Peroxide treated metallocene-based polyolefins with improved melt strength
Disclosed herein are ethylene-based polymers having low densities and narrow molecular weight distributions, but high melt strengths for blown film processing. Such polymers can be produced by peroxide-treating a metallocene-catalyzed resin.
1. An ethylene polymer having a ratio of Mw/Mn of less than or equal to about 5, a ratio of Mz/Mw of less than or equal to about 2.3, a zero-shear viscosity at 190° C. of greater than or equal to about 8×10 4 Pa-sec, a peak melting point in a range from about 100 to about 120° C., a vicat softening temperature in a range from about 95 to about 110° C., and a difference between the peak melting point and the vicat softening temperature of less than or equal to about 16° C.
2. The polymer of claim 1 , wherein the polymer has:
a melt index in a range from about 0.05 to about 2;
a ratio of HLMI/MI in a range from about 15 to about 50; and
a density in a range from about 0.895 to about 0.928 g/cm 3 .
3. The polymer of claim 1 , wherein the polymer has:
a ratio of Mw/Mn in a range from about 2 to about 5;
a ratio of Mz/Mw in a range from about 1.5 to about 2.3;
a Mw in a range from about 75,000 to about 250,000 g/mol;
a Mn in a range from about 10,000 to about 70,000 g/mol; or
a Mz in a range from about 175,000 to about 300,000 g/mol; or
any combination thereof.
4. The polymer of claim 1 , wherein the polymer is an ethylene/α-olefin copolymer.
5. The polymer of claim 4 , wherein the polymer has:
a ratio of Mw/Mn in a range from about 2 to about 5;
a ratio of Mz/Mw in a range from about 1.5 to about 2.3; and
a zero-shear viscosity at 190° C. in a range from about 8×10 4 to about 2×10 6 Pa-sec.
6. An article of manufacture comprising the ethylene polymer of claim 1 .
7. A blown or cast film comprising the ethylene polymer of claim 1 , wherein the film has a thickness in a range from about 1 to about 200 mils.
8. The film of claim 7 , wherein, in a stress versus strain curve in the transverse direction (TD) for a 10-mil film, a ratio of the maximum stress at a strain of less than 40% to the maximum stress at a strain in the 40% to 60% range is in a range from about 0.85 to 1.
9. The film of claim 7 , wherein, in a stress versus strain curve in the transverse direction (TD) for a 1-mil film, a ratio of the maximum stress at a strain of less than 40% to the maximum stress at a strain in the 40% to 60% range is in a range from about 0.85 to 1.1.
10. The film of claim 7 , wherein, in a stress versus strain curve in the transverse direction (TD) for a 10-mil film,
the slope is not negative in the 25% to 50% strain range; or
the stress at 50% strain is greater than the stress at the yield point; or
both.
11. The polymer of claim 1 , wherein the polymer has a CY-a parameter at 190° C. in a range from about 0.08 to about 0.28.
12. The polymer of claim 1 , wherein the polymer has from about 0.01 to about 0.03 long chain branches (LCB) per 1000 total carbon atoms.
13. An ethylene/α-olefin copolymer having:
a ratio of Mw/Mn in a range from about 2.1 to about 3.5;
a ratio of Mz/Mw in a range from about 1.5 to about 2.2;
a melt index in a range from 0 to about 1;
a zero-shear viscosity at 190° C. in a range from about 1×10 5 to about 1×10 6 Pa-sec;
a CY-a parameter at 190° C. in a range from about 0.1 to about 0.2;
a density in a range from about 0.91 to about 0.92 g/cm 3 ; and
from about 0.01 to about 0.03 long chain branches (LCB) per 1000 total carbon atoms.
14. The copolymer of claim 13 , wherein the copolymer has:
a melt index in a range from about 0.1 to about 1; and
a ratio of HLMI/MI in a range from about 15 to about 50.
15. The copolymer of claim 13 , wherein the copolymer has:
a Mw in a range from about 75,000 to about 250,000 g/mol; and
a peak melting point in a range from about 105 to about 120° C.
16. The copolymer of claim 13 , wherein the copolymer has:
a Mn in a range from about 10,000 to about 70,000 g/mol; and
a vicat softening temperature in a range from about 95 to about 110° C.
17. The copolymer of claim 13 , wherein the copolymer has:
a Mz in a range from about 175,000 to about 300,000 g/mol; and
a difference between a peak melting point and a vicat softening temperature of less than or equal to about 16° C.
18. An article of manufacture comprising the copolymer of claim 13 .
19. A blown or cast film comprising the copolymer of claim 13 , wherein the film has a thickness in a range from about 1 to about 200 mils.
20. The film of claim 19 , wherein, in a stress versus strain curve in the transverse direction (TD) for a 10-mil film, a ratio of the maximum stress at a strain of less than 40% to the maximum stress at a strain in the 40% to 60% range is in a range from about 0.85 to 1.
21. The film of claim 19 , wherein, in a stress versus strain curve in the transverse direction (TD) for a 1-mil film, a ratio of the maximum stress at a strain of less than 40% to the maximum stress at a strain in the 40% to 60% range is in a range from about 0.85 to 1.1.
22. The film of claim 19 , wherein, in a stress versus strain curve in the transverse direction (TD) for a 10-mil film,
the slope is not negative in the 25% to 50% strain range; or
the stress at 50% strain is greater than the stress at the yield point; or
both.
23. An ethylene/l-hexene copolymer having:
a ratio of Mw/Mn of less than or equal to about 5;
a ratio of Mz/Mw of less than or equal to about 2.3;
a zero-shear viscosity at 190° C. in a range from about 1×10 5 to about 1×10 6 Pa-sec;
a CY-a parameter at 190° C. in a range from about 0.08 to about 0.28;
a density in a range from about 0.905 to about 0.925 g/cm 3 ; and
from about 0.008 to about 0.04 long chain branches (LCB) per 1000 total carbon atoms.
24. The copolymer of claim 23 , wherein the copolymer has:
a ratio of Mw/Mn in a range from about 2 to about 3.5; and
a ratio of Mz/Mw in a range from about 1.5 to about 2.2.
25. An article of manufacture comprising the copolymer of claim 24 .
26. A blown or cast film comprising the copolymer of claim 24 , wherein the film has a thickness in a range from about 1 to about 200 mils.
27. The film of claim 26 , wherein:
in a stress versus strain curve in the transverse direction (TD) for a 10-mil film, a ratio of the maximum stress at a strain of less than 40% to the maximum stress at a strain in the 40% to 60% range is in a range from about 0.85 to 1;
in a stress versus strain curve in the transverse direction (TD) for a 1-mil film, a ratio of the maximum stress at a strain of less than 40% to the maximum stress at a strain in the 40% to 60% range is in a range from about 0.85 to 1.1;
in a stress versus strain curve in the transverse direction (TD) for a 10-mil film, the slope is not negative in the 25% to 50% strain range; or
in a stress versus strain curve in the transverse direction (TD) for a 10-mil film, the stress at 50% strain is greater than the stress at the yield point; or
any combination thereof.