IMPROVING THE ROLLING RESISTANCE OF DIENE RUBBER TIRES BY MEANS OF SILANE-MODIFIED POLYBUTADIENES

Abstract

The invention relates to the use of silane-modified polybutadienes in rubber mixtures, in particular for improving the rolling resistance of diene rubber tires. In particular, the invention is directed to silane-modified polybutadienes in rubber mixtures, wherein the polybutadiene comprises the 1,3-butadiene-derived monomer units and wherein the proportion of A in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 10 to 60 mol %, and wherein the sum of the proportions of B and C in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 40 to 90 mol %.

Claims

1. A rubber comprising silane-modified polybutadiene, wherein the polybutadiene comprises the 1,3-butadiene-derived monomer units ##STR00006## and wherein the proportion of A in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 10 to 60 mol %, and wherein the sum of the proportions of B and C in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 40 to 90 mol %.

2. The rubber according to claim 1, wherein the silane-modified polybutadienes are obtainable by reacting hydroxyl-terminated polybutadienes produced by free-radical polymerization with one or more organosilane compounds.

3. The rubber according to claim 1, wherein the proportion of A) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 15 to 30 mol %, the proportion of B) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 50 to 70 mol % and the proportion of C) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 15 to 30 mol %.

4. The rubber according to claim 2, wherein the organosilane compound is selected from the group comprising compounds of formula I
OCN-R-Si(OR.sup.1).sub.x(R.sup.2).sub.3?x I where R represents linear or branched alkylene chains having 1-4 carbon atoms and R.sup.1 and R.sup.2 simultaneously or independently of one another represent linear or branched alkyl chains having from 1 to 5 carbon atoms.

5. A rubber mixture comprising silane-modified polybutadienes, wherein the polybutadiene comprises the 1,3-butadiene-derived monomer units ##STR00007## and wherein the proportion of A in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 10 to 60 mol %, and wherein the sum of the proportions of B and C in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 40 to 90 mol %.

6. The rubber mixtures according to claim 5, wherein the silane-modified polybutadiene is employed in an amount of from 0.5 to 25 parts by wt based on 100 parts by wt of rubber.

7. The rubber mixtures according to claim 5, wherein said mixtures comprise 10 to 150 parts by wt of precipitated silica, 0 to 100 parts by wt of carbon black and 0.5 to 15 parts by wt of silane-modified polybutadiene according to claim 1, in each case based on 100 parts by weight of rubber.

8. The rubber mixtures according to claim 5, wherein said mixtures comprise an organosilane.

9. The rubber mixtures according to claim 8, wherein said mixtures comprise 0.5 to 20 parts by wt of organosilane based on 100 parts by wt of rubber.

10. The rubber mixtures according to claim 8, wherein said mixtures comprise natural rubber or mixtures of natural rubber and diene rubber, 10 to 150 parts by wt of precipitated silica, 0 to 100 parts by wt of carbon black, 0.5 to 20 parts by wt of organosilane and 0.5 to 25 parts by wt of the silane-modified polybutadiene, in each case based on 100 parts by weight of rubber.

11. A product comprising the rubber mixtures according to claim 5 wherein the product is selected from the group consisting of tires, profiles, cable sheaths, hoses, drive belts, conveyor belts, tire treads, shoe soles, sealing rings and damping elements.

12. A process of making a silane-terminated polybutadiene, the process comprising the steps of a) providing a polybutadiene produced by free-radical polymerization and having hydroxyl groups, and b) reacting the polybutadiene having hydroxyl groups from step a) with an organosilane compound, wherein the polybutadiene comprises the 1,3-butadiene-derived monomer units ##STR00008## and wherein the proportion of A in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 10 to 60 mol %, and wherein the sum of the proportions of B and C in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 40 to 90 mol %.

13. The process of claim 12 wherein the silane-modified polybutadienes are obtainable by reacting hydroxyl-terminated polybutadienes produced by free-radical polymerization with one or more organosilane compounds

14. The process of claim 12 wherein the proportion of A) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 15 to 30 mol %, the proportion of B) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 50 to 70 mol % and the proportion of C) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 15 to 30 mol %.

15. The process of claim 12 wherein the organosilane compound is selected from the group comprising compounds of formula I
OCN-R-Si(OR.sup.1).sub.x(R.sup.2).sub.3?x I where R represents linear or branched alkylene chains having 1-4 carbon atoms and R.sup.1 and R.sup.2 simultaneously or independently of one another represent linear or branched alkyl chains having from 1 to 5 carbon atoms

16. The rubber according to claim 2, wherein the proportion of A) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 15 to 30 mol %, the proportion of B) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 50 to 70 mol % and the proportion of C) in the entirety of the 1,3-butadiene-derived monomer units present in the polybutadiene is from 15 to 30 mol %.

17. The rubber according to claim 3, wherein the organosilane compound is selected from the group comprising compounds of formula I
OCN-R-Si(OR.sup.1).sub.x(R.sup.2).sub.3?x I where R represents linear or branched alkylene chains having 1-4 carbon atoms and R.sup.1 and R.sup.2 simultaneously or independently of one another represent linear or branched alkyl chains having from 1 to 5 carbon atoms.

18. The rubber mixtures according to claim 6, wherein said mixtures comprise an organosilane.

19. The rubber mixtures according to claim 18, wherein said mixtures comprise 0.5 to 20 parts by wt of organosilane based on 100 parts by wt of rubber.

20. The rubber mixtures according to claim 18, wherein said mixtures comprise natural rubber or mixtures of natural rubber and diene rubber, 10 to 150 parts by wt of precipitated silica, 0 to 100 parts by wt of carbon black, 0.5 to 20 parts by wt of organosilane and 0.5 to 25 parts by wt of the silane-modified polybutadiene, in each case based on 100 parts by weight of rubber.

Description

EXAMPLES

[0081] Production of the Silane-Modified Polybutadienes:

[0082] Raw Materials Employed:

[0083] Hydroxyl-terminated polybutadiene (POLYVEST? HT; Evonik), isocyanatopropyltriethoxysilane (Sigma Aldrich), isocyanatopropyltrimethoxysilane (Evonik), Coscat 83-bismuth trisneodecanoate/neodecanoic acid (58/42%) (C. H. Erbsl?h); dibutyltin laurate (Sigma Aldrich).

