Polyethylene copolymer compositions and their barrier properties

Patent metadata

Field	Value
Publication number	US-12091530-B2
Application number	US-201917311652-A
Country	US
Kind code	B2
Filing date	Dec 13, 2019
Priority date	Dec 20, 2018
Publication date	Sep 17, 2024
Grant date	Sep 17, 2024

Abstract

A dual reactor solution polymerization process gives high density polyethylene compositions containing a first ethylene copolymer and a second ethylene copolymer. The polyethylene compositions can be used in the manufacture of injection molded closures or cast film having good barrier properties.

First claim

The invention claimed is:

1. A polyethylene copolymer composition comprising:
(1) 10 to 70 wt % of a first ethylene copolymer having a melt index I 2 1 , of from 0.1 to 10 g/10 min; a molecular weight distribution M w /M n , of less than 3.0; and a density of from 0.930 to 0.960 g/cm 3 ; and
(2) 90 to 30 wt % of a second ethylene copolymer having a melt index I 2 2 , of from 1 to 45 g/10 min; a molecular weight distribution M w /M n , of less than 3.0; and a density higher than the density of the first ethylene copolymer, but less than 0.970 g/cm 3 ;
wherein the density of the second ethylene copolymer is less than 0.031 g/cm 3 higher than the density of the first ethylene copolymer; the melt index, I 2 1 , of the first ethylene copolymer is less than the melt index, I 2 2 , of the second ethylene copolymer; a ratio (SCB1/SCB2) of the number of short chain branches per thousand carbon atoms in the first ethylene copolymer (SCB1) to the number of short chain branches per thousand carbon atoms in the second ethylene copolymer (SCB2) is greater than 2.0; and wherein the polyethylene copolymer composition has a molecular weight distribution M w /M n , of from 1.8 to 7.0; a density of at least 0.949 g/cm 3 ; a high load melt index I 21 , of at least 200 g/10 min; a Z-average molecular weight M z , of less than 200,000; a melt flow ratio I 21 /I 2 , of less than 40, wherein the I 21 and the I 2 are the melt indices determined for the polyethylene copolymer composition using a 21.6 kg weight and a 2.16 kg weight, respectively; and a stress exponent of less than 1.40.

2. The polyethylene copolymer composition of claim 1 wherein the polyethylene copolymer composition has a melt index I 2 , of from 5.0 to 40.0 g/10 min.

3. The polyethylene copolymer composition of claim 1 wherein the density of the second ethylene copolymer is less than 0.020 g/cm 3 higher than the density of the first ethylene copolymer.

4. The polyethylene copolymer composition of claim 1 wherein the first ethylene copolymer has a melt index I 2 1 , of from 0.1 to 5.0 g/10 min.

5. The polyethylene copolymer composition of claim 1 wherein the polyethylene copolymer composition has a high load melt index I 21 , of from 250 to 750 g/10 min.

6. The polyethylene copolymer composition of claim 1 wherein the polyethylene copolymer composition has a unimodal molecular weight distribution as determined by gel permeation chromatography.

7. The polyethylene copolymer composition of claim 1 wherein the ratio (SCB1/SCB2) of the number of short chain branches per thousand carbon atoms in the first ethylene copolymer (SCB1) to the number of short chain branches per thousand carbon atoms in the second ethylene copolymer (SCB2) is at least 2.5.

8. The polyethylene copolymer composition of claim 1 wherein the polyethylene composition has a molecular weight distribution M w /M n , of from 1.8 to 4.0.

9. The polyethylene copolymer composition of claim 1 wherein the first ethylene copolymer has a density of from 0.936 to 0.952 g/cm 3 .

10. The polyethylene copolymer composition of claim 1 wherein the second ethylene copolymer has a density of less than 0.963 g/cm 3 .

11. The polyethylene copolymer composition of claim 1 wherein the polyethylene copolymer composition has a density of from 0.951 to 0.960 g/cm 3 .

12. The polyethylene copolymer composition of claim 1 wherein the polyethylene copolymer composition has no long chain branching.

13. The polyethylene copolymer composition of claim 1 wherein the polyethylene copolymer composition has a composition distribution breadth index CDBI(50) of greater than 65 wt %.

