Patent ID: 7381779

Claim:
A catalyst composition for the polymerization of propylene or mixtures of propylene and one or more copolymerizable comonomers, said catalyst composition comprising: one or more Ziegler-Natta procatalyst compositions comprising one or more transition metal compounds and one or more esters of aromatic dicarboxylic acid internal electron donors; one or more aluminum containing cocatalysts; and an SCA mixture of two or more different selectivity control agents, said SCA mixture comprising from 1 to 99 mol percent of ethyl p-ethoxybenzoate, and from 99 to 1 mol percent of dicyclopentyldimethoxysilane, said compounds and amounts being selected such that: A T ⁢ ⁢ 2 ⁡ ( mixture ) A T ⁢ ⁢ 1 ⁡ ( mixture ) < A T ⁢ ⁢ 2 ⁡ ( Si ) A T ⁢ ⁢ 1 ⁡ ( Si ) where A T2 (mixture) and A T1 (mixture) are normalized catalyst activities using the SCA mixture at temperatures T2 and T1, respectively; A T2 (Si) and A T1 (Si) are normalized catalyst activities using only the alkoxysilane SCA compound at temperatures T2 and T1, respectively; T1 is a normal polymerization temperature from 50 to 85° C.; and T2 is a polymerization temperature higher than T1 possibly encountered during the polymerization under nonstandard polymerization conditions from 85 to 130° C.