. . "A process for preparing rubber-like interpolymers of three different olefins, one being ethylene, the second being of the group consisting of propylene and butene-l, and thethird being different from the first two and having the formula CH =CHR wherein R is an alkyl radical of from 2 to 8 carbon atoms, said polymerization being carried out at ordinary atmospheric temperatures to 60 C. in the prese" . .