[0084] Methods:

[0085] Gel permeation chromatography (GPC) of hydroxyl-terminated polybutadienes: Measurements were carried out at 40? C. in tetrahydrofuran (THF) at a concentration of 1 g/L and a flow rate of 0.3 ml/min. Chromatographic separation was achieved using a PSS SDV Micro 5 ?/4.6?30 mm precolumn and a PSS SDV Micro linear S 5 ?/4.6?250 mm (2?) separation column. Detection was by means of an RI detector. Calibration was carried out by means of a polybutadiene standard (PSS-Kit polybutadiene-1,4, Mp 831-106000, Part No.:PSS-bdfkit, Mn: 1830/4330/9300/18000/33500).

[0086] Gel permeation chromatography (GPC) of silane-terminated polybutadienes: Measurements were carried out at room temperature in tetrahydrofuran (THF) at a concentration of 5 g/L and a flow rate of 1 ml/min. Chromatographic separation was effected using a combination of styrene-divinylbenzene columns (2?3 cm, 5 ?n, linear; 1?30 cm 5 ?m, 100 ?). Detection was by means of an RI detector. Calibration was carried out by means of polystyrene standards and absolute molecular weights obtained via Mark-Houwink constants (a=0.73; k=0.0266 ml/g).

[0087] Viscosity Determination:

[0088] The viscosities (cone-plate) of the materials were determined to DIN 53018 with a Rheometer Physica MCR 301 from ANTON PAAR Germany GmbH.

Example 1

[0089] In a typical reaction 84.4 g of a hydroxyl-terminated polybutadiene produced by free-radical polymerization from Evonik and 0.05 wt % of the catalyst (COSCAT 83 or DBTL) were initially charged under nitrogen into a three-necked flask fitted with a dropping funnel and thermometer and heated to 60? C. Once this temperature had been reached 15.5 g of 3-isocyanatopropyltrimethoxysilane were added via the dropping funnel with stirring and the reaction mixture was stirred for three hours. The end of the reaction was ascertained by determining the residual isocyanate content (NCO<0.1%) by titration.

[0090] GPC (PS Standard): M.sub.n=4.600 g/mol; M.sub.w=11.600 g/mol; D=2.93

[0091] Viscosity (cone-plate, 20? C.): 8.9 Pa*s

Example 2

[0092] In a typical reaction 81.9 g of a hydroxyl-terminated polybutadiene produced by free-radical polymerization from Evonik Industries AG and 0.05 wt % of the catalyst (COSCAT 83 or DBTL) were initially charged under nitrogen into a three-necked flask fitted with a dropping funnel and thermometer and heated to 60? C. Once this temperature had been reached 18 g of 3-isocyanatopropyltrimethoxysilane were added via the dropping funnel with stirring and the reaction mixture was stirred for three hours. The end of the reaction was ascertained by determining the residual isocyanate content (NCO<0.1%) by titration. GPC (PS Standard): M.sub.n=4.200 g/mol; M.sub.w=10.500 g/mol; D=2.48

[0093] Viscosity (20? C.): 9.6 Pa*s

Example 2A

[0094] Produced as per example 2 using 81.9 g of hydroxyl-terminated polybutadiene and 18.0 g of 3-isocyanatopropyltriethoxysilane.

[0095] Viscosity (20? C.): 8.5 Pa*s

Example 2B

[0096] Produced as per example 2 using 83.4 g of hydroxyl-terminated polybutadiene and 16.6 g of 3-isocyanatopropyltriethoxysilane.

[0097] Viscosity (20? C.): 9.4 Pa*s

Example 2C

[0098] Produced as per example 2 using 84.7 g of hydroxyl-terminated polybutadiene and 15.2 g of 3-isocyanatopropyltriethoxysilane.

[0099] Viscosity (20? C.): 8.8 Pa*s

Example 2D

[0100] Produced as per example 2 using 86.5 g of hydroxyl-terminated polybutadiene and 13.4 g of 3-isocyanatopropyltriethoxysilane.

[0101] Viscosity (20? C.): 8.7 Pa*s

Example 2E

[0102] Produced as per example 2 using 88.2 g of hydroxyl-terminated polybutadiene and 11.7 g of 3-isocyanatopropyltriethoxysilane.

[0103] Viscosity (20? C.): 8.5 Pa*s

Example 2F

[0104] Produced as per example 2 using 87.2 g of hydroxyl-terminated polybutadiene and 12.7 g of 3-isocyanatopropyltriethoxysilane.

[0105] Viscosity (20? C.): 8.2 Pa*s

Example 2G

[0106] Produced as per example 2 using 89.5 g of hydroxyl-terminated polybutadiene and 10.5 g of 3-isocyanatopropyltriethoxysilane.

[0107] Viscosity (20? C.): 8.2 Pa*s

Example 2H

[0108] Produced as per example 2 using 91.9 g of hydroxyl-terminated polybutadiene and 8.1 g of 3-isocyanatopropyltriethoxysilane.

[0109] Viscosity (20? C.): 8.5 Pa*s

Example 21

[0110] Produced as per example 2 using 94.4 g of hydroxyl-terminated polybutadiene and 5.5 g of 3-isocyanatopropyltriethoxysilane.

[0111] Viscosity (20? C.): 8.4 Pa*s

Example 2J

[0112] Produced as per example 2 using 97.1 g of hydroxyl-terminated polybutadiene and 2.8 g of 3-isocyanatopropyltriethoxysilane.

[0113] Viscosity (20? C.): 8.4 Pa*s

Example 3

[0114] In a typical reaction 94.43 g of a hydroxyl-terminated polybutadiene produced by anionic polymerization and 0.05 wt % of the catalyst (COSCAT 83 or DBTL) were initially charged under nitrogen into a three-necked round flask fitted with a dropping funnel and thermometer and heated to 60? C. Once the temperature had been reached 5.52 g of 3-isocyanatopropyltriethoxysilane were added via the dropping funnel with stirring and the reaction mixture was stirred for three hours. The end of the reaction was ascertained by determining the residual isocyanate content (NCO<0.1%) by titration.

