Europaisches Patentamt (19) European Patent Office Office europeenpeen des brevets EP 0 573 893 B1
(12) EUROPEAN PATENT SPECIFICATION
(45) Date of publication and mention (51) intci.e: C08F 236/10, C08F 4/48 of the grant of the patent: 22.01.1997 Bulletin 1997/04
(21) Application number: 93108898.3
(22) Date of filing: 03.06.1993
(54) Butadiene copolymer Butadien-Copolymer Copolymere de butadiene
(84) Designated Contracting States: • Kizuku, Wakatsuki DE FR GB IT NL Ichihara-shi, Chiba-ken (JP) • Mitsuji, Tsuji (30) Priority: 10.06.1992 JP 150432/92 Ichihara-shi, Chiba-ken (JP) • Yuichi, Saito (43) Date of publication of application: Kobe-shi, Hyogo-ken (JP) 15.12.1993 Bulletin 1993/50 (74) Representative: Turk, Gille, Hrabal, Leifert (73) Proprietor: SUMITOMO CHEMICAL COMPANY Brucknerstrasse 20 LIMITED 40593 Dusseldorf (DE) Osaka-shi, Osaka 541 (JP) (56) References cited: (72) Inventors: EP-A- 0 153 697 GB-A-2 160 207 • Keisaku, Yamamoto Ichihara-shi, Chiba-ken (JP)
DO CO O) 00 CO Is- Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice the Patent Office of the Notice of shall be filed in o to European opposition to European patent granted. opposition a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. a. 99(1) European Patent Convention). LU
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Description
The present invention relates to a butadiene copolymer, and more particularly to a butadiene copolymer suitable for use in tires, which is remarkably improved in processability with keeping resilience, wet grip property, abrasion 5 resistance and mechanical properties on high levels. A rubber well known as a rubber for tires is an emulsion styrene-butadiene copolymer prepared by an emulsion polymerisation. However, this copolymer has the disadvantage of being poor in resilience and, therefore, it is not pref- erable from the viewpoint of energy saving. Natural rubber, polyisoprene rubber and high-cis polybutadiene rubber are known as rubbers having a good resil- 10 ience. However, these rubbers are poor in wet grip property, and accordingly are not preferable from the viewpoint of running stability on wet roads. As a rubber having both good resilience and good wet grip property, there is known a rubber prepared by polym- erizing butadiene alone, or butadiene and styrene, in a hydrocarbon solvent in the presence of an organolithium com- pound as the polymerization initiator and a Lewis base such as an ether compound or a tertiary amine as an agent for is controlling microstructure. However, this rubber has the deficiency that the processability is insufficient. In order to improve the processability, it is also proposed to convert the polymer into a branched polymer by acting a tri- or tetraf unc- tional coupling agent on the active ends of the polymer. However, the processability is not sufficiently improved even by this method. In particular, in case of processing the rubber by a method using a large amount of a filler which is adopted in producing automobile tires superior in high speed running characteristics, the processability is unsatisfac- 20 tory. Abrasion resistance and mechanical properties are also required as the characteristics of rubbers for tire use in addition to the above-mentioned resilience, wet grip property and processability. However, any rubber which satisfies all of these characteristics, has not been proposed. It is an object of the present invention to provide a rubber suitable for use in tires and having excellent general 25 characteristics required for tire use. A further object of the present invention is to provide a butadiene copolymer suitable as a tire rubber, which is remarkably improved in processability with keeping resilience, wet grip property, abrasion resistance and mechanical properties on high levels. A still further object of the present invention is to provide a process for preparing the above-mentioned butadiene 30 copolymer. These and other objects of the present invention will become apparent from the description hereinafter. In accordance with the present invention, there is provided a butadiene copolymer prepared by a process which comprises copolymerizing a mixture of butadiene and a polyvinyl aromatic compound or a mixture of butadiene, styrene and a polyvinyl aromatic compound in a hydrocarbon solvent in the presence of an organolithium compound as a 35 polymerization initiator and subjecting the resulting copolymer having lithium at the polymer end to a coupling reaction with a trifunctional or tetrafunctional coupling agent, said butadiene copolymer satisfying the following conditions (a) to (d):
(a) the content of styrene is at most 50 % by weight, 40 (b) the content of vinyl bonds in the butadiene portion is from 10 to 90 % by weight, (c) the molecular weight distribution curve obtained by a high performance liquid chromatography has at least three peaks, and 5 to 60 % by weight of all the polymer chains have a molecular weight which is at least 5 times the molecular weight in terms of standard polystyrene corresponding to the peak appearing on the lowest molecular weight side of the chromatogram, and 45 (d) the Mooney viscosity (ML1+4, 100°C ) is from 30 to 200.
