RUBBER COMPOSITION AND A TIRE

Abstract

The present invention is directed to a rubber composition comprising 30 to 100 phr of at least one styrene-butadiene rubber; 0 to 70 phr of at least one further diene-based elastomer; 100 to 200 phr of silica; at least 30 phr of a hydrocarbon resin; and at least 0.1 phr of one or more of amino fatty acids and fatty acid amides. Moreover, the present invention is directed to a tire comprising such a rubber composition.

Claims

1. A rubber composition comprising: 30 to 100 phr of at least one styrene-butadiene rubber; 0 to 70 phr of at least one additional diene-based elastomer; 100 to 200 phr of silica; at least 30 phr of a hydrocarbon resin; and at least 0.1 phr of at least one member selected from the group consisting of amino fatty acids and fatty acid amides.

2. The rubber composition according to claim 1, wherein the styrene-butadiene rubber is functionalized for coupling to silica.

3. The rubber composition according to claim 1, wherein the rubber composition comprises from 30 to 75 phr of the styrene-butadiene rubber and from 25 to 70 phr of the at least one additional diene-based elastomer selected from the group consisting of polybutadiene rubber, synthetic polyisoprene rubber and natural rubber.

4. The rubber composition according to claim 1, wherein the silica is present at a level which is within the range of 140 phr to 200 phr.

5. The rubber composition according to claim 1, wherein the rubber composition comprises a total of from 0.2 phr to 10 phr of said one or more of amino fatty acids and fatty acid amides.

6. The rubber composition according to claim 1, wherein the styrene-butadiene rubber has a glass transition temperature within a range of −50° C. to −86° C.

7. The rubber composition according to claim 1, wherein the additional diene based elastomer is a polybutadiene rubber having a glass transition temperature within a range of −90° C. to −115° C.

8. The rubber composition according to claim 1, wherein the hydrocarbon resin is solid at 23° C.

9. The rubber composition according to claim 1, wherein the hydrocarbon resin is one or more members selected from the group consisting of aliphatic (C5) resins, aromatic (C9) resins, cyclopentadiene resins, dicyclopentadiene resins, coumarone indene resins, terpene resins, alpha methyl styrene resins, and terpene phenol resins.

10. The rubber composition according to claim 1, wherein the hydrocarbon resin has a glass transition temperature within a range of 35° C. to 90° C.

11. The rubber composition according to claim 1, wherein the rubber composition further comprises 5 to 30 phr of a liquid plasticizer.

12. The rubber composition according to claim 11, wherein the liquid plasticizer is chosen from one or more of oil and liquid polymer.

13. The rubber composition according to claim 12, wherein the ratio of the hydrocarbon resin to liquid plasticizers is at least 2:1.

14. The rubber composition according to claim 12, wherein the rubber composition comprises at least 5 phr of a vegetable oil having a glass transition temperature within a range of −75° C. to −90° C.

15. The rubber composition according to claim 1, wherein the hydrocarbon resin has a weight average molecular weight within a range of 500 g/mol to 1600 g/mol.

16. The rubber composition according to claim 1, wherein the rubber composition comprises a plasticizer composition comprising (i) the one or more of amino fatty acids and fatty acid amides and (ii) fatty acids, and wherein said plasticizer composition has one of: an acid number within a range of 50 to 200 mg KOH/g, an acid number within a range of 90 to 200 mg KOH/g, and a dropping point within the range of 50° C. to 100° C.

17. The rubber composition according to claim 1, wherein the amino fatty acids are based on the reaction of fatty acids with amino acids.

18. The rubber composition according to claim 17, wherein the amino acids are selected from the group consisting of glycine, alanine, valine, leucine, isoleucine, and proline; wherein the fatty acids are selected from the group consisting of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid and cerotic acid; and wherein the fatty acid amides are based on the reaction of fatty acids with amines.

19. A tire comprising the rubber composition according to claim 1.

20. The tire according to claim 19, wherein the tire is one or more of a winter tire, an all-season tire, and a tire having a three peak mountain snow flake (3PMSF) symbol on its sidewall.

