Polyethylene composition having high swell ratio

Patent metadata

Field	Value
Publication number	US-9353206-B2
Application number	US-201314437456-A
Country	US
Kind code	B2
Filing date	Oct 22, 2013
Priority date	Oct 22, 2012
Publication date	May 31, 2016
Grant date	May 31, 2016

Abstract

Polyethylene composition with improved swell ratio and mechanical properties, particularly suited for preparing blow-moulded articles, said composition having the following features:
1) density from 0.952 to 0.960 g/cm 3 ; 2) ratio MIF/MIP from 17 to 30; 3) Shear-Induced Crystallization Index SIC from 2.5 to 5.0.

First claim

What is claimed is:

1. A manufactured article comprising a polyethylene composition having:
1) a density from 0.952 to 0.960 g/cm 3 , determined according to ISO 1183 at 23° C.;
2) a ratio MIF/MIP from 17 to 30 wherein the MIF is the melt flow index at 190° C. with a load of 21.60 kg, and the MIP is the melt flow index at 190° C. with a load of 5 kg, both determined according to ISO 1133;
3) a SIC Index from 2.5 to 5.0;
wherein the SIC Index is the Shear-Induced Crystallization Index, determined according to the following relation:
SIC Index=( t onset,SIC @1000× t onset,quiescent )/(HLMI*100)

where t onset,SIC @1000 is measured in seconds and is the time required for a crystallization onset under shear rate of 1000 s −1 , the t onset, quiescent is measured in seconds and is the crystallization onset time at temperature of 125° C. under no shear, determined in isothermal mode by differential scanning calorimetry; HLMI is the melt flow index determined at 190° C. with load of 21.6 kg, according to ISO 1133.

2. The manufactured article of claim 1 , comprising a blow-molded article.

3. The manufactured article of claim 1 , comprising one or more ethylene copolymers.

4. The manufactured article of claim 3 , containing 1% by weight or less of a comonomer.

5. The manufactured article of claim 4 , wherein the comonomer present in the ethylene copolymers is selected from olefins having the general formula CH 2 ═CHR, wherein R is an alkyl radical, linear or branched, having from 1 to 10 carbon atoms.

6. The manufactured article of claim 1 , obtained by using a Ziegler-Natta polymerization catalyst.

7. The manufactured article of claim 1 , having at least one of the following properties:
a Mw equal to or greater than 250000 g/mol;
a Long Chain Branching index equal to or greater than 0.70;
a MIP from 0.05 to 0.5 g/10 min.;
a MIF from 1 to 15 g/10 min.

8. The manufactured article of claim 1 , comprising:
A) 40-60% by weight of an ethylene homopolymer or copolymer with density equal to or greater than 0.960 g/cm 3 and melt flow index MIE 190° C.with a load of 2.16 kg, according to ISO 1133, of 2-30 g/10 min.;
B) 40-60% by weight of an ethylene copolymer having a MIE value lower than the MIE value of A).

9. A process for preparing a polyethylene composition having:
1) a density from 0.952 to 0.960 g/cm 3 , determined according to ISO 1183 at 23° C.;
2) a ratio MIF/MIP from 17 to 30 wherein the MIF is the melt flow index at 190° C. with a load of 21.60 kg, and the MIP is the melt flow index at 190° C. with a load of 5 kg, both determined according to ISO 1133;
3) a SIC Index from 2.5 to 5.0;
wherein the SIC Index is the Shear-Induced Crystallization Index, determined according to the following relation:
SIC Index=( t onset,SIC @1000× t onset,quiescent )/(HLMI*100)

where t onset,SIC @1000 is measured in seconds and is the time required for a crystallization onset under shear rate of 1000 s −1 , the t onset, quiescent is measured in seconds and is the crystallization onset time at temperature of 125° C. under no shear, determined in isothermal mode by differential scanning calorimetry; HLMI is the melt flow index determined at 190° C. with a load of 21.6 kg, according to ISO 1133; and
wherein all the polymerization steps are carried out in the presence of a Ziegler-Natta polymerization catalyst supported on MgCl 2 .

10. The process of claim 9 , comprising the following steps, in any mutual order:
a) polymerizing ethylene, optionally together with one or more comonomers, in a gas-phase reactor in the presence of hydrogen;
b) copolymerizing ethylene with one or more comonomers in another gas-phase reactor in the presence of an amount of hydrogen less than step a);
where in at least one of said gas-phase reactors the growing polymer particles flow upward through a first polymerization zone under fast fluidization or transport conditions, leave said riser and enter a second polymerization zone through which they flow downward under the action of gravity, leave said second polymerization zone and are reintroduced into the first polymerization zone, thus establishing a circulation of polymer between said two polymerization zones.

Assignees

• Basell Polyolefine Gmbh
• Bassel Polylefine GmbH

Inventors

• Vittorias Iakovos
• Wiesecke Jens
• Marczinke Bernd Lothar
• Meier Gerhardus
• Schüller Ulf
• Dolle Volker
• Enderle Johannes-Friedrich
• Lilge Dieter
• Gall Barbara

Classifications

• C08L23/0815 Primary

  with aliphatic 1-olefins containing one carbon-to-carbon double bond · CPC title

• C08L23/06 Primary

  Polyethylene · CPC title

• C08L2314/02

  Ziegler natta catalyst · CPC title

• C08J5/00

  Manufacture of articles or shaped materials containing macromolecular substances (manufacture of semi-permeable membranes B01D67/00 - B01D71/00) · 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