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JP-7856199-B2 - Heavy-duty pneumatic tires

JP7856199B2JP 7856199 B2JP7856199 B2JP 7856199B2JP-7856199-B2

Inventors

  • 出雲 優

Assignees

  • 住友ゴム工業株式会社

Dates

Publication Date
20260511
Application Date
20250610

Claims (20)

  1. A heavy-duty pneumatic tire with a tread, The tread comprises a cap rubber layer constituting the tread surface and a base rubber layer adjacent to the inner side of the cap rubber layer in the tire radial direction, and the cap rubber layer and the base rubber layer are composed of a rubber composition containing rubber components and sulfur. The amount of acetone extracted from the rubber composition constituting the base rubber layer is less than 4.0% by mass. When the modulus of the rubber composition constituting the base rubber layer at 23°C and 200% stretch is M200b (MPa), and the modulus of the rubber composition constituting the cap rubber layer at 23°C and 200% stretch is M200c (MPa), then M200b and M200c satisfy the following formula (1), 0 ≤ M200c - M200b ≤ 4 ... (1) A heavy-duty pneumatic tire wherein, when the breaking strength at 23°C of the rubber composition constituting the base rubber layer is TB (MPa) and the elongation at 23°C is EB (%), the tanδ (70°C tanδ), TB, and EB of the rubber composition constituting the base rubber layer satisfy the following formula (2) . TB × EB / 70°C tanδ ≥ 4.5 × 10⁵ ... (2)
  2. A heavy-duty pneumatic tire with a tread, The tread comprises a cap rubber layer constituting the tread surface and a base rubber layer adjacent to the inner side of the cap rubber layer in the tire radial direction, and the cap rubber layer and the base rubber layer are composed of a rubber composition containing rubber components and sulfur. The amount of acetone extracted from the rubber composition constituting the base rubber layer is less than 4.0% by mass. When the modulus of the rubber composition constituting the base rubber layer at 23°C and 200% stretch is M200b (MPa), and the modulus of the rubber composition constituting the cap rubber layer at 23°C and 200% stretch is M200c (MPa), then M200b and M200c satisfy the following formula (1), 0 ≤ M200c - M200b ≤ 4 ... (1) A heavy-duty pneumatic tire in which the modulus M200b of the rubber composition constituting the base rubber layer is 13.0 MPa or less when stretched to 200% .
  3. A heavy-duty pneumatic tire with a tread, The tread comprises a cap rubber layer constituting the tread surface and a base rubber layer adjacent to the inner side of the cap rubber layer in the tire radial direction, and the cap rubber layer and the base rubber layer are composed of a rubber composition containing rubber components and sulfur. The amount of acetone extracted from the rubber composition constituting the base rubber layer is less than 4.0% by mass. When the modulus of the rubber composition constituting the base rubber layer at 23°C and 200% stretch is M200b (MPa), and the modulus of the rubber composition constituting the cap rubber layer at 23°C and 200% stretch is M200c (MPa), then M200b and M200c satisfy the following formula (1), 0 ≤ M200c - M200b ≤ 4 ... (1) A heavy-duty pneumatic tire in which the butadiene rubber content in the rubber component of the rubber composition constituting the base rubber layer is 28% by mass or less .
  4. A heavy-duty pneumatic tire with a tread, The tread comprises a cap rubber layer constituting the tread surface and a base rubber layer adjacent to the inner side of the cap rubber layer in the tire radial direction, and the cap rubber layer and the base rubber layer are composed of a rubber composition containing rubber components and sulfur. The amount of acetone extracted from the rubber composition constituting the base rubber layer is less than 4.0% by mass. When the modulus of the rubber composition constituting the base rubber layer at 23°C and 200% stretch is M200b (MPa), and the modulus of the rubber composition constituting the cap rubber layer at 23°C and 200% stretch is M200c (MPa), then M200b and M200c satisfy the following formula (1), 0 ≤ M200c - M200b ≤ 4 ... (1) A heavy-duty pneumatic tire in which the oil content of the rubber composition constituting the base rubber layer is 4 parts by mass or less per 100 parts by mass of rubber component .
