Very low density polyethylene blends
Blends of very low density polyethylene produced using metallocene catalysts (mVLDPE) and linear low density polyethylene (LLDPE) are disclosed. The polymer blends include a metallocene-catalyzed VLDPE polymer having a density of less than 0.916 g/cm3, the VLDPE polymer preferably being linear and without long chain branching, and a LLDPE polymer having a density of from 0.916 to 0.940 g/cm3. The polymer blends are particularly suitable in blown and cast film applications.
1. A polymer blend composition, comprising:
(i) a copolymer derived from ethylene and one or more C 3 –C 20 alpha olefin comonomers, said copolymer having:
a) a comonomer content of from 5 to 15 wt. %,
b) a density of less than 0.916 g/cm 3 ,
c) a composition distribution breadth index in the range of from 55% to 70%,
d) a molecular weight distribution Mw/Mn of from 2 to 3,
e) a molecular weight distribution Mz/Mw of less than 2, and
f) a bi-modal composition distribution; and
(ii) a linear low density polyethylene polymer having a density of from 0.916 to 0.940 g/cm 3 .
2. A monolayer film comprising a polymer blend composition, the polymer blend composition comprising:
(i) a copolymer derived from ethylene and one or more C 3 –C 20 alpha olefin comonomers, said copolymer having:
a) a comonomer content of from 5 to 15 wt. %,
b) a density of less than 0.916 g/cm 3 ,
c) a composition distribution breadth index in the range of from 55% to 70%,
d) a molecular weight distribution Mw/Mn of from 2 to 3,
e) a molecular weight distribution Mz/Mw of less than 2, and
f) a bi-modal composition distribution; and
(ii) a linear low density polyethylene polymer having a density of from 0.916 to 0.940 g/cm 3 .
3. A polymer blend composition, comprising:
(i) a copolymer derived from ethylene and one or more C 3 –C 20 alpha olefin comonomers, said copolymer having:
a) a comonomer content of from 5 to 15 wt. %,
b) a density of less than 0.916 g/cm 3 ,
c) a composition distribution breadth index in the range of from 55% to 70%,
d) a molecular weight distribution Mw/Mn of from 2 to 3, and
e) a molecular weight distribution Mz/Mw of less than 2; and
(ii) a linear low density polyethylene polymer having a density of from 0.916 to 0.940 g/cm 3 .
4. The polymer blend composition, or the monolayer film of claim 1 , 2 or 3 , wherein the copolymer is produced using an unbridged bis-Cp metallocene catalyst system.
5. The polymer blend composition, or the monolayer film of claim 1 , 2 or 3 , wherein the copolymer is produced in a gas phase polymerization process.
6. The polymer blend composition, or the monolayer film of claim 1 , 2 or 3 , wherein the copolymer is produced in a gas phase polymerization process at a pressure in the range of from 100 psig to 1000 psig.
7. The polymer blend composition, or the monolayer film of claim 1 , 2 or 3 , wherein the copolymer is produced using an unbridged bis-Cp metallocene catalyst system in a gas phase polymerization process at a pressure in the range of from 100 psig to 1000 psig.
8. The polymer blend composition, or the monolayer film of claim 1 or 2 wherein the copolymer has a melt index of 5 g/10 minutes or less.
9. The polymer blend composition claim 3 , wherein the copolymer has a melt index of 5 g/10 minutes or more.
10. A polymer blend composition, comprising:
(a) a metallocene-catalyzed linear very low density polyethylene polymer having:
(i) a density of less than 0.916 g/cm 3 ,
(ii) a composition distribution breadth index of 50 to 85% by weight,
(iii) a molecular weight distribution Mw/Mn of 2 to 3,
(iv) a molecular weight distribution Mz/Mw of less than 2, and
(v) two peaks in a TREF measurement, and
(b) a linear low density polyethylene polymer having a density of from 0.916 to 0.940 g/cm 3 .
11. A monolayer film formed from a polymer composition blend, the polymer blend composition comprising:
(a) a metallocene-catalyzed linear very low density polyethylene polymer having:
(i) a density of less than 0.916 g/cm 3 ,
(ii) a composition distribution breadth index of 50 to 85% by weight,
(iii) a molecular weight distribution Mw/Mn of 2 to 3,
(iv) a molecular weight distribution Mz/Mw of less than 2, and
(v) two peaks in a TREF measurement, and
(b) a linear low density polyethylene polymer having a density of from 0.916 to 0.940 g/cm 3 .
12. A polymer blend composition, comprising:
(a) a metallocene-catalyzed linear very low density polypropylene polymer having:
(i) a density of less than 0.916 g/cm 3 ,
(ii) a composition distribution breadth index of 50 to 85% by weight,
(iii) a molecular weight distribution Mw/Mn of 2 to 3, and
(iv) a molecular weight distribution Mz/Mw of less than 2, and
(b) a linear low density polyethylene polymer having a density of from 0.916 to 0.940 g/cm 3 .
13. The polymer blend composition, or the monolayer film of claim 10 , 11 or 12 , wherein the very low density polyethylene polymer is a gas-phase metallocene produced very low density polyethylene polymer.
14. The polymer blend composition, or the monolayer film of claim 10 , 11 or 12 , wherein the very low density polyethylene polymer has a density of from 0.900 to 0.915 g/cm 3 .
15. The polymer blend composition or the monolayer film of claim 10 , 11 or 12 , wherein the very low density polyethylene polymer is a comonomer of ethylene and at least one comonomer selected from the group consisting of C 3 to C 12 alpha olefins.
16. The polymer blend composition or the monolayer film of claim 10 , 11 or 12 , wherein the linear low density polyethylene polymer is a metallocene-catalyzed linear low density polyethylene polymer.
17. The polymer blend composition or the monolayer film of claim 10 , 11 or 12 , wherein the linear low density polyethylene polymer is a gas-phase metallocene produced linear low density polyethylene polymer.
18. The polymer blend composition or the monolayer film of claim 10 , 11 or 12 , wherein the linear low density polyethylene polymer is a Ziegler-Natta produced linear low density polyethylene polymer.
19. The polymer blend composition or the monolayer film of claim 10 , 11 or 12 , wherein the linear low density polyethylene polymer has a melt index of from 0.5 to 20 g/10 min.
20. The polymer blend composition or the monolayer film of claim 10 , 11 or 12 , wherein the linear low density polyethylene polymer is a comonomer of ethylene and at least one comonomer selected from the group consisting of C 3 to C 12 linear alpha olefins.
21. The polymer blend composition or the monolayer film of claim 10 , 11 or 12 , wherein the blend comprises 5–80% by weight of the very low density polyethylene polymer and 95–20% by weight of the linear low density polyethylene polymer, based on the total weight of the very low density polyethylene and linear low density polyethylene polymers.
22. The polymer blend composition or the monolayer film of claim 10 , 11 or 12 , wherein the blend further comprises a second very low density polyethylene polymer having a density of less than 0.916 g/cm 3 .
23. The polymer blend composition or the monolayer film of claim 10 , 11 or 12 , wherein the blend further comprises a second linear low density polyethylene polymer having a density of from 0.916 to 0.940 g/cm 3 .
24. The polymer blend composition or the monolayer film of claim 10 or 11 , wherein the very low density polyethylene polymer has a melt index of 5 g/10 min or less.
25. The polymer blend composition claim 12 , wherein the very low density polyethylene polymer has a melt index of 5 g/10 min or more.