Patent ID: 8846837

Claim:
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.