Sulfur-crosslinked rubber mixture for vehicle tires, containing carbon nanotubes (CNT), vehicle tire having the sulfur-crosslinked rubber mixture, and method for producing the sulfur-crosslinked rubber mixture containing carbon nanotubes

Abstract

A sulfur-crosslinked rubber mixture for vehicle tires including carbon nanotubes (CNT), to a vehicle tire comprising the sulfur-crosslinked rubber mixture and to a process for producing the sulfur-crosslinked rubber mixture comprising CNT. The sulfur-crosslinked rubber mixture according to the invention is characterized in that the CNT are predispersed in at least one polyisoprene. The vehicle tire according to the invention preferably comprises the sulfur-crosslinked rubber mixture in the tread and/or a sidewall and/or a conductivity track.

Claims

1. A method comprising: providing a sulfur-crosslinkable rubber mixture comprising a silane coupling agent and carbon nanotubes, wherein the carbon nanotubes are predispersed in at least one polyisoprene; molding the sulfur-crosslinkable rubber mixture into one or more components of a vehicle tire, wherein one of the one or more components of the vehicle tire is a conductivity track; vulcanizing the vehicle tire; wherein the sulfur-crosslinkable rubber mixture has a specific electrical volume resistance value, according to DIN IEC 60093, of ≤1×10.sup.4 ohm mm after vulcanization; wherein the conductivity track is arranged between an electrically conductive tire component and a tire sensor thus to transmit to the sensor information about the electrical conductivity of the tire; and, wherein the silane coupling agent is selected from the group consisting of 3-mercaptopropyltriethoxysilane, 3-thiocyanatopropyltrimethoxysilane, 3,3′-bis(triethoxysilylpropyl) polysulfides having 2 to 8 sulfur atoms, and mixtures thereof.

2. The method as claimed in claim 1, wherein the at least one polyisoprene is at least one natural polyisoprene.

3. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture comprises the carbon nanotubes in an amount of 0.1 to 25 phr.

4. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture further comprises at least one sulfur-crosslinkable rubber.

5. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture further comprises at least one reinforcing filler, and wherein a quantity ratio of the at least one reinforcing filler to carbon nanotubes is in the range of from 100:1 to 2:1.

6. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture contains not more than 35 phr of plasticizers.

7. The method as claimed in claim 1, wherein the one or more components further comprises a component selected from the group consisting of a tread, a sidewall, an inner component and a flange profile.

8. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture is molded into a tread of the vehicle tire.

9. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture is molded into a sidewall of the vehicle tire.

10. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture is molded into a flange profile of the vehicle tire.

11. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture is molded into an inner component of the vehicle tire.

12. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture has a specific electrical volume resistance value, according to DIN IEC 60093, of ≤1×10.sup.3 ohm mm after vulcanization.

13. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture has a specific electrical volume resistance value, according to DIN IEC 60093, of ≤1×10.sup.2 ohm mm after vulcanization.

14. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture has a specific electrical volume resistance value, according to DIN IEC 60093, of ≤10 ohm mm after vulcanization.

15. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture comprises carbon nanotubes in an amount of ≥3% by volume, and wherein the sulfur-crosslinkable rubber mixture has a specific electrical volume resistance value, according to DIN IEC 60093, of ≤1×10.sup.3 ohm mm after vulcanization.

16. The method as claimed in claim 15, wherein the sulfur-crosslinkable rubber mixture comprises carbon nanotubes in an amount of ≥4% by volume, and wherein the sulfur-crosslinkable rubber mixture has a specific electrical volume resistance value, according to DIN IEC 60093, of ≤1×10.sup.2 ohm mm after vulcanization.

17. The method as claimed in claim 16, wherein the sulfur-crosslinkable rubber mixture comprises carbon nanotubes in an amount of ≥4.5% by volume, and wherein the sulfur-crosslinkable rubber mixture has a specific electrical volume resistance value, according to DIN IEC 60093, of ≤10 ohm mm after vulcanization.

18. The method as claimed in claim 17, wherein the sulfur-crosslinkable rubber mixture comprises carbon nanotubes in an amount of ≥6.5% by volume, and wherein the sulfur-crosslinkable rubber mixture has a specific electrical volume resistance value, according to DIN IEC 60093, of ≤1 ohm mm after vulcanization.

19. The method as claimed in claim 1, wherein the sulfur-crosslinkable rubber mixture is molded into a tread of the vehicle tire, wherein the sulfur-crosslinkable rubber mixture comprises carbon nanotubes in an amount of ≥3% by volume, and wherein the sulfur-crosslinkable rubber mixture has a specific electrical volume resistance value, according to DIN IEC 60093, of ≤1×10.sup.3 ohm mm after vulcanization.

Description

(1) FIG. 1: Specific electrical volume resistance according to DIN IEC 60093; the FIGURE plots ohm mm (y-axis) against vol % of CNT based on the respective rubber mixture (x-axis)

(2) TABLE-US-00001 TABLE 1 Constituent Unit V1 E1 E2 NR (TSR) phr 60 47 35 BR phr 10 10 10 SSBR phr 30 30 30 Carbon black phr 43 31 20 NR-CNT MB .sup.a) phr — 17.69 34.01 Silica phr 16 16 16 Silane .sup.b) phr 2.25 2.25 2.25 Further additives .sup.c) phr 17.1 17.1 17.1 Accelerator .sup.d) phr 1.7 1.7 1.7 Sulfur phr 1.5 1.5 1.5 Viscosity M.U. 74 60 60 Hardness RT Shore A 63 60 60 Rebound % 60 61 61 elasticity 70° C. Tensile strength MPa 22 22 21 M50 MPa 1.4 1.3 1.3 M300 MPa 12 11 10 Elongation at % 522 560 570 break Dispersion % 88 93 87 Abrasion mm.sup.3 114 105 105

(3) Employed Substances of Table 1: a) NR-CNT masterbatch: CNT predispersed in NR: 67.3% by weight NR, 18.7% by weight CNT, 14% by weight resin acids; density 1.03 g/cm.sup.3 b) Silane: TESPD+3-mercaptopropyltriethoxysilane c) Further additives: processing aids: PEG carboxylic ester; hydrocarbon resin; aging stabilizer; antiozonant wax, zinc oxide; stearic acid d) Accelerator: DPG+CBS

(4) As is shown in table 1 the inventive rubber mixtures E1 and E2 exhibit improved abrasion behavior. The other properties are at a comparable level or are even likewise improved.

(5) Electrical conductivity/electrical resistance of various comparative mixtures and inventive mixtures was also investigated. The results are summarized in FIG. 1.

(6) The mixture series have the following compositions (explanation relating to FIG. 1):

COMPARATIVE EXAMPLE V2

(7) ESBR1500_CNT_1: ESBR is the sole rubber matrix, partly from an ESBR-CNT masterbatch and partly added separately:

(8) One data point for 5 vol % CNT in the rubber mixture; to this end 67.8 phr of a masterbatch—containing 16.1% by weight CNT and 82.9% by weight ESBR and balance plasticizer—were mixed with 43.8 phr of ESBR. Further constituents: 3 phr of zinc oxide, 2 phr of stearic acid, 1.5 phr of sulfur, 1.3 phr of accelerator TBBS.

INVENTIVE EXAMPLES E3, E4, E5

(9) NR_CNT_1: NR is the sole rubber matrix, partly from an NR-CNT masterbatch and partly added separately:

(10) 3 data points for 4.5 and 6.5 and 7.6 vol % of CNT in the rubber mixture:

(11) E3: 4.5 vol % CNT: 60 phr of an NR-CNT masterbatch—containing 82.8% by weight NR and 17% by weight CNT and balance plasticizer—and 50.32 phr of NR.

(12) E4: 6.5 vol % CNT: 90 phr of the NR-CNT masterbatch (as described under 4.5 vol % CNT) and 25.48 phr of NR.

(13) E5: 7.6 vol % CNT: 120.77 phr of the same NR-CNT masterbatch and no additional NR, i.e. 0 phr of separate NR.

(14) The mixtures also contained the same further constituents as listed under ESBR1500_CNT_1.

INVENTIVE EXAMPLES E6, E7, E8, E9, E10

(15) 50 NR/50 ESBR (NR_CNT_MB): The rubber matrix consists of 50% by weight ESBR and 50% by weight NR; the CNT are exclusively predispersed in the NR (NR-CNT masterbatch):

(16) 5 data points for 1.5 and 2 and 3 and 4 and 4.7 vol % of CNT in the rubber mixture:

(17) E6: 1.5 vol % CNT: 18.59 phr of the NR-CNT masterbatch (as described under 4.5 vol % CNT) and 34.61 phr of NR and 50 phr of ESBR;

(18) E7: 2 vol % CNT: 24.91 phr of the same NR-CNT masterbatch and 29.37 phr of NR and 50 phr of ESBR;

(19) E8: 3 vol % CNT: 37.75 phr of the same NR-CNT masterbatch and 18.74 phr of NR and 50 phr of ESBR;

(20) E9: 4 vol % CNT: 50.86 phr of the same NR-CNT masterbatch and 7.89 phr of NR and 50 phr of ESBR;

(21) E10: 4.7 vol % CNT: 60.39 phr of the same NR-CNT masterbatch and no additional NR, i.e. 0 phr of NR and 50 phr of ESBR;

(22) The mixtures also contained the same further constituents as listed under ESBR1500_CNT_1.

COMPARATIVE EXAMPLES V3, V4, V5 AND V6

(23) 50 NR/50 ESBR (ESBR_CNT_MB): The rubber matrix consists of 50% by weight ESBR and 50% by weight NR; the CNT are exclusively predispersed in the ESBR (ESBR-CNT masterbatch):

(24) 4 data points for 2 and 3 and 4 and 4.5 vol % of CNT:

(25) V3: 2 vol % CNT: 26.55 phr of the ESBR-CNT masterbatch (as described under ESBR1500_CNT_1) and 27.99 phr of ESBR and 50 phr of NR;

(26) V4: 3 vol % CNT: 40.26 phr of the ESBR-CNT masterbatch (as described under ESBR1500_CNT_1) and 16.63 phr of ESBR and 50 phr of NR;

(27) V5: 4 vol % CNT: 54.22 phr of the ESBR-CNT masterbatch (as described under ESBR1500_CNT_1) and 5.05 phr of ESBR and 50 phr of NR;

(28) V6: 4.5 vol % CNT: 60.31 phr of the ESBR-CNT masterbatch (as described under ESBR1500_CNT_1) and no additional ESBR, i.e. 0 phr of ESBR and 50 phr of NR;

(29) The mixtures also contained the same further constituents as listed under ESBR1500_CNT_1.

COMPARATIVE EXAMPLES V7, V8, V9 AND V10

(30) 50 NR/50 ESBR (½ NR_CNT_MB, ½ ESBR_CNT_MB): The rubber matrix consists of 50% by weight ESBR and 50% by weight NR; the CNT are predispersed both in ESBR (ESBR-CNT MB) and in the NR (NR-CNT masterbatch):

(31) V7: 1.5 vol % CNT: 9.29 phr of the NR-CNT masterbatch (as described under 4.5 vol % CNT) and 42.3 phr of NR and 9.91 phr of the ESBR-CNT masterbatch (as described under ESBR1500_CNT_1) and 41.79 phr of ESBR;

(32) V8: 2 vol % CNT: 12.46 phr of the NR-CNT masterbatch (as described under 4.5 vol % CNT) and 39.69 phr of NR and 13.27 phr of the ESBR-CNT masterbatch (as described under ESBR1500_CNT_1) and 39 phr of ESBR;

(33) V9: 5 vol % CNT: 32.12 phr of the NR-CNT masterbatch (as described under 4.5 vol % CNT) and 23.4 phr of NR and 34.24 phr of the ESBR-CNT masterbatch (as described under ESBR1500_CNT_1) and 21.61 phr of ESBR;

(34) V10: 8.7 vol % CNT: 60.39 phr of the NR-CNT masterbatch (as described under 4.5 vol % CNT) and no additional, i.e. 0 phr, NR and 60.31 phr of the ESBR-CNT masterbatch (as described under ESBR1500_CNT_1) and no additional, i.e. 0 phr, ESBR;

(35) The mixtures also contained the same further constituents as listed under ESBR1500_CNT_1.

(36) As is apparent in FIG. 1 (in conjunction with the above explanations) the inventive rubber mixtures (E3, E4, E5 and E6, E7, E8, E9, E10) in which the CNT are exclusively predispersed in at least one polyisoprene, here NR, achieve, surprisingly, a markedly lower electrical resistance and thus a markedly improved electrical conductivity.