Polyethylene processes for producing compositions having high swell ratio

Patent metadata

Field	Value
Publication number	US-9738777-B2
Application number	US-201715408172-A
Country	US
Kind code	B2
Filing date	Jan 17, 2017
Priority date	Oct 22, 2012
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

The present disclosure relates to a polyethylene composition with improved swell ratio and mechanical properties for use in preparing blow-molded 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 polymerization process for preparing a polyethylene composition having the following features:
A) a density from 0.945 to less than 0.952 g/cm 3 determined according to ISO 1183 at 23° C.;
B) an MIF/MIP ratio from 15-30, 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;
C) an SIC Index from 2.5-5.5;
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 shear rate of 1000 s −1 , 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; and HLMI is the melt flow index determined at 190° C. with a load of 21.6 kg, according to ISO 1133;
wherein the polymerization process comprises the following steps, in any mutual order:

a) polymerizing ethylene 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 polymer between the two polymerization zones, and all polymerizations are performed in the presence of a Ziegler-Natta polymerization catalyst supported on MgCl 2 .

2. The polymerization process of claim 1 , wherein:
i) in said polymerization step a) 30-50% by weight of an ethylene homopolymer or copolymer A) with 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. is polymerized;
ii) in said polymerization step b) 50-70% by weight of an ethylene copolymer B) having a MIE value lower than the MIE value of A is polymerized.

3. The polymerization process of claim 1 , wherein the one or more ethylene copolymers has a comonomer content equal or less than 1% by weight.

4. The polymerization process of claim 1 , 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 polymerization process of claim 1 , wherein the polyethylene composition has at least one of the following additional features:
Mw equal to or greater than 250000 g/mol;
Mw/Mn from 20 to 30;
Long Chain Branching index equal to or greater than 0.70;
MIP: 0.05-0.5 g/10 min.;
MIF: 1-15 g/10 min.

6. The polymerization process of claim 1 , wherein the Ziegler-Natta polymerization catalyst comprises the product of reaction of:
a) a solid catalyst component comprising a Ti compound and an electron donor compound ED supported on MgCl 2 ;
b) an organo-Al compound; and optionally
c) an external electron donor compound ED ext .

7. The polymerization process of claim 5 , wherein the Ziegler-Natta polymerization catalyst comprises the product of reaction of:
a) a solid catalyst component comprising a Ti compound and an electron donor compound ED supported on MgCl 2 ;
b) an organo-Al compound; and optionally
c) an external electron donor compound ED ext .

8. The polymerization process of claim 1 further comprising manufacturing a blow-molded article.

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

10. The polymerization process of claim 1 , wherein the polyethylene composition comprises a density from 0.948-0.951 g/cm 3 .

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

• C08L23/0815 Primary

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

• C08F2/34

  Polymerisation in gaseous state · CPC title

• B29L2031/7172

  Fuel tanks, jerry cans · CPC title

• C08J2323/06

  Polyethene · CPC title