternatively, preferably, the outermost surface of the second layer is the ground engaging surface of the tread and the first layer has no ground engaging surface. Figure 3 Shown.

[0103] Preferably, the tread has a width of between 130 mm and 360 mm, more preferably between 160 mm and 320 mm. Preferably, the tread has a thickness of between 3 mm and 6 mm, preferably between 3.5 mm and 4.5 mm, the tread thickness being determined by the maximum distance between the outermost surface of the tread (i.e. the ground engaging surface of the tread) and the innermost surface of the tread.

[0104] Preferably, the tread comprises one or more circumferential grooves.Alternatively, preferably, the tread comprises no circumferential grooves.

[0105] The invention is further illustrated by the following groups of embodiments and combinations of embodiments resulting from dependencies and back-references as described. In particular, it is noted that in each case where a series of embodiments is mentioned, for example in the context of a term such as "a pneumatic tire as described in any one of embodiments 1 to 3", each embodiment in the series is meant to be explicitly disclosed to a person skilled in the art, i.e. the wording of the term should be understood by a person skilled in the art as being synonymous with "a pneumatic tire as described in any one of embodiments 1, 2 and 3". In addition, it is explicitly noted that the following groups of embodiments represent a suitable structural part of the general description relating to the preferred aspects of the invention and therefore appropriately support, but do not represent, solutions of the invention.

[0106] According to Embodiment 1 of the present invention, a pneumatic tire includes a tread having a ground engaging surface, the tread being a double-layer tread made of

[0107] - a first layer comprising a first tread rubber compound having a loss compliance LC(1);

[0108] - a second layer comprising a second tread rubber compound having a loss compliance LC(2);

[0109] wherein both the loss compliances LC(1) and LC(2) are measured by a dynamic mechanical analysis system at a frequency of 10 Hz, at a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep from 0°C to 130°C;

[0110] When the tread temperature is between 5°C and 50°C, LC(1)>LC(2);

[0111] In the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.5:1 to 10:1.

[0112] Embodiment 2: The pneumatic tire of Embodiment 1, wherein the second tread rubber compound is a polymer rubber compound having a glass transition temperature Tg(2) of -10°C to 15°C, more preferably -5°C to 15°C, preferably -5°C to 10°C.

[0113] Embodiment 3: The pneumatic tire of embodiment 1 or 2, wherein the pneumatic tire is suitable for dry running conditions, and preferably the dry traction of the second tread rubber material is higher than the dry traction of the first tread rubber material.

[0114] Embodiment 4: The pneumatic tire of any one of Embodiments 1 to 3, wherein the minimum ratio of LC(1) to LC(2) is about 1.15:1, preferably about 1.2:1; wherein the maximum ratio of LC(1) to LC(2) is about 4:1, preferably about 3:1.

[0115] According to embodiment 5 of the present invention, the pneumatic tire includes a tread having a ground engaging surface, the tread being a double-layer tread made of

[0116] - a first layer comprising a first tread rubber compound having a loss modulus E" (1);

[0117] - a second layer comprising a second tread rubber compound having a loss modulus E"(2);

[0118] wherein both the loss modulus E" (1) and E" (2) are measured by a dynamic mechanical analysis (DMA) system at a frequency of 10 Hz, at a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep from 0°C to 130°C;

[0119] Wherein when the tread temperature is between 0°C and 20°C, E”(1)>E”(2);

[0120] In the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.5:1 to 10:1.

[0121] Embodiment 6: The pneumatic tire of Embodiment 5, wherein the second tread rubber compound is a polymer rubber compound having a glass transition temperature Tg(2) of -20°C to 0°C, more preferably -15°C to -1°C, preferably -10°C to -3°C.

[0122] Embodiment 7: The pneumatic tire of Embodiment 5 or 6, wherein the pneumatic tire is suitable for wet conditions, and preferably the wet traction of the second tread rubber material is higher than the wet traction of the first tread rubber material.

[0123] Embodiment 8: The pneumatic tire of any one of Embodiments 5 to 7, wherein the minimum ratio of E”(1) to E”(2), E”(1) / E”(2), is about 1.3:1, preferably about 1.5:1; wherein the maximum ratio of E”(1) to E”(2), E”(1) / E”(2), is about 3:1, more preferably about 2:1.

