SULFUR-CROSSLINKABLE RUBBER MIXTURE, VULCANIZATE OF THE RUBBER MIXTURE, AND VEHICLE TYRE

Abstract

The invention relates to a sulfur-crosslinkable rubber mixture, to a vulcanizate thereof and to a vehicle tire. The sulfur-crosslinkable rubber mixture contains at least the following constituents: at least one diene rubber; and 10 to 300 phr of at least one silica; and 1 to 22 phf of at least one silane A having general empirical formula A-I)

(R.sup.1).sub.oSiR.sup.2(SR.sup.3).sub.qS.sub.x(R.sup.3S).sub.qR.sup.2Si(R.sup.1).sub.o; and A-I) 0.5 to 30 phf of at least one silane B having general empirical formula B-I)

(R.sup.1).sub.oSiR.sup.2(SR.sup.3).sub.uSR.sup.2Si(R.sup.1).sub.0 B-I) wherein x is an integer from 2 to 10, q is 0, 1, 2 or 3 and u is 1, 2 or 3.

Claims

1.-15. (canceled)

16. A sulfur-crosslinkable rubber mixture comprising at least the following constituents: at least one diene rubber; and 10 to 300 phr of at least one silica; and 1 to 22 phf (parts per hundred parts of filler by weight) of at least one silane A having general empirical formula A-I)
(R.sup.1).sub.oSiR.sup.2(SR.sup.3).sub.qS.sub.x(R.sup.3S).sub.qR.sup.2Si(R.sup.1).sub.o; and A-I) 0.5 to 30 phf of at least one silane B having general empirical formula B-I)
(R.sup.1).sub.oSiR.sup.2(SR.sup.3).sub.uSR.sup.2Si(R.sup.1).sub.0 B-I) wherein o may be 1 or 2 or 3; wherein the radicals R.sup.1 may be identical or different and are selected from C.sub.1-C.sub.10-alkoxy groups, C.sub.6-C.sub.20-phenoxy groups, C.sub.2-C.sub.10-cyclic dialkoxy groups, C.sub.2-C.sub.10-dialkoxy groups, C.sub.4-C.sub.10-cycloalkoxy groups, C.sub.6-C.sub.20-aryl groups, C.sub.1-C.sub.10-alkyl groups, C.sub.2-C.sub.20-alkenyl groups, C.sub.2-C.sub.20-alkynyl groups, C.sub.7-C.sub.20-aralkyl groups, halides or alkyl polyether group O(R.sup.6O).sub.rR.sup.7, wherein the radicals R.sup.6 are identical or different and are branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C.sub.1-C.sub.30-hydrocarbon group, r is an integer from 1 to 30, and the radicals R.sup.7 are unsubstituted or substituted, branched or unbranched monovalent alkyl, alkenyl, aryl or aralkyl groups, or two R.sup.1 correspond to a dialkoxy group having 2 to 10 carbon atoms wherein in that case o<3, or two or more silanes of formulae A-I) and/or B-I) may be bridged via radicals R.sup.1 or by condensation; with the proviso that in the formulae A-I) and B-I) in each (R).sub.oSi group at least one R.sup.1 is selected from the abovementioned options, wherein this R.sup.1 i) is bonded to the silicon atom via an oxygen atom or ii) is a halide; wherein the radicals R.sup.2 and R.sup.3 in each molecule and within a molecule may be identical or different and are branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C.sub.1-C.sub.30-hydrocarbon groups; and, wherein x is an integer from 2 to 10 and q is 0 or 1 or 2 or 3; and wherein u is 1 or 2 or 3.

17. The sulfur-crosslinkable rubber mixture according to claim 16, wherein q is 0 or 1.

18. The sulfur-crosslinkable rubber mixture according to claim 16, wherein u is 1.

19. The sulfur-crosslinkable rubber mixture according to claim 16, wherein R.sup.2 is an alkyl group having 2 or 3 carbon atoms.

20. The sulfur-crosslinkable rubber mixture according to claim 16, wherein R.sup.3 is an alkyl group having 4 to 8 carbon atoms.

21. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the silane A has the following structure conforming to formula A-II): ##STR00004## and, wherein x is an integer from 2 to 10.

22. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the silane A has the following structure conforming to formula A-III):
(EtO).sub.3Si(CH.sub.2).sub.3S.sub.x(CH.sub.2).sub.3Si(EtO).sub.3; and, A-III) wherein x is an integer from 2 to 10.

23. The sulfur-crosslinkable rubber mixture according to claim 16, wherein x is an integer from 2 to 4, preferably 2.

24. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the silane B has the following structure conforming to formula B-II): ##STR00005##

25. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the molar ratio of silanes A present to silanes B present is 19:81 to 81:19.

26. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the diene rubber is selected from the group consisting of natural polyisoprene (NR), synthetic polyisoprene (IR), butadiene rubber (BR), solution-polymerized stirene-butadiene rubber (SSBR) and emulsion-polymerized stirene-butadiene rubber (ESBR).

27. The sulfur-crosslinkable rubber mixture according to claim 26, wherein the sulfur-crosslinkable rubber mixture contains 5 to 30 phr of at least one natural and/or at least one synthetic polyisoprene and 25 to 80 phr of at least one stirene-butadiene rubber and 5 to 50 phr of at least one butadiene rubber.

28. A vulcanizate obtained by sulfur vulcanization of at least one rubber mixture according to claim 16.

29. A vehicle tire comprising at least one component part based upon at least one vulcanizate according to claim 28.

30. The vehicle tire according to claim 29 comprising the at least one vulcanizate in a tread of the vehicle tire.

Description

[0184] The invention will now be more particularly elucidated with the aid of comparative examples and working examples which are summarized in the following tables.

[0185] The general compositions of the rubber mixtures upon which the examples are based are summarized in table 1 under Re1, Re2 and Re3 (recipe 1, recipe 2 or recipe 3). In table 2 recipe 3 was used. In table 3 and 4 it is stated which recipe was used in the respective example. In tables 2 to 4 both the employed silane types and the silane amounts were then additionally varied to afford comparative mixtures and inventive mixtures. The comparative mixtures are labeled V and the inventive mixtures are labeled E. In the individual examples the respective silanes were premixed with one another in the respective given quantities and then added to the rubber mixture in the base mixing stage, unless stated otherwise. The reported quantities for the silanes in phf relate to 95 phr of silica.

[0186] The silane.sup.f) was produced as follows:

[0187] 6-Bis(thiopropyltriethoxysilylhexyl) disulfide is produced as per synthesis example 1 and example 1 of EP 1375504. By contrast with synthesis example 1 of EP 1375504 the intermediate is not distilled.

[0188] Analysis: (88% yield, molar ratio:

[0189] silane of formula A-II): 94% (EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6S.sub.2(CH.sub.2).sub.6S(CH.sub.2).sub.3Si(OEt).sub.3 and

[0190] silane of formula B-II): 6% (EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6S(CH.sub.2).sub.3Si(OEt).sub.3, % by weight:

[0191] silane of formula A-II): 95% by weight (EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6S.sub.2(CH.sub.2).sub.6S(CH.sub.2).sub.3Si(OEt).sub.3 and

[0192] silane of formula B-II): 5% by weight (EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6S(CH.sub.2).sub.3Si(OEt).sub.3).

[0193] The silane.sup.h) (silane of formula B-II): 1,6-bis(thiopropyltriethoxysilyl)hexane)was produced as follows:

[0194] To mercaptopropyltriethoxysilane (62.0 g; 0.260 mol; 2.10 eq) sodium methoxide (21% in EtOH; 82.3 g; 0.254 mol; 2.05 eq) is added portionwise at a rate such that a reaction temperature of 35 C. is not exceeded. Once addition is complete the mixture is heated at reflux for 2 h. The reaction mixture is then added to 1,6-dichlorohexane (19.2 g; 0.124 mol; 1.00 eq) over 1.5 hours at 80 C. Once addition is complete the mixture is heated at reflux for 3 h and then allowed to cool to room temperature. Precipitated salts are filtered off and the product is freed of solvent under reduced pressure. The product (yield: 88%, purity: >99% in .sup.13C-NMR) was obtained as a clear liquid.

[0195] Production of bis(triethoxysilylpropyl)sulfide (silane.sup.g), B*)

[0196] To a solution of chloropropyltriethoxysilane (361 g; 1.5 mol; 1.92 eq) in ethanol (360 ml) Na.sub.2S (61.5 g; 0.78 mol; 1.00 eq) was added portionwise at a rate such that a temperature of 60 C. was not exceeded. Once addition was complete the mixture was heated at reflux for 3 h before being allowed to cool to room temperature. The reaction product was freed of precipitated salts by filtration. Distillative purification (0.04 mbar; 110 C.) afforded the product (yield: 73%, purity: >99% in .sup.13C-NMR) a clear liquid.

[0197] NMR method: The molar ratios and mass fractions reported in the examples as analytical results were obtained from .sup.13C-NMR measurements with the following parameters: 100.6 MHz, 1000 Scans, solvent CDCl.sub.3, internal standard for calibration: tetramethylsilane, relaxation agent Cr(acac)3, to determine the mass fraction in the product a defined amount of dimethyl sulfone was added as internal standard and the molar ratios of the products thereto were used to calculate the mass fraction.