The copolymerization is carried out according to a known living anionic polymerization procedure. Examples of the hydrocarbon solvent used in the polymerization are, for instance, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, aliphatic hydrocarbons such as hexane and heptane, and alicyclic so hydrocarbons such as cyclopentane, cyclohexane and methylcyclohexane. Organolithium compounds known as anionic polymerization initiators of one end initiation type or both ends initi- ation type can be used. Representative examples are, for instance, ethyllithium, propyllithium, butyllithium, amyllithium, trimethylenedilithium, tetramethylenedilithium, hexyllithium, cyclohexyllithium, phenyllithium, tolyllithium and naphthyl- lithium. 55 Examples of the polyvinyl aromatic compound used in the present invention are, for instance, divinylbenzene, 1 ,2,4-trivinylbenzene, 1 ,3-divinylnaphthalene, 1 ,8-divinylnaphthalene, 1, 2-divinyl-3, 4-dimethylbenzene, 2, 4-divinyl- biphenyl, 3,5,4'-trivinylbiphenyl and 1 ,3,5-trivinylbenzene. The polyvinyl aromatic compounds may be used alone or in admixture thereof. Among them, divinylbenzene is preferable from the viewpoint of easiness in industrial availability,
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and a mixture of the ortho, meta and para compounds which is industrially available, can be used. Known trifunctional ortetrafunctional coupling agents can be used in the present invention. Examples of the cou- pling agent are, for instance, silicon tetrachloride, silicon tetrabromide, silicon tetraiodide, germanium tetrachloride, tin tetrachloride, methyltrichlorosilane, butyl tin trichloride, bistrichlorosilylethane and bistrichloroethane. The coupling 5 agents may be used alone or in admixture thereof. Silicon tetrachloride and tin tetrachloride are preferred from the viewpoints of reactivity and industrial availability. The butadiene copolymers of the present invention contain units derived from butadiene, units derived from the polyvinyl aromatic compound and optionally units derived from styrene. The content of the styrene units in the copol- ymers is at most 50 % by weight, whereby an elasticity as a rubber is secured. 10 The content of vinyl bonds in the butadiene moiety of the butadiene copolymers is from 10 to 90 % by weight, preferably from 20 to 70 % by weight. The copolymers outside the above range are difficult to industrially produce. The content of cis-1 ,4 bonds in the butadiene moiety of the copolymers is usually from 5 to 40 % by weight. Also, the content of trans-1 , 4 bonds in the butadiene moiety is usually from 10 to 60 % by weight. The molecular weight distribution curve of the butadiene copolymer of the present invention obtained by a high is performance liquid chromatography, wherein the axis of ordinates is weight fraction and the axis of abscissas is mo- lecular weight, has at least three peaks. In the region of molecular weight of not less than 1 00,000 in terms of standard polystyrene, it is necessary that the proportion of high molecular weight polymer chains having a molecular weight which is equal to 5 times or more the molecular weight in terms of standard polystyrene corresponding to the top of a peak which appears on the lowest molecular weight side of the chromatogram, is from 5 to 60 % by weight, preferably 20 10 to 40% by weight, based on the entire butadiene copolymer. When the content of the above-defined higher molecular weight polymer chains in the butadiene copolymer is too large or is too small, effect on the processability according to the present invention is not exhibited. The Mooney viscosity (ML1+4, 100°C ) of the butadiene copolymer is from 30 to 200, preferably 50 to 150. When the Mooney viscosity is more than the above range, the state of mixing in the preparation of a rubber composition by 25 mixing the copolymer with additives is deteriorated. When the Mooney viscosity is less than the above range, the resilience characteristic is deteriorated. The butadiene copolymer of the present invention may be an oil extended butadiene copolymer containing at most 1 00 parts by weight of an oil extender per 1 00 parts by weight of the copolymer. The oil extended butadiene copolymer is superior in workability in the case where a large amount of a process oil must be added in the preparation of rubber 30 compositions. The elastomeric butadiene copolymer of the present invention is suitably prepared by a process which comprises copolymerising butadiene, a polyvinyl aromatic compound and optionally styrene in a hydrocarbon solvent in the pres- ence of an organolithium compound as a polymerization initiator to produce a copolymer having lithium at either or both polymer chain ends, adding a trifunctional or tetrafunctional coupling agent to the reaction mixture, and carrying 35 out the coupling reaction. A Lewis basic compound may be used in the polymerisation in order to control the content of vinyl bonds in the butadiene moiety of the produced copolymer. Various kinds of Lewis basic compounds can be used, but ether com- pounds and tertiary amine compounds are preferred from the viewpoint of their availability in industrially practicing the invention. Examples of the ether compounds are, for instance, cyclic ethers such as tetrahydrofuran, tetrahydropyran 40 and 1 , 4-dioxane; aliphatic monoethers such as diethyl ether and dibutyl ether; aliphatic polyethers such as ethyleneg- lycol dimethyl ether, ethyleneglycol diethyl ether, ethyleneglycol dibutyl ether, diethyleneglycol diethyl ether and dieth- yleneglycol dibutyl ether; aromatic ethers such as diphenyl ether and anisole. Examples of the tertiary amine com- pounds are, for instance, triethylamine, tripropylamine, tributylamine, and other compounds such as N,N, N', N'-te- tramethylethylenediamine, N,N-diethylaniline, pyridine and quinoline. 