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JP-7857503-B2 - Tread bands for pneumatic tires and tires containing them

JP7857503B2JP 7857503 B2JP7857503 B2JP 7857503B2JP-7857503-B2

Inventors

  • コトゥーニョ、サルヴァトーレ
  • フレッシュ、エンリコ
  • アンジェロサント、セシリア
  • アルノーネ、ジュゼッペ
  • デル ドゥーカ、マルコ
  • ティローネ、アントニオ

Assignees

  • ブリヂストン ヨーロッパ エヌブイ／エスエイ

Dates

Publication Date
20260512
Application Date
20221222

Claims (18)

  1. A tread band for a tire suitable for engaging with the road surface in the footprint area, Two shoulder regions at the axial outer end of the tread band, A central region is identified between the shoulder region, In each of the shoulder regions, a row of shoulder elements is arranged along the first circumferential rib, In the aforementioned central region, at least two rows of central elements are arranged along the second circumferential rib, It comprises at least three circumferential grooves that separate the first circumferential rib and the second circumferential rib from other circumferential ribs, The central elements are separated along their entire axial width by transverse sipes, and the transverse sipes define two endpoints at their respective axial outer ends where they intersect the circumferential grooves. The E treadband is (i) A first hydrocarbon polymer additive which is a partially hydrogenated C5 resin containing less than 100% and 5% or more olefin protons, (ii) A tread band (2) further comprising a second hydrocarbon polymer additive, the second hydrocarbon polymer additive being a fully hydrogenated resin, wherein the fully hydrogenated resin contains less than 5% olefin protons and is selected from the group consisting of hydrogenated C5 resins, hydrogenated C5 / C9 copolymer resins, hydrogenated C9 resins, and combinations thereof.
  2. The tread band according to claim 1, wherein the first hydrocarbon polymer additive is a partially hydrogenated C5 resin, and the second hydrocarbon polymer additive is a fully hydrogenated C9 resin.
  3. The tread band according to claim 1 or 2, wherein the first hydrocarbon polymer additive is a partially hydrogenated C5 and dicyclopentadiene (DCPD) copolymer.
  4. The first hydrocarbon polymer additive has the following characteristics, namely, Olefin proton content of less than 10 mol%, Softening point of 110°C or higher, Weight-average molecular weight of 200 g/mol to 2000 g/mol, and/or The tread band according to claim 1, which is a partially hydrogenated C5 resin having one or more glass transition temperatures ( Tg ) of 50°C or higher.
  5. The tread band according to claim 1, wherein the second hydrocarbon polymer additive is a fully hydrogenated C9 resin.
  6. The aforementioned hydrogenated C9 resin has the following characteristics, namely, Softening point is 100°C or higher, Weight-average molecular weight (Mw) of 700 g/mol to 1500 g/mol, and/or The tread band according to claim 1, having one or more of the following glass transition temperatures ( Tg ) of at least 50°C.
  7. The tread band according to claim 1, wherein the ratio of the amount of the first hydrocarbon polymer additive to the amount of the second hydrocarbon polymer additive is 10:1 to 1:10.
  8. The tread band according to claim 1, wherein the imaginary straight extension between the two endpoints defines the inclination angle of the transverse sipe with respect to the axial direction of the tire, the absolute value of which is in the range of 25° to 50°.
  9. The tread band according to claim 8, wherein the extension along the axial direction between the two endpoints of the transverse sipe is substantially S-shaped.
  10. The tread band according to claim 1, wherein each endpoint of the transverse sipes in each row of the central element has a circumferential offset with respect to the endpoint closest to the circumferential direction of each transverse sipe in one or more adjacent rows.
  11. The tread band according to claim 1, wherein the transverse sipe has a radial extension on the inside of the tread band along the radial profile, and the radial profile becomes wavy or zigzag in shape as the transverse sipe extends in the axial direction.
  12. The tread band according to claim 1, further comprising a first elastomer component containing one or more styrene-butadiene copolymers.
  13. The tread band according to claim 1, further comprising a second elastomer component containing natural rubber.
  14. The tread band according to claim 1, wherein the tread band comprises a first silica functionalized with one or more carboxyl groups.
  15. The tread band according to claim 14, wherein the first silica has a CTAB specific surface area of 230 m² /g to 285 m² /g.
  16. The tread band according to claim 1, wherein the tread band contains a second silica.
  17. The E treadband is A first styrene-butadiene copolymer functionalized with terminal carboxyl groups, having a styrene content of 21% to 24% by weight of the first styrene-butadiene copolymer and present in an amount of 50 phr to 65 phr, A second styrene-butadiene copolymer having a styrene content of 32% to 42% by weight of the second styrene-butadiene copolymer and present in an amount of 20 phr to 30 phr, A quantity of natural rubber ranging from 10 phr to 30 phr, A first silica having a surface functionalized with one or more carboxyl groups present in an amount of 60 phr to 70 phr, and having a CTAB specific surface area of 240 m² /g to 270 m² /g and/or a BET surface area of 270 m² /g to 300 m² /g, The tread band according to claim 1, comprising a second silica having a CTAB specific surface area of 65 m² /g to 95 m² / g and/or a BET surface area of 70 m² /g to 110 m² /g, and present in an amount of 10 phr to 20 phr.
  18. A pneumatic tire comprising the tread band described in claim 1.

