Neodymium-catalyzed polybutadienes

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.