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 HLMI in a range from about 10 to about 55 g/10 min, and a ratio of HLMI/MI in a range from about 185 to about 550;
a Mw in a range from about 200,000 to about 450,000 g/mol;
an IB parameter in a range from about 1.46 to about 1.80;
an IVc in a range from about 2.2 to about 3.2 dL/g;
a tan δ at 0.1 sec −1 in a range from about 1.05 to about 1.75 degrees; 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 0.18 to about 0.28; and
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.
2. An article comprising the ethylene polymer of claim 1 .
3. The polymer of claim 1 , wherein the density is in a range from about 0.955 to about 0.968 g/cm 3 .
4. The polymer of claim 1 , wherein the ratio of HLMI/MI is in a range from about 250 to about 550.
5. The polymer of claim 1 , wherein the Mw is in a range from about 250,000 to about 370,000 g/mol.
6. The polymer of claim 1 , wherein the IVc is in a range from about 2.3 to about 3.2 dL/g.
7. The polymer of claim 1 , wherein the IB parameter is in a range from about 1.46 to about 1.75.
8. The polymer of claim 1 , wherein the tan δ at 0.1 sec −1 is in a range from about 1.05 to about 1.45 degrees.
9. The polymer of claim 1 , wherein the slope is in a range from about 0.20 to about 0.26.
10. The polymer of claim 1 , wherein the ethylene polymer has an environmental stress crack resistance (ESCR) of at least 2,000 hours.
11. The polymer of claim 1 , wherein the ethylene polymer has:
a Mp in a range from about 30,000 to about 55,000 g/mol;
a ratio of Mw/Mn in a range from about 12 to about 30; and
a ratio of Mz/Mw in a range from about 5 to about 8.
12. A blow molded article comprising the ethylene polymer of claim 11 .
13. The polymer of claim 11 , wherein the ratio of Mw/Mn is in a range from about 12 to about 28.
14. The polymer of claim 13 , wherein the ethylene polymer has a relaxation time in a range from about 5 to about 30 sec.
15. The polymer of claim 1 , wherein the ethylene polymer has a CY-a parameter in a range from about 0.3 to about 0.5.
16. The polymer of claim 1 , wherein the ethylene polymer has a viscosity at 100 sec −1 in a range from about 1100 to about 2000 Pa-sec.
17. The polymer of claim 1 , wherein the ethylene polymer has a tan δ at 100 sec −1 in a range from about 0.3 to about 0.5 degrees.
18. The polymer of claim 1 , wherein the ethylene polymer has a ratio of Mz/Mw in a range from about 5.5 to about 7.5.
19. The polymer of claim 1 , wherein the ethylene polymer has:
a bimodal molecular weight distribution;
less than about 0.008 long chain branches per 1000 total carbon atoms; and
a number of short chain branches per 1000 total carbon atoms at Mz that is greater than at Mn.
20. The polymer of claim 1 , wherein the ethylene polymer contains, independently, less than 0.1 ppm by weight of chromium and titanium.
21. 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.