Rubber mixture and vehicle tire

Abstract

A rubber mixture for vehicle tires which exhibits improved rolling resistance behavior and improved wear properties. The rubber mixture includes: 5 to 100 phr of at least one polymer A of the formula I): 1) F-(P-Y-P-S.sub.x).sub.z-P-Y-P-F, wherein S is sulfur, P is an elastomer polymer chain obtained by the anionic polymerization of a conjugated diene and, optionally, a vinyl aromatic compound in the presence of a diinitiator, Y is a dicarbanion group derived from the diinitiator, x is an integer greater than or equal to 1 independently for each S.sub.x group, on the condition that x is selected from the numbers 2, 3, and 4 for at least one Sx group, z is an integer from 1 to 160, each F is a terminal group independently selected from H, SH, SOH, SCl, SO.sub.2H and SO.sub.3H, and at least one filler.

Claims

1. A rubber mixture, comprising: from 5 to 100 phr of at least one polymer A of the formula I) below:
F-(P-Y-P-S.sub.x).sub.z-P-Y-P-FI) where S is a sulfur atom; P is an elastomeric polymer chain which has been obtained by anionic polymerization of at least one conjugated diene and, optionally, at least one vinylaromatic compound, in the presence of a diinitiator; Y is a dicarbanion group derived from the diinitiator; x is independently for each S.sub.x group an integer equal to or greater than 1, with the proviso that x is selected from among the numbers 2, 3, and 4 for at least one S.sub.x group; z is an integer from 1 to 160; each F is independently an end group selected from the group consisting of H, SH, SOH, SCl, SSCl, SO.sub.2H, and SO.sub.3H; and, at least one filler.

2. The rubber mixture as claimed in claim 1, wherein the at least one conjugated diene is selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene, 1,3-hexadiene, 1,3-heptadiene, 1,3-octadiene, 2-methyl-2,4-pentadiene, cyclopentadiene, 2,4-hexadiene, and 1,3-cyclooctadiene.

3. The rubber mixture as claimed in claim 2, wherein the at least one conjugated diene is 1,3-butadiene.

4. The rubber mixture as claimed in claim 1, wherein the vinylaromatic compound is selected from the group consisting of styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,4,6-trimethylstyrene, alpha-methylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, stilbene, vinylbenzyldimethylamine, 4-vinylbenzyl dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, tert-butoxystyrene, vinylpyridine, 1,2-divinylbenzene, 1,3-divinylbenzene, and 1,4-divinylbenzene.

5. The rubber mixture as claimed in claim 4, wherein the vinylaromatic compound is styrene.

6. The rubber mixture as claimed in claim 1, wherein the polymer A has the formula II) below:
F-(SBR-Y-SBR-S.sub.x).sub.z-SBR-Y-SBR-F,II) where S is a sulfur atom; SBR is an elastomeric polymer chain which has been obtained by anionic polymerization of 1,3-butadiene and styrene in the presence of a diinitiator; Y is a dicarbanion group derived from the diinitiator; x is independently for each S.sub.x group an integer equal to or greater than 1, with the proviso that x is selected from among the numbers 2, 3 and 4 for at least one S.sub.x group; z is an integer from 1 to 160; and each F is independently an end group selected from the group consisting of H, SH, SOH, SCl, SSCl, SO.sub.2H, and SO.sub.3H.

7. The rubber mixture as claimed in claim 1, wherein the diinitiator is at least one organolithium compound.

8. The rubber mixture as claimed in claim 1, wherein the polymer A has a sulfur content of from 0.1 to 30 g per kg of polymer.

9. The rubber mixture as claimed in claim 1, wherein the filler is at least one silica and/or at least one carbon black.

10. A vehicle tire, comprising at least one rubber mixture as claimed in claim 1 in at least one component of the vehicle tire.

Description

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

(1) The disclosure will now be illustrated with the aid of comparative examples and working examples which are summarized in Table 1. The mixtures denoted by I are here mixtures according to the disclosure, while the mixtures denoted by C are comparative mixtures.

(2) In the case of all the examples of mixtures in the table, the amounts indicated are parts by weight based on 100 parts by weight of total rubber (phr) or on 100 parts by weight of silica (phf).

(3) The production of the mixture was carried out under conventional conditions in two stages in a laboratory tangential mixer. The rubber mixture I1 has 100 phr of the polymer A in the embodiment having the above-described formula II). In the case of the rubber mixture C1, a comparative polymer C of the formula III), which compared to the polymer A of the formula I) used by way of example has a comparable molecular weight, a comparable vinyl content and a comparable styrene content and likewise polymer sections of SBR which, however, are linked to one another via silicon atoms instead of an S.sub.x group, was used instead of a polymer of the formula I) or II). These polymer sections of the comparative polymer do not have any sulfur-vulcanizable end groups.

