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

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 30 phf of at least one silane A having general empirical formula A-I) and/or A-XI)

(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;A-I)

(R.sup.1).sub.oSiR.sup.2(SR.sup.3).sub.xSX; andA-XI) 5 to 30 phf of at least one silane B having general empirical formula B-I)

(R.sup.1).sub.oSiR.sup.4SR.sup.4Si(R.sup.1).sub.oB-I) wherein x is an integer from 2 to 10, q is 1, 2 or 3 and s is 0, 1, 2 or 3 and X is a hydrogen atom or a C(O)R.sup.8 group wherein R.sup.8 is selected from hydrogen C.sub.1-C.sub.20-alkyl groups, C.sub.6-C.sub.20-aryl groups, C.sub.2-C.sub.20-alkenyl groups and C.sub.7-C.sub.20-aralkyl groups.

Claims

1.-15. (canceled)

16. A sulfur-crosslinkable rubber mixture comprising at least the following constituents: at least one diene rubber; 10 to 300 phr of at least one silica; 1 to 30 phf of at least one silane A having general empirical formula A-I) and/or A-XI), where:
(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;A-I)
(R.sup.1).sub.oSiR.sup.2(SR.sup.3).sub.xSX;A-XI) and, 0.5 to 30 phf of at least one silane B having general empirical formula B-I), where
(R.sup.1).sub.oSiR.sup.4Si(R.sup.1).sub.oB-I) wherein o may be 1 or 2 or 3 and 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 A-XI) 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 A-XI) and B-I) in each (R.sup.1).sub.oSi group at least one R.sup.1 is selected from the abovementioned options where this R.sup.1 i) is bonded to the silicon atom via an oxygen atom or ii) is a halide; and, wherein the radicals R.sup.2, R.sup.3 and R.sup.4 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 s is 1 or 2 or 3; and X is a hydrogen atom or a C(O)R.sup.8 group wherein R.sup.8 is selected from hydrogen, C.sub.1-C.sub.20-alkyl groups, C.sub.6-C.sub.20-aryl groups, C.sub.2-C.sub.20-alkenyl groups and C.sub.7-C.sub.20-aralkyl groups.

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

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

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

20. The sulfur-crosslinkable rubber mixture according to claim 16, wherein R.sup.4 is an alkyl group having 2 to 6 carbon atoms.

21. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the silane A-I) has the following structure conforming to formula A-II): ##STR00003## wherein x is an integer from 2 to 10.

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

23. The sulfur-crosslinkable rubber mixture according to claim 16, wherein X is an alkanoyl group having 1 to 10 carbon atoms.

24. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the silane A-XI) has the following structure conforming to formula A-XII):
(EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6SC(O)CH.sub.3.A-XII)

25. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the silane A-XI) has the following structure conforming to formula A-XIII):
(EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6SC(O)(CH.sub.2).sub.6CH.sub.3.A-XIII)

26. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the silane A-XI) has the following structure conforming to formula A-XIV):
(EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6SC(O)(CH.sub.2).sub.16CH.sub.3.A-XIV)

27. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the silane A-XI) has the following structure conforming to formula A-XV):
(EtO).sub.3Si(CH.sub.2).sub.3SC(O)(CH.sub.2).sub.16CH.sub.3.A-XV)

28. The sulfur-crosslinkable rubber mixture according to claim 16, wherein the silane B has the following structure conforming to formula B-II):
(EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.3Si(OEt).sub.3.B-II)

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

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

Description

[0182] The invention will now be more particularly elucidated with the aid of comparative examples and working examples which are summarized in the following tables.

[0183] The general composition of the rubber mixture upon which the examples are based is summarized in table 1 under R1 (recipe 1). In tables 2 to 8 both the employed silane types and the silane amounts were then varied to afford comparative mixtures and inventive mixtures. The comparative mixtures are labeled V and the inventive mixtures are labeled E. Tables 2 to 4 are related and related tests comprise adding silane B in addition to silane A. Tables 5 to 8 show further working examples and related test series here comprise undertaking a complete or partial substitution of silane A by silane B, starting from comparative mixtures.

[0184] In the individual examples the respective silanes were premixed with one another and then added to the rubber mixture in the base mixing stage. The reported quantities for the silanes in phf relate to 95 phr of silica.

