Peroxide treated metallocene-based polyolefins with improved melt strength

Patent metadata

Field	Value
Publication number	US-9732197-B2
Application number	US-201615134464-A
Country	US
Kind code	B2
Filing date	Apr 21, 2016
Priority date	May 14, 2013
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

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.

First claim

The invention claimed is:

1. A process for preparing 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, and a zero-shear viscosity at 190° C. of greater than or equal to about 8×10 4 Pa-sec, the process comprising:
contacting a base resin with a peroxide compound at a temperature in a range from about 120 to about 300° C. to generate peroxide groups at about 10-50 ppm of peroxide groups based on the weight of the base resin.

2. The process of claim 1 , wherein the step of contacting the base resin with the peroxide compound comprises melt processing a mixture of the base resin and the peroxide compound in a twin screw extrusion system.

3. The process of claim 2 , wherein the base resin is produced using a metallocene-based catalyst system.

4. the process of claim 1 , wherein the ethylene polymer has from about 0.008 to about 0.04 long chain branches (LCB) per 1000 total carbon atoms.

5. The process of claim 1 , wherein:
the ratio of Mw/Mn is in a range from about 2 to about 5;
the ratio of Mz/Mw is a range from about 1.5 to about 2.3; and
the zero-shear viscosity at 190° C. is in a range from about 8×10 4 to about 2×10 6 Pa-sec.

6. The process of claim 5 , wherein the ethylene polymer is an ethylene/α-olefin copolymer.

7. The process of claim 6 , wherein the ethylene/α-olefin copolymer has:
a peak melting point in a range from about 100 to about 120° C.;
a difference between the peak melting point and the vicat softening temperature of less than or equal to about 18° C.;
a zero-shear viscosity at 190° C. in a range from about 1×10 5 to about 1×10 6 Pa-sec; and
a CY-a parameter at 190° C. in a range from about 0.08 to about 0.28.

8. The process of claim 5 , wherein:
the ethylene polymer is an ethylene/α-olefin copolymer characterized by a peak melting point in a range from about 100 to about 120° C., and a difference between the peak melting point and the vicat softening temperature of less than or equal to about 18° C.; and
the base resin is characterized by a peak melting point in a range from about 100 to about 120° C., and a difference between the peak melting point and the vicat softening temperature of less than or equal to about 18° C.

9. The process of claim 5 , wherein:
the ethylene polymer is an ethylene/α-olefin copolymer characterized by a zero-shear viscosity at 190° C. in a range from about 1×10 5 to about 1×10 6 Pa-sec, and a CY-a parameter at 190° C. in a range from about 0.08 to about 0.28; and
the base resin is characterized by a zero-shear viscosity at 190° C. in a range from about 2×10 3 to about 7×10 4 Pa-sec, and a CY-a parameter at 190° C. in a range from about 0.4 to about 0.8.

10. The process of claim 5 , wherein:
the ethylene polymer has from about 0.009 to about 0.035 long chain branches (LCB) per 1000 total carbon atoms; and
the base resin has less than about 0.005 long chain branches (LCB) per 1000 total carbon atoms.

11. The process of claim 1 , wherein the ethylene polymer has:
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; and
a zero-shear viscosity at 190° C. in a range from about 1×10 5 to about 1×10 6 Pa-sec.

12. The process of claim 11 , wherein the ethylene polymer has a CY-a parameter at 190° C. in a range from about 0.1 to about 0.2.

13. The process of claim 11 , wherein the ethylene polymer has from about 0.01 to about 0.03 long chain branches (LCB) per 1000 total carbon atoms.

14. The process of claim 11 , wherein the ethylene polymer has a peak melting point in a range from about 105 to about 120° C.

15. The process of claim 11 , wherein the ethylene polymer is an ethylene/α-olefin copolymer with a density in a range from about 0.91 to about 0.92 g/cm 3 .

16. The process of claim 15 , wherein the ethylene/α-olefin copolymer is an ethylene/1-hexene copolymer.

17. The process of claim 11 , wherein the base resin has:
a ratio of Mw/Mn in a range from about 2 to about 3.5;
a ratio of Mz/Mw in a range from about 1.5 to about 2.2; and
a melt index in a range from about 0.5 to about 2.

18. The process of claim 17 , wherein the base resin has:
a zero-shear viscosity at 190° C. in a range from about 3×10 3 to about 2×10 4 Pa-sec;
a CY-a parameter at 190° C. in a range from about 0.5 to about 0.8; and
less than about 0.005 long chain branches (LCB) per 1000 total carbon atoms.

19. The process of claim 1 , wherein the ethylene polymer is an ethylene/1-hexene copolymer characterized by:
a ratio of Mw/Mn in a range from about 2 to about 3.5;
a ratio of Mz/Mw in a range from about 1.5 to about 2.2; and
a density in a range from about 0.905 to about 0.925 g/cm 3 .

20. The process of claim 19 , wherein the ethylene/1-hexene copolymer has:
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; and
from about 0.008 to about 0.04 long chain branches (LCB) per 1000 total carbon atoms.

Assignees

• Chevron Phillips Chemical Co Lp

Inventors

• Cui Lili
• Sukhadia Ashish M
• Rohatgi Vivek

Classifications

• C08J2323/06

  Polyethene · CPC title

• B29C48/022

  characterised by the choice of material · CPC title

• B29K2105/0094

  having particular viscosity · CPC title

• C08F2810/10

  including a reactive processing step which leads, inter alia, to morphological and/or rheological modifications, e.g. visbreaking · CPC title

• C08J5/18 Primary

  Manufacture of films or sheets · CPC title