CATALYST, ITS MANUFACTURE AND ITS USE IN THE SOLUTION-POLYMERISATION OF CONJUGATED DIENES

1. A catalyst which is homogeneously soluble in solvents for the polymerisation of dienes, obtained by adding the catalyst constituents to the polymerisation mixture and mixing them therewith, consisting of : A) a rare earth carboxylate of the formula see diagramm : EP0011184,P8,F1 B) an aluminium alkyl AIR3 **4 and/or R2 **4AIH and C) a further Lewis acid, wherein in the formulae M denotes a trivalent rare earth element having an atomic number of from 57 to 71, R**1, R**2 and R**3 are identical or different and denote alkyl radicals with 1 to 10 carbon atoms, the sum of all the C atoms in the substituents being from 6 to 20,and R**4 denotes an alkyl radical with 1 to 10 carbon atoms, with the exception of a catalyst which contains a reaction product of component A of the formula 1, wherein the sum of all the C atoms in the substituents is from 6 to 19, with a portion of component B, when B has the meaning aluminium trialkyl.