Linear ethylene interpolymer blends of interpolymers having narrow molecular weight and composition distributions

• US 5,382,631 A
• Filed: 06/04/1993
• Issued: 01/17/1995
• Est. Priority Date: 09/30/1988
• Status: Expired due to Term

• Current Assignee: Exxon Chemical Patents Inc. (Exxon Mobil Corporation)
• Original Assignee: Exxon Chemical Patents Inc. (Exxon Mobil Corporation)
• Inventors: Welborn, deceased, Howard C. Jr., Speed, Charles S., Stehling, Ferdinand C.
• Primary Examiner(s): Seccuro, Jr., Carman J.
• Application Number:
  US08/073,362
• Time in Patent Office: 592 Days
• Field of Search: 525/240
• US Class Current: 525/240
• CPC Class Codes: C08L 2205/02 containing two or more polymers of the same C08L -group
• CPC Class Codes: C08L 2205/025 containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure
• CPC Class Codes: C08L 23/0815 Copolymers of ethene with aliphatic 1-olefins
• CPC Class Codes: C08L 23/16 Elastomeric ethene-propene or ethene-propene-diene copolymers, e.g. EPR and EPDM rubbers
• CPC Class Codes: C08L 2314/06 Metallocene or single site catalysts
• CPC Class Codes: C08L 2666/04 Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof

Abstract

Linear interpolymer blends are disclosed. The blends are made from components having a narrow molecular weight distribution (e.g. Mw/Mn≦3) and a narrow composition distribution (e.g. CDBI>50%). The blend components of the blend can all have the same molecular weight but different comonomer contents, the same comonomer content but different molecular weights, or comonomer contents which increase with molecular weight. The blends have either Mw/Mn>3 and/or CDBI<50%, and combinations of each, and can be bimodal with respect to either or both molecular weight and/or comonomer content. The blends are generally free of blend components having both a higher average molecular weight and a lower average comonomer content than another blend component. The blends can have improved mechanical, physical and/or chemical properties. Single or multilayer films having enhanced physical properties are made from the blends. Also, the interpolymer blends of this invention can be blended or coextruded with other polymers to further enhance processability of and the physical characteristics of the blends.

Claims

1. A polymer blend comprising:

a plurality of linear at least partially crystalline ethylene interpolymer components comprising ethylene and at least one alpha olefin comonomer, each component having a a different average molecular weight, Mw/Mn≦

3, a density in the range of 0.88 to less than 0.940 g/cm³ and a composition distribution breadth index of at least 50%;

said blend being essentially free of blend components having both a higher average molecular weight and a lower average comonomer content than that of any other components; and

said blend has a density in the range of from about 0.88 g/cm³ to less than 0.900 g/cm³ and a Mw/Mn>

3.

2. The blend in accordance with claim 1, wherein said blend components have an alpha-olefin comonomer content in the range of 1 to 30 mole percent and an ethylene content in the range of 99 to 70 mole percent.

3. The blend in accordance with claim 1, wherein said blend components are selected from the group consisting of:

poly(ethylene-co-alpha-olefin) plastomers;

very low density linear polyethylenes;

linear, low density polyethylenes.

4. The blend in accordance with claim 1, wherein the blend components have essentially the same comonomer content and different molecular weights.

5. The blend in accordance with claim 1, wherein the molecular weights and the comonomer contents of the blend components are both different.

6. The blend in accordance with claim 1, wherein the value of Mw/Mn for each blend component is less than or equal to 2.7.

7. The blend in accordance with claim 1, wherein the composition distribution breadth index for each blend component is greater than about 70%.

8. A polymer film comprising at least one layer, said layer comprising a blend of a plurality of linear at least partially crystalline ethylene interpolymer components comprising ethylene and at least one alpha-olefin comonomer, each having a different average molecular weight, a Mw/Mn≦

3, a density in the range of from about 0.88 g/cm³ to about 0.94 g/cm³ , and a CDBI greater than 50% said blend being essentially free of components having both a higher average molecular weight and a lower average comonomer content than that of any other component and a Mw/Mn>

3.

9. The film of claim 8 wherein said components have a CDBI>

60%.

10. The film of claim 8 wherein said film consists essentially of said layer.

11. The film in accordance with claim 8 wherein said components have an alpha-olefin content in the range of 1 to 30 mole percent and an ethylene content in the range of 99 to 70 mole percent.