[0115] GPC (PS Standard): M.sub.n=4.800 g/mol; M.sub.w=5.000 g/mol; D=1.04

[0116] Viscosity (20? C.): 27.8 Pa*s

Application Examples

Example 4: Rubber Mixtures I

[0117] The formulation used for the rubber mixtures is specified in table 1 below. In this table, the unit phr means parts by weight based on 100 parts of the crude rubber employed. The silane-modified polybutadiene according to the invention is employed as an additive in the inventive rubber mixtures in varying amounts.

TABLE-US-00001 TABLE 1 amount amount amount [phr] [phr] [phr] amount inv. rubber inv. rubber inv. rubber [phr] mixture II mixture III mixture IV ref. rubber comprising comprising comprising substance mixture I inv. example 1 inv. example 1 inv. example 1 1st stage NR SMR 100.0 100.0 100.0 100.0 10.sup.a silica.sup.b 55.0 55.0 55.0 55.0 fatty acid.sup.c 3.0 3.0 3.0 3.0 ZnO.sup.d 3.0 3.0 3.0 3.0 6PPD.sup.e 1.0 1.0 1.0 1.0 TMQ.sup.f 1.0 1.0 1.0 1.0 anti- 1.0 1.0 1.0 1.0 ozonant wax.sup.g Si 266.sup.h 5.0 5.0 5.0 5.0 example 1 2.5 5.0 7.5 2nd stage stage 1 batch 3rd stage stage 2 batch DPG-80.sup.i 2.5 2.5 2.5 2.5 CBS.sup.j 1.0 1.0 1.0 1.0 sulphur.sup.k 2.0 2.0 2.0 2.0 Substances used: .sup.aNR TSR: SMR 10 from Nordmann, Rassmann GmbH (TSR = Technically Specified Rubber; SMR = Standard Malaysian Rubber) .sup.bsilica: ULTRASIL? 7000 GR from Evonik Industries AG. .sup.cEDENOR ST1 GS fatty acid mixture, Caldic Deutschland Chemie B.V. .sup.dZnO: RS RAL 844 C ZnO from Arnsperger Chemikalien GmbH. .sup.e6PPD: Vulkanox 4020/LG N-(1,3-dimethylbutyl)-N-phenyl-p-phenylene diamine from Rhein Chemie Rheinau GmbH. .sup.fTMQ: Vulkanox HS/LG polymerized 2,2,4-trimethyl-1,2-dihydroquinoline from Rhein Chemie Rheinau GmbH. .sup.gantiozonant wax: Protektor G3108 from Paramelt B.V. .sup.hSi 266?: bis(triethoxysilylpropyl)disulphide from Evonik Industries AG. .sup.iDPG-80: Rhenogran? DPG-80 mixture of 80% N,N-diphenylguanidine and of 20% elastomeric carrier and dispersant from Rhein Chemie GmbH. .sup.jCBS: CZ/EG-C N-cyclohexyl-2-benzothiazolesulphenamide from Rhein Chemie Rheinau GmbH. .sup.ksulphur: Mahlschwefel 80/90? from Solvay & CPC Barium Strontium GmbH & Co. KG.

[0118] The mixtures are prepared in three stages in a 1.51 internal mixer (E-type) at a batch temperature of 150? C. in accordance with the mixing instructions in table 2.

TABLE-US-00002 TABLE 2 stage 1 settings mixing unit HF mixing group GmbH; type GK 1.5 E fill level 0.58 speed 70 rpm ram pressure 5.5 bar flow temp. 70? C. mixing operation 0 to 0.5 min SMR 10 0.5 min ? ULTRASIL 7000 GR, Si 266, ZnO, fatty acid, inventive silane-modified polybutadiene (if present) 0.5 to 1.5 min mix 1.5 min vent and purge 1.5 to 2.5 min ? ULTRASIL 7000 GR, antiozonant wax, 6PPD, TMQ 2.5 to 4 min mix at 150? C., optionally varying speed 4 min vent and purge 4 to 5.5 min mix at 150? C., optionally varying speed 5.5 min discharge and form milled sheet on laboratory mixing roll mill for 45 s (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 4 mm, flow temperature 60? C.) 24 h storage at room temperature stage 2 settings mixing unit as in stage 1 except fill level 0.55 speed 80 rpm ram pressure 5.5 bar flow temp. 80? C. mixing operation 0 to 1 min break up stage 1 batch 1 to 3 min mix at 150? C., optionally varying speed 3 min discharge and form milled sheet on laboratory mixing roll mill for 45 s (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 4 mm, flow temperature 60? C.) 24 h storage at room temperature stage 3 settings mixing unit as in stage 1 except fill level 0.52 speed 60 rpm flow temp. 50? C. mixing operation 0 to 2 min break up stage 2 batch, accelerant and sulphur, mix at 100? C., optionally varying speed 2 min discharge and form milled sheet on laboratory mixing roll mill for 20 s, then, over a further 40 s, cut and fold over 3* to the left, 3* to the right and roll 3* with a narrow roll gap (3 mm) and then draw off a milled sheet. (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 3-4 mm, flow temperature 80? C.)

[0119] The general process for producing rubber mixtures and vulcanizates thereof is described in Rubber Technology Handbook, W. Hofmann, Hanser Verlag 1994.

[0120] Vulcanization is effected at a temperature of 150? C. in a typical vulcanizing press with a holding pressure of 120 bar after t.sub.95%. The t.sub.95% time was determined by moving disc rheometer (rotorless vulcameter) to DIN 53529/3 at 150? C.

[0121] The rubber testing is effected in accordance with the test methods specified in table 3.

[0122] Table 4 reports the rubber data for the vulcanizates.