45 The polymerization temperature varies depending on the desired microstructure of the copolymer to be produced. Preferably, it is selected from 0° to 150°C, especially from 30° to 80°C, from the viewpoints of economy and side reaction. The amount of the polyvinyl aromatic compound is usually from 0.05 to 1 mole, preferably 0.1 to 0.6 mole, per mole of the organolithium initiator. When the amount is less than the above range, copolymers having the molecular so weight distribution according to the present invention are not obtained, and the obtained copolymers are poor in proc- essability. When the amount is more than the above range, the viscosity of the polymerization solution remarkably increases, thus the controllability in the production is lowered, and also undesirable side reactions such as gellation occur. The whole amount of the polyvinyl aromatic compound may be added to the polymerization system in the initial stage of the polymerization. Alternatively, the polyvinyl aromatic compound may be gradually added to the system in 55 a continuous or intermittent manner during the polymerization. Further, a part of the compound may be used after the coupling reaction with a tri- or tetrafunctional coupling agent. The amount of the trifunctional or tetrafunctional coupling agent is usually from 0.03 to 0.3 mole, preferably from 0.05 to 0.2 mole, per mole of the organolithium initiator. When the amount of the coupling agent is less than the above
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range, copolymers having the molecular weight distribution defined above of the present invention are not obtained, and the obtained copolymers are poor in processability. When the amount is more than the above range, the effect of improving the processability reaches maximum and does not increase even if the amount is increased, thus econom- ically disadvantageous. 5 The butadiene copolymer of the present invention may be used alone or in combination with other synthetic rubbers and/or natural rubber as a rubber component for rubber compositions. The rubber compositions may contain known various additives, e.g., a reinforcing agent such as carbon black or silica, a filler such as calcium carbonate or talc, a plasticizer, a curing accelerator, a curing agent, and an antioxidant. The butadiene copolymer of the present invention can be used as a rubber for various purposes, and is particularly 10 suitable for use in tires. The tires made using the copolymer according to the present invention have excellent char- acteristics in all of resilience, wet grip characteristic, abrasion resistance and mechanical properties. The butadiene copolymer of the present invention has features as explained above. The most important feature of them is that the copolymer has the characteristic molecular weight distribution as defined above. This feature is obtained only when a polyvinyl aromatic compound and a trifunctional or tetrafunctional coupling agent are used. The is butadiene copolymer having the specific molecular weight distribution according to the present invention cannot be obtained by the use of either one of the polyvinyl aromatic compound and the trifunctional or tetrafunctional coupling agent. The present invention is more specifically described and explained by means of the following Examples and Com- parative Examples, in which all % and parts are by weight unless otherwise noted. 20 In the following Examples and Comparative Examples, properties were measured as follows:
(1) Styrene content
The bound styrene content was measured by a refractive index method. 25 (2) Contents of vinyl bonds, cis-1 , 4 bonds and trans-1 , 4 bonds in butadiene moiety
The contents were measured by infrared spectroscopy.
30 (3) Molecular weight distribution curve (Content of specific high molecular weight polymer chains)
A high performance liquid chromatograph HLC-TWINCLE made by Nippon Bunkoh Kogyo Kabushiki Kaisha was used. Also, a column Shodex 80M made by Showa Denko Kabushiki Kaisha was used as a distribution column, and a UV meter was used as a detector. A molecular weight distribution of a copolymer was measured at room temperature 35 by using tetrahydrofuran as a developing solvent to obtain a molecular weight distribution curve (a high performance liquid chromatogram) wherein the axis of ordinate is weight fraction and the axis of abscissa is molecular weight. The weight proportion based on the whole polymer chains (namely content expressed by weight % in the copolymer) of polymer chains having a molecular weight of at least 5 times the molecular weight (in terms of standard polystyrene) which corresponds to the top of the peak located on the lowest molecular weight side of the chromatogram was meas- 40 ured. In the measurement, a calibration curve showing the relationship between retention times and molecular weights was prepared using standard polystyrenes made by Tosoh Corporation, namely polystyrene A-2500 having weight average molecular weight 2.8X1 03, polystyrene F-1 0 having weight average molecular weight 1 .06 X 1 05 and poly- styrene F-128 having weight average molecular weight 1.30 X 106. The molecular weight of a sample copolymer in terms of standard polystyrene was obtained from the calibration curve. 45 (4) Roll processability
Temperature of 6 inch rolls was adjusted to 70°C. A sample mixture obtained by mixing the following ingredients by a Banbury mixer was kneaded on the rolls with changing the roll spacing to 0.7 mm, 1 .0 mm, 1 .5 mm and 2.0 mm. so The state of winding of the sample mixture on the rolls was visually observed and estimated according to the following criteria.
Sample mixture
55 Copolymer 1 00 parts Aromatic oil 50 parts
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(continued) Stearic acid 2 parts Sulfur 2 parts Carbon black 90 parts Zinc oxide 3 parts Curing accelerator (N-cyclohexyl-2-benzothiazylsulfenamide) 1 part SUNNOC N (special wax made by Ohuchi Shinko Kabushiki Kaisha) 2 parts Antioxidant (N-phenyl-N'-isopropyl-p-phenylenediamine) 2 parts
Estimation
5: Winding state is very good, sheet skin is smooth and sheet has a tackiness. 4: Winding state is good, but sheet edge breaking occurs or sheet skin is somewhat rough. 3: Rubber sheet wound on the roll is lacking in tackiness, or biting into rolls of bank is somewhat bad. 2: Bagging and sheet breaking occur. 1 : Biting into rolls in an initial stage is bad, and the mixture is not formed into a sheet and is not wound round the roll.