14. The polyethylene copolymer composition of claim 1 wherein the polyethylene copolymer composition comprises:
from 20 to 55 wt % of the first ethylene copolymer; and
from 80 to 45 wt % of the second ethylene copolymer.

15. The polyethylene copolymer composition of claim 1 wherein the first and second ethylene copolymers are copolymers of ethylene and 1-octene.

16. The polyethylene copolymer composition of claim 1 wherein the polyethylene copolymer composition further comprises a nucleating agent.

17. The polyethylene copolymer composition of claim 16 , which when made into a PCO 1881 CSD closure, has an OTR of less than 0.0030 cm 3 /closure/day.

18. The polyethylene copolymer composition of claim 16 wherein the nucleating agent is a salt of a dicarboxylic acid compound.

19. The polyethylene copolymer composition of claim 18 wherein the polyethylene copolymer composition comprises from 20 to 4000 ppm of the nucleating agent based on the combined weight of the first ethylene copolymer and the second ethylene copolymer.

20. The polyethylene copolymer composition of claim 1 , wherein the polyethylene copolymer composition is made by a process comprising contacting at least one single site polymerization catalyst system with ethylene under solution polymerization conditions in at least two polymerization reactors.

21. An injection molded article comprising the polyethylene copolymer composition of claim 1 .

22. A compression molded article comprising the polyethylene copolymer composition of claim 1 .

23. A closure comprising the polyethylene copolymer composition of claim 1 .

24. A film comprising the polyethylene copolymer composition of claim 1 .

25. A cast film comprising the polyethylene copolymer composition of claim 1 .

26. A film comprising the polyethylene copolymer composition of claim 16 and having a normalized OTR of ≤100 cm 3 /100 in 2 /day.

27. A film comprising the polyethylene copolymer composition of claim 16 and having a normalized WVTR of ≤0.250 g/100 in 2 /day.

28. A process to prepare a polyethylene copolymer composition, the polyethylene copolymer composition comprising:
(1) 10 to 70 wt % of a first ethylene copolymer having a melt index I 2 1 , of from 0.1 to 10 g/10 min; a molecular weight distribution M w /M n , of less than 3.0; and a density of from 0.930 to 0.960 g/cm 3 ; and
(2) 90 to 30 wt % of a second ethylene copolymer having a melt index I 2 2 , of from 1 to 45 g/10 min; a molecular weight distribution M w /M n , of less than 3.0; and a density higher than the density of the first ethylene copolymer, but less than 0.970 g/cm 3 ;
wherein the density of the second ethylene copolymer is less than 0.031 g/cm 3 higher than the density of the first ethylene copolymer; the melt index, I 2 1 of the first ethylene copolymer is less than the melt index, I 2 2 of second ethylene copolymer; a ratio (SCB1/SCB2) of the number of short chain branches per thousand carbon atoms in the first ethylene copolymer (SCB1) to the number of short chain branches per thousand carbon atoms in the second ethylene copolymer (SCB2) is greater than 2.0; and wherein the polyethylene copolymer composition has a molecular weight distribution M w /M n , of from 1.8 to 7.0; a density of at least 0.949 g/cm 3 ; a high load melt index I 21 , of at least 200 g/10 min; a Z-average molecular weight M Z , of less than 200,000; a melt flow ratio I 21 /I 2 , of less than 40, wherein the I 21 and the I 2 are the melt index determined for the polyethylene copolymer composition using a 21.6 kg weight and a 2.16 kg weight, respectively; and a stress exponent of less than 1.40;
wherein the process comprises contacting at least one single site polymerization catalyst system with ethylen

Assignees

• Nova Chem Int Sa

Inventors

• Wang Xiaochuan
• Salomons Stephen

Classifications

• C08F4/65908

  in combination with an ionising compound other than alumoxane, e.g. (C6F5)4B-X+ · CPC title

• C08F4/65912

  in combination with an organoaluminium compound · CPC title

• C08F210/16

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

• C08L2205/025

  containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure · CPC title

• C08F2500/18

  Bulk density · CPC title