TABLE-US-00003 TABLE 3 physical testing standard/conditions DIN abrasion ISO 4649 abrasion [mm].sup.3) ring tensile test at 23? C. ISO 37 300% modulus/MPa Shore A hardness at 23? C. ISO 7619-1 Shore A hardness/SH ball rebound, 60? C. DIN EN ISO 8307 rebound resilience/% fall height 500 mm, steel ball d = 19 mm, 28 g viscoelastic properties of the RPA 2000 Rubber Process vulcanizate at 60? C. Analyzer (Alpha Technologies), maximum loss factor tan ? strain sweep, 1.7 Hz, 0.28%-42% elongation; see RPA 2000 Operators Manual, Alpha Technologies, February 1997 viscoelastic properties at 60? C. ISO 4664-1 loss factor tan ? 16 Hz, initial force 50 N and amplitude force 25 N, heat treatment time 5 min, parameters recorded after 30 s testing time

TABLE-US-00004 TABLE 4 inv. rubber inv. rubber inv. rubber mixture II mixture III mixture IV ref. rubber comprising comprising comprising vulcanizate results: mixture I inv. example 1 inv. example 1 inv. example 1 DIN abrasion 153 143 136 134 abrasion [mm].sup.3) ring tensile test at 23? C. 12.2 12.6 14.1 14.6 300% modulus/MPa Shore A hardness 68 66 67 69 Shore A hardness/SH ball rebound 71.9 72.7 75.6 77.3 rebound resilience at 60? C./% viscoelastic properties, 0.187 0.143 0.116 0.100 60? C., Rubber Process Analyzer (RPA), strain sweep, 1.7 Hz, 0.28%- 42% elongation maximum loss factor tan ?/ viscoelastic properties 0.072 0.064 0.049 0.042 at 60? C., 16 Hz, initial force 50 N, ampl. force 25 N loss factor tan ?/

[0123] The inventive rubber mixtures II-IV show improved rolling resistance (lower tan ? values and higher rebound resiliences at 60? C.) compared to the reference rubber mixture I. This positive effect increases as the amount of inventive silane-modified polybutadiene increases from mixture II to mixture IV. Addition of inventive silane-modified polybutadiene further achieves improved reinforcing characteristics (300% modulus) and lower abrasion (DIN abrasion).

Example 5: Rubber Mixtures II

[0124] The formulation used for the rubber mixtures is specified in table 5 below. In this table, the unit phr means parts by weight based on 100 parts of the crude rubber employed. In the inventive rubber mixtures the silane-modified polybutadienes according to the invention are employed as an additive and partially replace the sulphur silane.

TABLE-US-00005 TABLE 5 Amount Amount [phr] [phr] amount inv. rubber inv. rubber [phr] mixture VI mixture VII ref. rubber comprising comprising substance mixture V inv. example 1 inv. example 2 1st stage NR SMR 10.sup.a 100.0 100.0 100.0 silica.sup.b 55.0 55.0 55.0 fatty acid.sup.c 3.0 3.0 3.0 ZnO.sup.d 3.0 3.0 3.0 6PPD.sup.e 1.0 1.0 1.0 TMQ.sup.f 1.0 1.0 1.0 antiozonant wax.sup.g 1.0 1.0 1.0 Si 266.sup.h 5 4 4 example 1 7.5 example 2 7.5 2nd stage stage 1 batch 3rd stage stage 2 batch DPG-80.sup.i 2.5 2.5 2.5 CBS.sup.j 1.0 1.0 1.0 sulphur.sup.k 2.0 2.0 2.0 Substances used: .sup.aNR TSR: SMR 10 from Nordmann, Rassmann GmbH (TSR = Technically Specified Rubber; SMR = Standard Malaysian Rubber) .sup.bsilica: ULTRASIL? 7000 GR from Evonik Industries AG. .sup.cfatty acid: EDENOR ST1 GS fatty acid mixture, Caldic Deutschland Chemie B.V. .sup.dZnO: RS RAL 844 C ZnO from Arnsperger Chemikalien GmbH. .sup.e6PPD: Vulkanox 4020/LG N-(1,3-dimethylbutyl)-N-phenyl-p-phenylene diamine from Rhein Chemie Rheinau GmbH. .sup.fTMQ: Vulkanox HS/LG polymerized 2,2,4-trimethyl-1,2-dihydroquinoline from Rhein Chemie Rheinau GmbH. .sup.gantiozonant wax: Protektor G3108 from Paramelt B.V. .sup.hSi 266?: bis(triethoxysilylpropyl)disulphide from Evonik Industries AG. .sup.iDPG-80: Rhenogran? DPG-80 mixture of 80% N,N-diphenylguanidine and of 20% elastomeric carrier and dispersant from Rhein Chemie GmbH. .sup.jCBS: CZ/EG-C N-cyclohexyl-2-benzothiazolesulphenamide from Rhein Chemie Rheinau GmbH. .sup.ksulphur: Mahlschwefel 80/90? from Solvay & CPC Barium Strontium GmbH & Co. KG.

[0125] The mixtures are prepared in three stages in a 1.51 internal mixer (E-type) at a batch temperature of 150? C. in accordance with the mixing instructions in table 6.

TABLE-US-00006 TABLE 6 stage 1 settings mixing unit HF mixing group GmbH; type GK 1.5 E fill level 0.65 speed 70 rpm ram pressure 5.5 bar flow temp. 70? C. mixing operation 0 to 0.5 min SMR 10 0.5 min ? ULTRASIL 7000 GR, Si 266, ZnO, fatty acid, inventive silane-modified polybutadiene (if present) 0.5 to 1.5 min mix 1.5 min vent and purge 1.5 to 2.5 min ? ULTRASIL 7000 GR, antiozonant wax, 6PPD, TMQ 2.5 to 4 min mix at 150? C., optionally varying speed 4 min vent 4 to 5.5 min mix at 150? C., optionally varying speed 5.5 min discharge and form milled sheet on laboratory mixing roll mill for 45 s (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 4 mm, flow temperature 60? C.) 24 h storage at room temperature stage 2 settings mixing unit as in stage 1 except fill level 0.62 speed 80 rpm ram pressure 5.5 bar flow temp. 80? C. mixing operation 0 to 1 min break up stage 1 batch 1 to 3 min mix at 150? C., optionally varying speed 3 min discharge and form milled sheet on laboratory mixing roll mill for 45 s (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 4 mm, flow temperature 60? C.) 4 h storage at room temperature stage 3 settings mixing unit as in stage 1 except fill level 0.59 speed 60 rpm flow temp. 50? C. mixing operation 0 to 2 min break up stage 2 batch, accelerant and sulphur, mix at 100? C., optionally varying speed 2 min discharge and form milled sheet on laboratory mixing roll mill for 20 s, then, over a further 40 s: cut and fold over 3* to the left, 3* to the right and roll 3* with a narrow roll gap (3 mm) and then draw off a milled sheet. (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 3-4 mm, flow temperature 80? C.)

[0126] The general process for producing rubber mixtures and vulcanizates thereof is described in Rubber Technology Handbook, W. Hofmann, Hanser Verlag 1994.

