Dual metallocene polyethylene with improved processability for lightweight blow molded products
Ethylene-based polymers having a density of 0.952 to 0.968 g/cm 3 , a ratio of HLMI/MI from 185 to 550, an IB parameter from 1.46 to 1.80, a tan δ at 0.1 sec −1 from 1.05 to 1.75 degrees, and a slope of a plot of viscosity versus shear rate at 100 sec −1 from 0.18 to 0.28 are described, with low melt flow versions having a HLMI from 10 to 30 g/10 min and a Mw from 250,000 to 450,000 g/mol, and high melt flow versions having a HLMI from 30 to 55 g/10 min and a Mw from 200,000 to 300,000 g/mol. These polymers have the processability of chromium-based resins, but with improved stress crack resistance and topload strength for bottles and other blow molded products.
1. An ethylene polymer having:
a density in a range from about 0.952 to about 0.968 g/cm 3 ;
a relaxation time in a range from about 20 to about 1050 sec;
a tan δ at 0.1 sec −1 in a range from about 0.8 to about 1.15 degrees;
a viscosity at 100 sec −1 in a range from about 1000 to about 1900 Pa-sec; and
a slope of a plot of viscosity (Pa-sec) versus shear rate (sec −1 ) of the ethylene polymer at 100 sec −1 in a range from about 0.20 to about 0.31.
2. An article comprising the ethylene polymer of claim 1 .
3. The polymer of claim 1 , wherein the ethylene polymer has a high load melt index (HLMI) in a range from about 17 to about 55 g/10 min.
4. The polymer of claim 1 , wherein the ethylene polymer has a peak molecular weight (Mp) in a range from about 43,000 to about 57,000 g/mol.
5. The polymer of claim 1 , wherein the ethylene polymer has an IB parameter in a range from about 1.4 to about 1.6.
6. The polymer of claim 1 , wherein the ethylene polymer has a CY-a parameter in a range from about 0.15 to about 0.44.
7. The polymer of claim 1 , wherein the ethylene polymer has a tan δ at 100 sec −1 in a range from about 0.34 to about 0.52 degrees.
8. The polymer of claim 1 , wherein the ethylene polymer has a viscosity at HLMI in a range from about 200 to about 1550 Pa-sec.
9. The polymer of claim 1 , wherein the ethylene polymer has an environmental stress crack resistance (ESCR) of at least 2,000 hours.
10. The polymer of claim 1 , wherein the ethylene polymer has a topload strength:
from about 200 to about 260 lb at a part weight of 105 g; and/or
from about 170 to about 220 lb at a part weight of 95 g.
11. The polymer of claim 1 , wherein the ethylene polymer comprises an ethylene homopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or any combination thereof.
12. A polymer composition comprising the ethylene polymer of claim 11 and a post-consumer recycled polymer.
13. The composition of claim 12 , wherein the ethylene polymer has a high load melt index (HLMI) in a range from about 17 to about 55 g/10 min.
14. An article comprising the polymer composition of claim 13 .
15. The polymer of claim 11 , wherein the density is in a range from about 0.957 to about 0.966 g/cm 3 .
16. The polymer of claim 11 , wherein the relaxation time is in a range from about 45 to about 1050 sec.
17. The polymer of claim 11 , wherein the tan δ at 0.1 sec −1 is in a range from about 0.85 to about 1.1 degrees.
18. The polymer of claim 11 , wherein the viscosity at 100 sec −1 is in a range from about 1200 to about 1700 Pa-sec.
19. The polymer of claim 11 , wherein the slope of the plot of viscosity (Pa-sec) versus shear rate (sec −1 ) of the ethylene polymer at 100 sec −1 is in a range from about 0.25 to about 0.30.
20. The polymer of claim 11 , wherein the ethylene polymer contains, independently, less than 0.1 ppm by weight of chromium and titanium.
21. A blow molded article comprising the ethylene polymer of claim 20 .