Description

This invention relates to a tread band for a pneumatic tire and a tire comprising the same, wherein the tread band comprises a first hydrocarbon polymer resin additive and a second hydrocarbon polymer resin additive, which, in combination with the presence of transverse sipes in the tread band, have a beneficial and/or synergistic effect on the wet performance, rolling resistance, and wear resistance of the tire comprising the tread band. To reduce CO2 emissions, there is a demand for vehicles with lower fuel consumption, which can be achieved by reducing the rolling resistance of the vehicle's tires. It is also important that the tires have good grip performance, especially on wet surfaces (i.e., wet performance). High wear resistance is also a crucial factor for a tire's long service life. Wet performance ("WET"), rolling resistance ("RR"), and wear resistance ("WEAR") together are known as the "magic triangle" of viscoelastic properties. There is an ongoing need to manufacture tires with an improved balance between these properties. The chemical composition of tires can be modified to adjust their dynamic/mechanical properties. In attempts to achieve a better WET/RR/WEAR balance, the use of modified rubber, mixtures of rubber and various reinforcing fillers, has been proposed. However, improving any one of these tire properties often negatively impacts at least one of the others. For example, it is difficult to improve a tire's wet performance without negatively affecting its rolling resistance and wear resistance. Similarly, increasing the amount of reinforcing filler leads to improved wear performance, which in turn reduces rolling resistance. Hydrocarbon resins are widely used as processing aids to modify the viscoelastic properties of rubber compositions and thus improve tire tread performance characteristics, such as wet grip and rolling resistance. A wide range of hydrocarbon resins are known for use in the manufacture of rubber compositions for tire treads, including aliphatic resins, aromatic resins, partially hydrogenated resins, and fully hydrogenated resins. Combinations of different hydrocarbon resins have been proposed. For example, U.S. Patent Application Publication No. 2019/0092937 proposes a blend of a C5 aliphatic resin with a dicyclopentadiene DCPD resin or an aromatic pure monomer resin to adjust the material properties of an immiscible blend of natural rubber and high cis polybutadiene rubber. The physical morphology of the tire tread, particularly the size and shape of the portion that contacts the road surface (contact patch), also affects its performance. Generally, tire treads are cut to form tread elements. Circumferential grooves in the tread can improve drainage (and thus affect wet performance), while lateral grooves can improve traction and wear resistance. Sipes are small grooves cut laterally across larger tread elements and are known to improve traction in wet conditions and reduce wear. There remains a need in the art for tire treads where chemical composition and physical morphology are optimized in parallel to improve tire performance. The present invention aims to satisfy unmet requirements in the art and solve problems related to existing tires. This invention is based on the discovery that optimizing the chemical composition and physical morphology of a tread band can have beneficial and/or synergistic effects on the properties of tires prepared from that tread band. Therefore, this invention provides a tread band comprising a first hydrocarbon polymer resin and a second hydrocarbon polymer resin, and having transverse sipes, which together improve tire performance compared to tires prepared without the sipes or without the hydrocarbon polymer resins of this invention. In a first aspect, the present invention relates to a tread band for a tire suitable for engaging with the road surface in a footprint area, Two shoulder regions at the axial outer end of the tread band, A central region is identified between the shoulder regions, A row of shoulder elements arranged along the first circumferential rib in each of the shoulder regions, At least two rows of central elements arranged along the second circumferential rib in the central region, It comprises at least three circumferential grooves that separate a first circumferential rib and a second circumferential rib from other circumferential ribs, The central element is separated along its entire axial width by transverse sipes, which define two endpoints at their respective axial outer ends where they intersect with the circumferential grooves. The treadbands are (i) A first hydrocarbon polymer additive which is a partially hydrogenated C5 resin, (ii) A tread band further comprising a second hydrocarbon polymer additive which is a fully hydrogenated resin selected from the group consisting of hydrogenated C5 resin, hydrogenated C5 / C9 copolymer resin, hydrogenated C9 resin, and combinations thereof. In a second aspect