CCATALYTIC POLYMERISATION OF OLEFINS

1. A process for the preparation of homopolymers and copolymers of C2 -C6 -alpha-monoolefins at from 20 to 160 degrees C under a pressure of from 1 to 100 bar by means of a Ziegler-Natta catalyst system comprising (1) a modified titanium component and (2) an aluminium alkyl of the formula see diagramm : EP0036536,P8,F1 where X and Y are alkyl of not more than 8 carbon atoms and Z is alkyl of not more than 8 carbon atoms or chlorine, with the proviso that the atomic ratio of titanium from the modified titanium component (1) to aluminium from the aluminium alkyl (2) is from 1:0.1 to 1:500, wherein (a) the catalyst system contains, as a further component, (3) an ester component of the formula see diagramm : EP0036536,P8,F2 where R**1 is C1 -C4 -alkoxy, C1 -C4 -alkyl or hydrogen, R**2 is C1 -C4 -alkyl, and n is an integer from 0 to 3, with the proviso that the molar ratio of aluminium alkyl (2) to ester component (3) is from 10:8 to 10:0.5, and (b) the modified titanium component (1) employed is a component which is obtained by a method wherein first of all (1.1) in a first stage, (1.1.1) 100 parts by volume of titanium tetrachloride are brought together with (1.1.2) from 1 to 20 parts by volume of a benzene derivative of the formula see diagramm : EP0036536,P9,F1 where R**3 is hydrogen or C1 -C4 -alkyl, R**4 is hydrogen or chlorine, R**5 is hydrogen or chlorine, or R**4 and R**5 together are oxygen, o is an integer from 0 to 3, and p is an integer from 0 to 3, and the mixture is kept at from 30 to 100 degrees C until it is in the form of a homogeneous liquid, thereafter (1.2) in a second stage, (1.2.1) the liquid resulting from stage (1.1) is brought together with (1.2.2) a magnesium alcoholate in the form of particles having a diameter of from 0.05 to 5.0 mm, and having the formula Mg(OD)2 , where D is a monovalent C1 -C8 -hydrocarbon radical of saturated aliphatic character and/or aromatic character, with the proviso that the molar ratio of benzene derivative (1.1.2) from stage (1.1) to magnesium alcoholate (1.2.2) is from 1:12 to 1:1, the mixture is kept, with constant mixing, at from 40 to 180 degrees C, for from 0.2 to 4 hours, and the resulting solid is isolated, with the removal of the residual liquid phase, and finally (1.3) in a third stage, (1.3.1) 100 parts by weight of titanium tetrachloride are brought together with (1.3.2) from 0.2 to 100 parts by weight of the solid resulting from stage (1.2), with or without (1.3.3) up to 15 parts by weight of