[0198] Mixture production was otherwise performed by the process customary in the rubber industry under typical conditions in three stages in a laboratory mixer having a volume of 300 millilitres to 3 litres by initially mixing in the first mixing stage (base mixing stage) all constituents except the vulcanization system (sulfur and vulcanization-influencing substances) at 145 to 165 C., target temperatures of 152 to 157 C., for 200 to 600 seconds. In the second stage, the mixture from stage 1 was commixed once more, i.e. a so-called remill was performed. Addition of the vulcanization system in the third stage (final mixing stage) produced the final mixture, mixing being performed at 90 C. to 120 C. for 180 to 300 seconds. All mixtures were used to produce test specimens by vulcanization after t.sub.95 (measured on a Moving Die Rheometer according to ASTM D 5289-12/ISO 6502) under pressure at 160 C. and these test specimens were used to determine material characteristics typical for the rubber industry with the test methods reported hereinbelow. [0199] Mooney viscosity (M.V.) ML 1+4 at 100 C. according to ISO 289-1 [0200] Minimum and maximum torque T.sub.min and T.sub.max and also torque difference (delta or ) from RPA (Rubber Process Analyzer) at 165 C., 1.67 Hz, 3=42%; according to ISO 6502, section 3.2 rotorless curemeter [0201] Max. S: maximum elastic stiffness and S at 95%: S at 95% crosslinking and also k30/90: crosslinking rate between 30% and 90% conversion by means of MDR (Moving Disc Rheometer) according to ISO 6502 [0202] Stress at 300% elongation (300 modulus, M300) from tensile test on bar at 23 C. according to ISO 37 [0203] Abrasion at room temperature determined with an instrument having a rotating cylinder drum, 10 N, reported volume loss according to ISO 4649 [0204] Rebound elasticity at 70 C. according to ISO 8307 (fall height 500 mm, steel ball d=19 mm, 28 g) [0205] Maximum loss factor tan delta max. (tan max.) at 60 C. from RPA (RPA 2000, Alpha Technologies), strain-sweep, 1.7 Hz, 0.28%-42% elongation [0206] Complex moduli E* at 0 C. and 60 C. and loss factor tan delta (tan ) at 60 C. according to ISO 4664-1, 16 Hz, 50 N pre-force, 25 N amplitude force, 5 min heating time, measured value recorded after 30 s test time [0207] Conditioned Shore-A hardness at 70 C. based on DIN ISO 7619-1, preconditioned 10 times with 5 MPa and subsequently tested according to ISO 868

[0208] Substances used: [0209] a) Silica: VN3, Evonik [0210] b) Other additives: anti-aging additives, anti-ozonant wax, zinc oxide, stearic acid [0211] c) DPG+CBS [0212] d) Silane variants according to e) to h), see tables 2 to 4 [0213] e) Si 266, Evonik Industries AG; contains TESPD: silane of formula A-III) comprising 75% by weight S.sub.2 (x=2) and 7% by weight S.sub.1 (x=1) (and 18% by weight x>2) in the silane mixture; [0214] f) Contains silane of formula A-II) where x=2: (EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6S.sub.2(CH.sub.2).sub.6S(CH.sub.2).sub.3Si(OEt).sub.3 (6-bis(thiopropyltriethoxysilylhexyl)disulfide), purity 94 mol % (95% by weight), remainder: silane of formula B-II), production as above [0215] g) Bis(propyltriethoxysilyl)sulfide (monosulfide): non-bonding, but not of formula B-I), therefore indicated with B*; production as above [0216] h) Silane of formula B-II) (EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6S(CH.sub.2).sub.3Si(OEt).sub.3 (1,6-bis(thiopropyltriethoxysilyl)hexane), purity >99%, production as above [0217] i) Mole fraction of non-bonding silane B-II) in silane mixture: calculated from added silanes.sup.h) and .sup.f) (i.e. taking account of silane B-II) in silane.sup.f)) [0218] j) Mole fraction of non-bonding silane B* bis(propyltriethoxysilyl)sulfide in silane mixture: calculated from added silanes.sup.h) and .sup.e) (i.e. taking account of 7% by weight of S.sub.1-silaneB* in silane.sup.e)) [0219] k) Polybutadiene: Europrene Neocis BR 40, Polimeri [0220] l) Sprintan SLR-4601, Trinseo

TABLE-US-00001 TABLE 1 Constituents Unit Re1 Re2 Re3 NR TSR phr 10 10 20 BR .sup.k) phr 18 18 44 SSBR .sup.1) phr 72 72 36 Silica .sup.a) phr 95 95 95 TDAE phr 35 50 45 Other additives .sup.b) phr 9 9 11 Silane-varied .sup.d) phf varied varied varied Accelerator .sup.c) phr 4 4 4 Sulfur phr 2 2 2