(5) Physical properties of cured product
The mixture obtained according to the above formulation was press-cured at 160°C for 30 minutes, and the ob- tained cured product was used for the following measurement of physical properties. Resilience was measured at 60°C using a Lupke resilience tester. Wet grip index was measured using a portable skid resistance tester made by Stanley Co., Ltd. with respect to a cured rubber sheet having a thickness of 6.5 mm. An asphalt surface sprayed with water of 20°C was used as the contact road surface. Other properties, namely tensile strength, elongation and abrasion resistance, were measured according to JIS K 6301.
Example 1
A 20 liter stainless steel polymerization vessel was replaced with dry nitrogen, and it was charged with 1 ,400 g of 1 ,3-butadiene, 600 g of styrene, 9,900 g of n-hexane, 80 g of tetrahydrofuran, 10 millimoles of n-butyllithium dissolved in n-hexane and 0.8 millimole of divinylbenzene. The polymerization was carried out at 65°C for 4 hours with stirring. After the completion of the polymerization, 1 .7 millimoles of silicon tetrachloride was added to the reaction mixture, and the reaction was carried out for 30 minutes with stirring. To the reaction mixture was added 10 ml of methanol, and the reaction mixture was further stirred for 5 minutes. The reaction mixture was then taken out of the polymerization vessel. To the reaction mixture were added 10 g of 2,6-di-t-butyl-p-cresol (SumilizerR BHT, product of Sumitomo Chemical Co., Ltd.) and 750 g of aromatic oil. A large portion of n-hexane was evaporated by steam stripping followed by drying under reduced pressure at 50°C for 20 minutes to give a copolymer. The polymerization conditions are shown in Table 1 . The structure of the copolymer and the results of the estimation of the copolymer are shown in Table 2.
Examples 2 to 9 and Comparative Examples 1 to 8
The procedure of Example 1 was repeated except that the polymerization conditions (ingredients) were changed as shown in Table 1 . The structures of the obtained copolymers and the results of the estimation thereof are shown in Table 2. It is observed in Table 2 that all copolymers obtained in the Examples which satisfy the requirements of the present invention, show satisfactory results in all items of the estimation, particularly show that they have a very excellent roll processability, whereas the copolymers obtained in the Comparative Examples which do not have the specific molecular weight distribution defined in the present invention, are poor in roll processability. It is understood that according to the present invention the processability of butadiene copolymer rubbers is re- markably improved with keeping resilience, wet grip property, abrasion resistance and mechanical properties on high levels, thus the present invention provides butadiene copolymer rubbers suitable for use in tires.
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Claims 1. A butadiene copolymer prepared by a process which comprises copolymerizing a mixture of butadiene and a polyvinyl aromatic compound or a mixture of butadiene, styrene and a polyvinyl aromatic compound in a hydro- carbon solvent in the presence of an organolithium compound as a polymerization initiator and subjecting the resulting copolymer having lithium at the polymer end to a coupling reaction with a trifunctional or tetrafunctional coupling agent, said butadiene copolymer satisfying the following conditions (a) to (d): (a) the content of styrene is at most 50 % by weight, (b) the content of vinyl bonds in the butadiene portion is from 10 to 90 % by weight, (c) the molecular weight distribution curve obtained by a high performance liquid chromatography has at least three peaks, and 5 to 60 % by weight of all the polymer chains have a molecular weight which is at least 5 times the molecular weight in terms of standard polystyrene corresponding to the peak appearing on the lowest molecular weight side of the high performance liquid chromatogram, and (d) the Mooney viscosity (ML1+4, 100°C ) is from 30 to 200. 2. The copolymer of Claim 1 , wherein the proportion (c) of polymer chains having a molecular weight of at least 5 times the molecular weight in terms of standard polystyrene which corresponds to the peak located on the lowest molecular weight side of the high performance liquid chromatogram is from 10 to 40 % by weight based on the 10 EP 0 573 893 B1 entire of said copolymer. 3. The copolymer of Claim 1, wherein said hydrocarbon solvent is at least one member selected from the group consisting of benzene, toluene, xylene, ethylbenzene, hexane, heptane, cyclopentane, cyclohexane and methyl- 5 cyclohexane. 