A process for the preparation of homopolymers of ethene and copolymers of ethene with minor amounts of C.sub.3 -C.sub.8 -a-monoolefins by polymerization of the monomer or monomers at from 30.degree. to 200.degree. C. and under pressure from 0.1 to 200 bar using a Ziegler catalyst system consisting of
- (1) a transition metal catalyst component and
- (2) an organoaluminum catalyst component of the formula AlR.sub.m X.sub.3-m, where X is a radical OR, chlorine, bromine or hydrogen, R is a C.sub.1 -C.sub.18 -hydrocarbon radical and m is from 1 to 3, and
- (3) an organohalogen catalyst component with the provisos that the atomic ratio of transition metal from catalyst component (1) to aluminum from catalyst component (2) is from 1:0.1 to 1:500, and the molar ratio of organoaluminum catalyst component (2) to organohalogen catalyst component (3) is from 1:0.0001 to 1:10,
- wherein the transition metal catalyst component (1) used is the solid-phase product (VI) which has been obtained by a method in which
- (1.1) first
- (1.1.1) a finely divided, porous, inorganic oxidic substance (I) which has a particle diameter of from 1 to 1,000 .mu.m, a pore volume of from 0.3 to 3 cm.sup.3 /g and a specific surface area of from 100 to 1,000 m.sup.2 /g and is of the formula SiO.sub.2.aAl.sub.2 O.sub.3, where a is from 0 to 2, and
- (1.1.2) a solution (II) as obtained on combining (IIa) 100 parts by weight of a saturated aliphatic or partly saturated aliphatic and partly aromatic oxahydrocarbon which has 1 or 2 oxaoxygen atoms and more than 3 but less than 19 carbon atoms and
- (IIb) from 0.01 to 50 parts by weight of a mixture of
- (IIbl) 100 molar parts of a vanadium trihalide/alcohol complex of the formula VY.sub.3.nZ-OH, where Y is chlorine or bromine, n is from 1 to 6 and Z is a monovalent saturated aliphatic or partly saturated aliphatic and partly aromatic hydrocarbon radical of not more than 10 carbon atoms,
- (IIb2) from 0.2 to 200 molar parts of a titanium trihalide, where halogen may be chlorine and/or bromine, or a titanium trihalide complex of the formula TiY.sub.3.nZ-OH, where Y is chlorine or bromine, n is from 1 to 6 and Z is a monovalent saturated aliphatic or partly saturated aliphatic and partly aromatic hydrocarbon radical of not more than 10 carbon atoms, and
- (IIc) from 1 to 200 parts by weight of a compound of the type BXnYmRp or SiXnYmRq, where X is a radical OR, Y is chlorine, bromine or hydrogen and R is a C.sub.1 -C.sub.18 -hydrocarbon radical, with the proviso that n>0 and n+m+p=3 or n+m+q =4, are brought into contact with one another with formation of a suspension (III), with the proviso that the weight ratio of inorganic oxidic substance (I) to transition metal composition (IIb) is from 1:0.01 to 1:2, the suspension (III) evaporate to dryness at a temperature which is below 200.degree. C. and above the melting point of the oxahydrocarbon (IIa) used, with formation of a solid-phase intermediate (IV), and
- (1.2) then
- (1.2.1) the solid-phase intermediate (IV) obtained from stage (1.1) and
- (1.2.2) an aluminum compound (V) which is dissolved in an organic solvent and is of the formula AlR.sub.m X.sub.3-m, where X is a radical OR, chlorine, bromine or hydrogen, R is a C.sub.1 -C.sub.18 -hydrocarbon radical and m is from 1 to 3, are brought into contact with one another with formation of a suspension, with the proviso that the weight ratio of solid-phase intermediate (IV) to aluminum compound (V) is from 1:0.05 to 1:2, the solid-phase product (VI) formed as the suspended substance being the transition metal catalyst component (1).