Metallocene catalyst system for producing LLDPE copolymers with tear resistance and low haze

1. A film comprising an ethylene polymer, wherein the film has:

a haze in a range from about 2 to about 10%; and

a MD Elmendorf tear strength in a range from about 200 to about 500 g/mil; and wherein the ethylene polymer has:

a density in a range from about 0.908 to about 0.925 g/cm 3 ;

a melt index in a range from about 0.5 to about 3 g/10 min;

a ratio of Mw/Mn in a range from about 2 to about 4;

a ratio of Mz/Mw in a range from about 1.6 to about 2.3;

a CY-a parameter in a range from about 0.45 to about 0.6; and

an ATREF profile characterized by a single peak at a peak ATREF temperature in a range from about 76 to about 88° C., and by less than or equal to about 4.5 wt % of the polymer eluting above a temperature of 91° C.

2. The film of claim 1 , wherein:

the peak ATREF temperature is in a range from about 79 to about 86° C.; and

less than or equal to about 3.5 wt % of the polymer elutes above a temperature of 91° C.

3. The film of claim 1 , wherein:

the haze is in a range from about 2 to about 8%; and

the MD Elmendorf tear strength is in a range from about 250 to about 400 g/mil.

4. The film of claim 1 , wherein:

the ethylene polymer has a unimodal molecular weight distribution; and

the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or a combination thereof.

5. The film of claim 4 , wherein the film is a blown film having an average thickness in a range from about 0.8 to about 5 mils.

6. The film of claim 4 , wherein:

the density is in a range from about 0.91 to about 0.922 g/cm 3 ;

the melt index is in a range from about 1 to about 2.5 g/10 min;

the ratio of Mw/Mn is in a range from about 2.2 to about 3.8;

the ratio of Mz/Mw is in a range from about 1.7 to about 2.2; and

the CY-a parameter is in a range from about 0.5 to about 0.6.

7. The film of claim 6 , wherein the film is a cast film having an average thickness in a range from about 0.5 to about 8 mils.

8. The film of claim 4 , wherein the film has:

a ratio of MD Elmendorf tear strength to TD Elmendorf tear strength (MD:TD) in a range from about 0.5:1 to about 0.9:1; and

a dart impact strength of greater than or equal to about 500 g/mil.

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

a Mn in a range from about 25,000 to about 55,000 g/mol; and

a high load melt index (HLMI) in a range from about 18 to about 45 g/10 min.

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

a Mz in a range from about 175,000 to about 275,000 g/mol; and

an IB parameter in a range from about 0.9 to about 1.05.

11. The film of claim 1 , wherein:

the haze is in a range from about 2 to about 7%; and

the MD Elmendorf tear strength is in a range from about 300 to about 400 g/mil.

12. An ethylene polymer having:

a density in a range from about 0.908 to about 0.925 g/cm 3 ;

a melt index in a range from about 0.5 to about 3 g/10 min;

a ratio of Mw/Mn in a range from about 2 to about 4;

a ratio of Mz/Mw in a range from about 1.6 to about 2.3;

a CY-a parameter in a range from about 0.45 to about 0.6; and

an ATREF profile characterized by a single peak at a peak ATREF temperature in a range from about 76 to about 88° C., and by less than or equal to about 4.5 wt % of the polymer eluting above a temperature of 91° C.

13. The polymer of claim 12 , wherein the ethylene polymer has:

a Mw in a range from about 80,000 to about 180,000 g/mol; and

a relaxation time (τ η ) in a range from about 4×10 −3 sec to about 2×10 −2 sec.

14. An article of manufacture comprising the ethylene polymer of claim 13 .

15. The polymer of claim 12 , wherein:

the density is in a range from about 0.91 to about 0.922 g/cm 3 ;

the melt index is in a range from about 1 to about 2.5 g/10 min;

the ratio of Mw/Mn is in a range from about 2.2 to about 3.8;

the ratio of Mz/Mw is in a range from about 1.7 to about 2.2;

the CY-a parameter is in a range from about 0.52 to about 0.59;

the peak ATREF temperature is in a range from about 79 to about 86° C.; and

less than or equal to about 3.5 wt % of the polymer elutes above a temperature of 91° C.

16. The polymer of claim 12 , wherein the ATREF profile is further characterized by from about 0.05 to about 5 wt % of the polymer eluting below a temperature of 40° C., from about 14 to about 45 wt % of the polymer eluting between 40 and 76° C., from about 35 to about 53 wt % of the polymer eluting between 76 and 86° C., and the remainder of the polymer eluting above a temperature of 86° C.

17. An ethylene polymer having:

a density in a range from about 0.908 to about 0.925 g/cm 3 ;

a melt index in a range from about 0.5 to about 3 g/10 min;

a ratio of Mw/Mn in a range from about 2 to about 4;

a ratio of Mz/Mw in a range from about 1.6 to about 2.3;

a CY-a parameter in a range from about 0.45 to about 0.6; and

an ATREF profile characterized by a single peak at a peak ATREF temperature in a range from about 76 to about 90° C., by less than or equal to about 12 wt % of the polymer eluting above a temperature of 91° C., and by less than or equal to about 0.1 wt % of the polymer eluting above a temperature of 100° C.

18. An article of manufacture comprising the ethylene polymer of claim 17 .

19. The polymer of claim 17 , wherein:

the peak ATREF temperature is in a range from about 77 to about 89° C.;

less than or equal to about 11 wt % of the polymer elutes above a temperature of 91° C.; and

less than or equal to about 0.07 wt % of the polymer elutes above a temperature of 100° C.

20. The polymer of claim 17 , wherein the ethylene polymer:

has a unimodal molecular weight distribution; and

contains less than 0.1 ppm, independently, of hafnium and titanium.

21. The polymer of claim 17 , wherein:

the ethylene polymer further comprises an additive selected from an antioxidant, an acid scavenger, an antiblock additive, a slip additive, a colorant, a filler, a polymer processing aid, a UV additive, or a combination thereof; and

the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or a combination thereof.