[0124] Embodiment 9: The pneumatic tire of any one of Embodiments 1 to 8, wherein the tread is formed by extruding the first tread rubber material and the second tread rubber material to form a double-layer strip.

[0125] Embodiment 10: The pneumatic tire of Embodiment 9, wherein the dual-ply tread is formed by continuous spiral windings of a dual-ply strip.

[0126] Embodiment 11: The pneumatic tire of embodiment 9 or 10, wherein the width of the double-layer strip is equivalent to the width of the tread of the pneumatic tire, wherein preferably, the thickness of the double-layer strip is the thickness of the tread, and the thickness of the double-layer strip is determined by the maximum distance between the outermost surface of the double-layer strip (i.e., the ground engaging surface of the tread) and the innermost surface of the double-layer strip, wherein more preferably, the double-layer strip has a thickness of 3 mm to 6 mm, preferably 3.5 mm to 4.5 mm, and the thickness of the double-layer strip is the thickness of the tread, and the thickness of the double-layer strip is determined by the maximum distance between the outermost surface of the double-layer strip (i.e., the ground engaging surface of the tread) and the innermost surface of the double-layer strip.

[0127] Embodiment 12: The pneumatic tire of embodiment 9 or 10, wherein the width of the double-layer strip is < the width of the tread of the pneumatic tire; wherein preferably, the double-layer strip has a thickness of 1 mm to 3 mm, more preferably 1.5 mm to 2 mm; and / or wherein preferably the double-layer strip has a width of 10 mm to 25 mm.

[0128] Embodiment 13: The pneumatic tire of any one of Embodiments 1 to 8, wherein the double-layer tread is formed by sequentially extruding a first tread rubber material and a second tread rubber material.

[0129] Embodiment 14: The pneumatic tire of any one of Embodiments 1 to 13, wherein the first layer consists of (is made of) the first tread rubber compound.

[0130] Embodiment 15: The pneumatic tire of any one of Embodiments 1 to 14, wherein the second layer is composed of (made from) the first tread rubber compound.

[0131] Embodiment 16: The pneumatic tire of any one of Embodiments 1 to 15, wherein the volume ratio of the second tread rubber material to the first tread rubber material in the tread is 0.60:1 to 10:1, preferably 0.80:1 to 9:1, more preferably 0.85:1 to 9:1, more preferably 0.9:1 to 8:1; wherein more preferably, the volume ratio of the second tread rubber material to the first tread rubber material at the ground engaging surface of the tread is 0.60:1 to 10:1, more preferably 0.80:1 to 9:1, more preferably 0.85:1 to 9:1, more preferably 0.9:1 to 8:1.

[0132] Embodiment 17: The pneumatic tire of any one of Embodiments 1 to 16, which is a racing tire.

[0133] Embodiment 18: The pneumatic tire of any one of Embodiments 1 to 17, wherein the cross-sectional shape of the first layer is substantially triangular, preferably triangular.

[0134] Embodiment 19: The pneumatic tire of Embodiment 18, wherein the second layer has an inverted substantially triangular cross-sectional shape compared to the first layer, preferably an inverted triangular cross-sectional shape compared to the first layer.

[0135] Embodiment 20: The pneumatic tire of embodiment 18 or 19, wherein the volume ratio of the second tread rubber material to the first tread rubber material in the tread is 0.6:1 to 1.5:1, preferably 0.85:1 to 1.25:1, more preferably 0.9:1 to 1.1:1, and more preferably 0.95:1 to 1.05:1.

[0136] Embodiment 21: The pneumatic tire of Embodiment 20, wherein the outermost surface of the first layer is a first ground engaging surface and the outermost surface of the second layer is a second ground engaging surface, the first ground engaging surface and the second ground engaging surface forming a ground engaging surface of the tread.

[0137] Embodiment 22: The pneumatic tire of any one of Embodiments 1 to 17, wherein the cross-sectional shape of the first layer is substantially trapezoidal, preferably trapezoidal.

[0138] Embodiment 23: The pneumatic tire of Embodiment 22, wherein the cross-sectional shape of the second layer is substantially trapezoidal, preferably trapezoidal.

