The present invention relates to a process for the preparation of random
copolymers of propylene with c.sub.2 -c.sub.10 .alpha.-olefins, carried
out in the presence of a catalyst comprising:
A) A solid component comprising a titanium compound supported on mgcl.sub.2
in active form and an electron-donor compound;
b) An alkyl-al compound, and
c) An electron-donor compound selected from the group of 1,3-diethers.
The copolymers obtained using the said process show, for an equivalent
content of .alpha.-olefin, a lower content of xylene-soluble fractions
when compared with the copolymers obtained with the catalysts of the prior
art.
