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 −50° 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, where 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

PRODUCTION OF THE RUBBER BLEND OF THE INVENTION

[0093] Copolymerization of 1,3-Butadiene with Styrene (Diene Polymer A)

[0094] 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 (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.

[0095] For preparation of the unfunctionalized polymer A-1, rather than hexamethylcyclotrisiloxane (D3), the polymerization reaction was ended by addition of methanol.

[0096] Copolymerization of 1,3-Butadiene with Styrene (Polymer B of Low Molecular Weight)

[0097] 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.

[0098] For preparation of the unfunctionalized polymer B-1, rather than hexamethylcyclotrisiloxane (D3), the polymerization reaction is ended by addition of methanol.

Preparation of Comparative Polymers B-2 and B-3

[0099] 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. For preparation of the unfunctionalized polymer B-3, rather than hexamethylcyclotrisiloxane (D3), the polymerization reaction is ended by addition of methanol.

[0100] 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 436080 396421 92.5 29.3 15.0 −60.5 (functionalized) Diene polymer A-1 438020 393900 95.3 29.2 15.1 −60.6 (unfunctionalized) Polymer B 9450 7800 n. d. 66.0 25.0 −32 (functionalized) Polymer B-1 9450 7800 n. d. 66.0 25.0 −32 (unfunctionalized) Polymer B-2 9370 8150 n. d. 30.1 15.1 −59.2 (unfunctionalized) Polymer B-3 9370 8150 n. d. 30.1 15.1 −59.2 (unfunctionalized)

[0101] 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 were combined in various combinations. 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 or A-1 and 30 parts (phr) of polymer B or B-1 or B-2 or B-3. Table 2 lists the analytical data for the rubber blends.

TABLE-US-00002 TABLE 2a Mooney Content of Content of Content of Content of Content of Content of viscosity polymer A polymer A-1 polymer B polymer B-1 polymer B-2 polymer B-3 (ML 1 + 4) (phr) (phr) (phr) (phr) (phr) (phr) (MU) Rubber blend E-1 100 0 0 30 0 0 62 Rubber blend E-2 0 100 30 0 0 0 62 Rubber blend E-3 100 0 30 0 0 0 65 Rubber blend V-1 100 0 0 0 0 30 60 Rubber blend V-2 0 100 0 0 30 0 59 Rubber blend V-3 100 0 0 0 30 0 62

[0102] The rubber blends were used to create the rubber mixtures in table 3. As a comparison, rubber mixtures V(1) to V(3) with the rubber blends V1 to V3 composed of the polymers A or A-1 and B-2 or B-3 are in table 3, where polymer B-2 or B-3 has a glass transition temperature <−50° C.

TABLE-US-00003 TABLE 3 Constituents Unit V1 V2 V3 E1 E2 E3 BR.sup.a phr 20 20 20 20 20 20 Blend V-1 phr 104 — — — — — Blend V-2 phr 104 — — — — Blend V-3 phr — 104 — — — Blend E-1 phr — — — 104 — — Blend E-2 phr — — — — 104 — Blend E-3 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 auxiliary.sup.j phr 3 3 3 3 3 3 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

[0103] 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 produced analogously to the compositions shown in table 3. All results are reported as a relative assessment based on 100% for tire V1. Values exceeding 100% are superior to comparative tire V1 and represent an improvement.

[0104] The ABS wet braking characteristics were determined by the braking distance from 80 km/h on a wet driving surface.

[0105] The ABS dry braking characteristics were determined by the braking distance from to 100 km/h on a dry driving surface.

[0106] Rolling resistance corresponds to the rolling resistance force measured on the corresponding machine at 90 km/h.

[0107] The abrasion values are the weight loss of the tire after driving for 10 000 kilometers. Handling characteristics are ascertained in a subjective vehicle test on a dry driving surface.

[0108] 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-00004 TABLE 4 Tire property V1 V2 V3 E1 E2 E3 ABS dry braking 100 101 101 101 102 102 ABS wet braking 100 102 103 102 104 105 Rolling resistance 100 102 103 99 102 103 Winter properties 100 101 101 99 100 100 Handling 100 100 100 105 105 110 Abrasion 100 98 106 98 96 105 Processing — ∘ — ∘ ∘ —

[0109] Table 4 shows that the use of an inventive rubber blend achieves a distinct improvement with regard to handling characteristics and the rolling resistance/abrasion/winter properties conflict versus wet braking properties; see E1 to E3. Dry braking characteristics remain virtually unaffected thereby. As can also be seen, these advantages arise to a significant degree when the low-molecular-weight polymer constituent B of the rubber blend E has a glass transition temperature of >−50° C. The mixtures containing the inventive rubber blends also have advantages in processing characteristics (o=good, -=with difficulties, --=with considerable difficulties) over the remaining mixtures.