4. The copolymer of Claim 1 , wherein said organolithium compound is at least one member selected from the group consisting of ethyllithium, propyllithium, butyllithium, amyllithium, trimethylenedilithium, tetramethylenedilithium, hexyllithium, cyclohexyllithium, phenyllithium, tolyllithium and naphthyllithium. 10 5. The copolymer of Claim 1 , wherein said polyvinyl aromatic compound is at least one member selected from the group consisting of divinylbenzene, 1 ,2,4-trivinylbenzene, 1, 3-divinylnaphthalene, 1 ,8-divinylnaphthalene, 1, 2-di- vinyl-3, 4 -dimethylbenz ene, 2,4-divinylbiphenyl, 3, 5, 4 '-trivinylbiphenyl and 1 ,3,5-trivinylbenzene. is 6. The copolymer of Claim 1, wherein said trifunctional or tetrafunctional coupling agent is at least one member selected from the group consisting of silicon tetrachloride, silicon tetrabromide, silicon tetraiodide, germanium tetrachloride, tin tetrachloride, methyltrichlorosilane, butyl tin trichloride, bistrichlorosilylethane and bistrichlo- roethane. 20 7. The copolymer of Claim 1 , wherein said content of vinyl bonds in the butadiene portion is from 20 to 70 %. 8. The copolymer of Claim 1, wherein said Mooney viscosity (ML1+4, 100°C ) is from 50 to 150. 9. The copolymer of Claim 1 , which is an oil extended butadiene copolymer containing at most 100 parts by weight 25 of an oil extender per 100 parts by weight of the butadiene copolymer. 10. A process for preparing the butadiene copolymer of Claim 1 , which comprises copolymerizing a mixture of buta- diene and a polyvinyl aromatic compound or a mixture of butadiene, styrene and a polyvinyl aromatic compound in a hydrocarbon solvent in the presence of an organolithium compound as a polymerization initiator, and subjecting 30 the resulting copolymer having lithium at the polymer end to a coupling reaction with a trifunctional or tetrafunctional coupling agent, wherein the amount of said polyvinyl aromatic compound is from 0.05 to 1 .0 mole per mole of said organolithium compound initiator. 11. The process of Claim 10, wherein said hydrocarbon solvent is at least one member selected from the group con- 35 sisting of benzene, toluene, xylene, ethylbenzene, hexane, heptane, cyclopentane, cyclohexane and methylcy- clohexane. 12. The process of Claim 10, wherein said organolithium compound is at least one member selected from the group consisting of ethyllithium, propyllithium, butyllithium, amyllithium, trimethylenedilithium, tetramethylenedilithium, 40 hexyllithium, cyclohexyllithium, phenyllithium, tolyllithium and naphthyllithium. 13. The process of Claim 10, wherein said polyvinyl aromatic compound is at least one member selected from the group consisting of divinylbenzene, 1 ,2,4-trivinylbenzene, 1, 3-divinylnaphthalene, 1 ,8-divinylnaphthalene, 1, 2-di- vinyl-3, 4-dimethylbenzene, 2,4-divinylbiphenyl, 3,5,4'-trivinylbiphenyl and 1 ,3,5-trivinylbenzene. 45 14. The process of Claim 1 0, wherein said trifunctional or tetrafunctional coupling agent is at least one member selected from the group consisting of silicon tetrachloride, silicon tetrabromide, silicon tetraiodide, germanium tetrachloride, tin tetrachloride, methyltrichlorosilane, butyl tin trichloride, bistrichlorosilylethane and bistrichloroethane. so 15. The process of Claim 10, wherein the copolymerization is carried out in the presence of a Lewis basic compound as an agent for controlling the vinyl bond content in the butadiene portion. 16. The process of Claim 15, wherein said Lewis basic compound is an ether compound or a tertiary amine compound. 55 17. The process of Claim 15, wherein said Lewis basic compound is at least one member selected from the group consisting of tetrahydrofuran, tetrahydropyran, 1,4-dioxane, diethyl ether, dibutyl ether, ethyleneglycol dimethyl ether, ethyleneglycol diethyl ether, ethyleneglycol dibutyl ether, diethyleneglycol diethyl ether, diethyleneglycol dib- utyl ether, diphenyl ether, anisole, triethylamine, tripropylamine, tributylamine, N,N,N',N'-tetramethylethylenedi- 11 EP 0 573 893 B1 amine, N,N-diethylaniline, pyridine and quinoline. 18. The process of Claim 10, wherein the polymerization temperature is from 0° to 150°C. 5 19. The process of Claim 10, wherein the polymerization temperature is from 30° to 80°C. 20. The process of Claim 10, wherein the amount of said polyvinyl aromatic compound is from 0.1 to 0.6 mole per mole of said organolithium compound initiator. 10 21 . The process of Claim 1 0, wherein the amount of said trifunctional or tetrafunctional coupling agent is from 0.03 to 0.3 mole per mole of said organolithium compound initiator. 22. The process of Claim 10, wherein the amount of said trifunctional or tetrafunctional coupling agent is from 0.05 to 0.2 mole per mole of said organolithium compound initiator. 