12. A polymer blend comprising a plurality of linear at least partially crystalline ethylene interpolymer components comprising ethylene and at least one alpha-olefin comonomer, each having a different average molecular weight, a density in the range of from 0.88 g/cm³ to 0.940 g/cm³ , a Mw/Mn≦

3 and a CDBI greater than 50%;

said blend being essentially free of said components having both a higher average molecular weight and a lower average comonomer content than that of any other component and said blend having a Mw/Mn>

3.

13. The blend of claim 12 wherein said blend has a density greater than 0.88 g/cm³.

14. The blend of claim 12 wherein said components have a CDBI greater than 60%.

15. A film having at least one layer comprising said blend of claim 12.

16. A polymer blend composition comprising:

a plurality of linear at least partially crystalline ethylene interpolymers comprising ethylene and at least one α

-olefin comonomer, each of said components having a different average molecular weight, a Mw/Mn≦

3, a CDBI of at least 50% and a density greater than or equal to 0.88 to about 0.915 g/cm³ ;

the composition having a density in the range of greater than or equal to 0.88 g/cm³ to about 0.915 g/cm³ and a Mw/Mn>

3;

wherein the composition is essentially free of blend components having both a higher average molecular weight and a lower average comonomer content than that of any other component.

17. The composition of claim 16 wherein said components have an α

-olefin comonomer content in the range of 1 to 30 mole percent and an ethylene content in the range of 99 to 70 mole percent.

18. The composition of claim 16 wherein said components have essentially the same comonomer content.

19. The composition of claim 16 wherein said components have both a different molecular weight and comonomer content.

20. The composition of claim 16 wherein each of said components have a Mw/Mn less than or equal to 2.5.

21. The composition of claim 16 wherein each of said components have a CDBI greater than about 60%.

22. The composition of claim 16 wherein each of said components have a CDBI greater than 70%.

23. The composition of claim 16 wherein at least one of said components has a CDBI greater than 70%.

24. The composition of claim 16 wherein said components consist of at least one of the group of very low density linear polyethylenes and linear low density polyethylenes.

25. The composition of claim 16 wherein said components have a Mw/Mn≦

2.5 and a CDBI greater than 70%.

26. A polymer blend composition comprising:

a plurality of linear at least partially crystalline ethylene interpolymer components comprising ethylene and at least one α

-olefin comonomer, each of said components having a different average molecular weight, a Mw/Mn≦

3, a CDBI greater than 50% and a density greater than or equal to 0.88 g/cm³ ;

said composition having a density in the range of about 0.88 g/cm³ to about 0.940 g/cm³, a Mw/Mn>

3 and a CDBI greater than 50%;

wherein the composition is essentially free of said components having both a higher average molecular weight and a lower average comonomer content than that of any other component.

27. The composition of claim 26 wherein said components have an α

-olefin comonomer content in the range of 1 to 30 mole percent and an ethylene content in the range of 99 to 70 mole percent.

28. The composition of claim 26 wherein said components have essentially the same comonomer content and different molecular weights.

29. The composition of claim 26 wherein each of said components have a Mw/Mn less than or equal to 2.5.

30. The composition of claim 26 wherein each of said components have a CDBI greater than about 60%.

31. The composition of claim 26 wherein each of said components have a CDBI greater than 70%.

32. A polymer blend composition comprising:

a plurality of linear at least partially crystalline ethylene interpolymer components comprising ethylene and at least one C₃ -C₁₂ α

-olefin comonomer, each of said interpolymers having a different average molecular weight, a Mw/Mn≦

3, a CDBI greater than 50% and a density greater than or equal to 0.88 g/cm³ ; and

a high density polyethylene component;

said composition having a density greater than or equal to 0.88 g/cm³, and a Mw/Mn>

3;

wherein the composition is essentially free of said components having both a higher average molecular weight and a lower average comonomer content than that of any other component.

33. The composition of claim 32 wherein said interpolymer components have a CDBI of at least 60%.

34. The composition of claim 32 wherein at least one of said interpolymer components has a CDBI of at least 70%.

35. The composition of claim 32 wherein the composition has a density in the range of 0.88 g/cm³ to about 0.940 g/cm³.