Polyethylene composition having high swell ratio

Patent metadata

Field	Value
Publication number	US-2016237265-A1
Application number	US-201615140022-A
Country	US
Kind code	A1
Filing date	Apr 27, 2016
Priority date	Oct 22, 2012
Publication date	Aug 18, 2016
Grant date	—

Abstract

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

First claim

What is claimed is:

1 . A polyethylene composition comprising:
1) a density from 0.952 to 0.960 g/cm 3 as determined according to ISO 1183 at 23° C.; 2) aMIF/MIP ratio from 17 to 30, wherein 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; and 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 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.

2 . The polyethylene composition of claim 1 , comprising one or more ethylene copolymers.

3 . The polyethylene composition of claim 2 , containing 1% by weight or less of comonomer.

4 . The polyethylene composition of claim 3 , wherein the comonomer or comonomers present in the ethylene copolymers are selected from olefins having 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 , obtainable by using a Ziegler-Natta polymerization catalyst.

6 . The polyethylene composition of claim 1 , having at least one of the following additional features:
a Mw equal to or greater than 250000 g/mol; a Long Chain Branching index equal to or greater than 0.70; a MIP of 0.05-0.5 g/10 min.; and a MIF of 1-15 g/10 min.

7 . The polyethylene composition 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 at 190° C. with a load of 2.16 kg, according to ISO 1133, of 2-30 g/10 min.; and B) 40-60% by weight of an ethylene copolymer having a MIE value lower than the MIE value of A).

8 . A manufactured article comprising the polyethylene composition of claim 1 .

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

10 . A process for preparing the polyethylene composition of claim 1 , wherein all of the polymerization steps are carried out in the presence of a Ziegler-Natta polymerization catalyst supported on MgCl 2 .

11 . The process of claim 10 , 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

Inventors

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

Classifications

• C08J5/00

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

• C08L23/0815 Primary

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

• C08J2423/06

  Polyethene · CPC title

• C08L2205/02

  containing two or more polymers of the same C08L -group · 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