TABLE-US-00002 TABLE 2 Unit V1 E1 E2 E3 V2 Silane .sup.f) phf 10.5 10.5 10.5 10.5 Silane .sup.h) phf 2.0 5.5 8.2 8.3 Mol % of B-II) .sup.i) % 3 25 43 53 100 Physical characteristics M.V. stage 1 M.U. 47 43 35 31 54 M.V. stage 2 M.U. 41 37 31 27 46 M.V. stage 3 M.U. 32 29 26 22 34 Tmin dNm 3.8 3.6 3.1 2.7 3.9 Tmax dNm 35.9 41.9 44.5 46.9 34.0 Torque dNm 32.1 38.3 41.4 44.2 30.1 M300 MPa 5.0 5.5 6.4 6.7 3.1 Abrasion mm.sup.3 100 97 72 78 213 Rebound 70 C. % 60.6 61.8 63.1 65.7 57.5 Tan d 60 C. max. 0.205 0.195 0.179 0.167 0.250 E* 0 C. MPa 9.0 10.7 14.8 17.7 9.0 E* 60 C. MPa 6.1 6.7 7.3 8.4 5.7 Tan d 60 C. 0.142 0.134 0.119 0.116 0.169

TABLE-US-00003 TABLE 3 Unit V3 E4 E5 V4 V5 V6 V7 V8 E6 E7 Recipe Rel Rel Rel Re2 Re2 Re2 Re2 Re2 Re2 Re2 Silane .sup.e) phf 7.2 7.2 7.2 7.2 7.2 7.2 Silane .sup.f) phf 7.2 7.2 7.2 Silane .sup.g) phf 2.8 3.8 5.1 6.4 Silane .sup.h) phf 3.4 4.5 5.1 6.8 Mol % of B-II) .sup.i) % 6 41 48 39 46 Mol %of B* .sup.j) % 36 42 49 8 8 8 Physical characteristics Max T dNm 26.8 27.2 28.6 22.3 22.7 23.8 21.4 20.9 24.6 26.4 T at 95% dNm 25.6 26.0 27.3 21.3 21.6 22.7 20.6 20.0 23.5 25.1 k30/90 min.sup.1 0.18 0.35 0.34 0.30 0.30 0.28 0.26 0.20 0.33 0.31 C. hardness 70 Shore A 62 63 65 60 60 61 53 58 62 64

TABLE-US-00004 TABLE 4 Unit E8 E9 E10 V9 V10 V11 E11 E12 E13 Recipe Re2 Re2 Re2 Re2 Re2 Re2 Re2 Re2 Re2 Silane .sup.e) phf 4.3 2.9 1.4 4.3 2.9 1.4 Silane .sup.f) phf 7.5 5.5 3.0 Silane .sup.g) phf 2.6 3.8 5.1 Silane .sup.h) phf 4.0 6.5 9.5 3.4 5.1 6.8 Mol % of B-II) .sup.i) % 43 62 81 42 62 81 Mol % of B* .sup.j) % 45 63 81 8 8 8 Vulcanization characteristics k30/90 min.sup.1 0.35 0.36 0.38 0.20 0.20 0.21 0.25 0.30 0.40

[0221] As is apparent in table 2 the inventive combination of the silanes A (conforming to general formula A-I) and B (conforming to general formula B-I) in the inventive examples E2 to E4 achieved improved rolling resistance indicators (low loss factors tan delta at 60 C. and increased rebound elasticities at 70 C.), improved abrasion behaviour (lower volume loss in DIN abrasion), reduced Mooney viscosities, increased complex moduli E* and increased stiffnesses (M300) compared to the comparative examples.

[0222] As is apparent in table 3 the inventive combination of the silanes A (silanes A-II) and A-III) conforming to general formula A-I) and B (silane B-II) conforming to general formula B-I) achieved an increased torque T.sub.95 and an increased maximum torque Max T compared to the comparative examples. As is apparent from the data from the MDR measurements the rubber mixtures according to the invention have a more stable network. The effect with the inventive variants is markedly greater than for a silane mixture of TESPD (silane A-II) with a non-bonding silane B* (mixture from the prior art). The inventive rubber mixtures further exhibit an increase in the vulcanization rate k30/90 as apparent in tables 3 and 4. In tables 2 and 3 a silane of type B was added in addition to silane A. In table 4 partial or complete substitution of the silanes A for B was carried out which likewise surprisingly resulted in the described improved characteristics. Also achieved with the inventive rubber mixtures, as shown in table 3, is an improved handling behaviour as is apparent from the improved handling predictors, in particular hardness at 70 C. Here too, the effect is stronger for the inventive combination of silane A and silane B than for silane A with silane B*. The combination with the inventive silane B generally allows a higher hardness level at 70 C. to be achieved, which is not to be expected from the individual measures of the comparative mixtures (pure silane A/pure silane B). The inventive rubber mixture and the inventive vehicle tire accordingly exhibit improved processability and thus simplified producability coupled with optimized handling behaviour. Rolling resistance behaviour is also optimized with the inventive variants.