Polyethylene composition having high swell ratio

Patent metadata

Field	Value
Publication number	US-9580583-B2
Application number	US-201615215417-A
Country	US
Kind code	B2
Filing date	Jul 20, 2016
Priority date	Oct 22, 2012
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

The present disclosure relates to a polyethylene composition with improved swell ratio and mechanical properties for use in preparing blow-moulded articles and having the following features:
1) a density from 0.945 to less than 0.952 g/cm 3 ; 2) an MIF/MIP ratio from 15 to 30; 3) a Shear-Induced Crystallization Index (SIC) from 2.5 to 5.5.

First claim

What is claimed is:

1. A polyethylene composition comprising:
1) a density from 0.945 to less than 0.952 g/cm 3 , determined according to ISO 1183 at 23° C.;
2) a ratio MIF/MIP 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, 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 polyethylene composition of claim 1 , comprising one or more ethylene copolymers.

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

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

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

6. The polyethylene composition of claim 1 , having at least one of the following properties:
a Mw equal to or greater than 250,000 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 polyethylene composition 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 melt flow index MIE at 190° C. with a load of 2.16 kg, according to ISO 1133, of 10-35 g/10 min.;
B) 50-70% by weight of an ethylene copolymer having a MIE value lower than the MIE value of A).

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

9. The polyethylene composition of claim 8 , wherein the one or more polymerization 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);
where 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 they flow downward under the action of gravity, leave the second polymerization zone and are reintroduced into the first polymerization zone for establishing a circulation of polymers between the two polymerization zones.

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

• B29L2031/7172

  Fuel tanks, jerry cans · CPC title

• C08L2207/07

  Long chain branching · CPC title

• C08J5/00

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

• B29B15/00

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

• C08L23/06 Primary

  Polyethylene · CPC title