Dual catalyst system for producing LLDPE copolymers with improved processability
Disclosed herein are ethylene-based polymers generally characterized by a density from 0.89 to 0.93 g/cm 3 , a ratio of Mw/Mn from 3 to 6.5, a Mz from 200,000 to 650,000 g/mol, a CY-a parameter at 190° C. from 0.2 to 0.4, and a reverse short chain branching distribution. The ATREF profile of these polymers can have a high temperature peak from 92 to 102° C., and a low temperature peak from 18 to 36° C. less than that of the high temperature peak. These polymers can have comparable physical properties to that of a metallocene-catalyzed LLDPE, but with improved processability, shear thinning, and melt strength, and can be used in blown film and other end-use applications.
1. An ethylene polymer having:
a density in a range from about 0.89 to about 0.93 g/cm 3 ;
a ratio of Mw/Mn in a range from about 3 to about 6.5;
a Mz in a range from about 200,000 to about 650,000 g/mol;
a CY-a parameter at 190° C. in a range from about 0.2 to about 0.4;
a number of short chain branches (SCB's) per 1000 total carbon atoms of the polymer at Mz that is greater than at Mn; and
the following polymer fractions in an ATREF test:
from about 0.1 to about 8 wt. % of the polymer eluted below a temperature of 40° C.;
greater than about 45 wt. % of the polymer eluted between 40 and 76° C.;
less than about 36 wt. % of the polymer eluted between 76 and 86° C.; and
from about 1 to about 26 wt. % of the polymer eluted above a temperature of 86° C.
2. An article of manufacture comprising the polymer of claim 1 .
3. The polymer of claim 1 , wherein:
the density is in a range from about 0.902 to about 0.922 g/cm 3 ;
the ratio of Mw/Mn is in a range from about 3.5 to about 6;
the Mz is in a range from about 210,000 to about 575,000 g/mol; and
the CY-a parameter at 190° C. is in a range from about 0.24 to about 0.38.
4. The polymer of claim 3 , 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. A blown or cast film comprising the polymer of claim 4 , wherein the film has an average thickness in a range from about 0.5 to about 8 mils.
6. The polymer of claim 1 , wherein:
from about 0.5 to about 7 wt. % of the polymer is eluted below a temperature of 40° C.;
from about 46 to about 90 wt. % of the polymer is eluted between 40 and 76° C.;
from about 4 to about 35 wt. % of the polymer is eluted between 76 and 86° C.; and
from about 2 to about 25 wt. % of the polymer is eluted above a temperature of 86° C.
7. An article of manufacture comprising the polymer of claim 6 .
8. The polymer of claim 1 , wherein the ethylene polymer has:
a Mw in a range from about 80,000 to about 180,000 g/mol; and
an D3 parameter in a range from about 1.1 to about 1.4.
9. The polymer of claim 1 , wherein the ethylene polymer has:
a melt index in a range from about 0.5 to about 5 g/10 min; and
a ratio of HLMI/MI in a range from about 28 to about 42.
10. The polymer of claim 1 , wherein the ethylene polymer contains less than 0.008 long chain branches per 1000 total carbon atoms.
11. The polymer of claim 1 , wherein the ethylene polymer is further characterized by an ATREF profile having a first peak and a second peak, wherein:
the second peak is at a temperature from about 92 to about 102° C.; and
the first peak is at a temperature from about 18 to about 36° C. less than that of the second peak.
12. An article of manufacture comprising the polymer of claim 11 .
13. An ethylene polymer having:
a density in a range from about 0.89 to about 0.93 g/cm 3 ;
a ratio of Mw/Mn in a range from about 3 to about 6.5;
a Mz in a range from about 200,000 to about 650,000 g/mol;
a CY-a parameter at 190° C. in a range from about 0.2 to about 0.4;
a number of short chain branches (SCB's) per 1000 total carbon atoms of the polymer at Mz that is greater than at Mn; and
an ATREF profile characterized by a first peak and a second peak, with the second peak at a temperature from about 92 to about 102° C., and the first peak at a temperature from about 18 to about 36° C. less than that of the second peak.
14. The polymer of claim 13 , wherein the first peak is at a temperature in a range from about 60 to about 80° C.
15. The polymer of claim 13 , wherein the first peak is at a temperature from about 20 to about 34° C. less than that of the second peak.
16. The polymer of claim 13 , wherein the second peak is at a temperature in a range from about 93 to about 100° C.
17. The polymer of claim 13 , wherein the ethylene polymer has:
a Mw in a range from about 80,000 to about 180,000 g/mol;
an D3 parameter in a range from about 1.1 to about 1.4;
a melt index in a range from about 0.5 to about 5 g/10 min; and
a ratio of HLMI/MI in a range from about 28 to about 42.
18. An article of manufacture comprising the polymer of claim 17 .
19. The polymer of claim 1 , wherein the ethylene polymer is an ethylene/α-olefin copolymer further characterized by:
a density in a range from about 0.902 to about 0.928 g/cm 3 ;
a ratio of Mw/Mn is in a range from about 3.2 to about 5.8;
a Mz in a range from about 210,000 to about 575,000 g/mol; and
a ratio of HLMI/MI in a range from about 25 to about 45.
20. The polymer of claim 13 , wherein the ethylene polymer is an ethylene/α-olefin copolymer further characterized by:
a density in a range from about 0.902 to about 0.928 g/cm 3 ;
a ratio of Mw/Mn is in a range from about 3.2 to about 5.8;
a Mz in a range from about 210,000 to about 575,000 g/mol; and
a ratio of HLMI/MI in a range from about 25 to about 45.