[0127] Vulcanization is effected at a temperature of 150? C. in a typical vulcanizing press with a holding pressure of 120 bar after t.sub.95%. The t.sub.95% time is determined by moving disc rheometer (rotorless vulcameter) to DIN 53529/3 at 150? C.

[0128] The rubber testing is effected in accordance with the test methods specified in table 3.

[0129] Table 7 reports the rubber data for the vulcanizates.

TABLE-US-00007 TABLE 7 inv. rubber inv. rubber mixture VI mixture VII ref. rubber comprising comprising vulcanizate results: mixture V Inv. example 1 inv. example 2 DIN abrasion 129 114 119 abrasion [mm].sup.3) ring tensile test at 12.6 13.0 13.9 23? C. 300% modulus/ MPa Shore A hardness 62 62 64 Shore A hardness/ SH ball rebound 71.2 76.8 76.6 rebound resilience at 60? C./% viscoelastic 0.137 0.086 0.092 properties, 60? C., Rubber Process Analyzer (RPA), strain sweep, 1.7 Hz, 0.28%-42% elongation maximum loss factor tan ?/ viscoelastic 0.067 0.055 0.051 properties at 60? C., 16 Hz, initial force 50 N, ampl. force 25 N loss factor tan ?/

[0130] The inventive rubber mixtures VI-VII show improved rolling resistance (lower tan ? values and higher rebound resiliences at 60? C.) compared to the reference rubber mixture V. Addition of inventive silane-modified polybutadiene further achieves improved reinforcing characteristics (300% modulus) and lower abrasion (DIN abrasion).

Example 6: Rubber Mixtures III

[0131] The formulations used for the rubber mixtures are specified in table 8 below. In this table, the unit phr means parts by weight based on 100 parts of the crude rubber employed. In the inventive rubber mixtures the silane-modified polybutadienes according to the invention are employed as an additive and partially replace the sulphur silane.

TABLE-US-00008 TABLE 8 amount [phr] ref. amount amount amount amount amount rubber [phr] [phr] [phr] [phr] [phr] mixture inv. inv. inv. inv. inv. IX rubber rubber rubber rubber rubber amount comprising mixture mixture mixture mixture mixture [phr] comparative X XI XII XIII XIV ref. example comprising comprising comprising comprising comprising rubber hydroxyl- inv. inv. inv. inv. inv. mixture terminated example example example example example substance VIII polybutadiene 2A: 2B 2C 2D 2E 1st stage NR SMR 10.sup.a 100.0 100.0 100.0 100.0 100.0 100.0 100.0 silica.sup.b 55.0 55.0 55.0 55.0 55.0 55.0 55.0 fatty acid.sup.c 3.0 3.0 3.0 3.0 3.0 3.0 3.0 ZnO.sup.d 3.0 3.0 3.0 3.0 3.0 3.0 3.0 6PPD.sup.e 1.0 1.0 1.0 1.0 1.0 1.0 1.0 TMQ.sup.f 1.0 1.0 1.0 1.0 1.0 1.0 1.0 antiozonant 1.0 1.0 1.0 1.0 1.0 1.0 1.0 wax.sup.g Si 266.sup.h 5 4 4 4 4 4 4 hydroxyl- 7.5 terminated polybutadiene .sup.i example 2A 7.5 example 2B 7.5 example 2C 7.5 example 2D 7.5 example 2E 7.5 2nd stage stage 1 batch 3rd stage Stage 2 batch DPG-80.sup.j 2.5 2.5 2.5 2.5 2.5 2.5 2.5 CBS.sup.k 1.0 1.0 1.0 1.0 1.0 1.0 1.0 sulphur.sup.l 2.0 2.0 2.0 2.0 2.0 2.0 2.0 .sup.aNR TSR: SMR 10 from Nordmann, Rassmann GmbH (TSR = Technically Specified Rubber; SMR = Standard Malaysian Rubber) .sup.bsilica: ULTRASIL? 7000 GR from Evonik Industries AG. .sup.cfatty acid: EDENOR ST1 GS fatty acid mixture, Caldic Deutschland Chemie B.V. .sup.dZnO: RS RAL 844 C ZnO from Arnsperger Chemikalien GmbH. .sup.e6PPD: Vulkanox 4020/LG N-(1,3-dimethylbutyl)-N-phenyl-p-phenylene diamine from Rhein Chemie Rheinau GmbH. .sup.fTMQ: Vulkanox HS/LG polymerized 2,2,4-trimethyl-1,2-dihydroquinoline from Rhein Chemie Rheinau GmbH. .sup.gantiozonant wax: Protektor G3108 from Paramelt B.V. .sup.hSi 266?: bis(triethoxysilylpropyl)disulphide from Evonik Industries AG. # .sup.i Hydroxyl-terminated polybutadiene (POLYVEST HT) from Evonik .sup.jDPG-80: Rhenogran? DPG-80 mixture of 80% N,N-diphenylguanidine and of 20% elastomeric carrier and dispersant from Rhein Chemie GmbH. .sup.kCBS: CZ/EG-C N-cyclohexyl-2-benzothiazolesulphenamide from Rhein Chemie Rheinau GmbH. .sup.lsulphur: Mahlschwefel 80/90? from Solvay & CPC Barium Strontium GmbH & Co. KG

[0132] The mixtures are prepared in three stages in a 1.51 internal mixer (E-type) at a batch temperature of 150? C. in accordance with the mixing instructions in table 9.

