Polyethylene composition having high mechanical properties and processability

Patent metadata

Field	Value
Publication number	US-10577490-B2
Application number	US-201615739893-A
Country	US
Kind code	B2
Filing date	Jun 6, 2016
Priority date	Jun 26, 2015
Publication date	Mar 3, 2020
Grant date	Mar 3, 2020

Abstract

The polyethylene composition can be used to produce pipes and films.

First claim

What is claimed is:

1. A polyethylene composition comprising:
an ethylene polymer, wherein the ethylene polymer has a melt flow index (MIE) of 50 to 110 g/10 min., measured at 190° C. with a load of 2.16 kg, and wherein the polyethylene composition has:
1) a density from about 0.945 to about 0.955 g/cm 3 , determined according to ISO 1183 at 23° C.;
2) a ratio MIF/MIP from about 23 to about 40, 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) a MIF from about 8.5 to about 18 g/10 min.;
4) a HMWcopo index from about 3.5 to about 20; and
5) a long-chain branching index, LCBI, equal to or greater than about 0.45;
wherein the HMWcopo index is determined according to the following formula:
HMWcopo=(η 0.02 ×t maxDSC )/(10{circumflex over ( )}5)

where
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 about 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 catalyst and the catalyst was 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 solid catalyst component comprising a Ti compound supported on MgCl 2 , the solid catalyst component being obtained by
(i) contacting the titanium compound with the MgCl 2 , or a precursor Mg compound, optionally in the presence of an inert medium, thereby obtaining an intermediate product a′), and
(ii) subjecting a′) to prepolymerization and contact with an electron donor compound;

b) an organo-Al compound; and optionally
c) an external electron donor compound.

5. The polyethylene composition of claim 1 , wherein the polyethylene composition has at least one of the following features:
a z-average molecular weight Mz equal from about 800,000 to about 3,500,000 g/mol, measured by GPC-MALLS (Gel Permeation Chromatography coupled with Multi-angle laser-light scattering);
a M w_MALLS /M n_GPC values from about 8 to about 18; and
a comonomer content equal to or less than about 2.5% by weight, with respect to the total weight of the composition.

6. The polyethylene composition of claim 1 , wherein
A) about 30 to about 70% by weight of the polyethylene composition is the ethylene polymer being an ethylene homopolymer or copolymer with density equal to or greater than about 0.960 g/cm 3 ;
B) about 30 to about 70% by weight of the polyethylene composition is a second ethylene polymer being an ethylene copolymer having a MIE value lower than the MIE value of A).

7. An article of manufacture comprising:
a polyethylene composition comprising
an ethylene polymer, wherein the ethylene polymer has a melt flow index (MIE) of 50 to 110 g/10 min., measured at 190° C. with a load of 2.16 kg, and wherein the polyethylene composition has:
1) a density from about 0.945 to about 0.955 g/cm 3 , determined according to ISO 1183 at 23° C.;
2) a ratio MIF/MIP from about 23 to about 40, 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) a MIF from about 8.5 to about 18 g/10 min.;
4) a HMWcopo index from about 3.5 to about 20; and
5) a long-chain branching index, LCBI, equal to or greater than about 0.45;
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 about the molecular weight of the polyethylene composition.

8. The article of manufacture according to claim 7 , being selected from the group consisting of monolayer pipes, multilayer pipes, monolayer films, and multilayer films, wherein a layer comprises the polyethylene composition.

9. 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
an ethylene polymer, wherein the ethylene polymer has a melt flow index (MIE) of 50 to 110 g/10 min., measured at 190° C. with a load of 2.16 kg, and wherein the polyethylene composition has:
1) a density from about 0.945 to about 0.955 g/cm 3 , determined according to ISO 1183 at 23° C.;
2) a ratio MIF/MIP from about 23 to about 40, 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) a MIF from about 8.5 to about 18 g/10 min.;
4) a HMWcopo index from about 3.5 to about 20; and
5) a long-chain branching index, LCBI, equal to or greater than about 0.45;
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 about the molecular weight of the polyethylene composition.

10. The process for preparing a polyethylene composition of claim 9 , wherein the polymerization steps include the following steps, in any mutual order:
a) polymerizing ethylene, optionally together with one or more comonomers, in a first gas-phase reactor in the presence of a first amount of hydrogen;
b) copolymerizing ethylene with one or more comonomers in a second gas-phase reactor in the presence of a second amount of hydrogen less than the first amount of hydrogen in step a);

wherein in at least one of the gas-phase reactors, the growing polymer particles flow upward through a first polymerization zone under fast fluidization or transport conditions, leave the riser and enter a second polymerization zone through which

Assignees

• Basell Polyolefine Gmbh

Inventors

• Vittorias Iakovos
• Marczinke Bernd Lothar
• Meier Gerhardus
• Schüller Ulf
• Maus Andreas
• Mavridis Harilaos
• Dötsch Diana

Classifications

• F16L9/12

  of plastics with or without reinforcement (F16L9/16 - F16L9/22 take precedence) · CPC title

• B32B2597/00

  Tubular articles, e.g. hoses, pipes · CPC title

• B32B2307/72

  Density · CPC title

• C08L2308/00

  Chemical blending or stepwise polymerisation process with the same catalyst · 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