Polyethylene composition for films

Patent metadata

Field	Value
Publication number	US-10619035-B2
Application number	US-201615739652-A
Country	US
Kind code	B2
Filing date	Jun 6, 2016
Priority date	Jun 26, 2015
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

A polyethylene composition having the following features:
1) density from 0.945 to 0.958 g/cm 3 , determined according to ISO 1183 at 23° C.; 2) ratio MIF/MIP from 20 to 43; 3) MIF from 4.0 to less than 8.5 g/10 min.; 4) HMWcopo index from 3.5 to 20; and 5) long-chain branching index, LCBI, equal to or lower than 0.82. The polyethylene composition can be used to produce blown films.

First claim

What is claimed is:

1. A polyethylene composition comprising:
A) from 30 to 70% by weight of the polyethylene composition is an ethylene polymer, wherein the polymer is an ethylene homopolymer or a copolymer, and wherein the ethylene polymer has a density equal to or greater than 0.960 g/cm 3 , and a melt flow index MIE at 190° C. with a load of 2.16 kg, according to ISO 1133, greater than 35 g/10 min.;
B) from 30 to 70% by weight of the polyethylene composition is a second ethylene copolymer, wherein the second ethylene copolymer has a MIE value lower than the MIE value of A)
wherein the polyethylene composition has a molecular weight and
1) a density from 0.945 to 0.958 g/cm 3 , determined according to ISO 1183 at 23° C.;
2) an MIF/MIP ratio from 20 to 43, where MIF is the melt flow index at 190° C. with a load of 21.60 kg, and MIP is the melt flow index at 190° C. with a load of 5 kg, both determined according to ISO 1133;
3) an MIF from 4.0 to less than 8.5 g/10 min.;
4) an HMWcopo index from 3.5 to 20;
5) a long-chain branching index, LCBI, equal to or lower than 0.82;
wherein the HMWcopo index is determined according to the following formula:
HMWcopo=(η 0.02 ×t maxDSC )/(10{circumflex over ( )}5)

where
(i) η 0.02 is the complex viscosity of a melt in Pa·s, measured at a temperature of 190° C., in a parallel-plate rheometer under dynamic oscillatory shear mode with an applied angular frequency of 0.02 rad/s;
(ii) t maxDSC is the time in minutes to reach the maximum value of heat flow of crystallization at a temperature of 124° C. under quiescent conditions, measured in isothermal mode in a differential scanning calorimetry apparatus; and
(iii) LCBI is the ratio of the measured mean-square radius of gyration R g , measured by GPC-MALLS, to the mean-square radius of gyration for a linear PE having a molecular weight, equal to the molecular weight of the polyethylene composition.

2. The polyethylene composition of claim 1 , wherein the ethylene polymer is an ethylene copolymer.

3. The polyethylene composition of claim 1 , wherein the ethylene polymer was prepared in the presence of a Ziegler-Natta polymerization catalyst.

4. The polyethylene composition of claim 3 , wherein the Ziegler-Natta polymerization catalyst comprises a product of a reaction of:
a) a prepolymerized solid catalyst component comprising a Ti compound supported on MgCl 2 ;
b) an organo-Al compound; and optionally
c) an external electron donor compound.

5. The polyethylene composition of claim 1 , wherein the polyethylene composition comprises
A) from 40 to 60% by weight of the polyethylene composition is the ethylene polymer, wherein the ethylene polymer has a melt flow index MIE at 190° C. with a load of 2.16 kg, according to ISO 1133, from greater than 35 to 100 g/10 min.;
B) from 40 to 60% by weight of the polyethylene composition is the second ethylene copolymer, wherein the second ethylene copolymer has a melt flow index MIE at 190° C. with a load of 2.16 kg, according to ISO 1133, lower than 0.5 g/10 min.

6. The polyethylene composition of claim 1 , wherein the polyethylene composition has at least one of the following additional features:
a) a z-average molecular weight Mz equal to or greater than 1,200,000 g/mol, measured by GPC-MALLS;
b) an M w_MALLS /M n GPC value from 15 to 40; and
c) a comonomer content equal to or less than 2.5% by weight, with respect to the total weight of the composition (as determined by IR).