15 Patentanspruche 1. Butadien-Copolymer, hergestellt durch ein Verfahren, welches Copolymerisieren einer Mischung von Butadien 20 und einer aromatischen Polyvinyl-Verbindung oder einer Mischung von Butadien, Styrol und einer aromatischen Polyvinyl-Verbindung in einem Kohlenwasserstoff-Losungsmittel in Gegenwart einer Organolithiumverbindung als Polymerisationsinitiator und Durchfuhrung einer Kopplungsreaktion mit dem resultierenden Copolymer mit Lithium am Polymerende mit einem trifunktionellen oder tetrafunktionellen Kopplungsmittel umfaBt, wobei das Butadien- Copolymer die folgenden Bedingungen (a) bis (d) erfullt: 25 (a) der Anteil an Styrol betragt hochstens 50 Gew.-%, (b) der Anteil an Vinylbindungen in dem Butadienanteil betragt von 10 bis 90 Gew.-%, 30 (c) die Molekulargewichtsverteilungskurve, erhalten durch Hochleistungs-Flussigkeitschromatographie, weist mindestens drei Peaks auf, und 5 bis 60 Gew.-% aller Polymerketten haben ein Molekulargewicht, das min- destens 5 mal hoher ist als das Molekulargewicht, ausgedruckt als Standardpolystyrol, entsprechend dem Peak, der auf der Seite des Chromatogramms des niedrigsten Molekulargewichts erscheint, und 35 (d) die Mooney-Viskositat (ML1+4, 100°C) betragt von 30 bis 200. 2. Das Copolymer aus Anspruch 1 , wobei der Anteil (c)an Polymerketten mit einem Molekulargewicht von mindestens dem 5fachen des Molekulargewichts, ausgedruckt als Standardpolystyrol, das dem auf der Seite des niedrigsten Molekulargewichts angeordneten Peak im Hochleistungs-Flussigkeitschromatogramm entspricht, 1 0 bis 40 % be- 40 tragt, bezogen auf die Gesamtheit des Copolymeren. 3. Das Copolymer aus Anspruch 1 , wobei das Kohlenwasserstofflosungsmittel mindestens ein Bestandteil ist, aus- gewahlt aus der aus Benzol, Toluol, Xylol, Ethylbenzol, Hexan, Heptan, Cyclopentan, Cyclohexan und Methyl- cyclohexan bestehenden Gruppe. 45 4. Das Copolymer aus Anspruch 1 , wobei die Organolithiumverbindung mindestens ein Bestandteil ist, ausgewahlt aus der aus Ethyllithium, Propyllithium, Butyllithium, Amyllithium, Trimethylendilithium, Tetramethylendilithium, He- xyllithium, Cyclohexyllithium, Phenyllithium, Tolyllithium und Naphthyllithium bestehenden Gruppe. so 5. Das Copolymer aus Anspruch 1 , wobei die aromatische Polyvinylverbindung mindestens ein Bestandteil ist, aus- gewahlt aus der aus Divinylbenzol, 1 ,2,4-Trivinylbenzol, 1 ,3-Divinylnaphthalin, 1 ,8-Divinylnaphthalin, 1,2-Divinyl- 3,4-dimethylbenzol, 2,4-Divinyldiphenyl, 3,5,4'-Trivinylbiphenyl und 1 ,3,5-Trivinylbenzol bestehenden Gruppe. 6. Das Copolymer aus Anspruch 1 , wobei das trifunktionelle oder tetrafunktionelle Kopplungsmittel mindestens ein 55 Bestandteil ist, ausgewahlt aus der aus Siliciumtetrachlorid, Siliciumtetrabromid, Siliciumtetraiodid, Germanium- tetrachlorid, Zinntetrachlorid, Methyltrichlorsilan, Butylzinntrichlorid, Bistrichlorsilylethan und Bistrichlorethan be- stehenden Gruppe. 12 EP 0 573 893 B1 7. Das Copolymer aus Anspruch 1 , wobei der Anteil an Vinylbindungen im Butadienanteil von 20 bis 70 % betragt. 8. Das Copolymer aus Anspruch 1 , wobei die Mooney-Viskositat (ML1+4, 100°C) von 50 bis 150 betragt. 9. Das Copolymer aus Anspruch 1, das ein 6l-gestrecktes Butadien-Copolymer ist, welches hochstens 100 Ge- wichtsteile eines Olextenders pro 100 Gewichtsteile des Butadien-Copolymeren enthalt. 10. Verfahren zur Herstellung des Butadien-Copolymeren aus Anspruch 1 , welches Copolymerisieren einer Mischung von Butadien und einer aromatischen Polyvinylverbindung oder einer Mischung aus Butadien, Styrol und einer aromatischen Polyvinylverbindung in einem Kohlenwasserstofflosungsmittel in Gegenwart einer Organolithium- verbindung als Polymerisationsinitiator und Durchfuhrung einer Kopplungsreaktion des resultierenden Copolyme- ren mit Lithium am Polymerende mit einem trifunktionellen oder tetrafunktionellen Kopplungsmittel umfaBt, wobei die Menge der aromatischen Polyvinylverbindung 0,05 bis 1 ,0 Mol pro Mol des Organolithium-lnitiators betragt. 11. Das Verfahren nach Anspruch 10, wobei das Kohlenwasserstofflosungsmittel mindestens ein Bestandteil ist, aus- gewahlt aus der aus Benzol, Toluol, Xylol, Ethylbenzol, Hexan, Heptan, Cyclopentan, Cyclohexan und Methyl- cyclohexan bestehenden Gruppe. 12. Das Verfahren nach Anspruch 10, wobei die Organolithiumverbindung mindestens ein Bestandteil ist, ausgewahlt aus der aus Ethyllithium, Propyllithium, Butyllithium, Amyllithium, Trimethylendilithium, Tetramethylendilithium, He- xyllithium, Cyclohexyllithium, Phenyllithium, Tolyllithium und Naphthyllithium bestehenden Gruppe. 