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EP-4737515-A1 - RUBBER COMPOSITION FOR TIRES, AND TIRE

EP4737515A1EP 4737515 A1EP4737515 A1EP 4737515A1EP-4737515-A1

Abstract

The object is to provide a rubber composition for a tire capable of achieving a good balance between processability and both high fuel efficiency and wear resistance when adopted in a tire, and the solution is a rubber composition for a tire containing a rubber component and carbon black having a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of 50 m 2 /g to 125 m 2 /g, wherein the rubber component includes a copolymer of cyclopentene and a norbornene compound represented by the following general formula (1): (in the formula, R 1 to R 4 each independently represent a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a substituent containing a halogen atom, a silicon atom, an oxygen atom, or a nitrogen atom, R 2 and R 3 may be bonded to each other to form a ring, and m is an integer of 0 to 2) and butadiene rubber.

Inventors

  • FUKASAWA Rira
  • TARUTANI Yasunori
  • NISHIMURA SYUNSUKE

Assignees

  • BRIDGESTONE CORPORATION

Dates

Publication Date
20260506
Application Date
20231207

Claims (9)

  1. A rubber composition for a tire comprising a rubber component and carbon black having a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of not less than 50 m 2 /g and not more than 125 m 2 /g, wherein the rubber component includes: a copolymer of cyclopentene and a norbornene compound represented by general formula (1), shown below: where, in general formula (1), R 1 to R 4 each independently represent a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a substituent containing a halogen atom, a silicon atom, an oxygen atom, or a nitrogen atom, R 2 and R 3 may be bonded to each other to form a ring, and m is an integer of 0 to 2; and butadiene rubber.
  2. The rubber composition for a tire according to claim 1, wherein the norbornene compound represented by general formula (1) is 2-norbornene and/or dicyclopentadiene.
  3. The rubber composition for a tire according to claim 1, wherein content of the copolymer of cyclopentene and the norbornene compound is 20 parts by mass to 90 parts by mass per 100 parts by mass of the rubber component.
  4. The rubber composition for a tire according to claim 1, wherein the copolymer of cyclopentene and the norbornene compound has a weight-average molecular weight (Mw) of 200,000 to 1,000,000.
  5. The rubber composition for a tire according to claim 1, wherein the copolymer of cyclopentene and the norbornene compound has a content ratio of structural units derived from cyclopentene of 20% by mass to 75% by mass.
  6. The rubber composition for a tire according to claim 2, wherein the copolymer of cyclopentene and the norbornene compound has a content ratio of structural units derived from 2-norbornene of 10% by mass to 60% by mass.
  7. The rubber composition for a tire according to claim 2, wherein the copolymer of cyclopentene and the norbornene compound has a content ratio of structural units derived from dicyclopentadiene of 10% by mass to 60% by mass.
  8. The rubber composition for a tire according to claim 1, wherein content of the carbon black is 5 parts by mass to 80 parts by mass per 100 parts by mass of the rubber component.
  9. A tire comprising the rubber composition for a tire according to claim 1.

Description

TECHNICAL FIELD The present disclosure relates to a rubber composition for a tire and a tire. BACKGROUND In connection with the recent global movement toward carbon dioxide emission regulations due to increasing concern over environmental issues, there is a growing demand for improved fuel efficiency in automobiles. To meet such demands, tire performance is also required to be improved in terms of high fuel efficiency (that is, reduction of rolling resistance). In addition, from the viewpoint of tire economy, in the development of rubber compositions for tires, it is also required to improve wear resistance in addition to high fuel efficiency. However, in general, high fuel efficiency and wear resistance are in a trade-off relationship, and it is difficult to achieve both. For example, a method of increasing the amount of filler blended to improve wear resistance is known, but increasing the amount of filler blended leads to deterioration in the dispersion state of the filler, resulting in a problem of deteriorated high fuel efficiency, and furthermore, causes a problem in which the unvulcanized viscosity of the rubber composition increases, thereby deteriorating processability. Thus, in general, it is difficult to achieve a good balance among high fuel efficiency, wear resistance, and processability. In response, PTL 1 and PTL 2 below disclose rubber compositions for passenger vehicle tires and rubber compositions for heavy-duty truck and bus tires, which contain specific long-chain branched cyclopentene ring-opening rubber (LCB-CPR), and these rubber compositions are said to be effective in reducing rolling resistance of tires, improving wet skid resistance, and improving wear resistance. CITATION LIST Patent Literature PTL 1: WO 2021/178233 A1PTL 2: WO 2021/178235 A1 SUMMARY (Technical Problem) However, as a result of investigations by the present inventors, it was found that even with the techniques described in PTL 1 and PTL 2 above, it is difficult to achieve a good balance between the processability of the rubber composition and both the high fuel efficiency and wear resistance of a tire to which the rubber composition is applied, and there remains room for improvement. Accordingly, the present disclosure has as its object to solve the above problems of the prior art and to provide a rubber composition for a tire capable of achieving a good balance between processability and both high fuel efficiency and wear resistance when applied to a tire. Further, the present disclosure has as a further object to provide a tire in which high fuel efficiency, wear resistance, and productivity are well balanced. (Solution to Problem) The essential configuration of the rubber composition for a tire and the tire of the present disclosure for solving the above problems is as follows. [1] A rubber composition for a tire comprising a rubber component and carbon black having a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of not less than 50 m2/g and not more than 125 m2/g, wherein the rubber component includes:a copolymer of cyclopentene and a norbornene compound represented by general formula (1), shown below: where, in general formula (1), R1 to R4 each independently represent a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a substituent containing a halogen atom, a silicon atom, an oxygen atom, or a nitrogen atom, R2 and R3 may be bonded to each other to form a ring, and m is an integer of 0 to 2; andbutadiene rubber.[2] The rubber composition for a tire according to [1], wherein the norbornene compound represented by general formula (1) is 2-norbornene and/or dicyclopentadiene.[3] The rubber composition for a tire according to [1] or [2], wherein the content of the copolymer of cyclopentene and the norbornene compound is 20 parts by mass to 90 parts by mass per 100 parts by mass of the rubber component.[4] The rubber composition for a tire according to any one of [1] to [3], wherein the copolymer of cyclopentene and the norbornene compound has a weight-average molecular weight (Mw) of 200,000 to 1,000,000.[5] The rubber composition for a tire according to any one of [1] to [4], wherein the copolymer of cyclopentene and the norbornene compound has a content ratio of structural units derived from cyclopentene of 20% by mass to 75% by mass.[6] The rubber composition for a tire according to any one of [2] to [5], wherein the copolymer of cyclopentene and the norbornene compound has a content ratio of structural units derived from 2-norbornene of 10% by mass to 60% by mass.[7] The rubber composition for a tire according to any one of [2] to [6], wherein the copolymer of cyclopentene and the norbornene compound has a content ratio of structural units derived from dicyclopentadiene of 10% by mass to 60% by mass.[8] The rubber composition for a tire according to any one of [1] to [7], wherein the content of the carbon black is 5 parts by mass to 80 parts by mass per 100 parts