TABLE-US-00009 TABLE 9 stage 1 settings mixing unit HF mixing group GmbH; type GK 1.5 E fill level 0.65 speed 70 rpm ram pressure 5.5 bar flow temp. 70? C. mixing operation 0 to 0.5 min SMR 10 0.5 min ? ULTRASIL 7000 GR less 20 g, Si 266, ZnO, fatty acid, inventive silane-modified polybutadiene (if present) mixed directly prior to addition with 20 g of ULTRASIL 7000 GR from the first half of the ULTRASIL 7000 GR 0.5 to 1.5 min mix 1.5 min vent and purge 1.5 to 2.5 min ? ULTRASIL 7000 GR, antiozonant wax, 6PPD, TMQ 2.5 min vent and purge 2.5 to 4.0 min mix at 150? C., optionally varying speed 4.0 min vent 3 to 5.5 min mix at 150? C., optionally varying speed 5.5 min discharge and form milled sheet on laboratory mixing roll mill for 45 s (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 4 mm, flow temperature 60? C.) 24 h storage at room temperature stage 2 settings mixing unit as in stage 1 except fill level 0.62 speed 80 rpm flow temp. 80? C. mixing operation 0 to 1.0 min break up stage 1 batch 1.0 to 3.0 min mix at 150? C., optionally varying speed 3.0 min discharge and form milled sheet on laboratory mixing roll mill for 45 s (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 4 mm, flow temperature 60? C.) 24 h storage at room temperature stage 3 settings mixing unit as in stage 1 except fill level 0.59 speed 60 rpm flow temp. 50? C. mixing operation 0 to 2.0 min break up stage 2 batch, accelerant and sulphur, mix at 100? C., optionally varying speed 2.0 min discharge and form milled sheet on laboratory mixing roll mill for 20 s, then, over a further 40 s: cut and fold over 3* to the left, 3* to the right and roll 3* with a narrow roll gap (3 mm) and then draw off a milled sheet. (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 3-4 mm, flow temperature 80? C.)

[0133] The general process for producing rubber mixtures and vulcanizates thereof is described in Rubber Technology Handbook, W. Hofmann, Hanser Verlag 1994.

[0134] Vulcanization is effected at a temperature of 150? C. in a typical vulcanizing press with a holding pressure of 120 bar after t.sub.95%. The t.sub.95% time was determined by moving disc rheometer (rotorless vulcameter) to DIN 53529/3 at 150? C.

[0135] The rubber testing is effected in accordance with the test methods specified in table 3.

[0136] Table 10 reports the rubber data for the vulcanizates.

TABLE-US-00010 TABLE 10 ref. rubber mixture inv. inv. inv. inv. IX inv. rubber rubber rubber rubber comprising rubber mixture mixture mixture mixture comparative mixture X XI XII XIII XIV ref. example comprising comprising comprising comprising comprising rubber hydroxyl- Inv. inv. inv. inv. Inv. mixture terminated example example example example example vulcanizate results: VIII polybutadiene 2A 2B 2C 2D 2E DIN abrasion 124 127 113 112 111 105 113 abrasion [mm].sup.3) ring tensile test at 12.1 8.6 13.6 12.6 12.8 11.7 11.6 60? C. 300% modulus/MPa Shore A hardness 62 57 64 62 64 62 62 Shore A hardness/SH ball rebound 68.5 70.7 73.8 72.9 74.5 73.1 72.5 rebound resilience at 60? C./% viscoelastic 0.147 0.114 0.098 0.096 0.095 0.100 0.103 properties, 60? C., Rubber Process Analyzer (RPA), strain sweep, 1.7 Hz, 0.28%-42% elongation maximum loss factor tan ?/ viscoelastic properties 0.077 0.069 0.053 0.052 0.051 0.055 0.055 at 60? C., 16 Hz, initial force 50 N, ampl. force 25 N loss factor tan ?/

[0137] The inventive rubber mixtures X to XIV show improved rolling resistance (lower tan ? values and higher rebound resiliences at 60? C.) and improved DIN abrasion compared to the reference rubber mixture VIII.

[0138] When the degree of silane modification of the polybutadiene is zero (reference rubber mixture IX) the advantages compared to the reference rubber mixture VIII are not present (DIN abrasion, 300% modulus) or markedly less pronounced (tan ? and rebound resilience at 60? C.).

Example 7: Rubber Mixtures IV

[0139] The formulations used for the rubber mixtures are specified in table 8 below. In this table, the unit phr means parts by weight based on 100 parts by weight of the crude rubber used. The silane-modified polybutadienes according to the invention are employed as an additive in the inventive rubber mixtures and replace the sulphur silane proportionately.

TABLE-US-00011 TABLE 11 amount amount amount amount amount amount [phr] [phr] [phr] [phr] [phr] [phr] inv. inv. inv. inv. inv. inv. rubber rubber rubber rubber rubber rubber amount mixture mixture mixture mixture mixture mixture [phr] XVI, XVII, XIII, XIX, XX, XXI, ref. comprising comprising comprising comprising comprising comprising rubber inv. inv. inv. inv. inv. inv. mixture example example example example example example substance XV 2F 2G 2H 2I 2J 3 1st stage NR SMR 10.sup.a 100.0 100.0 100.0 100.0 100.0 100.0 100.0 silica.sup.b 55.0 55.0 55.0 55.0 55.0 55.0 55.0 fatty acid.sup.c 3.0 3.0 3.0 3.0 3.0 3.0 3.0 ZnO.sup.d 3.0 3.0 3.0 3.0 3.0 3.0 3.0 6PPD.sup.e 1.0 1.0 1.0 1.0 1.0 1.0 1.0 TMQ.sup.f 1.0 1.0 1.0 1.0 1.0 1.0 1.0 antiozonant 1.0 1.0 1.0 1.0 1.0 1.0 1.0 wax.sup.g Si 266.sup.h 5 4 4 4 4 4 4 example 2E 7.5 example 2F 7.5 example 2G 7.5 example 2H 7.5 example 2I 7.5 example 3 7.5 2nd stage stage 1 batch 3rd stage stage 2 batch DPG-80.sup.j 2.5 2.5 2.5 2.5 2.5 2.5 2.5 CBS.sup.k 1.0 1.0 1.0 1.0 1.0 1.0 1.0 sulphur.sup.l 2.0 2.0 2.0 2.0 2.0 2.0 2.0 .sup.aNR TSR: SMR 10 from Nordmann, Rassmann GmbH (TSR = Technically Specified Rubber; SMR = Standard Malaysian Rubber). .sup.bsilica: ULTRASIL? 7000 GR from Evonik Industries AG. .sup.cfatty acid: EDENOR ST1 GS fatty acid mixture, Caldic Deutschland Chemie B.V. .sup.dZnO: RS RAL 844 C ZnO from Arnsperger Chemikalien GmbH. .sup.e6PPD: Vulkanox 4020/LG N-(1,3-dimethylbutyl)-N-phenyl-p-phenylene diamine from Rhein Chemie Rheinau GmbH. .sup.fTMQ: Vulkanox HS/LG polymerized 2,2,4-trimethyl-l,2-dihydroquinoline from Rhein Chemie Rheinau GmbH. .sup.gantiozonant wax: Protektor G3108 from Paramelt B.V. .sup.hSi 266?: bis(triethoxysilylpropyl)disulphide from Evonik Industries AG. .sup.i) hydroxyl-terminated polybutadiene (POLYVEST HT) from Evonik .sup.jDPG-80: Rhenogran? DPG-80 mixture of 80% N,N-diphenylguanidine and of 20% elastomeric carrier and dispersant from Rhein Chemie GmbH. .sup.kCBS: CZ/EG-C N-cyclohexyl-2-benzothiazolesulphenamide from Rhein Chemie Rheinau GmbH. .sup.lsulphur: Mahlschwefel 80/90? from Solvay & CPC Barium Strontium GmbH & Co. KG

