| 摘要 |
The present invention relates to polypropylene impact copolymer compositions which exhibit improved stiffness without degrading the impact resistance performance. The polypropylene impact copolymer comprises a matrix and a dispersed phase. The matrix comprises a polypropylene homopolymer or a propylene/alpha-olefin random copolymer which comprises more than 50 wt. % of units derived from propylene monomer. The matrix should have a relatively high crystallinity, preferably 50% or greater. The polypropylene homopolymer or a propylene/alpha-olefin random copolymer preferably has a MWD between 4 and 8, such as typically obtained using Ziegler-Natta catalysts. The dispersed phase in the impact copolymer comprises an ethylene-propylene copolymer which comprises from 45 to 70 wt. % of units derived from an ethylene monomer. Preferably the dispersed phase comprises from 20 to 50 percent by weight of the polypropylene impact copolymer. |
