Dual metallocene polyethylene with improved processability for lightweight 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 30 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 250,000 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.

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 ;

the HLMI is in a range from about 20 to about 30 g/10 min;

the ratio of HLMI/MI is in a range from about 250 to about 550;

the Mw is in a range from about 250,000 to about 340,000 g/mol;

the IVc is in a range from about 2.3 to about 3.1 dL/g;

the IB parameter is in a range from about 1.50 to about 1.75;

the tan δ at 0.1 sec −1 is in a range from about 1.10 to about 1.50 degrees; and

the slope is in a range from about 0.19 to about 0.25.

4. The polymer of claim 3 , wherein the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, and/or an ethylene/1-octene copolymer.

5. The polymer of claim 4 , wherein the ethylene polymer has an environmental stress crack resistance (ESCR) of at least 2,000 hours.

6. A blow molded article comprising the ethylene polymer of claim 5 .

7. 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.

8. The polymer of claim 1 , wherein the ethylene polymer has:

a CY-a parameter in a range from about 0.32 to about 0.55;

a viscosity at 100 sec −1 in a range from about 1100 to about 2000 Pa-sec;

a tan δ at 100 sec −1 in a range from about 0.3 to about 0.5 degrees; and

a relaxation time in a range from about 3 to about 30 sec.

9. 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.

10. The polymer of claim 1 , wherein:

the ethylene polymer contains, independently, less than 0.1 ppm by weight of chromium and titanium; and

the ethylene polymer has a topload strength:

from about 180 to about 270 lb at a part weight of 105 g; and/or

from about 160 to about 230 lb at a part weight of 95 g.

11. 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 30 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 300,000 g/mol;

an IB parameter in a range from about 1.46 to about 1.80;

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.

12. An article comprising the ethylene polymer of claim 11 .

13. The polymer of claim 11 , wherein:

the density is in a range from about 0.955 to about 0.968 g/cm 3 ;

the HLMI is in a range from about 30 to about 50 g/10 min;

the ratio of HLMI/MI is in a range from about 250 to about 550;

the Mw is in a range from about 210,000 to about 280,000 g/mol;

the IB parameter is in a range from about 1.46 to about 1.75;

the tan δ at 0.1 sec −1 is in a range from about 1.10 to about 1.60 degrees; and

the slope is in a range from about 0.19 to about 0.27.

14. The polymer of claim 13 , wherein:

the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, and/or an ethylene/1-octene copolymer; and

the ethylene polymer has an environmental stress crack resistance (ESCR) of at least 2,000 hours.

15. A blow molded article comprising the ethylene polymer of claim 14 .

16. The polymer of claim 11 , wherein the ethylene polymer has:

a Mp in a range from about 25,000 to about 45,000 g/mol;

a ratio of Mw/Mn in a range from about 14 to about 28; and

a ratio of Mz/Mw in a range from about 5.3 to about 7.5.

17. The polymer of claim 11 , wherein the ethylene polymer has:

a CY-a parameter in a range from about 0.3 to about 0.5;

a viscosity at 100 sec −1 in a range from about 1000 to about 1500 Pa-sec;

a tan δ at 100 sec −1 in a range from about 0.3 to about 0.5 degrees; and

a relaxation time in a range from about 3 to about 20 sec.

18. A polymerization process, the process comprising contacting a catalyst composition with ethylene and an α-olefin comonomer in a polymerization reactor system under polymerization conditions to produce an ethylene polymer, wherein the ethylene polymer has:

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

the catalyst composition comprises:

an unbridged metallocene compound containing two cyclopentadienyl groups, two indenyl groups, or a cyclopentadienyl and an indenyl group;

a bridged metallocene compound with a cyclopentadienyl group and fluorenyl group, and an alkenyl substituent on the cyclopentadienyl group and/or on the bridging group;

an activator-support comprising a solid oxide treated with an electron-withdrawing anion; and

an organoaluminum compound.

19. The process of claim 18 , wherein the activator-support comprises a fluorided solid oxide and/or a sulfated solid oxide.

20. The process of claim 18 , wherein the polymerization reactor system comprises a slurry reactor, gas-phase reactor, solution reactor, or a combination thereof.