[0140] The mixtures are prepared in three stages in a 1.51 internal mixer (E-type) at a batch temperature of 150? C. in accordance with the mixing instructions in table 9.

TABLE-US-00012 TABLE 12 stage 1 settings mixing unit HF mixing group GmbH; type GK 1.5 E fill level 0.65 speed 70 rpm ram pressure 5.5 bar flow temp. 70? C. Mixing process 0 to 0.5 min SMR 10 0.5 min ? ULTRASIL 7000 GR less 20 g, Si 266, ZnO, fatty acid, inventive silane-modified polybutadiene (if present) mixed directly prior to addition with 20 g of ULTRASIL 7000 GR from the first half of the ULTRASIL 7000 GR 0.5 to 1.5 min mix 1.5 min vent and purge 1.5 to 2.5 min ? ULTRASIL 7000 GR, antiozonant wax, 6PPD, TMQ 2.5 min vent and purge 2.5 to 4.0 min mix at 150? C., optionally varying speed 4.0 min vent 3 to 5.5 min mix at 150? C., optionally varying speed 5.5 min discharge and form milled sheet on laboratory mixing roll mill for 45 s (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 4 mm, flow temperature 60? C.) 24 h storage at room temperature stage 2 settings mixing unit as in stage 1 except fill level 0.62 speed 80 rpm flow temp 80? C. mixing operation 0 to 1.0 min break up stage 1 batch 1.0 to 3.0 min mix at 150? C., optionally varying speed 3.0 min discharge and form milled sheet on laboratory mixing roll mill for 45 s (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 4 mm, flow temperature 60? C.) 24 h storage at room temperature stage 3 settings mixing unit as in stage 1 except fill level 0.59 speed 60 rpm flow temp. 50? C. mixing operation 0 to 2.0 min break up stage 2 batch, accelerant and sulphur, mix at 100? C., optionally varying speed 2.0 min discharge and form milled sheet on laboratory mixing roll mill for 20 s, then, over a further 40 s: cut and fold over 3* to the left, 3* to the right and roll 3* with a narrow roll gap (3 mm) and then draw off a milled sheet. (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 3-4 mm, flow temperature 80? C.)

[0141] The general process for producing rubber mixtures and vulcanizates thereof is described in Rubber Technology Handbook, W. Hofmann, Hanser Verlag 1994.

[0142] Vulcanization is effected at a temperature of 150? C. in a typical vulcanizing press with a holding pressure of 120 bar after t.sub.95%. The t.sub.95% time was determined by moving disc rheometer (rotorless vulcameter) to DIN 53529/3 at 150? C.

[0143] The rubber testing is effected in accordance with the test methods specified in table 3.

[0144] Table 10 reports the rubber data for the vulcanizates.

TABLE-US-00013 TABLE 13 inv. inv. inv. inv. inv. inv. rubber rubber rubber rubber rubber rubber mixture mixture mixture mixture mixture mixture XVI, XVII, XIII, XIX, XX, XXI, ref. comprising comprising comprising comprising comprising comprising rubber inv. inv. inv. inv. inv. inv. mixture example example example example example example vulcanizate results: XV 2F 2G 2H 2I 2J 3 DIN abrasion 123 119 123 126 131 126 135 abrasion/mm.sup.3 ring tensile test at 8.6 8.4 8.4 8.0 7.5 7.2 8.0 60? C. 300% modulus/ MPa Shore A hardness 63 60 60 59 59 58 57 Shore A hardness/ SH ball rebound 69.2 72.5 71.9 70.6 69.1 68.9 75.5 rebound resilience at 60? C./% viscoelastic 0.127 0.117 0.106 0.104 0.108 0.111 0.078 properties, 60? C., Rubber Process Analyzer (RPA), strain sweep, 1.7 Hz, 0.28%-42% elongation maximum loss factor tan ?/ viscoelastic 0.080 0.065 0.061 0.066 0.068 0.068 0.055 properties at 60? C., 16 Hz, initial force 50 N, ampl. force 25 N loss factor tan ?/

[0145] The inventive rubber mixtures XVI to XXI show improved rolling resistance (lower tan ? values and higher rebound resiliences at 60? C.) compared to the reference rubber mixture XV.

[0146] When the degree of silane modification of the polybutadiene goes down the advantages compared to the reference rubber mixture XVI are not present (DIN abrasion, 300% modulus) or markedly less pronounced (tan ? and rebound resilience at 60? C.).

[0147] Rubber mixture XXI based on a polybutadiene which was produced by anionic polymerization and subsequently modified shows impaired rolling resistance compared to polybutadienes produced by free-radical polymerization (e.g. rubber mixtures XVI) and in some cases a lower hardness and a lower 300 modulus (higher DIN abrasion and lower Shore A hardness). These effects are amplified with an increasing degree of silanization (cf. ex. X-XIV).

Example 8: Rubber Mixtures V

[0148] The formulation used for the rubber mixtures is specified in table 11 below. In this table, the unit phr means parts by weight based on 100 parts by weight of the crude rubber used. The silane-modified polybutadiene according to the invention is employed as an additive in the inventive rubber mixture.

