Polyethylene composition having high swell ratio

Patent metadata

Field	Value
Publication number	US-9428623-B2
Application number	US-201314437783-A
Country	US
Kind code	B2
Filing date	Oct 22, 2013
Priority date	Oct 22, 2012
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

Polyethylene composition with improved swell ratio and mechanical properties, particularly suited for preparing blow-molded articles, said composition having the following features:
1) density from 0.945 to less than 0.952 g/cm 3 ;
2) ratio MIF/MIP from 15 to 30;
3) Shear-Induced Crystallization Index SIC from 2.5 to 5.5.

First claim

What is claimed is:

1. A manufactured article comprising a polyethylene composition having the following properties:
1) a density from 0.945 to less than 0.952 g/cm 3 , determined according to ISO 1183 at 23° C.;
2) a MIF/MIP ratio from 15 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; and
3) a SIC Index from 2.5 to 5.5;
wherein the SIC Index is the Shear-Induced Crystallization Index as 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 crystallization onset under a shear rate of 1000 s −1 , the t onset, quiescent is measured in seconds and is the crystallization onset time at a temperature of 125° C. under no shear, as determined in isothermal mode by differential scanning calorimetry; and HLMI is the melt flow index determined at 190° C. with a load of 21.6 kg, according to ISO 1133.

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

3. The manufactured article of claim 2 , wherein the one or more ethylene copolymers have a comonomer content equal to or less than 1% by weight.

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

5. The polyethylene composition of claim 1 , obtained by using a Ziegler-Natta polymerization catalyst.

6. 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 Mw/Mn from 20 to 30;
a Long Chain Branching index equal to or greater than 0.70;
a MIP from 0.05-0.5 g/10 min; and
a MIF from 1-15 g/10 min.

7. The manufactured article of claim 1 , comprising:
A) 30-50% by weight of an ethylene homopolymer or copolymer with 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, of 10-35 g/10 min; and
B) 50-70% by weight of an ethylene copolymer having a MIE value lower than the MIE value of A).

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

9. The manufactured article of claim 1 , wherein the polyethylene composition is formed in one or more polymerizing steps, and wherein all of the polymerization steps are carried out in the presence of a Ziegler-Natta polymerization catalyst supported on MgCl 2 .

10. The manufactured article of claim 9 , wherein the one or more polymerizing steps comprise 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);
wherein 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 for establishing a circulation of polymer between said two polymerization zones.

11. The manufactured article of claim 8 , wherein the blow-molded article is selected from an open top drum (OTD), an industrial bulk article (IBC), a container and a gasoline storage tank.

Assignees

• Basell Polyolefine Gmbh

Inventors

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

Classifications

• C08L23/06

  Polyethylene · CPC title

• B29C48/92

  Measuring, controlling or regulating · CPC title

• B29B15/00

  Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00 · CPC title

• C08L2207/07

  Long chain branching · CPC title

• B29L2031/7154

  Barrels, drums, tuns, vats · CPC title