  5. A heavy-duty pneumatic tire according to any one of claims 1 to 4 , satisfying that the maximum value of M200c - M200b in formula (1) above is 3 or less.
  6. A heavy-duty pneumatic tire with a tread, The tread comprises a cap rubber layer constituting the tread surface and a base rubber layer adjacent to the inner side of the cap rubber layer in the tire radial direction, and the cap rubber layer and the base rubber layer are composed of a rubber composition containing rubber components and sulfur. The amount of acetone extracted from the rubber composition constituting the base rubber layer is less than 3.9% by mass. When the modulus of the rubber composition constituting the base rubber layer at 23°C and 200% stretch is M200b (MPa), and the modulus of the rubber composition constituting the cap rubber layer at 23°C and 200% stretch is M200c (MPa), then M200b and M200c satisfy the following formula (1), 0 ≤ M200c - M200b ≤ 5 ... (1') A heavy-duty pneumatic tire wherein, when the breaking strength at 23°C of the rubber composition constituting the base rubber layer is TB (MPa) and the elongation at 23°C is EB (%), the tanδ (70°C tanδ), TB, and EB of the rubber composition constituting the base rubber layer satisfy the following formula (2). TB × EB / 70°C tanδ ≥ 4.5 × 10⁵ ... (2)
  7. The heavy-duty pneumatic tire according to any one of claims 1 to 5, wherein the amount of acetone extracted from the rubber composition of the base rubber layer is less than 3.9% by mass.
  8. The heavy-duty pneumatic tire according to claim 6 or 7 , wherein the amount of acetone extracted from the rubber composition of the base rubber layer is less than 3.8% by mass.
  9. The heavy-duty pneumatic tire according to claim 8 , wherein the amount of acetone extracted from the rubber composition of the base rubber layer is less than 3.7% by mass.
  10. The heavy-duty pneumatic tire according to claim 9 , wherein the amount of acetone extracted from the rubber composition of the base rubber layer is less than 3.6% by mass.
  11. A heavy-duty pneumatic tire according to any one of claims 1 to 10 , wherein the tanδ (70°C tanδ) of the rubber composition constituting the base rubber layer is less than 0.040.
  12. The heavy-duty pneumatic tire according to claim 11 , wherein the tanδ (70°C tanδ) of the rubber composition constituting the base rubber layer is less than 0.039.
  13. The heavy-duty pneumatic tire according to claim 12 , wherein the tanδ (70°C tanδ) of the rubber composition constituting the base rubber layer is less than 0.038.
  14. The heavy-duty pneumatic tire according to claim 13 , wherein the tanδ (70°C tanδ) of the rubber composition constituting the base rubber layer is less than 0.037.
  15. A heavy-duty pneumatic tire according to any one of claims 2 to 5, wherein when the breaking strength at 23°C of the rubber composition constituting the base rubber layer is TB (MPa) and the elongation at 23°C is EB (%), the tanδ (70°C tanδ), TB, and EB of the rubber composition constituting the base rubber layer satisfy the following formula ( 2 ) . TB × EB / 70°C tanδ ≥ 4.5 × 10⁵ ... (2)
  16. A heavy-duty pneumatic tire according to claim 6 or 15, satisfying that the minimum value of TB × EB / 70°C tanδ in formula (2) above is 4.6 × 10⁵ or greater.
  17. A heavy-duty pneumatic tire according to claim 6 or 16 , wherein the minimum value of TB × EB / 70°C tanδ in formula (2) above is 4.7 × 10⁵ or greater.
  18. A heavy-duty pneumatic tire according to claim 6 or 17 , wherein the minimum value of TB × EB / 70°C tanδ in formula (2) above is 4.8 × 10⁵ or greater.
  19. A heavy-duty pneumatic tire according to claim 6 or 18 , satisfying that the minimum value of TB × EB / 70°C tanδ in formula (2) above is 4.9 × 10⁵ or greater.
  20. The heavy-duty pneumatic tire according to any one of claims 1 to 19 , wherein the rubber composition constituting the base rubber layer contains 5 parts by mass or more of silica per 100 parts by mass of rubber components.

