NEODYMIUM-CATALYZED POLYBUTADIENES

1 . High-molecular-weight, linear, neodymium-catalysed polybutadiene having a high proportion, >95%, of cis-1,4 units and having a low proportion, <1%, of 1,2-vinyl content, and also having a small molar-mass-distribution index (MDI), characterized in that

Mooney viscosity (ML 1+4 100° C.) of the polybutadiene is from 70 to 90 and

the molar-mass-distribution index of the polybutadiene is smaller than 10.

2 . Polybutadiene according to claim 1 , characterized in that the solution viscosity (RT, 5.43%, toluene) is from 350 to 630 mPas, preferably from 400 to 580 mPas.

3 . Polybutadiene according to claim 2 , characterized in that the branching index (BI) is from 5 to 7.

4 . Polybutadiene according to claim 3 , characterized in that its Mooney relaxation after 30 sec (ML-Relax 30 sec) is smaller than 6%.

5 . Polybutadiene according to claim 4 , characterized in that its molar-mass distribution is Mw 90%<1 000 000 g/mol and Mw 10%>100 000 g/mol.

6 . Process for producing high-molecular-weight, neodymium-catalysed polybutadienes according to any of the preceding claims, encompassing the following steps:

1) modified catalyst production using a preformation process, with use of catalyst systems based on neodymium, composed of

component A: an alcoholate or a carboxylate of neodymium, preferably neodymium versatate,

component B: a dialkylaluminium hydride, preferably diisobutylaluminium hydride (DIBAH),

component C: a trialkylaluminium compound, preferably tributylaluminium,

component D: a diene, preferably butadiene or isoprene, and

component E: at least one organometallic halide, preferably ethylaluminium sesquichloride (EASC),

where, in a first step, components A, B, C and D are firstly mixed at a temperature of from 0° C. to 80° C., preferably from 30° C. to 60° C., for a period of from 5 minutes to 10 hours, preferably from 20 minutes to 2 hours, and the mixture is then cooled to below −10° C., preferably to below −30° C., prior to addition of component E;

2) a process of preformation of the modified catalyst system at a temperature of from −30° C. to 80 C, preferably from 5° C. to 50° C., for a period of from 1 to 250 hours, preferably from 2 to 100 hours;

3) polymerization of the monomers at a temperature of from −20 to 150° C.

7 . Process according to claim 6 , characterized in that component D is preferably a monomer identical with that used for producing high-molecular-weight neodymium-catalysed polybutadienes.

8 . Process according to claim 7 , characterized in that the molar ratio of component A to component B is from 1:1 to 1:100, preferably from 1:3 to 1:80 and particularly preferably from 1:3 to 1:50, the molar ratio of component A to component C is from 1:0.4 to 1:15, preferably from 1:0.5 to 1:8, the molar ratio of component A to component D is from 1:1 to 1:200, preferably from 1:2 to 1:100 and particularly preferably from 1:3 to 1:50, and the molar ratio of component A to component E is from 1:0.5 to 1:20, preferably from 1:0.7 to 1:10 and particularly preferably from 1:0.8 to 1:8.

9 . Rubber mixtures comprising a polybutadiene according to claim 5 .

10 . Use of the rubber mixtures according to claim 9 for producing mouldings of any type.

11 . Use according to claim 10 , characterized in that the moulding is a tyre component.

12 . Use of the rubber mixture according to claim 9 for impact-modifying thermoplastics.

13 . Use of the rubber mixtures according to claim 9 for polystyrene and styrene/acrylonitrile copolymers.

14 . Use of the rubber mixtures according to claim 9 for golf balls.