Production of 1-Chloro-6-Thiopropyltriethoxysilylhexane

[0185] NaOEt (21% in EtOH; 1562 g; 4.820 mol) was added to mercaptopropyltriethoxysilane (1233 g; 5.170 mol) over 1 h while stirring at room temperature. Once addition was complete the reaction mixture was heated at reflux for 2 h and then left to cool to room temperature. The intermediate formed was added over 30 min to 1,6-dichlorohexane (4828 g; 31.14 mol) that had been heated to 80 C. Once addition was complete the reaction mixture was heated at reflux for 3 h, before being left to cool to room temperature. The reaction mixture was filtered and the filtercake was rinsed with EtOH. The volatile constituents were removed under reduced pressure and the intermediate product 1-chloro-6-thiopropyltriethoxysilylhexane (yield: 89%, molar ratio: 97% 1-chloro-6-thiopropyltriethoxysilylhexane, 3% bis(thiopropyltriethoxysilyl)hexan); % by weight: 95% by weight 1-chloro-6-thiopropyltriethoxysilylhexane, 5% by weight 1,6-bis(thiopropyltriethoxysilyl)hexane was obtained as a colourless to brown liquid.

The Silane.SUP.f) .was Produced as Follows:

[0186] Na.sub.2CO.sub.3 (59.78 g; 0.564 mol) and an aqueous solution of NaSH (40% in water; 79.04 g; 0.564 mol) were initially charged together with water (97.52 g). Then tetrabutylphosphonium bromide (TBPB) (50% in water; 3.190 g; 0.005 mol) was added and acetyl chloride (40.58 g; 0.517 mol) added dropwise over 1 h, the reaction temperature being maintained at 25-32 C. Upon complete addition of the acetyl chloride, the mixture was stirred at room temperature for 1 h. Then TBPB (50% in water; 3.190 g; 0.005 mol) and 1-chloro-6-thiopropyltriethoxysilylhexane (see above; 167.8 g; 0.470 mol) were added and the mixture heated at reflux for 3-5 h. The progress of the reaction was monitored by means of gas chromatography. Once the 1-chloro-6-thiopropyltriethoxysilylhexane had reacted to an extent of >96%, water was added until all salts had dissolved and the phases were separated. The volatile constituents of the organic phase were removed under reduced pressure and

[0187] S-(6-((3-(triethoxysilyl)propyl)thio)hexyl)thioacetate)

[0188] (Yield: 90%, molar ratio: 97% S-(6-((3-(triethoxysilyl)propyl)thio)hexyl)thioacetate (silane A-XII), 3% bis(thiopropyltriethoxysilyl)hexane;

[0189] % by weight: 96% by weight S-(6-((3-(triethoxysilyl)propyl)thio)hexyl)thioacetate (silane A-XII), 4% by weight 1,6-bis(thiopropyltriethoxysilyl)hexane) was obtained as a yellow to brown liquid.

The Silane.SUP.g) .was Produced as Follows:

[0190] Na.sub.2CO.sub.3 (220.2 g; 2.077 mol) and an aqueous solution of NaSH (40% in water; 291.2 g; 2.077 mol) were initially charged together with water (339.2 g). Then tetrabutylammonium bromide (TBAB) (50% in water; 10.96 g; 0.017 mol) was added and octanoyl chloride (307.2 g; 1.889 mol) added dropwise over 2.5 h, the reaction temperature being maintained at 24-28 C. Upon complete addition of the octanoyl chloride the mixture was stirred at room temperature for 1 h. Then TBAB (50% in water; 32.88 g; 0.051 mol) and 1-chloro-6-thiopropyltriethoxysilylhexane (see above; 606.9 g; 1.700 mol) were added and the mixture heated at reflux for 10 h. Then water was added until all salts had dissolved and the phases were separated. The volatile constituents of the organic phase were removed under reduced pressure and

[0191] S-(6-((3-(triethoxysilyl)propyl)thio)hexyl)thiooctanoate (yield: 95%, molar ratio: 97% S-(6-((3-(triethoxysilyl)propyl)thio)hexyl)thiooctanoate (silane A-XIII), 3% bis(thiopropyltriethoxysilyl)hexane;

[0192] % by weight: 96% by weight S-(6-((3-(triethoxysilyl)propyl)thio)hexyl)thiooctanoate, 4% by weight 1,6-bis(thiopropyltriethoxysilyl)hexane) was obtained as a yellow to brown liquid.

[0193] The silane.sup.h) was produced from 1-chloro-6-thiopropyltriethoxysilylhexane (see above) as per the synthesis example 1 and 3 in JP2012149189.

[0194] S-(6-((3-(triethoxysilyl)propyl)thio)hexyl)thiooctadecanoate (yield: 89%, molar ratio: 97%

[0195] S-(6-((3-(triethoxysilyl)propyl)thio)hexyl)thiooctadecanoate (silane A-XIV), 3% bis(thiopropyltriethoxysilyl)hexane; % by weight: 97% by weight S-(6-((3-(triethoxysilyl)propyl)thio)hexyl)thiooctadecanoate, 3% by weight 1,6-bis(thiopropyltriethoxysilyl)hexane) was obtained as a yellow to brown liquid.

The Silane.SUP.i) .was Produced as Follows:

[0196] 6-Bis(thiopropyltriethoxysilylhexyl) disulfide was produced as per synthesis example 1 and example 1 of EP 1375504.

[0197] By contrast with synthesis example 1 of EP 1375504 the intermediate was not distilled.

[0198] Analysis: (88% yield, molar ratio:

[0199] 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 6% (EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6S(CH.sub.2).sub.3Si(OEt).sub.3,

[0200] % by weight: silane of formula A-II: 95% by weight

[0201] (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 5% by weight

[0202] (EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.6S(CH.sub.2).sub.3Si(OEt).sub.3).

Production of Bis(Triethoxysilylpropyl)Sulfide (Silane.SUP.k)., B-II)

[0203] 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.

[0204] 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).sub.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.

[0205] 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.

[0206] All mixtures were used to produce test specimens by vulcanization after t.sub.95 to t.sub.100 (measured on a Moving Die Rheometer according to ASTM D 5289-12/ISO 6502) under pressure at 160 C. to 170 C. and these test specimens were used to determine material characteristics typical for the rubber industry with the test methods reported hereinbelow. [0207] Shore A hardness at room temperature according to DIN ISO 7619-1 [0208] Dynamic storage modulus E at 55 C. from dynamic-mechanical measurement according to DIN 53 513, strain sweep at 0.15% and 8% elongation; reported value: E at 0.15% minus E at 8% [0209] Loss factor tan (10%) and dynamic storage modulus (G(1%), G(100%)) from RPA (rubber process analyzer) based on ASTM D6601 from second strain sweep at 1 Hz and 70 C.; reported value: G at 1% minus G at 100% [0210] Breaking energy density determined in tensile test according to DIN 53 504, wherein braking energy density is the work required for breaking based on the volume of the sample.

TABLE-US-00001 TABLE 1 Constituents Unit R1 NR TSR phr 10 BR .sup.o) phr 18 SSBR .sup.p) phr 72 Silica .sup.a) phr 95 TDAE phr 50 Other additives .sup.b) phr 9 Silane - varied .sup.d) phf varied Accelerator .sup.c) phr 4 Sulfur phr 2

Substances Used:

[0211] a) Silica: VN3, Evonik [0212] b) Other additives: anti-aging additives, anti-ozonant wax, zinc oxide, stearic acid [0213] c) DPG+CBS [0214] d) Silane variants according to e) to m) [0215] e) NXT, Momentive; contains to extent of >90% by weight the silane of formula A-XV) [0216] f) Contains 97 mol % silane of formula A-II), production as above [0217] g) Contains 97 mol % silane of formula A-III), production as above [0218] h) Contains 97 mol % silane of formula A-IV), production as above [0219] i) 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) [0220] j) Si 266, Evonik; contains TESPD: silane of formula A*: [0221] A* (EtO).sub.3Si(CH.sub.2).sub.3S.sub.x(CH.sub.2).sub.3Si(OEt).sub.3, bonding but not inventive under formula A-I) 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 [0222] k) Silane B-II): (EtO).sub.3Si(CH.sub.2).sub.3S(CH.sub.2).sub.3Si(OEt).sub.3, production as above [0223] l) Mole fraction of non-bonding silane B-II) in silane mixture mole fraction in % of non-bonding silane B-II) in silane mixture: calculated from added silanes.sup.j) and .sup.k) (i.e. taking account of low mol % of silane B-II) in silane .sup.j)) [0224] m) Silane B*: bistriethoxysilyloctane from ABCR GmbH non-bonding but not inventive under formula B-I) [0225] n) Mole fraction of non-bonding silane B* in silane mixture [0226] o) Polybutadiene: Europrene Neocis BR 40, Polimeri [0227] p) Sprintan SLR-4601, Trinseo

