Neodymium-catalyzed polybutadienes

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 (ML1+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.