Polyethylene composition and film having outstanding properties

Patent metadata

Field	Value
Publication number	US-11352485-B2
Application number	US-201916507477-A
Country	US
Kind code	B2
Filing date	Jul 10, 2019
Priority date	Jul 11, 2018
Publication date	Jun 7, 2022
Grant date	Jun 7, 2022

Abstract

A polyethylene composition comprises a first polyethylene which is an ethylene copolymer having a weight average molecular weight of from 70,000 to 250,000 and a molecular weight distribution Mw/Mn of <2.3, a second polyethylene which is an ethylene copolymer or homopolymer having a weight average molecular weight of from 50,000 to 200,000 and a molecular weight distribution Mw/Mn of <2.3, and a third polyethylene which is an ethylene copolymer or homopolymer having a weight average molecular weight of from 70,000 to 200,000 and a molecular weight distribution Mw/Mn of <2.3, where the first polyethylene has more short chain branching than the second polyethylene or the third polyethylene. The polyethylene composition has a composition distribution breadth index, CDBI50 obtained from a crystallization elution fractionation (CEF) analysis of <45 weight %. A film made from the polyethylene composition may have a machine direction 1% secant modulus of ≥200 MPa (at a film thickness of about 1 mil), a seal initiation temperature (SIT) of ≤85° C. (at a film thickness of about 2 mil), an area of hot tack window (AHTW) of ≥220 Newtons·C° (at a film thickness of about 2 mil), an oxygen transmission rate (OTR) of ≥600 cm3 per 100 inch2 per day (at a film thickness of about 1 mil), a dart impact strength of ≥400 g/mil, and a machine direction (MD) tear strength of ≥400 g/mil.

First claim

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A polyethylene composition comprising:
from 15 to 80 wt % of a first polyethylene which is an ethylene copolymer, the first polyethylene having a weight average molecular weight Mw of from 70,000 to 250,000, a molecular weight distribution Mw/Mn of <2.3 and from 5 to 100 short chain branches per thousand carbon atoms;
from 5 to 50 wt % of a second polyethylene which is an ethylene copolymer or an ethylene homopolymer, the second polyethylene having a weight average molecular weight, Mw of from 50,000 to 200,000, a molecular weight distribution Mw/Mn of <2.3 and from 0 to 15 short chain branches per thousand carbon atoms; and
from 5 to 50 wt % of a third polyethylene which is an ethylene copolymer or an ethylene homopolymer, the third polyethylene having a weight average molecular weight, Mw of from 70,000 to 200,000, a molecular weight distribution Mw/Mn of <2.3 and from 0 to 10 short chain branches per thousand carbon atoms;
wherein:
the number of short chain branches per thousand carbon atoms in the first polyethylene (SCB PE-1 ) is greater than the number of short chain branches per thousand carbon atoms in the second polyethylene (SCB PE-2 ) and the third polyethylene (SCB PE-3 ); and
the polyethylene composition has a density of <0.939 g/cm 3 , a melt index I 2 , determined at 190° C., of from 0.1 to 10 g/10min, and a composition distribution breadth index CDBI 50 obtained from a crystallization elution fractionation (CEF) analysis of <45 w%.

2. The polyethylene composition of claim 1 wherein the weight average molecular weight of the second polyethylene is less than the weight average molecular weight of the first polyethylene.

3. The polyethylene composition of claim 1 wherein the weight average molecular weight of the second polyethylene is less than the weight average molecular weight of the third polyethylene.

4. The polyethylene composition of claim 1 wherein the number of short chain branches per thousand carbon atoms in the third polyethylene (SCB PE-3 ) is greater than the number of short chain branches per thousand carbon atoms in the second polyethylene (SCB PE-2 ).

5. The polyethylene composition of claim 1 wherein the polyethylene composition has composition distribution breadth index CDBI 50 obtained from a crystallization elution fractionation (CEF) analysis of <35 wt% .

6. The polyethylene composition of claim 1 wherein the polyethylene composition has a unimodal profile in a gel permeation chromatograph (GPC).

7. The polyethylene composition of claim 1 wherein the polyethylene composition has a melting peak temperature in a differential scanning calorimetry (DSC) analysis at above 125° C.

8. The polyethylene composition of claim 1 wherein the polyethylene composition has a melting peak temperature in a differential scanning calorimetry (DSC) analysis at below 90° C.

9. The polyethylene composition of claim 1 wherein the polyethylene composition has three melting peaks in a differential scanning calorimetry (DSC) analysis.

