Polyethylene composition and film having retained dart impact

Patent metadata

Field	Value
Publication number	US-11306196-B2
Application number	US-201916507616-A
Country	US
Kind code	B2
Filing date	Jul 10, 2019
Priority date	Jul 11, 2018
Publication date	Apr 19, 2022
Grant date	Apr 19, 2022

Abstract

A polyethylene composition including 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 M w /M n of <2.3, a second polyethylene which is an ethylene copolymer or homopolymer having a weight average molecular weight of less than 75,000 and a molecular weight distribution M w /M n of <2.3, and a third polyethylene which is an ethylene copolymer or homopolymer having a weight average molecular weight of from 100,000 to 300,000 and a molecular weight distribution M w /M n 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 soluble fraction in a CEF analysis of at least 15 weight percent. 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) and an oxygen transmission rate (OTR) of ≥700 cm 3 per 100 inch 2 per day (at a film thickness of about 1 mil). A film made from the polyethylene composition retains much of its dart impact performance on downgauging from a thickness of 1 mil to a thickness of 0.75 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 75 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 M w /M n of <2.3 and from 5 to 100 short chain branches per thousand carbon atoms;
from 5 to 80 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 less than 75,000, a molecular weight distribution M w /M n of <2.3 and from 0 to 20 short chain branches per thousand carbon atoms; and
from 5 to 60 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 100,000 to 300,000, a molecular weight distribution M w /M n of >2.3 and from 0 to 75 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 );
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 ); and
the weight average molecular weight of the second polyethylene is less than the weight average molecular weight of the first polyethylene and the third polyethylene; wherein,
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 dg/min, a melt flow ratio, I 21 /I 2 of greater than 40 and has a soluble fraction in a crystallization elution fractionation (CEF) analysis of at least 15 weight percent.

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

3. The polyethylene composition of claim 1 wherein the polyethylene composition has a soluble fraction in a crystallization elution fractionation (CEF) analysis of at least 20 weight percent.

4. 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.

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

6. The polyethylene composition of claim 1 wherein the first polyethylene has from 25 to 75 short chain branches per thousand carbon atoms.

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

8. The polyethylene composition of claim 1 wherein the third polyethylene is an ethylene copolymer and has from 5 to 50 short chain branches per thousand carbon atoms.

9. The polyethylene composition of claim 1 wherein the first polyethylene has a weight average molecular weight, Mw of from 75,000 to 200,000.

10. The polyethylene composition of claim 1 wherein the second polyethylene has a weight average molecular weight, Mw of from 15,000 to 40,000.

11. The polyethylene composition of claim 1 wherein the third polyethylene has a weight average molecular weight, Mw of from 100,000 to 240,000.

12. The polyethylene composition of claim 1 wherein the first polyethylene has a density of from 0.865 to 0.916 g/cm 3 .

13. The polyethylene composition of claim 1 wherein the second polyethylene is an ethylene homopolymer having a density of from 0.940 to 0.980 g/cm 3 .

14. The polyethylene composition of claim 1 wherein the third polyethylene is an ethylene copolymer having a density of from 0.880 to 0.936 g/cm 3 .

15. The polyethylene composition of claim 1 wherein the first polyethylene is present in from 20 to 70 wt %.

16. The polyethylene composition of claim 1 wherein the second polyethylene is present in from 15 to 60 wt %.

17. The polyethylene composition of claim 1 wherein the third polyethylene is present in from 5 to 50 wt %.

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

19. The polyethylene composition of claim 1 wherein the third polyethylene is a copolymer with a CDBI 50 of less than 75 wt %.

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

21. The polyethylene composition of claim 1 wherein the third polyethylene is a heterogeneously branched ethylene copolymer.

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

23. The polyethylene composition of claim 1 wherein the third polyethylene is made with a Ziegler-Natta catalyst.

24. The polyethylene composition of claim 1 wherein the polyethylene composition has a molecular weight distribution M w /M n of from 2.3 to 8.0.

25. The polyethylene composition of claim 1 wherein the polyethylene composition has a molecular weight distribution M w /M n of from 2.5 to 6.5.

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

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

28. The polyethylene composition of claim 1 wherein the polyethylene composition has a melt index, I 2 of from 0.1 to 3.0 dg/min.

29. The polyethylene composition of claim 1 wherein the polyethylene composition has a Mz/M w of less than 4.0.

30. The polyethylene composition of claim 1 wherein the polyethylene composition has a melt index ratio, I 21 /I 2 of from greater than 40 to 100.

31. The polyethylene composition of claim 1 wherein the polyethylene composition has a melt index ratio, I 21 /I 2 of greater than 45.

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

33. The polyethylene composition of claim 1 , which when made into a film layer having a thickness of about 1 mil exhibits a machine direction (MD) 1% secant modulus of ≥200 MPa.

34. The polyethylene composition of claim 1 , which when made into a film layer having a thickness of about 1 mil exhibits an oxygen transmission rate (OTR) of ≥700 cm 3 per 100 inches 2 per day.

35. The polyethylene composition of claim 1 , which when made into a film layer having a thickness of about 1 mil exhibits a machine direction (MD) 1% secant modulus of ≥200 MPa and an oxygen transmission rate (OTR) of ≥700 cm 3 per 100 inches 2 per day.

36. The polyethylene composition of claim 1 , which when made into a film layer having a thickness of about 1 mil exhibits a first dart impact value in g/mil and when made into a film layer having a thickness of about 0.75 mil exhibits a second dart impact value in g/mil; wherein the second dart impact value is within 15 percent of the first dart impact value.

37. A film comprisin

Assignees

• Nova Chem Int Sa

Inventors

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

Classifications

• C08L2314/02

  Ziegler natta catalyst · CPC title

• C08L2205/03

  containing three or more polymers in a blend · CPC title

• C08J5/18

  Manufacture of films or sheets · CPC title

• C08L2314/06

  Metallocene or single site catalysts · CPC title

• C08F210/16 Primary

  Copolymers of ethene with alpha-alkenes, e.g. EP rubbers · CPC title