TABLE-US-00014 TABLE 14 Amount [phr] amount inv. rubber [phr] mixture XXIII ref. rubber comprising substance mixture XXII inv. example 1 1st stage NR SMR 10.sup.a 80.0 80.0 BR.sup.b 20.0 20.0 silica.sup.c 55.0 55.0 fatty acid.sup.d 3.0 3.0 ZnO.sup.e 3.0 3.0 6PPD.sup.f 1.0 1.0 TMQ.sup.g 1.0 1.0 antiozonant wax.sup.h 1.0 1.0 Si 266.sup.i 5 5 example 1 7.5 2nd stage stage 1 batch 3rd stage stage 2 batch DPG-80.sup.j 2.5 2.5 CBS.sup.k 1.0 1.0 sulphur.sup.l 2.0 2.0 Substances used: .sup.aNR TSR: SMR 10 from Nordmann, Rassmann GmbH (TSR = Technically Specified Rubber; SMR = Standard Malaysian Rubber). .sup.bBR: hoch-cisPolybutadien Kautschuk CB 24, from Lanxess AG. .sup.csilica: ULTRASIL? 7000 GR from Evonik Industries AG. .sup.dfatty acid: EDENOR ST1 GS fatty acid mixture, Caldic Deutschland Chemie B.V. .sup.eZnO: RS RAL 844 C ZnO from Arnsperger Chemikalien GmbH. .sup.f6PPD: Vulkanox 4020/LG N-(l,3-dimethylbutyl)-N-phenyl-p-phenylene diamine from Rhein Chemie Rheinau GmbH. .sup.gTMQ: Vulkanox HS/LG polymerized 2,2,4-trimethyl-1,2-dihydroquinoline from Rhein Chemie Rheinau GmbH. .sup.hantiozonant wax: Protektor G3108 from Paramelt B.V. .sup.hSi 266?: bis(triethoxysilylpropyl)disulphide from Evonik Industries AG. .sup.jDPG-80: Rhenogran? DPG-80 mixture of 80% N,N-diphenylguanidine and of 20% elastomeric carrier and dispersant from Rhein Chemie GmbH. .sup.kCBS: CZ/EG-C N-cyclohexyl-2-benzothiazolesulphenamide from Rhein Chemie Rheinau GmbH. .sup.lsulphur: Mahlschwefel 80/90? from Solvay & CPC Barium Strontium GmbH & Co. KG

[0149] The mixtures are prepared in three stages in a 1.51 internal mixer (E-type) at a batch temperature of 150? C. in accordance with the mixing instructions in table 12.

TABLE-US-00015 TABLE 15 stage 1 settings mixing unit HF mixing group GmbH; type GK 1.5 E fill level 0.65 speed 70 rpm ram pressure 5.5 bar flow temp. 70? C. Mixing process 0 to 0.5 min SMR 10, BR CB 24 0.5 min ? ULTRASIL 7000 GR, Si 266, ZnO, fatty acid, inventive silane-modified polybutadiene (if present) 0.5 to 1.0 min mix 1.0 min vent and purge 1.0 to 2.0 min ? ULTRASIL 7000 GR, antiozonant wax, 6PPD, TMQ 2.0 to 3 min mix at 150? C., optionally varying speed 3 min vent 3 to 5 min mix at 150? C., optionally varying speed 5 min discharge and form milled sheet on laboratory mixing roll mill for 45 s (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 4 mm, flow temperature 60? C.) 24 h storage at room temperature stage 2 settings mixing unit as in stage 1 except fill level 0.62 mixing operation 0 to 1 min break up stage 1 batch 1 to 3 min mix at 150? C., optionally varying speed 3 min discharge and form milled sheet on laboratory mixing roll mill for 45 s (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 4 mm, flow temperature 60? C.) 24 h storage at room temperature stage 3 settings mixing unit as in stage 1 except fill level 0.59 speed 50 rpm flow temp. 50? C. mixing operation 0 to 2 min break up stage 2 batch, accelerant and sulphur, mix at 100? C., optionally varying speed 2 min discharge and form milled sheet on laboratory mixing roll mill for 20 s, then, over a further 40 s: cut and fold over 3* to the left, 3* to the right and roll 3* with a narrow roll gap (3 mm) and then draw off a milled sheet. (laboratory roll mill: diameter 250 mm, length 190 mm, roll gap 3-4 mm, flow temperature 80? C.)

[0150] The general process for producing rubber mixtures and vulcanizates thereof is described in Rubber Technology Handbook, W. Hofmann, Hanser Verlag 1994.

[0151] Vulcanization is effected at a temperature of 150? C. in a typical vulcanizing press with a holding pressure of 120 bar after t.sub.95%. The t.sub.95% time was determined by moving disc rheometer (rotorless vulcameter) to DIN 53529/3 at 150? C.

[0152] The rubber testing is effected in accordance with the test methods specified in table 3.

[0153] Table 13 reports the rubber data for the vulcanizates.

TABLE-US-00016 TABLE 16 inv. rubber mixture XXIII ref. rubber comprising vulcanizate results: mixture XXII inv. example 1 DIN abrasion 113 105 abrasion/mm.sup.3) ring tensile test at 23? C. 8.7 11.3 300% modulus/MPa Shore A hardness 63 65 Shore A hardness/SH ball rebound 72.1 76.0 rebound resilience at 60? C./% viscoelastic properties, 60? C., Rubber Process Analyzer (RPA), strain sweep, 1.7 Hz, 0.28%- 42% elongation 0.148 0.108 maximum loss factor tan ?/ viscoelastic properties at 0.064 0.047 60? C., 16 Hz, initial force 50 N, ampl. force 25 N loss factor tan ?/

[0154] The inventive rubber mixture XXIII shows improved rolling resistance (lower tan ? values and higher rebound resiliences at 60? C.) compared to the reference rubber mixture XXII. Addition of inventive silane-modified polybutadiene further achieves improved reinforcing characteristics (300% modulus) and lower abrasion (DIN abrasion).

[0155] Rubber Mixture Summary

[0156] It has been shown that addition of silane-modified polybutadienes to the typical rubber formulations known to those skilled in the art can markedly improve the core properties of tires, in particular abrasion and rolling resistance. This applies both to natural-rubber-based tires (examples 4-7) and to those based on a mixture of natural rubber and butyl rubber (example 8). This applies in particular to silane-modified polybutadienes based on free-radically-based polybutadienes as is shown inter alia by comparison of the DIN abrasion, 300 modulus and Shore A hardness for the rubber mixtures X and XXI. The polybutadienes produced by free-radical polymerization further show a markedly lower viscosity which facilitates both handling and processability.