13. Das Verfahren nach Anspruch 10, wobei die aromatische Polyvinylverbindung mindestens ein Bestandteil ist, aus- gewahlt aus der aus Divinylbenzol, 1 ,2,4-Trivinylbenzol, 1 ,3-Divinylnaphthalin, 1 ,8-Divinylnaphthalin, 1,2-Divinyl- 3,4-dimethylbenzol, 2,4-Divinylbiphenyl, 3,5,4'-Trivinylbiphenyl und 1 ,3,5-Trivinylbenzol bestehenden Gruppe. 14. Das Verfahren nach Anspruch 10, wobei das trifunktionelle odertetrafunktionelle Kopplungsmittel mindestens ein Bestandteil ist, ausgewahlt aus der aus Siliciumtetrachlorid, Siliciumtetrabromid, Siliciumtetraiodid, Germanium- tetrachlorid, Zinntetrachlorid, Methyltrichlorsilan, Butylzinntrichlorid, Bistrichlorsilylethan und Bistrichlorethan be- stehenden Gruppe. 15. Das Verfahren nach Anspruch 10, wobei die Copolymerisation in Gegenwart einer Lewis-Base-Verbindung als Mittel zur Kontrolle des Vinylbindungsanteils im Butadienanteil durchgefuhrt wird. 16. Das Verfahren nach Anspruch 15, wobei die Lewis-Base-Verbindungeine Etherverbindungoder einetertiare Amin- verbindung ist. 17. Das Verfahren nach Anspruch 15, wobei die Lewis-Base-Verbindung mindestens ein Bestandteil ist, ausgewahlt aus derausTetrahydrofuran, Tetrahydropyran, 1,4-Dioxan, Diethylether, Dibutylether, Ethylenglykoldimethylether, Ethylenglykoldiethylether, Ethylenglykoldibutylether, Diethylenglykoldiethylether, Diethylenglykoldibutylether, Diphenylether, Anisol, Triethylamin, Tripropylamin, Tributylamin, N,N,N',N'-Tetramethylethylendiamin, N,N- Diethylanilin, Pyridin und Chinolin bestehenden Gruppe. 18. Das Verfahren nach Anspruch 10, wobei die Polymerisationstemperatur 0 bis 150°C betragt. 19. Das Verfahren nach Anspruch 10, wobei die Polymerisationstemperatur 30 bis 80°C betragt. 20. Das Verfahren nach Anspruch 10, wobei die Menge des aromatischen Polyvinylverbindung 0,1 bis 0,6 Mol pro Mol des Organolithium-lnitiators betragt. 21. Das Verfahren nach Anspruch 10, wobei die Menge des trifunktionellen oder tetrafunktionellen Kopplungsmittels 0,03 bis 0,3 Mol pro Mol des Organolithium-lnitiators betragt. 22. Das Verfahren nach Anspruch 10, wobei die Menge des trifunktionellen oder tetrafunktionellen Kopplungsmittels 0,05 bis 0,2 Mol pro Mol des Organolithium-lnitiators betragt. 13 EP 0 573 893 B1 Revendications 1. Copolymere butadiene prepare a I'aide d'un procede qui comprend le fait de copolymeriser un melange de buta- diene et d'un compose polyvinylaromatique ou un melange de butadiene, de styrene et d'un compose polyvinyla- 5 romatique dans un solvant hydrocarbone en presence d'un compose organique du lithium en tant qu'amorceur de polymerisation et a soumettre le copolymere resultant possedant du lithium a I'extremite polymere, a une reaction de couplage avec un agent de couplage trifonctionnel ou tetrafonctionnel, ledit copolymere de butadiene satisfai- sant les conditions suivantes (a) a (d) : 10 (a) la teneur en styrene est au plus de 50 % en poids ; (b) la teneur en liaisons vinyliques dans la portion de butadiene est de 10 a 90 % en poids ; (c) la courbe de distribution de la masse moleculaire obtenue a I'aide d'une chromatographie liquide a haute is performance possede au moins trois pics, et 5 a 60 % en poids de toutes les chaTnes polymeres ont une masse moleculaire qui est au moins 5 fois la masse moleculaire exprimee en polystyrene etalon correspondant au pic apparaissant du cote a masse moleculaire la plus basse du chromatogramme liquide a haute performance ; et 20 (d) la viscosite de Mooney (ML1+4, 100°C) est de 30 a 200. 2. Copolymere selon la revendication 1 , dans lequel la proportion (c) de chaTnes polymeres ayant une masse mole- culaire d'au moins 5 fois la masse moleculaire exprimee en polystyrene etalon qui correspond au pic situe du cote de masse moleculaire la plus basse du chromatogramme liquide a haute performance est de 10 a 40 % en poids 25 par rapport a la totalite dudit copolymere. 3. Copolymere selon la revendication 1 , dans lequel ledit solvant hydrocarbone est au moins un element choisi dans le groupe forme par le benzene, le toluene, le xylene, I'ethylbenzene, I'hexane, I'heptane, le cyclopentane, le cyclohexane et le methylcyclohexane. 30 4. Copolymere selon la revendication 1, dans lequel ledit compose organique du lithium est au moins un element choisi dans le groupe forme par I'ethyllithium, le propyllithium, le butyllithium, l'amyllithium, le trimethylenedilithium, le tetramethylenedilithium, I'hexyllithium, le cyclohexyllithium, le phenyllithium, le tolyllithium et le naphtyllithium. 35 5. Copolymere selon la revendication 1 , dans lequel ledit compose polyvinylaromatique est au moins un element choisi dans le groupe forme par le divinylbenzene, le 1 ,2,4-trivinylbenzene, le 1 ,3-divinylnaphtalene, le 1,8-divi- nylnaphtalene, le 1 ,2-divinyl-3,4-dimethylbenzene, le 2,4-divinylbiphenyle, le 3,5,4-trivinylbiphenyle et le 1 ,3,5-tri- vinylbenzene. 