[0139] Embodiment 24: The pneumatic tire of Embodiment 22 or 23, wherein in the tread, the volume ratio of the second tread rubber material to the first tread rubber material is 2:1 to 9:1, preferably 3:1 to 8:1, and more preferably 4:1 to 5:1.

[0140] Embodiment 25: The pneumatic tire of Embodiment 24, wherein the outermost surface of the first layer is a first ground engaging surface and the outermost surface of the second layer is a second ground engaging surface, the first ground engaging surface and the second ground engaging surface forming a ground engaging surface of the tread.

[0141] Embodiment 26: The pneumatic tire of Embodiment 22, wherein the outermost surface of the second layer is a ground engaging surface of the tread, and the first layer does not have a ground engaging surface.

[0142] Embodiment 27: The pneumatic tire of any of Embodiments 1 to 26, wherein the tread includes one or more circumferential grooves.

[0143] Embodiment 28: The pneumatic tire of any of Embodiments 1 to 25, wherein the tread does not include circumferential grooves.

[0144] In the context of the present invention, the tread of the pneumatic tire of the present invention can be prepared according to any method known in the art. In particular, the tread of the pneumatic tire of the present invention can be prepared according to the method as described in US2011 / 0070325A1, which is incorporated herein by reference.

[0145] In the context of the present invention, the tread of the pneumatic tire of the present invention can be prepared according to the method as described in US 2022 / 0063340A1, which is incorporated herein by reference. In particular, the present invention further relates to a method for forming a tread, the method comprising the following steps: selecting a first tread rubber material having a first physical property, such as LC(1) or E"(1), and selecting a second tread rubber material having a second physical property, such as LC(2) or E"(2), respectively, forming the tread by winding a double-layer strip, the double-layer strip having a first layer formed by the first tread rubber material and a second layer formed by the second tread rubber material, wherein the volume ratio of the second tread rubber material to the first tread rubber material in the tread is between 0.5:1 and 10:1. Preferably, in particular for tires for dry conditions, the present invention further relates to a method for forming a tread, the method comprising the following steps: selecting a first tread rubber material having a loss compliance LC(1), and selecting a second tread rubber material having a loss compliance LC(2), forming the tread by winding a double-layer strip, the double-layer strip having a first layer formed by the first tread rubber material and a second layer formed by the second tread rubber material, wherein in the tread the volume ratio of the second tread rubber material to the first tread rubber material is between 0.5:1 and 10:1, wherein both the loss compliances LC(1) and LC(2) are measured by a dynamic mechanical analysis system at a frequency of 10 Hz, a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep of 0°C to 130°C; and wherein, when the tread temperature is between 5°C and 50°C, LC(1)>LC(2). Optionally, in particular for tires under wet conditions, the present invention further relates to a method for forming a tread, the method comprising the following steps: selecting a first tread rubber material having a loss modulus E”(1), and selecting a second tread rubber material having a loss modulus E”(2), forming the tread by winding a double-layer strip, the double-layer strip having a first layer formed by the first tread rubber material and a second layer formed by the second tread rubber material, wherein in the tread the volume ratio of the second tread rubber material to the first tread rubber material is between 0.5:1 and 10:1, wherein the loss modulus E”(1) and E”(2) are both measured as described above; and wherein, when the tread temperature is between 0°C and 20°C, E”(1)>E”(2).

[0146] In order to form the tread included in the tire of the present invention, an apparatus as described in US 2022 / 0063340A1 can be used. Such an apparatus according to the present invention can form a coextruded double-layer strip while instantaneously changing the volume ratio of the first rubber compound to the second rubber compound. The double-strip forming apparatus comprises a first extruder and a second extruder, preferably arranged vertically in close proximity. The first extruder has an inlet for receiving the first tread rubber compound, while the second extruder has an inlet for receiving the second tread rubber compound. The first tread rubber compound is extruded by the first extruder and then pumped into the nozzle by the first gear pump, while the second tread rubber compound is extruded by the second extruder and then pumped into the nozzle by the second gear pump. The volume ratio of the second tread rubber compound relative to the first tread rubber compound in the tread can be changed by changing the ratio of the speed of the gear pump of the first tread rubber compound to the speed of the gear pump of the second tread rubber compound. The double coextrusion strip forming apparatus can adjust the speed ratio instantly, and because the residence time of the coextrusion nozzle is short, the apparatus has a rapid response to changes in the rubber compound ratio. This is due to the small volume of the coextrusion area.

