Neodymium-catalyzed polybutadienes

1. A process for producing high-molecular-weight, neodymium-catalysed polybutadiene comprising:

1) modifying the 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,

component B: a dialkylaluminium hydride

component C: a trialkylaluminium compound,

component D: a diene, and

component E: at least one organometallic halide

where, in a first step, components A, B, C and D are first mixed at a temperature of from 0° C. to 80° C. for a period of from 5 minutes to 10 hours, and cooling the mixture to below −10° C. prior to addition of component E;

2) preforming the modified catalyst system at a temperature of 0° C. to 80 C for a period of from 1 to 250 hours; and

3) polymerizing component D at a temperature of from −20 to 150° C. to produce the polybutadiene,

wherein the neodymium-catalysed polybutadiene comprises a high proportion, >95%, of cis-1,4 units and having a low proportion, <1%, of 1,2-vinyl content, and 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 and a Mw 90%<1 000 000 g/mol and Mw 10%>100 000 g/mol.

2. The process according to claim 1 , characterized in that component D is a monomer identical with that used for producing high-molecular-weight neodymium-catalysed polybutadiene.

3. The process according to claim 2 , characterized in that the molar ratio of component A to component B is from 1:1 to 1:100, the molar ratio of component A to component C is from 1:0.4 to 1:15, the molar ratio of component A to component D is from 1:1 to 1:200, and the molar ratio of component A to component E is from 1:0.5 to 1:20.