Novel propylene polymerization process

A process for the production of substantially amorphous interpolymers which comprises polymerizing from about 70 to about 90 wt. % propylene and from about 10 to about 30 wt. % ethylene at a temperature between about 130.degree. F. and about 175.degree. F. and at a reactor pressure sufficient to maintain propylene in the liquid phase, in the presence of from about 0.7 to about 3.0 mol % hydrogen based on the monomer feed to the process and employing as catalyst a composition comprised of:

• (a) a solid catalyst component produced by the method comprising
• (i) co-communicating magnesium halide support base and aluminum trihalide in a molar ratio from about 8:0.5 to about 8:3 in the absence of added electron donor and (ii) then co-communicating the product of step (i) in the absence of added electron donor with sufficient titanium tetrahalide to provide a molar ratio of magnesium halide to titanium tetrahalide from about 8:0.4 to about 8:1;
• and
• (b) a co-catalyst component comprised of a mixture of from about 15 to about 90 mol % of trialkylaluminum having from 1 to 9 carbon atoms in each alkyl group and about 85 to about 10 mol % of an alkylaluminum halide having at least one halide group per molecular in a sufficient quantity to provide an Al/Ti ratio in the range from about 50:1 to about 600:1;
• and recovering a substantially amorphous, random interpolymer having a tacticity index m/r ranging between about 3 and about 4 as determined by 13C NMR spectra.