(19) TZZ¥_Z_T (11) EP 3 196 048 A1 (12) EUROPEAN PATENT APPLICATION published in accordance with Art. 153(4) EPC (43) Date of publication: (51) Int Cl.: 26.07.2017 Bulletin 2017/30 B60C 1/00 (2006.01) B60B 9/26 (2006.01) B60C 7/00 (2006.01) B60C 15/06 (2006.01) (2006.01) (21) Application number: 15849011.0 B60C 17/00 (22) Date of filing: 30.09.2015 (86) International application number: PCT/JP2015/077765 (87) International publication number: WO 2016/056444 (14.04.2016 Gazette 2016/15) (84) Designated Contracting States: •SUGIMOTOMutsuki AL AT BE BG CH CY CZ DE DK EE ES FI FR GB Kobe-shi GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO Hyogo 651-0072 (JP) PL PT RO RS SE SI SK SM TR • IWAMURA Wako Designated Extension States: Kobe-shi BA ME Hyogo 651-0072 (JP) Designated Validation States: • SUGIYA Makoto MA Kobe-shi Hyogo 651-0072 (JP) (30) Priority: 06.10.2014 JP 2014205811 18.12.2014 JP 2014256002 (74) Representative: ManitzFinsterwald Patentanwälte PartmbB (71) Applicant: Sumitomo Rubber Industries, Ltd. Martin-Greif-Strasse 1 Kobe-shi, Hyogo 651-0072 (JP) 80336 München (DE) (72) Inventors: • YOKOYAMA Yuka Kobe-shi Hyogo 651-0072 (JP) (54) RUBBER COMPOSITION FOR TIRES, PNEUMATIC TIRE, AND AN AIRLESS TIRE (57) [ Problem ] To provide a rubber compound for tires, a pneumatic tire and an airless tire capable of improving the steering stability of the tire while exerting excellent low fuel con- sumption performance. [Solution] A rubber compound for tires characterized in that, of vulcanized rubber’s physical properties, a complex elas- tic modulus E*70 (unit: MPa) and a loss tangent tanδ70 under initial strain of 10 %, dynamic strain of 2 % and temperature of 70 degrees C, satisfy 90 < E*70 < 250, and E*70/ tanδ70 > 800. A pneumatic tire provided with a rubber member made of the above-mentioned rubber compound. An airless tire provided with a rubber member made of the above-mentioned rubber compound. An air- less tire provided in a tread ring with a shear rubber layer (107) made of the above-mentioned rubber compound. EP 3 196 048 A1 Printed by Jouve, 75001 PARIS (FR) EP 3 196 048 A1 Description Technical Field 5 [0001] The present invention relates to a rubber compound for tires, a pneumatic tire, and an airless tire capable of improving the steering stability of the tire while exerting excellent low fuel consumption performance. Background Art 10 [0002] Rubber compounds constituting rubber members for tires, for example vulcanized rubber compounds used inside a tire such as a bead apex, is required to have high rigidity in order to improve the steering stability. [0003] For the purpose of increasing rigidity of vulcanized rubber compounds, there have been proposed adding a large amount of filler, adding a thermosetting resin (patent document 1), adding fibrous fillers (patent document 2), blending butadiene rubber comprising 1, 2-syndiotactic polybutadiene crystals (SPB) (patent document 3). 15 [0004] However, the above listed methods tend to deteriorate the low fuel consumption property which is an important performance requirement. For example, a rubber compound having a complex elastic modulus higher than 90 MPa, significantly deteriorates the low fuel consumption properties, therefore, it is difficult to use it for a tire practically. [0005] In view of the above, the inventors of the present invention have conducted various researches. As a result, the inventors of the present invention have succeeded in providing a rubber compound capable of satisfying both high 20 elasticity and low fuel consumption property in a range previously not reached by improving combination of materials composing the rubber compound which have been individually known (hereafter, may be referred to as "compounding tuning"). Prior art document 25 Patent document [0006] 30 Patent document 1: Japanese Patent Application Publication No. 2009-127041 Patent document 2: Japanese Patent Application Publication No. 2013-253222 Patent document 3: Japanese Patent Application Publication No. 2012-97280 Summary of the Invention 35 Problems to be Solved by the Invention [0007] It is an object of the present invention to provide a rubber compound for tires, a pneumatic tire and an airless tire capable of improving steering stability while exerting excellent low fuel consumption property. 