Ziegler-natta catalyst systems containing organometallic compounds

Abstract

Ziegler-Natta-type catalyst systems containing, as active constituents, a) a titanium-containing solid component which also contains magnesium, halogen and a carboxylic acid ester as electron donor, b) an aluminum component, c) a further electron-donor component, and, as an additional component, d) an organometallic compound of the general formula A or B ##STR1## where M.sup.1 is an element f rom main group I, and M.sup.2 is an element from main group II of the Periodic Table, and R.sup.1 and R.sup.2 are identical or different C.sub.1 -C.sub.10 -alkyl, C.sub.6 -C.sub.12 -aryl, C.sub.6 -C.sub.12 -arylalkyl, or 5- to 7-membered cycloalkyl, which may itself carry C.sub.1 -C.sub.8 -alkyl groups, can be used to prepare polymers which have, in particular, a low proportion of very fine grains.

Dependencies are inferred from the claim text.