Polymers with improved ESCR for blow molding applications

摘要

Disclosed herein are ethylene-based polymers having a higher molecular weight component and a lower molecular weight component, and characterized by a density greater than 0.945 g/cm3, a melt index less than 1.5 g/10 min, and a ratio of high load melt index to melt index ranging from 40 to 175. These polymers have the processability of chromium-based resins, but with improved stiffness and stress crack resistance, and can be used in blow molding and other end-use applications.

主权项

1. A polymerization process comprising:
contacting a catalyst composition with ethylene and an olefin comonomer in a polymerization reactor system under polymerization conditions to produce an ethylene polymer;wherein the ethylene polymer comprises a higher molecular weight component and a lower molecular weight component, and wherein the ethylene polymer is characterized by:
a density in a range from about 0.95 to about 0.965 g/cm3; a melt index (MI) in a range from about 0.05 to about 1.5 g/10 min; a ratio of high load melt index to melt index (HLMI/MI) in a range from about 40 to about 175; a bimodal molecular weight distribution; less than about 0.008 long chain branches per 1000 total carbon atoms; a number of short chain branches per 1000 total carbon atoms at Mz that is greater than or equal to the number at Mn; and a slope of a plot of the viscosity (Pa-sec) versus shear rate (sec−1) at 190° C. of the ethylene polymer at 100 sec−1 in a range from about 0.42 to about 0.65.