40 6. Copolymere selon la revendication 1 , dans lequel ledit agent de couplage trifonctionnel et tetrafonctionnel est au moins un element choisi dans le groupe forme par le tetrachlorure de silicium, le tetrabromure de silicium, le tetraiodurede silicium, le tetrachlorure de germanium, le tetrachlorure d'etain, le methyltrichlorosilane, letrichlorure de butyletain, le bistrichlorosilylethane et le bistrichloroethane. 45 7. Copolymere selon la revendication 1 , dans lequel ladite teneur en liaisons vinyliques dans la partie butadiene est comprise entre 20 et 70 %. 8. Copolymere selon la revendication 1, dans lequel ladite viscosite de Mooney (ML1+4, 100°C) est comprise entre 50 et 150. 50 9. Copolymere selon la revendication 1 , qui est un copolymere butadiene dilate par de I'huile contenant au plus 1 00 parties en poids d'un agent de dilatation a base d'huile pour 100 parties en poids du copolymere butadiene. 10. Procede pour preparer le copolymere butadiene selon la revendication 1 , qui consiste a copolymeriser un melange 55 de butadiene et d'un compose polyvinylaromatique ou un melange de butadiene, de styrene et d'un compose polyvinylaromatique dans un solvant hydrocarbone en presence d'un compose organique du lithium en tant qu'amorceur de polymerisation, eta soumettre le copolymere resultant possedant du lithium a I'extremite polymere, a une reaction de couplage avec un agent de couplage trifonctionnel ou tetrafonctionnel, dans lequel la quantite 14 EP 0 573 893 B1 dudit compose polyvinylaromatique est comprise entre 0,05 et 1,0 mole par mole dudit amorceur au compose organique du lithium. 11. Procede selon la revendication 10, dans lequel ledit solvant hydrocarbone est au moins un element choisi dans le groupe forme par le benzene, le toluene, le xylene, I'ethylbenzene, I'hexane, I'heptane, le cyclopentane, le cyclohexane et le methylcyclohexane. 12. Procede selon la revendication 10, dans lequel le compose organique du lithium est au moins un element choisi dans le groupe forme par I'ethyllithium, le propyllithium, le butyllithium, l'amyllithium, le trimethylenedilithium, le tetramethylenedilithium, I'hexyllithium, le cyclohexyllithium, le phenyllithium, le tolyllithium et le naphtyllithium. 1 3. Procede selon la revendication 1 0, dans lequel ledit compose polyvinylaromatique est au moins un element choisi dans le groupe forme par le divinylbenzene, le 1 ,2,4-trivinylbenzene, le 1 ,3-divinylnaphtalene, le 1 ,8-divinylnaph- talene, le 1 ,2-divinyl-3,4-dimethylbenzene, le 2,4-divinylbiphenyle, le 3,5,4-trivinylbiphenyle et le 1 ,3,5-trivinylben- zene. 14. Procede selon la revendication 10, dans lequel ledit agent de couplage trifonctionnel ou tetrafonctionnel est au moins un element choisi dans le groupe forme par le tetrachlorure de silicium, le tetrabromure de silicium. le tetraiodurede silicium, le tetrachlorure de germanium, le tetrachlorure d'etain, le methyltrichlorosilane, letrichlorure de butyletain, le bistrichlorosilylethane et le bistrichloroethane. 1 5. Procede selon la revendication 1 0, dans lequel la copolymerisation est effectuee en presence d'une base de Lewis en tant qu'agent pour reguler la teneur en liaison vinylique dans la partie butadiene. 16. Procede selon la revendication 15, dans lequel ladite base de Lewis est un ether ou une amine tertiaire. 17. Procede selon la revendication 15, dans lequel ladite base de Lewis est au moins un element choisi dans le groupe forme parletetrahydrofuranne, letetrahydropyranne, le 1 ,4-dioxanne, Tether diethylique, Tether dibutylique, Tether dimethylique d'ethyleneglycol, Tether diethylique d'ethyleneglycol, Tether dibutylique d'ethyleneglycol, Tether die- thylique de diethyleneglycol, Tether dibutylique de diethyleneglycol, Tether diphenylique, Tanisole. latriethylamine, la tripropylamine, la tributylamine, la N,N,N',N'-tetramethylethylenediamine, la N,N-diethylaniline, la pyridine et la quinoline. 18. Procede selon la revendication 10, dans lequel la temperature de polymerisation est comprise entre 0° et 150°C. 19. Procede selon la revendication 10, dans lequel la temperature de polymerisation est comprise entre 30° et 80°C. 20. Procede selon la revendication 1 0, dans lequel la quantite dudit compose polyvinylaromatique est comprise entre 0,1 et 0,6 mole par mole dudit amorceur au compose organique du lithium. 21. Procede selon la revendication 10, dans lequel la quantite dudit agent de couplage trifonctionnel ou tetrafonctionnel est comprise entre 0,03 et 0,3 mole par mole dudit amorceur au compose organique du lithium. 22. Procede selon la revendication 10, dans lequel la quantite dudit agent de couplage trifonctionnel ou tetrafonctionnel est comprise entre 0,05 et 0,2 mole par mole dudit amorceur au compose organique du lithium. 15