10. The polyethylene composition of claim 1 wherein the first polyethylene has from 15 to 50 short chain branches per thousand carbon atoms.

11. The polyethylene composition of claim 1 wherein the second polyethylene is an ethylene homopolymer.

12. The polyethylene composition of claim 1 wherein the third polyethylene is an ethylene copolymer and has from 0.1 to 5 short chain branches per thousand carbon atoms.

13. The polyethylene composition of claim 1 wherein the first polyethylene has a weight average molecular weight, Mw of from 75,000 to 175,000.

14. The polyethylene composition of claim 1 wherein the second polyethylene has a weight average molecular weight, Mw of from 60,000 to 150,000.

15. The polyethylene composition of claim 1 wherein the third polyethylene has a weight average molecular weight, Mw of from 75,000 to 175,000.

16. The polyethylene composition of claim 1 wherein the first polyethylene has a density of from 0.860 to 0.916 g/cm 3 .

17. The polyethylene composition of claim 1 wherein the second polyethylene is an ethylene homopolymer having a density of from 0.930 to 0.980 g/cm 3 .

18. The polyethylene composition of claim 1 wherein the third polyethylene is an ethylene copolymer having a density of from 0.916 to 0.980 g/cm 3 .

19. The polyethylene composition of claim 1 wherein the first polyethylene is present in from 35 to 75 wt %.

20. The polyethylene composition of claim 1 wherein the second polyethylene is present in from 15 to 40 wt %.

21. The polyethylene composition of claim 1 wherein the third polyethylene is present in from 10 to 35 wt %.

22. The polyethylene composition of claim 1 wherein the first polyethylene has a CDBI 50 of at least 75 wt %.

23. The polyethylene composition of claim 1 wherein the third polyethylene is a copolymer with a CDBI 50 of at least 75 wt %.

24. The polyethylene composition of claim 1 wherein the first polyethylene is a homogeneously branched ethylene copolymer.

25. The polyethylene composition of claim 1 wherein the third polyethylene is a homogeneously branched ethylene copolymer.

26. The polyethylene composition of claim 1 wherein the first polyethylene is a made with a single site catalyst.

27. The polyethylene composition of claim 1 wherein the second polyethylene is made with a single site catalyst.

28. The polyethylene composition of claim 1 wherein the third polyethylene is made with a single site catalyst.

29. The polyethylene composition of claim 1 wherein the polyethylene composition has a molecular weight distribution M w /M n of <2.5.

30. The polyethylene composition of claim 1 wherein the polyethylene composition has a molecular weight distribution M w /M n of from 1.5 to 3.5.

31. The polyethylene composition of claim 1 wherein the polyethylene composition has a density of <0.935 g/cm 3 .

32. The polyethylene composition of claim 1 wherein the polyethylene composition has a density of from 0.880 to 0.932 g/cm 3 .

33. The polyethylene composition of claim 1 wherein the polyethylene composition has a melt index, 12 of from 0.1 to 3.0 dg/min.

34. The polyethylene composition of claim 1 wherein the polyethylene composition has a M z /M w of less than 2.3.

35. The polyethylene composition of claim 1 wherein the polyethylene composition has a melt index ratio, I 21 /I 2 of from 15 to 40.

36. A film layer having a thickness of from 0.5 to 10 mil, comprising the polyethylene composition of claim 1 .

37. The film layer of claim 36 wherein the film layer has a machine direction (MD) 1% secant modulus of ≥220 MPa when measured at a film thickness of about 1 mil.

38. The film layer of claim 36 wherein the film layer has a dart impact strength of ≥400 g/mil.

39. The film layer of claim 36 wherein the film layer has a machine direction (MD) tear strength of ≥400 g/mil.

40. The film layer of claim 36 wherein the film layer has a machine direction (MD) 1% secant modulus of ≥200 MPa when measured at a film thickness of about 1 mil; a dart impact strength of ≥

Assignees

• Nova Chem Int Sa

Inventors

• Wang Xiaochuan
• Zoricak Peter
• Molloy Brian
• Wang Qinyan
• Vanasseldonk Lawrence
• Aubee Norman

Classifications

• C08L2205/03

  containing three or more polymers in a blend · CPC title

• C08L2314/06

  Metallocene or single site catalysts · CPC title

• C08J2423/08

  Copolymers of ethene (C08J2423/16 takes precedence) · CPC title

• C08L23/06 Primary

  Polyethylene · CPC title

• C08F110/02

  Ethene · CPC title