[0147] Example

[0148] A pneumatic racing tire according to the present invention (tire of the present invention) is prepared, in particular the pneumatic racing tire has a tread formed via an extrusion process of a double-layer strip (having a bottom layer and a top layer, the outer surface of the top layer being the ground engaging surface of the tread), the top layer being made from a second tread compound having a loss modulus E”(2), and the bottom layer being made from a first tread compound having a loss modulus E”(1), wherein, at a tread temperature of 0°C to 20°C, E”(1)>E”(2). The volume ratio of the second tread compound to the first tread compound in the tread is greater than 3:1, the first tread compound being a polymer tread compound having a Tg of +3°C, and the second tread compound being a polymer tread compound having a Tg of -3°C. In this particular embodiment, at a tread temperature of about 10°C, E”(1)=8.0 MPa and E”(2)=6.2 MPa (see Figure 5 ).

[0149] A pneumatic racing tire not according to the invention (reference tire) was prepared, in particular having a tread formed by an extrusion process of a single-layer strip made from a tread compound having a loss modulus of 5.3 MPa at a tread temperature of about 10° C. The tread compound was a polymer tread compound having a Tg of −3° C. The chemical composition of the tread compound of this comparative tire was identical to that of the second tread compound of the tire of the invention.

[0150] The tires of the invention and the comparative tires were mounted on different motorcycles for testing and comparison. The tests were carried out by professional riders on a racing circuit under wet conditions. The ratings ranged from 1 (very poor) to 10 (excellent).

[0151] Table 1

[0152] Reference tire Tire of the present invention Air temperature 15℃ 19℃ Track temperature 15℃ 21℃ <![CDATA[Tire tread temperature * > 48℃ 60℃ <![CDATA[Tire pressure * > 1.39 bar 1.49 bar Total laps (laps) 8 6 Fastest lap Lap 6 Lap 4 Fastest time 2:02.299 (6th lap) 1:52.911 (4th lap) Rear entry stability 5 7 Rear entry grip 5 7 Rear mid-corner grip 5 7 Rear exit grip 5 7 Rear exit stability 5 7 Rear slide control 5 8 Rear confidence 5 7 Total score of rear part 5 7

[0153] * Measure directly after running

[0154] As can be seen from Table 1, the ratings of the tires of the invention are much better than those of the reference tires. The optimum performance is achieved much sooner thanks to the tires of the invention. In fact, the fastest time is achieved already on the 4th lap for the tires of the invention, whereas it is only on the 6th lap with the tires not according to the invention, and moreover, the optimum lap time for the tires of the invention is significantly faster than that for the reference tires. As can be seen from Table 1 above, the tires according to the invention show high stability and grip performances. Moreover, the tires reach the optimum operating window much sooner and are able to maintain this optimum window despite the significant cooling effect due to the water on the track. Thus, it has been demonstrated that, thanks to the double-layer strip made of two tread compounds with different physical properties, here with different loss moduli at a tread temperature of up to 20°C, the bottom layer generates a lot of heat, which helps the top layer to reach its optimum temperature much sooner than usual. It therefore allows to properly adjust the temperature of the tread to obtain the optimum performance in the operating window on a wet track / track. This allows great flexibility in terms of performance, regardless of the racing conditions.

[0155] Figure 1 Schematic illustration of a portion of a double-layer tread 10 included in a pneumatic tire according to the present invention, wherein the tread is made of a first layer 11 and a second layer 12, the first layer 11 comprising a first tread rubber material having a first tread property (loss compliance LC(1) or loss modulus E"(1)), the second layer 12 comprising a second tread rubber material having a second tread physical property (loss compliance LC(2) or loss modulus E"(2)), the first layer and the second layer having been extruded together as a thin double-layer strip, the thin double-layer strip being continuously spirally wound to form the double-layer tread included in the pneumatic tire according to the present invention. The cross-sectional shape of the first layer is triangular, and the second layer has an inverted triangular cross-sectional shape compared to the first layer. The volume ratio of the second tread rubber material to the first tread rubber material in the tread is preferably in the range of 0.6:1 to 1.5:1.