(4) In addition, a similar hardness (Shore A at room temperature) was set in the case of the rubber mixture I1 by adapting the amounts of sulfur and accelerator.

(5) Test specimens were produced from all mixtures by vulcanization, and materials properties typical for the rubber industry were determined using these test specimens. The following test methods were employed for the above-described tests on test specimens: Shore A hardness (unit Shore A, abbreviated as ShA) at room temperature (RT) in accordance with DIN 53 505 Rebound resilience (rebound for short) at room temperature (RT) and 70 C. in accordance with DIN 53 512 Stress values at 300% elongation (modulus 300) at room temperature (RT) in accordance with DIN 53 504 Tensile strength and elongation at break at room temperature in accordance with DIN 53 504 Abrasion at room temperature in accordance with DIN53 516 or DIN/ISO 4649 Glass transition temperature T.sub.g of the rubber mixture from loss factor tan (tangent delta) from dynamic-mechanical measurement in accordance with DIN 53 513 (temperature sweep) Maximum loss factor tan (max) from dynamic-mechanical measurement in accordance with DIN 53 513 (temperature sweep)

(6) TABLE-US-00001 TABLE 1 Constituents Unit C1 I1 Polymer A .sup.a) phr 100 Polymer C .sup.b) phr 100 Silica .sup.c) phr 95 95 TDAE phr 3.5 3.5 Aging inhibitor phr 4 4 Stearic acid phr 2.5 2.5 Zinc oxide phr 2.5 2.5 Silane phf 7.2 7.2 Accelerator DPG phr 2 2 Accelerator CBS phr 3.6 2.7 Sulfur phr 0.36 0.27 Physical properties Shore hardness at RT Shore A 64 65 Rebound resilience at RT % 14 15 Rebound resilience at 70 C. % 28 37 Diff. in the rebound resilience 14 22 (70 C.-RT) Tensile strength MPa 6 8 Elongation at break % 582 645 Modulus 300 MPa 3.5 4.0 Tan (max) 0.276 0.246 Tg from tan C. 2 5 Abrasion mm.sup.3 343 317 Substances used from Table 1: .sup.a) Polymer A: sulfur-modified SSBR of the formula II) below: II) F(SBRYSBRS.sub.x).sub.zSBRYSBRF where: T.sub.g = 16.3 C.; Mooney viscosity = 94.3 MU; vinyl content = 68.1% by weight; styrene content = 21.6% by weight; sulfur content = 1.3 g/kg of polymer; M.sub.w = 463 kg/mol; M.sub.n = 194 kg/mol; produced from: 14.35 mmol of the diinitiator 1,3-phenylenebis(3-methyl-1-(4-methyl)phenylpentylidene)bislithium of the formula II); 10.99 mmol of S.sub.2Cl.sub.2; 10.48 mol of butadiene; 1.452 mol of styrene; 7.158 mmol of TMEDA (N,N,N,N-tetramethylethane-1,2-diamine) .sup.b) Polymer C: Comparative polymer of the formula III) below where: Me = methyl group; Tg = 16.4 C.; Mooney viscosity = 32.6 MU; vinyl content = 67.5% by weight; styrene content = 21.6% by weight; sulfur content = 0 g/kg of polymer; MM = 323 kg/mol, M.sub.n = 102 kg/mol; produced from: 9.046 mmol of the diinitiator of the formula II); 6.732 mmol of Me.sub.2SiCl.sub.2; 6.559 mol of butadiene; 0.911 mol of styrene; 4.605 mmol of TMEDA; the wavy lines represent SBR copolymer units. .sup.c)Silica: ULTRASIL VN3, from Evonik

(7) As can be seen from Table 1, the rubber mixture I1 according to the disclosure displays, compared to the comparative mixture C1, a significantly higher value for the rebound resilience at 70 C. at virtually the same glass transition temperature, which is an indication of a significantly improved rolling resistance behavior of the rubber mixture of the disclosure compared to the comparative mixture C1. In addition, the rubber mixture I1 of the disclosure displays improved abrasion behavior and an increased tensile strength.

(8) At the same time, the other physical properties remain at virtually the same level. In particular, the difference in the rebound resiliences of I1 is significantly increased compared to C1, which indicates that I1 is superior in respect of the conflicting targets of rolling resistance and wet grip.

(9) The rubber mixture of the invention thus makes it possible, particularly by use in treads, to achieve a further improvement in the rolling resistance and the abrasion resistance of vehicle tires based on the prior art without the other tire properties being adversely affected.

(10) It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.