7. The polyolefin composition of claim 1 , wherein the long-chain branching index, LCBI, is 0.45 to 0.68.

8. An article of manufacture comprising:
(a) a polyethylene composition comprising:
A) from 30 to 70% by weight of the polyethylene composition is an ethylene polymer, wherein the polymer is an ethylene homopolymer or a copolymer, and wherein the ethylene polymer has a density equal to or greater than 0.960 g/cm 3 , and a melt flow index MIE at 190° C. with a load of 2.16 kg, according to ISO 1133, greater than 35 g/10 min.;
B) from 30 to 70% by weight of the polyethylene composition is a second ethylene copolymer, wherein the second ethylene copolymer has a MIE value lower than the MIE value of A)
wherein the polyethylene composition has a molecular weight and
a density from 0.945 to 0.958 g/cm 3 , determined according to ISO 1183 at 23° C.;
an MIF/MIP ratio from 20 to 43, where MIF is the melt flow index at 190° C. with a load of 21.60 kg, and MIP is the melt flow index at 190° C. with a load of 5 kg, both determined according to ISO 1133;
an MIF from 4.0 to less than 8.5 g/10 min.;
an HMWcopo index from 3.5 to 20;
a long-chain branching index, LCBI, equal to or lower than 0.82;
wherein the HMWcopo index is determined according to the following formula:
HMWcopo=(η 0.02 ×t maxDSC )/(10{circumflex over ( )}5)

where
(i) η 0.02 is the complex viscosity of a melt in Pa·s, measured at a temperature of 190° C., in a parallel-plate rheometer under dynamic oscillatory shear mode with an applied angular frequency of 0.02 rad/s;
(ii) t maxDSC is the time in minutes to reach the maximum value of heat flow of crystallization at a temperature of 124° C. under quiescent conditions, measured in isothermal mode in a differential scanning calorimetry apparatus; and
(iii) LCBI is the ratio of the measured mean-square radius of gyration R g , measured by GPC-MALLS, to the mean-square radius of gyration for a linear PE having a molecular weight, equal to the molecular weight of the polyethylene composition.

9. The article of manufacture according to claim 8 , being a mono- or multilayer blown film, wherein at least one layer comprises the polyethylene composition.

10. The article of manufacture of claim 8 , wherein the long-chain branching index, LCBI, is 0.45 to 0.68.

11. A process for preparing a polyethylene composition comprising:
polymerization steps carried out in the presence of a Ziegler-Natta polymerization catalyst supported on MgCl 2 , wherein the polyethylene composition comprises:
A) from 30 to 70% by weight of the polyethylene composition is an ethylene polymer, wherein the polymer is an ethylene homopolymer or a copolymer, and wherein the ethylene polymer has a density equal to or greater than 0.960 g/cm 3 , and a melt flow index MIE at 190° C. with a load of 2.16 kg, according to ISO 1133, greater than 35 g/10 min.;
B) from 30 to 70% by weight of the polyethylene composition is a second ethylene copolymer, wherein the second ethylene copolymer has a MIE value lower than the MIE value of A)
wherein the polyethylene composition has a molecular weight and
1) a density from 0.945 to 0.958 g/cm 3 , determined according to ISO 1183 at 23° C.;
2) an MIF/MIP ratio from 20 to 43, where MIF is the melt flow index at 190° C. with a load of 21.60 kg, and MIP is the melt flow index at 190° C. with a load of 5 kg, both determined according to ISO 1133;
3) an MIF from 4.0 to less than 8.5 g/10 min.;
4) an HMWcopo index from 3.5 to 20;
5) a long-chain branching index, LCBI, equal to or lower than 0.82;
wherein the HMWcopo index is determined according to the following formula:
HMWcopo=(η 0.02 ×t maxDSC )/(10{circumflex over ( )}5)

where
(i) η 0.02 is the complex viscosity of a melt in Pa·s, measured at a temperature of 190° C., in a parallel-plate rheometer under dynamic oscillatory shear mode with an applied angular frequency of 0.02 rad/s;
(ii) t maxDSC is the time in minutes to reach the maximum value of heat flow of crystallization at a temperature of 124° C. under quiescent conditions, measured in isothermal mode in a differential scanning calorimetry apparatus; and
(iii) LCBI is the ratio of the measured mea

Assignees

• Basell Polyolefine Gmbh

Inventors

• Vittorias Iakovos
• Meier Gerhardus
• Schüller Ulf
• Maus Andreas
• Wiesecke Jens
• Mavridis Harilaos

Classifications

• C08L2314/02

  Ziegler natta catalyst · CPC title

• B32B27/32

  comprising polyolefins {(comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30)} · CPC title

• C08J5/18

  Manufacture of films or sheets · 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

• C08L2308/00

  Chemical blending or stepwise polymerisation process with the same catalyst · CPC title