[0156] Figure 21 is a schematic illustration of a portion of a double-layer tread 100 included in a pneumatic tire according to the present invention, wherein the tread is made of a first layer 101 and a second layer 102, the first layer 101 comprising a first tread rubber material having a first tread property (loss compliance LC(1) or loss modulus E"(1)), the second layer 102 comprising a second tread rubber material having a second tread physical property (loss compliance LC(2) or loss modulus E"(2)), the first tread rubber material and the second tread rubber material having been extruded together as a thin double-layer strip, the thin double-layer strip being continuously spirally wound to form the double-layer tread included in the pneumatic tire according to the present invention. The cross-sectional shape of the first layer is trapezoidal, and the cross-sectional shape of the second layer is also trapezoidal. In the tread, the volume ratio of the second tread rubber material to the first tread rubber material is between 2:1 and 9:1.

[0157] Figure 3 is a schematic illustration of a portion of a double-layer tread 200 included in a pneumatic tire according to the present invention, wherein the tread is made of a first (bottom) layer 201 and a second (top) layer 202, wherein the first layer (bottom) 201 includes a first tread rubber material having first tread properties (loss compliance LC(1) or loss modulus E"(1)), and the second (top) layer 202 includes a second tread rubber material having second tread physical properties (loss compliance LC(2) or loss modulus E"(2)). The first tread rubber material and the second tread rubber material have been co-extruded to form a large double-layer strip, the width of which is the width of the tread.

[0158] The present invention may be modified according to the description provided herein. Although certain representative embodiments and details have been shown for the purpose of illustrating the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the present invention. Therefore, it should be understood that changes may be made in the specific embodiments described, and these changes will be within the full expected scope of the present invention as defined by the appended claims.

Claims

1. A pneumatic tire comprising a tread having a ground engaging surface, the tread being a double layer tread made from - a first layer comprising a first tread rubber compound having a loss compliance LC(1); - a second layer comprising a second tread rubber compound having a loss compliance LC(2); wherein both the loss compliances LC(1) and LC(2) are measured by a dynamic mechanical analysis system at a frequency of 10 Hz, at a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep from 0°C to 130°C; When the tread temperature is between 5°C and 50°C, LC(1)>LC(2); In the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.5:1 to 10:

1.

2. The pneumatic tire according to claim 1, wherein the second tread compound is a polymer compound having a glass transition temperature Tg(2) of -10°C to 15°C.

3. The pneumatic tire according to claim 1 or 2, wherein the dry traction of the second tread rubber compound is higher than the dry traction of the first tread rubber compound.

4. A pneumatic tire comprising a tread having a ground engaging surface, the tread being a double layer tread made from - a first layer comprising a first tread rubber compound having a loss modulus E" (1); - a second layer comprising a second tread rubber compound having a loss modulus E"(2); wherein both the loss modulus E" (1) and E" (2) are measured by a dynamic mechanical analysis (DMA) system at a frequency of 10 Hz, at a pre-strain of 10% and a dynamic strain of 2.5% within a temperature sweep from 0°C to 130°C; Wherein when the tread temperature is between 0°C and 20°C, E”(1)>E”(2); In the tread, a volume ratio of the second tread rubber material to the first tread rubber material is in a range of 0.5:1 to 10:

1.

5. The pneumatic tire according to claim 4, wherein the second tread compound is a polymer compound having a glass transition temperature Tg(2) in the range of -20°C to 0°C.

6. The pneumatic tire according to claim 4 or 5, wherein the wet traction of the second tread rubber compound is higher than the wet traction of the first tread rubber compound.

7. The pneumatic tire according to claim 1 or 4, wherein the tread is formed by extruding the first tread rubber material and the second tread rubber material to form a double-layer strip.

8. The pneumatic tire of claim 7, wherein the double-ply tread is formed by continuous spiral windings of a double-ply strip.

9. The pneumatic tire according to claim 1 or 4, wherein the double-layer tread is formed by sequentially extruding a first tread rubber compound and a second tread rubber compound. 10 . The pneumatic tire according to claim 1 , wherein a volume ratio of the second tread rubber material to the first tread rubber material in the tread is in a range of 0.60:1 to 10:1.

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