40 Means for Solving the Problem [0008] The present invention is a rubber compound for tires characterized in that, of vulcanized rubber’s physical properties, a complex elastic modulus E* 70 (unit: MPa) and a loss tangent tanδ70 under 45 an initial strain of 10 %, a dynamic strain of 2 %, and a temperature of 70 degrees C, satisfy the following expressions (1) and (2): 50 [0009] In another aspect of the present invention, the rubber compound is characterized in that, 55 of vulcanized rubber’s physical properties, a complex elastic modulus E* 30 (unit: MPa) under the initial strain of 10 %, the dynamic strain of 2 %, and the temperature of 30 degrees c, and 2 EP 3 196 048 A1 a complex elastic modulus E* 100 (unit: MPa) under the initial strain of 10 %, the dynamic strain of 2 %, and the temperature of 100 degrees c can satisfy a following expression (3): 5 [0010] In another aspect of the present invention, the rubber compound is characterized in that, of vulcanized rubber’s physical properties, 10 a breaking elongation EBx in an X-axis direction which is a rubber extruded direction, a breaking elongation EBY in a Y-axis direction orthogonal to the X-axis direction, and a breaking elongation EBZ in a z-axis direction orthogonal to the X-axis direction and the Y-axis direction can satisfy following expressions (4) and (5): 15 20 [0011] In another aspect of the present invention, the rubber compound is characterized in that, of vulcanized rubber’s properties, a breaking strength TBX in the X-axis direction which is the rubber extruded direction, a breaking strength TBY in the Y-axis direction perpendicular to the X-axis direction, and 25 a breaking strength TBZ in the Z-axis direction perpendicular to the X-axis direction and the Y-axis direction can satisfy following expressions (6) and (7): 30 [0012] In another aspect of the present invention, the rubber compound for tires is characterized in that, 35 of vulcanized rubber’s physical properties, a volume resistivity value may be less than 1 x 10^8 ohm cm. [0013] In another aspect of the present invention, a pneumatic tire is provided which comprises a rubber member made of the rubber compound for tires as set forth in any one of claims 1-5. [0014] In another aspect of the present invention, an airless tire is provided which comprises a rubber member made of the rubber compound for tires as set forth in any one of claims 1-5. 40 [0015] Another aspect of the present invention is an airless tire comprising a cylindrical tread ring provided with a ground contacting surface, a hub disposed radially inside the tread ring and fixed to a vehicle axle, and a spoke connecting the tread ring and the hub, characterized in that, the tread ring comprises 45 a tread rubber forming the ground contacting surface, an outer reinforcing cord layer disposed closest to the tread rubber, an inner reinforcing cord layer disposed radially inside the outer reinforcing cord layer, and a shearing rubber layer disposed between the outer reinforcing cord layer and the inner reinforcing cord layer, the shearing rubber layer has a complex elastic modulus E* (unit: MPa) and a loss tangent tanδ under an initial strain of 10 %, a dynamic strain 50 70 70 of 2 %, and a temperature of 70 degrees C which satisfy following expressions (1) and (2): 55 3 EP 3 196 048 A1 [0016] In another aspect of the present invention, the shearing rubber layer has a complex elastic modulus E* 30 (unit: MPa) under the initial strain of 10 %, the dynamic strain of 2 %, and the temperature of 30 degrees C, and a complex elastic modulus E* 100 (unit: MPa) under the initial strain of 10 %, the dynamic strain of 2 %, and the temperature 5 of 100 degrees C which can satisfy a following expression (3): 10 [0017] In another aspect of the present invention, the shearing rubber layer has a breaking elongation EBX in the tire circumferential direction and a breaking elongation EBY in the tire axial direction which satisfy a following expression (4), and a breaking strength TBX in the tire circumferential direction and 15 a breaking strength TBY in the tire axial direction which satisfy a following expression (5): 20 [0018] In another aspect of the present invention, the shearing rubber layer has a volume resistivity which may be less than 1 x 10^8 ohm cm. 25 [0019] In another aspect of the present invention, reinforcing cords of the outer reinforcing cord layer and reinforcing cords of the inner reinforcing cord layer may be steel cords. [0020] In another aspect of the present invention, it is possible that the outer reinforcing cord layer comprise a first cord ply including first reinforcing cords arranged to incline with respect to the tire circumferential direction, and 30 a second cord ply disposed radially outside the first cord ply and including second reinforcing cords arranged to incline with respect to the tire circumferential direction at the same angle as and to the opposite direction to the first reinforcing cords, and the inner reinforcing cord layer comprises a third cord ply including third reinforcing cords arranged in parallel with the tire circumferential direction or the tire axi al 35 direction. [0021] In another aspect of the present invention, the outer reinforcing cord layer can further comprise a fourth cord ply disposed radially outside the second cord ply and including fourth reinforcing cords.