Description

This invention relates to a pneumatic tire for heavy loads. A known technique for improving the fracture strength of truck and bus tires involves micronizing or highly structuring carbon black (for example, Patent Document 1). Japanese Patent Application Publication No. 6-279624 This is a cross-sectional view in the tread width direction showing half of the tread portion of the heavy-duty pneumatic tire of this disclosure.This is a schematic front view showing an example of a test apparatus used in this disclosure to evaluate the rib tear resistance of a heavy-duty pneumatic tire.This is a plan view of the protruding fixture and reference surface of the testing apparatus.This is a magnified view of the main parts of the test apparatus. The heavy-duty pneumatic tire according to this disclosure is a heavy-duty pneumatic tire having a tread, wherein the tread has a cap rubber layer constituting the tread surface and a base rubber layer adjacent to the radially inward side of the cap rubber layer, the cap rubber layer and the base rubber layer are composed of a rubber composition containing rubber components, the amount of acetone extracted from the rubber composition constituting the base rubber layer is less than 4.0% by mass, and when the modulus of the rubber composition constituting the base rubber layer at 23°C and 200% stretch is M200b (MPa), and the modulus of the rubber composition constituting the cap rubber layer at 23°C and 200% stretch is M200c (MPa), M200b and M200c satisfy the following formula (1). 0 ≤ M200c - M200b ≤ 5 ... (1) While we do not intend to be bound by theory, the following are some possible mechanisms by which the effects of this disclosure are realized. Poor modulus balance between the base rubber layer and the cap rubber layer can lead to tread damage, such as delamination at the interface between the cap rubber layer and the base rubber layer, or cracks within the base tread rubber. Therefore, by setting the difference in modulus between the base rubber layer and the cap rubber layer at 200% stretch within a predetermined range, and by setting the amount of acetone extracted from the base rubber layer within a predetermined range, it is believed that the modulus balance between the base rubber layer and the cap rubber layer was optimized, thereby suppressing heat generation in the tread rubber while improving rib tear resistance. Furthermore, it is believed that the combination of the structure of the reinforcing rubber layer (described later) and the aforementioned physical properties of the rubber composition constituting each layer of the tread resulted in improved fuel efficiency and rib tear resistance. The tanδ (70°C tanδ) of the rubber composition constituting the base rubber layer is preferably less than 0.040. When the breaking strength at 23°C of the rubber composition constituting the base rubber layer is denoted as TB (MPa) and the elongation at 23°C as EB (%), it is preferable that the tanδ (70°C tanδ), TB, and EB of the rubber composition constituting the base rubber layer at 70°C satisfy the following formula (2). TB × EB / 70°C tanδ ≥ 4.5 × 10⁵ ... (2) The rubber component constituting the base rubber layer preferably contains butadiene rubber. The thickness of the base rubber layer is preferably 1 to 70% of the total thickness of the tread. The heavy-duty pneumatic tire according to this disclosure comprises four or more belt layers on the radially inward side of the base rubber layer, and preferably, at least one of the radially outer surfaces of the outermost belt layer and the widest belt layer is covered with a reinforcing rubber layer that terminates without reaching the tire equator, and preferably, the tanδ (70°C tanδ) value of the rubber composition constituting the reinforcing rubber layer at 70°C is greater than the tanδ (70°C tanδ) value of the rubber composition constituting the base rubber layer at 70°C. The width w of the reinforcing rubber layer is preferably 10 to 40% of the tread width W of the tread. The maximum thickness of the reinforcing rubber layer is preferably 5 to 25% of the groove depth of the widthwise groove located at a position 1/4 of the tread width from the tire equator. The rubber composition constituting the base rubber layer preferably contains a glycerin fatty acid ester. A heavy-duty pneumatic tire containing a tread rubber composition, which is one embodiment of this disclosure, will be described in detail below. However, the following description is illustrative for illustrating this disclosure and is not intended to limit the technical scope of the present invention to this scope only. In this specification, when numerical ranges are indicated using "~", the values at both ends of the range are included. <Heavy-duty pneumatic tires> Figure 1 shows a cross-sectional view in the tread width direction of half of the tread portion of the heavy-duty pneumatic tire of the present disclosure, but the present disclosure is not l