Description

DETAILED DESCRIPTION THE EMBODIMENTS

[0067] In order to demonstrate the technical effects of an embodiment of the present invention, two different rubber compositions have been prepared. Both compositions comprise a SSBR which has been functionalized for the coupling to silica and a polybutadiene. The Inventive Example comprises a composition comprising amino fatty acids and fatty acid amides, whereas the Comparative Example does not comprise such a composition. While the Comparative Example is mentioned herein to demonstrate the effects of the provision of amino fatty acids or fatty acid amides in a rubber composition, it is not necessarily deemed state of the art. As shown in the compositions according to Table 1, preferably the rubber matrix does not comprise only one diene-based elastomer, such as a SSBR. The resin used in both compositions of Table 1 is a plasticizing DCPD resin. In particular, the compositions comprise herein relatively high amounts of resin (amongst others for traction and plasticizing purposes). Oil, especially vegetable oil, is also present but in a far lower amount than the plasticizing resin. With regard to fillers, both compounds comprise only a small amount of carbon black and a relatively high amount of silica of 140 phr. In further inventive examples of the inventors, the silica amount was even higher such as 150 phr, 155 phr, 160 phr or even 165 phr. The positive effect of the invention is also present for such higher silica amounts. The remaining ingredients of the composition according to the Comparative Example and the Inventive Example are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Sample (amounts in phr) Ingredient Comparative Example Inventive Example SBR.sup.1 42 42 BR.sup.2 60 60 Resin.sup.3 62 62 Silica.sup.4 140 140 Rosin 3 3 Silane.sup.5 8.8 8.8 Oil.sup.6 10 10 Amino fatty acids.sup.7 0 3 Waxes 3 3 Antidegradants.sup.8 3.5 3.5 Zinc Oxide 2.5 2.5 Stearic Acid 2 2 Accelerators.sup.9 5.8 6 Sulfur donor.sup.10 2 2 Sulfur 1.25 1.25 .sup.1Solution-polymerized styrene butadiene rubber having a Tg of −60° C., a styrene content of 15 wt %, vinyl content of 26 wt %, 2 phr of extension oil, Mw of 860k g/mol, end-chain functionalized for the coupling to silica .sup.2Polybutadiene having a Tg of −108° C. as Budene 1223 of Goodyear Chemical .sup.3C9 modified and hydrogenated DCPD resin having a Tg of 56° C. as Oppera 383 from Exxon Mobil .sup.4Precipitated silica having a BET NSA of 125 m.sup.2/g .sup.5Bis-triethoxysilylpropyl-disulfide as SI 266 ™ of the company Evonik .sup.6Sunflower oil as Agripure AP-65 from Cargill .sup.7as HT257 from Schill & Seilacher .sup.8Phenylene diamines types .sup.9Diphenylguanidine and sulfenamide types .sup.10Bis-triethoxysilylpropyl tetrasulfide on a N330 carbon black carrier as X50S from Evonik

[0068] Measurements of physical properties have been carried out for the Inventive Example and the Comparative Example.

[0069] While it is known in the art that fatty acids may have a plasticizing effect to a rubber composition and may thus be used as process aids, it has surprisingly been found by the inventors that amino fatty acids and fatty acid amides have also a considerable positive effect on the tensile strength of a rubber composition.

[0070] As shown below in Table 2, the tensile strength of the Inventive Example has been increased by more than 5% by adding only a relatively small amount of amino fatty acids and fatty acid amides. At the same time elongation at break has also been improved by more than 5%. Thus, the robustness of the rubber composition has been improved, e.g. with respect to chipping and flaking behavior of the rubber compound.

[0071] At the same time the rebound value at 100° C., which can be considered as a hysteresis or rolling resistance indicator has increased (i.e. by about 3%) which is a hint for a slight improvement in rolling resistance. In other words, a higher rebound value at 100° C. indicates a reduced hysteresis and/or lower rolling resistance.

[0072] Moreover, the rebound values measured at 0° C. have decreased for the Inventive Example compared to the Comparative Example. At such low temperatures a lower rebound value can be considered as an indicator for an improved wet traction and/or wet performance of the rubber compound. Thus, as shown in Table 2, the rebound value at 0° C. was decreased by almost 5% which is an indicator of improvement of the wet performance characteristics of tires having treads made with the inventive formulation.

[0073] The abrasion of the Inventive Example could be kept at a reasonable level over the Comparative Example.

[0074] Overall, the balance of properties of the Inventive Example was improved over the balance of properties of the Comparative Example.

TABLE-US-00002 TABLE 2 Test/Property Comparative Example Inventive Example Tensile strength (MPa) .sup.a 11.9 12.5 Elongation at Break (%) .sup.a 476 503 Rebound (100° C.) .sup.b 50.8 52.5 Rebound (0° C.) .sup.b 13.4 12.8 Abrasion (%) .sup.c 100 92 .sup.a Tensile strength and elongation at break have been determined by a ring sample test based on ASTM D412 or equivalent, percentages are percentages of elongation, respectively strain; tensile strength is stress at break; elongation is elongation at break in percent. .sup.b Rebound measured on a Zwick Roell 5109 rebound resilience tester according to DIN 53512 at given temperature. .sup.c Rotary drum abrasion test according to ASTM D5963 or equivalent, wherein abrasion has been normalized to the Example and wherein higher is better than lower.

[0075] While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention.