RUBBER BLEND, SULFUR-CROSSLINKABLE RUBBER MIXTURE, AND VEHICLE TIRE

Abstract

The invention relates to a rubber blend, to a sulfur-crosslinkable rubber mixture comprising the rubber blend and to a vehicle tire comprising such a rubber mixture. The rubber blend comprises at least one solution-polymerized diene polymer A of high molecular weight and at least one solution-polymerized polymer B of low molecular weight, wherein at least one of polymers A and B has been functionalized at the chain end and/or along the polymer chain and/or at a coupling site with at least one group selected from epoxy groups, hydroxyl groups, carboxyl groups, silane sulfide groups, amino groups, siloxane groups, organosilicon groups, phthalocyanine groups and amino group-containing alkoxysilyl groups.

Claims

1.-14. (canceled)

15. A rubber blend comprising: at least one solution-polymerized diene polymer A of high molecular weight, formed from at least one conjugated diene and one or more optional vinylaromatic compound(s), wherein the one or more optional vinylaromatic compound(s) have a content of vinylaromatic compound of 0% to 50% by weight, a vinyl content of 8% to 80% by weight based on any diene content present, and wherein the one or more optional vinylaromatic compound(s), has a glass transition temperature Tg according to DSC of −100° C.<Tg<−35° C., a molecular weight Mw according to GPC of more than 350000 g/mol and a polydispersity PD of 1.1<PD<3; and at least one solution-polymerized polymer B of low molecular weight, formed from at least one conjugated diene, at least one conjugated diene and one or more vinylaromatic compound(s), or at least one or more vinylaromatic compound(s), wherein the one or more vinylaromatic compound(s) has a content of vinylaromatic compound of 0% to 50% by weight, a vinyl content of 8% to 80% by weight based on any diene content present, and wherein the one or more vinylaromatic compound(s) has a glass transition temperature Tg according to DSC of −100° C.<Tg<+80° C., a molecular weight Mw according to GPC of 1300 g/mol<Mw<10000 g/mol and a polydispersity PD of 1<PD<1.5; wherein at least one of polymers A and B has been functionalized at the chain end and/or along the polymer chain and/or at a coupling site with at least one group selected from epoxy groups, hydroxyl groups, carboxyl groups, silane sulfide groups, amino groups, siloxane groups, organosilicon groups, phthalocyanine groups and amino group-containing alkoxysilyl groups.

16. The rubber blend as claimed in claim 15, wherein at least the solution-polymerized polymer B of low molecular weight has been functionalized.

17. The rubber blend as claimed in claim 16, wherein the solution-polymerized diene polymer A of high molecular weight has been functionalized.

18. The rubber blend as claimed in claim 15, wherein at least one of polymer A and polymer B has been functionalized at the chain end with an amino group-containing alkoxysilyl group and at least one further amino group and/or at least one further alkoxysilyl group and/or at least one further amino group-containing alkoxysilyl group, wherein the amino groups are bonded to the chain end of the polymer chain with or without spacers.

19. The rubber blend as claimed in claim 15, wherein at least one of the polymers A and B has been functionalized at the chain end and/or along the polymer chain and/or at a coupling site with a silane sulfide group.

20. The rubber blend as claimed in claim 15, wherein at least one of the polymers A and B has been functionalized at the chain end and/or along the polymer chain and/or at a coupling site with a siloxane group.

21. The rubber blend as claimed in claim 15, wherein at least one of the polymers A and B has coupling sites.

22. The rubber blend as claimed in claim 15 comprising 5 to 100 phr of the at least one solution-polymerized polymer B of low molecular weight, based on the at least one solution-polymerized diene polymer A of high molecular weight.

23. The rubber blend as claimed in claim 15 having a Mooney viscosity (ML1+4, 100° C. according to ASTM-D 1646) of 40 to 100 Mooney units.

24. A sulfur-crosslinkable rubber mixture comprising the rubber blend as claimed in claim 15 and 30 to 300 phr of silica.

25. The rubber blend as claimed in claim 24, wherein the proportion of the diene polymer A of the rubber blend in the rubber mixture is at least 50 phr based on the total amount of solid rubbers present in the rubber mixture.

26. The rubber blend as claimed in claim 24, comprising 0.1 to 20 phr of carbon black.

27. A vehicle tire in which at least one component includes the with sulfur-crosslinked rubber mixture as claimed in claim 24.

28. The vehicle tire as claimed in claim 27, wherein at least the part of a tread that comes into contact with a driving surface comprises the sulfur-crosslinked rubber mixture.

Description

[0104] The invention will now be illustrated in detail by comparative examples and working examples.

[0105] Production of the Rubber Blend of the Invention:

[0106] Copolymerization of 1,3-Butadiene with Styrene (Diene Polymer A, A-1, T.sub.g>−25° C.)

[0107] The copolymerization was conducted in a jacketed 40 L steel reactor that was purged with nitrogen prior to the addition of the organic solvent, the monomers, the polar coordinator compound, the initiator compound and other components. The following components were added in the sequence specified: cyclohexane solvent (18 560 g), butadiene monomer (1412 g), styrene monomer (507 g) and tetramethylethylenediamine (TMEDA, 7.8 g), and the mixture was heated to 40° C., followed by titration with n-butyllithium to remove traces of moisture or other impurities. n-BuLi (14.18 mmol) was added to the polymerization reactor to initiate the polymerization reaction. The polymerization was conducted for 20 min, in the course of which the polymerization temperature was not allowed to rise to more than 70° C. Then butadiene (955 g) and styrene (103 g) as monomers were added over the course of 55 min. The polymerization was conducted for a further 20 min, followed by the addition of 50 g of butadiene monomer. After 20 min, the polymerization was terminated by adding hexamethylcyclotrisiloxane (D3) for functionalization (0.5 equivalent based on the initiator). The resultant polymer has been siloxane group-functionalized. 0.25% by weight of IRGANOX® 1520, BASF, based on the total monomer weight, was added to the polymer solution as stabilizer. This mixture was stirred for 10 min. For preparation of the unfunctionalized polymer A-1, rather than hexamethylcyclotrisiloxane (D3), the polymerization was ended by addition of methanol.

[0108] Copolymerization of 1,3-Butadiene with Styrene (Diene Polymer A-2, A-3, T.sub.g<−25° C.)

[0109] The copolymerization was conducted in a jacketed 40 L steel reactor that was purged with nitrogen prior to the addition of the organic solvent, the monomers, the polar coordinator compound, the initiator compound and other components. The following components were added in the sequence specified: cyclohexane solvent (18 560 g), butadiene monomer (1777 g), styrene monomer (448 g) and tetramethylethylenediamine (TMEDA, 1.0 g), and the mixture was heated to 40° C., followed by titration with n-butyllithium to remove traces of moisture or other impurities. n-BuLi (14.08 mmol) was added to the polymerization reactor to initiate the polymerization reaction. The polymerization was conducted for 20 min, in the course of which the polymerization temperature was not allowed to rise to more than 70° C. Then butadiene (1202 g) and styrene (91 g) as monomers were added over the course of 55 min. The polymerization was conducted for a further 20 min, followed by the addition of 63 g of butadiene monomer. After 20 min, the polymerization was stopped by adding hexamethylcyclotrisiloxane (D3) for functionalization and preparation of polymer A-2 (0.5 equivalent based on the initiator). The resultant polymer has been siloxane group-functionalized. 0.25% by weight of IRGANOX® 1520, BASF, based on the total monomer weight, was added to the polymer solution as stabilizer. This mixture was stirred for 10 min.

[0110] For preparation of the unfunctionalized polymer A-3, rather than hexamethylcyclotrisiloxane (D3), the polymerization was ended by addition of methanol.

[0111] Copolymerization of 1,3-Butadiene with Styrene (Polymer B of Low Molecular Weight)

[0112] The copolymerization was conducted in a jacketed 5 L steel reactor that was purged with nitrogen prior to the addition of the organic solvent, the monomers, the polar coordinator compound, the initiator compound and other components. The following components were added in the sequence specified: cyclohexane solvent (3000 g), tetrahydrofuran (45 g), butadiene monomer (375 g), styrene monomer (125 g), and the mixture was heated to 25° C., followed by titration with n-butyllithium to remove traces of moisture or other impurities. n-BuLi (5.6 g) was added to the polymerization reactor to initiate the polymerization reaction. The polymerization was conducted for 15 min, in the course of which the polymerization temperature was not allowed to rise to more than 70° C. After 15 min, the polymerization was stopped by adding hexamethylcyclotrisiloxane (D3) for functionalization (0.5 equivalent based on the initiator). The resultant polymer has been siloxane group-functionalized. 0.25% by weight of IRGANOX® 1520, BASF, based on the total monomer weight, was added to the polymer solution as stabilizer. This mixture was stirred for 10 min.

[0113] For preparation of the unfunctionalized polymer B-1, rather than hexamethylcyclotrisiloxane (D3), the polymerization is ended by addition of methanol.

[0114] Preparation of Comparative Polymers B-2 and B-3

[0115] The copolymerization was conducted in a jacketed 5 L steel reactor that was purged with nitrogen prior to the addition of the organic solvent, the monomers, the polar coordinator compound, the initiator compound and other components. The following components were added in the sequence specified: cyclohexane solvent (3000 g), tetrahydrofuran (5 g), butadiene monomer (425 g), styrene monomer (75 g), and the mixture was heated to 25° C., followed by titration with n-butyllithium to remove traces of moisture or other impurities. n-BuLi (5.6 g) was added to the polymerization reactor to initiate the polymerization reaction. The polymerization was conducted for 15 min, in the course of which the polymerization temperature was not allowed to rise to more than 70° C. After 15 min, the polymerization was stopped by adding hexamethylcyclotrisiloxane (D3) for functionalization (0.5 equivalent based on the initiator). The resultant polymer has been siloxane group-functionalized. 0.25% by weight of IRGANOX® 1520, BASF, based on the total monomer weight, was added to the polymer solution as stabilizer. This mixture was stirred for 10 min.

[0116] For preparation of the unfunctionalized polymer B-3, rather than to hexamethylcyclotrisiloxane (D3), the polymerization is ended by addition of methanol.

[0117] Table 1 lists the analytical data for polymers A and B.

TABLE-US-00001 TABLE 1 Vinyl Styrene M.sub.w M.sub.n Mooney content content T.sub.g [g/mol] [g/mol] viscosity [% by wt.] [% by wt.] [° C.] Diene polymer A 446070 371725 91.7 63.9 20.1 −20.5 (functionalized) Diene polymer A-1 459320 355983 94.3 64.0 20.3 −20.3 (unfunctionalized) Diene polymer A-2 436080 396421 92.5 29.3 15.0 −60.5 (functionalized) Diene polymer A-3 438020 393900 95.3 29.2 15.1 −60.6 (unfunctionalized) Polymer B-1 9450 7800 n.d. 66.0 25.0 −32 (unfunctionalized) Polymer B 9450 7800 n.d. 66.0 25.0 −32 (functionalized) Polymer B-2 9370 8150 n.d. 30.1 15.1 −59.2 (functionalized) Polymer B-3 9370 8150 n.d. 30.1 15.1 −59.2 (unfunctionalized)

[0118] The polymer solutions of diene polymer A or A-1 and 2.149 mixtures of polymer B or B-1 or B-2 or B-3 and the polymer solutions of diene polymers A-2 or A-3 and 1.817 mixtures of polymer B or B-1 or B-2 or B-3 were combined in various combinations.

[0119] This was followed by stripping with steam in order to remove solvents and other volatile substances, and drying in an oven at 70° C. for 30 min and then additionally at room temperature for three days. The rubber blends obtained in this way contained, based on 100 parts of the diene polymer A/A-1/A-2/A-3, 30 parts (phr) in each case of polymer B/B-1/B-2/B-3. Table 2a lists the designations for the various blends produced; E identifies blends of the invention, and V corresponding comparative blends. Table 2b lists the respective Mooney viscosities MU as analytical index in the table fields.

TABLE-US-00002 TABLE 2a Polymer Polymer Polymer Polymer A A-1 A-2 A-3 Polymer B V-1 V-2 E-1 E-2 Polymer B-1 V-3 / E-3 / Polymer B-2 V-4 V-5 E-4 E-5 Polymer B-3 V-6 / E-6 /

TABLE-US-00003 TABLE 2b Polymer Polymer Polymer Polymer A A-1 A-2 A-3 Polymer B 64 60 65 62 Polymer B-1 62 / 62 / Polymer B-2 60 58 62 59 Polymer B-3 61 / 60 /

[0120] The rubber blends were used to create the rubber mixtures in table 3. As a comparison, table 3 lists rubber mixtures V(1) to V(6) with the rubber blends V-1 to V-6 composed of polymers A/A-1 and B/B-1/B-2/B-3. Likewise shown in table 3 are the inventive rubber mixtures E(1) to E(6); the mixtures of the invention are characterized in that the polymer A has a glass transition temperature of less than −35° C.

TABLE-US-00004 TABLE 3 Constituents Unit V1 V2 V3 V4 V5 V6 BR.sup.a phr 20 20 20 20 20 20 Blend V-1 phr 104 — — — — — Blend V-2 phr — 104 — — — 104 Blend V-3 phr — — 104 — — — Blend V-4 phr — — — 104 — — Blend V-5 phr — — — — 104 — Blend V-6 phr — — — — — 104 N339 carbon black phr 9 9 9 9 9 9 Silica.sup.e phr 90 90 90 90 90 90 Silane.sup.f phr 6.5 6.5 6.5 6.5 6.5 6.5 ZnO phr 2 2 2 2 2 2 Aging stabilizer/ phr 5 5 5 5 5 5 antiozonant/ stearic acid Processing phr 3 3 3 3 3 3 auxiliary.sup.j DPG phr 2 2 2 2 2 2 CBS phr 2.6 2.6 2.6 2.6 2.6 2.6 Sulfur phr 2.1 2.1 2.1 2.1 2.1 2.1 Constituents Unit E1 E2 E3 E4 E5 E6 BR.sup.a phr 20 20 20 20 20 20 Blend E-1 phr 104 — — — — — Blend E-2 phr — 104 — — — — Blend E-3 phr — — 104 — — — Blend E-4 phr — — — 104 — — Blend E-5 phr — — — — 104 — Blend E-6 phr — — — — — 104 N339 carbon black phr 9 9 9 9 9 9 Silica phr 90 90 90 90 90 90 Silane.sup.f phr 6.5 6.5 6.5 6.5 6.5 6.5 ZnO phr 2 2 2 2 2 2 Aging stabilizer/ phr 5 5 5 5 5 5 antiozonant/ stearic acid Processing phr 3 3 3 3 3 3 auxiliary.sup.j DPG phr 2 2 2 2 2 2 CBS phr 2.6 2.6 2.6 2.6 2.6 2.6 Sulfur phr 2.1 2.1 2.1 2.1 2.1 2.1 .sup.aBR with cis content greater than 80% by weight; .sup.eZeosil 1165MP, from Rhodia (BET 149 m.sup.2/g, CTAB 154 m.sup.2/g); .sup.fTESPD Si261, from Evonik; .sup.jAktiplast TS, from Rheinchemie

[0121] The test results summarized in table 4 were ascertained on 195/65 R15 size tires with the ContiWinterContact TS830 profile. For this purpose, the rubber mixture for the tread of the tire in each case was used analogously to the compositions shown in table 3. All results are reported as a relative assessment based on 100% for tire V3. Values exceeding 100% are superior to comparative tire V3 and represent an improvement.

[0122] The ABS wet braking characteristics were determined by the braking distance from 80 km/h on a wet driving surface.

[0123] The ABS dry braking characteristics were determined by the braking distance from 100 km/h on a dry driving surface.

[0124] Rolling resistance corresponds to the rolling resistance force measured on the corresponding machine at 90 km/h.

[0125] The abrasion values are the weight loss of the tire after driving for 10 000 kilometers. Handling characteristics are ascertained in a subjective driving test on a dry driving surface.

[0126] To assess the winter properties, snow traction, i.e. traction force in an acceleration run on a snow-covered driving surface, is ascertained.

TABLE-US-00005 TABLE 4 Tire property V1 V2 V3 V4 V5 V6 E1 E2 E3 E4 E5 E6 ABS dry braking 101 101 100 100 100 99 100 100 99 99 99 98 ABS wet braking 103 102 100 101 100 98 103 102 100 101 100 98 Rolling resistance 104 103 100 104 103 101 107 106 103 108 107 106 Winter properties 101 101 100 102 102 101 110 108 106 113 110 110 Abrasion 107 98 100 108 100 102 120 105 109 125 112 115

[0127] Table 4 shows that the use of a rubber blend of the invention (glass transition temperature of polymer A<−35° C., E1 to E6) achieves a distinct improvement with regard to winter properties, rolling resistance and abrasion in the conflict with wet braking properties; see E1 to E3 as compared with V1 to V3. This advantage is particularly marked when polymer B also has a glass transition temperature of <−50° C. (E4 to E6 by comparison with V4 to V6). Dry braking characteristics remain virtually unaffected thereby the measures.