TABLE-US-00002 TABLE 2 Silane Unit V1 V2 V3 V4 E1 E2 Silane .sup.e) phf 7.2 7.2 7.2 7.2 Silane .sup.j) phf 7.2 7.2 Silane .sup.k) phf 2.8 3.8 1.7 2.6 Mol % of B-II) .sup.l) Mol % 35 41 17 23 Silane .sup.m) phf 1.7 2.6 Mol % of B* .sup.n) Mol % 17 23 E(0.15%)-E(8%) MPa 7.7 7.6 6.4 7.2 4.2 4.4 G(1%)-G(100%) kPa 1089 1046 1096 1106 859 908 Breaking energy J/cm.sup.3 25 23.6 26.7 23.4 29.7 32.6 density RT hardness Shore A 58.9 59.2 68.0 67.6 61.4 61.7

TABLE-US-00003 TABLE 3 Silane Unit E3 E4 V5 Silane .sup.i) phf 7.2 7.2 Silane .sup.k) phf 1.8 2.7 7.2 Mol % of B-II) .sup.l) 29 38 100 E(0.15%)-E(8%) MPa 5.7 7.3 G(1%)-G(100%) kPa 915 965 1238 Breaking energy J/cm.sup.3 31.8 27.6 27.3 density RT hardness Shore A 61.8 61.2 53.8

TABLE-US-00004 TABLE 4 Silane Unit E5 E6 E7 E8 E9 E10 Silane .sup.f) phf 7.2 7.2 Silane .sup.g) phf 7.2 7.2 Silane .sup.h) phf 7.2 7.2 Silane .sup.k) phf 1.6 2.4 1.3 2.0 1.0 1.5 Mol % of B-II) .sup.l) Mol % 17 23 17 23 17 23 E(0.15%)-E(8%) MPa 5.9 5.8 4.7 4.8 4.4 4.8 G(1%)-G(100%) kPa 922 930 885 890 918 911 Breaking energy J/cm.sup.3 39.9 33.9 39.1 37.0 38.9 39.6 density RT hardness Shore A 59.8 60.3 56.8 58.2 57.9 58.2

TABLE-US-00005 TABLE 5 Silane Unit V6 V7 V8 V9 V10 Silane .sup.e) phf 6.6 4.4 Silane .sup.j) phf 7.2 4.3 2.9 Silane B-II) .sup.k) phf 2.6 3.8 Mol % of B-II) .sup.l) Mol % 7 43 62 Silane B* .sup.m) phf 2.7 4.0 Mol % of B* .sup.n) Mol % 25 43 Tan d (10%) 0.214 0.221 0.182 0.183 0.187 RT hardness Shore A 58.6 56.8 66.8 65.8 65.4

TABLE-US-00006 TABLE 6 Silane Unit V11 E11 E12 E13 Silane .sup.e) phf 11.1 8.8 6.6 4.4 Silane B-II) .sup.k) phf 1.3 2.7 4.0 Mol % of B-II) .sup.l) Mol % 11 25 43 Tan d (10%) 0.205 0.152 0.152 0.149 RT hardness Shore A 58.6 61.6 62.8 63.2

TABLE-US-00007 TABLE 7 Silane Unit E14 E15 E16 E17 E18 E19 Silane .sup.i) phf 8.6 6.4 4.3 Silane .sup.f) phf 9.6 7.2 4.8 Silane .sup.k) phf 1.3 2.7 4.0 1.3 2.7 4.0 Mol % of B-II) .sup.l) Mol % 20 40 60 11 25 43 Tan d (10%) 0.160 0.161 0.165 0.159 0.161 0.169 RT hardness Shore A 61.0 61.0 58.5 60.5 60.4 59.0

TABLE-US-00008 TABLE 8 Silane Unit E20 E21 E22 E23 E24 E25 V12 Silane .sup.g) phf 11.7 8.7 5.8 Silane .sup.h) phf 15.1 11.3 7.5 Silane B-II) .sup.k) phf 1.3 2.7 4.0 1.3 2.7 4.0 6.7 Mol % of B-II) .sup.l) Mol % 11 25 43 11 25 43 100 Tan d (10%) 0.159 0.155 0.166 0.150 0.160 0.169 0.202 RT hardness Shore A 53.2 49.1 53.6 52.8 54.2 56.4 60.8

[0228] As is apparent from the tables inventive rubber mixtures exhibit a reduced Payne effect compared to the prior art as is apparent from the smaller differences for the dynamic storage modulus E from the Eplexor measurement and the dynamic stiffness G from the RPA measurement. The inventive rubber mixtures thus exhibit an improvement in hysteresis characteristics and thus improved rolling resistance indicators. This is also apparent from the lower values for tan delta. In addition inventive rubber mixtures exhibit an elevated breaking energy density and thus improved tearing characteristics. The hardness of the inventive rubber mixtures moreover remains at a comparable level compared to the prior art.